Accumulated Other Comprehensive Income (Loss) - Summary of Changes in Accumulated Other Comprehensive Income (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Disclosure Accumulated Other Comprehensive Income Loss Summary Of Changes In Accumulated Other Comprehensive Income [Abstract]
Unrealized gains on cash flow hedging instruments	$ 65	$ 29	$ 2
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Tax	10	23	41
Reclassification Of Unrealized Gains Losses On Other Than Temporary Impaired Debt Securities Tax		0	0
Unrealized gains on securities available-for-sale, not other-than-temporarily impaired, net	16	33	25
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Tax	(9)	(20)	(3)
Other Comprehensive Income Unrealized Holding Gain Loss On Debt Securities Arising During Period Tax	0	0	0
Tax Effect of Net Unrealized Gains in Other Than Temporary Impairment Losses, Portion in Other Comprehensive Income (Loss) Net of Tax, Portion Attrible to Parent, Available-for-sale Securites	1	(1)	1
Other Comprehensive Income Loss Reclassification Adjustment For Sale Of Debt Securities Included In Net Income Tax	0	4	0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax, Portion Attributable to Parent	(9)	(7)	(5)
Other Comprehensive Income (Loss), Available-for-sale Securities, before Reclassification Adjustments, Tax	1	1	0
Other Comprehensive Income (Loss), Foreign Currency Translation Gain (Loss) Arising During Period, Tax	$ 1	$ (1)	$ 2