Capital Stock - Stockholders' Equity (Details) - USD ($) $ in Thousands	1 Months Ended	9 Months Ended
	Apr. 30, 2017	Sep. 30, 2017	Sep. 30, 2016
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' equity beginning balance		$ 19,099	$ 22,879
Exercise of stock options (shares)		63,509	361,145
Exercise of stock options		$ 175	$ 939
Release of stock awards		0	0
Employee stock-based compensation		5,212	3,861
Issuance of common stock, net of issuance costs (shares)	6,300,000
Issuance of common stock, net of issuance costs		23,230
Cancelled shares		(1,670)	(1,523)
Total comprehensive loss		(23,953)	(3,320)
Stockholders' equity ending balance		$ 22,092	$ 22,836
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (shares)		41,255,000	40,343,000
Stockholders' equity beginning balance		$ 4	$ 4
Exercise of stock options (shares)		64,000	361,000
Release of stock awards (shares)		1,096,000	911,000
Issuance of common stock, net of issuance costs (shares)		6,325,000
Issuance of common stock, net of issuance costs		$ 1
Cancelled shares (shares)		(397,000)	(397,000)
Ending balance (shares)		48,343,000	41,218,000
Stockholders' equity ending balance		$ 5	$ 4
Additional Paid-in Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' equity beginning balance		311,164	305,981
Exercise of stock options		175	939
Release of stock awards		0	0
Employee stock-based compensation		5,212	3,861
Issuance of common stock, net of issuance costs		23,229
Cancelled shares		(1,670)	(1,523)
Stockholders' equity ending balance		338,110	309,258
Accumulated Other Comprehensive Income (Loss) [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' equity beginning balance		0	405
Total comprehensive loss		13	(22)
Stockholders' equity ending balance		13	383
Accumulated Deficit [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' equity beginning balance		(292,069)	(283,511)
Total comprehensive loss		(23,966)	(3,298)
Stockholders' equity ending balance		$ (316,036)	$ (286,809)