Century Aluminum (CENX) 10-Q 4 May 20 2020 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	3 Months Ended
	Mar. 31, 2020	Apr. 30, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Entity File Number	001-34474
Entity Registrant Name	Century Aluminum Company
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	13-3070826
Entity Address, Address Line One	One South Wacker Drive
Entity Address, Address Line Two	Suite 1000
Entity Address, City or Town	Chicago
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60606
City Area Code	312
Local Phone Number	696-3101
Title of 12(b) Security	Common Stock, $0.01 par value per share
Entity Trading Symbol	CENX
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		89,460,965
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Central Index Key	0000949157
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
NET SALES
Related parties	$ 271	$ 311.3
Other customers	150.2	178.7
Total net sales	421.2	490
Cost of goods sold	416.4	502.8
Gross profit (loss)	4.8	(12.8)
Selling, general and administrative expenses	8.9	14.7
Other operating expense, net	0.3	0.3
Operating income (loss)	(4.4)	(27.8)
Interest expense - term loan	(0.7)	0
Interest expense	(6)	(5.8)
Interest income	0.1	0.2
Net gain (loss) on forward and derivative contracts	3.8	(5.7)
Other income (expense) - net	1.7	1.1
Income (loss) before income taxes and equity in earnings of joint ventures	(5.5)	(38)
Income tax benefit (expense)	2.8	2.9
Income (loss) before equity in earnings of joint ventures	(2.7)	(35.1)
Equity in earnings of joint ventures	0	0.5
Net income (loss)	$ (2.7)	$ (34.6)
EARNINGS (LOSS) PER COMMON SHARE:
Basic and diluted (per share)	$ (0.03)	$ (0.39)
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING:
Basic and diluted (per share)	89.3	88.1

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Comprehensive income (loss):
Net income (loss)	$ (2.7)	$ (34.6)
Other comprehensive income before income tax effect:
Net income (loss) on foreign currency cash flow hedges reclassified as income	0	0
Defined benefit plans and other postretirement benefits:
Amortization of prior service benefit (cost) during the period	(0.8)	(1.3)
Amortization of net gain (loss) during the period	2.5	1.9
Other comprehensive income (loss) before income tax effect	1.7	0.6
Income tax effect	(0.3)	(0.3)
Other comprehensive income (loss)	1.4	0.3
Total comprehensive income (loss)	$ (1.3)	$ (34.3)

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
ASSETS
Cash and cash equivalents	$ 147.6	$ 38.9
Restricted cash	1.8	0.8
Accounts receivable - net	52.9	70.1
Due from affiliates	17.8	30.1
Inventories	317.6	320.6
Derivative assets	32.7	14.6
Prepaid and other current assets	13.4	12.2
Total current assets	583.8	487.3
Property, plant and equipment - net	935.4	949.2
Due from affiliates - less current portion	5.1	0.5
Other assets	66.8	62.7
TOTAL	1,591.1	1,499.7
LIABILITIES:
Accounts payable, trade	87.1	97.1
Due to affiliates	29.5	32.9
Accrued and other current liabilities	50.6	57.2
Derivative liabilities	34.5	4.3
Accrued employee benefits costs	10.4	10.4
Hawesville term loan	20	20
U.S. revolving credit facility	45	4
Industrial revenue bonds	7.8	7.8
Total current liabilities	284.9	233.7
Senior notes payable	249.3	249.2
Hawesville term loan - less current portion	15	20
Iceland revolving credit facility	45	0
Accrued pension benefits costs - less current portion	59.3	60.8
Accrued postretirement benefits costs - less current portion	100.1	100.7
Other liabilities	47.1	42.4
Leases - right of use liabilities	21.9	22.8
Deferred taxes	94.7	95.1
Total noncurrent liabilities	632.4	591
COMMITMENTS AND CONTINGENCIES	0	0
SHAREHOLDERS’ EQUITY:
Preferred stock	0	0
Common stock	1	1
Additional paid-in capital	2,526.6	2,526.5
Treasury stock, at cost	(86.3)	(86.3)
Accumulated other comprehensive loss	(108.4)	(109.8)
Accumulated deficit	(1,659.1)	(1,656.4)
Total shareholders’ equity	673.8	675
TOTAL	$ 1,591.1	$ 1,499.7

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ (2.7)	$ (34.6)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Unrealized (gain) loss on derivative instruments	(3.7)	5.6
Lower of cost or NRV inventory adjustment	13.4	0
Depreciation and amortization	20.2	24.3
Other non-cash items - net	(0.7)	(4.5)
Change in operating assets and liabilities:
Accounts receivable - net	17.2	(8.4)
Due from affiliates	20.2	(1.1)
Inventories	(10.4)	16.4
Prepaid and other current assets	0.1	2.6
Accounts payable, trade	(11.3)	(10.2)
Due to affiliates	(3.2)	(7.2)
Accrued and other current liabilities	(5.6)	(3.8)
Other - net	1.1	(0.6)
Net cash provided by (used in) operating activities	34.6	(21.5)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property, plant and equipment	(6)	(10.6)
Proceeds from sales of property, plant & equipment	0.1	0
Net cash provided by (used in) investing activities	(5.9)	(10.6)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repayments on term loan	(5)	0
Borrowings under revolving credit facilities	121.8	169.6
Repayments under revolving credit facilities	(35.8)	(157.6)
Other short-term borrowings	0	3.4
Net cash provided by (used in) financing activities	81	15.4
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	109.7	(16.7)
Cash, cash equivalents and restricted cash, beginning of period	39.7	39.7
Cash, cash equivalents and restricted cash, end of period	149.4	23
Cash paid for:
Interest	0.8	0.4
Taxes	0	0.1
Non-cash investing activities:
Capital expenditures	$ 1.2	$ 4

CONSOLIDATED STATEMENTS OF SHAR

CONSOLIDATED STATEMENTS OF SHAREHOLDERS’ EQUITY - USD ($) $ in Millions	Total	Preferred stock [Member]	Common stock [Member]	Additional paid-in capital [Member]	Treasury stock, at cost [Member]	Accumulated other comprehensive loss [Member]	Accumulated deficit [Member]
Balance, start at Dec. 31, 2018	$ 762.2	$ 0	$ 1	$ 2,523	$ (86.3)	$ (98.7)	$ (1,576.8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(34.6)						(34.6)
Other comprehensive income (loss)	0.3					0.3
Share-based compensation	0.3		0	0.3
Conversion of preferred stock to common stock	0	0	0	0
Balance, end at Mar. 31, 2019	728.1	0	1	2,523.3	(86.3)	(99.7)	(1,610.1)
Balance, start at Dec. 31, 2019	675	0	1	2,526.5	(86.3)	(109.8)	(1,656.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(2.7)						(2.7)
Other comprehensive income (loss)	1.4					1.4
Share-based compensation	0.1	0	0	0.1
Conversion of preferred stock to common stock	0	0	0	0
Balance, end at Mar. 31, 2020	$ 673.8	$ 0	$ 1	$ 2,526.6	$ (86.3)	$ (108.4)	$ (1,659.1)

General

General	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
General	General The accompanying unaudited interim consolidated financial statements of Century Aluminum Company should be read in conjunction with the audited consolidated financial statements for the year ended December 31, 2019 . In management’s opinion, the unaudited interim consolidated financial statements reflect all adjustments, which are of a normal and recurring nature, that are necessary for a fair presentation of financial results for the interim periods presented. Operating results for the first three months of 2020 are not necessarily indicative of the results that may be expected for the year ending December 31, 2020. Throughout this Form 10-Q, and unless expressly stated otherwise or as the context otherwise requires, "Century Aluminum," "Century," the "Company," "we," "us," "our" and "ours" refer to Century Aluminum Company and its consolidated subsidiaries. Recently Adopted Accounting Standards On January 1, 2020, we adopted Financial Accounting Standards Board (“FASB”) Accounting Standards Update (“ASU”) 2016-13, “Measurement of Credit Losses on Financial Instruments.” The ASU added an impairment model known as the current expected credit loss ("CECL") model, which is based on expected losses rather than incurred losses. The CECL model is applicable to our receivables, both from related parties and third-party customers related to the sale of primary aluminum (collectively, “trade receivables”). We do not have any other financial instruments or assets to which the CECL model applies. The adoption of the CECL model did not have a material impact on the Company’s consolidated financial statements. On January 1, 2020, we adopted FASB ASU 2018-13, “Disclosure Framework- Changes to the Disclosure Requirements for Fair Value Measurement” which changed the fair value measurement disclosure requirements of ASC 820. The additional disclosures include a requirement to disclose the range and weighted average used to develop significant unobservable inputs for Level 3 fair value measurements. The new framework also eliminates and modifies certain other fair value disclosures. See Note 4. Fair Value Measurement for updated fair value disclosures in connection with the adoption of this accounting standard. Recently Issued Accounting Standards In December 2019, the FASB issued ASU 2019-12, “Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes." Amendments include the removal of certain exceptions to the general principles of ASC 740 and to improve and simplify accounting for income taxes by clarifying and amending existing guidance. Updates are related to intraperiod tax allocation, interim period tax calculations, tax laws or rate changes in interim periods, and income taxes related to employee stock ownership plans. The ASU is effective for fiscal years beginning after December 15, 2020, including interim periods therein and early adoption is permitted. The Company is currently evaluating the impacts of ASU 2019-12 and we do not expect the adoption to have a material effect on the consolidated financial statements. In March 2020, the Securities and Exchange Commission (“SEC”) issued a final rule that amends the disclosure requirements related to certain registered securities under SEC Regulation S-X Rule 3-10 with respect to the disclosure requirements related to issuers and guarantors of guaranteed debt securities. The final rule allows registrants to provide alternative financial disclosures in either the registrant’s MD&A or financial statements, rather than the previous requirement under Rule 3-10, which required condensed consolidating financial information within the financial statements. It also simplifies the requirements in Rule 3-10 that currently must be met for a parent company to qualify for exceptions allowing it to provide alternative disclosures rather than full audited financial statements. The ruling also reduces the periods for which summarized financial information is required to be presented to the most recent (1) annual period and (2) year-to-date interim period. The final rule applies to annual reports on Form 10-K for fiscal years ending after January 4, 2021 and quarterly reports on Form 10-Q for quarterly periods ending after January 4, 2021 and registrants may voluntarily comply with the final rule before the effective date. The Company does not expect the future adoption, which is limited to disclosures only, to have a material effect on the Company’s consolidated financial statements.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions The significant related party transactions occurring during the three months ended March 31, 2020 and 2019 are described below. We believe all of our transactions with Glencore and BHH are at prices that approximate market. Glencore ownership As of March 31, 2020 , Glencore plc and its affiliates (together "Glencore") beneficially owned 42.9% of Century’s outstanding common stock ( 46.8% on a fully-diluted basis assuming the conversion of all of the Series A Convertible Preferred Stock) and all of our outstanding Series A Convertible Preferred Stock. See Note 6. Shareholders' Equity for a description of our outstanding Series A Convertible Preferred Stock. From time to time, Century and Glencore enter into various transactions for the purchase and sale of primary aluminum, purchase and sale of alumina, tolling agreements, certain forward financial contracts and loan agreements. Sales to Glencore For the three months ended March 31, 2020 and 2019, approximately 64% of our consolidated net sales were made to Glencore. Glencore purchases aluminum produced at our U.S smelters at prices based on the London Metal Exchange (the "LME") plus the Midwest regional delivery premium plus any additional market-based product premiums. Glencore purchases aluminum produced at our Grundartangi, Iceland smelter at prices based on the LME plus the European Duty Paid premium plus any additional market-based product premiums. We have also entered into agreements with Glencore pursuant to which we sell certain amounts of alumina at prices that approximate market. For the three months ended March 31, 2020 , we recorded $0.3 million of revenue related to alumina sales to Glencore. Purchases from Glencore We purchase a portion of our alumina requirements from Glencore. Alumina purchases from Glencore during the three months ended March 31, 2020 were priced based on published alumina and aluminum indices, respectively. Financial contracts with Glencore We have certain financial contracts with Glencore. See Note 13. Derivatives regarding these forward financial sales contracts. Hawesville Term Loan On April 29, 2019, we entered into a loan agreement with Glencore Ltd. pursuant to which the Company borrowed $40.0 million (the "Hawesville Term Loan”). See Note 9. Debt for additional information. Borrowings under the Hawesville Term Loan were used to partially finance the second phase of the Hawesville restart project. Summary A summary of the aforementioned significant related party transactions is as follows: Three months ended March 31, 2020 2019 Net sales to Glencore $ 271.0 $ 311.3 Purchases from Glencore 40.2 90.7 Purchases from BHH (1) — 6.1 (1) We previously owned a 40% interest in Baise Haohai Carbon Co. Ltd. ("BHH") and purchased carbon anodes from them for use in our operations. Purchases represented herein were prior to the divestiture of our interest in BHH on May 22, 2019.

