Receivables, net - Aging Analysis of Past Due Loans (Detail) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total receivables		$ 8,160	$ 9,156	$ 10,307
Threshold period for current receivable		30 days
Real estate secured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due receivables		$ 407	558
Current	[1]	7,753	8,598
Total receivables	[2]	8,160	9,156
First lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due receivables		277	398
Current	[1]	6,209	6,904
Total receivables	[2]	6,486	7,302
Second lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due receivables		130	160
Current	[1]	1,544	1,694
Total receivables	[2]	1,674	1,854
Past Due, 30 - 89 days [Member] | Real estate secured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due receivables		215	277
Past Due, 30 - 89 days [Member] | First lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due receivables		130	179
Past Due, 30 - 89 days [Member] | Second lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due receivables		85	98
Past Due, 90 plus days [Member] | Real estate secured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due receivables		192	281
Past Due, 90 plus days [Member] | First lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due receivables		147	219
Past Due, 90 plus days [Member] | Second lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due receivables		$ 45	$ 62

[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.