Condensed Statements of Changes in Stockholders’ Equity (Deficit) - USD ($) $ in Thousands	Common Stock Private placement	Common Stock	Additional Paid-in Capital Private placement	Additional Paid-in Capital	Accumulated Deficit	Private placement	Total
Balance at beginning of period at Dec. 31, 2016		$ 17		$ 47,674	$ (27,059)		$ 20,632
Balance at end of period (shares) at Mar. 31, 2017		10,596,838
Balance at beginning of period (shares) at Dec. 31, 2016		9,270,255
Increase (Decrease) in Stockholders' Equity
Issuance of common stock	$ 1		$ 8,978			$ 8,979
Issuance of common stock (in shares)	1,324,256
Issuance of detachable stock warrants in connection with private placement offering			3,562			3,562
Issuance costs			(1,219)			(1,219)
Exercise of stock options				3			3
Exercise of stock options (in shares)		2,327
Share-based compensation - employee				829			829
Share-based compensation - non-employee				7			7
Net loss					(7,496)		(7,496)
Balance at end of period at Mar. 31, 2017		$ 18		59,834	(34,555)		25,297
Balance at beginning of period at Dec. 31, 2016		$ 17		47,674	(27,059)		$ 20,632
Balance at end of period (shares) at Sep. 30, 2017		10,633,042
Balance at beginning of period (shares) at Dec. 31, 2016		9,270,255
Increase (Decrease) in Stockholders' Equity
Exercise of warrants (in shares)							0
Net loss							$ (26,669)
Balance at end of period at Sep. 30, 2017		$ 18		63,659	(53,728)		9,949
Balance at beginning of period at Dec. 31, 2016		$ 17		47,674	(27,059)		20,632
Balance at end of period (shares) at Dec. 31, 2017		10,633,042
Balance at beginning of period (shares) at Dec. 31, 2016		9,270,255
Balance at end of period at Dec. 31, 2017		$ 18		64,397	(60,474)		3,941
Balance at beginning of period at Mar. 31, 2017		$ 18		59,834	(34,555)		25,297
Balance at end of period (shares) at Jun. 30, 2017		10,607,361
Balance at beginning of period (shares) at Mar. 31, 2017		10,596,838
Increase (Decrease) in Stockholders' Equity
Issuance costs			(38)			(38)
Exercise of stock options				10			10
Exercise of stock options (in shares)		10,523
Share-based compensation - employee				2,955			2,955
Share-based compensation - non-employee				8			8
Net loss					(10,502)		(10,502)
Balance at end of period at Jun. 30, 2017		$ 18		62,769	(45,057)		17,730
Balance at end of period (shares) at Sep. 30, 2017		10,633,042
Balance at beginning of period (shares) at Jun. 30, 2017		10,607,361
Increase (Decrease) in Stockholders' Equity
Issuance of detachable stock warrants in connection with private placement offering				156			156
Exercise of warrants (in shares)		15,000
Issuance costs			$ (30)			$ (30)
Exercise of stock options				28			28
Exercise of stock options (in shares)		10,681
Share-based compensation - employee				726			726
Share-based compensation - non-employee				10			10
Net loss					(8,671)		(8,671)
Balance at end of period at Sep. 30, 2017		$ 18		63,659	(53,728)		9,949
Balance at beginning of period at Dec. 31, 2017		$ 18		64,397	(60,474)		3,941
Balance at end of period (shares) at Mar. 31, 2018		14,232,313
Balance at beginning of period (shares) at Dec. 31, 2017		10,633,042
Increase (Decrease) in Stockholders' Equity
Issuance of common stock		$ 4		25,146			$ 25,150
Issuance of common stock (in shares)		3,592,858					3,592,858
Issuance costs				(2,093)			$ (2,093)
Exercise of stock options				23			23
Exercise of stock options (in shares)		6,413
Share-based compensation - employee				1,019			1,019
Share-based compensation - non-employee				1			1
Net loss					(7,224)		(7,224)
Balance at end of period at Mar. 31, 2018		$ 22		88,493	(67,698)		20,817
Balance at beginning of period at Dec. 31, 2017		$ 18		64,397	(60,474)		$ 3,941
Balance at end of period (shares) at Sep. 30, 2018		14,265,411
Balance at beginning of period (shares) at Dec. 31, 2017		10,633,042
Increase (Decrease) in Stockholders' Equity
Exercise of warrants (in shares)							0
Net loss							$ (19,981)
Balance at end of period at Sep. 30, 2018		$ 22		91,286	(80,455)		10,853
Balance at beginning of period at Mar. 31, 2018		$ 22		88,493	(67,698)		20,817
Balance at end of period (shares) at Jun. 30, 2018		14,232,313
Balance at beginning of period (shares) at Mar. 31, 2018		14,232,313
Increase (Decrease) in Stockholders' Equity
Share-based compensation - employee				908			908
Share-based compensation - non-employee				1			1
Net loss					(6,678)		(6,678)
Balance at end of period at Jun. 30, 2018		$ 22		89,402	(74,376)		15,048
Balance at end of period (shares) at Sep. 30, 2018		14,265,411
Balance at beginning of period (shares) at Jun. 30, 2018		14,232,313
Increase (Decrease) in Stockholders' Equity
Issuance of detachable stock warrants in connection with private placement offering				196			196
Exercise of stock options				61			61
Exercise of stock options (in shares)		33,098
Share-based compensation - employee				1,626			1,626
Share-based compensation - non-employee				1			1
Net loss					(6,079)		(6,079)
Balance at end of period at Sep. 30, 2018		$ 22		$ 91,286	$ (80,455)		$ 10,853