Investments (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available for Sale Securities
Amortized cost	$ 57,201	$ 59,672
Gross unrealized gains	(1,707)	(3,082)
Gross unrealized losses	(960)	(314)
Fair value	57,948	62,440
U.S. government and agencies
Schedule of Available for Sale Securities
Amortized cost	3,836	4,192
Gross unrealized gains	(90)	(139)
Gross unrealized losses	(4)	(3)
Fair value	3,922	4,328
Municipal
Schedule of Available for Sale Securities
Amortized cost	7,032	7,877
Gross unrealized gains	(389)	(645)
Gross unrealized losses	(20)	(25)
Fair value	7,401	8,497
Corporate
Schedule of Available for Sale Securities
Amortized cost	41,674	40,386
Gross unrealized gains	(1,032)	(1,998)
Gross unrealized losses	(879)	(240)
Fair value	41,827	42,144
Foreign government
Schedule of Available for Sale Securities
Amortized cost	983	1,543
Gross unrealized gains	(50)	(102)
Gross unrealized losses	0	0
Fair value	1,033	1,645
ABS
Schedule of Available for Sale Securities
Amortized cost	2,359	3,971
Gross unrealized gains	(11)	(38)
Gross unrealized losses	(43)	(31)
Fair value	2,327	3,978
RMBS
Schedule of Available for Sale Securities
Amortized cost	857	1,108
Gross unrealized gains	(100)	(112)
Gross unrealized losses	(10)	(13)
Fair value	947	1,207
CMBS
Schedule of Available for Sale Securities
Amortized cost	438	573
Gross unrealized gains	(32)	(44)
Gross unrealized losses	(4)	(2)
Fair value	466	615
Redeemable preferred stock
Schedule of Available for Sale Securities
Amortized cost	22	22
Gross unrealized gains	(3)	(4)
Gross unrealized losses	0	0
Fair value	$ 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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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