Revenue - Schedule of Revenue by Geographic Area (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Disaggregation of Revenue [Line Items]
Net sales	$ 633.9	$ 489.5
United States
Disaggregation of Revenue [Line Items]
Net sales	413.8	300.0
Iceland
Disaggregation of Revenue [Line Items]
Net sales	$ 220.1	$ 189.5

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.

- 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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+ Details

CENTURY ALUMINUM CO 10-Q