CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock and Additional Paid-in Capital Flow-through common shares	Common Stock and Additional Paid-in Capital	Accumulated Deficit	Flow-through common shares	Total
Balance at Dec. 31, 2019		$ 1,530,702	$ (1,031,223)		$ 499,479
Balance (in shares) at Dec. 31, 2019		400,339,000
Increase (Decrease) in Shareholders' Equity
Stock-based compensation		$ 88			88
Exercise of stock options		$ 62			$ 62
Exercise of stock options (in shares)		60,000			60,000
Net loss			(99,191)		$ (99,191)
Balance at Mar. 31, 2020		$ 1,530,852	(1,130,414)		400,438
Balance (in shares) at Mar. 31, 2020		400,399,000
Balance at Dec. 31, 2020		$ 1,548,876	(1,183,548)		365,328
Balance (in shares) at Dec. 31, 2020		416,587,000
Increase (Decrease) in Shareholders' Equity
Stock-based compensation		$ 227			$ 227
Exercise of stock options (in shares)					0
Stock issued during the period	$ 10,785	$ 29,875		$ 10,785	$ 29,875
Stock issued during the period (in shares)	12,601,000	30,000,000
Net loss			(12,466)		(12,466)
Balance at Mar. 31, 2021		$ 1,589,763	$ (1,196,014)		$ 393,749
Balance (in shares) at Mar. 31, 2021		459,188,000