Asset Quality (TDR charge off narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Amount charged off	$ 11	$ 21	$ 12	$ 23
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Amount charged off	1	5	2	7
Equipment Lease Financing [Member]
Financing Receivable, Modifications [Line Items]
Amount charged off	1	0	5	0
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Amount charged off	$ 3	$ 4	$ 3	$ 12