Investment Securities - Schedule of Available-for-Sale Securities (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Investment securities available for sale:
Total Amortized Cost	$ 39,103	$ 41,632
Gross Unrealized Gains	874	799
Gross Unrealized Losses	(312)	(631)
Securities available for sale, at fair value	39,665	41,800
U.S. Treasury debt obligations
Investment securities available for sale:
Total Amortized Cost	4,261	831
Gross Unrealized Gains	2	2
Gross Unrealized Losses	(2)	0
Securities available for sale, at fair value	4,261	833
U.S. agency debt obligations
Investment securities available for sale:
Total Amortized Cost	1	1
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Securities available for sale, at fair value	1	1
Corporate debt securities guaranteed by U.S. government agencies
Investment securities available for sale:
Total Amortized Cost	1,001	1,282
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(23)	(49)
Securities available for sale, at fair value	979	1,234
RMBS
Investment securities available for sale:
Total Amortized Cost	23,877	24,737
Gross Unrealized Gains	760	689
Gross Unrealized Losses	(154)	(347)
Securities available for sale, at fair value	24,483	25,079
RMBS | Agency
Investment securities available for sale:
Total Amortized Cost	20,853	21,572
Gross Unrealized Gains	274	239
Gross Unrealized Losses	(141)	(332)
Securities available for sale, at fair value	20,986	21,479
RMBS | Non-Agency
Investment securities available for sale:
Total Amortized Cost	3,024	3,165
Gross Unrealized Gains	486	450
Gross Unrealized Losses	(13)	(15)
Securities available for sale, at fair value	3,497	3,600
CMBS
Investment securities available for sale:
Total Amortized Cost	5,838	6,116
Gross Unrealized Gains	47	34
Gross Unrealized Losses	(99)	(144)
Securities available for sale, at fair value	5,786	6,006
CMBS | Agency
Investment securities available for sale:
Total Amortized Cost	4,029	4,262
Gross Unrealized Gains	25	20
Gross Unrealized Losses	(71)	(84)
Securities available for sale, at fair value	3,983	4,198
CMBS | Non-Agency
Investment securities available for sale:
Total Amortized Cost	1,809	1,854
Gross Unrealized Gains	22	14
Gross Unrealized Losses	(28)	(60)
Securities available for sale, at fair value	1,803	1,808
Other ABS
Investment securities available for sale:
Total Amortized Cost	3,038	7,123
Gross Unrealized Gains	58	49
Gross Unrealized Losses	(13)	(36)
Securities available for sale, at fair value	3,083	7,136
Other securities
Investment securities available for sale:
Total Amortized Cost	1,087	1,542
Gross Unrealized Gains	6	24
Gross Unrealized Losses	(21)	(55)
Securities available for sale, at fair value	$ 1,072	$ 1,511