Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	At-the-market offerings [Member]	Common Stock [Member]	Common Stock [Member] At-the-market offerings [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] At-the-market offerings [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2016	$ 209,837		$ 4		$ 263,403			$ (53,570)
Beginning balance, shares at Dec. 31, 2016			36,018,540
Issuance of common stock	141,000				141,000
Issuance of common stock, shares			6,250,000
Exercise of stock options	1,156				1,156
Exercise of stock options, shares			141,759
Issuance of shares under employee stock purchase plan	825				825
Issuance of shares under employee stock purchase plan, shares			64,786
Equity-based compensation	15,322				15,322
Equity-based compensation, shares			(90,462)
Net loss	(67,543)							(67,543)
Ending balance at Dec. 31, 2017	300,597		$ 4		421,706			(121,113)
Ending balance, shares at Dec. 31, 2017			42,384,623
Retroactive adjustment to beginning accumulated deficit (ASU 2014-09 [Member]) at Dec. 31, 2018	5,431							5,431
Issuance of common stock		$ 28,548		$ 1		$ 28,547
Issuance of common stock, shares				1,659,300
Exercise of stock options	10,651				10,651
Exercise of stock options, shares			1,142,944
Issuance of shares under employee stock purchase plan	1,018				1,018
Issuance of shares under employee stock purchase plan, shares			68,865
Equity-based compensation	17,046				17,046
Equity-based compensation, shares			(31,252)
Other comprehensive income (loss)	(28)						$ (28)
Net loss	(85,343)							(85,343)
Ending balance at Dec. 31, 2018	$ 277,920		$ 5		478,968		(28)	(201,025)
Ending balance, shares at Dec. 31, 2018	45,224,480		45,224,480
Retroactive adjustment to beginning accumulated deficit (ASC 842 [Member]) at Dec. 31, 2019	$ (320)							(320)
Issuance of common stock		$ 72,256				$ 72,256
Issuance of common stock, shares				4,518,579
Exercise of stock options	$ 3,086				3,086
Exercise of stock options, shares	364,404		364,404
Issuance of shares under employee stock purchase plan	$ 1,092				1,092
Issuance of shares under employee stock purchase plan, shares			90,581
Equity-based compensation	15,091				15,091
Other comprehensive income (loss)	289						289
Net loss	(99,533)							(99,533)
Ending balance at Dec. 31, 2019	$ 269,881		$ 5		$ 570,493		$ 261	$ (300,878)
Ending balance, shares at Dec. 31, 2019	50,198,044		50,198,044