v3.26.3
Reportable Segments - Schedule of Reportable Segments Expense Information Used in Measure for Segment Profit or Loss (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Segment Reporting        
Prior year reserve reestimates excluding catastrophes $ (753) $ (424) $ (2,398) $ (1,045)
Accident, health and other policy benefits 77 67 225 588
Amortization of DAC 2,220 2,101 6,600 6,264
Amortization of purchased intangibles 46 59 139 175
Interest expense 97 101 291 301
Restructuring and related charges 40 17 52 48
Income Tax Expense (Benefit) 537 1,075 2,058 1,802
Preferred stock dividends 29 29 88 88
Non-catastrophe losses        
Segment Reporting        
Prior year reserve reestimates excluding catastrophes (763) (396) (2,471) (1,007)
Catastrophe        
Segment Reporting        
Prior year reserve reestimates excluding catastrophes 10 (28) 73 (38)
Loss adjustment expenses, net of reinsurance     4,610 4,750
Operating segments | Allstate Protection | Allstate Protection        
Segment Reporting        
Property and casualty insurance claims and claims expense 8,856 8,304 26,262 25,467
Amortization of DAC 1,854 1,757 5,515 5,231
Advertising expense 589 575 1,657 1,540
Amortization of purchased intangibles 38 46 115 138
Restructuring and related charges 39 15 46 44
Other segment expenses 1,363 1,298 4,057 3,717
Total 13,410 12,011 39,577 39,729
Loss adjustment expenses, net of reinsurance 862 741 2,440 2,220
Operating segments | Allstate Protection | Allstate Protection | Non-catastrophe losses        
Segment Reporting        
Prior year reserve reestimates excluding catastrophes (979) (542) (2,687) (1,158)
Operating segments | Allstate Protection | Allstate Protection | Catastrophe        
Segment Reporting        
Property and casualty insurance claims and claims expense 1,650 558 4,612 4,750
Operating segments | Allstate Protection | Run-off Property-Liability        
Segment Reporting        
Property and casualty insurance claims and claims expense 216 146 216 151
Other segment expenses 2 0 3 2
Total 218 146 219 153
Operating segments | Protection Services        
Segment Reporting        
Property and casualty insurance claims and claims expense 208 193 605 524
Amortization of DAC 358 337 1,062 983
Non-deferrable commissions 127 116 377 327
Restructuring and related charges 1 1 5 2
Other segment expenses 189 194 558 582
Income Tax Expense (Benefit) 17 16 51 51
Total 900 857 2,658 2,469
Operating segments | Allstate Health and Benefits        
Segment Reporting        
Accident, health and other policy benefits 0 0 0 379
Amortization of DAC 0 0 0 30
Other segment expenses 0 0 0 213
Income Tax Expense (Benefit) 0 0 0 12
Total 0 0 0 634
Operating segments | Corporate        
Segment Reporting        
Interest expense 97 101 291 301
Other segment expenses 25 42 91 119
Income Tax Expense (Benefit) (3) (12) (22) (60)
Preferred stock dividends 29 29 88 88
Total $ 148 $ 160 $ 448 $ 448