Investments (Summary of fixed maturity and equity securities) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	$ 38,019	$ 38,106
Gross Unrealized Gains	3,230	4,126
Gross Unrealized Losses	1,117	45
Estimated Fair Value	40,083	42,187
Total fixed maturity securities trading
Debt securities, amortized cost	38,034	38,126
Debt securities	40,098	42,207
Allowance for Credit Losses	49
Corporate and other bonds
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	20,181	19,789
Gross Unrealized Gains	1,419	2,292
Gross Unrealized Losses	817	32
Estimated Fair Value	20,734	22,049
Unrealized OTTI Losses (Gains)		0
Total fixed maturity securities trading
Debt securities	21,376	22,728
Allowance for Credit Losses	49	0
Asset-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	8,273	8,577
Gross Unrealized Gains	252	260
Gross Unrealized Losses	294	10
Estimated Fair Value	8,231	8,827
Unrealized OTTI Losses (Gains)		(19)
Total fixed maturity securities trading
Debt securities	8,231	8,827
Allowance for Credit Losses	0
States, municipalities and political subdivisions
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	8,957	9,093
Gross Unrealized Gains	1,536	1,559
Gross Unrealized Losses	2	0
Estimated Fair Value	10,491	10,652
Unrealized OTTI Losses (Gains)		0
Total fixed maturity securities trading
Debt securities	10,491	10,652
Allowance for Credit Losses	0
Residential mortgage-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	4,198	4,387
Gross Unrealized Gains	207	133
Gross Unrealized Losses	8	1
Estimated Fair Value	4,397	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	2,207	2,265
Gross Unrealized Gains	36	86
Gross Unrealized Losses	153	5
Estimated Fair Value	2,090	2,346
Unrealized OTTI Losses (Gains)		1
Total fixed maturity securities trading
Allowance for Credit Losses	0
Other asset-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	1,868	1,925
Gross Unrealized Gains	9	41
Gross Unrealized Losses	133	4
Estimated Fair Value	1,744	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	147	146
Gross Unrealized Gains	8	1
Gross Unrealized Losses	0	2
Estimated Fair Value	155	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	452	491
Gross Unrealized Gains	15	14
Gross Unrealized Losses	4	1
Estimated Fair Value	463	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	9	10
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	9	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	38,019	38,106
Gross Unrealized Gains	3,230	4,126
Gross Unrealized Losses	1,117	45
Estimated Fair Value	40,083	42,187
Unrealized OTTI Losses (Gains)		(19)
Total fixed maturity securities trading
Allowance for Credit Losses	49
Fixed Maturities
Total fixed maturity securities trading
Cost or amortized cost, trading securities	15	20
Estimated fair value, trading securities	$ 15	$ 20

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