Summary of Accrued Interest Payable on ABS Issued (Detail) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Debt Instrument [Line Items]
Accrued interest payable	$ 6,422	$ 5,930
Asset-backed Securities | Variable Interest Entity, Primary Beneficiary
Debt Instrument [Line Items]
Accrued interest payable	5,809	5,267
Asset-backed Securities | Variable Interest Entity, Primary Beneficiary | Sequoia
Debt Instrument [Line Items]
Accrued interest payable	3,017	2,356
Asset-backed Securities | Variable Interest Entity, Primary Beneficiary | Acacia
Debt Instrument [Line Items]
Accrued interest payable	$ 2,792	$ 2,911