Condensed Consolidated Statements of Stockholders' Deficit (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	SVB Leerink	Common Shares	Common Shares SVB Leerink	Additional Paid-in Capital	Additional Paid-in Capital SVB Leerink	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning Balance at Dec. 31, 2017	$ (40,763)		$ 118		$ 546,092		$ (4)	$ (586,969)
Beginning Balance (in shares) at Dec. 31, 2017			118,325
Adjustment related to adoption of new revenue recognition standard ASC 606 | ASC 606	(2,711)							(2,711)
Stock-based compensation expense related to equity-classified awards | Equity-classified awards	583				583
Issuance of common stock in connection with warrant exercises	518		$ 1		517
Issuance of common stock in connection with warrant exercises (in shares)			518
Reduction in PIPE Warrant liability in connection with warrant exercises	1,101				1,101
Exercise of stock options	15				15
Exercise of stock options (in shares)			24
Net income (loss)	(8,988)							(8,988)
Ending Balance at Mar. 31, 2018	(50,245)		$ 119		548,308		(4)	(598,668)
Ending Balance (in shares) at Mar. 31, 2018			118,867
Beginning Balance at Dec. 31, 2018	(27,227)		$ 126		567,655		1	(595,009)
Beginning Balance (in shares) at Dec. 31, 2018			126,485
Issuance of common stock from the SVB Leerink sales agreement (net of issuance costs of $0.2 million)		$ 7,512		$ 13		$ 7,499
Issuance of common stock from the SVB Leerink sales agreement (net of issuance costs of $0.2 million) (in shares)				12,515
Stock-based compensation expense related to equity-classified awards | Equity-classified awards	584				584
Net income (loss)	555							555
Ending Balance at Mar. 31, 2019	$ (18,576)		$ 139		$ 575,738		$ 1	$ (594,454)
Ending Balance (in shares) at Mar. 31, 2019			139,000