Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Activities
Net income (loss)	$ 42,482,000	$ (777,967,000)	$ 38,690,000
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depletion, depreciation and accretion (Note 5 and 10)	139,874,000	164,233,000	225,033,000
Goodwill impairment (Note 6)	0	102,581,000	0
Asset impairment (Note 6)	0	564,495,000	0
Deferred tax (recovery) expense (Note 13)	(23,825,000)	(76,148,000)	40,227,000
Stock-based compensation (Note 9)	8,396,000	1,216,000	1,430,000
Amortization of debt issuance costs (Note 8)	3,809,000	3,625,000	3,376,000
Non-cash lease expenses	1,667,000	1,951,000	1,806,000
Lease payments	(1,621,000)	(1,926,000)	(1,969,000)
Unrealized foreign exchange loss	21,879,000	5,271,000	1,803,000
Derivative instruments loss (Note 15)	48,838,000	4,100,000	3,669,000
Cash settlement on derivatives instruments (Note 15)	(58,427,000)	4,874,000	(3,273,000)
Other financial instruments loss (gain) (Note 15)	3,369,000	46,882,000	(49,884,000)
Cash settlement of asset retirement obligation (Note 10)	(805,000)	(201,000)	(870,000)
Other non-cash loss	44,000	2,026,000	0
Loss on redemption of Convertible Notes	0	0	11,501,000
Net change in assets and liabilities from operating activities (Note 16)	59,154,000	36,062,000	(93,874,000)
Net cash provided by operating activities	244,834,000	81,074,000	177,665,000
Investing Activities
Additions to property, plant and equipment (Note 5)	(149,879,000)	(96,281,000)	(379,314,000)
Property acquisitions (Note 5)	0	0	(77,772,000)
Proceeds on disposition of investment, net of transaction costs (Note 15)	43,126,000	0	0
Changes in non-cash investing working capital	1,431,000	(48,642,000)	(7,851,000)
Net cash used in investing activities	(105,322,000)	(144,923,000)	(464,937,000)
Financing Activities
Proceeds from issuance of Senior Notes, net of issuance costs (Note 8)	0	0	289,271,000
Proceeds from bank debt, net of issuance costs	(228,000)	88,332,000	342,575,000
Repayment of debt	(122,500,000)	(17,000,000)	(349,219,000)
Lease payments	(2,182,000)	(879,000)	0
Proceeds from exercise of stock options	100,000	0	0
Repurchase of shares of Common Stock (Note 9)	0	0	(37,561,000)
Net cash (used in) provided by financing activities	(124,810,000)	70,453,000	245,066,000
Foreign exchange loss on cash and cash equivalents and restricted cash and cash equivalents	(821,000)	(156,000)	(1,027,000)
Net increase (decrease) in cash and cash equivalents and restricted cash and cash equivalents	13,881,000	6,448,000	(43,233,000)
Cash and cash equivalents and restricted cash and cash equivalents, beginning of year (Note 16)	17,523,000	11,075,000	54,308,000
Cash and cash equivalents and restricted cash and cash equivalents, end of year (Note 16)	$ 31,404,000	$ 17,523,000	$ 11,075,000