Servicing Advance Liabilities - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2014	Nov. 30, 2014
Short-term Debt [Line Items]
Non-Recourse Debt, Number of Credit Facilities without Recourse		2
Secured Debt [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,500,000,000	$ 1,500,000,000
Debt Instrument, Maturity Date		Dec. 18, 2015
Secured Debt [Member] | Servicer Advance Facility [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	1,200,000,000.0	1,200,000,000.0	100,000,000
Proceeds from Lines of Credit	1,100,000,000
Secured Debt [Member] | Servicer Advance Reimbursement Agreement [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	200,000,000	200,000,000	950,000,000
Debt Instrument, Maturity Date		Mar. 31, 2015
Repayments of Lines of Credit	765,000,000
Period Following Expiration, Recovered Collections Remitted		18 months
Notification Period Required For Non-Renewal		120 days
Secured Debt [Member] | Servicing Advance Facilities [Member]
Short-term Debt [Line Items]
Servicer and Protective Advances Pledged As Collateral	$ 1,400,000,000	$ 1,400,000,000
Secured Debt [Member] | London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member]
Short-term Debt [Line Items]
Interest Spread		1.80%
Secured Debt [Member] | London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member]
Short-term Debt [Line Items]
Interest Spread		4.00%