Investments (Details) - Investment Information, Debt Securities - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022	Dec. 31, 2021
Investment disclosure details
Fixed maturities, amortized cost	$ 80,792			$ 77,380
Allowance for expected credit losses	4			3
Gross unrealized gains	28			135
Gross unrealized losses	8,232			6,352
Fixed maturities, at fair value	72,584			71,160
Proceeds from sales of fixed maturities classified as available for sale	4,619	$ 3,951
Gross realized gains	26	17
Gross realized losses	93	52
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Investment disclosure details
Fixed maturities, amortized cost	6,575			5,798
Allowance for expected credit losses	0			0
Gross unrealized gains	0			3
Gross unrealized losses	363			363
Fixed maturities, at fair value	6,212			5,438
Obligations of U.S. states, municipalities and political subdivisions [Member]
Investment disclosure details
Fixed maturities, amortized cost	30,330			34,118
Allowance for expected credit losses	0			0
Gross unrealized gains	4			82
Gross unrealized losses	4,096			2,821
Fixed maturities, at fair value	26,238			31,379
Obligations of U.S. states, municipalities and political subdivisions, local general obligation [Member]
Investment disclosure details
Fixed maturities, amortized cost	18,358			19,615
Allowance for expected credit losses	0			0
Gross unrealized gains	1			33
Gross unrealized losses	2,675			1,825
Fixed maturities, at fair value	15,684			17,823
Obligations of U.S. states, municipalities and political subdivisions, revenue [Member]
Investment disclosure details
Fixed maturities, amortized cost	9,750			11,076
Allowance for expected credit losses	0			0
Gross unrealized gains	2			29
Gross unrealized losses	1,275			907
Fixed maturities, at fair value	8,477			10,198
Obligations of U.S. states, municipalities and political subdivisions, state general obligation [Member]
Investment disclosure details
Fixed maturities, amortized cost	1,174			1,104
Allowance for expected credit losses	0			0
Gross unrealized gains	0			3
Gross unrealized losses	137			88
Fixed maturities, at fair value	1,037			1,019
Obligations of U.S. states, municipalities and political subdivisions, pre-refunded [Member]
Investment disclosure details
Fixed maturities, amortized cost	1,048			2,323
Allowance for expected credit losses	0			0
Gross unrealized gains	1			17
Gross unrealized losses	9			1
Fixed maturities, at fair value	1,040			2,339
Debt securities issued by foreign governments [Member]
Investment disclosure details
Fixed maturities, amortized cost	1,037			1,049
Allowance for expected credit losses	0			0
Gross unrealized gains	1			0
Gross unrealized losses	56			55
Fixed maturities, at fair value	982			994
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Investment disclosure details
Fixed maturities, amortized cost	6,927			2,178
Allowance for expected credit losses	0			0
Gross unrealized gains	7			13
Gross unrealized losses	411			200
Fixed maturities, at fair value	6,523			1,991
Corporate and all other bonds [Member]
Investment disclosure details
Fixed maturities, amortized cost	35,923			34,237
Allowance for expected credit losses	4	$ 3	$ 4	3	$ 4	$ 3
Gross unrealized gains	16			37
Gross unrealized losses	3,306			2,913
Fixed maturities, at fair value	$ 32,629			$ 31,358