Investments - Fair Values and Unrealized Losses by Investment Category and by Duration of Securities' Continuous Unrealized Loss Position (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Investments, Unrealized Loss Position
Investments, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 5,007	$ 6,683
Investments, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	116	121
Investments, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer	5,363	5,823
Investments, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	466	510
Investments, Available-for-Sale, Unrealized Loss Position	10,370	12,506
Investments, Available-for-Sale, Unrealized Loss Position, Accumulated Loss	582	631
Short-term investments, available-for-sale, continuous unrealized loss position, less than 12 months	100	100
Short-term Investments, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Short-term investments, available-for-sale, continuous unrealized loss position, 12 months or longer	0	0
Short-term investments, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	0	0
Short-term investments, available-for-sale, unrealized loss position, total	100	100
Short-term investments, available-for-sale, unrealized loss position, accumulated loss	0	0
Less than 12 months Fair Value	4,907	6,583
Less than 12 Months, Unrealized Loss	116	121
12 months or more, Fair Value	5,363	5,823
12 months or longer, Unrealized Loss	466	510
Total Fair Value	10,270	12,406
Total Unrealized Losses	582	631
Corporate
Investments, Unrealized Loss Position
Less than 12 months Fair Value	1,738	2,815
Less than 12 Months, Unrealized Loss	51	78
12 months or more, Fair Value	3,037	3,634
12 months or longer, Unrealized Loss	205	255
Total Fair Value	4,775	6,449
Total Unrealized Losses	256	333
States, municipalities and political subdivisions
Investments, Unrealized Loss Position
Less than 12 months Fair Value	1,505	1,513
Less than 12 Months, Unrealized Loss	49	25
12 months or more, Fair Value	2,062	1,898
12 months or longer, Unrealized Loss	255	245
Total Fair Value	3,567	3,411
Total Unrealized Losses	304	270
Government-sponsored enterprises
Investments, Unrealized Loss Position
Less than 12 months Fair Value	1,427	1,876
Less than 12 Months, Unrealized Loss	9	8
12 months or more, Fair Value	124	92
12 months or longer, Unrealized Loss	0	1
Total Fair Value	1,551	1,968
Total Unrealized Losses	9	9
Asset-backed
Investments, Unrealized Loss Position
Less than 12 months Fair Value	237	331
Less than 12 Months, Unrealized Loss	7	10
12 months or more, Fair Value	78	96
12 months or longer, Unrealized Loss	5	7
Total Fair Value	315	427
Total Unrealized Losses	12	17
United States government
Investments, Unrealized Loss Position
Less than 12 months Fair Value	0	48
Less than 12 Months, Unrealized Loss	0	0
12 months or more, Fair Value	62	100
12 months or longer, Unrealized Loss	1	2
Total Fair Value	62	148
Total Unrealized Losses	1	2
Foreign government
Investments, Unrealized Loss Position
Less than 12 months Fair Value	0	0
Less than 12 Months, Unrealized Loss	0	0
12 months or more, Fair Value	0	3
12 months or longer, Unrealized Loss	0	0
Total Fair Value	0	3
Total Unrealized Losses	$ 0	$ 0

Amount of investment in available for sale security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset

No definition available.