Derivative Financial Instruments - Recognized Derivative Income Included in Other Noninterest Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative Gain Loss On Derivative Net [Abstract]
Derivative income	$ 78	$ 72	$ 270	$ 370