SEC Info  
    Home      Search      My Interests      Help      Sign In      Please Sign In

Unum Group – ‘10-K’ for 12/31/19 – ‘XML’

On:  Tuesday, 2/18/20, at 4:33pm ET   ·   For:  12/31/19   ·   Accession #:  5513-20-27   ·   File #:  1-11294

Previous ‘10-K’:  ‘10-K’ on 2/19/19 for 12/31/18   ·   Next:  ‘10-K’ on 2/17/21 for 12/31/20   ·   Latest:  ‘10-K’ on 2/20/24 for 12/31/23   ·   6 References:   

Find Words in Filings emoji
 
  in    Show  and   Hints

  As Of               Filer                 Filing    For·On·As Docs:Size

 2/18/20  Unum Group                        10-K       12/31/19  160:42M

Annual Report   —   Form 10-K   —   Sect. 13 / 15(d) – SEA’34
Filing Table of Contents

Document/Exhibit                   Description                      Pages   Size 

 1: 10-K        Annual Report                                       HTML   4.22M 
 2: EX-10.15    Material Contract                                   HTML     72K 
 3: EX-10.37    Material Contract                                   HTML     97K 
 4: EX-10.38    Material Contract                                   HTML     99K 
 5: EX-10.39    Material Contract                                   HTML     97K 
 6: EX-10.40    Material Contract                                   HTML    119K 
 7: EX-10.41    Material Contract                                   HTML    117K 
 8: EX-21       Subsidiaries List                                   HTML     46K 
 9: EX-23       Consent of Experts or Counsel                       HTML     45K 
10: EX-24       Power of Attorney                                   HTML     48K 
11: EX-31.1     Certification -- §302 - SOA'02                      HTML     47K 
12: EX-31.2     Certification -- §302 - SOA'02                      HTML     47K 
13: EX-32.1     Certification -- §906 - SOA'02                      HTML     43K 
14: EX-32.2     Certification -- §906 - SOA'02                      HTML     43K 
106: R1          Document and Entity Information                     HTML    106K  
54: R2          Consolidated Balance Sheets                         HTML    147K 
73: R3          Consolidated Balance Sheets (Parenthetical)         HTML     55K 
157: R4          Consolidated Statements of Income                   HTML    119K  
103: R5          Consolidated Statements of Comprehensive Income     HTML     69K  
51: R6          Statement of Comprehensive Income (Parenthetical)   HTML     56K 
72: R7          Consolidated Statements of Stockholders' Equity     HTML     80K 
155: R8          Consolidated Statements of Stockholders' Equity     HTML     42K  
                (Parenthetical)                                                  
107: R9          Consolidated Statements of Cash Flows               HTML    135K  
68: R10         Significant Accounting Policies                     HTML    224K 
49: R11         Fair Values of Financial Instruments                HTML    692K 
109: R12         Investments                                         HTML    584K  
159: R13         Derivative Financial Instruments                    HTML    364K  
69: R14         Accumulated Other Comprehensive Income              HTML    235K 
50: R15         Liability for Unpaid Claims and Claim Adjustment    HTML    115K 
                Expenses                                                         
110: R16         Income Tax                                          HTML    192K  
160: R17         Debt                                                HTML    126K  
70: R18         Employee Benefit Plans                              HTML    647K 
48: R19         Stockholders' Equity and Earnings Per Common Share  HTML     93K 
112: R20         Stock-Based Compensation                            HTML    125K  
126: R21         Reinsurance                                         HTML     62K  
75: R22         Segment Information                                 HTML    390K 
20: R23         Commitments and Contingent Liabilities              HTML     62K 
113: R24         Leases                                              HTML     68K  
127: R25         Statutory Financial Information                     HTML     78K  
76: R26         Unaudited Quarterly Results                         HTML    107K 
21: R27         Schedule I - Summary of Investments, Other Than     HTML     92K 
                Investments in Related Parties Schedule I -                      
                Summary of Investments, Other Than Investments in                
                Related Parties                                                  
111: R28         Schedule II Condensed Finacial Information of       HTML    269K  
                Registrant                                                       
129: R29         Schedule III Supplementary Insurance Information    HTML    222K  
158: R30         Schedule IV Reinsurance                             HTML    121K  
105: R31         Schedule V Valuation and Qualifying Accounts        HTML     98K  
53: R32         Signficant Accounting Policies (Policies)           HTML    229K 
74: R33         Significant Accounting Policies (Tables)            HTML    152K 
156: R34         Fair Values of Financial Instruments (Tables)       HTML    583K  
104: R35         Investments (Tables)                                HTML    643K  
52: R36         Derivative Financial Instruments (Tables)           HTML    359K 
71: R37         Accumulated Other Comprehensive Income (Tables)     HTML    239K 
154: R38         Liability for Unpaid Claims and Claim Adjustment    HTML    112K  
                Expenses (Tables)                                                
108: R39         Income Tax (Tables)                                 HTML    194K  
141: R40         Debt (Tables)                                       HTML    110K  
124: R41         Employee Benefit Plans (Tables)                     HTML    972K  
26: R42         Stockholders' Equity and Earnings Per Common Share  HTML     93K 
                (Tables)                                                         
79: R43         Stock-Based Compensation (Tables)                   HTML    129K 
140: R44         Reinsurance (Tables)                                HTML     61K  
121: R45         Segment Information (Tables)                        HTML    390K  
23: R46         Leases (Tables)                                     HTML     66K 
78: R47         Statutory Financial Information (Tables)            HTML     72K 
137: R48         Unaudited Quarterly Results (Tables)                HTML    107K  
125: R49         Schedule II Condensed Financial Information of      HTML    326K  
                Registrant (Tables)                                              
100: R50         Significant Accounting Policies Schedule of New     HTML     64K  
                Accounting Pronouncements (Details)                              
150: R51         Significant Accounting Policies - Additional        HTML     71K  
                Information (Detail)                                             
55: R52         Fair Values of Financial Instruments Private        HTML     70K 
                Equity Partnerships (Details)                                    
36: R53         Fair Value Measurements by Input Level (Detail)     HTML    174K 
101: R54         Changes in Assets and Liabilities Measured at Fair  HTML    123K  
                Value on a Recurring Basis using Significant                     
                Unobservable Inputs (Level 3) (Detail)                           
152: R55         Quantitative Information Regarding Significant      HTML     75K  
                Unobservable Inputs (Details)                                    
59: R56         Fair Values of Financial Instruments Carrying       HTML     92K 
                Amounts and Estimated Fair value of Financial                    
                Instruments Not Measured at Fair Value (Details)                 
37: R57         Fair Value of Financial Instruments Additional      HTML     61K 
                Information (Detail)                                             
98: R58         Amortized Cost and Fair Values of Securities by     HTML     80K 
                Security Type (Detail)                                           
153: R59         Length of Time Fixed Maturity Securities had been   HTML     78K  
                in a Gross Unrealized Loss Position (Detail)                     
83: R60         Investments Distribution of the Maturity Dates for  HTML    125K 
                Fixed Maturity Securities (Details)                              
29: R61         Investments Distribution by External Credit Rating  HTML     59K 
                for Fixed Maturity Securities (Details)                          
114: R62         Investments Low Income Housing Tax Credits          HTML     48K  
                (Details)                                                        
132: R63         Mortgage Loans by Property Type and Geographic      HTML     79K  
                Region (Detail)                                                  
86: R64         Mortgage Loans, Sorted by Applicable Credit         HTML     59K 
                Quality Indicators (Detail)                                      
34: R65         Investments Remaining Contractual Maturity of       HTML     53K 
                Security Lending Agreements (Details)                            
119: R66         Investments Federal Home Loan Bank Carrying         HTML     54K  
                Amount, Collateral Posted and Advances Received                  
                (Details)                                                        
135: R67         Investments Schedule of Financial Instrument and    HTML    167K  
                Derivative Offsetting (Details)                                  
88: R68         Investments Investment Income (Detail)              HTML     82K 
27: R69         Realized Investment Gains and Losses Reported in    HTML     71K 
                Consolidated Statements of Income (Detail)                       
43: R70         Investments - Additional Information (Detail)       HTML    152K 
67: R71         Derivative Financial Instruments Nature and Amount  HTML     52K 
                of Collateral Received From and Posted To Our                    
                Derivative Counterparties (Details)                              
148: R72         Notional Amounts for Each Category of Derivative    HTML     70K  
