Net Gains (Losses) Relating to Derivative Instruments Designated as Cash Flow Hedges (Detail) (Cash Flow Hedging, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Amount of net gain recognized in OCI	$ 37	$ 89	$ 2
Interest Income Expense Net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of net gain reclassified into net income	83	69	60
Other Noninterest Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of ineffectiveness recognized in other noninterest income		$ 1	$ 6