CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional paid-in capital	Accumulated other comprehensive income (loss)	Accumulated deficit
Beginning balance (in shares) at Dec. 31, 2015		19,282,935
Beginning balance at Dec. 31, 2015	$ 118,176	$ 19	$ 415,232	$ 9,558	$ (306,633)
Increase (Decrease) in Stockholders' Equity
Net loss for the year	(83,118)				(83,118)
Share-based compensation expense	10,624		10,624
Issuance of common stock from ESPP	297		297
Issuance of common stock from ESPP (in shares)		28,483
Exercise of options for cash	240		240
Exercise of options for cash (in shares)		22,132
Exercise of warrants for cash	$ 2,115	$ 1	2,114
Exercise of warrants for cash (in shares)	313,756	313,756
Net exercise of warrants	$ 0
Net exercise of warrants (in shares)	603,545	289,789
Unrealized loss on investments	$ (25)			(25)
Ending balance (in shares) at Dec. 31, 2016		19,937,095
Ending balance at Dec. 31, 2016	48,309	$ 20	428,507	9,533	(389,751)
Increase (Decrease) in Stockholders' Equity
Net loss for the year	(70,430)				(70,430)
Share-based compensation expense	6,786		6,786
Issuance of common stock and warrants, net of issuance costs	153,530	$ 8	153,522
Issuance of common stock and warrants, net of issuance costs (shares)		7,941,688
Issuance of common stock from ESPP	144		144
Issuance of common stock from ESPP (in shares)		59,976
Exercise of options for cash	399		399
Exercise of options for cash (in shares)		45,573
Exercise of warrants for cash	$ 4,604	$ 1	4,603
Exercise of warrants for cash (in shares)	585,729	585,729
Net exercise of warrants	$ 0
Net exercise of warrants (in shares)	638,554	52,825
Unrealized loss on investments	$ (54)			(54)
Ending balance (in shares) at Dec. 31, 2017	28,622,886	28,622,886
Ending balance at Dec. 31, 2017	$ 143,288	$ 29	594,407	9,479	(460,627)
Increase (Decrease) in Stockholders' Equity
Net loss for the year	(98,418)				(98,418)
Share-based compensation expense	15,854		15,854
Issuance of common stock and warrants, net of issuance costs	130,663	$ 3	130,660
Issuance of common stock and warrants, net of issuance costs (shares)		3,162,500
Issuance of common stock from ESPP	442		442
Issuance of common stock from ESPP (in shares)		21,536
Exercise of options for cash	$ 9,747	$ 1	9,746
Exercise of options for cash (in shares)	731,935	731,935
Unrealized loss on investments	$ 0
Ending balance (in shares) at Dec. 31, 2018	32,538,857	32,538,857
Ending balance at Dec. 31, 2018	$ 201,576	$ 33	$ 751,109	$ 9,479	$ (559,045)