Receivables - Aging Analysis of Past Due Loans (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Real estate secured [Member]		Dec. 31, 2013 Real estate secured [Member]		Sep. 30, 2014 First Lien [Member]		Dec. 31, 2013 First Lien [Member]		Sep. 30, 2014 Second Lien [Member]		Dec. 31, 2013 Second Lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, 30 - 89 days past due			$ 1,803		$ 2,711		$ 1,630		$ 2,462		$ 173		$ 249
Financing Receivable, 90 plus days past due			1,042		1,730		936		1,538		106		192
Financing Receivable, Past Due, Total			2,845		4,441		2,566		4,000		279		441
Financing Receivable, Current			20,658	[1]	22,143	[1]	18,269	[1]	19,568	[1]	2,389	[1]	2,575	[1]
Total receivables	$ 23,503	$ 27,844	$ 23,503	[2]	$ 26,584	[2]	$ 20,835	[2]	$ 23,568	[2]	$ 2,668	[2]	$ 3,016	[2]
Threshold period for current receivable	30 days

[1] Receivables less than 30 days past due are presented as current.

[2] The receivable balances included in this table reflects the principal amount outstanding on the loan and 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 loans. However, these basis adjustments on the loans are excluded in other presentations of dollars of two-months-and-over contractual delinquency and nonperforming receivable account balances.