CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional paid-in capital	Accumulated other comprehensive income	Accumulated deficit
Balance at beginning of period (shares) at Dec. 31, 2017		28,622,886
Balance at beginning of period at Dec. 31, 2017	$ 143,288	$ 29	$ 594,407	$ 9,479	$ (460,627)
Increase (Decrease) in Stockholders' Equity
Net loss for the period	(14,709)				(14,709)
Share-based compensation expense	$ 3,660		3,660
Exercise of options for cash (shares)	402,948	402,948
Exercise of options for cash	$ 5,890		5,890
Unrealized gain (loss) on investments	(288)			(288)
Balance at end of period (shares) at Mar. 31, 2018		29,025,834
Balance at end of period at Mar. 31, 2018	$ 137,841	$ 29	603,957	9,191	(475,336)
Balance at beginning of period (shares) at Dec. 31, 2018	32,538,857	32,538,857
Balance at beginning of period at Dec. 31, 2018	$ 201,576	$ 33	751,109	9,479	(559,045)
Increase (Decrease) in Stockholders' Equity
Net loss for the period	(40,912)				(40,912)
Issuance of common stock, net of issuance costs (shares)		1,854,838
Issuance of common stock, net of issuance costs	107,883	$ 2	107,881
Share-based compensation expense	$ 11,131		11,131
Exercise of options for cash (shares)	235,398	235,398
Exercise of options for cash	$ 2,668		2,668
Net exercise of warrants (shares)	1,400,000	1,400,000
Net exercise of warrants	$ 0	$ 1	(1)
Unrealized gain (loss) on investments	158			158
Proceeds from disgorgement of stockholders' short-swing profits	$ 1,050		1,050
Balance at end of period (shares) at Mar. 31, 2019	36,029,093	36,029,093
Balance at end of period at Mar. 31, 2019	$ 283,554	$ 36	$ 873,838	$ 9,637	$ (599,957)