SHAREHOLDERS' EQUITY (Details) $ / shares in Units, $ in Millions								3 Months Ended			6 Months Ended
	May 23, 2019 USD ($) shares	Mar. 29, 2019 USD ($) $ / shares shares	Dec. 20, 2018 CAD ($)	Dec. 20, 2018 USD ($) $ / shares shares	Nov. 08, 2018 USD ($)	Dec. 19, 2017 CAD ($)	Dec. 19, 2017 USD ($) $ / shares shares	Jun. 30, 2019 USD ($) shares	Mar. 31, 2019 USD ($) shares	Jun. 30, 2018 USD ($) shares	Jun. 30, 2019 CAD ($) shares	Jun. 30, 2019 USD ($) $ / shares shares	Jun. 30, 2018 CAD ($) shares	Jun. 30, 2018 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) shares	Jun. 11, 2018 shares
Shareholders' distributions														$ 1,686,000
Semi-annual shareholders' distribution | $ / shares														0.005
Common stock issued | shares								361,957,000				361,957,000			344,560,000
Weighted average exercise price of stock options (in dollars per share) | $ / shares												$ 1.01		$ 1.14
Shares of common stock issued upon exercise of stock options | shares											257,500	257,500	39,199	39,199
Exercise of stock options								$ 37,000		$ 5,000		$ 260,000		$ 45,000
Proceeds from exercise of stock options												260,000		45,000
Stock-based compensation								136,000		193,000		197,000		396,000
Stock options granted												2,600,000
Restricted cash								13,112,000				13,112,000			$ 14,685,000
Number of units issued | shares	1,935,484	14,193,548
Price per unit | $ / shares		$ 1.55
Net proceeds		$ 20,300,000										22,900,000
Issuance costs	$ 300,000	$ 1,700,000
Flow-through share premium received								2,344,000				2,344,000			2,950,000
Number of warrants received for each share of common stock share sold | shares		0.50
Number of common share per warrant | shares		1
Outstanding warrants								8,064,516		$ 10,350,000		8,064,516		10,350,000
Warrants issued in connection with registered direct offering (note 8)								$ 2,634,000				$ 2,634,000
Black Fox
Common stock issued | shares																178,321
Maximum
Proceeds from exercise of stock options														100,000
Officers, directors and certain employees
Weighted average exercise price of stock options (in dollars per share) | $ / shares												$ 1.67
Common Stock
Shareholders' distributions														$ 1,686,000
Shares of common stock issued upon exercise of stock options | shares								36,000		4,000	258,000	258,000	39,000	39,000
Exercise of stock options								$ 37,000		$ 5,000		$ 260,000		$ 45,000
Stock-based compensation								136,000		$ 193,000		197,000		$ 396,000
Net proceeds												20,300,000
Shares of common stock issued as payment for mining concessions in Mexico | shares										178,000			178,000	178,000
Warrants
Net proceeds												2,600,000
Number of common share per warrant | shares		1
Price per common share for each warrant | $ / shares		$ 2.00
Warrants Expiration Term		3 years
Subscription Receipts
Number of units issued | shares		1,935,484
Price per unit | $ / shares		$ 1.55
Net proceeds	$ 2,600,000
Number of units received upon necessary shareholder and NYSE approvals | shares		1
Flow Through Common Shares
Common stock issued | shares				6,634,000			4,000,000
Restricted cash for exploration activities											$ 17.1	13,100,000
Price per unit | $ / shares				$ 2.24			$ 2.50
Net proceeds			$ 20.0	$ 14,900,000		$ 12.9	$ 10,000,000.0
Flow-through share premium received										$ 3,000,000.0				$ 3,000,000.0	$ 11,900,000
Flow-through share recovery of premium								$ 600,000		$ 1,300,000		600,000		1,300,000
Flow through expenditure incurred											$ 4.6	3,500,000	$ 10.5	$ 8,100,000
ATM offering
Common stock issued | shares									1,010,545
Sale of common stock for cash, net of issuance costs												1,851,000
Aggregate offering price					$ 90,000,000.0
Net proceeds									$ 1,900,000			$ 1,851,000
ATM offering | Common Stock
Number of units issued | shares											1,010,000	1,010,000
Net proceeds												$ 1,851,000