Receivables Held for Sale - Summary of Components of Cumulative Lower of Amortized Cost or Fair Value Adjustment (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2012
Lower of amortized cost or fair value adjustment recorded as a component of:
Other revenues	$ 50	$ 1,597
Lower of amortized cost or fair value adjustment	50	1,709
Provision for credit losses		112
Other revenues	50	1,597
Lower of amortized cost or fair value adjustment	50	1,709
Fair Value [Member]
Lower of amortized cost or fair value adjustment recorded as a component of:
Other revenues	85	1,632
Lower of amortized cost or fair value adjustment	85	1,744
Provision for credit losses		112
Other revenues	85	1,632
Lower of amortized cost or fair value adjustment	85	1,744
REO [Member]
Lower of amortized cost or fair value adjustment recorded as a component of:
Other revenues	(26)	(220)
Lower of amortized cost or fair value adjustment	(26)	(26)
Other revenues	(26)	(220)
Lower of amortized cost or fair value adjustment	(26)	(26)
Short Sales [Member]
Lower of amortized cost or fair value adjustment recorded as a component of:
Other revenues	(9)	(9)
Lower of amortized cost or fair value adjustment	(9)	(9)
Other revenues	(9)	(9)
Lower of amortized cost or fair value adjustment	$ (9)	$ (9)