Net Interest Revenue (Components of Interest Revenue and Interest Expenses) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Net Interest Revenue [Abstract]
Deposits with banks	$ 51		$ 31		$ 85		$ 62
U.S. Treasury and federal agencies	164		183		327		377
State and political subdivisions	44		54		115		105
Other investments	318		339		637		680
Securities purchased under resale agreements	10		12		19		25
Loans and leases	61		79		119		135
Other interest-earning assets	2		2		3		3
Total interest revenue	650		700		1,305		1,387
Deposits	18		27		33		61
Short-term borrowings(1)	(12)	[1]	15	[1]	3	[1]	31	[1]
Long-term debt	64		54		127		110
Other interest-bearing liabilities	19		8		26		13
Total interest expense	89		104		189		215
Net interest revenue	$ 561		$ 596		$ 1,116		$ 1,172

[1] The negative interest expense for the three months ended June 30, 2014 was associated with a reclassification of certain derivative contracts that hedge our interest-rate risk on certain assets and liabilities. This reclassification reduced total interest revenue and total interest expense for the three months ended June 30, 2014.