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Commitments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating leases
2021	$ 16.8
2022	15.9
2023	15.4
2024	14.9
2025	14.2
Rental expense for noncancelable operating leases	$ 24.9	$ 21.6
Rental expense for noncancelable operating leases			$ 15.2
Take-Or-Pay Contracts
Other Commitments [Line Items]
Term of take-or-pay contract	9 years 9 months 18 days
Minimum annual payments under take-or-pay contracts, fiscal year maturity
2021	$ 9.1
2022	4.0
2023	4.0
2024	4.0
2025	4.0
Capital Addition Purchase Commitments
Other Commitments [Line Items]
Commitments for capital expenditures	286.8
Construction in Progress
Other Commitments [Line Items]
Commitments for capital expenditures	278.3
Building Improvements
Other Commitments [Line Items]
Commitments for capital expenditures	$ 4.1

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- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

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-Publisher FASB
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-Topic 842
-SubTopic 20
-Section 50
-Paragraph 6
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Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

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Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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The minimum amount the entity agreed to spend under the long-term purchase commitment.

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Period covered by the long-term purchase commitment, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount of operating lease expense. Excludes sublease income.

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Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

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Amount of fixed and determinable portion of unrecorded unconditional purchase obligation to be paid in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

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Amount of fixed and determinable portion of unrecorded unconditional purchase obligation to be paid in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of fixed and determinable portion of unrecorded unconditional purchase obligation to be paid in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of fixed and determinable portion of unrecorded unconditional purchase obligation to be paid in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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