Investment Securities - Schedule of Available-for-Sale Securities (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Investment securities available for sale:
Total Amortized Cost	$ 40,733	$ 38,804
Gross Unrealized Gains	539	578
Gross Unrealized Losses	(535)	(321)
Securities available for sale, at fair value	$ 40,737	$ 39,061
Collateralized Credit Card Securities [Member] \| Other Asset-backed Securities Portfolio
Investment securities available for sale:
Percentage of portfolio	57.00%	71.00%
Auto Dealer Floor Plan Inventory Loans and Leases \| Other Asset-backed Securities Portfolio
Investment securities available for sale:
Percentage of portfolio	23.00%	11.00%
U.S. Treasury securities
Investment securities available for sale:
Total Amortized Cost	$ 5,103	$ 4,664
Gross Unrealized Gains	11	5
Gross Unrealized Losses	(49)	(9)
Securities available for sale, at fair value	5,065	4,660
RMBS
Investment securities available for sale:
Total Amortized Cost	29,179	27,012
Gross Unrealized Gains	491	533
Gross Unrealized Losses	(421)	(234)
Securities available for sale, at fair value	29,249	27,311
RMBS \| Agency
Investment securities available for sale:
Total Amortized Cost	26,830	24,332
Gross Unrealized Gains	109	165
Gross Unrealized Losses	(412)	(212)
Securities available for sale, at fair value	26,527	24,285
RMBS \| Non-Agency
Investment securities available for sale:
Total Amortized Cost	2,349	2,680
Gross Unrealized Gains	382	368
Gross Unrealized Losses	(9)	(22)
Securities available for sale, at fair value	2,722	3,026
Non-credit OTTI losses related to non-agency RMBS	9	22
CMBS
Investment securities available for sale:
Total Amortized Cost	5,011	5,413
Gross Unrealized Gains	35	37
Gross Unrealized Losses	(58)	(71)
Securities available for sale, at fair value	4,988	5,379
CMBS \| Agency
Investment securities available for sale:
Total Amortized Cost	3,335	3,690
Gross Unrealized Gains	14	21
Gross Unrealized Losses	(45)	(47)
Securities available for sale, at fair value	3,304	3,664
CMBS \| Non-Agency
Investment securities available for sale:
Total Amortized Cost	1,676	1,723
Gross Unrealized Gains	21	16
Gross Unrealized Losses	(13)	(24)
Securities available for sale, at fair value	1,684	1,715
Other ABS
Investment securities available for sale:
Total Amortized Cost	714	1,345
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(1)	(6)
Securities available for sale, at fair value	714	1,340
Other securities
Investment securities available for sale:
Total Amortized Cost	726	370
Gross Unrealized Gains	1	2
Gross Unrealized Losses	(6)	(1)
Securities available for sale, at fair value	$ 721	$ 371

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

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