Investments - Fair Values and Unrealized Losses by Investment Category and by Duration of Securities' Continuous Unrealized Loss Position (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Investments, Unrealized Loss Position
Less than 12 months Fair Value	$ 6,154	$ 2,206
Less than 12 Months, Unrealized Loss	88	22
12 months or more, Fair Value	5,040	5,671
12 months or longer, Unrealized Loss	390	375
Total Fair Value	11,194	7,877
Total Unrealized Losses	478	397
Short-term investments, available-for-sale, continuous unrealized loss position, less than 12 months	142
Short-term Investments, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1
Short-term investments, available-for-sale, continuous unrealized loss position, 12 months or longer	0
Short-term investments, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	0
Short-term investments, available-for-sale, unrealized loss position, total	142
Short-term investments, available-for-sale, unrealized loss position, accumulated loss	1
Investments, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months	6,296
Investments, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	89
Investments, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer	5,040
Investments, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	390
Investments, Available-for-Sale, Unrealized Loss Position	11,336
Investments, Available-for-Sale, Unrealized Loss Position, Accumulated Loss	479
Corporate
Investments, Unrealized Loss Position
Less than 12 months Fair Value	3,194	849
Less than 12 Months, Unrealized Loss	42	15
12 months or more, Fair Value	2,580	2,926
12 months or longer, Unrealized Loss	199	188
Total Fair Value	5,774	3,775
Total Unrealized Losses	241	203
States, municipalities and political subdivisions
Investments, Unrealized Loss Position
Less than 12 months Fair Value	316	204
Less than 12 Months, Unrealized Loss	2	2
12 months or more, Fair Value	2,063	2,346
12 months or longer, Unrealized Loss	180	179
Total Fair Value	2,379	2,550
Total Unrealized Losses	182	181
Government-sponsored enterprises
Investments, Unrealized Loss Position
Less than 12 months Fair Value	2,152	983
Less than 12 Months, Unrealized Loss	38	3
12 months or more, Fair Value	193	195
12 months or longer, Unrealized Loss	3	1
Total Fair Value	2,345	1,178
Total Unrealized Losses	41	4
Asset-backed
Investments, Unrealized Loss Position
Less than 12 months Fair Value	202	101
Less than 12 Months, Unrealized Loss	3	2
12 months or more, Fair Value	184	184
12 months or longer, Unrealized Loss	7	6
Total Fair Value	386	285
Total Unrealized Losses	10	8
United States government
Investments, Unrealized Loss Position
Less than 12 months Fair Value	276	69
Less than 12 Months, Unrealized Loss	3	0
12 months or more, Fair Value	20	20
12 months or longer, Unrealized Loss	1	1
Total Fair Value	296	89
Total Unrealized Losses	4	1
Foreign government
Investments, Unrealized Loss Position
Less than 12 months Fair Value	14
Less than 12 Months, Unrealized Loss	0
12 months or more, Fair Value	0
12 months or longer, Unrealized Loss	0
Total Fair Value	14
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.