Receivables Held for Sale - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Receivables held for sale	$ 1,097	[1]		$ 860	[1]
Other Income [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Initial lower of amortized cost or fair value adjustment	0		60
Subsequent to initial transfer to held for sale	17		(171)
Fair Value [Member] | Other Income [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Initial lower of amortized cost or fair value adjustment	0		60
Subsequent to initial transfer to held for sale	16		(176)
First Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Receivables held for sale	1,097			860
Threshold, days past due to initiate sale activities for first lien real estate secured receivables	180 days
Aggregate unpaid balance	431		439
Aggregate carrying balance	$ 311		$ 342

[1] The receivable balances included in this table reflect the current carrying amount of the loan excluding certain basis adjustments to the loan such as deferred fees and costs on originated loans, purchase accounting fair value adjustments and premiums or discounts on purchased receivables.