Revenue

Revenue	3 Months Ended
	Mar. 31, 2020
Revenue Recognition and Deferred Revenue [Abstract]
Revenue	Revenue We disaggregate our revenue by geographical region as follows: Net Sales Three months ended March 31, 2020 2019 United States $ 274.1 $ 325.2 Iceland 147.1 164.8 Total $ 421.2 $ 490.0 Trade accounts receivable - net as of March 31, 2020 decreased by $17.3 million from December 31, 2019 due to a decrease in sales resulting from lower realized LME prices and timing of receivable collections.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements We measure certain of our assets and liabilities at fair value. Fair value represents the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The fair value hierarchy provides transparency regarding the inputs we use to measure fair value. We categorize each fair value measurement in its entirety into the following three levels, based on the lowest level input that is significant to the entire measurement: • Level 1 Inputs - quoted prices (unadjusted) in active markets for identical assets or liabilities that the reporting entity can access at the measurement date. • Level 2 Inputs - inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. • Level 3 Inputs - significant unobservable inputs for the asset or liability. Recurring Fair Value Measurements As of March 31, 2020 Level 1 Level 2 Level 3 Total ASSETS: Cash equivalents $ 89.3 $ — $ — $ 89.3 Trust assets (1) 1.3 — — 1.3 Surety bonds (2) 1.9 — — 1.9 Derivative instruments — 50.5 7.8 58.3 TOTAL $ 92.5 $ 50.5 $ 7.8 $ 150.8 LIABILITIES: Contingent obligation – net $ — $ — $ — $ — Derivative instruments — 36.1 3.2 39.3 TOTAL $ — $ 36.1 $ 3.2 $ 39.3 Recurring Fair Value Measurements As of December 31, 2019 Level 1 Level 2 Level 3 Total ASSETS: Cash equivalents $ 23.3 $ — $ — $ 23.3 Trust assets (1) 0.2 — — 0.2 Surety bonds (2) 1.8 — — 1.8 Derivative instruments — 9.1 10.6 19.7 TOTAL $ 25.3 $ 9.1 $ 10.6 $ 45.0 LIABILITIES: Contingent obligation – net $ — $ — $ — $ — Derivative instruments — 1.3 2.9 4.2 TOTAL $ — $ 1.3 $ 2.9 $ 4.2 (1) Trust assets are currently invested in money market funds. These trust assets are held to fund the non-qualified supplemental executive pension benefit obligations for certain of our officers. (2) Surety bonds are currently invested in U.S. treasury bills and represent collateral against our workers' compensation insurance policy. We use the following valuation techniques and inputs for fair value measurements categorized within Level 2 of the fair value hierarchy: Level 2 Fair Value Measurements: Asset / Liability Level Valuation Techniques Inputs LME forward financial sales contracts 2 Discounted cash flows Quoted LME forward market MWP forward financial sales contracts 2 Discounted cash flows Quoted MWP forward market Fixed for floating swaps 2 Discounted cash flows Quoted LME forward market, quoted MWP forward market Nord Pool power price swaps 2 Discounted cash flows Quoted Nord Pool forward market NYMEX Henry Hub natural gas price swaps 2 Discounted cash flows Quoted Henry Hub forward market MISO Indiana Hub power price swaps 2 Discounted cash flows Quoted Indy Hub forward market FX swaps 2 Discounted cash flows Euro/USD forward exchange rate When valuing Level 3 assets and liabilities, we use certain significant unobservable inputs. Management incorporates various inputs and assumptions including forward commodity prices, commodity price volatility, and macroeconomic conditions, including interest rates and discount rates. Our estimates of significant unobservable inputs are ultimately based on our estimates of risks that market participants would consider when valuing our assets and liabilities. The following table presents the inputs for fair value measurements categorized within Level 3 of the fair value hierarchy, along with information regarding significant unobservable inputs used to value Level 3 assets and liabilities: Level 3 Fair Value Measurements: Asset / Liability Fair Value at 3/31/2020 Valuation Technique Observable Inputs Significant Unobservable Input Value/Range of Unobservable Input LME forward financial sales contracts $ 7.8 Discounted cash flows Quoted LME forward market prices Discount rate (1) 7.50% Contingent obligation $ — Discounted cash flows Quoted LME forward market prices Management's estimates of the LME forward market price beyond the quoted periods (2) $1,496/T-$2,122/T Hawesville L4 power price swaps $ 3.2 Discounted cash flows Quoted Indy Hub forward market prices Estimates of locational margin prices during contract term (3) $0.58/MwH (1) Represents risk adjusted discount rate. (2) Represents the range of estimated forward LME prices of primary aluminum through the term of the agreement in December 2028. (3) Represents historical average of locational margin prices in the past three years . The following table presents the fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis. Level 3 Assets Level 3 Liabilities For the three months ended March 31, 2020 LME forward financial sales contracts Hawesville L4 power price swaps Balance as of January 1, 2020 $ 10.6 $ (2.9 ) Total realized/unrealized gains (losses) Included in net income (loss) 6.7 (1.5 ) Purchases, sales, settlements Purchases — — Sales — — Settlements — 1.2 Transfers into Level 3 — — Transfers out of Level 3 (1) (9.5 ) — Balance as of March 31, 2020 $ 7.8 $ (3.2 ) Change in unrealized gains (losses) (2) $ 6.7 $ (0.3 ) (1) Transfer out of Level 3 due to period of time remaining in derivative contract (2) Gains and losses are presented in the Statement of Operations within the line item "Net gain (loss) on forward and derivative contracts" For the three months ended March 31, 2019 Level 3 Assets Level 3 Liabilities Nord Pool power price swaps US LME forward financial sales contracts Iceland LME forward financial sales contracts MWP forward financial sales contracts FX Swaps Balance as of January 1, 2019 $ 4.7 $ 0.3 $ (0.2 ) $ — $ (0.3 ) Total realized/unrealized gains (losses) Included in Net Income (2) (1.0 ) (1.9 ) (0.1 ) (1.7 ) (0.3 ) Purchases, sales, settlements Purchases — — — — — Sales — — — — — Settlements — — — 0.2 — Transfers into Level 3 (1) — (0.2 ) — 0.6 — Transfers out of Level 3 — — — — — Balance as of March 31, 2019 $ 3.7 $ (1.8 ) $ (0.3 ) $ (0.9 ) $ (0.6 ) Change in unrealized gains (losses) (2) $ (1.0 ) $ (2.1 ) $ (0.1 ) $ (0.9 ) $ (0.3 ) (1) Transfer into Level 3 resulting from long term derivative contracts entered into during the first quarter of 2019. (2) Gains and losses are presented in the Statement of Operations within the line item "Net gain (loss) on forward and derivative contracts"

Earnings (Loss) Per Share

Earnings (Loss) Per Share	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Earnings (Loss) Per Share	Earnings (Loss) Per Share Basic earnings (loss) per share ("EPS") amounts are calculated by dividing net income (loss) allocated to common stockholders by the weighted average number of common shares outstanding during the period. Diluted EPS amounts assume the issuance of common stock for all potentially dilutive securities. The following table shows the basic and diluted earnings (loss) per share: For the three months ended March 31, 2020 2019 Net Income (Loss) Shares (in millions) Per Share Net Income (Loss) Shares (in millions) Per Share Net income (loss) $ (2.7 ) $ (34.6 ) Amount allocated to common stockholders 100.0 % 100.0 % Basic and diluted EPS (1) $ (2.7 ) 89.3 $ (0.03 ) $ (34.6 ) 88.1 $ (0.39 ) Three months ended March 31, Securities excluded from the calculation of diluted EPS (in millions) (1) : 2020 2019 Share-based compensation 0.4 0.6 (1) In periods when we report a net loss, all share-based compensation awards are excluded from the calculation of diluted weighted average shares outstanding because of their anti-dilutive effect on earnings (loss) per share.

Shareholders_ Equity

Shareholders’ Equity	3 Months Ended
	Mar. 31, 2020
Stockholders' Equity Note [Abstract]
Shareholders’ Equity	Shareholders’ Equity Common Stock As of March 31, 2020 and December 31, 2019 , we had 195,000,000 shares of common stock, $0.01 par value per share, authorized under our Restated Certificate of Incorporation, of which 96,647,486 shares were issued and 89,460,965 shares were outstanding at March 31, 2020 ; 96,372,182 shares were issued and 89,185,661 shares were outstanding at December 31, 2019 . The rights, preferences and privileges of holders of our common stock are subject to, and may be adversely affected by, the rights of the holders of shares of any series of our preferred stock which are currently outstanding, including our Series A Convertible Preferred Stock, or which we may designate and issue in the future. Preferred Stock As of March 31, 2020 and December 31, 2019 , we had 5,000,000 shares of preferred stock, $0.01 par value per share, authorized under our Restated Certificate of Incorporation. In 2008, we issued 160,000 shares of our Series A Convertible Preferred Stock. Glencore holds all of the issued and outstanding Series A Convertible Preferred Stock. At March 31, 2020 and December 31, 2019 , there were 66,141 and 67,323 shares of Series A Convertible Preferred Stock outstanding, respectively. The issuance of common stock under our stock incentive programs, debt exchange transactions and any stock offering that excludes Glencore participation triggers anti-dilution provisions of the preferred stock agreement and results in the automatic conversion of Series A Convertible Preferred Stock shares into shares of common stock. The conversion ratio of preferred to common shares is 100 shares of common stock for each share of preferred stock. The Common and Preferred Stock table below contains additional information about preferred stock conversions during the three months ended March 31, 2020 and 2019 . Preferred stock Common stock Common and Preferred Stock Activity (in shares): Series A Convertible Treasury Outstanding Beginning balance as of December 31, 2019 67,323 7,186,521 89,185,661 Conversion of convertible preferred stock (1,182 ) — 118,146 Issuance for share-based compensation plans — — 157,158 Ending balance as of March 31, 2020 66,141 7,186,521 89,460,965 Beginning balance as of December 31, 2018 71,967 7,186,521 88,103,440 Conversion of convertible preferred stock (3,023 ) — 302,255 Issuance for share-based compensation plans — — 402,062 Ending balance as of March 31, 2019 68,944 7,186,521 88,807,757 Stock Repurchase Program In 2011, our Board of Directors authorized a $60.0 million common stock repurchase program and during the first quarter of 2015, our Board of Directors increased the size of the program by $70.0 million . Under the program, Century is authorized to repurchase up to $130.0 million of our outstanding shares of common stock, from time to time, on the open market at prevailing market prices, in block trades or otherwise. The timing and amount of any shares repurchased will be determined by our management based on its evaluation of market conditions, the trading price of our common stock and other factors. The stock repurchase program may be suspended or discontinued at any time. Shares of common stock repurchased are recorded at cost as treasury stock and result in a reduction of shareholders’ equity in the consolidated balance sheets. From time to time, treasury shares may be reissued as contributions to our employee benefit plans and for the conversion of convertible preferred stock. When shares are reissued, we use an average cost method for determining cost. The difference between the cost of the shares and the reissuance price is added to or deducted from additional paid-in capital. We have repurchased 7,186,521 shares of common stock under the program for an aggregate purchase price of $86.3 million . We have made no repurchases since April 2015 and we have $43.7 million remaining under the repurchase program authorization as of March 31, 2020

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes We recorded an income tax benefit of $ 2.8 million and $ 2.9 million for the three months ended March 31, 2020 and 2019, respectively, which primarily consisted of tax benefits on losses from foreign operations. Our income tax benefit or expense is based on an annual effective tax rate forecast, including estimates and assumptions that could change during the year. The application of the accounting requirements for income taxes in interim periods, after consideration of our valuation allowance, causes a significant variation in the typical relationship between income tax expense/benefit and pre-tax accounting income/loss. As of March 31, 2020 , all of Century's U.S. and certain foreign deferred tax assets, net of deferred tax liabilities, continue to be subject to a valuation allowance. On January 1, 2019, the Company adopted ASU 2018-02, "Income Statement-Reporting Comprehensive Income (Topic 220), Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income," which provides for the reclassification from accumulated other comprehensive income to retained earnings of stranded tax effects resulting from the Tax Cuts and Jobs Act ("the Act"). In accordance with the provisions of ASU 2018-02, $1.3 million of stranded tax effects related to the Act were reclassified from accumulated other comprehensive loss to retained earnings in the first quarter of 2019. This reclassification included the impact of the change in the federal corporate income tax rate and the related federal benefit of state taxes. The Company’s accounting policy with respect to releasing income tax effects from accumulated other comprehensive income is to apply a security by security approach whereby the tax effects are measured based on the change in the unrealized gains or losses reflected in other comprehensive loss.

Inventories

Inventories	3 Months Ended
	Mar. 31, 2020
Inventory, Net [Abstract]
Inventories	Inventories Inventories consist of the following: March 31, 2020 December 31, 2019 Raw materials $ 94.8 $ 101.3 Work-in-process 46.8 44.1 Finished goods 38.1 34.3 Operating and other supplies 137.9 140.9 Total inventories $ 317.6 $ 320.6 Inventories are stated at the lower of cost or Net Realizable Value ("NRV") using the first-in, first-out ("FIFO") or the weighted average cost method.

