Net Gains (Losses) Relating to Derivative Instruments Designated as Cash Flow Hedges (Detail) (Cash Flow Hedging, USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Amount of loss recognized in OCI	$ 16	$ (32)	$ 25	$ (32)
Interest Income Expense Net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain reclassified from OCI into net interest income	$ (21)	$ 16	$ (41)	$ 31