Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating activities:
Net income (loss)	$ 35,095	$ (9,457)	$ (94,909)
Non-cash elements included in net income (loss):
Depreciation, depletion and amortization	172,651	155,006	196,408
Fair value adjustments, net	15,040	(4,690)	7,079
Adjustment of inventory to net realizable value	6,524	0	1,399
Fee on prepayment of debt with shares of common stock	0	0	2,855
Loss on disposition of properties, plants, equipment and mineral interests	87	572	4,643
Provision for reclamation and closure costs	11,514	6,189	6,914
Deferred income taxes	(48,049)	(3,818)	(29,968)
Stock compensation	6,082	6,458	5,668
Amortization of loan origination fees	1,895	3,666	2,637
Foreign exchange (gain) loss	(79)	2,680	8,025
Other non-cash items	681	1,794	42
Changes in assets and liabilities:
Accounts receivable	(5,405)	(1,080)	(10,939)
Inventories	16,919	(13,208)	16,146
Other current and non-current assets	(1,678)	2,381	15,618
Accounts payable and accrued liabilities	(795)	19,379	(24,355)
Accrued payroll and related benefits	1,270	14,445	9,226
Accrued taxes	6,457	3,561	(3,155)
Accrued reclamation and closure costs and other non-current liabilities	2,128	(3,085)	7,532
Net cash provided by operating activities	220,337	180,793	120,866
Investing activities:
Additions to properties, plants, equipment and mineral interests	(109,048)	(91,016)	(121,421)
Purchase of carbon credits	(869)	0	0
Proceeds from sale or exchange of investments	1,811	0	1,760
Proceeds from disposition of properties, plants, equipment and mineral interests	1,077	331	183
Purchases of investments	0	(2,216)	(389)
Net cash used in investing activities	107,029	92,901	119,867
Financing activities:
Proceeds from issuance of common stock, net of offering costs	0	0	49,019
Dividends paid to common and preferred stockholders	(20,672)	(9,152)	(5,466)
Debt issuance and credit facility fees paid	(116)	(1,356)	(976)
Acquisition of treasury shares from employee equity awards	(4,525)	(2,745)	(2,231)
Borrowings of debt	0	716,327	279,500
Repayments of debt	0	(716,500)	(279,500)
Repayments of finance leases	(7,285)	(5,953)	(7,157)
Net cash (used in) provided by financing activities	(32,598)	(19,379)	33,189
Effect of exchange rates on cash	(530)	(1,107)	875
Net increase in cash, cash equivalents and restricted cash and cash equivalents	80,180	67,406	35,063
Cash, cash equivalents and restricted cash and cash equivalents at beginning of year	130,883	63,477	28,414
Cash, cash equivalents and restricted cash and cash equivalents at end of year	211,063	130,883	63,477
Supplemental disclosure of cash flow information:
Interest	(37,565)	(34,853)	(42,972)
Income and mining taxes	(12,105)	7,913	(3,385)
Significant non-cash investing and financing activities:
Adjustment to common stock and warrants issued for acquisition of another company	0	0	(325)
Addition of finance lease obligations	4,870	9,113	6,506
Recognition of operating lease liabilities and right-of-use assets	4,874	0	22,365
Common stock contributed to pension plans	22,250	16,032	3,600
Common stock issued for 401(k) match	4,339	4,624	3,862
Payment of accrued compensation in restricted stock units	0	5,096	8,274
Common Stocks issued for prepayment of debt	0	0	33,457
Equity securities received from exchange of investments	3,626	0	0
Marketable equity securities received for sale of mineral interest	$ 0	$ 0	$ 2,257