Schedule of Repurchase Agreements Obligation by Type of Collateral Pledged (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	$ 42,102	$ 29,907
Gross and Net Amounts of Liabilities Presented in the Statement of Financial Condition	66,896	38,560
Net Amount, Liabilities	5,638	97
Asset-backed Securities
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	42,102
Repurchase Agreements
Assets Sold under Agreements to Repurchase [Line Items]
Gross and Net Amounts of Liabilities Presented in the Statement of Financial Condition	42,102	$ 29,907
Net Amount, Liabilities	0
Overnight and Continuous \| Repurchase Agreements
Assets Sold under Agreements to Repurchase [Line Items]
Net Amount, Liabilities	0
Up to 30 Days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	42,102
Up to 30 Days \| Asset-backed Securities
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	42,102
Up to 30 Days \| Repurchase Agreements
Assets Sold under Agreements to Repurchase [Line Items]
Net Amount, Liabilities	0
30 - 90 Days \| Repurchase Agreements
Assets Sold under Agreements to Repurchase [Line Items]
Net Amount, Liabilities	0
Greater than 90 Days \| Repurchase Agreements
Assets Sold under Agreements to Repurchase [Line Items]
Net Amount, Liabilities	$ 0