Summary of Significant Accounting Policies and New Accounting Pronouncements - Reclassifications (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Noninterest Expense	$ 864	$ 934	$ 876	$ 750	$ 1,519	$ 834	$ 766	$ 768	$ 3,424	[1]	$ 3,887	[1]	$ 4,664	[1]
Income tax expense (benefit)	30	(29)	(206)	149	(72)	32	71	125	(56)		156		422
Trading Liabilities	(8,164)				(10,875)				(8,164)		(10,875)
Restatement Adjustment [Member] | Elimination of Intercompany Trading Assets and Liabilities [Member]
Trading Liabilities													5,100
Accounting Standards Update 2014-01 [Member]
Noninterest Expense									(85)		(85)		(85)
Income tax expense (benefit)									$ (85)		$ (85)		$ (85)

[1] Expenses for the segments include fully apportioned corporate overhead expenses.