Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock	Common stock	Additional paid-in Capital	Accumulated other comprehensive income (loss)	Accumulated deficit
Balance at Dec. 31, 2018	$ 476,984		$ 2	$ 616,573	$ (319)	$ (139,272)
Balance (in shares) at Dec. 31, 2018		1,969,797	15,409,023
Increase (Decrease) in Stockholders' Equity
Exercise of common stock options	83			83
Exercise of common stock options (in shares)			8,041
Compensation expense related to stock options for services	6,022			6,022
Unrealized gain (loss) on marketable securities	497				497
Net loss	(15,080)					(15,080)
Balance at Mar. 31, 2019	468,506		$ 2	622,678	178	(154,352)
Balance (in shares) at Mar. 31, 2019		1,969,797	15,417,064
Balance at Dec. 31, 2018	476,984		$ 2	616,573	(319)	(139,272)
Balance (in shares) at Dec. 31, 2018		1,969,797	15,409,023
Increase (Decrease) in Stockholders' Equity
Unrealized gain (loss) on marketable securities	804
Net loss	(34,779)
Balance at Jun. 30, 2019	456,986		$ 2	630,550	485	(174,051)
Balance (in shares) at Jun. 30, 2019		1,969,797	15,426,297
Balance at Mar. 31, 2019	468,506		$ 2	622,678	178	(154,352)
Balance (in shares) at Mar. 31, 2019		1,969,797	15,417,064
Increase (Decrease) in Stockholders' Equity
Exercise of common stock options	117			117
Exercise of common stock options (in shares)			9,233
Compensation expense related to stock options for services	7,755			7,755
Unrealized gain (loss) on marketable securities	307				307
Net loss	(19,699)					(19,699)
Balance at Jun. 30, 2019	456,986		$ 2	630,550	485	(174,051)
Balance (in shares) at Jun. 30, 2019		1,969,797	15,426,297
Balance at Dec. 31, 2019	$ 416,565		$ 2	639,567	216	(223,220)
Balance (in shares) at Dec. 31, 2019	15,429,154	1,969,797	15,429,154
Increase (Decrease) in Stockholders' Equity
Compensation expense related to stock options for services	$ 4,846			4,846
Unrealized gain (loss) on marketable securities	199				199
Net loss	(36,135)					(36,135)
Balance at Mar. 31, 2020	385,475		$ 2	644,413	415	(259,355)
Balance (in shares) at Mar. 31, 2020		1,969,797	15,429,154
Balance at Dec. 31, 2019	$ 416,565		$ 2	639,567	216	(223,220)
Balance (in shares) at Dec. 31, 2019	15,429,154	1,969,797	15,429,154
Increase (Decrease) in Stockholders' Equity
Unrealized gain (loss) on marketable securities	$ 865
Net loss	(85,158)
Balance at Jun. 30, 2020	$ 342,916		$ 2	650,211	1,081	(308,378)
Balance (in shares) at Jun. 30, 2020	15,438,124	1,969,797	15,438,124
Balance at Mar. 31, 2020	$ 385,475		$ 2	644,413	415	(259,355)
Balance (in shares) at Mar. 31, 2020		1,969,797	15,429,154
Increase (Decrease) in Stockholders' Equity
Exercise of common stock options	109			109
Exercise of common stock options (in shares)			8,970
Compensation expense related to stock options for services	5,689			5,689
Unrealized gain (loss) on marketable securities	666				666
Net loss	(49,023)					(49,023)
Balance at Jun. 30, 2020	$ 342,916		$ 2	$ 650,211	$ 1,081	$ (308,378)
Balance (in shares) at Jun. 30, 2020	15,438,124	1,969,797	15,438,124