Debt

Debt	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Debt	Debt March 31, 2020 December 31, 2019 Debt classified as current liabilities: Hawesville Term Loan - current portion (1) $ 20.0 $ 20.0 Hancock County industrial revenue bonds ("IRBs") due April 1, 2028, interest payable quarterly (variable interest rates (not to exceed 12%)) (2) 7.8 7.8 U.S. Revolving Credit Facility (3) 45.0 4.0 Debt classified as non-current liabilities: Iceland Revolving Credit Facility (4) 45.0 — 7.5% senior secured notes due June 2021, net of debt discount of $0.7 million and $0.8 million, respectively, interest payable semiannually 249.3 249.2 Hawesville Term Loan - less current portion (1) , principal and interest payable monthly 15.0 20.0 Total $ 382.1 $ 301.0 (1) See "Hawesville Term Loan" below. At March 31, 2020 , the applicable interest rate was LIBOR of 1.68% plus margin of 5.375% and there is no interest payable outstanding. As of March 31, 2020, we have made $5.0 million of principal payments and $0.7 million of interest payments. (2) The IRBs are classified as current liabilities because they are remarketed weekly and could be required to be repaid upon demand if there is a failed remarketing. The IRB interest rate at March 31, 2020 was 5.63% . (3) For borrowings that we expect to repay within a month, we generally elect to incur interest at a base rate plus applicable margin as defined within the agreement. The interest rates at March 31, 2020 was 3.5% . (4) We have elected to incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at March 31, 2020 was 3.8% . 7.5% Notes due 2021 General. In June 2013, we issued $250.0 million of our 7.5% Notes due June 2021 (the "2021 Notes") in a private offering exempt from the registration requirements of the Securities Act of 1933, as amended. The 2021 Notes were issued at a discount and we received proceeds of $246.3 million , prior to payment of financing fees and related expenses. The 2021 Notes bear interest at a rate of 7.5% per annum on the principal amount, payable semi-annually in arrears in cash on June 1st and December 1st of each year. The Notes are senior secured obligations of Century, ranking equally in right of payment with all existing and future senior indebtedness of Century, but effectively senior to unsecured debt to the extent of the value of the collateral. The maturity date for the payment of principal is June 2021. Fair Value. Fair value for our 2021 Notes, based on the latest trading data available, was $228.5 million and $244.2 million , as of March 31, 2020 and December 31, 2019 , respectively. Although we use quoted market prices for identical debt instruments, the markets on which they trade are not considered to be active and are therefore considered Level 2 fair value measurements. Hawesville Term Loan On April 29, 2019, we entered into a loan agreement with Glencore Ltd. pursuant to which the Company borrowed $40.0 million . Borrowings under the Hawesville Term Loan were used to partially finance the second phase of the Hawesville restart project. The Hawesville Term Loan matures on December 31, 2021 and is to be repaid in twenty-four ( 24 ) equal monthly installments of principal, beginning on January 31, 2020. The Hawesville Term Loan bears interest, due monthly, at a floating rate equal to LIBOR plus 5.375% per annum. The Hawesville Term Loan is not secured by any collateral. U.S. Revolving Credit Facility We and certain of our direct and indirect domestic subsidiaries ("the Borrowers") have a senior secured revolving credit facility with a syndicate of lenders (the "U.S. revolving credit facility"). The U.S. revolving credit facility provides for borrowings of up to $175.0 million in the aggregate, including up to $110.0 million under a letter of credit sub-facility, and also includes an uncommitted accordion feature whereby borrowers may increase the capacity of the U.S. revolving credit facility by up to $50.0 million , subject to agreement with the lenders. The U.S. revolving credit facility matures on the earlier of May 2023 or six months before the stated maturity of our outstanding senior secured notes. Based on the current maturity date for our outstanding secured notes of June 1, 2021, the maturity date for the U.S. revolving credit facility would be December 1, 2020. Upon a refinancing of our secured notes, the maturity date of our U.S. revolving credit facility will extend to May 2023. Any letters of credit issued and outstanding under the U.S. revolving credit facility reduce our borrowing availability on a dollar-for-dollar basis. At March 31, 2020 , there were $45.0 million in outstanding borrowings under our U.S. revolving credit facility. Principal payments, if any, are due upon maturity of the U.S. revolving credit facility and may be prepaid without penalty. The U.S revolving credit facility contains a springing financial covenant that requires us to maintain a fixed charge coverage ratio of at least 1.0 to 1.0 any time availability under the U.S revolving credit facility is less than or equal to the lower of $17.5 million or 10% of the borrowing base but not less than $12.5 million . Status of our U.S. revolving credit facility: March 31, 2020 Credit facility maximum amount $ 175.0 Borrowing availability 133.8 Outstanding letters of credit issued 38.3 Outstanding borrowings 45.0 Borrowing availability, net of outstanding letters of credit and borrowings 50.5 Iceland Revolving Credit Facility Our wholly-owned subsidiary, Nordural Grundartangi ehf ("Grundartangi"), has entered into a $50.0 million revolving credit facility agreement with Landsbankinn hf., dated November 2013, as amended (the "Iceland revolving credit facility"). Under the terms of the Iceland revolving credit facility, when Grundartangi borrows funds it will designate a repayment date, which may be any date prior to the maturity of the Iceland revolving credit facility. At March 31, 2020 , there were $ 45.0 million in outstanding borrowings under our Iceland revolving credit facility. The Iceland revolving credit facility has a term through November 2022. Principal payments, if any, are due upon maturity of the Iceland revolving credit facility and may be prepaid without penalty. Status of our Iceland revolving credit facility: March 31, 2020 Credit facility maximum amount $ 50.0 Borrowing availability 50.0 Outstanding letters of credit issued — Outstanding borrowings 45.0 Borrowing availability, net of borrowings 5.0

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and contingencies	Commitments and Contingencies We have pending against us or may be subject to various lawsuits, claims and proceedings related primarily to employment, commercial, stockholder, environmental, safety and health matters and are involved in other matters that may give rise to contingent liabilities. While the results of such matters and claims cannot be predicted with certainty, we believe that the ultimate outcome of any such matters and claims will not have a material adverse impact on our financial condition, results of operations or liquidity. However, because of the nature and inherent uncertainties of litigation and estimating liabilities, should the resolution or outcome of these actions be unfavorable, our business, financial condition, results of operations and liquidity could be materially and adversely affected. In evaluating whether to accrue for losses associated with legal or environmental contingencies, it is our policy to take into consideration factors such as the facts and circumstances asserted, our historical experience with contingencies of a similar nature, the likelihood of our prevailing and the severity of any potential loss. For some matters, no accrual is established because we have assessed our risk of loss to be remote. Where the risk of loss is probable and the amount of the loss can be reasonably estimated, we record an accrual, either on an individual basis or with respect to a group of matters involving similar claims, based on the factors set forth above. While we regularly review the status of, and our estimates of potential liability associated with, contingencies to determine the adequacy of any associated accruals and related disclosures, the ultimate amount of loss may differ from our estimates. Legal Contingencies Vernon In July 2006, we were named as a defendant, together with certain affiliates of Alcan Inc., in a lawsuit brought by Alcoa Inc. seeking to determine responsibility for certain environmental indemnity obligations related to the sale of a cast aluminum plate manufacturing facility located in Vernon, California, which we purchased from Alcoa Inc. in December 1998, and sold to Alcan Rolled Products-Ravenswood LLC in July 1999. The complaint also seeks costs and attorney fees. The matter was stayed by the court in 2008 to allow for the remediation of environmental areas at the site. On June 30, 2016, the U.S. District Court for the District of Delaware ordered the stay lifted and reopened the case. Discovery was completed in the third quarter of 2019. Trial was bifurcated and moved from March 2020 to November 2020 for Comprehensive Environmental Response, Compensation, and Liability Act ("CERCLA") issues and to February 2021 for questions of fact. At this stage, we cannot predict the ultimate outcome of this action or estimate a range of reasonably possible losses related to this matter. Ravenswood Retiree Medical Benefits In November 2009, Century Aluminum of West Virginia ("CAWV") filed a class action complaint for declaratory judgment against the United Steel, Paper and Forestry, Rubber, Manufacturing, Energy, Allied Industrial and Service Workers International Union ("USW"), the USW’s local and certain CAWV retirees, individually and as class representatives ("CAWV Retirees"), seeking a declaration of CAWV’s rights to modify/terminate retiree medical benefits. Later in November 2009, the USW and representatives of a retiree class filed a separate suit against CAWV, Century Aluminum Company, Century Aluminum Master Welfare Benefit Plan, and various John Does with respect to the foregoing. On August 18, 2017, the District Court for the Southern District of West Virginia approved a settlement agreement in respect of these actions. Under the terms of the settlement agreement, CAWV agreed to make payments into a trust for the benefit of the CAWV Retirees in the aggregate amount of $23.0 million over the course of 10 years. Upon approval of the settlement, we paid $5.0 million to the aforementioned trust in September 2017 and recognized a gain of $5.5 million to arrive at the-then net present value of $12.5 million . CAWV has agreed to pay the remaining amounts under the settlement agreement in annual increments of $2.0 million for nine years. As of March 31, 2020 , $2.0 million was recorded in other current liabilities and $8.9 million was recorded in other liabilities. PBGC Settlement In 2013, we entered into a settlement agreement with the Pension Benefit Guarantee Corporation ("PBGC") regarding an alleged "cessation of operations" at our Ravenswood facility. Pursuant to the terms of the agreement, we agreed to make additional contributions (above any minimum required contributions) to our defined benefit pension plans totaling approximately $17.4 million . Under certain circumstances, in periods of lower primary aluminum prices relative to our cost of operations, we are able to defer one or more of these payments, provided that we provide the PBGC with acceptable security for such deferred payments. We did not make any contributions for the three month periods ended March 31, 2020 and 2019 . We have elected to defer certain payments under the PBGC agreement and have provided the PBGC with the appropriate security. The remaining contributions under this agreement are approximately $9.6 million . Environmental Contingencies Matters relating to the St. Croix Alumina Refining Facility We are a party to a United States Environmental Protection Agency Administrative Order on Consent (the "Order") pursuant to which certain past and present owners of an alumina refining facility at St. Croix, Virgin Islands (the "St. Croix Alumina Refinery") have agreed to carry out a Hydrocarbon Recovery Plan to remove and manage hydrocarbons floating on groundwater underlying the facility. Pursuant to the Hydrocarbon Recovery Plan, recovered hydrocarbons and groundwater are delivered to the adjacent petroleum refinery where they are received and managed. At this time, we are not able to estimate the amount of any future potential payments under this indemnification to comply with the Order, but we do not anticipate that any such amounts will have a material adverse effect on our financial condition, results of operations or liquidity, regardless of the final outcome. In December 2010, Century was among several defendants named in a lawsuit filed by plaintiffs who either worked, resided or owned property in the area downwind from the St. Croix Alumina Refinery. In March 2011, Century was also named a defendant in a nearly identical suit brought by certain additional plaintiffs. The plaintiffs in both suits allege damages caused by the presence of red mud and other particulates coming from the alumina facility and are seeking unspecified monetary damages, costs and attorney fees as well as certain injunctive relief. We tendered indemnity and defense to St. Croix Alumina LLC and Alcoa Alumina & Chemical LLC under the terms of an acquisition agreement relating to the facility and have filed motions to dismiss plaintiffs’ claims. In August 2015, the Superior Court of the Virgin Islands, Division of St. Croix denied the motions to dismiss but ordered all plaintiffs to refile individual complaints. On February 28, 2018, plaintiffs in both cases filed a Motion for Voluntary Dismissal of Century without prejudice to refiling. At this time, it is not possible to predict the ultimate outcome of or to estimate a range of reasonably possible losses for any of the foregoing actions relating to the St. Croix Alumina Refinery. Power Commitments and Contingencies Hawesville Hawesville has a power supply arrangement with Kenergy and EDF Trading North America, LLC (“EDF") which provides market-based power to the Hawesville smelter. Under this arrangement, the power companies purchase power on the open market and pass it through to Hawesville at Midcontinent Independent System Operator ("MISO") pricing plus transmission and other costs. The power supply arrangement with Kenergy has an effective term through December 2023. The arrangement with EDF to act as our market participant with MISO has an effective term through May 2021. Each of these agreements provide for automatic extension on a year-to-year basis unless a one year notice is given. Sebree Sebree has a power supply arrangement with Kenergy and EDF which provides market-based power to the Sebree smelter. Similar to the arrangement at Hawesville, the power companies purchase power on the open market and pass it through to Sebree at MISO pricing plus transmission and other costs. The power supply arrangement with Kenergy has an effective term through December 2023. The arrangement with EDF to act as our market participant with MISO has an effective term through May 2021. Each of these agreements provides for automatic extension on a year-to-year basis unless a one year notice is given. Mt. Holly Mt. Holly has a power supply arrangement pursuant to which 25% of the Mt. Holly load is served from the South Carolina Public Service Authority’s ("Santee Cooper") generation at a cost-based industrial rate and 75% of the Mt. Holly load is sourced from a supplier that is outside Santee Cooper’s service territory at market prices that are tied to natural gas prices. The agreement with Santee Cooper has a term through December 31, 2020 and can be terminated by Mt. Holly on 120 days' notice. The agreement with the other power supplier has a term through December 31, 2020 and may be terminated by Mt. Holly on 60 days’ notice. Grundartangi Grundartangi has power purchase agreements for approximately 525 MW with HS Orka hf ("HS"), Landsvirkjun and Orkuveita Reykjavikur ("OR") to provide power to its Grundartangi smelter. These power purchase agreements expire on various dates from 2023 through 2036 (subject to extension). The power purchase agreements with HS and OR both provide power at LME-based variable rates for the duration of these agreements. The power purchase agreement with Landsvirkjun for 161 MW provides power at rates linked to the Nord Pool power market. Helguvik Nordural Helguvik ehf ("Helguvik") has a power purchase agreement with OR to provide a portion of the power requirements to the Helguvik project. The agreement would provide power at LME-based variable rates and contain take-or-pay obligations with respect to a significant percentage of the total committed and available power under such agreement. The first phase of power under the OR purchase agreement (approximately 47.5 MW) became available in the fourth quarter of 2011 and is currently being utilized at Grundartangi. The agreement contains certain conditions to OR’s obligations with respect to the remaining phases and OR has alleged that certain of these conditions have not been satisfied. Other Commitments and Contingencies Labor Commitments The bargaining unit employees at our Grundartangi, Vlissingen, Hawesville and Sebree facilities are represented by labor unions, representing approximately 65% of our total workforce. Approximately 86% of Grundartangi’s work force is represented by five labor unions, governed by a labor agreement that establishes wages and work rules for covered employees. This agreement expired on December 31, 2019. Since such time we have been operating under the terms of the expired agreement while we engage in negotiations with the unions regarding the terms of a new agreement. 100% of Vlissingen's work force is represented by the Federation for the Metal and Electrical Industry ("FME") by a labor agreement that is effective through December 1, 2020. Approximately 57% of our U.S. based work force is represented by USW. The labor agreement for Hawesville employees is effective through April 1, 2021. Century Sebree's labor agreement with the USW for its employees is effective through October 28, 2023. Mt. Holly employees are not represented by a labor union.

