Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) Statement - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock Including Additional Paid in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]
Beginning Balance at Dec. 31, 2018	$ 212,112	$ 894,755	$ (113,613)	$ (569,030)
Beginning Balance (shares) at Dec. 31, 2018		141,067
Common stock issued under employee benefit plans, net of shares withheld for tax	3,761	$ 3,761
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation	(2,673)	$ 2,673
Common stock issued under employee benefit plans, net of shares withheld for tax (shares)		3,293
Allocated share-based compensation expense	9,782	$ 9,782
Net loss	(24,365)			(24,365)
Ending Balance at Mar. 31, 2019	198,556	$ 905,625	(113,613)	(593,456)
Ending Balance (shares) at Mar. 31, 2019		144,360
Cumulative Effect of New Accounting Principle in Period of Adoption				(61)
Beginning Balance at Dec. 31, 2019	233,529	$ 930,875	(113,613)	(583,733)
Beginning Balance (shares) at Dec. 31, 2019		146,818
Common stock issued under employee benefit plans, net of shares withheld for tax	1,863	$ 1,863
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation	(2,003)	$ 2,003
Common stock issued under employee benefit plans, net of shares withheld for tax (shares)		1,542
Allocated share-based compensation expense	7,637	$ 7,637
Net loss	(63,528)			(63,528)
Ending Balance at Mar. 31, 2020	$ 177,498	$ 938,372	$ (113,613)	$ (647,261)
Ending Balance (shares) at Mar. 31, 2020		148,360