                Activity (Detail)                                                
96: R73         Derivative Financial Instruments Fair Value Hedges  HTML     59K 
                Carrying Amount of Hedged Assets and Liabilities                 
                and Cumulative Basis Adjustments (Details)                       
40: R74         Location and Fair Values of Derivative Financial    HTML     80K 
                Instruments (Detail)                                             
62: R75         Derivative Financial Instruments Location of Gains  HTML     97K 
                and Losses Designated as Hedging Instruments,                    
                Consolidated Statements of Income (Details)                      
143: R76         Location of Gains and Losses on Derivative          HTML     52K  
                Instruments Designated as Cash Flow Hedging                      
                Instruments (Detail)                                             
93: R77         Gains and Losses on Derivatives Not Designated as   HTML     55K 
                Hedging Instruments (Detail)                                     
46: R78         Derivative Financial Instruments - Additional       HTML    104K 
                Information (Detail)                                             
61: R79         Schedule of Accumulated Other Comprehensive Income  HTML     83K 
                (Details)                                                        
42: R80         Schedule of Components of Unrealized Gain (Loss)    HTML     76K 
                on Securities (Details)                                          
65: R81         Schedule of Reclassifications Out of Accumulated    HTML    107K 
                Other Comprehensive Income (Details)                             
146: R82         Liability for Unpaid Claims and Claims Adjustment   HTML     80K  
                Expense (Detail)                                                 
95: R83         Reconciliation of Policy and Contract Benefits and  HTML     60K 
                Reserves for Future Policy and Contract Benefits                 
                (Detail)                                                         
41: R84         Liability for Unpaid Claims - Additional            HTML     61K 
                Information (Detail)                                             
64: R85         Income Tax Expense (Benefit) (Detail)               HTML     63K 
145: R86         Reconciliation of income tax computed at US         HTML     65K  
                Federal tax rates (Detail)                                       
94: R87         Schedule of deferred income tax assets and          HTML     82K 
                liabilities (Detail)                                             
45: R88         Schedule of Income subject to domestic and foreign  HTML     85K 
                taxation (Detail)                                                
60: R89         Unrecognized tax benefits (Detail)                  HTML     59K 
84: R90         Income Tax Additional Information (Detail)          HTML     74K 
31: R91         Debt Schedule (Detail)                              HTML     97K 
116: R92         Debt - Additional Information (Details)             HTML    172K  
133: R93         Employee Benefit Plans Change in Projected Benefit  HTML    115K  
                Obligation Amount (Details)                                      
85: R94         Employee Benefit Plans Amounts Recognized in        HTML     86K 
                Balance Sheet (Details)                                          
32: R95         Employee Benefit Plans Amounts Recognized in Other  HTML     74K 
                Comprehensive Income (Details)                                   
117: R96         Employee Benefit Plans US Pension Assets, Fair      HTML    149K  
                Value Measurement by Input Level (Details)                       
134: R97         Employee Benefit Plans UK Pension Assets, Fair      HTML     82K  
                Value Measurement by Input Level (Details)                       
89: R98         Employee Benefit Plans OPEB Plan Assets, Fair       HTML     52K 
                Value Measurements by Input Level (Details)                      
28: R99         Employee Benefit Plans OPEB Changes in Assets       HTML     57K 
                Measured at Fair Value Using Signficant                          
                Unobservable Inputs (Details)                                    
115: R100        Employee Benefit Plans Measurement Assumptions      HTML     63K  
                (Details)                                                        
131: R101        Employee Benefit Plans Net Periodic Benefit Cost    HTML     71K  
                (Detail)                                                         
82: R102        Employee Benefit Plans Expected Benefit Payments    HTML     95K 
                (Details)                                                        
30: R103        Employee Benefit Plans - Additional Information     HTML    133K 
                (Detail)                                                         
118: R104        Basic and Diluted Earnings Per Share (Detail)       HTML     74K  
136: R105        Treasury Stock Transactions (Details)               HTML     67K  
87: R106        Stockholders' Equity and Earnings Per Common Share  HTML     52K 
                - Additional Information (Detail)                                
33: R107        Stock-Based Compensation - Activity for PSUs        HTML     66K 
                Classified as Equity (Details)                                   
120: R108        Stock-Based Compensation - Valuation Assumptions    HTML     51K  
                on PSU Grants (Details)                                          
130: R109        Stock-Based Compensation - Nonvested Stock Awards   HTML     66K  
                Classified in Equity (Details)                                   
147: R110        Stock option activity (Details)                     HTML     71K  
97: R111        Intrinsic Value of Options Exercised and Fair       HTML     47K 
                Value of Options Vested (Details)                                
44: R112        Stock-Based Compensation Expense (Details)          HTML     54K 
66: R113        Stock-Based Compensation - Additional Information   HTML    105K 
                (Details)                                                        
144: R114        Reinsurance - Premium Income Data (Detail)          HTML     62K  
92: R115        Reinsurance - Additional Information (Detail)       HTML     54K 
39: R116        Premium Income by Major Line of Business within     HTML    115K 
                Each Segment (Detail)                                            
63: R117        Selected Operating Statement Data by Segment        HTML    102K 
                (Detail)                                                         
149: R118        Segment Information Deferred Acquisition Costs by   HTML     74K  
                Segment (Details)                                                
90: R119        Assets by Segment (Detail)                          HTML     56K 
25: R120        Reconciliation of Total Revenue and Income Before   HTML     78K 
                Income Tax to Operating Revenue and Operating                    
                Income (Detail)                                                  
80: R121        Segment Information Segments - Additional           HTML     77K 
                Information (Detail)                                             
142: R122        Leases, Cost (Details)                              HTML     60K  
123: R123        Lessee, Operating Lease, Liability, Payment, Due    HTML     60K  
                (Details)                                                        
24: R124        Leases - Additional Information (Details)           HTML     56K 
77: R125        Statutory Financial Information (Detail)            HTML     53K 
139: R126        Statutory Financial Information - Additional        HTML     63K  
                Details (Detail)                                                 
122: R127        Schedule of Unaudited Quarterly Results (Detail)    HTML     79K  
22: R128        Schedule I - Summary of Investments, Other Than     HTML     90K 
                Investments in Related Parties Schedule I -                      
                Summary of Investments, Other Than Investments in                
                Related Parties (Details)                                        
81: R129        Parent Company Balance Sheet (Detail)               HTML    115K 
56: R130        Parent Company Statement of Income (Detail)         HTML    101K 
35: R131        Parent Company Cash Flow Statement (Detail)         HTML    106K 
99: R132        Parent Company Debt Schedule (Detail)               HTML    107K 
151: R133        Parent Company Notes - Additional Details           HTML    137K  
                (Details)                                                        
57: R134        Schedule III Supplementary Insurance Information    HTML     98K 
                (Detail)                                                         
38: R135        Schedule IV Reinsurance (Detail)                    HTML     88K 
102: R136        Schedule V Valuation and Qualifying Accounts        HTML     58K  
                (Detail)                                                         
47: XML         IDEA XML File -- Filing Summary                      XML    292K 
91: XML         XBRL Instance -- unm-20191231_htm                    XML  13.78M 
128: EXCEL       IDEA Workbook of Financial Reports                  XLSX    250K  
16: EX-101.CAL  XBRL Calculations -- unm-20191231_cal                XML    392K 
17: EX-101.DEF  XBRL Definitions -- unm-20191231_def                 XML   2.32M 
18: EX-101.LAB  XBRL Labels -- unm-20191231_lab                      XML   4.00M 
19: EX-101.PRE  XBRL Presentations -- unm-20191231_pre               XML   2.85M 
15: EX-101.SCH  XBRL Schema -- unm-20191231                          XSD    395K 
58: JSON        XBRL Instance as JSON Data -- MetaLinks              783±  1.24M 
138: ZIP         XBRL Zipped Folder -- 0000005513-20-000027-xbrl      Zip   1.13M  


‘XML’   —   IDEA XML File — Filing Summary


This Document is an IDEA XML File.