Components of Accumulated Other

Components of Accumulated Other Comprehensive Loss	3 Months Ended
	Mar. 31, 2020
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Components of Accumulated Other Comprehensive Loss	Components of Accumulated Other Comprehensive Loss Components of AOCL: March 31, 2020 December 31, 2019 Defined benefit plan liabilities $ (114.2 ) $ (115.9 ) Unrealized gain (loss) on financial instruments 2.3 2.3 Other comprehensive loss before income tax effect (111.9 ) (113.6 ) Income tax effect (1) 3.5 3.8 Accumulated other comprehensive loss $ (108.4 ) $ (109.8 ) (1) The allocation of the income tax effect to the components of other comprehensive loss is as follows: March 31, 2020 December 31, 2019 Defined benefit plan liabilities $ 4.0 $ 4.3 Unrealized loss on financial instruments (0.5 ) (0.4 ) The following table summarizes the changes in the accumulated balances for each component of AOCL: Defined benefit plan and other postretirement liabilities Unrealized gain (loss) on financial instruments Total, net of tax Balance, January 1, 2020 $ (111.7 ) $ 1.9 $ (109.8 ) Net amount reclassified to net income (loss) 1.4 0.0 1.4 Balance, March 31, 2020 $ (110.3 ) $ 1.9 $ (108.4 ) Balance, January 1, 2019 $ (100.7 ) $ 2.0 $ (98.7 ) Impact of ASU 2018-02 (2) (1.3 ) — (1.3 ) Net amount reclassified to net income (loss) 0.3 0.0 0.3 Balance, March 31, 2019 $ (101.7 ) $ 2.0 $ (99.7 ) (2) ASU 2018-02. See Note 7. Income Taxes for further information regarding our adoption of ASU 2018-02. Reclassifications out of AOCL were included in the consolidated statements of operations as follows: Three months ended March 31, AOCL Components Location 2020 2019 Defined benefit plan and other postretirement liabilities Cost of goods sold $ 1.1 $ 0.6 Selling, general and administrative expenses 0.2 (0.4 ) Other operating expense, net 0.4 0.4 Income tax effect (0.3 ) (0.3 ) Net of tax $ 1.4 $ 0.3 Unrealized loss on financial instruments Cost of goods sold $ 0.0 $ 0.0 Income tax effect 0.0 0.0 Net of tax $ 0.0 $ 0.0

Components of Net Periodic Bene

Components of Net Periodic Benefit Cost	3 Months Ended
	Mar. 31, 2020
Components of net periodic benefit cost [Abstract]
Components of Net Periodic Benefit Cost	Components of Net Periodic Benefit Cost Pension Benefits Three months ended March 31, 2020 2019 Service cost $ 1.3 $ 1.1 Interest cost 2.8 3.3 Expected return on plan assets (5.1 ) (4.9 ) Amortization of prior service costs 0.0 0.0 Amortization of net loss 1.5 1.1 Net periodic benefit cost $ 0.5 $ 0.6 Other Postretirement Benefits ("OPEB") Three months ended March 31, 2020 2019 Service cost $ 0.1 $ 0.0 Interest cost 0.8 1.0 Amortization of prior service cost (0.8 ) (1.3 ) Amortization of net loss 1.0 0.8 Net periodic benefit cost $ 1.1 $ 0.5

Derivatives

Derivatives	3 Months Ended
	Mar. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives	Derivatives As of March 31, 2020 , we had an open position of 145,402 tonnes related to LME forward financial sales contracts to fix the forward LME price. These contracts are expected to settle monthly through December 2024. We also had an open position of 117,000 tonnes related to Midwest Premium ("MWP") forward financial sales contracts to fix the forward MWP price. These contracts are expected to settle through December 2021. We have entered into financial contracts to fix the forward price for power related to the expected production of Line 4 at Hawesville for the period of January 2020 through December 2020 ("Hawesville L4 power price swaps"). As of March 31, 2020 , we had an open position of 592,920 MWh. The Hawesville L4 power price swaps are expected to settle monthly over the term of the contracts. We have entered into financial contracts to hedge approximately 50% of our exposure at our U.S operations to the MISO Indiana Hub (“MISO Indiana Hub power price swaps”) and the NYMEX Henry Hub (“NYMEX Henry Hub natural gas price swaps”) for the period of April 2020 through September 2020. The natural gas volume is measured per million British Thermal Units ("mmBTU"). As of March 31, 2020 , we had an open position of 2,340,000 mmBTU related to the NYMEX Henry Hub natural gas price swaps and an open position of 1,471,320 MWh related to the MISO Indiana Hub power price swaps. Both the NYMEX Henry Hub natural gas price swaps and MISO Indiana power price swaps are expected to settle monthly over the term of the contracts. We have financial contracts with various counterparties to offset fixed price sales arrangements with certain of our customers (“fixed for floating swaps”) to remain exposed to the LME and MWP prices. As of March 31, 2020 , we had an open position related to such arrangements of 15,271 tonnes that will settle at various dates through June 2021. We have entered into financial contracts to hedge approximately all of Grundartangi's exposure to the Nord Pool power market through December 2020 and 50% of Grundartangi's exposure to the Nord Pool power market through December 2021 (“Nord Pool power price swaps”), respectively. As of March 31, 2020 , we had an open position of 1,693,958 MWh related to the Nord Pool power price swaps. Because the Nord Pool power price swaps are settled in euros, we have entered into financial contracts to hedge the risk of fluctuations associated with the euro ("FX swaps"). As of March 31, 2020 , we had an open position related to the FX swaps of €44.6 million that will settle monthly through December 2021. The following table sets forth the Company's derivative assets and liabilities that were accounted for at fair value and not designated as cashflow hedges as of March 31, 2020 and December 31, 2019, respectively: Asset Fair Value March 31, 2020 December 31, 2019 Commodity contracts (1) $ 58.3 $ 19.7 Foreign exchange contracts (2) — — Total $ 58.3 $ 19.7 Liability Fair Value March 31, 2020 December 31, 2019 Commodity contracts (1) $ 37.7 $ 3.6 Foreign exchange contracts (2) 1.6 0.6 Total $ 39.3 $ 4.2 (1) Commodity contracts reflect our outstanding LME forward financial sales contracts, MWP forward financial sales contracts, Hawesville L4 power price swaps, fixed for floating swaps, NYMEX Henry Hub natural gas price swaps, MISO Indiana Hub power price swaps, and Nord Pool power price swaps. At March 31, 2020 and December 31, 2019, $ 8.1 million and $ 0.2 million of Due from affiliates and $ 5.1 million and $ 0.5 million of Due from affiliates - less current portion, respectively, is related to commodity contract assets with Glencore. (2) Foreign exchange contracts reflect our outstanding FX swaps. The following table summarizes the net (loss) gain on forward and derivative contracts: Three months ended March 31, 2020 2019 Commodity contracts (3) $ 9.0 $ (5.5 ) Foreign exchange contracts (5.2 ) (0.2 ) Total $ 3.8 $ (5.7 ) (3) For the three months ended March 31, 2020 and 2019, $ 12.6 million and $ (1.0) million

Condensed Consolidating Financi

Condensed Consolidating Financial Information	3 Months Ended
	Mar. 31, 2020
Condensed Financial Information Disclosure [Abstract]
Condensed Consolidating Financial Information	Condensed Consolidating Financial Information The Company has filed a Registration Statement on Form S-3 (the "Universal Shelf Registration Statement") with the Securities and Exchange Commission pursuant to which the Company may, from time to time, offer an indeterminate amount of securities, which may include securities that are guaranteed by certain of the Company's subsidiaries. The condensed consolidated financial information below is presented herein pursuant to the Universal Shelf Registration Statement. We have not issued any debt securities pursuant to the Universal Shelf Registration Statement. "Guarantor Subsidiaries" refers to all of our material domestic subsidiaries except for Nordural US LLC, Century Aluminum Development LLC and Century Aluminum of West Virginia, Inc. The Guarantor Subsidiaries are 100% owned by Century. All guarantees will be full and unconditional; all guarantees will be joint and several. Our foreign subsidiaries, together with Nordural US LLC, Century Aluminum Development LLC and Century Aluminum of West Virginia, Inc., are collectively referred to as the “Non-Guarantor Subsidiaries”. We allocate corporate expenses or income to our subsidiaries and charge interest on certain intercompany balances. The following summarized condensed consolidating statements of comprehensive income (loss) for the three months ended March 31, 2020 and 2019 , condensed consolidating balance sheets as of March 31, 2020 and December 31, 2019 and the condensed consolidating statements of cash flows for the three months ended March 31, 2020 and 2019 present separate results for Century, the Guarantor Subsidiaries, the Non-Guarantor Subsidiaries, consolidating adjustments and total consolidated amounts. Condensed Consolidating Statements of Comprehensive Income (Loss) For the three months ended March 31, 2020 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated NET SALES: Related parties $ — $ 147.9 $ 123.1 $ — $ 271.0 Other customers — 126.3 23.9 — 150.2 Total net sales — 274.2 147.0 — 421.2 Cost of goods sold — 281.0 135.4 — 416.4 Gross profit (loss) — (6.8 ) 11.6 — 4.8 Selling, general and administrative expenses 8.4 — 0.5 — 8.9 Other operating (income) expense - net — — 0.3 — 0.3 Operating income (loss) (8.4 ) (6.8 ) 10.8 — (4.4 ) Interest expense - term loan (0.7 ) — — — (0.7 ) Interest expense (5.1 ) (0.4 ) (0.5 ) — (6.0 ) Intercompany interest 8.4 2.7 (11.1 ) — — Interest income — — 0.1 — 0.1 Net gain (loss) on forward and derivative contracts 32.6 0.4 (29.2 ) — 3.8 Other income (expense) - net 0.3 (0.1 ) 1.5 — 1.7 Income (loss) before income taxes and equity in earnings of joint ventures 27.1 (4.2 ) (28.4 ) — (5.5 ) Income tax benefit (expense) 0.5 — 2.3 — 2.8 Income (loss) before equity in earnings of joint ventures 27.6 (4.2 ) (26.1 ) — (2.7 ) Equity in earnings (loss) of joint ventures (30.4 ) 0.5 — 29.9 — Net income (loss) (2.8 ) (3.7 ) (26.1 ) 29.9 (2.7 ) Other comprehensive income before income tax effect 1.7 1.1 0.4 (1.5 ) 1.7 Income tax effect (0.3 ) — — — (0.3 ) Other comprehensive income 1.4 1.1 0.4 (1.5 ) 1.4 Total comprehensive income (loss) $ (1.4 ) $ (2.6 ) $ (25.7 ) $ 28.4 $ (1.3 ) Condensed Consolidating Statements of Comprehensive Income (Loss) For the three months ended March 31, 2019 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated NET SALES: Related parties $ — $ 152.5 $ 158.8 $ — $ 311.3 Other customers — 172.7 6.0 — 178.7 Total net sales — 325.2 164.8 — 490.0 Cost of goods sold — 327.2 175.6 — 502.8 Gross profit (loss) — (2.0 ) (10.8 ) — (12.8 ) Selling, general and administrative expenses 14.1 — 0.6 — 14.7 Other operating (income) expense - net — — 0.3 — 0.3 Operating income (loss) (14.1 ) (2.0 ) (11.7 ) — (27.8 ) Interest expense (5.4 ) (0.4 ) — — (5.8 ) Intercompany interest 8.7 2.5 (11.2 ) — — Interest income — — 0.2 — 0.2 Net gain (loss) on forward and derivative contracts (4.7 ) 0.4 (1.4 ) — (5.7 ) Other income (expense) - net 0.8 (0.5 ) 0.8 — 1.1 Income (loss) before income taxes and equity in earnings of joint ventures (14.7 ) — (23.3 ) — (38.0 ) Income tax (expense) benefit 1.0 — 1.9 — 2.9 Income (loss) before equity in earnings of joint ventures (13.7 ) — (21.4 ) — (35.1 ) Equity in earnings (loss) of joint ventures (20.9 ) 0.3 0.5 20.6 0.5 Net income (loss) (34.6 ) 0.3 (20.9 ) 20.6 (34.6 ) Other comprehensive income (loss) before income tax effect 0.6 0.6 0.3 (0.9 ) 0.6 Income tax effect (0.3 ) — — — (0.3 ) Other comprehensive income 0.3 0.6 0.3 (0.9 ) 0.3 Total comprehensive income (loss) $ (34.3 ) $ 0.9 $ (20.6 ) $ 19.7 $ (34.3 ) Condensed Consolidating Balance Sheet As of March 31, 2020 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated Cash & cash equivalents $ 82.5 $ 0.2 $ 64.9 $ — $ 147.6 Restricted cash — 1.8 — — 1.8 Accounts receivable - net 2.2 49.6 1.1 — 52.9 Due from affiliates 7.5 9.6 0.7 — 17.8 Inventories — 187.9 129.7 — 317.6 Derivative Assets 32.7 — — — 32.7 Prepaid and other current assets 4.9 0.5 8.0 — 13.4 Total current assets 129.8 249.6 204.4 — 583.8 Property, plant and equipment - net 16.5 332.8 586.1 — 935.4 Investment in subsidiaries 583.4 63.3 — (646.7 ) — Due from affiliates - long term 734.3 570.0 5.1 (1,304.3 ) 5.1 Other assets 44.7 3.9 18.2 — 66.8 TOTAL $ 1,508.7 $ 1,219.6 $ 813.8 $ (1,951.0 ) $ 1,591.1 Accounts payable, trade $ 3.8 $ 58.1 $ 25.2 $ — $ 87.1 Due to affiliates — 11.1 18.4 — 29.5 Accrued and other current liabilities 17.1 18.4 15.1 — 50.6 Derivative Liabilities 15.5 — 19.0 — 34.5 Accrued employee benefits costs 1.9 7.7 0.8 — 10.4 Term loan - current 20.0 — — — 20.0 U.S. Revolving credit facility 45.0 — — — 45.0 Industrial revenue bonds — 7.8 — — 7.8 Total current liabilities 103.3 103.1 78.5 — 284.9 Senior notes payable 249.3 — — — 249.3 Term loan - less current portion 15.0 — — — 15.0 Iceland Revolving credit facility — — 45.0 — 45.0 Accrued pension benefits costs - less current portion 24.8 26.8 7.7 — 59.3 Accrued postretirement benefits costs - less current portion 1.0 97.3 1.8 — 100.1 Due to affiliates - long term 432.2 320.2 551.9 (1,304.3 ) — Other liabilities 3.9 21.4 21.8 — 47.1 Leases - right of use liabilities 5.4 0.1 16.4 — 21.9 Deferred taxes — 0.4 94.3 — 94.7 Total noncurrent liabilities 731.6 466.2 738.9 (1,304.3 ) 632.4 Preferred stock 0.0 — — — 0.0 Common stock 1.0 — 0.1 (0.1 ) 1.0 Other shareholders' equity 672.8 650.3 (3.7 ) (646.6 ) 672.8 Total shareholders' equity 673.8 650.3 (3.6 ) (646.7 ) 673.8 TOTAL $ 1,508.7 $ 1,219.6 $ 813.8 $ (1,951.0 ) $ 1,591.1 Condensed Consolidating Balance Sheet As of December 31, 2019 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated Cash & cash equivalents $ 0.3 $ 0.1 $ 38.5 $ — $ 38.9 Restricted cash — 0.8 — — 0.8 Accounts receivable - net 0.7 64.1 5.3 — 70.1 Due from affiliates — 10.9 19.2 — 30.1 Inventories — 205.5 115.1 — 320.6 Derivative Assets 12.2 — 2.4 — 14.6 Prepaid and other current assets 3.0 2.8 6.4 — 12.2 Total current assets 16.2 284.2 186.9 — 487.3 Property, plant and equipment - net 17.2 334.8 597.2 — 949.2 Investment in subsidiaries 609.5 62.7 — (672.2 ) — Due from affiliates - long term 749.5 537.9 5.1 (1,292.0 ) 0.5 Other assets 38.1 5.7 18.9 — 62.7 TOTAL $ 1,430.5 $ 1,225.3 $ 808.1 $ (1,964.2 ) $ 1,499.7 Accounts payable, trade $ 2.3 $ 66.2 $ 28.6 $ — $ 97.1 Due to affiliates — 2.2 30.7 — 32.9 Accrued and other current liabilities 23.5 27.3 14.7 — 65.5 Accrued employee benefits costs 1.9 7.7 0.8 — 10.4 Hawesville term loan 20.0 — — — 20.0 Industrial revenue bonds — 7.8 — — 7.8 Total current liabilities 47.7 111.2 74.8 — 233.7 Senior notes payable 249.2 — — — 249.2 Hawesville term loan - less current portion 20.0 — — — 20.0 Accrued pension benefits costs - less current portion 25.1 27.3 8.4 — 60.8 Accrued postretirement benefits costs - less current portion 1.1 97.8 1.8 — 100.7 Leases - right of use liabilities 5.5 0.4 16.9 — 22.8 Other liabilities 3.5 22.2 16.7 — 42.4 Due to affiliates - long term 403.4 315.9 572.7 (1,292.0 ) — Deferred taxes — 0.4 94.7 — 95.1 Total noncurrent liabilities 707.8 464.0 711.2 (1,292.0 ) 591.0 Preferred stock 0.0 — — — 0.0 Common stock 1.0 0.0 0.1 (0.1 ) 1.0 Other shareholders' equity 674.0 650.1 22.0 (672.1 ) 674.0 Total shareholders' equity 675.0 650.1 22.1 (672.2 ) 675.0 TOTAL $ 1,430.5 $ 1,225.3 $ 808.1 $ (1,964.2 ) $ 1,499.7 Condensed Consolidating Statement of Cash Flows For the three months ended March 31, 2020 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated Net cash provided by (used in) operating activities $ (13.0 ) $ 34.1 $ 13.5 $ — $ 34.6 Purchase of property, plant and equipment (0.1 ) (5.6 ) (0.3 ) — (6.0 ) Proceeds from sale of property, plant, and equipment — — 0.1 — 0.1 Intercompany transactions 30.5 (29.4 ) (0.1 ) (1.0 ) — Net cash provided by (used in) investing activities 30.4 (35.0 ) (0.3 ) (1.0 ) (5.9 ) Repayments on term loan (5.0 ) — — — (5.0 ) Borrowings under revolving credit facilities 76.8 — 45.0 — 121.8 Repayments under revolving credit facilities (35.8 ) — — — (35.8 ) Intercompany transactions 28.9 1.9 (31.8 ) 1.0 — Net cash provided by (used in) financing activities 64.9 1.9 13.2 1.0 81.0 CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH 82.3 1.0 26.4 — 109.7 Cash, cash equivalents and restricted cash, beginning of period 0.2 1.0 38.5 — 39.7 Cash, cash equivalents and restricted cash, end of period $ 82.5 $ 2.0 $ 64.9 $ — $ 149.4 Condensed Consolidating Statement of Cash Flows For the three months ended March 31, 2019 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated Net cash provided by (used in) operating activities $ (17.6 ) $ (5.3 ) $ 1.4 $ — $ (21.5 ) Purchase of property, plant and equipment (0.6 ) (6.8 ) (3.2 ) — (10.6 ) Intercompany transactions (15.2 ) (17.7 ) 0.1 32.8 — Net cash provided by (used in) investing activities (15.8 ) (24.5 ) (3.1 ) 32.8 (10.6 ) Borrowings under revolving credit facilities 169.6 — — — 169.6 Repayments under revolving credit facilities (157.6 ) — — — (157.6 ) Debt issuance costs 3.4 — — — 3.4 Intercompany transactions 17.8 29.9 (14.9 ) (32.8 ) — Net cash provided by (used in) financing activities 33.2 29.9 (14.9 ) (32.8 ) 15.4 CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH (0.2 ) 0.1 (16.6 ) — (16.7 ) Cash, cash equivalents and restricted cash, beginning of period 0.1 0.8 38.8 — 39.7 Cash, cash equivalents and restricted cash, end of period $ (0.1 ) $ 0.9 $ 22.2 $ — $ 23.0

