CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock Lexam VG Gold	Common Stock	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit	Flow Through Common Shares	Lexam VG Gold	Total
Balance at Dec. 31, 2015		$ 1,359,144	$ (825)	$ (940,027)			$ 418,292
Balance (in shares) at Dec. 31, 2015		298,634
Increase (Decrease) in Shareholders' Equity
Stock-based compensation (note 11)		$ 1,039					1,039
Exercise of stock options (note 11)		$ 3,730					$ 3,730
Exercise of stock options (note 11) (in shares)		1,494					1,457
Other-than-temporary impairment on marketable equity securities (note 3)			882				$ 882
Share repurchase (note 10)		$ (582)					(582)
Share repurchase (note 10) (in shares)		(558)
Shareholder distributions (note 10)		$ (2,986)					(2,986)
Unrealized gain (loss) on available-for-sale securities (note 3)			1,609				1,609
Net (loss) income				21,055			21,055
Balance at Dec. 31, 2016		$ 1,360,345	1,666	(918,972)			443,039
Balance (in shares) at Dec. 31, 2016		299,570
Increase (Decrease) in Shareholders' Equity
Stock-based compensation (note 11)		$ 1,311					1,311
Shares issued for cash (note 10 and note 19)		$ 39,397			$ 7,799		39,397
Shares issued for cash (note 10 and note 19) (in shares)		20,700			4,000
Shares issued in connection with acquisitions (note 10)	$ 38,141					$ 38,141
Shares issued in connection with acquisitions (note 10) (in shares)	12,687
Exercise of stock options (note 11)		$ 122					$ 122
Exercise of stock options (note 11) (in shares)		94					94
Other-than-temporary impairment on marketable equity securities (note 3)			356				$ 356
Shareholder distributions (note 10)		$ (3,059)					(3,059)
Reclassification of unrealized gain on marketable securities disposed of during the period, net of taxes (note 3)			(840)				(840)
Unrealized gain (loss) on available-for-sale securities (note 3)			1,818				1,818
Net (loss) income				(10,634)			(10,634)
Balance at Dec. 31, 2017		$ 1,447,879	3,000	(929,606)			521,273
Balance (in shares) at Dec. 31, 2017		337,051
Increase (Decrease) in Shareholders' Equity
Warrants issued in connection with the equity issuance (note 10)		$ 3,823					3,823
Balance at Dec. 31, 2017		1,447,879		(926,606)			521,273
Increase (Decrease) in Shareholders' Equity
Stock-based compensation (note 11)		269					269
Shares issued for cash (note 10 and note 19)		$ 918			$ 11,145		918
Shares issued for cash (note 10 and note 19) (in shares)		515			6,634
Shares issued in connection with acquisitions (note 10)		$ 391					391
Shares issued in connection with acquisitions (note 10) (in shares)		178
Exercise of stock options (note 11)		$ 192					$ 192
Exercise of stock options (note 11) (in shares)		182					171
Share repurchase (note 10) (in shares)							0
Shareholder distributions (note 10)		$ (3,372)					$ (3,372)
Net (loss) income				(44,870)			(44,870)
Balance at Dec. 31, 2018		$ 1,457,422		(971,476)			$ 485,946
Balance (in shares) at Dec. 31, 2018		344,560
Increase (Decrease) in Shareholders' Equity
Adoption of ASU 2016-01 (note 2 and note 3) | Accounting Standards Update 2016-01			$ (3,000)	$ 3,000