CONDENSED CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Revision of Prior Period, Accounting Standards Update, Adjustment	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Accumulated Deficit Revision of Prior Period, Accounting Standards Update, Adjustment
Beginning balance (in shares) at Dec. 31, 2018			63,916,437
Beginning balance at Dec. 31, 2018	$ 73,192	$ 60,941	$ 6	$ 218,284	$ 542	$ (145,640)	$ 60,941
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(15,216)					(15,216)
Issuance of common stock to directors (in shares)			3,461
Vesting of restricted stock units (in shares)			278,680
Exercise of stock options (in shares)			482,444
Exercise of stock options	1,073			1,073
Stock-based compensation expense	7,225			7,225
Other comprehensive loss (loss)	296				296
Ending balance (in shares) at Mar. 31, 2019			64,681,022
Ending balance at Mar. 31, 2019	127,511		$ 6	226,582	838	(99,915)
Beginning balance (in shares) at Dec. 31, 2018			63,916,437
Beginning balance at Dec. 31, 2018	73,192	60,941	$ 6	218,284	542	(145,640)	60,941
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(25,267)
Ending balance (in shares) at Jun. 30, 2019			64,837,568
Ending balance at Jun. 30, 2019	120,573		$ 6	230,185	348	(109,966)
Beginning balance (in shares) at Dec. 31, 2018			63,916,437
Beginning balance at Dec. 31, 2018	73,192	$ 60,941	$ 6	218,284	542	(145,640)	$ 60,941
Ending balance (in shares) at Dec. 31, 2019			67,468,022
Ending balance at Dec. 31, 2019	$ 205,237		$ 6	340,929	(285)	(135,413)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201409Member
Beginning balance (in shares) at Mar. 31, 2019			64,681,022
Beginning balance at Mar. 31, 2019	$ 127,511		$ 6	226,582	838	(99,915)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(10,051)					(10,051)
Issuance of common stock to directors (in shares)			2,684
Vesting of restricted stock units (in shares)			6,010
Exercise of stock options (in shares)			147,852
Exercise of stock options	914			914
Stock-based compensation expense	2,689			2,689
Other comprehensive loss (loss)	(490)				(490)
Ending balance (in shares) at Jun. 30, 2019			64,837,568
Ending balance at Jun. 30, 2019	120,573		$ 6	230,185	348	(109,966)
Beginning balance (in shares) at Dec. 31, 2019			67,468,022
Beginning balance at Dec. 31, 2019	205,237		$ 6	340,929	(285)	(135,413)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(11,669)					(11,669)
Issuance of common stock to directors (in shares)			1,946
Vesting of restricted stock units (in shares)			46,031
Exercise of stock options (in shares)			129,082
Exercise of stock options	670			670
Stock-based compensation expense	3,476			3,476
Other comprehensive loss (loss)	17				17
Ending balance (in shares) at Mar. 31, 2020			67,645,081
Ending balance at Mar. 31, 2020	197,731		$ 6	345,075	(268)	(147,082)
Beginning balance (in shares) at Dec. 31, 2019			67,468,022
Beginning balance at Dec. 31, 2019	205,237		$ 6	340,929	(285)	(135,413)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ (23,484)
Exercise of stock options (in shares)	376,967
Ending balance (in shares) at Jun. 30, 2020			69,840,315
Ending balance at Jun. 30, 2020	$ 298,802		$ 7	458,174	(482)	(158,897)
Beginning balance (in shares) at Mar. 31, 2020			67,645,081
Beginning balance at Mar. 31, 2020	197,731		$ 6	345,075	(268)	(147,082)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(11,815)					(11,815)
Issuance of common stock from public offering, net of issuance costs (in shares)			1,931,206
Issuance of common stock from public offering, net of issuance costs	107,915		$ 1	107,914
Issuance of common stock to directors (in shares)			2,296
Vesting of restricted stock units (in shares)			13,567
Exercise of stock options (in shares)			248,165
Exercise of stock options	1,571			1,571
Stock-based compensation expense	3,614			3,614
Other comprehensive loss (loss)	(214)				(214)
Ending balance (in shares) at Jun. 30, 2020			69,840,315
Ending balance at Jun. 30, 2020	$ 298,802		$ 7	$ 458,174	$ (482)	$ (158,897)