General (Policies)

General (Policies)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Recently Adopted Accounting Standards and Recently Issued Accounting Standards	Recently Adopted Accounting Standards On January 1, 2020, we adopted Financial Accounting Standards Board (“FASB”) Accounting Standards Update (“ASU”) 2016-13, “Measurement of Credit Losses on Financial Instruments.” The ASU added an impairment model known as the current expected credit loss ("CECL") model, which is based on expected losses rather than incurred losses. The CECL model is applicable to our receivables, both from related parties and third-party customers related to the sale of primary aluminum (collectively, “trade receivables”). We do not have any other financial instruments or assets to which the CECL model applies. The adoption of the CECL model did not have a material impact on the Company’s consolidated financial statements. On January 1, 2020, we adopted FASB ASU 2018-13, “Disclosure Framework- Changes to the Disclosure Requirements for Fair Value Measurement” which changed the fair value measurement disclosure requirements of ASC 820. The additional disclosures include a requirement to disclose the range and weighted average used to develop significant unobservable inputs for Level 3 fair value measurements. The new framework also eliminates and modifies certain other fair value disclosures. See Note 4. Fair Value Measurement for updated fair value disclosures in connection with the adoption of this accounting standard. Recently Issued Accounting Standards In December 2019, the FASB issued ASU 2019-12, “Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes." Amendments include the removal of certain exceptions to the general principles of ASC 740 and to improve and simplify accounting for income taxes by clarifying and amending existing guidance. Updates are related to intraperiod tax allocation, interim period tax calculations, tax laws or rate changes in interim periods, and income taxes related to employee stock ownership plans. The ASU is effective for fiscal years beginning after December 15, 2020, including interim periods therein and early adoption is permitted. The Company is currently evaluating the impacts of ASU 2019-12 and we do not expect the adoption to have a material effect on the consolidated financial statements. In March 2020, the Securities and Exchange Commission (“SEC”) issued a final rule that amends the disclosure requirements related to certain registered securities under SEC Regulation S-X Rule 3-10 with respect to the disclosure requirements related to issuers and guarantors of guaranteed debt securities. The final rule allows registrants to provide alternative financial disclosures in either the registrant’s MD&A or financial statements, rather than the previous requirement under Rule 3-10, which required condensed consolidating financial information within the financial statements. It also simplifies the requirements in Rule 3-10 that currently must be met for a parent company to qualify for exceptions allowing it to provide alternative disclosures rather than full audited financial statements. The ruling also reduces the periods for which summarized financial information is required to be presented to the most recent (1) annual period and (2) year-to-date interim period. The final rule applies to annual reports on Form 10-K for fiscal years ending after January 4, 2021 and quarterly reports on Form 10-Q for quarterly periods ending after January 4, 2021 and registrants may voluntarily comply with the final rule before the effective date. The Company does not expect the future adoption, which is limited to disclosures only, to have a material effect on the Company’s consolidated financial statements.
Commitments and contingencies	We have pending against us or may be subject to various lawsuits, claims and proceedings related primarily to employment, commercial, stockholder, environmental, safety and health matters and are involved in other matters that may give rise to contingent liabilities. While the results of such matters and claims cannot be predicted with certainty, we believe that the ultimate outcome of any such matters and claims will not have a material adverse impact on our financial condition, results of operations or liquidity. However, because of the nature and inherent uncertainties of litigation and estimating liabilities, should the resolution or outcome of these actions be unfavorable, our business, financial condition, results of operations and liquidity could be materially and adversely affected. In evaluating whether to accrue for losses associated with legal or environmental contingencies, it is our policy to take into consideration factors such as the facts and circumstances asserted, our historical experience with contingencies of a similar nature, the likelihood of our prevailing and the severity of any potential loss. For some matters, no accrual is established because we have assessed our risk of loss to be remote. Where the risk of loss is probable and the amount of the loss can be reasonably estimated, we record an accrual, either on an individual basis or with respect to a group of matters involving similar claims, based on the factors set forth above. While we regularly review the status of, and our estimates of potential liability associated with, contingencies to determine the adequacy of any associated accruals and related disclosures, the ultimate amount of loss may differ from our estimates.

Related Party Transactions (Tab

Related Party Transactions (Tables)	3 Months Ended
	Mar. 31, 2020
Related Party Transactions [Abstract]
Schedule of related party transactions	A summary of the aforementioned significant related party transactions is as follows: Three months ended March 31, 2020 2019 Net sales to Glencore $ 271.0 $ 311.3 Purchases from Glencore 40.2 90.7 Purchases from BHH (1) — 6.1 (1) We previously owned a 40% interest in Baise Haohai Carbon Co. Ltd. ("BHH") and purchased carbon anodes from them for use in our operations. Purchases represented herein were prior to the divestiture of our interest in BHH on May 22, 2019.

Revenue (Tables)

Revenue (Tables)	3 Months Ended
	Mar. 31, 2020
Revenue Recognition and Deferred Revenue [Abstract]
Disaggregation of revenue	We disaggregate our revenue by geographical region as follows: Net Sales Three months ended March 31, 2020 2019 United States $ 274.1 $ 325.2 Iceland 147.1 164.8 Total $ 421.2 $ 490.0

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Financial assets and liabilities at fair value on a recurring basis	Recurring Fair Value Measurements As of March 31, 2020 Level 1 Level 2 Level 3 Total ASSETS: Cash equivalents $ 89.3 $ — $ — $ 89.3 Trust assets (1) 1.3 — — 1.3 Surety bonds (2) 1.9 — — 1.9 Derivative instruments — 50.5 7.8 58.3 TOTAL $ 92.5 $ 50.5 $ 7.8 $ 150.8 LIABILITIES: Contingent obligation – net $ — $ — $ — $ — Derivative instruments — 36.1 3.2 39.3 TOTAL $ — $ 36.1 $ 3.2 $ 39.3 Recurring Fair Value Measurements As of December 31, 2019 Level 1 Level 2 Level 3 Total ASSETS: Cash equivalents $ 23.3 $ — $ — $ 23.3 Trust assets (1) 0.2 — — 0.2 Surety bonds (2) 1.8 — — 1.8 Derivative instruments — 9.1 10.6 19.7 TOTAL $ 25.3 $ 9.1 $ 10.6 $ 45.0 LIABILITIES: Contingent obligation – net $ — $ — $ — $ — Derivative instruments — 1.3 2.9 4.2 TOTAL $ — $ 1.3 $ 2.9 $ 4.2 (1) Trust assets are currently invested in money market funds. These trust assets are held to fund the non-qualified supplemental executive pension benefit obligations for certain of our officers. (2) Surety bonds are currently invested in U.S. treasury bills and represent collateral against our workers' compensation insurance policy.
Schedule of valuation methodology for assets and liabilities at fair value	We use the following valuation techniques and inputs for fair value measurements categorized within Level 2 of the fair value hierarchy: Level 2 Fair Value Measurements: Asset / Liability Level Valuation Techniques Inputs LME forward financial sales contracts 2 Discounted cash flows Quoted LME forward market MWP forward financial sales contracts 2 Discounted cash flows Quoted MWP forward market Fixed for floating swaps 2 Discounted cash flows Quoted LME forward market, quoted MWP forward market Nord Pool power price swaps 2 Discounted cash flows Quoted Nord Pool forward market NYMEX Henry Hub natural gas price swaps 2 Discounted cash flows Quoted Henry Hub forward market MISO Indiana Hub power price swaps 2 Discounted cash flows Quoted Indy Hub forward market FX swaps 2 Discounted cash flows Euro/USD forward exchange rate When valuing Level 3 assets and liabilities, we use certain significant unobservable inputs. Management incorporates various inputs and assumptions including forward commodity prices, commodity price volatility, and macroeconomic conditions, including interest rates and discount rates. Our estimates of significant unobservable inputs are ultimately based on our estimates of risks that market participants would consider when valuing our assets and liabilities. The following table presents the inputs for fair value measurements categorized within Level 3 of the fair value hierarchy, along with information regarding significant unobservable inputs used to value Level 3 assets and liabilities: Level 3 Fair Value Measurements: Asset / Liability Fair Value at 3/31/2020 Valuation Technique Observable Inputs Significant Unobservable Input Value/Range of Unobservable Input LME forward financial sales contracts $ 7.8 Discounted cash flows Quoted LME forward market prices Discount rate (1) 7.50% Contingent obligation $ — Discounted cash flows Quoted LME forward market prices Management's estimates of the LME forward market price beyond the quoted periods (2) $1,496/T-$2,122/T Hawesville L4 power price swaps $ 3.2 Discounted cash flows Quoted Indy Hub forward market prices Estimates of locational margin prices during contract term (3) $0.58/MwH (1) Represents risk adjusted discount rate. (2) Represents the range of estimated forward LME prices of primary aluminum through the term of the agreement in December 2028. (3) Represents historical average of locational margin prices in the past three years .
Schedule of fair value reconciliation of Level 3 assets and liabilities measured at fair value	The following table presents the fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis. Level 3 Assets Level 3 Liabilities For the three months ended March 31, 2020 LME forward financial sales contracts Hawesville L4 power price swaps Balance as of January 1, 2020 $ 10.6 $ (2.9 ) Total realized/unrealized gains (losses) Included in net income (loss) 6.7 (1.5 ) Purchases, sales, settlements Purchases — — Sales — — Settlements — 1.2 Transfers into Level 3 — — Transfers out of Level 3 (1) (9.5 ) — Balance as of March 31, 2020 $ 7.8 $ (3.2 ) Change in unrealized gains (losses) (2) $ 6.7 $ (0.3 ) (1) Transfer out of Level 3 due to period of time remaining in derivative contract (2) Gains and losses are presented in the Statement of Operations within the line item "Net gain (loss) on forward and derivative contracts" For the three months ended March 31, 2019 Level 3 Assets Level 3 Liabilities Nord Pool power price swaps US LME forward financial sales contracts Iceland LME forward financial sales contracts MWP forward financial sales contracts FX Swaps Balance as of January 1, 2019 $ 4.7 $ 0.3 $ (0.2 ) $ — $ (0.3 ) Total realized/unrealized gains (losses) Included in Net Income (2) (1.0 ) (1.9 ) (0.1 ) (1.7 ) (0.3 ) Purchases, sales, settlements Purchases — — — — — Sales — — — — — Settlements — — — 0.2 — Transfers into Level 3 (1) — (0.2 ) — 0.6 — Transfers out of Level 3 — — — — — Balance as of March 31, 2019 $ 3.7 $ (1.8 ) $ (0.3 ) $ (0.9 ) $ (0.6 ) Change in unrealized gains (losses) (2) $ (1.0 ) $ (2.1 ) $ (0.1 ) $ (0.9 ) $ (0.3 ) (1) Transfer into Level 3 resulting from long term derivative contracts entered into during the first quarter of 2019. (2) Gains and losses are presented in the Statement of Operations within the line item "Net gain (loss) on forward and derivative contracts"

Earnings (Loss) Per Share (Tabl

Earnings (Loss) Per Share (Tables)	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Basic and diluted earnings (loss) per share	(1) In periods when we report a net loss, all share-based compensation awards are excluded from the calculation of diluted weighted average shares outstanding because of their anti-dilutive effect on earnings (loss) per share. The following table shows the basic and diluted earnings (loss) per share: For the three months ended March 31, 2020 2019 Net Income (Loss) Shares (in millions) Per Share Net Income (Loss) Shares (in millions) Per Share Net income (loss) $ (2.7 ) $ (34.6 ) Amount allocated to common stockholders 100.0 % 100.0 % Basic and diluted EPS (1) $ (2.7 ) 89.3 $ (0.03 ) $ (34.6 ) 88.1 $ (0.39 )
Securities excluded from the calculation of diluted EPS	Three months ended March 31, Securities excluded from the calculation of diluted EPS (in millions) (1) : 2020 2019 Share-based compensation 0.4 0.6 (1) In periods when we report a net loss, all share-based compensation awards are excluded from the calculation of diluted weighted average shares outstanding because of their anti-dilutive effect on earnings (loss) per share.

