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Rli Corp – ‘10-K’ for 12/31/18 – ‘XML’

On:  Friday, 2/22/19, at 1:59pm ET   ·   For:  12/31/18   ·   Accession #:  84246-19-13   ·   File #:  1-09463

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

 2/22/19  Rli Corp                          10-K       12/31/18   98:37M

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   3.26M 
 2: EX-21.1     Subsidiaries List                                   HTML     39K 
 3: EX-23.1     Consent of Experts or Counsel                       HTML     29K 
 4: EX-31.1     Certification -- §302 - SOA'02                      HTML     34K 
 5: EX-31.2     Certification -- §302 - SOA'02                      HTML     34K 
 6: EX-32.1     Certification -- §906 - SOA'02                      HTML     30K 
 7: EX-32.2     Certification -- §906 - SOA'02                      HTML     30K 
14: R1          Document and Entity Information                     HTML     62K 
15: R2          Consolidated Balance Sheets                         HTML    127K 
16: R3          Consolidated Balance Sheets (Parenthetical)         HTML     52K 
17: R4          Consolidated Statements of Earnings and             HTML    119K 
                Comprehensive Earnings                                           
18: R5          Consolidated Statements of Shareholders' Equity     HTML     74K 
19: R6          Consolidated Statements of Shareholders' Equity     HTML     33K 
                (Parenthetical)                                                  
20: R7          Consolidated Statements of Cash Flows               HTML    154K 
21: R8          Summary of Significant Accounting Policies          HTML    355K 
22: R9          Investments                                         HTML    816K 
23: R10         Policy Acquisition Costs                            HTML     91K 
24: R11         Debt                                                HTML     34K 
25: R12         Reinsurance                                         HTML    201K 
26: R13         Historical Loss and Lae Development                 HTML   2.01M 
27: R14         Income Taxes                                        HTML    175K 
28: R15         Employee Benefits                                   HTML    218K 
29: R16         Statutory Information and Dividend Restrictions     HTML     52K 
30: R17         Commitments and Contingent Liabilities              HTML     51K 
31: R18         Operating Segment Information                       HTML    303K 
32: R19         Unaudited Interim Financial Information             HTML    143K 
33: R20         Schedule I-Summary of Investments-Other Than        HTML    125K 
                Investments in Related Parties                                   
34: R21         Schedule Ii-Condensed Financial Information of      HTML    340K 
                Registrant (Parent Company)                                      
35: R22         Schedule Iii-Supplementary Insurance Information    HTML    311K 
36: R23         Schedule Iv-Reinsurance                             HTML    175K 
37: R24         Schedule V-Valuation and Qualifying Accounts        HTML     72K 
38: R25         Schedule Vi-Supplementary Information Concerning    HTML    115K 
                Property-Casualty Insurance Operations                           
39: R26         Summary of Significant Accounting Policies          HTML    412K 
                (Policies)                                                       
40: R27         Summary of Significant Accounting Policies          HTML    254K 
                (Tables)                                                         
41: R28         Investments (Tables)                                HTML    807K 
42: R29         Policy Acquisition Costs (Tables)                   HTML     91K 
43: R30         Reinsurance (Tables)                                HTML    195K 
44: R31         Historical Loss and Lae Development (Tables)        HTML   2.00M 
45: R32         Income Taxes (Tables)                               HTML    168K 
46: R33         Employee Benefits (Tables)                          HTML    199K 
47: R34         Statutory Information and Dividend Restrictions     HTML     43K 
                (Tables)                                                         
48: R35         Commitments and Contingent Liabilities (Tables)     HTML     44K 
49: R36         Operating Segment Information (Tables)              HTML    300K 
50: R37         Unaudited Interim Financial Information (Tables)    HTML    142K 
51: R38         SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES -        HTML     46K 
                Description of Business (Details)                                
52: R39         SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES -        HTML     81K 
                Accounting Standards (Details)                                   
53: R40         SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES -        HTML     36K 
                Property and Equipment (Details)                                 
54: R41         SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES -        HTML     98K 
                Investment in Unconsolidated Investees (Details)                 
55: R42         SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES -        HTML     77K 
                Intangible Assets (Details)                                      
56: R43         SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES -        HTML     69K 
                Earnings Per Share (Details)                                     
57: R44         SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES -        HTML     95K 
                Changes in Accumulated Other Comprehensive                       
                Earnings (Details)                                               
58: R45         SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES -        HTML     31K 
                Insurance Risk (Details)                                         
59: R46         SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES -        HTML     38K 
                Catastrophe Exposures (Details)                                  
60: R47         INVESTMENTS - Net Investment Income (Details)       HTML     48K 
61: R48         INVESTMENTS - Realized and Unrealized Gains         HTML     64K 
                (Details)                                                        
