Fair Value Measurement - Realized Unrealized Derivatives, net (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Realized (loss) gain	$ 777	$ 137	$ 1,423
Unrealized (loss) gain	225	(184)	291
Total realized/ unrealized derivatives, net	1,002	(47)	1,714
Gold
Derivatives, Fair Value [Line Items]
Realized (loss) gain	(47)	623	318
Unrealized (loss) gain		(237)	117
Total realized/ unrealized derivatives, net	(47)	386	435
Silver.
Derivatives, Fair Value [Line Items]
Realized (loss) gain	(44)	344	167
Unrealized (loss) gain	(159)	(244)	208
Total realized/ unrealized derivatives, net	(203)	100	375
Copper
Derivatives, Fair Value [Line Items]
Realized (loss) gain	73	35	17
Unrealized (loss) gain	6	(15)	114
Total realized/ unrealized derivatives, net	79	20	131
Lead
Derivatives, Fair Value [Line Items]
Realized (loss) gain	163	(143)	(44)
Unrealized (loss) gain	(2)	59	(64)
Total realized/ unrealized derivatives, net	161	(84)	(108)
Zinc
Derivatives, Fair Value [Line Items]
Realized (loss) gain	632	(722)	965
Unrealized (loss) gain	380	253	(84)
Total realized/ unrealized derivatives, net	$ 1,012	$ (469)	$ 881

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Net Increase or Decrease in the fair value of the embedded derivative or group of embedded derivatives included in earnings in the period.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 15
-URI http://asc.fasb.org/subtopic&trid=2229187

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The difference between the book value and the sale price of options, swaps, futures, forward contracts, and other derivative instruments. This element refers to the gain (loss) included in earnings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.13(h))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

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The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

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