Investments (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available for Sale Securities
Amortized cost	$ 58,235	$ 59,672
Gross unrealized gains	(3,405)	(3,082)
Gross unrealized losses	(237)	(314)
Fixed income securities:	61,403	62,440
U.S. government and agencies
Schedule of Available for Sale Securities
Amortized cost	3,972	4,192
Gross unrealized gains	(137)	(139)
Gross unrealized losses	(3)	(3)
Fixed income securities:	4,106	4,328
Municipal
Schedule of Available for Sale Securities
Amortized cost	8,043	7,877
Gross unrealized gains	(691)	(645)
Gross unrealized losses	(21)	(25)
Fixed income securities:	8,713	8,497
Corporate
Schedule of Available for Sale Securities
Amortized cost	40,255	40,386
Gross unrealized gains	(2,294)	(1,998)
Gross unrealized losses	(174)	(240)
Fixed income securities:	42,375	42,144
Foreign government
Schedule of Available for Sale Securities
Amortized cost	1,290	1,543
Gross unrealized gains	(85)	(102)
Gross unrealized losses	0	0
Fixed income securities:	1,375	1,645
Asset-backed securities (“ABS”)
Schedule of Available for Sale Securities
Amortized cost	3,047	3,971
Gross unrealized gains	(34)	(38)
Gross unrealized losses	(26)	(31)
Fixed income securities:	3,055	3,978
Residential mortgage-backed securities (“RMBS”)
Schedule of Available for Sale Securities
Amortized cost	1,049	1,108
Gross unrealized gains	(117)	(112)
Gross unrealized losses	(12)	(13)
Fixed income securities:	1,154	1,207
Commercial mortgage-backed securities (“CMBS”)
Schedule of Available for Sale Securities
Amortized cost	558	573
Gross unrealized gains	(43)	(44)
Gross unrealized losses	(1)	(2)
Fixed income securities:	600	615
Redeemable preferred stock
Schedule of Available for Sale Securities
Amortized cost	21	22
Gross unrealized gains	(4)	(4)
Gross unrealized losses	0	0
Fixed income securities:	$ 25	$ 26

This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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