                                                                                                                                                                                
<?xml version="1.0" encoding="windows-1252"?>
<FilingSummary>
<Version> 3.19.3.a.u2 </Version>
<ProcessingTime/>
<ReportFormat> html </ReportFormat>
<ContextCount> 1219 </ContextCount>
<ElementCount> 793 </ElementCount>
<EntityCount> 1 </EntityCount>
<FootnotesReported> true </FootnotesReported>
<SegmentCount> 269 </SegmentCount>
<ScenarioCount> 0 </ScenarioCount>
<TuplesReported> false </TuplesReported>
<UnitCount> 7 </UnitCount>
<MyReports>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R1.htm </HtmlFileName>
<LongName> 000010001 - Document - Document and Entity Information </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/DocumentandEntityInformation </Role>
<ShortName> Document and Entity Information </ShortName>
<MenuCategory> Cover </MenuCategory>
<Position> 1 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R2.htm </HtmlFileName>
<LongName> 100010002 - Statement - CONSOLIDATED BALANCE SHEETS </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/CONSOLIDATEDBALANCESHEETS </Role>
<ShortName> CONSOLIDATED BALANCE SHEETS </ShortName>
<MenuCategory> Statements </MenuCategory>
<Position> 2 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R3.htm </HtmlFileName>
<LongName> 100020003 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/CONSOLIDATEDBALANCESHEETSParenthetical </Role>
<ShortName> CONSOLIDATED BALANCE SHEETS (Parenthetical) </ShortName>
<MenuCategory> Statements </MenuCategory>
<Position> 3 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R4.htm </HtmlFileName>
<LongName> 100030004 - Statement - CONSOLIDATED STATEMENTS OF INCOME </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/CONSOLIDATEDSTATEMENTSOFINCOME </Role>
<ShortName> CONSOLIDATED STATEMENTS OF INCOME </ShortName>
<MenuCategory> Statements </MenuCategory>
<Position> 4 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R5.htm </HtmlFileName>
<LongName> 100040005 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOME </Role>
<ShortName> CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME </ShortName>
<MenuCategory> Statements </MenuCategory>
<Position> 5 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R6.htm </HtmlFileName>
<LongName> 100050006 - Statement - STATEMENT OF COMPREHENSIVE INCOME (Parenthetical) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/STATEMENTOFCOMPREHENSIVEINCOMEParenthetical </Role>
<ShortName> STATEMENT OF COMPREHENSIVE INCOME (Parenthetical) </ShortName>
<MenuCategory> Statements </MenuCategory>
<Position> 6 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R7.htm </HtmlFileName>
<LongName> 100060007 - Statement - CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/CONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY </Role>
<ShortName> CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY </ShortName>
<MenuCategory> Statements </MenuCategory>
<Position> 7 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R8.htm </HtmlFileName>
<LongName> 100070008 - Statement - CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/CONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITYParenthetical </Role>
<ShortName> CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) </ShortName>
<MenuCategory> Statements </MenuCategory>
<Position> 8 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R9.htm </HtmlFileName>
<LongName> 100080009 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/CONSOLIDATEDSTATEMENTSOFCASHFLOWS </Role>
<ShortName> CONSOLIDATED STATEMENTS OF CASH FLOWS </ShortName>
<MenuCategory> Statements </MenuCategory>
<Position> 9 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R10.htm </HtmlFileName>
<LongName> 210011001 - Disclosure - Significant Accounting Policies </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/SignificantAccountingPolicies </Role>
<ShortName> Significant Accounting Policies </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 10 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R11.htm </HtmlFileName>
<LongName> 210061002 - Disclosure - Fair Values of Financial Instruments </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/FairValuesofFinancialInstruments </Role>
<ShortName> Fair Values of Financial Instruments </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 11 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R12.htm </HtmlFileName>
<LongName> 210141003 - Disclosure - Investments </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/Investments </Role>
<ShortName> Investments </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 12 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R13.htm </HtmlFileName>
<LongName> 210291004 - Disclosure - Derivative Financial Instruments </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/DerivativeFinancialInstruments </Role>
<ShortName> Derivative Financial Instruments </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 13 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R14.htm </HtmlFileName>
<LongName> 210391005 - Disclosure - Accumulated Other Comprehensive Income </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/AccumulatedOtherComprehensiveIncome </Role>
<ShortName> Accumulated Other Comprehensive Income </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 14 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R15.htm </HtmlFileName>
<LongName> 210441006 - Disclosure - Liability for Unpaid Claims and Claim Adjustment Expenses </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/LiabilityforUnpaidClaimsandClaimAdjustmentExpenses </Role>
<ShortName> Liability for Unpaid Claims and Claim Adjustment Expenses </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 15 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R16.htm </HtmlFileName>
<LongName> 210491007 - Disclosure - Income Tax </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/IncomeTax </Role>
<ShortName> Income Tax </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 16 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R17.htm </HtmlFileName>
<LongName> 210571008 - Disclosure - Debt </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/Debt </Role>
<ShortName> Debt </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 17 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R18.htm </HtmlFileName>
<LongName> 210611009 - Disclosure - Employee Benefit Plans </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/EmployeeBenefitPlans </Role>
<ShortName> Employee Benefit Plans </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 18 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R19.htm </HtmlFileName>
<LongName> 210741010 - Disclosure - Stockholders' Equity and Earnings Per Common Share </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/StockholdersEquityandEarningsPerCommonShare </Role>
<ShortName> Stockholders' Equity and Earnings Per Common Share </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 19 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R20.htm </HtmlFileName>
<LongName> 210791011 - Disclosure - Stock-Based Compensation </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/StockBasedCompensation </Role>
<ShortName> Stock-Based Compensation </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 20 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R21.htm </HtmlFileName>
<LongName> 210881012 - Disclosure - Reinsurance </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/Reinsurance </Role>
<ShortName> Reinsurance </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 21 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R22.htm </HtmlFileName>
<LongName> 210921013 - Disclosure - Segment Information </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/SegmentInformation </Role>
<ShortName> Segment Information </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 22 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R23.htm </HtmlFileName>
<LongName> 211001014 - Disclosure - Commitments and Contingent Liabilities </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/CommitmentsandContingentLiabilities </Role>
<ShortName> Commitments and Contingent Liabilities </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 23 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R24.htm </HtmlFileName>
<LongName> 211011015 - Disclosure - Leases </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/Leases </Role>
<ShortName> Leases </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 24 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R25.htm </HtmlFileName>
<LongName> 211061016 - Disclosure - Statutory Financial Information </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/StatutoryFinancialInformation </Role>
<ShortName> Statutory Financial Information </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 25 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R26.htm </HtmlFileName>
<LongName> 211101017 - Disclosure - Unaudited Quarterly Results </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/UnauditedQuarterlyResults </Role>
<ShortName> Unaudited Quarterly Results </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 26 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R27.htm </HtmlFileName>
<LongName> 211131018 - Disclosure - Schedule I - Summary of Investments, Other Than Investments in Related Parties Schedule I - Summary of Investments, Other Than Investments in Related Parties </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ScheduleISummaryofInvestmentsOtherThanInvestmentsinRelatedPartiesScheduleISummaryofInvestmentsOtherThanInvestmentsinRelatedParties </Role>
