v3.26.3
Segment Information - Reconciliation of Other Items from Segments to Consolidated (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Segment Reporting [Line Items]        
Deferred Policy Acquisition Costs, Amortization Expense $ 679 $ 639 $ 2,004 $ 1,871
Insurance operating costs and other expense 1,177 1,203 3,620 3,488
Amortization of other intangible assets 18 18 53 53
Benefits, Losses and Expenses 5,637 5,703 17,619 17,067
Policyholder Benefits and Claims Incurred, Net 3,713 3,793 11,792 11,505
Operating Segments [Member]        
Segment Reporting [Line Items]        
Deferred Policy Acquisition Costs, Amortization Expense 679 639 2,004 1,871
Amortization of other intangible assets 18 18 53 53
Benefits, Losses and Expenses 5,547 5,613 17,319 16,801
Operating Segments [Member] | P&C Business Insurance        
Segment Reporting [Line Items]        
Prior accident year development [1] (61) (60) (83) (289)
Deferred Policy Acquisition Costs, Amortization Expense 600 559 1,767 1,636
Insurance operating costs and other expense 536 546 1,633 1,565
Amortization of other intangible assets 7 7 21 21
Policyholder Dividends, Expense 10 12 34 33
Benefits, Losses and Expenses 3,460 3,154 10,218 9,293
Operating Segments [Member] | P&C Personal Insurance        
Segment Reporting [Line Items]        
Prior accident year development [1] (36) (43) (130) (123)
Deferred Policy Acquisition Costs, Amortization Expense 70 72 211 210
Insurance operating costs and other expense 174 180 529 534
Amortization of other intangible assets 1 1 2 2
Benefits, Losses and Expenses 859 851 2,483 2,697
Operating Segments [Member] | Property & Casualty Other Operations [Member]        
Segment Reporting [Line Items]        
Prior accident year development [1] (497) 0 (533) 0
Deferred Policy Acquisition Costs, Amortization Expense 0 0 0 0
Insurance operating costs and other expense 2 2 6 6
Amortization of other intangible assets 0 0 0 0
Benefits, Losses and Expenses (495) 2 (527) 6
Operating Segments [Member] | Employee Benefits [Member]        
Segment Reporting [Line Items]        
Deferred Policy Acquisition Costs, Amortization Expense 9 8 26 25
Insurance operating costs and other expense 417 425 1,273 1,238
Amortization of other intangible assets 10 10 30 30
Benefits, Losses and Expenses 1,723 1,606 5,145 4,805
Operating Segments [Member] | Employee Benefits [Member] | Disability Insurance Policy [Member]        
Segment Reporting [Line Items]        
Policyholder Benefits and Claims Incurred, Net 721 628 2,136 1,866
Operating Segments [Member] | Employee Benefits [Member] | Life Insurance Product Line [Member]        
Segment Reporting [Line Items]        
Policyholder Benefits and Claims Incurred, Net 498 481 1,470 1,478
Operating Segments [Member] | Employee Benefits [Member] | Insurance, Other [Member]        
Segment Reporting [Line Items]        
Policyholder Benefits and Claims Incurred, Net 68 54 210 168
Non-Catastrophe [Member] | Operating Segments [Member] | P&C Business Insurance        
Segment Reporting [Line Items]        
Current accident year 2,262 2,051 6,440 5,894
Non-Catastrophe [Member] | Operating Segments [Member] | P&C Personal Insurance        
Segment Reporting [Line Items]        
Current accident year 558 610 1,627 1,758
Catastrophe | Operating Segments [Member] | P&C Business Insurance        
Segment Reporting [Line Items]        
Current accident year 106 39 406 433
Catastrophe | Operating Segments [Member] | P&C Personal Insurance        
Segment Reporting [Line Items]        
Current accident year $ 92 $ 31 $ 244 $ 316