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		Sep. 30, 2015	Dec. 31, 2014
Derivative Asset [Abstract]
Gross amounts recognized		$ 14,232	$ 13,203
Gross amounts offset		0	(222)
Net amounts presented in the Consolidated Balance Sheets		14,232	12,981
Gross amounts not offset	[1]	0	0
Net Amount		14,232	12,981
Derivative Liability [Abstract]
Gross amounts recognized		14,184	13,175
Gross amounts offset		0	(222)
Net amounts presented in the Consolidated Balance Sheets		14,184	12,953
Gross amounts not offset	[1]	(12,548)	(12,059)
Net Amount		$ 1,636	$ 894

[1] Amounts represent posted collateral.