Investment Securities - Schedule of Available-for-Sale Securities (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Investment securities available for sale:
Total Amortized Cost	$ 38,804	$ 38,859
Gross Unrealized Gains	578	886
Gross Unrealized Losses	(321)	(237)
Securities available for sale, at fair value	$ 39,061	$ 39,508
Collateralized by Credit Card Loans \| Other Asset-backed Securities Portfolio
Investment securities available for sale:
Percentage of portfolio	71.00%	56.00%
Auto Dealer Floor Plan Inventory Loans and Leases \| Other Asset-backed Securities Portfolio
Investment securities available for sale:
Percentage of portfolio	11.00%	16.00%
U.S. Treasury securities
Investment securities available for sale:
Total Amortized Cost	$ 4,664	$ 4,114
Gross Unrealized Gains	5	5
Gross Unrealized Losses	(9)	(1)
Securities available for sale, at fair value	4,660	4,118
Corporate debt securities guaranteed by U.S. government agencies
Investment securities available for sale:
Total Amortized Cost		819
Gross Unrealized Gains		1
Gross Unrealized Losses		(20)
Securities available for sale, at fair value		800
RMBS
Investment securities available for sale:
Total Amortized Cost	27,012	24,742
Gross Unrealized Gains	533	757
Gross Unrealized Losses	(234)	(118)
Securities available for sale, at fair value	27,311	25,381
RMBS \| Agency
Investment securities available for sale:
Total Amortized Cost	24,332	21,804
Gross Unrealized Gains	165	296
Gross Unrealized Losses	(212)	(105)
Securities available for sale, at fair value	24,285	21,995
RMBS \| Non-Agency
Investment securities available for sale:
Total Amortized Cost	2,680	2,938
Gross Unrealized Gains	368	461
Gross Unrealized Losses	(22)	(13)
Securities available for sale, at fair value	3,026	3,386
Non-credit OTTI losses related to non-agency RMBS	22	8
CMBS
Investment securities available for sale:
Total Amortized Cost	5,413	5,531
Gross Unrealized Gains	37	63
Gross Unrealized Losses	(71)	(75)
Securities available for sale, at fair value	5,379	5,519
CMBS \| Agency
Investment securities available for sale:
Total Amortized Cost	3,690	3,751
Gross Unrealized Gains	21	32
Gross Unrealized Losses	(47)	(60)
Securities available for sale, at fair value	3,664	3,723
CMBS \| Non-Agency
Investment securities available for sale:
Total Amortized Cost	1,723	1,780
Gross Unrealized Gains	16	31
Gross Unrealized Losses	(24)	(15)
Securities available for sale, at fair value	1,715	1,796
Other ABS
Investment securities available for sale:
Total Amortized Cost	1,345	2,618
Gross Unrealized Gains	1	54
Gross Unrealized Losses	(6)	(10)
Securities available for sale, at fair value	1,340	2,662
Other securities
Investment securities available for sale:
Total Amortized Cost	370	1,035
Gross Unrealized Gains	2	6
Gross Unrealized Losses	(1)	(13)
Securities available for sale, at fair value	$ 371	$ 1,028

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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