Consolidation of Variable Interest Entities Consolidation of Variable Interest Entities (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Primary Beneficiary Variable Interest Entity
Variable Interest Entity [Line Items]
Primary Beneficiary Consolidated VIEs, assets	$ 464,032	$ 314,062
Primary Beneficiary Consolidated VIEs, liabilities	214,019	146,254
Not Primary Beneficiary Variable Interest Entity
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	2,384	2,384
Not Primary Beneficiary Non-consolidated VIEs, Maximum Exposure to Loss	$ 2,384	$ 2,384