Investments (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available for Sale Securities
Amortized cost	$ 59,672	$ 59,008
Gross unrealized gains	3,082	2,475
Gross unrealized losses	(314)	(573)
Fair value	62,440	60,910
U.S. government and agencies
Schedule of Available for Sale Securities
Amortized cost	4,192	2,791
Gross unrealized gains	139	129
Gross unrealized losses	(3)	(7)
Fair value	4,328	2,913
Municipal
Schedule of Available for Sale Securities
Amortized cost	7,877	8,446
Gross unrealized gains	645	364
Gross unrealized losses	(25)	(87)
Fair value	8,497	8,723
Corporate
Schedule of Available for Sale Securities
Amortized cost	40,386	39,331
Gross unrealized gains	1,998	1,659
Gross unrealized losses	(240)	(387)
Fair value	42,144	40,603
Foreign government
Schedule of Available for Sale Securities
Amortized cost	1,543	1,736
Gross unrealized gains	102	99
Gross unrealized losses		(11)
Fair value	1,645	1,824
Asset-backed securities ("ABS")
Schedule of Available for Sale Securities
Amortized cost	3,971	4,491
Gross unrealized gains	38	71
Gross unrealized losses	(31)	(44)
Fair value	3,978	4,518
Residential mortgage-backed securities ("RMBS")
Schedule of Available for Sale Securities
Amortized cost	1,108	1,403
Gross unrealized gains	112	101
Gross unrealized losses	(13)	(30)
Fair value	1,207	1,474
Commercial mortgage-backed securities ("CMBS")
Schedule of Available for Sale Securities
Amortized cost	573	788
Gross unrealized gains	44	48
Gross unrealized losses	(2)	(7)
Fair value	615	829
Redeemable preferred stock
Schedule of Available for Sale Securities
Amortized cost	22	22
Gross unrealized gains	4	4
Fair value	$ 26	$ 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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