SHAREHOLDERS' EQUITY (Details) - USD ($)										3 Months Ended	12 Months Ended
	Feb. 09, 2021	Jan. 29, 2021	Dec. 31, 2020	Sep. 10, 2020	Jun. 25, 2020	Nov. 20, 2019	May 23, 2019	Mar. 29, 2019	Nov. 08, 2018	Mar. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jun. 30, 2021	Jun. 29, 2021	Dec. 31, 2018
Common stock, shares authorized														675,000,000	500,000,000
Number of units issued							1,935,484
Net proceeds							$ 2,600,000						$ 1,851,000
Issuance costs							$ 400,000
Sale of common stock for cash, net of issuance costs											$ 29,875,000		$ 69,467,000
Weighted average exercise price of stock options (in dollars per share)												$ 1.02	$ 1.01
Outstanding options (in shares)			7,012,334								6,171,167	7,012,334	5,269,000			4,243,000
Stock options exercised (in shares)												135,000	535,000
Stock options issued (in shares)											950,000	5,097,000	3,050,000
Acquisition of Mineral Property Interests
Shares issued in connection with acquisitions (in shares)												53,600	353,570
Shares issued in connection with acquisitions												$ 100,000
November 2019 Offering
Number of units issued						37,750,000
Price per unit						$ 1.325
Net proceeds						$ 46,600,000
Warrant expiration term						5 years
Issuance costs						$ 3,500,000
Outstanding warrants											$ 21,706,250
June 2020 Amended and Restated Credit Agreement
Number of units issued					2,091,700
Net proceeds					$ 1,900,000
March 2019 Offering
Number of units issued								14,193,548
Price per unit								$ 1.55
Net proceeds								$ 20,300,000
Number of shares of common stock								1
Number of warrants received for each share of common stock share sold								0.50
Issuance costs								$ 1,700,000
Equity Incentive Plan
Weighted average exercise price of stock options (in dollars per share)												$ 1.02
Stock options exercised (in shares)											0
Stock options issued (in shares)											0	135,000
Officers Directors And Certain Employees
Stock options granted											$ 950,000
Weighted average exercise price of stock options (in dollars per share)											$ 1.22
Equity Financing In February 2021
Number of units issued	30,000,000
Price per unit	$ 1.05
Gross proceeds	$ 31,500,000
Net proceeds	29,900,000
Issuance costs	$ 1,700,000
Equity Financing In February 2021 | Canadian Development Expenses
Gross proceeds											$ 31,500,000
Subscription Receipts | Officers Directors And Certain Employees
Number of units issued								1,935,484
Price per unit								$ 1.55
Common Stock [Member]
Number of units issued													1,010,000
Net proceeds													$ 1,851,000
Shares issued for acquisition of mineral property interests (in shares)												53,000	354,000
Stock options exercised (in shares)												135,000	535,000
Common Stock [Member] | November 2019 Offering
Net proceeds						37,300,000
Warrant | November 2019 Offering
Net proceeds						$ 9,300,000
Number of shares of common stock						1
Number of warrants received for each share of common stock share sold						0.50
Warrant | March 2019 Offering
Warrant expiration term								3 years
Price per common share for each warrant								$ 2.00
Warrant at Second Stock Price | November 2019 Offering
Number of shares of common stock						1
Price per common share for each warrant						$ 1.7225
Flow Through Common Shares | Canadian Development Expenses
Number of units issued		12,600,600
Price per unit		$ 1.01
Gross proceeds		$ 12,700,000									12,700,000
Net proceeds		12,000,000.0
Issuance costs		700,000
Net proceeds allocated to the sale of tax benefits		1,200,000
Sale of common stock for cash, net of issuance costs		$ 10,800,000
Exploration expenditures											12,700,000
Flow Through Common Shares | Canadian Exploration Expenditures
Number of units issued			7,669,900	6,298,166
Price per unit			$ 1.28	$ 1.65								$ 1.28
Gross proceeds				$ 10,400,000
Net proceeds			$ 9,800,000	9,800,000
Issuance costs			0	600,000
Net proceeds allocated to the sale of tax benefits			2,100,000	2,000,000.0
Sale of common stock for cash, net of issuance costs			$ 7,700,000	$ 7,800,000
Exploration expenditures											$ 12,700,000
At-the-market ("ATM")
Number of units issued										1,010,545
Sale of common stock for cash, net of issuance costs										$ 1,900,000
Aggregate offering price									$ 90,000,000.0