Investments (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available for Sale Securities
Amortized cost	$ 56,576	$ 57,201
Gross unrealized gains	1,710	1,707
Gross unrealized losses	(447)	(960)
Fair value	57,839	57,948
U.S. government and agencies
Schedule of Available for Sale Securities
Amortized cost	3,572	3,836
Gross unrealized gains	74	90
Gross unrealized losses	(9)	(4)
Fair value	3,637	3,922
Municipal
Schedule of Available for Sale Securities
Amortized cost	7,116	7,032
Gross unrealized gains	304	389
Gross unrealized losses	(87)	(20)
Fair value	7,333	7,401
Corporate
Schedule of Available for Sale Securities
Amortized cost	42,742	41,674
Gross unrealized gains	1,178	1,032
Gross unrealized losses	(319)	(879)
Fair value	43,601	41,827
Foreign government
Schedule of Available for Sale Securities
Amortized cost	1,043	983
Gross unrealized gains	36	50
Gross unrealized losses	(4)	0
Fair value	1,075	1,033
ABS
Schedule of Available for Sale Securities
Amortized cost	1,169	2,359
Gross unrealized gains	13	11
Gross unrealized losses	(11)	(43)
Fair value	1,171	2,327
RMBS
Schedule of Available for Sale Securities
Amortized cost	651	857
Gross unrealized gains	85	100
Gross unrealized losses	(8)	(10)
Fair value	728	947
CMBS
Schedule of Available for Sale Securities
Amortized cost	262	438
Gross unrealized gains	17	32
Gross unrealized losses	(9)	(4)
Fair value	270	466
Redeemable preferred stock
Schedule of Available for Sale Securities
Amortized cost	21	22
Gross unrealized gains	3	3
Gross unrealized losses	0	0
Fair value	$ 24	$ 25

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
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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