<ShortName> Schedule I - Summary of Investments, Other Than Investments in Related Parties Schedule I - Summary of Investments, Other Than Investments in Related Parties </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 27 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R28.htm </HtmlFileName>
<LongName> 211151019 - Disclosure - Schedule II Condensed Finacial Information of Registrant </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ScheduleIICondensedFinacialInformationofRegistrant </Role>
<ShortName> Schedule II Condensed Finacial Information of Registrant </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 28 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R29.htm </HtmlFileName>
<LongName> 211221020 - Disclosure - Schedule III Supplementary Insurance Information </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ScheduleIIISupplementaryInsuranceInformation </Role>
<ShortName> Schedule III Supplementary Insurance Information </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 29 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R30.htm </HtmlFileName>
<LongName> 211241021 - Disclosure - Schedule IV Reinsurance </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ScheduleIVReinsurance </Role>
<ShortName> Schedule IV Reinsurance </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 30 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R31.htm </HtmlFileName>
<LongName> 211261022 - Disclosure - Schedule V Valuation and Qualifying Accounts </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ScheduleVValuationandQualifyingAccounts </Role>
<ShortName> Schedule V Valuation and Qualifying Accounts </ShortName>
<MenuCategory> Notes </MenuCategory>
<Position> 31 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R32.htm </HtmlFileName>
<LongName> 220022001 - Disclosure - Signficant Accounting Policies (Policies) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/SignficantAccountingPoliciesPolicies </Role>
<ShortName> Signficant Accounting Policies (Policies) </ShortName>
<MenuCategory> Policies </MenuCategory>
<ParentRole> http://www.unum.com/role/SignificantAccountingPolicies </ParentRole>
<Position> 32 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R33.htm </HtmlFileName>
<LongName> 230033001 - Disclosure - Significant Accounting Policies (Tables) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/SignificantAccountingPoliciesTables </Role>
<ShortName> Significant Accounting Policies (Tables) </ShortName>
<MenuCategory> Tables </MenuCategory>
<ParentRole> http://www.unum.com/role/SignificantAccountingPolicies </ParentRole>
<Position> 33 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R34.htm </HtmlFileName>
<LongName> 230073002 - Disclosure - Fair Values of Financial Instruments (Tables) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/FairValuesofFinancialInstrumentsTables </Role>
<ShortName> Fair Values of Financial Instruments (Tables) </ShortName>
<MenuCategory> Tables </MenuCategory>
<ParentRole> http://www.unum.com/role/FairValuesofFinancialInstruments </ParentRole>
<Position> 34 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R35.htm </HtmlFileName>
<LongName> 230153003 - Disclosure - Investments (Tables) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/InvestmentsTables </Role>
<ShortName> Investments (Tables) </ShortName>
<MenuCategory> Tables </MenuCategory>
<ParentRole> http://www.unum.com/role/Investments </ParentRole>
<Position> 35 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R36.htm </HtmlFileName>
<LongName> 230303004 - Disclosure - Derivative Financial Instruments (Tables) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/DerivativeFinancialInstrumentsTables </Role>
<ShortName> Derivative Financial Instruments (Tables) </ShortName>
<MenuCategory> Tables </MenuCategory>
<ParentRole> http://www.unum.com/role/DerivativeFinancialInstruments </ParentRole>
<Position> 36 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R37.htm </HtmlFileName>
<LongName> 230403005 - Disclosure - Accumulated Other Comprehensive Income (Tables) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/AccumulatedOtherComprehensiveIncomeTables </Role>
<ShortName> Accumulated Other Comprehensive Income (Tables) </ShortName>
<MenuCategory> Tables </MenuCategory>
<ParentRole> http://www.unum.com/role/AccumulatedOtherComprehensiveIncome </ParentRole>
<Position> 37 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R38.htm </HtmlFileName>
<LongName> 230453006 - Disclosure - Liability for Unpaid Claims and Claim Adjustment Expenses (Tables) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/LiabilityforUnpaidClaimsandClaimAdjustmentExpensesTables </Role>
<ShortName> Liability for Unpaid Claims and Claim Adjustment Expenses (Tables) </ShortName>
<MenuCategory> Tables </MenuCategory>
<ParentRole> http://www.unum.com/role/LiabilityforUnpaidClaimsandClaimAdjustmentExpenses </ParentRole>
<Position> 38 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R39.htm </HtmlFileName>
<LongName> 230503007 - Disclosure - Income Tax (Tables) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/IncomeTaxTables </Role>
<ShortName> Income Tax (Tables) </ShortName>
<MenuCategory> Tables </MenuCategory>
<ParentRole> http://www.unum.com/role/IncomeTax </ParentRole>
<Position> 39 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R40.htm </HtmlFileName>
<LongName> 230583008 - Disclosure - Debt (Tables) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/DebtTables </Role>
<ShortName> Debt (Tables) </ShortName>
<MenuCategory> Tables </MenuCategory>
<ParentRole> http://www.unum.com/role/Debt </ParentRole>
<Position> 40 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R41.htm </HtmlFileName>
<LongName> 230623009 - Disclosure - Employee Benefit Plans (Tables) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/EmployeeBenefitPlansTables </Role>
<ShortName> Employee Benefit Plans (Tables) </ShortName>
<MenuCategory> Tables </MenuCategory>
<ParentRole> http://www.unum.com/role/EmployeeBenefitPlans </ParentRole>
<Position> 41 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R42.htm </HtmlFileName>
<LongName> 230753010 - Disclosure - Stockholders' Equity and Earnings Per Common Share (Tables) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/StockholdersEquityandEarningsPerCommonShareTables </Role>
<ShortName> Stockholders' Equity and Earnings Per Common Share (Tables) </ShortName>
<MenuCategory> Tables </MenuCategory>
<ParentRole> http://www.unum.com/role/StockholdersEquityandEarningsPerCommonShare </ParentRole>
<Position> 42 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R43.htm </HtmlFileName>
<LongName> 230803011 - Disclosure - Stock-Based Compensation (Tables) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/StockBasedCompensationTables </Role>
<ShortName> Stock-Based Compensation (Tables) </ShortName>
<MenuCategory> Tables </MenuCategory>
<ParentRole> http://www.unum.com/role/StockBasedCompensation </ParentRole>
<Position> 43 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R44.htm </HtmlFileName>
<LongName> 230893012 - Disclosure - Reinsurance (Tables) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ReinsuranceTables </Role>
<ShortName> Reinsurance (Tables) </ShortName>
<MenuCategory> Tables </MenuCategory>
<ParentRole> http://www.unum.com/role/Reinsurance </ParentRole>
<Position> 44 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R45.htm </HtmlFileName>
<LongName> 230933013 - Disclosure - Segment Information (Tables) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/SegmentInformationTables </Role>
<ShortName> Segment Information (Tables) </ShortName>
<MenuCategory> Tables </MenuCategory>
<ParentRole> http://www.unum.com/role/SegmentInformation </ParentRole>
<Position> 45 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R46.htm </HtmlFileName>
<LongName> 231023014 - Disclosure - Leases (Tables) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/LeasesTables </Role>
<ShortName> Leases (Tables) </ShortName>
<MenuCategory> Tables </MenuCategory>
<ParentRole> http://www.unum.com/role/Leases </ParentRole>
<Position> 46 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R47.htm </HtmlFileName>
<LongName> 231073015 - Disclosure - Statutory Financial Information (Tables) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/StatutoryFinancialInformationTables </Role>
<ShortName> Statutory Financial Information (Tables) </ShortName>
<MenuCategory> Tables </MenuCategory>
<ParentRole> http://www.unum.com/role/StatutoryFinancialInformation </ParentRole>
<Position> 47 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R48.htm </HtmlFileName>
<LongName> 231113016 - Disclosure - Unaudited Quarterly Results (Tables) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/UnauditedQuarterlyResultsTables </Role>
<ShortName> Unaudited Quarterly Results (Tables) </ShortName>
<MenuCategory> Tables </MenuCategory>
<ParentRole> http://www.unum.com/role/UnauditedQuarterlyResults </ParentRole>
<Position> 48 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R49.htm </HtmlFileName>
<LongName> 231163017 - Disclosure - Schedule II Condensed Financial Information of Registrant (Tables) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ScheduleIICondensedFinancialInformationofRegistrantTables </Role>
<ShortName> Schedule II Condensed Financial Information of Registrant (Tables) </ShortName>
<MenuCategory> Tables </MenuCategory>
<Position> 49 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R50.htm </HtmlFileName>
<LongName> 240044001 - Disclosure - Significant Accounting Policies Schedule of New Accounting Pronouncements (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/SignificantAccountingPoliciesScheduleofNewAccountingPronouncementsDetails </Role>
<ShortName> Significant Accounting Policies Schedule of New Accounting Pronouncements (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 50 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R51.htm </HtmlFileName>
