Investments (Details) - Investment Information, Losses - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	$ 25,942	$ 48,184
Continuous unrealized loss position, less than 12 months, gross unrealized losses	1,070	3,860
Continuous unrealized loss position, 12 months or longer, fair value	44,884	11,592
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	7,162	2,492
Continuous unrealized loss position, total, fair value	70,826	59,776
Continuous unrealized loss position, total, gross unrealized losses	8,232	6,352
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	1,833	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	468	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	185	651
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 12 months	1,090	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, total	3,576	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	2,979	2,835
Continuous unrealized loss position, less than 12 months, gross unrealized losses	32	100
Continuous unrealized loss position, 12 months or longer, fair value	3,083	1,679
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	331	263
Continuous unrealized loss position, total, fair value	6,062	4,514
Continuous unrealized loss position, total, gross unrealized losses	363	363
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	17	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	17	0
Obligations of U.S. states, municipalities and political subdivisions [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	12,050	19,251
Continuous unrealized loss position, less than 12 months, gross unrealized losses	703	1,975
Continuous unrealized loss position, 12 months or longer, fair value	13,625	3,134
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	3,393	846
Continuous unrealized loss position, total, fair value	25,675	22,385
Continuous unrealized loss position, total, gross unrealized losses	4,096	2,821
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	948	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	167	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	140	643
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 12 months	1,024	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, total	2,279	1,500
Debt securities issued by foreign governments [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	201	604
Continuous unrealized loss position, less than 12 months, gross unrealized losses	6	22
Continuous unrealized loss position, 12 months or longer, fair value	769	367
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	50	33
Continuous unrealized loss position, total, fair value	970	971
Continuous unrealized loss position, total, gross unrealized losses	56	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	1	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	1	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	5,032	1,414
Continuous unrealized loss position, less than 12 months, gross unrealized losses	162	128
Continuous unrealized loss position, 12 months or longer, fair value	1,373	316
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	249	72
Continuous unrealized loss position, total, fair value	6,405	1,730
Continuous unrealized loss position, total, gross unrealized losses	411	200
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	46	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	54	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	100	52
Corporate and all other bonds [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	5,680	24,080
Continuous unrealized loss position, less than 12 months, gross unrealized losses	167	1,635
Continuous unrealized loss position, 12 months or longer, fair value	26,034	6,096
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	3,139	1,278
Continuous unrealized loss position, total, fair value	31,714	30,176
Continuous unrealized loss position, total, gross unrealized losses	3,306	2,913
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	822	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	246	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	45	8
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 12 months	66	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, total	$ 1,179	$ 623