Servicing of Residential Loans - Schedule of Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities (Detail)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Minimum [Member]
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Weighted-average life in years	6 years 4 months 24 days	7 years 0 months 0 days
Weighted-average stated borrower interest rate on underlying collateral	3.93%	4.48%
Weighted-average discount rate	9.30%	9.50%
Conditional prepayment rate	6.92%	7.26%
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities, Probability of Default	0.73%	0.64%
Maximum [Member]
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Weighted-average life in years	7 years 0 months 0 days	7 years 8 months 12 days
Weighted-average stated borrower interest rate on underlying collateral	4.14%	4.67%
Weighted-average discount rate	9.55%	9.50%
Conditional prepayment rate	9.62%	8.35%
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities, Probability of Default	0.81%	0.66%