Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Common stock [Member]	Additional paid-in capital [Member]	Retained earnings [Member]	Treasury stock [Member]	Accumulated other comprehensive income, net [Member]	Total
Balance in the beginning at Dec. 31, 2015	$ 513	$ 997,926	$ 38,670	$ (419,660)	$ 95	$ 617,544
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income			4,755			4,755
Stock-based compensation		1,791				1,791
Issuance under purchase and equity compensation plans, including (gain) loss on reissuance of treasury stock	1	(2,862)		2,422		(439)
Repurchase of shares				(32,918)		(32,918)
Cash dividends declared			(3,006)			(3,006)
Other comprehensive income (loss)					11,183	11,183
Balance in the ending at Jun. 30, 2016	514	996,855	40,419	(450,156)	11,278	598,910
Balance in the beginning at Dec. 31, 2016	514	984,087	55,454	(502,104)	(1,762)	536,189
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income			17,467			17,467
Stock-based compensation		1,869				1,869
Issuance under purchase and equity compensation plans, including (gain) loss on reissuance of treasury stock	1	(12,878)		5,624		(7,253)
Cash dividends declared			(4,351)			(4,351)
Warrant exercise		(1,933)		1,933
Other comprehensive income (loss)					566	566
Balance in the ending at Jun. 30, 2017	$ 515	$ 971,145	$ 68,570	$ (494,547)	$ (1,196)	$ 544,487