Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Shares	Capital in Excess of Par Value	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2019		176,505
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	1,358
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
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, 2020		180,091
Beginning balance at Dec. 31, 2020	$ 1,077,295	$ 18	3,388,730	(2,295)	(2,309,158)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)	2,199	2,199
Shares issued under equity compensation plans	$ 17,106		17,106
Stock-based compensation	23,898		23,898
Comprehensive loss	(123,793)			(826)	(122,967)
Ending balance (in shares) at Mar. 31, 2021		182,290
Ending balance at Mar. 31, 2021	$ 994,506	$ 18	$ 3,429,734	$ (3,121)	$ (2,432,125)