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 Gain (Loss) [Member]	Treasury Stock [Member]	Common Stock Acquired by Deferred Compensation Plan [Member]	Deferred Compensation Plan Liability [Member]
Beginning Balance at Dec. 31, 2014	$ 218,259	$ (3,330)	$ 336	$ 265,260	$ 217,714	$ (7,109)	$ (254,612)	$ (304)	$ 304
Net income	15,093				15,093
Other comprehensive income, net of tax	783					783
Tax benefit (expense) of stock plans	13			13
Stock awards	985			985
Treasury stock allocated to restricted stock plan				1,215	(142)		(1,073)
Issued 660,998 treasury shares to finance acquisition	11,818			1,633			10,185
Purchased 373,594 shares of common stock	(6,457)						(6,457)
Allocation of ESOP stock	440	214		226
Cash dividend	(6,496)				(6,496)
Exercise of stock options	250				(54)		304
Sale/Purchase of stock for the deferred compensation plan								(7)	7
Ending Balance at Sep. 30, 2015	234,688	(3,116)	336	269,332	226,115	(6,326)	(251,653)	(311)	311
Beginning Balance at Dec. 31, 2015	238,446	(3,045)	336	269,757	229,140	(6,241)	(251,501)	(314)	314
Net income	16,994				16,994
Other comprehensive income, net of tax	630					630
Tax benefit (expense) of stock plans	(228)			(228)
Stock awards	1,181			1,181
Treasury stock allocated to restricted stock plan				1,081	(109)		(972)
Issued 660,998 treasury shares to finance acquisition	165,901			36,940			128,961
Allocation of ESOP stock	461	213		248
Cash dividend	(8,789)				(8,789)
Exercise of stock options	2,648				(764)		3,412
Sale/Purchase of stock for the deferred compensation plan								4	(4)
Ending Balance at Sep. 30, 2016	$ 417,244	$ (2,832)	$ 336	$ 308,979	$ 236,472	$ (5,611)	$ (120,100)	$ (310)	$ 310