<LongName> 240054002 - Disclosure - Significant Accounting Policies - Additional Information (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/SignificantAccountingPoliciesAdditionalInformationDetail </Role>
<ShortName> Significant Accounting Policies - Additional Information (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 51 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R52.htm </HtmlFileName>
<LongName> 240084003 - Disclosure - Fair Values of Financial Instruments Private Equity Partnerships (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/FairValuesofFinancialInstrumentsPrivateEquityPartnershipsDetails </Role>
<ShortName> Fair Values of Financial Instruments Private Equity Partnerships (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 52 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R53.htm </HtmlFileName>
<LongName> 240094004 - Disclosure - Fair Value Measurements by Input Level (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/FairValueMeasurementsbyInputLevelDetail </Role>
<ShortName> Fair Value Measurements by Input Level (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 53 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R54.htm </HtmlFileName>
<LongName> 240104005 - Disclosure - Changes in Assets and Liabilities Measured at Fair Value on a Recurring Basis using Significant Unobservable Inputs (Level 3) (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ChangesinAssetsandLiabilitiesMeasuredatFairValueonaRecurringBasisusingSignificantUnobservableInputsLevel3Detail </Role>
<ShortName> Changes in Assets and Liabilities Measured at Fair Value on a Recurring Basis using Significant Unobservable Inputs (Level 3) (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 54 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R55.htm </HtmlFileName>
<LongName> 240114006 - Disclosure - Quantitative Information Regarding Significant Unobservable Inputs (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/QuantitativeInformationRegardingSignificantUnobservableInputsDetails </Role>
<ShortName> Quantitative Information Regarding Significant Unobservable Inputs (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 55 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R56.htm </HtmlFileName>
<LongName> 240124007 - Disclosure - Fair Values of Financial Instruments Carrying Amounts and Estimated Fair value of Financial Instruments Not Measured at Fair Value (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/FairValuesofFinancialInstrumentsCarryingAmountsandEstimatedFairvalueofFinancialInstrumentsNotMeasuredatFairValueDetails </Role>
<ShortName> Fair Values of Financial Instruments Carrying Amounts and Estimated Fair value of Financial Instruments Not Measured at Fair Value (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 56 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R57.htm </HtmlFileName>
<LongName> 240134008 - Disclosure - Fair Value of Financial Instruments Additional Information (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/FairValueofFinancialInstrumentsAdditionalInformationDetail </Role>
<ShortName> Fair Value of Financial Instruments Additional Information (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 57 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R58.htm </HtmlFileName>
<LongName> 240164009 - Disclosure - Amortized Cost and Fair Values of Securities by Security Type (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/AmortizedCostandFairValuesofSecuritiesbySecurityTypeDetail </Role>
<ShortName> Amortized Cost and Fair Values of Securities by Security Type (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 58 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R59.htm </HtmlFileName>
<LongName> 240174010 - Disclosure - Length of Time Fixed Maturity Securities had been in a Gross Unrealized Loss Position (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/LengthofTimeFixedMaturitySecuritieshadbeeninaGrossUnrealizedLossPositionDetail </Role>
<ShortName> Length of Time Fixed Maturity Securities had been in a Gross Unrealized Loss Position (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 59 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R60.htm </HtmlFileName>
<LongName> 240184011 - Disclosure - Investments Distribution of the Maturity Dates for Fixed Maturity Securities (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/InvestmentsDistributionoftheMaturityDatesforFixedMaturitySecuritiesDetails </Role>
<ShortName> Investments Distribution of the Maturity Dates for Fixed Maturity Securities (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 60 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R61.htm </HtmlFileName>
<LongName> 240194012 - Disclosure - Investments Distribution by External Credit Rating for Fixed Maturity Securities (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/InvestmentsDistributionbyExternalCreditRatingforFixedMaturitySecuritiesDetails </Role>
<ShortName> Investments Distribution by External Credit Rating for Fixed Maturity Securities (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 61 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R62.htm </HtmlFileName>
<LongName> 240204013 - Disclosure - Investments Low Income Housing Tax Credits (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/InvestmentsLowIncomeHousingTaxCreditsDetails </Role>
<ShortName> Investments Low Income Housing Tax Credits (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 62 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R63.htm </HtmlFileName>
<LongName> 240214014 - Disclosure - Mortgage Loans by Property Type and Geographic Region (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/MortgageLoansbyPropertyTypeandGeographicRegionDetail </Role>
<ShortName> Mortgage Loans by Property Type and Geographic Region (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 63 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R64.htm </HtmlFileName>
<LongName> 240224015 - Disclosure - Mortgage Loans, Sorted by Applicable Credit Quality Indicators (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/MortgageLoansSortedbyApplicableCreditQualityIndicatorsDetail </Role>
<ShortName> Mortgage Loans, Sorted by Applicable Credit Quality Indicators (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 64 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R65.htm </HtmlFileName>
<LongName> 240234016 - Disclosure - Investments Remaining Contractual Maturity of Security Lending Agreements (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/InvestmentsRemainingContractualMaturityofSecurityLendingAgreementsDetails </Role>
<ShortName> Investments Remaining Contractual Maturity of Security Lending Agreements (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 65 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R66.htm </HtmlFileName>
<LongName> 240244017 - Disclosure - Investments Federal Home Loan Bank Carrying Amount, Collateral Posted and Advances Received (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/InvestmentsFederalHomeLoanBankCarryingAmountCollateralPostedandAdvancesReceivedDetails </Role>
<ShortName> Investments Federal Home Loan Bank Carrying Amount, Collateral Posted and Advances Received (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 66 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R67.htm </HtmlFileName>
<LongName> 240254018 - Disclosure - Investments Schedule of Financial Instrument and Derivative Offsetting (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/InvestmentsScheduleofFinancialInstrumentandDerivativeOffsettingDetails </Role>
<ShortName> Investments Schedule of Financial Instrument and Derivative Offsetting (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 67 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R68.htm </HtmlFileName>
<LongName> 240264019 - Disclosure - Investments Investment Income (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/InvestmentsInvestmentIncomeDetail </Role>
<ShortName> Investments Investment Income (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 68 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R69.htm </HtmlFileName>
<LongName> 240274020 - Disclosure - Realized Investment Gains and Losses Reported in Consolidated Statements of Income (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/RealizedInvestmentGainsandLossesReportedinConsolidatedStatementsofIncomeDetail </Role>
<ShortName> Realized Investment Gains and Losses Reported in Consolidated Statements of Income (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 69 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R70.htm </HtmlFileName>
<LongName> 240284021 - Disclosure - Investments - Additional Information (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/InvestmentsAdditionalInformationDetail </Role>
<ShortName> Investments - Additional Information (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 70 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R71.htm </HtmlFileName>
<LongName> 240314022 - Disclosure - Derivative Financial Instruments Nature and Amount of Collateral Received From and Posted To Our Derivative Counterparties (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/DerivativeFinancialInstrumentsNatureandAmountofCollateralReceivedFromandPostedToOurDerivativeCounterpartiesDetails </Role>
<ShortName> Derivative Financial Instruments Nature and Amount of Collateral Received From and Posted To Our Derivative Counterparties (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 71 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R72.htm </HtmlFileName>
<LongName> 240324023 - Disclosure - Notional Amounts for Each Category of Derivative Activity (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/NotionalAmountsforEachCategoryofDerivativeActivityDetail </Role>
