Derivative Instruments and Hedging Activities - (Losses) Gains Related to Derivative Instruments Not Designated as Hedging Instruments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Non-designated hedge interest rate derivatives
Other non-interest expense	$ (263)	$ 44	$ (155)	$ (172)