Property, Plant, Equipment and Mine Development - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Impaired Long-Lived Assets Held and Used [Line Items]
At-risk assets	$ 388.0		$ 388.0
Asset impairment	$ 0.0	$ 1.7	$ 2.0	$ 1.7

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482740/230-10-45-28

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482130/360-10-45-4

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration