Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Shares	Capital in Excess of Par Value	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2018		173,530,000
Beginning balance at Dec. 31, 2018	$ 1,717,575	$ 17	$ 3,147,925	$ (6,316)	$ (1,424,051)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)		698,000
Shares issued under equity compensation plans	5,463		5,463
Stock-based compensation	25,385		25,385
Comprehensive loss	(114,912)			4,720	(119,632)
Ending balance (in shares) at Mar. 31, 2019		174,228,000
Ending balance at Mar. 31, 2019	1,633,511	$ 17	3,178,773	(1,596)	(1,543,683)
Beginning balance (in shares) at Dec. 31, 2018		173,530,000
Beginning balance at Dec. 31, 2018	$ 1,717,575	$ 17	3,147,925	(6,316)	(1,424,051)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)	115,000
Comprehensive loss	$ (222,893)
Ending balance (in shares) at Jun. 30, 2019		174,966,000
Ending balance at Jun. 30, 2019	1,557,155	$ 17	3,210,398	709	(1,653,969)
Beginning balance (in shares) at Mar. 31, 2019		174,228,000
Beginning balance at Mar. 31, 2019	$ 1,633,511	$ 17	3,178,773	(1,596)	(1,543,683)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)	95,000	738,000
Shares issued under equity compensation plans	$ 7,841		7,103
Stock-based compensation	24,522		24,522
Comprehensive loss	(107,981)			2,305	(110,286)
Ending balance (in shares) at Jun. 30, 2019		174,966,000
Ending balance at Jun. 30, 2019	1,557,155	$ 17	3,210,398	709	(1,653,969)
Beginning balance (in shares) at Dec. 31, 2019		176,505,000
Beginning balance at Dec. 31, 2019	1,405,391	$ 17	3,271,097	(1,005)	(1,864,718)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)		1,358,000
Shares issued under equity compensation plans	11,347		11,347
Stock-based compensation	24,211		24,211
Comprehensive loss	(144,523)			(5,872)	(138,651)
Ending balance (in shares) at Mar. 31, 2020		177,863,000
Ending balance at Mar. 31, 2020	1,296,426	$ 17	3,306,655	(6,877)	(2,003,369)
Beginning balance (in shares) at Dec. 31, 2019		176,505,000
Beginning balance at Dec. 31, 2019	$ 1,405,391	$ 17	3,271,097	(1,005)	(1,864,718)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)	49,000
Comprehensive loss	$ (216,931)
Ending balance (in shares) at Jun. 30, 2020		178,810,000
Ending balance at Jun. 30, 2020	1,256,240	$ 18	3,338,876	715	(2,083,369)
Beginning balance (in shares) at Mar. 31, 2020		177,863,000
Beginning balance at Mar. 31, 2020	$ 1,296,426	$ 17	3,306,655	(6,877)	(2,003,369)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)	0	947,000
Shares issued under equity compensation plans	$ 7,826	$ 1	7,825
Stock-based compensation	24,396		24,396
Comprehensive loss	(72,408)			7,592	(80,000)
Ending balance (in shares) at Jun. 30, 2020		178,810,000
Ending balance at Jun. 30, 2020	$ 1,256,240	$ 18	$ 3,338,876	$ 715	$ (2,083,369)