Consolidated Statements of Stockholders’ Equity - USD ($) $ in Thousands	Total	Secondary Offering	Common Stock	Common Stock Secondary Offering	Additional Paid-In Capital	Additional Paid-In Capital Secondary Offering	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2016			22,139,346
Beginning balance at Dec. 31, 2016	$ 93,041		$ 22		$ 220,089		$ (127,061)	$ (9)
Increase (Decrease) in Stockholders' and Temporary Equity [Roll Forward]
Issuance of common stock in connection with employee equity incentive plans, net (in shares)	827,556		1,027,595
Issuance of common stock in connection with employee equity incentive plans, net	$ 6,390		$ 1		6,389
Issuance of preferred stock upon exercise of warrants (in shares)			210,374
Tax withholding upon vesting of restricted stock awards	(46)				(46)
Stock-based compensation expense	9,752				9,752
Net loss	(29,740)						(29,740)
Net change in unrealized gains on available-for-sale securities	(56)							(56)
Common stock ending balance (in shares) at Dec. 31, 2017			23,377,315
Ending balance at Dec. 31, 2017	$ 79,341		$ 23		236,184		(156,801)	(65)
Increase (Decrease) in Stockholders' and Temporary Equity [Roll Forward]
Issuance of common stock in connection with employee equity incentive plans, net (in shares)	798,424		990,758
Issuance of common stock in connection with employee equity incentive plans, net	$ 9,319				9,319
Tax withholding upon vesting of restricted stock awards	(3,877)				(3,877)
Stock-based compensation expense	16,329				16,329
Net loss	(50,378)						(50,378)
Net change in unrealized gains on available-for-sale securities	$ 49							49
Common stock ending balance (in shares) at Dec. 31, 2018	24,368,073		24,368,073
Ending balance at Dec. 31, 2018	$ 52,137		$ 23		257,955		(205,825)	(16)
Increase (Decrease) in Stockholders' and Temporary Equity [Roll Forward]
Issuance of common stock in connection with employee equity incentive plans, net (in shares)	540,307		734,453
Issuance of common stock in connection with employee equity incentive plans, net	$ 9,495
Warrants exercised (in shares)			4,852
Issuance of common stock in connection with follow-on public offering, net of discounts and issuance costs (in shares)				1,575,342
Issuance of common stock in connection with follow-on public offering, net of issuance costs		$ 107,294		$ 2		$ 107,292
Tax withholding upon vesting of restricted stock awards	(5,288)				(5,288)
Stock-based compensation expense	26,241				26,241
Net loss	(54,568)						(54,568)
Net change in unrealized gains on available-for-sale securities	$ 98							98
Common stock ending balance (in shares) at Dec. 31, 2019	26,682,720		26,682,720
Ending balance at Dec. 31, 2019	$ 135,409		$ 25		$ 395,695		$ (260,393)	$ 82