<ShortName> Notional Amounts for Each Category of Derivative Activity (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 72 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R73.htm </HtmlFileName>
<LongName> 240334024 - Disclosure - Derivative Financial Instruments Fair Value Hedges Carrying Amount of Hedged Assets and Liabilities and Cumulative Basis Adjustments (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/DerivativeFinancialInstrumentsFairValueHedgesCarryingAmountofHedgedAssetsandLiabilitiesandCumulativeBasisAdjustmentsDetails </Role>
<ShortName> Derivative Financial Instruments Fair Value Hedges Carrying Amount of Hedged Assets and Liabilities and Cumulative Basis Adjustments (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 73 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R74.htm </HtmlFileName>
<LongName> 240344025 - Disclosure - Location and Fair Values of Derivative Financial Instruments (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/LocationandFairValuesofDerivativeFinancialInstrumentsDetail </Role>
<ShortName> Location and Fair Values of Derivative Financial Instruments (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 74 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R75.htm </HtmlFileName>
<LongName> 240354026 - Disclosure - Derivative Financial Instruments Location of Gains and Losses Designated as Hedging Instruments, Consolidated Statements of Income (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/DerivativeFinancialInstrumentsLocationofGainsandLossesDesignatedasHedgingInstrumentsConsolidatedStatementsofIncomeDetails </Role>
<ShortName> Derivative Financial Instruments Location of Gains and Losses Designated as Hedging Instruments, Consolidated Statements of Income (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 75 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R76.htm </HtmlFileName>
<LongName> 240364027 - Disclosure - Location of Gains and Losses on Derivative Instruments Designated as Cash Flow Hedging Instruments (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/LocationofGainsandLossesonDerivativeInstrumentsDesignatedasCashFlowHedgingInstrumentsDetail </Role>
<ShortName> Location of Gains and Losses on Derivative Instruments Designated as Cash Flow Hedging Instruments (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 76 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R77.htm </HtmlFileName>
<LongName> 240374028 - Disclosure - Gains and Losses on Derivatives Not Designated as Hedging Instruments (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/GainsandLossesonDerivativesNotDesignatedasHedgingInstrumentsDetail </Role>
<ShortName> Gains and Losses on Derivatives Not Designated as Hedging Instruments (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 77 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R78.htm </HtmlFileName>
<LongName> 240384029 - Disclosure - Derivative Financial Instruments - Additional Information (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/DerivativeFinancialInstrumentsAdditionalInformationDetail </Role>
<ShortName> Derivative Financial Instruments - Additional Information (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 78 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R79.htm </HtmlFileName>
<LongName> 240414030 - Disclosure - Schedule of Accumulated Other Comprehensive Income (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ScheduleofAccumulatedOtherComprehensiveIncomeDetails </Role>
<ShortName> Schedule of Accumulated Other Comprehensive Income (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 79 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R80.htm </HtmlFileName>
<LongName> 240424031 - Disclosure - Schedule of Components of Unrealized Gain (Loss) on Securities (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ScheduleofComponentsofUnrealizedGainLossonSecuritiesDetails </Role>
<ShortName> Schedule of Components of Unrealized Gain (Loss) on Securities (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 80 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R81.htm </HtmlFileName>
<LongName> 240434032 - Disclosure - Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ScheduleofReclassificationsOutofAccumulatedOtherComprehensiveIncomeDetails </Role>
<ShortName> Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 81 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R82.htm </HtmlFileName>
<LongName> 240464033 - Disclosure - Liability for Unpaid Claims and Claims Adjustment Expense (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/LiabilityforUnpaidClaimsandClaimsAdjustmentExpenseDetail </Role>
<ShortName> Liability for Unpaid Claims and Claims Adjustment Expense (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 82 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R83.htm </HtmlFileName>
<LongName> 240474034 - Disclosure - Reconciliation of Policy and Contract Benefits and Reserves for Future Policy and Contract Benefits (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ReconciliationofPolicyandContractBenefitsandReservesforFuturePolicyandContractBenefitsDetail </Role>
<ShortName> Reconciliation of Policy and Contract Benefits and Reserves for Future Policy and Contract Benefits (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 83 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R84.htm </HtmlFileName>
<LongName> 240484035 - Disclosure - Liability for Unpaid Claims - Additional Information (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/LiabilityforUnpaidClaimsAdditionalInformationDetail </Role>
<ShortName> Liability for Unpaid Claims - Additional Information (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 84 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R85.htm </HtmlFileName>
<LongName> 240514036 - Disclosure - Income Tax Expense (Benefit) (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/IncomeTaxExpenseBenefitDetail </Role>
<ShortName> Income Tax Expense (Benefit) (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 85 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R86.htm </HtmlFileName>
<LongName> 240524037 - Disclosure - Reconciliation of income tax computed at US Federal tax rates (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ReconciliationofincometaxcomputedatUSFederaltaxratesDetail </Role>
<ShortName> Reconciliation of income tax computed at US Federal tax rates (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 86 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R87.htm </HtmlFileName>
<LongName> 240534038 - Disclosure - Schedule of deferred income tax assets and liabilities (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ScheduleofdeferredincometaxassetsandliabilitiesDetail </Role>
<ShortName> Schedule of deferred income tax assets and liabilities (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 87 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R88.htm </HtmlFileName>
<LongName> 240544039 - Disclosure - Schedule of Income subject to domestic and foreign taxation (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ScheduleofIncomesubjecttodomesticandforeigntaxationDetail </Role>
<ShortName> Schedule of Income subject to domestic and foreign taxation (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 88 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R89.htm </HtmlFileName>
<LongName> 240554040 - Disclosure - Unrecognized tax benefits (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/UnrecognizedtaxbenefitsDetail </Role>
<ShortName> Unrecognized tax benefits (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 89 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R90.htm </HtmlFileName>
<LongName> 240564041 - Disclosure - Income Tax Additional Information (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/IncomeTaxAdditionalInformationDetail </Role>
<ShortName> Income Tax Additional Information (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 90 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R91.htm </HtmlFileName>
<LongName> 240594042 - Disclosure - Debt Schedule (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/DebtScheduleDetail </Role>
<ShortName> Debt Schedule (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 91 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R92.htm </HtmlFileName>
<LongName> 240604043 - Disclosure - Debt - Additional Information (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/DebtAdditionalInformationDetails </Role>
<ShortName> Debt - Additional Information (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 92 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R93.htm </HtmlFileName>
<LongName> 240634044 - Disclosure - Employee Benefit Plans Change in Projected Benefit Obligation Amount (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/EmployeeBenefitPlansChangeinProjectedBenefitObligationAmountDetails </Role>
<ShortName> Employee Benefit Plans Change in Projected Benefit Obligation Amount (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 93 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R94.htm </HtmlFileName>
<LongName> 240644045 - Disclosure - Employee Benefit Plans Amounts Recognized in Balance Sheet (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/EmployeeBenefitPlansAmountsRecognizedinBalanceSheetDetails </Role>
<ShortName> Employee Benefit Plans Amounts Recognized in Balance Sheet (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 94 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R95.htm </HtmlFileName>
<LongName> 240654046 - Disclosure - Employee Benefit Plans Amounts Recognized in Other Comprehensive Income (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/EmployeeBenefitPlansAmountsRecognizedinOtherComprehensiveIncomeDetails </Role>
