Derivative Instruments and Other Financial Instruments Used For Hedging - Schedule of Derivatives Designated as Cash Flow Hedges (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	$ 7	$ 3	$ 14	$ 5
Amount of Gain or (Loss) Recognized in OCI on Derivative Instruments (Effective Portion)	3	28	9	38
Interest income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	8	4	15	6
Interest expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(1)	(1)	(1)	(1)
Interest rate derivative contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in OCI on Derivative Instruments (Effective Portion)	$ 3	$ 28	$ 9	$ 38