Investments (Summary of fixed maturity and equity securities) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	$ 38,962		$ 38,106
Gross Unrealized Gains	5,160		4,126
Gross Unrealized Losses	181		45
Estimated Fair Value	43,894		42,187
Total fixed maturity securities trading
Debt securities, amortized cost	38,969		38,126
Debt securities	43,901		42,207
Allowance for Credit Losses	47	$ 51	0
Corporate and other bonds
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	20,734		19,789
Gross Unrealized Gains	3,047		2,292
Gross Unrealized Losses	89		32
Estimated Fair Value	23,658		22,049
Unrealized OTTI Losses (Gains)			0
Total fixed maturity securities trading
Debt securities	24,525		22,728
Allowance for Credit Losses	34	39	0
Asset-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	7,941		8,577
Gross Unrealized Gains	314		260
Gross Unrealized Losses	90		10
Estimated Fair Value	8,152		8,827
Unrealized OTTI Losses (Gains)			(19)
Total fixed maturity securities trading
Debt securities	8,152		8,827
Allowance for Credit Losses	13	$ 12	0
States, municipalities and political subdivisions
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	9,459		9,093
Gross Unrealized Gains	1,766		1,559
Gross Unrealized Losses	1		0
Estimated Fair Value	11,224		10,652
Unrealized OTTI Losses (Gains)			0
Total fixed maturity securities trading
Debt securities	11,224		10,652
Allowance for Credit Losses	0
Residential mortgage-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	3,796		4,387
Gross Unrealized Gains	153		133
Gross Unrealized Losses	1		1
Estimated Fair Value	3,948		4,519
Unrealized OTTI Losses (Gains)			(17)
Total fixed maturity securities trading
Allowance for Credit Losses	0
Commercial mortgage-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	2,048		2,265
Gross Unrealized Gains	85		86
Gross Unrealized Losses	70		5
Estimated Fair Value	2,050		2,346
Unrealized OTTI Losses (Gains)			1
Total fixed maturity securities trading
Allowance for Credit Losses	13
Other asset-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	2,097		1,925
Gross Unrealized Gains	76		41
Gross Unrealized Losses	19		4
Estimated Fair Value	2,154		1,962
Unrealized OTTI Losses (Gains)			(3)
Total fixed maturity securities trading
Allowance for Credit Losses	0
U.S. Treasury and obligations of government-sponsored enterprises
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	347		146
Gross Unrealized Gains	4		1
Gross Unrealized Losses	1		2
Estimated Fair Value	350		145
Unrealized OTTI Losses (Gains)			0
Total fixed maturity securities trading
Allowance for Credit Losses	0
Foreign government
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	481		491
Gross Unrealized Gains	29		14
Gross Unrealized Losses	0		1
Estimated Fair Value	510		504
Unrealized OTTI Losses (Gains)			0
Total fixed maturity securities trading
Allowance for Credit Losses	0
Redeemable preferred stock
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	0		10
Gross Unrealized Gains	0		0
Gross Unrealized Losses	0		0
Estimated Fair Value	0		10
Unrealized OTTI Losses (Gains)			0
Total fixed maturity securities trading
Allowance for Credit Losses	0
Fixed maturity securities
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	38,962		38,106
Gross Unrealized Gains	5,160		4,126
Gross Unrealized Losses	181		45
Estimated Fair Value	43,894		42,187
Unrealized OTTI Losses (Gains)			(19)
Total fixed maturity securities trading
Allowance for Credit Losses	47
Total fixed maturity securities trading
Total fixed maturity securities trading
Cost or amortized cost, trading securities	7		20
Estimated fair value, trading securities	$ 7		$ 20

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