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	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Weighted-average discount rates	9.37%
Conditional prepayment rates	9.31%
Conditional default rates	4.02%
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	7 years 2 months 12 days	6 years 1 month 6 days
Weighted-average stated customer interest rate on underlying collateral	3.85%	3.85%
Weighted-average discount rates	9.50%	9.50%
Conditional prepayment rates	3.00%	3.00%
Conditional default rates	0.50%	0.50%
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	9 years 7 months 6 days	9 years 7 months 6 days
Weighted-average stated customer interest rate on underlying collateral	4.20%	4.20%
Weighted-average discount rates	10.40%	12.30%
Conditional prepayment rates	5.10%	8.10%
Conditional default rates	2.00%	2.00%