v3.26.3
Reportable Segments - Schedule of Reportable Segments Revenue Information (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Segment Reporting        
Net investment income $ 1,177 $ 949 $ 3,124 $ 2,557
Net gains (losses) on investments and derivatives (545) 252 105 (241)
Total revenues 17,348 17,255 52,885 50,340
Operating segments | Property Liability        
Segment Reporting        
Insurance premiums 15,650 15,051 46,482 44,416
Other revenue 564 518 1,676 1,510
Net investment income 1,052 873 2,782 2,343
Net gains (losses) on investments and derivatives (471) 157 200 (362)
Operating segments | Property Liability | Total Allstate Protection insurance premiums        
Segment Reporting        
Insurance premiums 15,086 14,533 44,806 42,906
Operating segments | Property Liability | Run-off Property-Liability        
Segment Reporting        
Insurance premiums 0 0 0 0
Operating segments | Protection Services        
Segment Reporting        
Intersegment premiums and service fees 43 33 109 106
Other revenue 124 124 364 363
Net investment income 27 25 75 74
Net gains (losses) on investments and derivatives (18) 10 1 1
Total revenues 946 912 2,822 2,630
Operating segments | Allstate Health and Benefits        
Segment Reporting        
Other revenue 0 0 0 163
Net investment income 0 0 0 24
Net gains (losses) on investments and derivatives 0 0 0 (1)
Total revenues 0 0 0 676
Operating segments | Corporate        
Segment Reporting        
Other revenue 9 24 38 62
Net investment income 96 49 260 108
Net gains (losses) on investments and derivatives (54) 85 (93) 122
Total revenues 51 158 205 292
Operating segments | Auto | Property Liability | Total Allstate Protection insurance premiums        
Segment Reporting        
Insurance premiums 9,654 9,593 28,845 28,468
Operating segments | Homeowners | Property Liability | Total Allstate Protection insurance premiums        
Segment Reporting        
Insurance premiums 4,325 3,880 12,690 11,308
Operating segments | Specialty lines | Property Liability | Total Allstate Protection insurance premiums        
Segment Reporting        
Insurance premiums 839 800 2,481 2,320
Operating segments | Commercial lines | Property Liability | Total Allstate Protection insurance premiums        
Segment Reporting        
Insurance premiums 113 99 321 316
Operating segments | Brokered solutions and collateral protection | Property Liability | Total Allstate Protection insurance premiums        
Segment Reporting        
Insurance premiums 155 161 469 494
Operating segments | Protection plans | Protection Services        
Segment Reporting        
Insurance premiums 592 552 1,748 1,593
Operating segments | Roadside assistance | Protection Services        
Segment Reporting        
Insurance premiums 54 42 150 117
Operating segments | Protection and insurance products | Protection Services        
Segment Reporting        
Insurance premiums 124 126 375 376
Operating segments | Employer voluntary benefits | Allstate Health and Benefits        
Segment Reporting        
Insurance premiums 0 0 0 243
Operating segments | Group health | Allstate Health and Benefits        
Segment Reporting        
Insurance premiums 0 0 0 247
All other        
Segment Reporting        
Net gains (losses) on investments and derivatives (545) 252 105 (241)
Total revenues 163 137 503 451
All other | Property Liability        
Segment Reporting        
Net investment income 1,052 873 2,782 2,343
Intersegment eliminations        
Segment Reporting        
Total revenues $ (43) $ (33) $ (109) $ (106)