Condensed Consolidated Statements of Changes in Stockholders' Deficit (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in-Capital [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2019	$ (20,108)	$ 38	$ 648,391	$ 62	$ (668,599)
Balance (in shares) at Dec. 31, 2019		38,361
Issuance of common stock for equity awards, net of shares withheld for taxes	9	$ 1	8
Issuance of common stock for equity awards, net of shares withheld for taxes (in shares)		201
Stock-based compensation expense	4,651		4,651
Net loss	(36,802)				(36,802)
Other comprehensive income (loss)	(56)			(56)
Balance at Mar. 31, 2020	(52,306)	$ 39	653,050	6	(705,401)
Balance (in shares) at Mar. 31, 2020		38,562
Balance at Dec. 31, 2020	(16,660)	$ 49	765,607	(11)	(782,305)
Balance (in shares) at Dec. 31, 2020		49,403
Issuance of common stock, net of issuance costs	1,700		1,700
Issuance of common stock net of issuance costs (in shares)		134
Issuance of common stock for equity awards, net of shares withheld for taxes	8	$ 1	7
Issuance of common stock for equity awards, net of shares withheld for taxes (in shares)		405
Stock-based compensation expense	4,640		4,640
Net loss	(28,556)				(28,556)
Other comprehensive income (loss)	1			1
Balance at Mar. 31, 2021	$ (38,867)	$ 50	$ 771,954	$ (10)	$ (810,861)
Balance (in shares) at Mar. 31, 2021		49,942