Investments (Details) - Investment Information, Losses - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	$ 27,046	$ 48,184
Continuous unrealized loss position, less than 12 months, gross unrealized losses	590	3,860
Continuous unrealized loss position, 12 months or longer, fair value	37,554	11,592
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	5,320	2,492
Continuous unrealized loss position, total, fair value	64,600	59,776
Continuous unrealized loss position, total, gross unrealized losses	5,910	6,352
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	478	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	150	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	280	651
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 12 months	591	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, total	1,499	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	4,119	2,835
Continuous unrealized loss position, less than 12 months, gross unrealized losses	76	100
Continuous unrealized loss position, 12 months or longer, fair value	1,900	1,679
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	270	263
Continuous unrealized loss position, total, fair value	6,019	4,514
Continuous unrealized loss position, total, gross unrealized losses	346	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	9,891	19,251
Continuous unrealized loss position, less than 12 months, gross unrealized losses	146	1,975
Continuous unrealized loss position, 12 months or longer, fair value	13,014	3,134
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	2,304	846
Continuous unrealized loss position, total, fair value	22,905	22,385
Continuous unrealized loss position, total, gross unrealized losses	2,450	2,821
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	160	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	105	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	223	643
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 12 months	586	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, total	1,074	1,500
Debt securities issued by foreign governments [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	234	604
Continuous unrealized loss position, less than 12 months, gross unrealized losses	6	22
Continuous unrealized loss position, 12 months or longer, fair value	781	367
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	50	33
Continuous unrealized loss position, total, fair value	1,015	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	2	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	2	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	2,686	1,414
Continuous unrealized loss position, less than 12 months, gross unrealized losses	47	128
Continuous unrealized loss position, 12 months or longer, fair value	1,161	316
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	175	72
Continuous unrealized loss position, total, fair value	3,847	1,730
Continuous unrealized loss position, total, gross unrealized losses	222	200
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	44	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	44	52
Corporate and all other bonds [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	10,116	24,080
Continuous unrealized loss position, less than 12 months, gross unrealized losses	315	1,635
Continuous unrealized loss position, 12 months or longer, fair value	20,698	6,096
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	2,521	1,278
Continuous unrealized loss position, total, fair value	30,814	30,176
Continuous unrealized loss position, total, gross unrealized losses	2,836	2,913
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, 3 months or less	272	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	45	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	57	8
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, greater than 12 months	5	0
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, total	$ 379	$ 623