Consolidated Statements of Changes in Stockholders' Equity (USD $) In Thousands	Total	Employee Stock Ownership Plan [Member]	Preferred Stock [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, 2011	$ 216,849	$ (4,193)		$ 336	$ 262,812	$ 186,666	$ (2,468)	$ (226,304)	$ (871)	$ 871
Net income	20,020					20,020
Other comprehensive gain (loss), net of tax	2,517						2,517
Stock awards	591				591
Tax benefit (expense) of stock plans	(608)				(608)
Treasury stock allocated to restricted stock plan					(282)	42		240
Allocation of ESOP stock	480	289			191
Cash dividend - $0.48, $0.48 and 0.49 per share for 2012, 2013 and 2014 respectively	(8,579)					(8,579)
Exercise of stock options	419					(40)		459
Purchase of 843,370, 533,018, 551,291 shares of common stock in 2012, 2013 and 2014 respectively	(11,897)							(11,897)
Sale of stock for the deferred compensation plan, net									224	(224)
Ending 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 gain (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, $0.48 and 0.49 per share for 2012, 2013 and 2014 respectively	(8,239)					(8,239)
Exercise of stock options	65					(5)		70
Purchase of 843,370, 533,018, 551,291 shares of common stock in 2012, 2013 and 2014 respectively	(8,108)							(8,108)
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 gain (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, $0.48 and 0.49 per share for 2012, 2013 and 2014 respectively	(8,241)					(8,241)
Exercise of stock options	349					(67)		416
Purchase of 843,370, 533,018, 551,291 shares of common stock in 2012, 2013 and 2014 respectively	(9,178)							(9,178)
Sale 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