Investments (Details) - Investment Information, Debt Securities - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021
Investment disclosure details
Fixed maturities, amortized cost	$ 79,027			$ 77,380
Allowance for expected credit losses	4			3
Gross unrealized gains	99			135
Gross unrealized losses	5,910			6,352
Fixed maturities, at fair value	73,212			71,160
Proceeds from sales of fixed maturities classified as available for sale	3,115	$ 2,701
Gross realized gains	19	10
Gross realized losses	51	8
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Investment disclosure details
Fixed maturities, amortized cost	6,420			5,798
Allowance for expected credit losses	0			0
Gross unrealized gains	0			3
Gross unrealized losses	346			363
Fixed maturities, at fair value	6,074			5,438
Obligations of U.S. states, municipalities and political subdivisions [Member]
Investment disclosure details
Fixed maturities, amortized cost	31,814			34,118
Allowance for expected credit losses	0			0
Gross unrealized gains	65			82
Gross unrealized losses	2,450			2,821
Fixed maturities, at fair value	29,429			31,379
Obligations of U.S. states, municipalities and political subdivisions, local general obligation [Member]
Investment disclosure details
Fixed maturities, amortized cost	18,886			19,615
Allowance for expected credit losses	0			0
Gross unrealized gains	33			33
Gross unrealized losses	1,600			1,825
Fixed maturities, at fair value	17,319			17,823
Obligations of U.S. states, municipalities and political subdivisions, revenue [Member]
Investment disclosure details
Fixed maturities, amortized cost	10,141			11,076
Allowance for expected credit losses	0			0
Gross unrealized gains	25			29
Gross unrealized losses	772			907
Fixed maturities, at fair value	9,394			10,198
Obligations of U.S. states, municipalities and political subdivisions, state general obligation [Member]
Investment disclosure details
Fixed maturities, amortized cost	1,194			1,104
Allowance for expected credit losses	0			0
Gross unrealized gains	2			3
Gross unrealized losses	76			88
Fixed maturities, at fair value	1,120			1,019
Obligations of U.S. states, municipalities and political subdivisions, pre-refunded [Member]
Investment disclosure details
Fixed maturities, amortized cost	1,593			2,323
Allowance for expected credit losses	0			0
Gross unrealized gains	5			17
Gross unrealized losses	2			1
Fixed maturities, at fair value	1,596			2,339
Debt securities issued by foreign governments [Member]
Investment disclosure details
Fixed maturities, amortized cost	1,084			1,049
Allowance for expected credit losses	0			0
Gross unrealized gains	0			0
Gross unrealized losses	56			55
Fixed maturities, at fair value	1,028			994
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Investment disclosure details
Fixed maturities, amortized cost	4,463			2,178
Allowance for expected credit losses	0			0
Gross unrealized gains	11			13
Gross unrealized losses	222			200
Fixed maturities, at fair value	4,252			1,991
Corporate and all other bonds [Member]
Investment disclosure details
Fixed maturities, amortized cost	35,246			34,237
Allowance for expected credit losses	4	$ 4	$ 4	3	$ 4	$ 3
Gross unrealized gains	23			37
Gross unrealized losses	2,836			2,913
Fixed maturities, at fair value	$ 32,429			$ 31,358