Asset Quality (TDR charge off narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Amount charged off	$ 6		$ 18	$ 23
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Amount charged off		5	2	12
Equipment Lease Financing [Member]
Financing Receivable, Modifications [Line Items]
Amount charged off			5
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Amount charged off	$ 2	$ 3	$ 5	$ 15