Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Accumulated Deficit [Member]
Beginning Balances at Dec. 31, 2016	$ 151,068	$ 1	$ 440,670	$ (350)	$ (289,253)
Beginning Balances, shares at Dec. 31, 2016		5,807,314
Issuance of common stock upon exercise of options	$ 2,504		2,504
Issuance of common stock upon exercise of options, shares	141,833	141,833
Issuance of common stock under employee benefit plans	$ 464		464
Issuance of common stock under employee benefit plans, shares		40,541
Stock-based compensation	13,349		13,349
Other comprehensive income	350			$ 350
Net loss	(84,979)				(84,979)
Ending Balances at Dec. 31, 2017	82,756	$ 1	456,987		(374,232)
Ending Balances, shares at Dec. 31, 2017		5,989,688
Issuance of common stock upon exercise of options	$ 35		35
Issuance of common stock upon exercise of options, shares	3,643	3,643
Issuance of common stock under employee benefit plans	$ 17		17
Issuance of common stock under employee benefit plans, shares		130,905
Stock-based compensation	16,139		16,139
Issuance of common stock for the merger transaction	37,331		37,331
Issuance of common stock for the merger transaction, shares		5,141,915
Net loss	(76,333)				(76,333)
Ending Balances at Dec. 31, 2018	$ 59,945	$ 1	$ 510,509		$ (450,565)
Ending Balances, shares at Dec. 31, 2018		11,266,151