v3.24.2
Segment Information (Details)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2024
USD ($)
Jun. 30, 2023
USD ($)
Jun. 30, 2024
USD ($)
segment
Jun. 30, 2023
USD ($)
Segment reporting information        
Number of reportable business segments | segment     3  
Premiums $ 10,243 $ 9,216 $ 20,369 $ 18,070
Net investment income 885 712 1,731 1,375
Fee income 115 106 224 212
Other revenues 105 99 217 174
Net realized investment losses (65) (35) (30) (29)
Total revenues 11,283 10,098 22,511 19,802
Core income (loss) 585 15 1,681 985
Net realized investment losses, net of tax (51) (29) (24) (24)
Net income (loss) 534 (14) 1,657 961
Reportable Segments [Member]        
Segment reporting information        
Premiums 10,243 9,216 20,369 18,070
Net investment income 885 712 1,731 1,375
Fee income 115 106 224 212
Other revenues 105 99 217 174
Total segment revenues 11,348 10,133 22,541 19,831
Core income (loss) 673 94 1,852 1,140
Reportable Segments [Member] | Business Insurance [Member]        
Segment reporting information        
Premiums 5,168 4,644 10,328 9,121
Net investment income 632 509 1,241 982
Fee income 105 98 206 197
Other revenues 77 67 154 114
Total segment revenues 5,982 5,318 11,929 10,414
Core income (loss) 656 402 1,420 1,158
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member]        
Segment reporting information        
Premiums 4,736 4,325 9,483 8,523
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member] | Workers' compensation [Member]        
Segment reporting information        
Premiums 864 858 1,744 1,708
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member] | Automobile [Member]        
Segment reporting information        
Premiums 874 798 1,734 1,559
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member] | Commercial property [Member]        
Segment reporting information        
Premiums 894 760 1,767 1,469
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member] | General liability [Member]        
Segment reporting information        
Premiums 845 748 1,692 1,508
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member] | Commercial multi-peril [Member]        
Segment reporting information        
Premiums 1,246 1,145 2,516 2,245
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member] | Other [Member]        
Segment reporting information        
Premiums 13 16 30 34
Reportable Segments [Member] | Business Insurance [Member] | International [Member]        
Segment reporting information        
Premiums 432 319 845 598
Reportable Segments [Member] | Bond & Specialty Insurance [Member]        
Segment reporting information        
Premiums 977 911 1,933 1,786
Net investment income 94 78 184 151
Fee income 0 0 0 0
Other revenues 6 7 15 12
Total segment revenues 1,077 996 2,132 1,949
Core income (loss) 170 230 365 437
Reportable Segments [Member] | Bond & Specialty Insurance [Member] | Domestic [Member]        
Segment reporting information        
Premiums 845 788 1,667 1,546
Reportable Segments [Member] | Bond & Specialty Insurance [Member] | Domestic [Member] | General liability [Member]        
Segment reporting information        
Premiums 437 406 863 804
Reportable Segments [Member] | Bond & Specialty Insurance [Member] | Domestic [Member] | Fidelity and surety [Member]        
Segment reporting information        
Premiums 350 325 690 631
Reportable Segments [Member] | Bond & Specialty Insurance [Member] | Domestic [Member] | Other [Member]        
Segment reporting information        
Premiums 58 57 114 111
Reportable Segments [Member] | Bond & Specialty Insurance [Member] | International [Member]        
Segment reporting information        
Premiums 132 123 266 240
Reportable Segments [Member] | Personal Insurance [Member]        
Segment reporting information        
Premiums 4,098 3,661 8,108 7,163
Net investment income 159 125 306 242
Fee income 10 8 18 15
Other revenues 22 25 48 48
Total segment revenues 4,289 3,819 8,480 7,468
Core income (loss) (153) (538) 67 (455)
Reportable Segments [Member] | Personal Insurance [Member] | Domestic [Member]        
Segment reporting information        
Premiums 3,933 3,502 7,779 6,850
Reportable Segments [Member] | Personal Insurance [Member] | Domestic [Member] | Automobile [Member]        
Segment reporting information        
Premiums 1,919 1,688 3,793 3,312
Reportable Segments [Member] | Personal Insurance [Member] | Domestic [Member] | Homeowners and Other [Member]        
Segment reporting information        
Premiums 2,014 1,814 3,986 3,538
Reportable Segments [Member] | Personal Insurance [Member] | International [Member]        
Segment reporting information        
Premiums 165 159 329 313
Other [Member]        
Segment reporting information        
Core income (loss) (88) (79) (171) (155)
After-tax interest expense $ 78 $ 72 $ 155 $ 142