Subsequent Events	3 Months Ended
Subsequent Events	Mar. 31, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On April 9, 2021, we completed our private offering of $86.3 million aggregate principal amount of the Convertible Notes. The Convertible Notes were issued at a price of 100% of their aggregate principal amount, will pay interest semi-annually in arrears on May 1 and November 1 of each year, beginning on November 1, 2021, at a rate of 2.75% per annum in cash, and will mature on May 1, 2028, unless earlier converted, repurchased or redeemed. The Convertible Notes are Century’s senior unsecured obligations and rank senior in right of payment to any of Century’s indebtedness that is expressly subordinated in right of payment to the Convertible Notes; equal in right of payment to any of Century’s unsecured indebtedness that is not so subordinated; effectively junior in right of payment to any of Century’s senior, secured indebtedness to the extent of the value of the assets securing such indebtedness; and structurally junior to all indebtedness and other liabilities (including trade payables) of Century’s subsidiaries. On April 14, 2021, we completed our offering of $250.0 million aggregate principal amount of the 2028 Notes. The 2028 Notes bear interest semi-annually in arrears on each April 1 and October 1 of each year, beginning on October 1, 2021, at a rate of 7.5% per year. Concurrently with the closing of the issuance of the 2028 Notes, on April 14, 2021, we accepted for purchase and purchased $195.9 million in aggregate principal amount of the 2025 Notes pursuant to a tender offer commenced in connection with the offering; and we notified the holders of all outstanding 2025 Notes that were not purchased in the tender offer of our election to redeem all such remaining 2025 Notes on May 14, 2021, and deposited with the trustee under the indenture governing the 2025 Notes an amount sufficient to fund the full redemption of the remaining 2025 Notes and discharge our obligations with respect thereto. We applied a portion of net proceeds from the offering of the 2028 Notes described above toward payment of the total consideration amount to holders whose 2025 Notes were accepted and purchased in the tender offer and the remaining proceeds from the issuance of the 2028 Notes and a portion of the net proceeds from the Convertible Notes will be used to fund the redemption of any remaining 2025 Notes, which will be redeemed on May 14, 2021. The remaining proceeds from the Convertible Notes offering were used to repay borrowings under our revolving credit facilities and to pay for the cost of the capped call transactions in connection with the issuance of the Convertible Notes. Based on the characteristics of the 2025 Notes and the 2028 Notes that were issued, the tender and redemption of the 2025 Notes would be accounted for as an extinguishment of the debt. Accordingly, we expect to record a loss on early extinguishment of debt in the second quarter of 2021, consisting of the write-off of deferred financing costs of $4.4 million and the debt discount of $2.2 million associated with the 2025 Notes, as well as the tender fees, including a tender premium of $14.6 million, paid as part of the tender offer. On April 16, 2021, a new, five-year collective bargaining agreement was ratified by the United Steelworkers Local 9423 for the Company's Hawesville, Kentucky smelter. The agreement will run through April 1, 2026.