Investments - Fair Values and Unrealized Losses by Investment Category and by Duration of Securities' Continuous Unrealized Loss Position (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Investments, Unrealized Loss Position
Less than 12 months Fair Value	$ 12,759	$ 2,206
Less than 12 Months, Unrealized Loss	786	22
12 months or more, Fair Value	4,824	5,671
12 months or longer, Unrealized Loss	727	375
Total Fair Value	17,583	7,877
Total Unrealized Losses	1,513	397
Short-term investments, available-for-sale, continuous unrealized loss position, less than 12 months	141
Short-term Investments, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3
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	141
Short-term investments, available-for-sale, unrealized loss position, accumulated loss	3
Investments, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months	12,900
Investments, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	789
Investments, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer	4,824
Investments, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	727
Investments, Available-for-Sale, Unrealized Loss Position	17,724
Investments, Available-for-Sale, Unrealized Loss Position, Accumulated Loss	1,516
Corporate
Investments, Unrealized Loss Position
Less than 12 months Fair Value	6,972	849
Less than 12 Months, Unrealized Loss	355	15
12 months or more, Fair Value	2,473	2,926
12 months or longer, Unrealized Loss	321	188
Total Fair Value	9,445	3,775
Total Unrealized Losses	676	203
States, municipalities and political subdivisions
Investments, Unrealized Loss Position
Less than 12 months Fair Value	2,436	204
Less than 12 Months, Unrealized Loss	147	2
12 months or more, Fair Value	1,852	2,346
12 months or longer, Unrealized Loss	360	179
Total Fair Value	4,288	2,550
Total Unrealized Losses	507	181
Government-sponsored enterprises
Investments, Unrealized Loss Position
Less than 12 months Fair Value	2,397	983
Less than 12 Months, Unrealized Loss	242	3
12 months or more, Fair Value	283	195
12 months or longer, Unrealized Loss	26	1
Total Fair Value	2,680	1,178
Total Unrealized Losses	268	4
Asset-backed
Investments, Unrealized Loss Position
Less than 12 months Fair Value	642	101
Less than 12 Months, Unrealized Loss	28	2
12 months or more, Fair Value	198	184
12 months or longer, Unrealized Loss	19	6
Total Fair Value	840	285
Total Unrealized Losses	47	8
United States government
Investments, Unrealized Loss Position
Less than 12 months Fair Value	293	69
Less than 12 Months, Unrealized Loss	14	0
12 months or more, Fair Value	18	20
12 months or longer, Unrealized Loss	1	1
Total Fair Value	311	89
Total Unrealized Losses	15	1
Foreign government
Investments, Unrealized Loss Position
Less than 12 months Fair Value	19
Less than 12 Months, Unrealized Loss	0
12 months or more, Fair Value	0
12 months or longer, Unrealized Loss	0
Total Fair Value	19
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.