Investments (Details) - Investment Information, Losses - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	$ 25,625	$ 48,184
Continuous unrealized loss position, less than 12 months, gross unrealized losses	682	3,860
Continuous unrealized loss position, 12 months or longer, fair value	29,350	11,592
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	4,481	2,492
Continuous unrealized loss position, total, fair value	54,975	59,776
Continuous unrealized loss position, total, gross unrealized losses	5,163	6,352
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	253	175
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	2	1,350
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	701	651
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 12 months	185	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, total	1,141	2,176
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	2,056	2,835
Continuous unrealized loss position, less than 12 months, gross unrealized losses	29	100
Continuous unrealized loss position, 12 months or longer, fair value	1,969	1,679
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	254	263
Continuous unrealized loss position, total, fair value	4,025	4,514
Continuous unrealized loss position, total, gross unrealized losses	283	363
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	7,701	19,251
Continuous unrealized loss position, less than 12 months, gross unrealized losses	182	1,975
Continuous unrealized loss position, 12 months or longer, fair value	10,534	3,134
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	2,025	846
Continuous unrealized loss position, total, fair value	18,235	22,385
Continuous unrealized loss position, total, gross unrealized losses	2,207	2,821
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	115	81
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	1	776
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	617	643
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 12 months	185	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, total	918	1,500
Debt securities issued by foreign governments [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	284	604
Continuous unrealized loss position, less than 12 months, gross unrealized losses	3	22
Continuous unrealized loss position, 12 months or longer, fair value	668	367
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	38	33
Continuous unrealized loss position, total, fair value	952	971
Continuous unrealized loss position, total, gross unrealized losses	41	55
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	0	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	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	1
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	875	1,414
Continuous unrealized loss position, less than 12 months, gross unrealized losses	27	128
Continuous unrealized loss position, 12 months or longer, fair value	1,081	316
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	153	72
Continuous unrealized loss position, total, fair value	1,956	1,730
Continuous unrealized loss position, total, gross unrealized losses	180	200
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	35	4
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	48
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	35	52
Corporate and all other bonds [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	14,709	24,080
Continuous unrealized loss position, less than 12 months, gross unrealized losses	441	1,635
Continuous unrealized loss position, 12 months or longer, fair value	15,098	6,096
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	2,011	1,278
Continuous unrealized loss position, total, fair value	29,807	30,176
Continuous unrealized loss position, total, gross unrealized losses	2,452	2,913
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	103	89
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	1	526
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	84	8
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	$ 188	$ 623