CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	At-the-market Offering	Public Offering	Common stock	Common stock At-the-market Offering	Common stock Public Offering	Additional paid-in capital	Additional paid-in capital At-the-market Offering	Additional paid-in capital Public Offering	Accumulated deficit	Accumulated other comprehensive income (loss)
Balance at Dec. 31, 2019	$ 17,575			$ 1			$ 328,156			$ (310,587)	$ 5
Balance (shares) at Dec. 31, 2019				9,120,078
CHANGES DURING THE PERIOD:
Comprehensive (loss) income	(207,678)									(207,673)	(5)
Exercise of options, vesting of restricted stock units and shares issued under employee stock purchase plan	260						260
Exercise of options, vesting of restricted stock units and shares issued under employee stock purchase plan (in shares)				258,000
Stock-based compensation	12,527						12,527
Deemed dividend to warrants holders due to warrant modifications	0						41			(41)
Classification of stock awards to derivative liability	(975)						(975)
Issuance of common stock, net of issuance costs			$ 53,649	$ 1					$ 53,648
Issuance of common stock, net of issuance costs (in shares)						7,776,875
Issuance of stock related to merger	196,170			$ 2			196,168
Issuance of stock related to merger (in shares)				24,765,999
Balance at Jun. 30, 2020	71,528			$ 4			589,825			(518,301)	0
Balance (shares) at Jun. 30, 2020				41,920,952
Balance at Mar. 31, 2020	69,535			$ 2			420,434			(350,861)	(40)
Balance (shares) at Mar. 31, 2020				15,375,282
CHANGES DURING THE PERIOD:
Comprehensive (loss) income	(167,400)									(167,440)	40
Exercise of options, vesting of restricted stock units and shares issued under employee stock purchase plan	(43)						(43)
Exercise of options, vesting of restricted stock units and shares issued under employee stock purchase plan (in shares)				132,692
Stock-based compensation	10,768						10,768
Classification of stock awards to derivative liability	657						657
Issuance of common stock, net of issuance costs			53,649	$ 1					53,648
Issuance of common stock, net of issuance costs (in shares)						7,776,875
Issuance of stock related to merger	104,362			$ 1			104,361
Issuance of stock related to merger (in shares)				18,636,103
Balance at Jun. 30, 2020	71,528			$ 4			589,825			(518,301)	$ 0
Balance (shares) at Jun. 30, 2020				41,920,952
Balance at Dec. 31, 2020	$ 37,493			$ 4			603,685			(566,196)
Balance (shares) at Dec. 31, 2020	43,205,221			43,205,221
CHANGES DURING THE PERIOD:
Comprehensive (loss) income	$ (40,474)									(40,474)
Exercise of options, vesting of restricted stock units and shares issued under employee stock purchase plan	403						403
Exercise of options, vesting of restricted stock units and shares issued under employee stock purchase plan (in shares)				254,351
Stock-based compensation	4,343						4,343
Issuance of common stock, net of issuance costs		$ 26,304	$ 46,824	$ 1				$ 26,304	$ 46,823
Issuance of common stock, net of issuance costs (in shares)					2,778,012	5,274,261
Balance at Jun. 30, 2021	$ 74,893			$ 5			681,558			(606,670)
Balance (shares) at Jun. 30, 2021	51,511,845			51,511,845
Balance at Mar. 31, 2021	$ 92,901			$ 5			679,642			(586,746)
Balance (shares) at Mar. 31, 2021				51,386,596
CHANGES DURING THE PERIOD:
Comprehensive (loss) income	(19,924)									(19,924)
Exercise of options, vesting of restricted stock units and shares issued under employee stock purchase plan	15						15
Exercise of options, vesting of restricted stock units and shares issued under employee stock purchase plan (in shares)				125,249
Stock-based compensation	1,901						1,901
Balance at Jun. 30, 2021	$ 74,893			$ 5			$ 681,558			$ (606,670)
Balance (shares) at Jun. 30, 2021	51,511,845			51,511,845