CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ (DEFICIT) EQUITY (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2018		22,466
Beginning balance at Dec. 31, 2018	$ 51,975	$ 7	$ 371,463	$ 1,992	$ (321,487)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		111
Exercise of common stock options	1,348		1,348
Stock-based compensation			4,797
Settlement of restricted stock (in shares)		0
Vesting of common stock warrants	4,797
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures		157
Stock Issued During Period, Value, Restricted Stock Award, Gross		$ 0	0
Other comprehensive income	77			77
Ending balance (in shares) at Jun. 30, 2019		22,828
Ending balance at Jun. 30, 2019	46,538	$ 7	378,773	2,069	(334,311)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Issued During Period, Value, Employee Stock Purchase Plan	1,165	$ 94	1,165
Net Income (Loss) Attributable to Parent	(12,824)				(12,824)
Beginning balance (in shares) at Mar. 31, 2019		22,570
Beginning balance at Mar. 31, 2019	47,177	$ 7	373,351	1,620	(327,801)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		80
Exercise of common stock options	1,175		1,175
Stock-based compensation			3,082
Settlement of restricted stock (in shares)		0
Vesting of common stock warrants	3,082
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures		84
Stock Issued During Period, Value, Restricted Stock Award, Gross		$ 0	0
Other comprehensive income	449			449
Ending balance (in shares) at Jun. 30, 2019		22,828
Ending balance at Jun. 30, 2019	46,538	$ 7	378,773	2,069	(334,311)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Issued During Period, Value, Employee Stock Purchase Plan	1,165	$ 94	1,165
Net Income (Loss) Attributable to Parent	(6,510)				(6,510)
Beginning balance (in shares) at Dec. 31, 2019		26,547
Beginning balance at Dec. 31, 2019	$ 143,267	$ 8	480,578	1,312	(338,631)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)	275	275
Exercise of common stock options	$ 5,426		$ 5,426
Stock Issued During Period, Shares, Warrants Exercised In Period	0	9	0
Stock-based compensation	$ 12,347		$ 12,347
Settlement of restricted stock (in shares)		416
Other comprehensive income	1,402			1,402
Ending balance (in shares) at Jun. 30, 2020		27,275
Ending balance at Jun. 30, 2020	130,465	$ 8	499,663	2,714	(371,920)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	(33,289)				(33,289)
Beginning balance (in shares) at Mar. 31, 2020		26,824
Beginning balance at Mar. 31, 2020	138,358	$ 8	487,903	2,609	(352,162)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		114
Exercise of common stock options	2,281		2,281
Stock-based compensation	8,167		8,167
Settlement of restricted stock (in shares)		309
Other comprehensive income	105			105
Ending balance (in shares) at Jun. 30, 2020		27,275
Ending balance at Jun. 30, 2020	130,465	$ 8	499,663	$ 2,714	(371,920)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Issued During Period, Value, Employee Stock Purchase Plan	1,312	$ 28	$ 1,312
Net Income (Loss) Attributable to Parent	$ (19,758)				$ (19,758)