Earnings Per Share - Computation of Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Earnings Per Share [Abstract]
Net income per consolidated statements of income	$ 3,320	$ 3,686
Net income allocated to participating securities	(22)	(21)
Net income allocated to common stock	3,298	3,665
Distributed earnings allocated to common stock	1,188	493
Undistributed earnings allocated to common stock	2,110	3,172
Net income allocated to common stock	$ 3,298	$ 3,665
Weighted average common shares outstanding, including shares considered participating securities	47,587	49,291
Less: Average participating securities	(315)	(269)
Weighted average shares	47,272	49,022
Basic earnings per common share	$ 0.07	$ 0.07
Weighted average common shares outstanding for basic earnings per common share	47,272	49,022
Add: Dilutive effects of assumed exercises of stock options	279	273
Weighted average shares and dilutive potential common shares	47,551	49,295
Diluted earnings per common share	$ 0.07	$ 0.07