Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Employee Stock Ownership Plan	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock	Common Stock Acquired by Deferred Compensation Plan	Deferred Compensation Plan Liability
Beginning Balance at Dec. 31, 2015	$ 238,446	$ (3,045)	$ 336	$ 269,757	$ 229,140	$ (6,241)	$ (251,501)	$ (314)	$ 314
Net income	4,205				4,205
Other comprehensive income, net of tax	318					318
Tax expense of stock plans	(270)			(270)
Stock awards	330			330
Treasury stock allocated to restricted stock plan				1,108	(113)		(995)
Allocation of ESOP stock	149	71		78
Cash dividend	(2,197)				(2,197)
Exercise of stock options	95				(19)		114
Sale/Purchase of stock for the deferred compensation plan								9	(9)
Ending Balance at Mar. 31, 2016	241,076	(2,974)	336	271,003	231,016	(5,923)	(252,382)	(305)	305
Effect of adopting Accounting Standards Update (ASU) No. 2016-09				(11,129)	11,129
Beginning Balance at Dec. 31, 2016	572,038	(2,761)	336	364,433	238,192	(5,614)	(22,548)	(313)	313
Net income	12,018				12,018
Other comprehensive income, net of tax	232					232
Stock awards	730			730
Treasury stock allocated to restricted stock plan				(1,892)	892		1,000
Allocation of ESOP stock	245	71		174
Cash dividend	(4,787)				(4,787)
Exercise of stock options	2,204				(1,399)		3,603
Sale/Purchase of stock for the deferred compensation plan								(3)	3
Ending Balance at Mar. 31, 2017	$ 582,680	$ (2,690)	$ 336	$ 352,316	$ 256,045	$ (5,382)	$ (17,945)	$ (316)	$ 316