<ShortName> Employee Benefit Plans Amounts Recognized in Other Comprehensive Income (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 95 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R96.htm </HtmlFileName>
<LongName> 240664047 - Disclosure - Employee Benefit Plans US Pension Assets, Fair Value Measurement by Input Level (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/EmployeeBenefitPlansUSPensionAssetsFairValueMeasurementbyInputLevelDetails </Role>
<ShortName> Employee Benefit Plans US Pension Assets, Fair Value Measurement by Input Level (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 96 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R97.htm </HtmlFileName>
<LongName> 240674048 - Disclosure - Employee Benefit Plans UK Pension Assets, Fair Value Measurement by Input Level (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/EmployeeBenefitPlansUKPensionAssetsFairValueMeasurementbyInputLevelDetails </Role>
<ShortName> Employee Benefit Plans UK Pension Assets, Fair Value Measurement by Input Level (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 97 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R98.htm </HtmlFileName>
<LongName> 240684049 - Disclosure - Employee Benefit Plans OPEB Plan Assets, Fair Value Measurements by Input Level (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/EmployeeBenefitPlansOPEBPlanAssetsFairValueMeasurementsbyInputLevelDetails </Role>
<ShortName> Employee Benefit Plans OPEB Plan Assets, Fair Value Measurements by Input Level (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 98 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R99.htm </HtmlFileName>
<LongName> 240694050 - Disclosure - Employee Benefit Plans OPEB Changes in Assets Measured at Fair Value Using Signficant Unobservable Inputs (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/EmployeeBenefitPlansOPEBChangesinAssetsMeasuredatFairValueUsingSignficantUnobservableInputsDetails </Role>
<ShortName> Employee Benefit Plans OPEB Changes in Assets Measured at Fair Value Using Signficant Unobservable Inputs (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 99 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R100.htm </HtmlFileName>
<LongName> 240704051 - Disclosure - Employee Benefit Plans Measurement Assumptions (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/EmployeeBenefitPlansMeasurementAssumptionsDetails </Role>
<ShortName> Employee Benefit Plans Measurement Assumptions (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 100 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R101.htm </HtmlFileName>
<LongName> 240714052 - Disclosure - Employee Benefit Plans Net Periodic Benefit Cost (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/EmployeeBenefitPlansNetPeriodicBenefitCostDetail </Role>
<ShortName> Employee Benefit Plans Net Periodic Benefit Cost (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 101 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R102.htm </HtmlFileName>
<LongName> 240724053 - Disclosure - Employee Benefit Plans Expected Benefit Payments (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/EmployeeBenefitPlansExpectedBenefitPaymentsDetails </Role>
<ShortName> Employee Benefit Plans Expected Benefit Payments (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 102 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R103.htm </HtmlFileName>
<LongName> 240734054 - Disclosure - Employee Benefit Plans - Additional Information (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/EmployeeBenefitPlansAdditionalInformationDetail </Role>
<ShortName> Employee Benefit Plans - Additional Information (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 103 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R104.htm </HtmlFileName>
<LongName> 240764055 - Disclosure - Basic and Diluted Earnings Per Share (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/BasicandDilutedEarningsPerShareDetail </Role>
<ShortName> Basic and Diluted Earnings Per Share (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 104 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R105.htm </HtmlFileName>
<LongName> 240774056 - Disclosure - Treasury Stock Transactions (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/TreasuryStockTransactionsDetails </Role>
<ShortName> Treasury Stock Transactions (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 105 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R106.htm </HtmlFileName>
<LongName> 240784057 - Disclosure - Stockholders' Equity and Earnings Per Common Share - Additional Information (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/StockholdersEquityandEarningsPerCommonShareAdditionalInformationDetail </Role>
<ShortName> Stockholders' Equity and Earnings Per Common Share - Additional Information (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 106 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R107.htm </HtmlFileName>
<LongName> 240814058 - Disclosure - Stock-Based Compensation - Activity for PSUs Classified as Equity (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/StockBasedCompensationActivityforPSUsClassifiedasEquityDetails </Role>
<ShortName> Stock-Based Compensation - Activity for PSUs Classified as Equity (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 107 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R108.htm </HtmlFileName>
<LongName> 240824059 - Disclosure - Stock-Based Compensation - Valuation Assumptions on PSU Grants (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/StockBasedCompensationValuationAssumptionsonPSUGrantsDetails </Role>
<ShortName> Stock-Based Compensation - Valuation Assumptions on PSU Grants (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 108 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R109.htm </HtmlFileName>
<LongName> 240834060 - Disclosure - Stock-Based Compensation - Nonvested Stock Awards Classified in Equity (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/StockBasedCompensationNonvestedStockAwardsClassifiedinEquityDetails </Role>
<ShortName> Stock-Based Compensation - Nonvested Stock Awards Classified in Equity (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 109 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R110.htm </HtmlFileName>
<LongName> 240844061 - Disclosure - Stock option activity (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/StockoptionactivityDetails </Role>
<ShortName> Stock option activity (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 110 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R111.htm </HtmlFileName>
<LongName> 240854062 - Disclosure - Intrinsic Value of Options Exercised and Fair Value of Options Vested (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/IntrinsicValueofOptionsExercisedandFairValueofOptionsVestedDetails </Role>
<ShortName> Intrinsic Value of Options Exercised and Fair Value of Options Vested (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 111 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R112.htm </HtmlFileName>
<LongName> 240864063 - Disclosure - Stock-Based Compensation Expense (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/StockBasedCompensationExpenseDetails </Role>
<ShortName> Stock-Based Compensation Expense (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 112 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R113.htm </HtmlFileName>
<LongName> 240874064 - Disclosure - Stock-Based Compensation - Additional Information (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/StockBasedCompensationAdditionalInformationDetails </Role>
<ShortName> Stock-Based Compensation - Additional Information (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 113 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R114.htm </HtmlFileName>
<LongName> 240904065 - Disclosure - Reinsurance - Premium Income Data (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ReinsurancePremiumIncomeDataDetail </Role>
<ShortName> Reinsurance - Premium Income Data (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 114 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R115.htm </HtmlFileName>
<LongName> 240914066 - Disclosure - Reinsurance - Additional Information (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ReinsuranceAdditionalInformationDetail </Role>
<ShortName> Reinsurance - Additional Information (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 115 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R116.htm </HtmlFileName>
<LongName> 240944067 - Disclosure - Premium Income by Major Line of Business within Each Segment (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/PremiumIncomebyMajorLineofBusinesswithinEachSegmentDetail </Role>
<ShortName> Premium Income by Major Line of Business within Each Segment (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 116 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R117.htm </HtmlFileName>
<LongName> 240954068 - Disclosure - Selected Operating Statement Data by Segment (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/SelectedOperatingStatementDatabySegmentDetail </Role>
<ShortName> Selected Operating Statement Data by Segment (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 117 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R118.htm </HtmlFileName>
<LongName> 240964069 - Disclosure - Segment Information Deferred Acquisition Costs by Segment (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/SegmentInformationDeferredAcquisitionCostsbySegmentDetails </Role>
<ShortName> Segment Information Deferred Acquisition Costs by Segment (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 118 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R119.htm </HtmlFileName>
<LongName> 240974070 - Disclosure - Assets by Segment (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/AssetsbySegmentDetail </Role>
