Debt Instrument, Term Extension

No definition available.

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- Definition

Debt Instrument, Variable Interest Rate

+ References

No definition available.

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- Definition

The percentage of common stock and preferred stock of the company owned by a related party.

+ References

No definition available.

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- Definition

Related Party Transaction, Carbon Credit Amount

+ References

No definition available.

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- Definition

Related Party Transaction, Carbon Credit, Price Per Credit

+ References

No definition available.

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

+ References

No definition available.

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- Definition

Amount of transactions with related party during the financial reporting period.

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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.

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- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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Related Party Transactions - Narrative (Details) € in Millions, $ in Millions		1 Months Ended				3 Months Ended		9 Months Ended
	Oct. 01, 2024 USD ($)	Dec. 31, 2024 EUR (€) carbon_credit € / carbonCredit	Aug. 31, 2024 EUR (€) carbon_credit € / carbonCredit	Dec. 31, 2023 EUR (€) carbon_credit € / carbonCredit	Sep. 30, 2023 EUR (€) carbon_credit € / carbonCredit	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Aug. 31, 2025 carbon_credit
Related Party Transaction [Line Items]
Net sales \| $						$ 632.2	$ 539.1	$ 1,894.2	$ 1,589.4
Vlissingen \| Vlissingen Credit Facility \| Affiliated Entity
Related Party Transaction [Line Items]
Term extension	2 years
Credit facility maximum amount \| $	$ 90.0
Stated interest rate, percentage	8.75%
Debt instrument, basis spread on variable rate	3.687%
Vlissingen \| Vlissingen Credit Facility \| Affiliated Entity \| Maximum
Related Party Transaction [Line Items]
Variable interest rate	9.00%
Vlissingen \| Vlissingen Credit Facility \| Affiliated Entity \| Minimum
Related Party Transaction [Line Items]
Variable interest rate	7.00%
Grundartangi \| Carbon Credit Sale \| Affiliated Entity
Related Party Transaction [Line Items]
Carbon credit sold in transaction		370,700			390,000
Sale price (Euro per carbon credit) \| € / carbonCredit					82.18
Aggregate amount \| €					€ 32.1
Grundartangi \| Carbon Credit Repurchase \| Affiliated Entity
Related Party Transaction [Line Items]
Sale price (Euro per carbon credit) \| € / carbonCredit		69.16			83.72
Aggregate amount \| €		€ 25.6			€ 32.7
Grundartangi \| Repurchase Agreement, Carbon Credits Settled \| Affiliated Entity
Related Party Transaction [Line Items]
Carbon credit sold in transaction		19,300								370,700
Grundartangi \| Second Repurchase Agreement \| Affiliated Entity
Related Party Transaction [Line Items]
Carbon credit sold in transaction			59,300
Sale price (Euro per carbon credit) \| € / carbonCredit			186.74
Aggregate amount \| €			€ 11.1
Grundartangi \| Carbon Credit Sale \| Affiliated Entity
Related Party Transaction [Line Items]
Carbon credit sold in transaction				40,000
Sale price (Euro per carbon credit) \| € / carbonCredit				69.30
Grundartangi \| Carbon Credit Repurchase \| Affiliated Entity
Related Party Transaction [Line Items]
Sale price (Euro per carbon credit) \| € / carbonCredit				70.71
Aggregate amount \| €				€ 2.8
Grundartangi \| Carbon Credit Increase \| Affiliated Entity
Related Party Transaction [Line Items]
Carbon credit sold in transaction			19,300
Grundartangi \| Carbon Credit Settled \| Affiliated Entity
Related Party Transaction [Line Items]
Carbon credit sold in transaction			59,300
Glencore \| Supply Commitment
Related Party Transaction [Line Items]
Net sales \| $						$ 34.8	$ 31.5	$ 161.2	$ 117.3
Glencore \| Consolidated sales \| Customer concentration risk
Related Party Transaction [Line Items]
Major customer, percentage of revenue, net (percent)						50.60%	61.60%	56.30%	61.00%
Century Aluminum \| Glencore
Related Party Transaction [Line Items]
Ownership percentage by noncontrolling owners						42.90%		42.90%
Economic ownership percentage by related party						45.80%		45.80%