Earnings per Share - Reconciliation of Shares Outstanding for Basic and Diluted Earnings per Share (Detail) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share [Abstract]
Weighted average shares issued net of Treasury shares	16,811	17,258	16,856	17,327
Less: Unallocated ESOP shares	(382)	(416)	(386)	(420)
Unallocated incentive award shares and shares held by deferred compensation plan	(28)	(102)	(37)	(95)
Average basic shares outstanding	16,401	16,740	16,433	16,812
Average basic shares outstanding	16,401	16,740	16,433	16,812
Add: Effect of dilutive securities:
Stock options	20	61	20	109
Shares held by deferred compensation plan	172	21	160	25
Average diluted shares outstanding	16,593	16,822	16,613	16,946