Derivatives - Credit Value Adjustment Recorded Related to Notional Amount of Derivatives Outstanding (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Derivative, Fair Value, Net	$ (268)	$ 77
Interest rate swap [Member]
Derivative [Line Items]
Derivative, Notional Amount	273,388	274,718
Interest Rate Cap [Member]
Derivative [Line Items]
Derivative, Notional Amount	6,656	7,500
Credit Default Swap, Buying Protection [Member]
Derivative [Line Items]
Derivative, Notional Amount	113,624	82,197
Credit Default Swap, Selling Protection [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ (17,296)	$ (19,161)