Investment Securities - Schedule of Available-for-Sale Securities (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Investment securities available for sale:
Total Amortized Cost	$ 39,539	$ 38,804
Gross Unrealized Gains	682	578
Gross Unrealized Losses	(129)	(321)
Securities available for sale, at fair value	$ 40,092	$ 39,061
Collateralized by Credit Card Loans \| Other Asset-backed Securities Portfolio
Investment securities available for sale:
Percentage of portfolio	65.00%	71.00%
Auto Dealer Floor Plan Inventory Loans and Leases \| Other Asset-backed Securities Portfolio
Investment securities available for sale:
Percentage of portfolio	16.00%	11.00%
U.S. Treasury securities
Investment securities available for sale:
Total Amortized Cost	$ 4,934	$ 4,664
Gross Unrealized Gains	32	5
Gross Unrealized Losses	0	(9)
Securities available for sale, at fair value	4,966	4,660
RMBS
Investment securities available for sale:
Total Amortized Cost	27,800	27,012
Gross Unrealized Gains	562	533
Gross Unrealized Losses	(94)	(234)
Securities available for sale, at fair value	28,268	27,311
RMBS \| Agency
Investment securities available for sale:
Total Amortized Cost	25,187	24,332
Gross Unrealized Gains	248	165
Gross Unrealized Losses	(68)	(212)
Securities available for sale, at fair value	25,367	24,285
RMBS \| Non-Agency
Investment securities available for sale:
Total Amortized Cost	2,613	2,680
Gross Unrealized Gains	314	368
Gross Unrealized Losses	(26)	(22)
Securities available for sale, at fair value	2,901	3,026
Non-credit OTTI losses related to non-agency RMBS	25	22
CMBS
Investment securities available for sale:
Total Amortized Cost	5,451	5,413
Gross Unrealized Gains	83	37
Gross Unrealized Losses	(30)	(71)
Securities available for sale, at fair value	5,504	5,379
CMBS \| Agency
Investment securities available for sale:
Total Amortized Cost	3,732	3,690
Gross Unrealized Gains	48	21
Gross Unrealized Losses	(25)	(47)
Securities available for sale, at fair value	3,755	3,664
CMBS \| Non-Agency
Investment securities available for sale:
Total Amortized Cost	1,719	1,723
Gross Unrealized Gains	35	16
Gross Unrealized Losses	(5)	(24)
Securities available for sale, at fair value	1,749	1,715
Other ABS
Investment securities available for sale:
Total Amortized Cost	1,037	1,345
Gross Unrealized Gains	2	1
Gross Unrealized Losses	(1)	(6)
Securities available for sale, at fair value	1,038	1,340
Other securities
Investment securities available for sale:
Total Amortized Cost	317	370
Gross Unrealized Gains	3	2
Gross Unrealized Losses	(4)	(1)
Securities available for sale, at fair value	$ 316	$ 371

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

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