Asset-Backed Securities Issued - Summary of Carrying Value Components of Collateral for Asset-Backed Securities Issued and Outstanding (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	$ 1,622,636	$ 1,900,118
Residential Loans
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	1,237,114	1,474,386
Commercial Loans
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	182,184	194,991
Real Estate Securities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	195,278	221,676
Restricted Cash
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	286	327
Accrued Interest Receivable
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	3,365	4,347
REO
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	4,409	4,391
Sequoia
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	1,243,259	1,481,283
Sequoia | Residential Loans
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	1,237,114	1,474,386
Sequoia | Restricted Cash
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	147	147
Sequoia | Accrued Interest Receivable
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	1,589	2,359
Sequoia | REO
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	4,409	4,391
Residential Resecuritization
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	195,687	222,196
Residential Resecuritization | Real Estate Securities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	195,278	221,676
Residential Resecuritization | Restricted Cash
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	0	43
Residential Resecuritization | Accrued Interest Receivable
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	409	477
Commercial Securitization
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	183,690	196,639
Commercial Securitization | Commercial Loans
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	182,184	194,991
Commercial Securitization | Restricted Cash
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	139	137
Commercial Securitization | Accrued Interest Receivable
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	1,367	$ 1,511
Commercial Securitization | REO
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	$ 0