Shareholders_ Equity (Tables)

Shareholders’ Equity (Tables)	3 Months Ended
	Mar. 31, 2020
Stockholders' Equity Note [Abstract]
Common and Preferred Stock Activity	The Common and Preferred Stock table below contains additional information about preferred stock conversions during the three months ended March 31, 2020 and 2019 . Preferred stock Common stock Common and Preferred Stock Activity (in shares): Series A Convertible Treasury Outstanding Beginning balance as of December 31, 2019 67,323 7,186,521 89,185,661 Conversion of convertible preferred stock (1,182 ) — 118,146 Issuance for share-based compensation plans — — 157,158 Ending balance as of March 31, 2020 66,141 7,186,521 89,460,965 Beginning balance as of December 31, 2018 71,967 7,186,521 88,103,440 Conversion of convertible preferred stock (3,023 ) — 302,255 Issuance for share-based compensation plans — — 402,062 Ending balance as of March 31, 2019 68,944 7,186,521 88,807,757

Inventories (Tables)

Inventories (Tables)	3 Months Ended
	Mar. 31, 2020
Inventory, Net [Abstract]
Schedule of Inventories	Inventories consist of the following: March 31, 2020 December 31, 2019 Raw materials $ 94.8 $ 101.3 Work-in-process 46.8 44.1 Finished goods 38.1 34.3 Operating and other supplies 137.9 140.9 Total inventories $ 317.6 $ 320.6

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Schedule of Debt	March 31, 2020 December 31, 2019 Debt classified as current liabilities: Hawesville Term Loan - current portion (1) $ 20.0 $ 20.0 Hancock County industrial revenue bonds ("IRBs") due April 1, 2028, interest payable quarterly (variable interest rates (not to exceed 12%)) (2) 7.8 7.8 U.S. Revolving Credit Facility (3) 45.0 4.0 Debt classified as non-current liabilities: Iceland Revolving Credit Facility (4) 45.0 — 7.5% senior secured notes due June 2021, net of debt discount of $0.7 million and $0.8 million, respectively, interest payable semiannually 249.3 249.2 Hawesville Term Loan - less current portion (1) , principal and interest payable monthly 15.0 20.0 Total $ 382.1 $ 301.0 (1) See "Hawesville Term Loan" below. At March 31, 2020 , the applicable interest rate was LIBOR of 1.68% plus margin of 5.375% and there is no interest payable outstanding. As of March 31, 2020, we have made $5.0 million of principal payments and $0.7 million of interest payments. (2) The IRBs are classified as current liabilities because they are remarketed weekly and could be required to be repaid upon demand if there is a failed remarketing. The IRB interest rate at March 31, 2020 was 5.63% . (3) For borrowings that we expect to repay within a month, we generally elect to incur interest at a base rate plus applicable margin as defined within the agreement. The interest rates at March 31, 2020 was 3.5% . (4) We have elected to incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at March 31, 2020 was 3.8%
Schedule of Line of Credit Facilities	Status of our Iceland revolving credit facility: March 31, 2020 Credit facility maximum amount $ 50.0 Borrowing availability 50.0 Outstanding letters of credit issued — Outstanding borrowings 45.0 Borrowing availability, net of borrowings 5.0 Status of our U.S. revolving credit facility: March 31, 2020 Credit facility maximum amount $ 175.0 Borrowing availability 133.8 Outstanding letters of credit issued 38.3 Outstanding borrowings 45.0 Borrowing availability, net of outstanding letters of credit and borrowings 50.5

Components of Accumulated Oth_2

Components of Accumulated Other Comprehensive Loss (Tables)	3 Months Ended
	Mar. 31, 2020
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated balances for each component of AOCI	Components of AOCL: March 31, 2020 December 31, 2019 Defined benefit plan liabilities $ (114.2 ) $ (115.9 ) Unrealized gain (loss) on financial instruments 2.3 2.3 Other comprehensive loss before income tax effect (111.9 ) (113.6 ) Income tax effect (1) 3.5 3.8 Accumulated other comprehensive loss $ (108.4 ) $ (109.8 ) (1) The allocation of the income tax effect to the components of other comprehensive loss is as follows: March 31, 2020 December 31, 2019 Defined benefit plan liabilities $ 4.0 $ 4.3 Unrealized loss on financial instruments (0.5 ) (0.4 ) The following table summarizes the changes in the accumulated balances for each component of AOCL: Defined benefit plan and other postretirement liabilities Unrealized gain (loss) on financial instruments Total, net of tax Balance, January 1, 2020 $ (111.7 ) $ 1.9 $ (109.8 ) Net amount reclassified to net income (loss) 1.4 0.0 1.4 Balance, March 31, 2020 $ (110.3 ) $ 1.9 $ (108.4 ) Balance, January 1, 2019 $ (100.7 ) $ 2.0 $ (98.7 ) Impact of ASU 2018-02 (2) (1.3 ) — (1.3 ) Net amount reclassified to net income (loss) 0.3 0.0 0.3 Balance, March 31, 2019 $ (101.7 ) $ 2.0 $ (99.7 ) (2) ASU 2018-02. See Note 7. Income Taxes for further information regarding our adoption of ASU 2018-02.
Reclassification out of AOCI	Reclassifications out of AOCL were included in the consolidated statements of operations as follows: Three months ended March 31, AOCL Components Location 2020 2019 Defined benefit plan and other postretirement liabilities Cost of goods sold $ 1.1 $ 0.6 Selling, general and administrative expenses 0.2 (0.4 ) Other operating expense, net 0.4 0.4 Income tax effect (0.3 ) (0.3 ) Net of tax $ 1.4 $ 0.3 Unrealized loss on financial instruments Cost of goods sold $ 0.0 $ 0.0 Income tax effect 0.0 0.0 Net of tax $ 0.0 $ 0.0

Components of Net Periodic Be_2

Components of Net Periodic Benefit Cost (Tables)	3 Months Ended
	Mar. 31, 2020
Components of net periodic benefit cost [Abstract]
Schedule of net periodic benefit cost	Pension Benefits Three months ended March 31, 2020 2019 Service cost $ 1.3 $ 1.1 Interest cost 2.8 3.3 Expected return on plan assets (5.1 ) (4.9 ) Amortization of prior service costs 0.0 0.0 Amortization of net loss 1.5 1.1 Net periodic benefit cost $ 0.5 $ 0.6 Other Postretirement Benefits ("OPEB") Three months ended March 31, 2020 2019 Service cost $ 0.1 $ 0.0 Interest cost 0.8 1.0 Amortization of prior service cost (0.8 ) (1.3 ) Amortization of net loss 1.0 0.8 Net periodic benefit cost $ 1.1 $ 0.5

Derivatives (Tables)

Derivatives (Tables)	3 Months Ended
	Mar. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives Not Designated as Hedging Instruments	The following table sets forth the Company's derivative assets and liabilities that were accounted for at fair value and not designated as cashflow hedges as of March 31, 2020 and December 31, 2019, respectively: Asset Fair Value March 31, 2020 December 31, 2019 Commodity contracts (1) $ 58.3 $ 19.7 Foreign exchange contracts (2) — — Total $ 58.3 $ 19.7 Liability Fair Value March 31, 2020 December 31, 2019 Commodity contracts (1) $ 37.7 $ 3.6 Foreign exchange contracts (2) 1.6 0.6 Total $ 39.3 $ 4.2 (1) Commodity contracts reflect our outstanding LME forward financial sales contracts, MWP forward financial sales contracts, Hawesville L4 power price swaps, fixed for floating swaps, NYMEX Henry Hub natural gas price swaps, MISO Indiana Hub power price swaps, and Nord Pool power price swaps. At March 31, 2020 and December 31, 2019, $ 8.1 million and $ 0.2 million of Due from affiliates and $ 5.1 million and $ 0.5 million of Due from affiliates - less current portion, respectively, is related to commodity contract assets with Glencore. (2) Foreign exchange contracts reflect our outstanding FX swaps.
Schedule of Derivative Instruments	The following table summarizes the net (loss) gain on forward and derivative contracts: Three months ended March 31, 2020 2019 Commodity contracts (3) $ 9.0 $ (5.5 ) Foreign exchange contracts (5.2 ) (0.2 ) Total $ 3.8 $ (5.7 ) (3) For the three months ended March 31, 2020 and 2019, $ 12.6 million and $ (1.0) million

