Accumulated Other Comprehensive Income (Loss) - Summary of Changes in Accumulated Other Comprehensive Income (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Unrealized gains (losses) on cash flow hedging instruments:
Balance at beginning of period	$ (444)	$ (515)	$ (494)	$ (575)
Net gains (losses) arising during period	30	(65)	71	(27)
Reclassification adjustment for losses realized in net income	4	9	13	31
Total other comprehensive income (loss) for period	34	(56)	84	4
Balance at end of period	(410)	(571)	(410)	(571)
Unrealized gains (losses) on securities available-for-sale, not other-than temporarily impaired:
Balance at beginning of period	109	75	102	78
Reclassification of unrealized gains on other than temporary impaired debt securities, net of tax			1
Net unrealized holding gains arising during period, net of tax	20	52	35	58
Reclassification adjustment for (gains) losses realized in net income, net of tax	(5)	(9)	(14)	(18)
Total other comprehensive income for period	15	43	22	40
Balance at end of period	124	118	124	118
Unrealized gains (losses) on other-than-temporarily impaired debt securities available-for-sale:
Balance at beginning of period		(5)		(4)
Reclassification of unrealized (gains) losses on other than temporary impaired debt securities, net of tax			(1)
Other-than-temporary impairment on debt securities available-for-sale recognized in other comprehensive income, net of tax of $- million and $- million, respectively	1		1	(1)
Reclassification adjustment for (gains) losses realized in net income, net of tax of $- million and $- million, respectively	(1)
Total other comprehensive income for period				(1)
Balance at end of period		(5)		(5)
Pension and postretirement benefit plan liability:
Balance at beginning and end of period	(10)	1	(11)
Reclassification adjustment for (gains) losses realized in net income, net of tax of $1 million and $- million, respectively			1	1
Total other comprehensive income for period			1	1
Balance at end of period	(10)	1	(10)	1
Foreign currency translation adjustments:
Balance at beginning of period	7	16	7	10
Translation gains (losses), net of tax	4	(11)	4	(5)
Total other comprehensive income (loss) for period	4	(11)	4	(5)
Balance at end of period	11	5	11	5
Total accumulated other comprehensive loss at end of period	$ (285)	$ (452)	$ (285)	$ (452)	$ (396)