Condensed Consolidated Statements of Stockholders’ Equity - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2018		0	31,825,769
Beginning balance at Dec. 31, 2018	$ 136,949	$ 0	$ 32	$ 250,316	$ (18)	$ (113,381)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted common stock (in shares)			23,345
Vesting of restricted common stock	7			7
Exercise of stock options (in shares)			181,521
Exercise of stock options	257			257
Stock-based compensation expense	1,953			1,953
Unrealized gain on investments	16				16
Net loss	(20,299)					(20,299)
Ending balance (in shares) at Mar. 31, 2019		0	32,030,635
Ending balance at Mar. 31, 2019	118,883	$ 0	$ 32	252,533	(2)	(133,680)
Beginning balance (in shares) at Dec. 31, 2018		0	31,825,769
Beginning balance at Dec. 31, 2018	136,949	$ 0	$ 32	250,316	(18)	(113,381)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized gain on investments	18
Net loss	(62,873)
Ending balance (in shares) at Sep. 30, 2019		0	32,072,030
Ending balance at Sep. 30, 2019	80,546	$ 0	$ 32	256,768	0	(176,254)
Beginning balance (in shares) at Mar. 31, 2019		0	32,030,635
Beginning balance at Mar. 31, 2019	118,883	$ 0	$ 32	252,533	(2)	(133,680)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted common stock (in shares)			13,692
Vesting of restricted common stock	7			7
Exercise of stock options (in shares)			1,379
Exercise of stock options	1			1
Stock-based compensation expense	2,135			2,135
Unrealized gain on investments	3				3
Net loss	(20,941)					(20,941)
Ending balance (in shares) at Jun. 30, 2019		0	32,045,706
Ending balance at Jun. 30, 2019	100,088	$ 0	$ 32	254,676	1	(154,621)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted common stock (in shares)			13,691
Vesting of restricted common stock	7			7
Exercise of stock options (in shares)			12,633
Exercise of stock options	23			23
Stock-based compensation expense	2,062			2,062
Unrealized gain on investments	(1)				(1)
Net loss	(21,633)					(21,633)
Ending balance (in shares) at Sep. 30, 2019		0	32,072,030
Ending balance at Sep. 30, 2019	80,546	$ 0	$ 32	256,768	0	(176,254)
Beginning balance (in shares) at Dec. 31, 2019		0	32,170,605
Beginning balance at Dec. 31, 2019	60,197	$ 0	$ 32	259,018	0	(198,853)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted common stock (in shares)			13,390
Vesting of restricted common stock	7			7
Exercise of stock options (in shares)			137,213
Exercise of stock options	226			226
Stock-based compensation expense	1,955			1,955
Net loss	(23,041)					(23,041)
Ending balance (in shares) at Mar. 31, 2020		0	32,321,208
Ending balance at Mar. 31, 2020	39,344	$ 0	$ 32	261,206	0	(221,894)
Beginning balance (in shares) at Dec. 31, 2019		0	32,170,605
Beginning balance at Dec. 31, 2019	$ 60,197	$ 0	$ 32	259,018	0	(198,853)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	159,998
Unrealized gain on investments	$ 0
Net loss	(64,616)
Ending balance (in shares) at Sep. 30, 2020		0	46,184,087
Ending balance at Sep. 30, 2020	50,430	$ 0	$ 46	313,853	0	(263,469)
Beginning balance (in shares) at Mar. 31, 2020		0	32,321,208
Beginning balance at Mar. 31, 2020	39,344	$ 0	$ 32	261,206	0	(221,894)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in public offering, net of fees (in shares)			13,800,000
Issuance of common stock in public offering, net of fees	48,407		$ 14	48,393
Vesting of restricted common stock (in shares)			11,491
Vesting of restricted common stock	5			5
Exercise of stock options (in shares)			3,944
Exercise of stock options	9			9
Stock-based compensation expense	2,093			2,093
Net loss	(20,652)					(20,652)
Ending balance (in shares) at Jun. 30, 2020		0	46,136,643
Ending balance at Jun. 30, 2020	69,206	$ 0	$ 46	311,706	0	(242,546)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock under the Employee Stock Purchase Plan (in shares)			28,603
Issuance of stock under the Employee Stock Purchase Plan	92			92
Exercise of stock options (in shares)			18,841
Exercise of stock options	11			11
Stock-based compensation expense	2,045			2,045
Fees associated with public offering of common stock	(1)			(1)
Unrealized gain on investments	0
Net loss	(20,923)					(20,923)
Ending balance (in shares) at Sep. 30, 2020		0	46,184,087
Ending balance at Sep. 30, 2020	$ 50,430	$ 0	$ 46	$ 313,853	$ 0	$ (263,469)