Loans and Allowance for Loan Losses (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended			3 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Commercial portfolio	Jun. 30, 2013 Commercial portfolio	Jun. 30, 2014 Commercial portfolio	Jun. 30, 2013 Commercial portfolio	Jun. 30, 2014 Consumer portfolio	Jun. 30, 2013 Consumer portfolio	Jun. 30, 2014 Consumer portfolio	Jun. 30, 2013 Consumer portfolio	Jun. 30, 2013 Purchased credit-impaired loans	Jun. 30, 2014 Purchased credit-impaired loans	Jun. 30, 2013 Purchased credit-impaired loans	Mar. 31, 2014 Purchased credit-impaired loans	Jun. 30, 2014 Unallocated portfolio	Jun. 30, 2014 Unallocated portfolio	Jun. 30, 2013 Unallocated portfolio	Mar. 31, 2013 Unallocated portfolio
Financing Receivable, Allowance for Credit Losses
Allowance for loan losses, beginning of period	$ 557	$ 638	$ 568	$ 653	$ 479	$ 486	$ 421	$ 418	$ 55	$ 113	$ 69	$ 124	$ 1	$ 1	$ 1	$ 3	$ 20	$ 77	$ 110	$ 38
(Reversal of) provision for loan losses	9	(3)	(9)	(6)	7	(3)	58	65	(3)		(15)	1					5	(52)	(72)
(Reversal of) Provision for purchased credit-impaired loan losses not subject to FDIC indemnification			2											2
Other			(1)				(1)
Decrease in allowance covered by FDIC indemnification		(2)											(2)
Loans charged-off	(12)	(20)	(21)	(39)	(8)	(12)	(14)	(15)	(4)	(8)	(7)	(21)			(3)
Recoveries of loans previously charged-off	5	12	20	17	4	9	18	12	1	1	2	2	2		3
Allowance for loan losses, end of period	$ 559	$ 625	$ 559	$ 625	$ 482	$ 480	$ 482	$ 480	$ 49	$ 106	$ 49	$ 106	$ 1	$ 3	$ 1	$ 3	$ 25	$ 25	$ 38	$ 38