Net Interest Revenue (Components of Interest Revenue and Interest Expenses) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net Interest Revenue [Abstract]
Deposits with banks	$ 125	$ 141	$ 149
U.S. Treasury and federal agencies	706	799	775
State and political subdivisions	250	215	221
Other investments	1,332	1,552	1,493
Securities purchased under resale agreements	45	51	28
Loans and leases	252	253	278
Other interest-earning assets	4	3	2
Total interest revenue	2,714	3,014	2,946
Deposits	93	166	220
Short-term borrowings	60	73	96
Long-term debt	232	222	289
Other interest-bearing liabilities	26	15	8
Total interest expense	411	476	613
Net interest revenue	$ 2,303	$ 2,538	$ 2,333