Investments, Amortized Cost and Fair Values of Fixed Maturity Securities (Details) - USD ($) $ in Millions	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost	$ 40,342		$ 38,963
Gross unrealized gains	4,847		5,800
Gross unrealized losses	89		77
Allowance for credit loss	31	$ 45	40	$ 47	$ 51	$ 0
Estimated fair value	45,069		44,646
Shadow adjustments	2,200		2,500
Fixed Maturities Available-for-Sale [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost	40,333		38,926
Gross unrealized gains	4,847		5,795
Gross unrealized losses	89		77
Allowance for credit loss	31		40
Estimated fair value	45,060		44,604
Corporate and Other Bonds [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost	21,608		20,792
Gross unrealized gains	2,967		3,578
Gross unrealized losses	42		22
Allowance for credit loss	10	24	23	34	39	0
Estimated fair value	24,523		24,325
States, Municipalities and Political Subdivisions [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost	10,384		9,729
Gross unrealized gains	1,610		1,863
Gross unrealized losses	15
Estimated fair value	11,979		11,592
Asset-Backed [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost	7,669		7,554
Gross unrealized gains	250		320
Gross unrealized losses	26		52
Allowance for credit loss	21	$ 21	17	$ 13	$ 12	$ 0
Estimated fair value	7,872		7,805
Residential Mortgage-Backed [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost	3,176		3,442
Gross unrealized gains	89		146
Gross unrealized losses	6		1
Estimated fair value	3,259		3,587
Commercial Mortgage-Backed [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost	2,064		1,933
Gross unrealized gains	85		93
Gross unrealized losses	16		42
Allowance for credit loss	17		17
Estimated fair value	2,116		1,967
Other Asset-Backed [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost	2,429		2,179
Gross unrealized gains	76		81
Gross unrealized losses	4		9
Allowance for credit loss	4
Estimated fair value	2,497		2,251
U.S. Treasury and Obligations of Government-sponsored Enterprises [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost	139		339
Gross unrealized gains	1		2
Gross unrealized losses	4		3
Estimated fair value	136		338
Foreign Government [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost	521		512
Gross unrealized gains	19		32
Gross unrealized losses	2
Estimated fair value	538		544
Redeemable Preferred Stock [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost	12
Estimated fair value	12
Fixed Maturities Trading [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost	9		37
Gross unrealized gains			5
Estimated fair value	$ 9		$ 42