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Related Party Transactions - Narrative (Details) carbon_credit in Thousands, € in Millions, $ in Millions		1 Months Ended			3 Months Ended		6 Months Ended
	Dec. 21, 2023 EUR (€) € / carbonCredit	Mar. 31, 2024 EUR (€) € / carbonCredit	Dec. 31, 2023 EUR (€) carbon_credit € / carbonCredit	Sep. 30, 2023 EUR (€) carbon_credit € / carbonCredit	Jun. 30, 2024 USD ($) € / carbonCredit	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($) € / carbonCredit	Jun. 30, 2023 USD ($)	Dec. 09, 2022 USD ($)
Related Party Transaction [Line Items]
Revenue | $					$ 560.8	$ 575.5	$ 1,050.3	$ 1,127.9
Vlissingen facility agreement | Affiliated Entity | Vlissingen
Related Party Transaction [Line Items]
Credit facility maximum amount | $									$ 90.0
Stated interest rate, percentage									8.75%
Carbon Credit Sale | Affiliated Entity | Grundartangi
Related Party Transaction [Line Items]
Carbon credit sold in transaction | carbon_credit				390
Sale price (Euro per carbon credit)				82.18
Aggregate amount | €				€ 32.1
Carbon Credit Repurchase | Affiliated Entity | Grundartangi
Related Party Transaction [Line Items]
Sale price (Euro per carbon credit)	83.72	87.01	85.13
Aggregate amount | €	€ 32.7	€ 33.9	€ 33.2
Second Repurchase Agreement, Carbon Credit Sale | Affiliated Entity | Grundartangi
Related Party Transaction [Line Items]
Carbon credit sold in transaction | carbon_credit			40
Sale price (Euro per carbon credit)			69.30
Second Repurchase Agreement, Carbon Credit Repurchase | Affiliated Entity | Grundartangi
Related Party Transaction [Line Items]
Sale price (Euro per carbon credit)			70.71		72.59		72.59
Aggregate amount | €		€ 2.9	€ 2.8
Supply Commitment | Glencore
Related Party Transaction [Line Items]
Revenue | $					$ 50.3	$ 65.8	$ 85.8	$ 86.8
Consolidated sales | Customer concentration risk | Glencore
Related Party Transaction [Line Items]
Major customer, percentage of revenue, net (percent)					58.00%	74.00%	61.00%	74.00%
Glencore
Related Party Transaction [Line Items]
Ownership percentage by noncontrolling owners					42.90%		42.90%
Economic ownership percentage by related party					45.90%		45.90%

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