Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Preferred Stock [Member] Series A Convertible Preferred Shares [Member]	Preferred Stock [Member] Series B Convertible Preferred Shares [Member]	Common Stock [Member]	Treasury Stock [Member]	Additional Paid in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Beginning Balance at Dec. 31, 2017	$ 16,060	$ 25,406	$ 68		$ 5,340	$ (31,355)	$ 0	$ 15,519
Beginning Balance (in shares) at Dec. 31, 2017	128,738	126,909	6,795,627
Conversion of convertible preferred shares into common shares (in shares)	128,738	126,909
Conversion of convertible preferred shares into common shares	$ (16,060)	$ (25,406)
Conversion of convertible preferred shares into common shares			$ 194		41,272	0	0	0
Conversion of convertible preferred shares into common shares (in shares)			19,475,788
Exchange of common shares in connection with the Merger	$ 0	$ 0	$ 68		85,992	0	0	86,060
Exchange of common shares in connection with the Merger (in shares)	0	0	6,805,608
Issuance of common shares, net of issuance costs	$ 0	$ 0	$ 63		78,455	0	0	78,518
Issuance of common shares, net of issuance costs (in shares)	0	0	6,325,000
Issuance of common stock pursuant to settlement of restricted stock units	$ 0	$ 0	$ 1		(1)	0	0	0
Issuance of common stock pursuant to settlement of restricted stock units (in shares)	0	0	1,875
Unrealized comprehensive gain (loss) on marketable securities/short term investments			$ 0		0	0	10	10
Stock-based compensation			0		5,382	0	0	5,382
Net loss	$ 0	$ 0	0		0	(15,343)	0	(15,343)
Ending Balance at Mar. 31, 2018	$ 0	$ 0	$ 394		216,440	(46,698)	10	170,146
Ending Balance (in shares) at Mar. 31, 2018	0	0	39,403,898
Beginning Balance at Dec. 31, 2017	$ 16,060	$ 25,406	$ 68		5,340	(31,355)	0	15,519
Beginning Balance (in shares) at Dec. 31, 2017	128,738	126,909	6,795,627
Unrealized comprehensive gain (loss) on marketable securities/short term investments								(79)
Net loss								(31,110)
Ending Balance at Jun. 30, 2018	$ 0	$ 0	$ 395		219,225	(62,465)	(79)	157,076
Ending Balance (in shares) at Jun. 30, 2018	0	0	39,506,527
Beginning Balance at Mar. 31, 2018	$ 0	$ 0	$ 394		216,440	(46,698)	10	170,146
Beginning Balance (in shares) at Mar. 31, 2018	0	0	39,403,898
Issuance of common stock pursuant to exercise of stock options	$ 0	$ 0	$ 1		(1)	0	0	0
Issuance of common stock pursuant to exercise of stock options (in shares)	0	0	61,536
Issuance of common stock pursuant to settlement of restricted stock units	$ 0	$ 0	$ 0		0	0	0	0
Issuance of common stock pursuant to settlement of restricted stock units (in shares)	0	0	41,093
Unrealized comprehensive gain (loss) on marketable securities/short term investments			$ 0		0	0	(89)	(89)
Stock-based compensation			0		2,786	0	0	2,786
Net loss	$ 0	$ 0	0		0	(15,767)	0	(15,767)
Ending Balance at Jun. 30, 2018	$ 0	$ 0	$ 395		219,225	(62,465)	(79)	157,076
Ending Balance (in shares) at Jun. 30, 2018	0	0	39,506,527
Beginning Balance at Dec. 31, 2018			$ 452	$ (668)	300,253	(105,873)	(127)	194,037
Beginning Balance (in shares) at Dec. 31, 2018			45,194,736
Issuance of common stock pursuant to exercise of stock options			$ 0	0	0	0	0	0
Issuance of common stock pursuant to exercise of stock options (in shares)			19,701
Stock repurchase			$ 0	(725)	(2)	0	0	(727)
Stock repurchase (in shares)			0
Retirement of treasury stock			$ (1)	1,393	(1,392)	0	0	0
Retirement of treasury stock (in shares)			100,000
Unrealized comprehensive gain (loss) on marketable securities/short term investments			$ 0	0	0	0	38	38
Stock-based compensation			0	0	3,180	0	0	3,180
Net loss			0	0	0	(19,451)	0	(19,451)
Ending Balance at Mar. 31, 2019			$ 451	0	302,039	(125,324)	(89)	177,077
Ending Balance (in shares) at Mar. 31, 2019			45,114,437
Beginning Balance at Dec. 31, 2018			$ 452	(668)	300,253	(105,873)	(127)	194,037
Beginning Balance (in shares) at Dec. 31, 2018			45,194,736
Unrealized comprehensive gain (loss) on marketable securities/short term investments								271
Net loss								(38,131)
Ending Balance at Jun. 30, 2019			$ 503	(344)	392,205	(144,004)	144	248,504
Ending Balance (in shares) at Jun. 30, 2019			50,332,435
Beginning Balance at Mar. 31, 2019			$ 451	0	302,039	(125,324)	(89)	177,077
Beginning Balance (in shares) at Mar. 31, 2019			45,114,437
Issuance of common stock pursuant to exercise of stock options			$ 0	0	0	0	0	0
Issuance of common stock pursuant to exercise of stock options (in shares)			42,998
Net exercise of options			$ 0	(344)	0	0	0	(344)
Issuance of common shares, net of issuance costs			$ 52		86,028	0	0	86,080
Issuance of common shares, net of issuance costs (in shares)			5,175,000
Unrealized comprehensive gain (loss) on marketable securities/short term investments			$ 0	0	0	0	233	233
Stock-based compensation			0	0	4,183	0	0	4,183
Net loss			0	0	0	(18,680)	0	(18,680)
Ending Balance at Jun. 30, 2019			$ 503	$ (344)	$ 392,205	$ (144,004)	$ 144	$ 248,504
Ending Balance (in shares) at Jun. 30, 2019			50,332,435