Receivables Held for Sale - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended	3 Months Ended
	Jun. 30, 2012	Sep. 30, 2012	Sep. 30, 2012 REO [Member]	Sep. 30, 2012 Short Sales [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Period of receivables sold in multiple transactions		2 years
Percentage of fair value adjustment recorded on receivables at time of transfer	20.00%
Real estate secured receivables held for sale through short sale or transfer to REO			$ 79	$ 46
Reversed portion towards carrying value of assets held for sale			$ 26	$ 9