Investments (Details) - Unrealized Losses - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	$ 7,993	$ 48,184
Continuous unrealized loss position, less than 12 months, gross unrealized losses	56	3,860
Continuous unrealized loss position, 12 months or longer, fair value	45,976	11,592
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	4,384	2,492
Continuous unrealized loss position, total, fair value	53,969	59,776
Continuous unrealized loss position, total, gross unrealized losses	4,440	6,352
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	1	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	5	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	53	651
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 12 months	667	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, total	726	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	1,864	2,835
Continuous unrealized loss position, less than 12 months, gross unrealized losses	7	100
Continuous unrealized loss position, 12 months or longer, fair value	2,985	1,679
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	224	263
Continuous unrealized loss position, total, fair value	4,849	4,514
Continuous unrealized loss position, total, gross unrealized losses	231	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	3,868	19,251
Continuous unrealized loss position, less than 12 months, gross unrealized losses	31	1,975
Continuous unrealized loss position, 12 months or longer, fair value	14,351	3,134
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	1,911	846
Continuous unrealized loss position, total, fair value	18,219	22,385
Continuous unrealized loss position, total, gross unrealized losses	1,942	2,821
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	0	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	2	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	31	643
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 12 months	642	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, total	675	1,500
Debt securities issued by foreign governments [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	30	604
Continuous unrealized loss position, less than 12 months, gross unrealized losses	0	22
Continuous unrealized loss position, 12 months or longer, fair value	763	367
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	31	33
Continuous unrealized loss position, total, fair value	793	971
Continuous unrealized loss position, total, gross unrealized losses	31	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	1,215	1,414
Continuous unrealized loss position, less than 12 months, gross unrealized losses	9	128
Continuous unrealized loss position, 12 months or longer, fair value	1,433	316
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	167	72
Continuous unrealized loss position, total, fair value	2,648	1,730
Continuous unrealized loss position, total, gross unrealized losses	176	200
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	0	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	0	52
Corporate and all other bonds [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	1,016	24,080
Continuous unrealized loss position, less than 12 months, gross unrealized losses	9	1,635
Continuous unrealized loss position, 12 months or longer, fair value	26,444	6,096
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	2,051	1,278
Continuous unrealized loss position, total, fair value	27,460	30,176
Continuous unrealized loss position, total, gross unrealized losses	2,060	2,913
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	1	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	3	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	22	8
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 12 months	25	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, total	$ 51	$ 623