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
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
Comprehensive income (loss)	1,297
Ending Balance at Jun. 30, 2018	800,863	$ 428	282,622	567,988	(47,933)	(2,242)
Ending Balance, shares at Jun. 30, 2018		42,821
Cumulative effect of accounting change | Accounting Standards Update 2014-09 [Member]	3,019			3,019
Beginning Balance at Mar. 31, 2018	806,146	$ 428	280,840	560,810	(33,799)	(2,133)
Beginning Balance, shares at Mar. 31, 2018		42,799
Stock-based compensation expense	1,673		1,673
Issuance of common stock under equity award plans, net of forfeitures			109			(109)
Issuance of common stock under equity award plans, net of forfeitures, Share		22
Comprehensive income (loss)	(6,956)			7,178	(14,134)
Ending Balance at Jun. 30, 2018	800,863	$ 428	282,622	567,988	(47,933)	(2,242)
Ending Balance, shares at Jun. 30, 2018		42,821
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
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
Repurchase of common stock	(20,178)
Comprehensive income (loss)	31,167
Ending Balance at Jun. 30, 2019	840,529	$ 421	288,879	609,791	(48,564)	(9,998)
Ending Balance, shares at Jun. 30, 2019		42,091
Cumulative effect of accounting change | Accounting Standards Update 2016-02 [Member]	110			110
Beginning Balance at Mar. 31, 2019	842,041	$ 426	287,347	610,585	(53,761)	(2,556)
Beginning Balance, shares at Mar. 31, 2019		42,565
Stock-based compensation expense	2,200		2,200
Issuance of common stock under equity award plans, net of forfeitures			123			(123)
Issuance of common stock under equity award plans, net of forfeitures, Share		26
Repurchase of common stock	(20,178)					(20,178)
Retirement of treasury stock		$ (5)	(791)	(12,063)		12,859
Retirement of treasury stock, shares		(500)
Comprehensive income (loss)	16,466			11,269	5,197
Ending Balance at Jun. 30, 2019	$ 840,529	$ 421	$ 288,879	$ 609,791	$ (48,564)	$ (9,998)
Ending Balance, shares at Jun. 30, 2019		42,091