Earnings per Share - Reconciliation of Shares Outstanding for Basic and Diluted Earnings per Share (Detail) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Weighted average shares issued net of Treasury shares	17,146	17,132	16,954	17,261
Less: Unallocated ESOP shares	(374)	(407)	(382)	(416)
Unallocated incentive award shares and shares held by deferred compensation plan	(39)	(102)	(50)	(97)
Average basic shares outstanding	16,733	16,623	16,522	16,748
Average basic shares outstanding	16,733	16,623	16,522	16,748
Add: Effect of dilutive securities:
Stock options	200	61	204	93
Shares held by deferred compensation plan	20	20	20	24
Average diluted shares outstanding	16,953	16,704	16,746	16,865