Condensed Consolidating Finan_2

Condensed Consolidating Financial Information (Tables)	3 Months Ended
	Mar. 31, 2020
Condensed Financial Information Disclosure [Abstract]
Condensed Consolidating Statements of Comprehensive Income (Loss)	Condensed Consolidating Statements of Comprehensive Income (Loss) For the three months ended March 31, 2020 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated NET SALES: Related parties $ — $ 147.9 $ 123.1 $ — $ 271.0 Other customers — 126.3 23.9 — 150.2 Total net sales — 274.2 147.0 — 421.2 Cost of goods sold — 281.0 135.4 — 416.4 Gross profit (loss) — (6.8 ) 11.6 — 4.8 Selling, general and administrative expenses 8.4 — 0.5 — 8.9 Other operating (income) expense - net — — 0.3 — 0.3 Operating income (loss) (8.4 ) (6.8 ) 10.8 — (4.4 ) Interest expense - term loan (0.7 ) — — — (0.7 ) Interest expense (5.1 ) (0.4 ) (0.5 ) — (6.0 ) Intercompany interest 8.4 2.7 (11.1 ) — — Interest income — — 0.1 — 0.1 Net gain (loss) on forward and derivative contracts 32.6 0.4 (29.2 ) — 3.8 Other income (expense) - net 0.3 (0.1 ) 1.5 — 1.7 Income (loss) before income taxes and equity in earnings of joint ventures 27.1 (4.2 ) (28.4 ) — (5.5 ) Income tax benefit (expense) 0.5 — 2.3 — 2.8 Income (loss) before equity in earnings of joint ventures 27.6 (4.2 ) (26.1 ) — (2.7 ) Equity in earnings (loss) of joint ventures (30.4 ) 0.5 — 29.9 — Net income (loss) (2.8 ) (3.7 ) (26.1 ) 29.9 (2.7 ) Other comprehensive income before income tax effect 1.7 1.1 0.4 (1.5 ) 1.7 Income tax effect (0.3 ) — — — (0.3 ) Other comprehensive income 1.4 1.1 0.4 (1.5 ) 1.4 Total comprehensive income (loss) $ (1.4 ) $ (2.6 ) $ (25.7 ) $ 28.4 $ (1.3 ) Condensed Consolidating Statements of Comprehensive Income (Loss) For the three months ended March 31, 2019 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated NET SALES: Related parties $ — $ 152.5 $ 158.8 $ — $ 311.3 Other customers — 172.7 6.0 — 178.7 Total net sales — 325.2 164.8 — 490.0 Cost of goods sold — 327.2 175.6 — 502.8 Gross profit (loss) — (2.0 ) (10.8 ) — (12.8 ) Selling, general and administrative expenses 14.1 — 0.6 — 14.7 Other operating (income) expense - net — — 0.3 — 0.3 Operating income (loss) (14.1 ) (2.0 ) (11.7 ) — (27.8 ) Interest expense (5.4 ) (0.4 ) — — (5.8 ) Intercompany interest 8.7 2.5 (11.2 ) — — Interest income — — 0.2 — 0.2 Net gain (loss) on forward and derivative contracts (4.7 ) 0.4 (1.4 ) — (5.7 ) Other income (expense) - net 0.8 (0.5 ) 0.8 — 1.1 Income (loss) before income taxes and equity in earnings of joint ventures (14.7 ) — (23.3 ) — (38.0 ) Income tax (expense) benefit 1.0 — 1.9 — 2.9 Income (loss) before equity in earnings of joint ventures (13.7 ) — (21.4 ) — (35.1 ) Equity in earnings (loss) of joint ventures (20.9 ) 0.3 0.5 20.6 0.5 Net income (loss) (34.6 ) 0.3 (20.9 ) 20.6 (34.6 ) Other comprehensive income (loss) before income tax effect 0.6 0.6 0.3 (0.9 ) 0.6 Income tax effect (0.3 ) — — — (0.3 ) Other comprehensive income 0.3 0.6 0.3 (0.9 ) 0.3 Total comprehensive income (loss) $ (34.3 ) $ 0.9 $ (20.6 ) $ 19.7 $ (34.3 )
Condensed Consolidating Balance Sheet	Condensed Consolidating Balance Sheet As of March 31, 2020 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated Cash & cash equivalents $ 82.5 $ 0.2 $ 64.9 $ — $ 147.6 Restricted cash — 1.8 — — 1.8 Accounts receivable - net 2.2 49.6 1.1 — 52.9 Due from affiliates 7.5 9.6 0.7 — 17.8 Inventories — 187.9 129.7 — 317.6 Derivative Assets 32.7 — — — 32.7 Prepaid and other current assets 4.9 0.5 8.0 — 13.4 Total current assets 129.8 249.6 204.4 — 583.8 Property, plant and equipment - net 16.5 332.8 586.1 — 935.4 Investment in subsidiaries 583.4 63.3 — (646.7 ) — Due from affiliates - long term 734.3 570.0 5.1 (1,304.3 ) 5.1 Other assets 44.7 3.9 18.2 — 66.8 TOTAL $ 1,508.7 $ 1,219.6 $ 813.8 $ (1,951.0 ) $ 1,591.1 Accounts payable, trade $ 3.8 $ 58.1 $ 25.2 $ — $ 87.1 Due to affiliates — 11.1 18.4 — 29.5 Accrued and other current liabilities 17.1 18.4 15.1 — 50.6 Derivative Liabilities 15.5 — 19.0 — 34.5 Accrued employee benefits costs 1.9 7.7 0.8 — 10.4 Term loan - current 20.0 — — — 20.0 U.S. Revolving credit facility 45.0 — — — 45.0 Industrial revenue bonds — 7.8 — — 7.8 Total current liabilities 103.3 103.1 78.5 — 284.9 Senior notes payable 249.3 — — — 249.3 Term loan - less current portion 15.0 — — — 15.0 Iceland Revolving credit facility — — 45.0 — 45.0 Accrued pension benefits costs - less current portion 24.8 26.8 7.7 — 59.3 Accrued postretirement benefits costs - less current portion 1.0 97.3 1.8 — 100.1 Due to affiliates - long term 432.2 320.2 551.9 (1,304.3 ) — Other liabilities 3.9 21.4 21.8 — 47.1 Leases - right of use liabilities 5.4 0.1 16.4 — 21.9 Deferred taxes — 0.4 94.3 — 94.7 Total noncurrent liabilities 731.6 466.2 738.9 (1,304.3 ) 632.4 Preferred stock 0.0 — — — 0.0 Common stock 1.0 — 0.1 (0.1 ) 1.0 Other shareholders' equity 672.8 650.3 (3.7 ) (646.6 ) 672.8 Total shareholders' equity 673.8 650.3 (3.6 ) (646.7 ) 673.8 TOTAL $ 1,508.7 $ 1,219.6 $ 813.8 $ (1,951.0 ) $ 1,591.1 Condensed Consolidating Balance Sheet As of December 31, 2019 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated Cash & cash equivalents $ 0.3 $ 0.1 $ 38.5 $ — $ 38.9 Restricted cash — 0.8 — — 0.8 Accounts receivable - net 0.7 64.1 5.3 — 70.1 Due from affiliates — 10.9 19.2 — 30.1 Inventories — 205.5 115.1 — 320.6 Derivative Assets 12.2 — 2.4 — 14.6 Prepaid and other current assets 3.0 2.8 6.4 — 12.2 Total current assets 16.2 284.2 186.9 — 487.3 Property, plant and equipment - net 17.2 334.8 597.2 — 949.2 Investment in subsidiaries 609.5 62.7 — (672.2 ) — Due from affiliates - long term 749.5 537.9 5.1 (1,292.0 ) 0.5 Other assets 38.1 5.7 18.9 — 62.7 TOTAL $ 1,430.5 $ 1,225.3 $ 808.1 $ (1,964.2 ) $ 1,499.7 Accounts payable, trade $ 2.3 $ 66.2 $ 28.6 $ — $ 97.1 Due to affiliates — 2.2 30.7 — 32.9 Accrued and other current liabilities 23.5 27.3 14.7 — 65.5 Accrued employee benefits costs 1.9 7.7 0.8 — 10.4 Hawesville term loan 20.0 — — — 20.0 Industrial revenue bonds — 7.8 — — 7.8 Total current liabilities 47.7 111.2 74.8 — 233.7 Senior notes payable 249.2 — — — 249.2 Hawesville term loan - less current portion 20.0 — — — 20.0 Accrued pension benefits costs - less current portion 25.1 27.3 8.4 — 60.8 Accrued postretirement benefits costs - less current portion 1.1 97.8 1.8 — 100.7 Leases - right of use liabilities 5.5 0.4 16.9 — 22.8 Other liabilities 3.5 22.2 16.7 — 42.4 Due to affiliates - long term 403.4 315.9 572.7 (1,292.0 ) — Deferred taxes — 0.4 94.7 — 95.1 Total noncurrent liabilities 707.8 464.0 711.2 (1,292.0 ) 591.0 Preferred stock 0.0 — — — 0.0 Common stock 1.0 0.0 0.1 (0.1 ) 1.0 Other shareholders' equity 674.0 650.1 22.0 (672.1 ) 674.0 Total shareholders' equity 675.0 650.1 22.1 (672.2 ) 675.0 TOTAL $ 1,430.5 $ 1,225.3 $ 808.1 $ (1,964.2 ) $ 1,499.7
Condensed Consolidating Statement of Cash Flows	Condensed Consolidating Statement of Cash Flows For the three months ended March 31, 2020 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated Net cash provided by (used in) operating activities $ (13.0 ) $ 34.1 $ 13.5 $ — $ 34.6 Purchase of property, plant and equipment (0.1 ) (5.6 ) (0.3 ) — (6.0 ) Proceeds from sale of property, plant, and equipment — — 0.1 — 0.1 Intercompany transactions 30.5 (29.4 ) (0.1 ) (1.0 ) — Net cash provided by (used in) investing activities 30.4 (35.0 ) (0.3 ) (1.0 ) (5.9 ) Repayments on term loan (5.0 ) — — — (5.0 ) Borrowings under revolving credit facilities 76.8 — 45.0 — 121.8 Repayments under revolving credit facilities (35.8 ) — — — (35.8 ) Intercompany transactions 28.9 1.9 (31.8 ) 1.0 — Net cash provided by (used in) financing activities 64.9 1.9 13.2 1.0 81.0 CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH 82.3 1.0 26.4 — 109.7 Cash, cash equivalents and restricted cash, beginning of period 0.2 1.0 38.5 — 39.7 Cash, cash equivalents and restricted cash, end of period $ 82.5 $ 2.0 $ 64.9 $ — $ 149.4 Condensed Consolidating Statement of Cash Flows For the three months ended March 31, 2019 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated Net cash provided by (used in) operating activities $ (17.6 ) $ (5.3 ) $ 1.4 $ — $ (21.5 ) Purchase of property, plant and equipment (0.6 ) (6.8 ) (3.2 ) — (10.6 ) Intercompany transactions (15.2 ) (17.7 ) 0.1 32.8 — Net cash provided by (used in) investing activities (15.8 ) (24.5 ) (3.1 ) 32.8 (10.6 ) Borrowings under revolving credit facilities 169.6 — — — 169.6 Repayments under revolving credit facilities (157.6 ) — — — (157.6 ) Debt issuance costs 3.4 — — — 3.4 Intercompany transactions 17.8 29.9 (14.9 ) (32.8 ) — Net cash provided by (used in) financing activities 33.2 29.9 (14.9 ) (32.8 ) 15.4 CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH (0.2 ) 0.1 (16.6 ) — (16.7 ) Cash, cash equivalents and restricted cash, beginning of period 0.1 0.8 38.8 — 39.7 Cash, cash equivalents and restricted cash, end of period $ (0.1 ) $ 0.9 $ 22.2 $ — $ 23.0

Related Party Transactions - Na

Related Party Transactions - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Apr. 29, 2019
Related Party Transaction [Line Items]
Related parties	$ 271	$ 311.3
Glencore [Member]
Related Party Transaction [Line Items]
Related parties	271	$ 311.3
Hawesville [Member]
Related Party Transaction [Line Items]
Term loan - less current portion			$ 40
Aluminum [Member] | Glencore [Member]
Related Party Transaction [Line Items]
Related parties	$ 0.3
Consolidated Sales [Member] | Customer Concentration Risk [Member] | Glencore [Member]
Related Party Transaction [Line Items]
Major customer, percentage of revenue, net (percent)	64.00%	64.00%
Glencore [Member]
Related Party Transaction [Line Items]
Ownership percentage by noncontrolling owners	42.90%
Economic ownership percentage by related party	46.80%

Related Party Transactions - Su

Related Party Transactions - Summary of related party transactions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	May 22, 2019
Related Party Transaction [Line Items]
Net sales to Glencore	$ 271	$ 311.3
Glencore [Member]
Related Party Transaction [Line Items]
Net sales to Glencore	271	311.3
Purchases from Glencore	40.2	90.7
BHH [Member]
Related Party Transaction [Line Items]
Purchases from Glencore	$ 0	$ 6.1
Percentage of voting interests sold			40.00%

Revenue (Details)

Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 421.2	$ 490
Decrease in accounts receivable - net	(17.2)	8.4
United States [Member]
Disaggregation of Revenue [Line Items]
Revenue	274.1	325.2
Iceland [Member]
Disaggregation of Revenue [Line Items]
Revenue	147.1	$ 164.8
Trade Accounts Receivable [Member]
Disaggregation of Revenue [Line Items]
Decrease in accounts receivable - net	$ (17.3)

Fair Value Measurements (Detail

Fair Value Measurements (Details) - Fair Value, Recurring [Member] - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
ASSETS:
Cash equivalents	$ 89.3	$ 23.3
Trust assets	1.3	0.2
Surety bonds	1.9	1.8
Derivative instruments	58.3	19.7
TOTAL	150.8	45
LIABILITIES:
Contingent obligation – net	0	0
Derivative instruments	39.3	4.2
TOTAL	39.3	4.2
Fair Value, Inputs, Level 1 [Member]
ASSETS:
Cash equivalents	89.3	23.3
Trust assets	1.3	0.2
Surety bonds	1.9	1.8
Derivative instruments	0	0
TOTAL	92.5	25.3
LIABILITIES:
Contingent obligation – net	0	0
Derivative instruments	0	0
TOTAL	0	0
Fair Value, Inputs, Level 2 [Member]
ASSETS:
Cash equivalents	0	0
Trust assets	0	0
Surety bonds	0	0
Derivative instruments	50.5	9.1
TOTAL	50.5	9.1
LIABILITIES:
Contingent obligation – net	0	0
Derivative instruments	36.1	1.3
TOTAL	36.1	1.3
Fair Value, Inputs, Level 3 [Member]
ASSETS:
Cash equivalents	0	0
Trust assets	0	0
Surety bonds	0	0
Derivative instruments	7.8	10.6
TOTAL	7.8	10.6
LIABILITIES:
Contingent obligation – net	0	0
Derivative instruments	3.2	2.9
TOTAL	$ 3.2	$ 2.9

Fair Value Measurements - Signi

Fair Value Measurements - Significant Unobservable Inputs (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)MWhT	Dec. 31, 2019USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Locational margin price average term	3 years
LME Swap [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value	$ 7.8	$ 10.6
LME Swap [Member] | Discounted Cash Flow [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, percentage	0.075
Contingent obligation [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value	$ 0
Contingent obligation [Member] | Minimum [Member] | Discounted Cash Flow [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset (in tones) | T	1,496
Contingent obligation [Member] | Maximum [Member] | Discounted Cash Flow [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset (in tones) | T	2,122
Hawesville L4 Power Price Swaps [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value	$ (3.2)	$ (2.9)
Hawesville L4 Power Price Swaps [Member] | Discounted Cash Flow [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative liability (in MwH) | MWh	0.58

Fair Value Measurements - Level

Fair Value Measurements - Level 3 Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
LME Swap [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning	$ 10,600
Total realized/unrealized gains (losses)
Included in net income (loss)	6,700
Purchases, sales, settlements
Purchases	0
Sales	0
Settlements	0
Transfers into Level 3	0
Transfers out of Level 3	(9,500)
Balance, ending	7,800
Change in unrealized gains (losses)	6,700
Hawesville L4 Power Price Swaps [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning	(2,900)
Total realized/unrealized gains (losses)
Included in net income (loss)	(1,500)
Purchases, sales, settlements
Purchases	0
Sales	0
Settlements	1,200
Transfers into Level 3	0
Transfers out of Level 3	0
Balance, ending	(3,200)
Change in unrealized gains (losses)	$ (300)
Nordpool Power Price Swap [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning		$ 4,700
Total realized/unrealized gains (losses)
Included in net income (loss)		(1,000)
Purchases, sales, settlements
Purchases		0
Sales		0
Settlements		0
Transfers into Level 3		0
Transfers out of Level 3		0
Balance, ending		3,700
Change in unrealized gains (losses)		(1,000)
Midwest Premium (MWP) [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning		0
Total realized/unrealized gains (losses)
Included in net income (loss)		(1,700)
Purchases, sales, settlements
Purchases		0
Sales		0
Settlements		200
Transfers into Level 3		600
Transfers out of Level 3		0
Balance, ending		(900)
Change in unrealized gains (losses)		(900)
FX Swap [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning		(300)
Total realized/unrealized gains (losses)
Included in net income (loss)		(300)
Purchases, sales, settlements
Purchases		0
Sales		0
Settlements		0
Transfers into Level 3		0
Transfers out of Level 3		0
Balance, ending		(600)
Change in unrealized gains (losses)		(300)
United States [Member] | LME Swap [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning		300
Total realized/unrealized gains (losses)
Included in net income (loss)		(1,900)
Purchases, sales, settlements
Purchases		0
Sales		0
Settlements		0
Transfers into Level 3		(200)
Transfers out of Level 3		0
Balance, ending		(1,800)
Change in unrealized gains (losses)		(2,100)
Iceland [Member] | LME Swap [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning		(200)
Total realized/unrealized gains (losses)
Included in net income (loss)		(100)
Purchases, sales, settlements
Purchases		0
Sales		0
Settlements		0
Transfers into Level 3		0
Transfers out of Level 3		0
Balance, ending		(300)
Change in unrealized gains (losses)		$ (100)

Earnings (Loss) Per Share (Deta

Earnings (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Net income (loss)	$ (2.7)	$ (34.6)
Amount allocated to common stockholders (as percent)	100.00%	100.00%
Basic and diluted EPS
Net income (loss) allocated to common stockholders (shares)	89.3	88.1
Basic and diluted (per share)	$ (0.03)	$ (0.39)
Securities excluded from calculation of diluted EPS (shares)	0.4	0.6

Shareholders_ Equity (Details)

