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Pension and Other Postretirement Benefits - Participation in Multi-Employer Pension Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Retirement Benefits [Abstract]
EIN	236648508
PN	499
Pension protection act zone status		Green	Green
Subject to financial improvement/rehabilitation plan	No
Contributions of century aluminum company	$ 0.2	$ 1.6	$ 1.7
Withdrawal from Plan Probable	No
Surcharge Imposed	No
Expiration date of collective bargaining agreement	Mar. 31, 2026

X

- Definition

Whether withdrawal from the multi-employer pension plan is probable.

+ References

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X

- Definition

Indicates certified zone status of multiemployer pension plan determined to be individually significant. Acceptable values are "Green", "Yellow", "Orange", "Red", "Other", and "NA".

+ References

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X

- Definition

Expiration date of collective-bargaining arrangement (CBA) requiring contribution to multiemployer pension plan determined to be individually significant, in YYYY-MM-DD format.

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X

- Definition

Amount of cost for employer contribution to multiemployer pension plan determined to be individually significant.

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- Definition

Employer Identification Number (EIN) or Tax Identification Number (TIN) assigned by Internal Revenue Service (IRS) for multiemployer pension plan determined to be individually significant, in nine-digit numeric format.

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X

- Definition

Indicates whether funding improvement plan or rehabilitation plan was implemented or pending for multiemployer pension plan, determined to be individually significant. Acceptable values are "No", "Pending", "Implemented", "Other", and "NA".

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X

- Definition

Plan number for multiemployer pension plan determined to be individually significant, in three-digit numeric format.

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Indicates whether employer paid surcharge to multiemployer pension plan determined to be individually significant. Acceptable values are "No", "Yes" and "NA".

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