Investments (Details) - Unrealized Losses - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	$ 23,954	$ 7,993
Continuous unrealized loss position, less than 12 months, gross unrealized losses	454	56
Continuous unrealized loss position, 12 months or longer, fair value	41,709	45,976
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	4,378	4,384
Continuous unrealized loss position, total, fair value	65,663	53,969
Continuous unrealized loss position, total, gross unrealized losses	4,832	4,440
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	437	1
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost greater than 3 months, 6 months or less	0	5
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 6 months, 12 months or less	43	53
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 12 months	638	667
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, total	1,118	726
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	557	1,864
Continuous unrealized loss position, less than 12 months, gross unrealized losses	1	7
Continuous unrealized loss position, 12 months or longer, fair value	2,830	2,985
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	168	224
Continuous unrealized loss position, total, fair value	3,387	4,849
Continuous unrealized loss position, total, gross unrealized losses	169	231
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	0	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost greater than 3 months, 6 months or less	0	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 6 months, 12 months or less	0	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 12 months	0	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, total	0	0
Obligations of U.S. states, municipalities and political subdivisions [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	8,584	3,868
Continuous unrealized loss position, less than 12 months, gross unrealized losses	160	31
Continuous unrealized loss position, 12 months or longer, fair value	15,007	14,351
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	2,224	1,911
Continuous unrealized loss position, total, fair value	23,591	18,219
Continuous unrealized loss position, total, gross unrealized losses	2,384	1,942
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	366	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost greater than 3 months, 6 months or less	0	2
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 6 months, 12 months or less	43	31
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 12 months	635	642
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, total	1,044	675
Debt securities issued by foreign governments [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	113	30
Continuous unrealized loss position, less than 12 months, gross unrealized losses	1	0
Continuous unrealized loss position, 12 months or longer, fair value	454	763
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	12	31
Continuous unrealized loss position, total, fair value	567	793
Continuous unrealized loss position, total, gross unrealized losses	13	31
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	0	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost greater than 3 months, 6 months or less	0	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 6 months, 12 months or less	0	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 12 months	0	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, total	0	0
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	7,359	1,215
Continuous unrealized loss position, less than 12 months, gross unrealized losses	148	9
Continuous unrealized loss position, 12 months or longer, fair value	1,419	1,433
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	188	167
Continuous unrealized loss position, total, fair value	8,778	2,648
Continuous unrealized loss position, total, gross unrealized losses	336	176
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	58	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost greater than 3 months, 6 months or less	0	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 6 months, 12 months or less	0	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 12 months	0	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, total	58	0
Corporate and all other bonds [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	7,341	1,016
Continuous unrealized loss position, less than 12 months, gross unrealized losses	144	9
Continuous unrealized loss position, 12 months or longer, fair value	21,999	26,444
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	1,786	2,051
Continuous unrealized loss position, total, fair value	29,340	27,460
Continuous unrealized loss position, total, gross unrealized losses	1,930	2,060
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	13	1
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost greater than 3 months, 6 months or less	0	3
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 6 months, 12 months or less	0	22
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 12 months	3	25
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, total	$ 16	$ 51