Derivative Instruments and Hedging Activities - Schedule of Gross Amounts of Derivative Assets and Derivative Liabilities (Detail) - Not Designated as Hedging Instruments [Member] - USD ($) $ in Thousands		Jun. 30, 2015	Dec. 31, 2014
Derivative Asset [Abstract]
Gross amounts recognized		$ 11,030	$ 13,203
Gross amounts offset		(17)	(222)
Net amounts presented in the Consolidated Balance Sheets		11,013	12,981
Net Amount		11,013	12,981
Derivative Liability [Abstract]
Gross amounts recognized		11,011	13,175
Gross amounts offset		(17)	(222)
Net amounts presented in the Consolidated Balance Sheets		10,994	12,953
Gross amounts not offset	[1]	(12,489)	(12,059)
Net Amount		$ (1,495)	$ 894

[1] Amounts represent posted collateral.