Conditional Asset Retirement Obligation, Measurement Input

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- Definition

ExpectedPeriodRelatedToRemediationExpendituresForEnvironmentalContingencies

+ References

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- Definition

Period For Final Feasibility Study

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- Definition

Time period within which recorded estimate of its obligation may change.

+ References

No definition available.

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- Definition

Total costs accrued as of the balance sheet date for environmental loss contingencies.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
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-SubTopic 30
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- Definition

Increase (decrease) in the accrual for environmental loss contingencies during the reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 5.Y.Q2)
-URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751

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- Definition

The difference between the maximum amount of estimated loss and the amount recorded as of the balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 05
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=99385795&loc=d3e12631-108344

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Environmental Contingency
Environmental accrual increased during the period	$ 3.8
Environmental accrual	$ 18.7	$ 17.0	$ 16.9	$ 16.6
Expected period related to remediation expenditures for environmental contingencies period	30 years
Potential increase in environmental costs	$ 11.6
Time period within which recorded estimate of its obligation may change	12 months
Minimum
Environmental Contingency
Period for final feasibility study	10 months
Maximum
Environmental Contingency
Period for final feasibility study	16 months
Weighted-average Credit-adjusted Risk-free Rate
Environmental Contingency
Weighted-average credit-adjusted risk-free rate (percent)	8.70%	8.70%