Investments (Details) - Investment Information, Debt Securities - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022	Dec. 31, 2021
Investment disclosure details
Fixed maturities, amortized cost	$ 77,827		$ 77,380
Allowance for expected credit losses	4		3
Gross unrealized gains	254		135
Gross unrealized losses	5,163		6,352
Fixed maturities, at fair value	72,914		71,160
Proceeds from sales of fixed maturities classified as available for sale	2,364	$ 1,044
Gross realized gains	17	5
Gross realized losses	27	2
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Investment disclosure details
Fixed maturities, amortized cost	6,617		5,798
Allowance for expected credit losses	0		0
Gross unrealized gains	18		3
Gross unrealized losses	283		363
Fixed maturities, at fair value	6,352		5,438
Obligations of U.S. states, municipalities and political subdivisions [Member]
Investment disclosure details
Fixed maturities, amortized cost	32,095		34,118
Allowance for expected credit losses	0		0
Gross unrealized gains	145		82
Gross unrealized losses	2,207		2,821
Fixed maturities, at fair value	30,033		31,379
Obligations of U.S. states, municipalities and political subdivisions, local general obligation [Member]
Investment disclosure details
Fixed maturities, amortized cost	18,866		19,615
Allowance for expected credit losses	0		0
Gross unrealized gains	74		33
Gross unrealized losses	1,430		1,825
Fixed maturities, at fair value	17,510		17,823
Obligations of U.S. states, municipalities and political subdivisions, revenue [Member]
Investment disclosure details
Fixed maturities, amortized cost	10,321		11,076
Allowance for expected credit losses	0		0
Gross unrealized gains	51		29
Gross unrealized losses	709		907
Fixed maturities, at fair value	9,663		10,198
Obligations of U.S. states, municipalities and political subdivisions, state general obligation [Member]
Investment disclosure details
Fixed maturities, amortized cost	1,198		1,104
Allowance for expected credit losses	0		0
Gross unrealized gains	5		3
Gross unrealized losses	68		88
Fixed maturities, at fair value	1,135		1,019
Obligations of U.S. states, municipalities and political subdivisions, pre-refunded [Member]
Investment disclosure details
Fixed maturities, amortized cost	1,710		2,323
Allowance for expected credit losses	0		0
Gross unrealized gains	15		17
Gross unrealized losses	0		1
Fixed maturities, at fair value	1,725		2,339
Debt securities issued by foreign governments [Member]
Investment disclosure details
Fixed maturities, amortized cost	1,051		1,049
Allowance for expected credit losses	0		0
Gross unrealized gains	0		0
Gross unrealized losses	41		55
Fixed maturities, at fair value	1,010		994
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Investment disclosure details
Fixed maturities, amortized cost	3,024		2,178
Allowance for expected credit losses	0		0
Gross unrealized gains	20		13
Gross unrealized losses	180		200
Fixed maturities, at fair value	2,864		1,991
Corporate and all other bonds [Member]
Investment disclosure details
Fixed maturities, amortized cost	35,040		34,237
Allowance for expected credit losses	4	$ 4	3	$ 3
Gross unrealized gains	71		37
Gross unrealized losses	2,452		2,913
Fixed maturities, at fair value	$ 32,655		$ 31,358

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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