Consolidated Statements Of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance, beginning of period at Dec. 31, 2014	$ 1,653,474	$ 934,447	$ 781,279	$ (62,252)
Balance, beginning of period (in shares) at Dec. 31, 2014		105,586
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(376,980)		(376,980)
Foreign currency translation adjustments	(12,849)			(12,849)
Unrealized gain on hedges, net of tax	4,200			4,200
Unrealized gain on note receivable, net of tax	0
Activity in company stock plans, net and other	3,443	$ 3,443
Activity in company stock plans, net and other (in shares)		703
Share-based compensation	5,463	$ 5,463
Cumulative share-based compensation in excess of fair value of modified liability awards	2,915	2,915
Excess tax from share-based compensation	(703)	(703)
Balance, end of period at Dec. 31, 2015	1,278,963	$ 945,565	404,299	(70,901)
Balance, end of period (in shares) at Dec. 31, 2015		106,289
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(81,445)		(81,445)
Foreign currency translation adjustments	(35,943)			(35,943)
Unrealized gain on hedges, net of tax	9,870			9,870
Unrealized gain on note receivable, net of tax	0
Equity component of debt discount on Convertible Senior Notes due 2022	10,719	$ 10,719
Re-acquisition of equity component of debt discount on Convertible Senior Notes due 2032	(1,625)	(1,625)
Issuance of common stock, net of transaction costs	96,547	$ 96,547
Issuance of common stock, net of transaction costs (in shares)		13,019
Activity in company stock plans, net and other	463	$ 463
Activity in company stock plans, net and other (in shares)		1,322
Share-based compensation	5,767	$ 5,767
Cumulative share-based compensation in excess of fair value of modified liability awards	203	203
Excess tax from share-based compensation	(1,705)	(1,705)
Balance, end of period at Dec. 31, 2016	1,281,814	$ 1,055,934	322,854	(96,974)
Balance, end of period (in shares) at Dec. 31, 2016		120,630
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	30,052		30,052
Foreign currency translation adjustments	16,264			16,264
Unrealized gain on hedges, net of tax	10,514			10,514
Unrealized gain on note receivable, net of tax	409			409
Equity component of debt discount on Convertible Senior Notes due 2022	(7)	$ (7)
Issuance of common stock, net of transaction costs	219,504	$ 219,504
Issuance of common stock, net of transaction costs (in shares)		26,450
Activity in company stock plans, net and other	(1,887)	$ (1,887)
Activity in company stock plans, net and other (in shares)		660
Share-based compensation	10,730	$ 10,730
Balance, end of period at Dec. 31, 2017	$ 1,567,393	$ 1,284,274	$ 352,906	$ (69,787)
Balance, end of period (in shares) at Dec. 31, 2017		147,740