Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Employee Stock Ownership Plan [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Gain [Member]	Treasury Stock [Member]	Common Stock Acquired by Deferred Compensation Plan [Member]	Deferred Compensation Plan Liability [Member]
Beginning Balance at Dec. 31, 2012	$ 219,792	$ (3,904)	$ 336	$ 262,704	$ 198,109	$ 49	$ (237,502)	$ (647)	$ 647
Net income	16,330				16,330
Other comprehensive income (loss), net of tax	(6,668)					(6,668)
Stock awards	671			671
Tax benefit (expense) of stock plans	(31)			(31)
Treasury stock allocated to restricted stock plan				(275)	6		269
Allocation of ESOP stock	538	288		250
Cash dividend $0.48, $0.49 and $0.52 per share for 2013, 2014 and 2015 respectively	(8,239)				(8,239)
Exercise of stock options	65				(5)		70
Purchase of 533,018, 551,291 and 373,594 shares of common stock in 2013, 2014 and 2015 respectively	(8,108)						(8,108)
Sale/Purchase of stock for the deferred compensation plan, net								(18)	18
Ending Balance at Dec. 31, 2013	214,350	(3,616)	336	263,319	206,201	(6,619)	(245,271)	(665)	665
Net income	19,920				19,920
Other comprehensive income (loss), net of tax	(490)					(490)
Stock awards	928			928
Tax benefit (expense) of stock plans	51			51
Treasury stock allocated to restricted stock plan				678	(99)		(579)
Allocation of ESOP stock	570	286		284
Cash dividend $0.48, $0.49 and $0.52 per share for 2013, 2014 and 2015 respectively	(8,241)				(8,241)
Exercise of stock options	349				(67)		416
Purchase of 533,018, 551,291 and 373,594 shares of common stock in 2013, 2014 and 2015 respectively	(9,178)						(9,178)
Sale/Purchase of stock for the deferred compensation plan, net								361	(361)
Ending Balance at Dec. 31, 2014	218,259	(3,330)	336	265,260	217,714	(7,109)	(254,612)	(304)	304
Net income	20,322				20,322
Other comprehensive income (loss), net of tax	868					868
Stock awards	1,300			1,300
Tax benefit (expense) of stock plans	32			32
Treasury stock allocated to restricted stock plan				1,214	(144)		(1,070)
Allocation of ESOP stock	603	285		318
Issued 660,098 treasury shares to finance acquisition	11,818			1,633			10,185
Cash dividend $0.48, $0.49 and $0.52 per share for 2013, 2014 and 2015 respectively	(8,693)				(8,693)
Exercise of stock options	396				(59)		455
Purchase of 533,018, 551,291 and 373,594 shares of common stock in 2013, 2014 and 2015 respectively	(6,459)						(6,459)
Sale/Purchase of stock for the deferred compensation plan, net								(10)	10
Ending Balance at Dec. 31, 2015	$ 238,446	$ (3,045)	$ 336	$ 269,757	$ 229,140	$ (6,241)	$ (251,501)	$ (314)	$ 314