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Investments (Details) - Investment Information, Debt Securities - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Investment disclosure details
Fixed maturities, amortized cost	$ 84,231			$ 81,781
Allowance for expected credit losses	1			5
Gross unrealized gains	181			471
Gross unrealized losses	5,223			4,440
Fixed maturities, at fair value	79,188			77,807
Proceeds from sales of fixed maturities classified as available for sale	1,250	$ 3,115
Gross realized gains	2	19
Gross realized losses	41	51
Realized losses resulting from the early redemption of fixed maturities by the issuer prior to the bonds' maturity date	33	0
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Investment disclosure details
Fixed maturities, amortized cost	6,183			6,591
Allowance for expected credit losses	0			0
Gross unrealized gains	0			8
Gross unrealized losses	243			231
Fixed maturities, at fair value	5,940			6,368
Obligations of U.S. states, municipalities and political subdivisions [Member]
Investment disclosure details
Fixed maturities, amortized cost	29,639			30,294
Allowance for expected credit losses	0			0
Gross unrealized gains	54			154
Gross unrealized losses	2,437			1,942
Fixed maturities, at fair value	27,256			28,506
Obligations of U.S. states, municipalities and political subdivisions, local general obligation [Member]
Investment disclosure details
Fixed maturities, amortized cost	18,280			18,374
Allowance for expected credit losses	0			0
Gross unrealized gains	29			90
Gross unrealized losses	1,619			1,265
Fixed maturities, at fair value	16,690			17,199
Obligations of U.S. states, municipalities and political subdivisions, revenue [Member]
Investment disclosure details
Fixed maturities, amortized cost	9,216			9,748
Allowance for expected credit losses	0			0
Gross unrealized gains	21			52
Gross unrealized losses	736			616
Fixed maturities, at fair value	8,501			9,184
Obligations of U.S. states, municipalities and political subdivisions, state general obligation [Member]
Investment disclosure details
Fixed maturities, amortized cost	1,166			1,209
Allowance for expected credit losses	0			0
Gross unrealized gains	2			7
Gross unrealized losses	78			59
Fixed maturities, at fair value	1,090			1,157
Obligations of U.S. states, municipalities and political subdivisions, pre-refunded [Member]
Investment disclosure details
Fixed maturities, amortized cost	977			963
Allowance for expected credit losses	0			0
Gross unrealized gains	2			5
Gross unrealized losses	4			2
Fixed maturities, at fair value	975			966
Debt securities issued by foreign governments [Member]
Investment disclosure details
Fixed maturities, amortized cost	907			1,035
Allowance for expected credit losses	0			0
Gross unrealized gains	0			2
Gross unrealized losses	27			31
Fixed maturities, at fair value	880			1,006
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Investment disclosure details
Fixed maturities, amortized cost	10,412			7,874
Allowance for expected credit losses	0			0
Gross unrealized gains	51			120
Gross unrealized losses	262			176
Fixed maturities, at fair value	10,201			7,818
Corporate and all other bonds [Member]
Investment disclosure details
Fixed maturities, amortized cost	37,090			35,987
Allowance for expected credit losses	1	$ 4	$ 3	5	$ 4	$ 3
Gross unrealized gains	76			187
Gross unrealized losses	2,254			2,060
Fixed maturities, at fair value	$ 34,911			$ 34,109