Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Common Stock	Deficit	Accumulated other comprehensive income	Total shareholders' equity	Non-controlling interests
Beginning Balance (in shares) at Dec. 31, 2013		19,601,251
Beginning Balance at Dec. 31, 2013	$ 184,233	$ 258,109	$ (73,256)	$ (620)	$ 184,233	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(86,635)		(86,635)		(86,635)	0
Other comprehensive income	$ 1,205			1,205	1,205
Shares issued for exercise of stock options (in shares)	15,000	15,000
Shares issued for exercise of stock options (Note 15)	$ 120	$ 120			120
Shares issued for exercise of share purchase warrants (in shares)	49,273	61,301
Shares issued for exercise of share purchase warrants	$ 483	$ 483			483
Share-based compensation (Note 15)	$ 1,405	$ 1,405			1,405
Share issued for property acquisitions (in shares)	0
Share issued for property acquisitions	$ 0
Shares issued for consulting services	0
Ending Balance (in shares) at Dec. 31, 2014		19,677,552
Ending Balance at Dec. 31, 2014	100,811	$ 260,117	(159,891)	585	100,811	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(82,357)		(82,217)		(82,217)	(140)
Other comprehensive income	$ 2,920			2,920	2,920
Shares issued for exercise of stock options (in shares)	48,802	48,802
Shares issued for exercise of stock options (Note 15)	$ 185	$ 185			185
Shares issued for exercise of share purchase warrants (in shares)	173	300
Shares issued for exercise of share purchase warrants	$ 2	$ 2			2
Share-based compensation (Note 15)	1,099	$ 1,099			1,099
Shares issued in connection with the acquisition of Uranerz Energy Corporation (in shares)		25,347,209
Shares issued in connection with the acquisition of Uranerz Energy Corporation	105,673	$ 105,673			105,673
Options issued in connection with the acquisition of Uranerz Energy Corporation (in shares)		0
Options issued in connection with the acquisition of Uranerz Energy Corporation	3,681	$ 3,681			3,681
Shares issued for cash by at-the-market offering (in shares)		1,275,908
Shares issued for cash by at-the-market offering (Note 13a)	$ 2,939	$ 2,939			2,939
Share issued for property acquisitions (in shares)	13,654,488	169,361
Share issued for property acquisitions	$ 550	$ 550			550
Share issuance cost	(312)	$ (312)			(312)
Non-controlling interest upon acquisition of Uranerz Energy Corporation	3,992					3,992
Contributions attributable to non-controlling interest	304					304
Shares issued for consulting services	0
Ending Balance (in shares) at Dec. 31, 2015		46,519,132
Ending Balance at Dec. 31, 2015	139,487	$ 373,934	(242,108)	3,505	135,331	4,156
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(39,864)		(39,413)		(39,413)	(451)
Other comprehensive income	$ (197)			(197)	(197)
Shares issued for exercise of stock options (in shares)	8,369	8,369
Shares issued for exercise of stock options (Note 15)	$ 18	$ 18			18
Shares issued for exercise of share purchase warrants (in shares)	0
Share-based compensation (Note 15)	$ 2,657	$ 2,657			2,657
Shares issued for cash by at-the-market offering (in shares)		200,225
Shares issued for cash by at-the-market offering (Note 13a)	$ 539	$ 539			539
Share issued for property acquisitions (in shares)	0
Share issuance cost	$ (2,330)	$ (2,330)			(2,330)
Contributions attributable to non-controlling interest	37					37
Shares issued for public offering (in shares)		13,368,750
Shares issued for public offerings (Note 13b, 13e)	22,980	$ 22,980			22,980
Shares issued for the vesting of restricted stock units (in shares)		138,608
Shares issued for acquistion of Alta Mesa (in shares)		4,551,284
Shares issued for acquisition of Alta Mesa (Note 4, 13d)	11,378	$ 11,378			11,378
Shares issued for acquisition of 40% Roca Honda (in shares)		1,212,173
Shares issued for acquisition of 40% interest in Roca Honda (Note 13c)	2,679	$ 2,679			2,679
Shares issued for consulting services (in shares)		206,612
Shares issued for consulting services	479	$ 479			479
Ending Balance (in shares) at Dec. 31, 2016		66,205,153
Ending Balance at Dec. 31, 2016	$ 137,863	$ 412,334	$ (281,521)	$ 3,308	$ 134,121	$ 3,742