Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income/(Loss)	Accumulated Deficit	Total
Balance at the beginning of period at Dec. 31, 2018	$ 3	$ 225,352	$ 7	$ (84,835)	$ 140,527
Balance at the beginning of period (in shares) at Dec. 31, 2018	34,193,666
Increase (Decrease) in Stockholders' Equity
Stock-based compensation expense		864			864
Foreign currency translation			56		56
Net loss				(15,934)	(15,934)
Balance at the end of period at Mar. 31, 2019	$ 3	226,216	63	(100,769)	125,513
Balance at the end of period (in shares) at Mar. 31, 2019	34,193,666
Balance at the beginning of period at Dec. 31, 2018	$ 3	225,352	7	(84,835)	140,527
Balance at the beginning of period (in shares) at Dec. 31, 2018	34,193,666
Increase (Decrease) in Stockholders' Equity
Net loss					(33,970)
Balance at the end of period at Jun. 30, 2019	$ 3	227,187	(3)	(118,805)	108,382
Balance at the end of period (in shares) at Jun. 30, 2019	34,193,666
Balance at the beginning of period at Dec. 31, 2018	$ 3	225,352	7	(84,835)	140,527
Balance at the beginning of period (in shares) at Dec. 31, 2018	34,193,666
Balance at the end of period at Dec. 31, 2019	$ 4	364,712	50	(165,863)	198,903
Balance at the end of period (in shares) at Dec. 31, 2019	39,728,416
Balance at the beginning of period at Mar. 31, 2019	$ 3	226,216	63	(100,769)	125,513
Balance at the beginning of period (in shares) at Mar. 31, 2019	34,193,666
Increase (Decrease) in Stockholders' Equity
Stock-based compensation expense		971			971
Foreign currency translation			(66)		(66)
Net loss				(18,036)	(18,036)
Balance at the end of period at Jun. 30, 2019	$ 3	227,187	(3)	(118,805)	108,382
Balance at the end of period (in shares) at Jun. 30, 2019	34,193,666
Balance at the beginning of period at Dec. 31, 2019	$ 4	364,712	50	(165,863)	198,903
Balance at the beginning of period (in shares) at Dec. 31, 2019	39,728,416
Increase (Decrease) in Stockholders' Equity
Exercise of stock options		370			370
Exercise of stock options (in shares)	25,778
Stock-based compensation expense		2,211			2,211
Stock-based compensation expense (in shares)	3,429
Foreign currency translation			25		25
Net loss				(26,179)	(26,179)
Balance at the end of period at Mar. 31, 2020	$ 4	367,293	75	(192,042)	175,330
Balance at the end of period (in shares) at Mar. 31, 2020	39,757,623
Balance at the beginning of period at Dec. 31, 2019	$ 4	364,712	50	(165,863)	$ 198,903
Balance at the beginning of period (in shares) at Dec. 31, 2019	39,728,416
Increase (Decrease) in Stockholders' Equity
Exercise of stock options (in shares)					25,778
Net loss					$ (66,572)
Balance at the end of period at Jun. 30, 2020	$ 4	378,455	(16)	(232,435)	146,008
Balance at the end of period (in shares) at Jun. 30, 2020	40,014,519
Balance at the beginning of period at Mar. 31, 2020	$ 4	367,293	75	(192,042)	175,330
Balance at the beginning of period (in shares) at Mar. 31, 2020	39,757,623
Increase (Decrease) in Stockholders' Equity
Issuance of common stock		8,707			8,707
Shares issued (in shares)	256,896
Stock-based compensation expense		2,455			2,455
Foreign currency translation			(91)		(91)
Net loss				(40,393)	(40,393)
Balance at the end of period at Jun. 30, 2020	$ 4	$ 378,455	$ (16)	$ (232,435)	$ 146,008
Balance at the end of period (in shares) at Jun. 30, 2020	40,014,519