Investments (Summary of fixed maturity and equity securities) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	$ 38,387		$ 38,106
Gross Unrealized Gains	4,706		4,126
Gross Unrealized Losses	272		45
Estimated Fair Value	42,770		42,187
Total fixed maturity securities trading
Debt securities, amortized cost	38,392		38,126
Debt securities	42,775		42,207
Allowance for Credit Losses	51	$ 49	0
Corporate and other bonds
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	20,305		19,789
Gross Unrealized Gains	2,680		2,292
Gross Unrealized Losses	143		32
Estimated Fair Value	22,803		22,049
Unrealized OTTI Losses (Gains)			0
Total fixed maturity securities trading
Debt securities	23,789		22,728
Allowance for Credit Losses	39	49	0
Asset-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	7,708		8,577
Gross Unrealized Gains	291		260
Gross Unrealized Losses	128		10
Estimated Fair Value	7,859		8,827
Unrealized OTTI Losses (Gains)			(19)
Total fixed maturity securities trading
Debt securities	7,859		8,827
Allowance for Credit Losses	12	$ 0	0
States, municipalities and political subdivisions
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	9,426		9,093
Gross Unrealized Gains	1,702		1,559
Gross Unrealized Losses	1		0
Estimated Fair Value	11,127		10,652
Unrealized OTTI Losses (Gains)			0
Total fixed maturity securities trading
Debt securities	11,127		10,652
Allowance for Credit Losses	0
Residential mortgage-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	3,617		4,387
Gross Unrealized Gains	169		133
Gross Unrealized Losses	2		1
Estimated Fair Value	3,784		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	2,151		2,265
Gross Unrealized Gains	70		86
Gross Unrealized Losses	93		5
Estimated Fair Value	2,116		2,346
Unrealized OTTI Losses (Gains)			1
Total fixed maturity securities trading
Allowance for Credit Losses	12
Other asset-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	1,940		1,925
Gross Unrealized Gains	52		41
Gross Unrealized Losses	33		4
Estimated Fair Value	1,959		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	491		146
Gross Unrealized Gains	7		1
Gross Unrealized Losses	0		2
Estimated Fair Value	498		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	457		491
Gross Unrealized Gains	26		14
Gross Unrealized Losses	0		1
Estimated Fair Value	483		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	38,387		38,106
Gross Unrealized Gains	4,706		4,126
Gross Unrealized Losses	272		45
Estimated Fair Value	42,770		42,187
Unrealized OTTI Losses (Gains)			(19)
Total fixed maturity securities trading
Allowance for Credit Losses	51
Total fixed maturity securities trading
Total fixed maturity securities trading
Cost or amortized cost, trading securities	5		20
Estimated fair value, trading securities	$ 5		$ 20

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