Derivative Financial Instruments (Notional Amount of Interest Rate Swap Agreements Designated as Fair Value and Cash Flow Hedges) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Derivative [Line Items]
Total	$ 5,221		$ 3,153
Increase in carrying value of long-term debt	(35)		174
Investment securities available for sale
Derivative [Line Items]
Investment securities available for sale	2,721		1,703
Long-term debt
Derivative [Line Items]
Long-term debt	2,500	[1]	1,450	[1]
Fair Value Hedges
Derivative [Line Items]
Total	5,089		3,023
Increase in carrying value of long-term debt	(35)		174
Fair Value Hedges | Investment securities available for sale
Derivative [Line Items]
Investment securities available for sale	2,589		1,573
Fair Value Hedges | Long-term debt
Derivative [Line Items]
Long-term debt	2,500	[1]	1,450	[1]
Cash Flow Hedges
Derivative [Line Items]
Total	132		130
Cash Flow Hedges | Investment securities available for sale
Derivative [Line Items]
Investment securities available for sale	132		130
Cash Flow Hedges | Long-term debt
Derivative [Line Items]
Long-term debt	$ 0	[1]	$ 0	[1]

[1] As of December 31, 2013, fair value hedges of long-term debt decreased the carrying value of long-term debt presented in our consolidated statement of condition by $35 million. As of December 31, 2012, fair value hedges of long-term debt increased the carrying value of long-term debt presented in our consolidated statement of condition by $174 million.