Investments (Details) - Unrealized Losses - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	$ 14,495	$ 1,045
Continuous unrealized loss position, less than 12 months, gross unrealized losses	266	8
Continuous unrealized loss position, 12 months or longer, fair value	602	98
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	28	3
Continuous unrealized loss position, total, fair value	15,097	1,143
Continuous unrealized loss position, total, gross unrealized losses	294	11
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, total	0
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	2,438	92
Continuous unrealized loss position, less than 12 months, gross unrealized losses	32	0
Continuous unrealized loss position, 12 months or longer, fair value	5	0
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	0	0
Continuous unrealized loss position, total, fair value	2,443	92
Continuous unrealized loss position, total, gross unrealized losses	32	0
Obligations of states, municipalities and political subdivisions [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	3,873	245
Continuous unrealized loss position, less than 12 months, gross unrealized losses	69	2
Continuous unrealized loss position, 12 months or longer, fair value	153	0
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	6	0
Continuous unrealized loss position, total, fair value	4,026	245
Continuous unrealized loss position, total, gross unrealized losses	75	2
Debt securities issued by foreign governments [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	452	7
Continuous unrealized loss position, less than 12 months, gross unrealized losses	7	0
Continuous unrealized loss position, 12 months or longer, fair value	7	0
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	0	0
Continuous unrealized loss position, total, fair value	459	7
Continuous unrealized loss position, total, gross unrealized losses	7	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	426	20
Continuous unrealized loss position, less than 12 months, gross unrealized losses	5	0
Continuous unrealized loss position, 12 months or longer, fair value	1	1
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	0	0
Continuous unrealized loss position, total, fair value	427	21
Continuous unrealized loss position, total, gross unrealized losses	5	0
All other corporate bonds [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	7,306	681
Continuous unrealized loss position, less than 12 months, gross unrealized losses	153	6
Continuous unrealized loss position, 12 months or longer, fair value	436	97
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	22	3
Continuous unrealized loss position, total, fair value	7,742	778
Continuous unrealized loss position, total, gross unrealized losses	$ 175	$ 9