Receivables, net - Aging Analysis of Past Due Loans (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total receivables		$ 9,156	$ 22,670	$ 26,584
Threshold period for current receivable		30 days
Real estate secured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due receivables		$ 558	2,739
Current	[1]	8,598	19,931
Total receivables	[2]	9,156	22,670
First lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due receivables		398	2,474
Current	[1]	6,904	17,679
Total receivables	[2]	7,302	20,153
Second lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due receivables		160	265
Current	[1]	1,694	2,252
Total receivables	[2]	1,854	2,517
Past Due, 30 - 89 days [Member] | Real estate secured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due receivables		277	1,737
Past Due, 30 - 89 days [Member] | First lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due receivables		179	1,572
Past Due, 30 - 89 days [Member] | Second lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due receivables		98	165
Past Due, 90 plus days [Member] | Real estate secured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due receivables		281	1,002
Past Due, 90 plus days [Member] | First lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due receivables		219	902
Past Due, 90 plus days [Member] | Second lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due receivables		$ 62	$ 100

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

[2] The receivable balances included in this table reflect the principal amount outstanding on the loan net of any charge-off recorded in accordance with our existing charge-off policies and include certain basis adjustments to the loan such as unearned income, unamortized 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, nonaccrual receivable and nonperforming receivable account balances.