Quantitative Information about Significant Unobservable Inputs Used in Valuation of Level 3 Assets and Liabilities Measured at Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013
Residential Loans Priced To Securitization
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value, Assets	$ 1,047,686
Residential Loans Priced To Securitization | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	4.00%
Prepayment rate	10.00%
Default rate	1.00%
Loss severity	22.00%
Credit support	7.00%
Residential Loans Priced To Securitization | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	4.00%
Prepayment rate	10.00%
Default rate	1.00%
Loss severity	22.00%
Credit support	7.00%
Residential Loans Priced To Securitization | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	4.00%
Prepayment rate	10.00%
Default rate	1.00%
Loss severity	22.00%
Credit support	7.00%
Residential Loans Priced To Whole Loan Market
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value, Assets	171,682
Residential Loans Priced To Whole Loan Market | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Pool fallout assumption	0.00%
Fallout assumption price discount	0.00%
Residential Loans Priced To Whole Loan Market | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Pool fallout assumption	5.00%
Fallout assumption price discount	0.05%
Residential Loans Priced To Whole Loan Market | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Pool fallout assumption	4.00%
Fallout assumption price discount	0.04%
Residential Loans at Lower of Cost or Fair Value
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value, Assets	1,122
Residential Loans at Lower of Cost or Fair Value | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity	15.00%
Residential Loans at Lower of Cost or Fair Value | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity	28.00%
Residential Loans at Lower of Cost or Fair Value | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity	21.00%
Trading and AFS securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value, Assets	1,314,305
Trading and AFS securities | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	6.00%
Prepayment rate	1.00%
Default rate	0.00%
Loss severity	20.00%
Credit support	0.00%
Trading and AFS securities | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	18.00%
Prepayment rate	40.00%
Default rate	37.00%
Loss severity	64.00%
Credit support	59.00%
Trading and AFS securities | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	7.00%
Prepayment rate	14.00%
Default rate	10.00%
Loss severity	38.00%
Credit support	6.00%
Mortgage Servicing Rights
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value, Assets	43,098
Mortgage Servicing Rights | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	12.00%
Prepayment rate	6.00%
Mortgage Servicing Rights | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	12.00%
Prepayment rate	50.00%
Mortgage Servicing Rights | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	12.00%
Prepayment rate	8.00%
REO
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value, Assets	$ 2,117
REO | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Historical loss adjustment	0.00%
REO | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Historical loss adjustment	40.00%
REO | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Historical loss adjustment	10.00%