v3.26.1
Reportable Segments - Schedule of Reportable Segments Revenue Information (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Segment Reporting        
Net investment income $ 1,009 $ 754 $ 1,947 $ 1,608
Net gains (losses) on investments and derivatives 1,055 (144) 650 (493)
Total revenues 18,596 16,633 35,537 33,085
Operating segments | Property Liability        
Segment Reporting        
Insurance premiums 15,486 14,850 30,832 29,365
Other revenue 568 504 1,112 992
Net investment income 885 687 1,730 1,470
Net gains (losses) on investments and derivatives 999 (190) 671 (519)
Operating segments | Property Liability | Total Allstate Protection insurance premiums        
Segment Reporting        
Insurance premiums 14,918 14,346 29,720 28,373
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 35 36 66 73
Other revenue 123 111 240 239
Net investment income 25 25 48 49
Net gains (losses) on investments and derivatives 26 1 19 (9)
Total revenues 961 868 1,876 1,718
Operating segments | Allstate Health and Benefits        
Segment Reporting        
Other revenue 0 79 0 163
Net investment income 0 1 0 24
Net gains (losses) on investments and derivatives 0 (1) 0 (1)
Total revenues 0 202 0 676
Operating segments | Corporate        
Segment Reporting        
Other revenue 12 23 29 38
Net investment income 96 37 164 59
Net gains (losses) on investments and derivatives 31 46 (39) 37
Total revenues 139 106 154 134
Operating segments | Auto | Property Liability | Total Allstate Protection insurance premiums        
Segment Reporting        
Insurance premiums 9,644 9,528 19,191 18,875
Operating segments | Homeowners | Property Liability | Total Allstate Protection insurance premiums        
Segment Reporting        
Insurance premiums 4,201 3,771 8,365 7,428
Operating segments | Specialty lines | Property Liability | Total Allstate Protection insurance premiums        
Segment Reporting        
Insurance premiums 822 779 1,642 1,520
Operating segments | Commercial lines | Property Liability | Total Allstate Protection insurance premiums        
Segment Reporting        
Insurance premiums 107 104 208 217
Operating segments | Brokered solutions and collateral protection | Property Liability | Total Allstate Protection insurance premiums        
Segment Reporting        
Insurance premiums 144 164 314 333
Operating segments | Protection plans | Protection Services        
Segment Reporting        
Insurance premiums 578 531 1,156 1,041
Operating segments | Roadside assistance | Protection Services        
Segment Reporting        
Insurance premiums 49 39 96 75
Operating segments | Protection and insurance products | Protection Services        
Segment Reporting        
Insurance premiums 125 125 251 250
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 0 123 0 247
All other        
Segment Reporting        
Net gains (losses) on investments and derivatives 1,055 (144) 650 (493)
Total revenues 161 146 340 314
All other | Property Liability        
Segment Reporting        
Net investment income 885 687 1,730 1,470
Intersegment eliminations        
Segment Reporting        
Total revenues $ (35) $ (36) $ (66) $ (73)