Premises and Equipment (Summary of Leases) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Premises and Equipment
Total rent expense applicable to operating leases	$ 227	$ 230	$ 215
Rental income from owned properties and subleases	7	8	8
Operating leases, future minimum payments due, current	224
Operating leases, future minimum payments, due in two years	205
Operating leases, future minimum payments, due in three years	186
Operating leases, future minimum payments, due in four years	160
Operating leases, future minimum payments, due in five years	137
Operating leases, future minimum payments, due thereafter	$ 552