Condensed Consolidated Statements of Changes in Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]
Beginning Balance at Dec. 31, 2017	$ 796,479	$ 429	$ 282,385	$ 546,843	$ (31,104)	$ (2,074)
Beginning Balance, shares at Dec. 31, 2017		42,899
Stock-based compensation expense	2,077		2,077
Issuance of common stock under equity award plans, net of forfeitures			59			(59)
Issuance of common stock under equity award plans, net of forfeitures, Share		18
Shares repurchased for tax withholding on equity awards	(3,682)	$ (1)	(3,681)
Shares repurchased for tax withholding on equity awards, Share		(118)
Comprehensive income (loss)	8,253			10,948	(2,695)
Ending Balance at Mar. 31, 2018	806,146	$ 428	280,840	560,810	(33,799)	(2,133)
Ending Balance, shares at Mar. 31, 2018		42,799
Cumulative effect of accounting change | Accounting Standards Update 2014-09 [Member]	3,019			3,019
Beginning Balance at Dec. 31, 2018	826,609	$ 428	286,544	598,788	(56,775)	(2,376)
Beginning Balance, shares at Dec. 31, 2018		42,778
Stock-based compensation expense	1,890		1,890
Issuance of common stock under equity award plans, net of forfeitures		$ (2)	182			(180)
Issuance of common stock under equity award plans, net of forfeitures, Share		(168)
Shares repurchased for tax withholding on equity awards	(1,269)		(1,269)
Shares repurchased for tax withholding on equity awards, Share		(45)
Comprehensive income (loss)	14,701			11,687	3,014
Ending Balance at Mar. 31, 2019	842,041	$ 426	$ 287,347	610,585	$ (53,761)	$ (2,556)
Ending Balance, shares at Mar. 31, 2019		42,565
Cumulative effect of accounting change | Accounting Standards Update 2016-02 [Member]	$ 110			$ 110