Investments (Summary of fixed maturity and equity securities) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	$ 38,106	$ 38,081
Gross Unrealized Gains	4,126	1,982
Gross Unrealized Losses	45	521
Estimated Fair Value	42,187	39,542
Total fixed maturity securities trading
Debt securities, amortized cost	38,126	38,085
Debt securities	42,207	39,546
Corporate and other bonds
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	19,789	18,764
Gross Unrealized Gains	2,292	791
Gross Unrealized Losses	32	395
Estimated Fair Value	22,049	19,160
Total fixed maturity securities trading
Debt securities	22,728	19,814
Unrealized OTTI Losses (Gains)	0	0
States, municipalities and political subdivisions
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	9,093	9,681
Gross Unrealized Gains	1,559	1,076
Gross Unrealized Losses	0	9
Estimated Fair Value	10,652	10,748
Total fixed maturity securities trading
Debt securities	10,652	10,748
Unrealized OTTI Losses (Gains)	0	0
Residential mortgage-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	4,387	4,815
Gross Unrealized Gains	133	68
Gross Unrealized Losses	1	57
Estimated Fair Value	4,519	4,826
Total fixed maturity securities trading
Unrealized OTTI Losses (Gains)	(17)	(20)
Commercial mortgage-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	2,265	2,200
Gross Unrealized Gains	86	28
Gross Unrealized Losses	5	32
Estimated Fair Value	2,346	2,196
Total fixed maturity securities trading
Unrealized OTTI Losses (Gains)	1	0
Other asset-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	1,925	1,975
Gross Unrealized Gains	41	11
Gross Unrealized Losses	4	24
Estimated Fair Value	1,962	1,962
Total fixed maturity securities trading
Unrealized OTTI Losses (Gains)	(3)	0
Asset-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	8,577	8,990
Gross Unrealized Gains	260	107
Gross Unrealized Losses	10	113
Estimated Fair Value	8,827	8,984
Total fixed maturity securities trading
Debt securities	8,827	8,984
Unrealized OTTI Losses (Gains)	(19)	(20)
U.S. Treasury and obligations of government-sponsored enterprises
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	146	156
Gross Unrealized Gains	1	3
Gross Unrealized Losses	2	0
Estimated Fair Value	145	159
Total fixed maturity securities trading
Unrealized OTTI Losses (Gains)	0	0
Foreign government
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	491	480
Gross Unrealized Gains	14	5
Gross Unrealized Losses	1	4
Estimated Fair Value	504	481
Total fixed maturity securities trading
Unrealized OTTI Losses (Gains)	0	0
Redeemable preferred stock
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	10	10
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	10	10
Total fixed maturity securities trading
Unrealized OTTI Losses (Gains)	0	0
Fixed maturity securities
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	38,106	38,081
Gross Unrealized Gains	4,126	1,982
Gross Unrealized Losses	45	521
Estimated Fair Value	42,187	39,542
Total fixed maturity securities trading
Unrealized OTTI Losses (Gains)	(19)	(20)
Total fixed maturity securities trading
Total fixed maturity securities trading
Cost or amortized cost, trading securities	20	4
Estimated fair value, trading securities	$ 20	$ 4

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