Fair Value of Financial Instruments - Quantitative Information about Significant Unobservable Inputs Used in Valuation of Level 3 Assets and Liabilities Measured at Fair Value (Detail) - Jun. 30, 2015	USD ($) $ / shares $ / senior_security $ / loan
Asset-backed Securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 1,173,336,000
Asset-backed Securities | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	5.00%
Prepayment rate	0.00%
Credit support	0.00%
Loss severity	20.00%
Default rate	0.00%
Asset-backed Securities | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	8.00%
Prepayment rate	31.00%
Credit support	69.00%
Loss severity	32.00%
Default rate	12.00%
Asset-backed Securities | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	5.00%
Prepayment rate	13.00%
Credit support	11.00%
Loss severity	26.00%
Default rate	6.00%
Commercial Secured Borrowings
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 65,232,000
Commercial Secured Borrowings | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Spread to swap rate	1.68%
Credit support	23.00%
Commercial Secured Borrowings | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Spread to swap rate	1.68%
Credit support	23.00%
Commercial Secured Borrowings | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Spread to swap rate	1.68%
Credit support	23.00%
Residential Loans Priced To Securitization and Whole Loan Market, Uncommitted to Sell
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 1,267,521,000
Residential Loans Priced To Securitization and Whole Loan Market, Uncommitted to Sell | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	430.00%
Prepayment rate	12.00%
Senior credit spread to TBA (usd per senior security) | $ / senior_security	3.5
Spread to swap rate	3.10%
Credit support	5.00%
Whole loan spread to TBA (usd per loan) | $ / loan	2.90
Residential Loans Priced To Securitization and Whole Loan Market, Uncommitted to Sell | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	500.00%
Prepayment rate	15.00%
Senior credit spread to TBA (usd per senior security) | $ / senior_security	3.5
Spread to swap rate	3.10%
Credit support	5.00%
Whole loan spread to TBA (usd per loan) | $ / loan	4.15
Residential Loans Priced To Securitization and Whole Loan Market, Uncommitted to Sell | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	440.00%
Prepayment rate	14.00%
Senior credit spread to TBA (usd per senior security) | $ / senior_security	3.50
Spread to swap rate	3.10%
Credit support	5.00%
Whole loan spread to TBA (usd per loan) | $ / loan	4.00
Residential Jumbo Hybrid Loans Priced To Whole Loan Market Uncommitted To Sell
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 181,279,000
Residential Jumbo Hybrid Loans Priced To Whole Loan Market Uncommitted To Sell | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Prepayment rate	15.00%
Spread to swap rate	1.25%
Residential Jumbo Hybrid Loans Priced To Whole Loan Market Uncommitted To Sell | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Prepayment rate	15.00%
Spread to swap rate	1.60%
Residential Jumbo Hybrid Loans Priced To Whole Loan Market Uncommitted To Sell | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Prepayment rate	15.00%
Spread to swap rate	1.29%
Residential Loans Priced To Whole Loan Market and Committed to Sell
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 350,951,000
Residential Loans Priced To Whole Loan Market and Committed to Sell | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Committed Sales Price | $ / shares	$ 101
Residential Loans Priced To Whole Loan Market and Committed to Sell | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Committed Sales Price | $ / shares	102
Residential Loans Priced To Whole Loan Market and Committed to Sell | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Committed Sales Price | $ / shares	$ 102
Residential Loans Held For Investment at Fair Value
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 1,237,114,000
Residential Loans at Lower of Cost or Fair Value
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 1,102,000
Residential Loans at Lower of Cost or Fair Value | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity	13.00%
Residential Loans at Lower of Cost or Fair Value | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity	30.00%
Residential Loans at Lower of Cost or Fair Value | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity	20.00%
Commercial Loans at Fair Value
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 235,616,000
Commercial Loans at Fair Value | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Spread to swap rate	1.68%
Credit support	23.00%
Commercial Loans at Fair Value | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Spread to swap rate	1.69%
Credit support	23.00%
Commercial Loans at Fair Value | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Spread to swap rate	1.68%
Credit support	23.00%
Investment Securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 1,157,599,000
Investment Securities | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	4.00%
Prepayment rate	1.00%
Credit support	0.00%
Loss severity	20.00%
Default rate	0.00%
Investment Securities | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	12.00%
Prepayment rate	35.00%
Credit support	49.00%
Loss severity	65.00%
Default rate	35.00%
Investment Securities | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	6.00%
Prepayment rate	13.00%
Credit support	5.00%
Loss severity	34.00%
Default rate	8.00%
Mortgage servicing rights
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 168,462,000
Mortgage servicing rights | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	8.00%
Prepayment rate	4.00%
Per loan annual cost to service	$ 72
Mortgage servicing rights | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	11.00%
Prepayment rate	60.00%
Per loan annual cost to service	$ 82
Mortgage servicing rights | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	10.00%
Prepayment rate	9.00%
Per loan annual cost to service	$ 78
Guarantee asset
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 6,417,000
Guarantee asset | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	11.00%
Prepayment rate	5.00%
Guarantee asset | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	11.00%
Prepayment rate	27.00%
Guarantee asset | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	11.00%
Prepayment rate	12.00%
REO
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 1,017,000
REO | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity	19.00%
REO | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity	76.00%
REO | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loss severity	55.00%
Loan Purchase Commitments
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 605,000
Loan Purchase Commitments | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
MSR Multiple	0
Fallout rate	2.00%
Loan Purchase Commitments | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
MSR Multiple	4
Fallout rate	97.00%
Loan Purchase Commitments | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
MSR Multiple	3.0
Fallout rate	26.00%