<ShortName> Assets by Segment (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 119 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R120.htm </HtmlFileName>
<LongName> 240984071 - Disclosure - Reconciliation of Total Revenue and Income Before Income Tax to Operating Revenue and Operating Income (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ReconciliationofTotalRevenueandIncomeBeforeIncomeTaxtoOperatingRevenueandOperatingIncomeDetail </Role>
<ShortName> Reconciliation of Total Revenue and Income Before Income Tax to Operating Revenue and Operating Income (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 120 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R121.htm </HtmlFileName>
<LongName> 240994072 - Disclosure - Segment Information Segments - Additional Information (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/SegmentInformationSegmentsAdditionalInformationDetail </Role>
<ShortName> Segment Information Segments - Additional Information (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 121 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R122.htm </HtmlFileName>
<LongName> 241034073 - Disclosure - Leases, Cost (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/LeasesCostDetails </Role>
<ShortName> Leases, Cost (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 122 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R123.htm </HtmlFileName>
<LongName> 241044074 - Disclosure - Lessee, Operating Lease, Liability, Payment, Due (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/LesseeOperatingLeaseLiabilityPaymentDueDetails </Role>
<ShortName> Lessee, Operating Lease, Liability, Payment, Due (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 123 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R124.htm </HtmlFileName>
<LongName> 241054075 - Disclosure - Leases - Additional Information (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/LeasesAdditionalInformationDetails </Role>
<ShortName> Leases - Additional Information (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 124 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R125.htm </HtmlFileName>
<LongName> 241084076 - Disclosure - Statutory Financial Information (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/StatutoryFinancialInformationDetail </Role>
<ShortName> Statutory Financial Information (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<ParentRole> http://www.unum.com/role/StatutoryFinancialInformationTables </ParentRole>
<Position> 125 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R126.htm </HtmlFileName>
<LongName> 241094077 - Disclosure - Statutory Financial Information - Additional Details (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/StatutoryFinancialInformationAdditionalDetailsDetail </Role>
<ShortName> Statutory Financial Information - Additional Details (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 126 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R127.htm </HtmlFileName>
<LongName> 241124078 - Disclosure - Schedule of Unaudited Quarterly Results (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ScheduleofUnauditedQuarterlyResultsDetail </Role>
<ShortName> Schedule of Unaudited Quarterly Results (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 127 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R128.htm </HtmlFileName>
<LongName> 241144079 - Disclosure - Schedule I - Summary of Investments, Other Than Investments in Related Parties Schedule I - Summary of Investments, Other Than Investments in Related Parties (Details) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ScheduleISummaryofInvestmentsOtherThanInvestmentsinRelatedPartiesScheduleISummaryofInvestmentsOtherThanInvestmentsinRelatedPartiesDetails </Role>
<ShortName> Schedule I - Summary of Investments, Other Than Investments in Related Parties Schedule I - Summary of Investments, Other Than Investments in Related Parties (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<ParentRole> http://www.unum.com/role/ScheduleISummaryofInvestmentsOtherThanInvestmentsinRelatedPartiesScheduleISummaryofInvestmentsOtherThanInvestmentsinRelatedParties </ParentRole>
<Position> 128 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R129.htm </HtmlFileName>
<LongName> 241174080 - Disclosure - Parent Company Balance Sheet (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ParentCompanyBalanceSheetDetail </Role>
<ShortName> Parent Company Balance Sheet (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 129 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R130.htm </HtmlFileName>
<LongName> 241184081 - Disclosure - Parent Company Statement of Income (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ParentCompanyStatementofIncomeDetail </Role>
<ShortName> Parent Company Statement of Income (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 130 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R131.htm </HtmlFileName>
<LongName> 241194082 - Disclosure - Parent Company Cash Flow Statement (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ParentCompanyCashFlowStatementDetail </Role>
<ShortName> Parent Company Cash Flow Statement (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 131 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R132.htm </HtmlFileName>
<LongName> 241204083 - Disclosure - Parent Company Debt Schedule (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ParentCompanyDebtScheduleDetail </Role>
<ShortName> Parent Company Debt Schedule (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 132 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R133.htm </HtmlFileName>
<LongName> 241214084 - Disclosure - Parent Company Notes - Additional Details (Details) </LongName>
<ReportType> Notes </ReportType>
<Role> http://www.unum.com/role/ParentCompanyNotesAdditionalDetailsDetails </Role>
<ShortName> Parent Company Notes - Additional Details (Details) </ShortName>
<MenuCategory> Details </MenuCategory>
<Position> 133 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R134.htm </HtmlFileName>
<LongName> 241234085 - Disclosure - Schedule III Supplementary Insurance Information (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ScheduleIIISupplementaryInsuranceInformationDetail </Role>
<ShortName> Schedule III Supplementary Insurance Information (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<ParentRole> http://www.unum.com/role/ScheduleIIISupplementaryInsuranceInformation </ParentRole>
<Position> 134 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R135.htm </HtmlFileName>
<LongName> 241254086 - Disclosure - Schedule IV Reinsurance (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ScheduleIVReinsuranceDetail </Role>
<ShortName> Schedule IV Reinsurance (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<ParentRole> http://www.unum.com/role/ScheduleIVReinsurance </ParentRole>
<Position> 135 </Position>
</Report>
<Report instance="unm-20191231.htm">
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<HtmlFileName> R136.htm </HtmlFileName>
<LongName> 241274087 - Disclosure - Schedule V Valuation and Qualifying Accounts (Detail) </LongName>
<ReportType> Sheet </ReportType>
<Role> http://www.unum.com/role/ScheduleVValuationandQualifyingAccountsDetail </Role>
<ShortName> Schedule V Valuation and Qualifying Accounts (Detail) </ShortName>
<MenuCategory> Details </MenuCategory>
<ParentRole> http://www.unum.com/role/ScheduleVValuationandQualifyingAccounts </ParentRole>
<Position> 136 </Position>
</Report>
<Report>
<IsDefault> false </IsDefault>
<HasEmbeddedReports> false </HasEmbeddedReports>
<LongName> All Reports </LongName>
<ReportType> Book </ReportType>
<ShortName> All Reports </ShortName>
</Report>
</MyReports>
<InputFiles>
<File doctype="10-K" original="unm-20191231.htm"> unm-20191231.htm </File>
<File> unm-20191231.xsd </File>
<File> unm-20191231_cal.xml </File>
<File> unm-20191231_def.xml </File>
<File> unm-20191231_lab.xml </File>
<File> unm-20191231_pre.xml </File>
<File> unm123119ex1015.htm </File>
<File> unm123119ex1037.htm </File>
<File> unm123119ex1038.htm </File>
<File> unm123119ex1039.htm </File>
<File> unm123119ex1040.htm </File>
<File> unm123119ex1041.htm </File>
<File> unm123119ex21.htm </File>
<File> unm123119ex23.htm </File>
<File> unm123119ex24.htm </File>
<File> unm123119ex311.htm </File>
<File> unm123119ex312.htm </File>
<File> unm123119ex321.htm </File>
<File> unm123119ex322.htm </File>
</InputFiles>
<SupplementalFiles/>
<BaseTaxonomies>
<BaseTaxonomy> http://fasb.org/srt/2019-01-31 </BaseTaxonomy>
<BaseTaxonomy> http://xbrl.sec.gov/country/2017-01-31 </BaseTaxonomy>
<BaseTaxonomy> http://xbrl.sec.gov/exch/2019-01-31 </BaseTaxonomy>
<BaseTaxonomy> http://xbrl.sec.gov/dei/2019-01-31 </BaseTaxonomy>
<BaseTaxonomy> http://fasb.org/us-gaap/2019-01-31 </BaseTaxonomy>
<BaseTaxonomy> http://xbrl.sec.gov/invest/2013-01-31 </BaseTaxonomy>
</BaseTaxonomies>
<HasPresentationLinkbase> true </HasPresentationLinkbase>
<HasCalculationLinkbase> true </HasCalculationLinkbase>
</FilingSummary>


6 Subsequent Filings that Reference this Filing

  As Of               Filer                 Filing    For·On·As Docs:Size             Issuer                      Filing Agent

 2/20/24  Unum Group                        10-K       12/31/23  158:41M
 2/23/23  Unum Group                        10-K       12/31/22  158:34M
 2/25/22  Unum Group                        10-K       12/31/21  165:35M
 6/11/21  Unum Group                        424B2                  1:776K                                   Donnelley … Solutions/FA
 2/17/21  Unum Group                        10-K       12/31/20  167:35M
 8/20/20  Unum Group                        S-3ASR      8/20/20    7:859K
Top
Filing Submission 0000005513-20-000027   –   Alternative Formats (Word / Rich Text, HTML, Plain Text, et al.)

Copyright © 2024 Fran Finnegan & Company LLC – All Rights Reserved.
AboutPrivacyRedactionsHelp — Fri., May 17, 10:53:05.1pm ET