62: R49         INVESTMENTS - Disposition of Fixed Securities and   HTML     51K 
                Equities (Details)                                               
63: R50         INVESTMENTS - Assets Measured At Fair Value         HTML     84K 
                (Details)                                                        
64: R51         INVESTMENTS - Fixed Income Securities By            HTML     63K 
                Contractual Maturity (Details)                                   
65: R52         INVESTMENTS - Investments In Fixed Income           HTML     82K 
                Securities (Details)                                             
66: R53         INVESTMENTS - Types of Debt and Equity Securities   HTML     96K 
                (Details)                                                        
67: R54         INVESTMENTS - Portfolio Analysis (Details)          HTML     40K 
68: R55         INVESTMENTS - Other Invested Assets (Details)       HTML     50K 
69: R56         Policy Acquisition Costs (Details)                  HTML     55K 
70: R57         Debt (Details)                                      HTML     62K 
71: R58         REINSURANCE - Summary of Premiums and Losses        HTML     75K 
                (Details)                                                        
72: R59         REINSURANCE - Summary of Reinsurers (Details)       HTML    113K 
73: R60         HISTORICAL LOSS AND LAE DEVELOPMENT - Unpaid        HTML     72K 
                Losses and Settlement Expenses (Details)                         
74: R61         HISTORICAL LOSS AND LAE DEVELOPMENT - Incurred      HTML    336K 
                Losses and Loss Adjustment Expenses, Net of                      
                Reinsurance (Details)                                            
75: R62         HISTORICAL LOSS AND LAE DEVELOPMENT - Cumulative    HTML     83K 
                Paid Loss and Loss Adjustment Expenses, Net of                   
                Reinsurance (Details)                                            
76: R63         HISTORICAL LOSS AND LAE DEVELOPMENT -               HTML     72K 
                Reconciliation of Incurred and Paid Loss                         
                Development to the Liability for Unpaid Losses and               
                Settlement Expenses (Details)                                    
77: R64         HISTORICAL LOSS AND LAE DEVELOPMENT - Reserve       HTML     83K 
                Development (Details)                                            
78: R65         HISTORICAL LOSS AND LAE DEVELOPMENT -               HTML     51K 
                Environmental, Asbestos and Mass Tort Exposures                  
                (Details)                                                        
79: R66         Income Taxes (Details)                              HTML    152K 
80: R67         EMPLOYEE BENEFITS - Stock Ownership and Incentive   HTML     57K 
                Plans (Details)                                                  
81: R68         EMPLOYEE BENEFITS - Stock Options and Stock Plans   HTML    159K 
                (Details)                                                        
82: R69         Statutory Information and Dividend Restrictions     HTML     62K 
                (Details)                                                        
83: R70         Commitments and Contingent Liabilities (Details)    HTML     67K 
84: R71         OPERATING SEGMENT INFORMATION - Summary of          HTML    115K 
                Segments (Details)                                               
85: R72         OPERATING SEGMENT INFORMATION - Revenue by Product  HTML     92K 
                (Details)                                                        
86: R73         Unaudited Interim Financial Information (Details)   HTML     63K 
87: R74         Schedule I-Summary of Investments-Other Than        HTML     74K 
                Investments in Related Parties (Details)                         
88: R75         Schedule Ii-Condensed Financial Information of      HTML    124K 
                Registrant (PARENT COMPANY) - Balance Sheets                     
                (Details)                                                        
89: R76         Schedule Ii-Condensed Financial Information of      HTML     50K 
                Registrant (PARENT COMPANY) - Balance Sheets                     
                Information (Details)                                            
90: R77         Schedule Ii-Condensed Financial Information of      HTML     99K 
                Registrant (PARENT COMPANY) - Statements of                      
                Earnings and Comprehensive Earnings (Details)                    
91: R78         Schedule Ii-Condensed Financial Information of      HTML    146K 
                Registrant (PARENT COMPANY) - Statements of Cash                 
                Flows (Details)                                                  
92: R79         Schedule Iii-Supplementary Insurance Information    HTML     70K 
                (Details)                                                        
93: R80         Schedule Iv-Reinsurance (Details)                   HTML     65K 
94: R81         Schedule V-Valuation and Qualifying Accounts        HTML     36K 
                (Details)                                                        
95: R82         Schedule Vi-Supplementary Information Concerning    HTML     58K 
                Property-Casualty Insurance Operations (Details)                 
97: XML         IDEA XML File -- Filing Summary                      XML    181K 
96: EXCEL       IDEA Workbook of Financial Reports                  XLSX    173K 
 8: EX-101.INS  XBRL Instance -- rli-20181231                        XML  13.18M 
10: EX-101.CAL  XBRL Calculations -- rli-20181231_cal                XML    378K 
11: EX-101.DEF  XBRL Definitions -- rli-20181231_def                 XML   1.06M 
12: EX-101.LAB  XBRL Labels -- rli-20181231_lab                      XML   2.22M 
13: EX-101.PRE  XBRL Presentations -- rli-20181231_pre               XML   1.65M 
 9: EX-101.SCH  XBRL Schema -- rli-20181231                          XSD    260K 
98: ZIP         XBRL Zipped Folder -- 0000084246-19-000013-xbrl      Zip    483K 


‘XML’   —   IDEA XML File — Filing Summary


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Filing Submission 0000084246-19-000013   –   Alternative Formats (Word / Rich Text, HTML, Plain Text, et al.)

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