Summary of Carrying Value Components of Collateral for Asset-Backed Securities Issued and Outstanding (Detail) (Asset-backed Securities, USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	$ 2,419,694	$ 2,893,012
Residential Loans
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	1,864,653	2,272,812
Commercial Loans
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	269,255	283,610
Real Estate Securities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	275,763	324,606
Restricted Cash
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	297	284
Accrued Interest Receivable
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	5,676	7,455
REO
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	4,050	4,245
Sequoia
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	1,871,923	2,281,688
Sequoia | Residential Loans
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	1,864,653	2,272,812
Sequoia | Restricted Cash
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	159	147
Sequoia | Accrued Interest Receivable
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	3,061	4,484
Sequoia | REO
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	4,050	4,245
Resecuritization
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	276,445	325,445
Resecuritization | Real Estate Securities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	275,763	324,606
Resecuritization | Accrued Interest Receivable
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	682	839
Commercial Securitization
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	271,326	285,879
Commercial Securitization | Commercial Loans
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	269,255	283,610
Commercial Securitization | Restricted Cash
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	138	137
Commercial Securitization | Accrued Interest Receivable
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral for ABS Issued	$ 1,933	$ 2,132