Investments, Amortized Cost and Fair Values of Fixed Maturity Securities (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Sep. 30, 2020		Jun. 30, 2020
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		$ 38,157	$ 38,979
Gross unrealized gains		4,128	5,166
Gross unrealized losses		45	181
Allowance for credit loss		0	47	[1]	$ 51
Estimated fair value		42,240	43,917
Unrealized OTTI losses (gains)	[1]	(19)
Shadow adjustments		2,000	2,300
Fixed Maturities Available-for-Sale [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		38,106	38,962
Gross unrealized gains		4,126	5,160
Gross unrealized losses		45	181
Allowance for credit loss	[1]		47
Estimated fair value		42,187	43,894
Unrealized OTTI losses (gains)	[1]	(19)
Corporate and Other Bonds [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		19,789	20,734
Gross unrealized gains		2,292	3,047
Gross unrealized losses		32	89
Allowance for credit loss		0	34	[1]	39
Estimated fair value		22,049	23,658
States, Municipalities and Political Subdivisions [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		9,093	9,459
Gross unrealized gains		1,559	1,766
Gross unrealized losses			1
Estimated fair value		10,652	11,224
Asset-Backed [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		8,577	7,941
Gross unrealized gains		260	314
Gross unrealized losses		10	90
Allowance for credit loss		0	13	[1]	$ 12
Estimated fair value		8,827	8,152
Unrealized OTTI losses (gains)	[1]	(19)
Residential Mortgage-Backed [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		4,387	3,796
Gross unrealized gains		133	153
Gross unrealized losses		1	1
Estimated fair value		4,519	3,948
Unrealized OTTI losses (gains)	[1]	(17)
Commercial Mortgage-Backed [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		2,265	2,048
Gross unrealized gains		86	85
Gross unrealized losses		5	70
Allowance for credit loss	[1]		13
Estimated fair value		2,346	2,050
Unrealized OTTI losses (gains)	[1]	1
Other Asset-Backed [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		1,925	2,097
Gross unrealized gains		41	76
Gross unrealized losses		4	19
Estimated fair value		1,962	2,154
Unrealized OTTI losses (gains)	[1]	(3)
U.S. Treasury and Obligations of Government-sponsored Enterprises [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		146	347
Gross unrealized gains		1	4
Gross unrealized losses		2	1
Estimated fair value		145	350
Foreign Government [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		491	481
Gross unrealized gains		14	29
Gross unrealized losses		1
Estimated fair value		504	510
Redeemable Preferred Stock [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		10
Estimated fair value		10
Fixed Maturities Trading [Member]
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or amortized cost		51	17
Gross unrealized gains		2	6
Estimated fair value		$ 53	$ 23

[1] On January 1, 2020, the Company adopted ASU 2016-13; see Note 1. The Unrealized OTTI Losses (Gains) column that tracked subsequent valuation changes on securities for which a credit loss had previously been recorded has been replaced with the Allowance for Credit Losses column. Prior period amounts were not adjusted for the adoption of this standard.