Shareholders’ Equity (Details) - USD ($)	3 Months Ended		60 Months Ended	111 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2015	Dec. 31, 2011	Dec. 31, 2008
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	195,000,000		195,000,000	195,000,000	195,000,000
Common stock, par value (in dollars per share)	$ 0.01		$ 0.01	$ 0.01	$ 0.01
Common stock, shares issued (in shares)	96,647,486		96,647,486	96,647,486	96,372,182
Common stock, shares, outstanding (in shares)	89,460,965		89,460,965	89,460,965	89,185,661
Preferred stock, shares authorized (in shares)	5,000,000		5,000,000	5,000,000	5,000,000
Preferred stock par value (in dollars per share)	$ 0.01		$ 0.01	$ 0.01	$ 0.01
Preferred shares issued (in shares)								160,000
Number of shares issued for each share of preferred stock (in shares)	100		100	100
Stock repurchase program, authorized amount	$ 130,000,000		$ 130,000,000	$ 130,000,000		$ 70,000,000	$ 60,000,000
Treasury stock, shares, acquired (in shares)			0	7,186,521
Treasury stock, value, acquired, cost method				$ 86,300,000
Stock repurchase program, remaining authorized repurchase amount	$ 43,700,000		$ 43,700,000	$ 43,700,000
Series A Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Preferred shares outstanding (in shares)	66,141		66,141	66,141	67,323
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, Beginning balance (in shares)	67,323	71,967
Conversion of convertible preferred stock (in shares)	(1,182)	(3,023)
Issuance for stock compensation plans (in shares)	0	0
Shares, Ending balance (in shares)	66,141	68,944	66,141	66,141
Treasury [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, Beginning balance (in shares)	7,186,521	7,186,521
Conversion of convertible preferred stock (in shares)	0	0
Issuance for stock compensation plans (in shares)	0	0
Shares, Ending balance (in shares)	7,186,521	7,186,521	7,186,521	7,186,521
Common stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, Beginning balance (in shares)	89,185,661	88,103,440
Conversion of convertible preferred stock (in shares)	118,146	302,255
Issuance for stock compensation plans (in shares)	157,158	402,062
Shares, Ending balance (in shares)	89,460,965	88,807,757	89,460,965	89,460,965

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019	Jan. 01, 2019
Income Tax Disclosure [Abstract]
Income tax benefit		$ 2.8	$ 2.9
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impact of ASU 2018-02	[1]			$ 0
Accounting Standards Update 2018-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impact of ASU 2018-02				$ 1.3
[1]	ASU 2018-02. See Note 7. Income Taxes for further information regarding our adoption of ASU 2018-02.

Inventories (Details)

Inventories (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Inventory, Net [Abstract]
Raw materials	$ 94.8	$ 101.3
Work-in-process	46.8	44.1
Finished goods	38.1	34.3
Operating and other supplies	137.9	140.9
Total inventories	$ 317.6	$ 320.6

Debt (Details)

Debt (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Jun. 04, 2013
Debt Instrument [Line Items]
Hawesville term loan - current portion	$ 20,000,000	$ 20,000,000
Hancock County industrial revenue bonds (IRBs) due April 1, 2028, interest payable quarterly (variable interest rates (not to exceed 12%))	7,800,000	7,800,000
Hawesville term loan - less current portion, interest payable monthly	15,000,000	20,000,000
Total debt	382,100,000	301,000,000
Hawesville [Member]
Debt Instrument [Line Items]
Hawesville term loan - current portion	20,000,000	20,000,000
Hawesville term loan - less current portion, interest payable monthly	15,000,000	20,000,000
Long-term Debt [Member] | Senior secured notes due June 01, 2021 [Member]
Debt Instrument [Line Items]
7.5% senior secured notes due June 2021, net of debt discount of $0.7 million and $0.8 million, respectively, interest payable semiannually	$ 249,300,000	249,200,000
Maturity date	Jun. 1, 2021
Stated interest rate, percentage	7.50%		7.50%
Debt discount	$ 700,000	800,000
Short-term Debt [Member] | Industrial revenue bonds due April 1, 2028 [Member]
Debt Instrument [Line Items]
Hancock County industrial revenue bonds (IRBs) due April 1, 2028, interest payable quarterly (variable interest rates (not to exceed 12%))	$ 7,800,000	7,800,000
Maturity date	Apr. 1, 2028
Stated interest rate, percentage	5.63%
Short-term Debt [Member] | Industrial revenue bonds due April 1, 2028 [Member] | Maximum [Member]
Debt Instrument [Line Items]
Effective interest rate, maximum	12.00%
Short-term Debt [Member] | Revolving credit facility [Member]
Debt Instrument [Line Items]
Stated interest rate, percentage	5.375%
Interest payable outstanding	$ 0
Principal payment	5,000,000
Interest payable	$ 700,000
Short-term Debt [Member] | Revolving credit facility [Member] | Revolving Credit Facility, Portion Subject To LIBOR Rate [Member]
Debt Instrument [Line Items]
Stated interest rate, percentage	1.68%
U.S. revolving credit facility [Member] | Short-term Debt [Member] | Revolving credit facility [Member]
Debt Instrument [Line Items]
Revolving credit facility	$ 45,000,000	4,000,000
Stated interest rate, percentage	3.50%
Iceland revolving line of credit [Member] | Short-term Debt [Member] | Revolving credit facility [Member]
Debt Instrument [Line Items]
Revolving credit facility	$ 45,000,000
Revolving credit facility	$ 45,000,000	$ 0
Stated interest rate, percentage	3.80%

Debt - Credit Facility (Details

Debt - Credit Facility (Details)	Apr. 29, 2019USD ($)payment	Jun. 30, 2013USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Jun. 04, 2013USD ($)
Line of Credit Facility [Line Items]
Fair value of debt instrument			$ 228,500,000	$ 244,200,000
U.S. revolving credit facility [Member]
Line of Credit Facility [Line Items]
Credit facility maximum amount			175,000,000
Borrowing availability			133,800,000
Borrowing availability, net of outstanding letters of credit and borrowings			38,300,000
U.S. revolving credit facility [Member] | Long-term Debt [Member]
Line of Credit Facility [Line Items]
Credit facility face amount			175,000,000
U.S. letter of credit [Member]
Line of Credit Facility [Line Items]
Letter of credit sub-facility amount			50,500,000
U.S. letter of credit [Member] | Long-term Debt [Member]
Line of Credit Facility [Line Items]
Letter of credit sub-facility amount			110,000,000
U.S. revolving credit facility, accordion [Member] | Long-term Debt [Member]
Line of Credit Facility [Line Items]
Credit facility face amount			50,000,000
Iceland revolving line of credit [Member] | Long-term Debt [Member]
Line of Credit Facility [Line Items]
Credit facility maximum amount			50,000,000
Borrowing availability			50,000,000
Borrowing availability, net of outstanding letters of credit and borrowings			0
Borrowing availability, net of borrowings			$ 5,000,000
Senior secured notes due June 01, 2021 [Member] | Long-term Debt [Member]
Line of Credit Facility [Line Items]
Face amount					$ 250,000,000
Stated interest rate, percentage			7.50%		7.50%
Proceeds from issuance of debt		$ 246,300,000
Short-term Debt [Member] | U.S. letter of credit [Member]
Line of Credit Facility [Line Items]
Outstanding borrowings			$ 45,000,000
Short-term Debt [Member] | Iceland revolving line of credit [Member]
Line of Credit Facility [Line Items]
Outstanding borrowings			$ 45,000,000
Short-term Debt [Member] | Revolving credit facility [Member]
Line of Credit Facility [Line Items]
Stated interest rate, percentage			5.375%
Short-term Debt [Member] | Revolving credit facility [Member] | U.S. revolving credit facility [Member]
Line of Credit Facility [Line Items]
Stated interest rate, percentage			3.50%
U.S revolving credit facility			$ 45,000,000	$ 4,000,000
Debt, financial covenant, fixed coverage ratio			1
Debt, financial covenant, amount			$ 17,500,000
Debt, financial covenant, borrowing base, percentage			10.00%
Debt, financial covenant, borrowing base, minimum			$ 12,500,000
Short-term Debt [Member] | Revolving credit facility [Member] | Iceland revolving line of credit [Member]
Line of Credit Facility [Line Items]
Stated interest rate, percentage			3.80%
U.S revolving credit facility			$ 45,000,000
Hawesville [Member]
Line of Credit Facility [Line Items]
Due to related parties, noncurrent	$ 40,000,000
Debt instrument, payment terms, number of monthly payments | payment	24
London Interbank Offered Rate (LIBOR) [Member] | Hawesville [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	5.375%

Commitments and Contingencies (

Commitments and Contingencies (Details)	Aug. 18, 2017USD ($)	Sep. 30, 2017USD ($)	Mar. 31, 2020USD ($)Labor_UnionMW	Mar. 31, 2019USD ($)	Dec. 31, 2013USD ($)
Labor Commitments [Abstract]
Percentage of total work force in union			65.00%
Percentage of Grundartangi work force represented by the labor unions (in hundredths)			86.00%
Number of labor unions Grundartangi subsidiary entered into a new labor agreement with | Labor_Union			5
Percentage of U.S. based work force represented by a union (in hundredths)			57.00%
Ravenswood Retiree Medical Benefits Changes [Member]
Ravenswood litigation [Abstract]
Gain (loss) related to litigation settlement		$ 5,500,000
Loss contingency accrual		12,500,000
PBGC Agreement [Member]
PBGC Settlement [Abstract]
Required pension contributions above minimum					$ 17,400,000
Payment for pension benefits			$ 0	$ 0
Pension contributions above minimum remaining			$ 9,600,000
Hawesville [Member]
Power Contingencies [Abstract]
Power supply agreement, termination notice period			1 year
Sebree [Member]
Power Contingencies [Abstract]
Power supply agreement, termination notice period			1 year
South Carolina Public Service Authority [Member]
Power Contingencies [Abstract]
Power agreement, power supply from source one, percentage			25.00%
Power agreement, power supply from source two, percentage			75.00%
Power supply agreement, termination notice period			120 days
Other Power Suppliers [Member]
Power Contingencies [Abstract]
Power supply agreement, termination notice period			60 days
Grundartangi - HS, Landsvirkjun and OR [Member]
Power Contingencies [Abstract]
Power currently available under the power purchase agreement (in megawatts) | MW			525
Grundartangi - Landsvirkjun [Member]
Power Contingencies [Abstract]
Power currently available under the power purchase agreement (in megawatts) | MW			161
Helguvik [Member]
Power Contingencies [Abstract]
Power currently available under the power purchase agreement (in megawatts) | MW			47.5
NETHERLANDS
Labor Commitments [Abstract]
Percentage of Vlissingen work force represented by the labor union (in hundredths)			100.00%
Ravenswood Retiree Medical Benefits Changes [Member]
Ravenswood litigation [Abstract]
Ravenswood litigation settlement amount	$ 23,000,000
Ravenswood litigation settlement installment period	10 years		9 years
Litigation payment to trust		$ 5,000,000
Litigation settlement, amount awarded to other party, annual payments			$ 2,000,000
Other Current Liabilities [Member] | Ravenswood Retiree Medical Benefits Changes [Member]
Ravenswood litigation [Abstract]
Litigation settlement, amount awarded to other party, annual payments			2,000,000
Other Liabilities [Member] | Ravenswood Retiree Medical Benefits Changes [Member]
Ravenswood litigation [Abstract]
Litigation settlement, amount awarded to other party, annual payments			$ 8,900,000

Components of Accumulated Oth_3

Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive loss before income tax effect	$ (111.9)		$ (113.6)
Income tax effect	3.5		3.8
Accumulated other comprehensive loss	(108.4)		(109.8)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, start	675	$ 762.2
Balance, end	673.8	728.1
Defined benefit plan and other postretirement liabilities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive loss before income tax effect	(114.2)		(115.9)
Income tax effect	(4)		(4.3)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, start	(111.7)	(100.7)
Impact of ASU 2018-02		(1.3)
Net amount reclassified to net income (loss)	1.4	0.3
Balance, end	(110.3)	(101.7)
Unrealized gain (loss) on financial instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive loss before income tax effect	2.3		2.3
Income tax effect	0.5		$ 0.4
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, start	1.9	2
Impact of ASU 2018-02		0
Net amount reclassified to net income (loss)	0	0
Balance, end	1.9	2
Accumulated other comprehensive loss [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, start	(109.8)	(98.7)
Impact of ASU 2018-02		(1.3)
Net amount reclassified to net income (loss)	1.4	0.3
Balance, end	$ (108.4)	$ (99.7)

Components of Accumulated Oth_4

Components of Accumulated Other Comprehensive Loss - Reclassifications out of AOCI (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Cost of goods sold	$ 416.4	$ 502.8
Selling, general and administrative expenses	8.9	14.7
Other operating expense, net	0.3	0.3
Income tax effect	(2.8)	(2.9)
Net of tax	2.7	34.6
Reclassification out of Accumulated Other Comprehensive Income [Member] | Defined benefit plan and other postretirement liabilities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Cost of goods sold	1.1	0.6
Selling, general and administrative expenses	0.2	(0.4)
Other operating expense, net	0.4	0.4
Income tax effect	(0.3)	(0.3)
Net of tax	1.4	0.3
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized loss on financial instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Cost of goods sold	0	0
Income tax effect	0	0
Net of tax	$ 0	$ 0

Components of Net Periodic Be_3

Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 1.3	$ 1.1
Interest cost	2.8	3.3
Expected return on plan assets	(5.1)	(4.9)
Amortization of prior service costs	0	0
Amortization of net loss	1.5	1.1
Net periodic benefit cost	0.5	0.6
Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	0.1	0
Interest cost	0.8	1
Amortization of prior service costs	(0.8)	(1.3)
Amortization of net loss	1	0.8
Net periodic benefit cost	$ 1.1	$ 0.5

Derivatives (Details)

Derivatives (Details) € in Millions	3 Months Ended
	Mar. 31, 2020EUR (€)MMBTUMWht
Derivative [Line Items]
Percentage of exposure hedged by derivatives (percent)	50.00%
LME Swap [Member]
Derivative [Line Items]
Other forward delivery contracts to sell primary aluminum, open (in tonnes) | t	145,402
Midwest Premium (MWP) [Member]
Derivative [Line Items]
Open position to offset fixed prices | t	117,000
Hawesville L4 Power Price Swaps [Member]
Derivative [Line Items]
Power available | MWh	592,920
NYMEX Henry Hub Natural Gas Price Swaps [Member]
Derivative [Line Items]
Power available | MMBTU	2,340,000
MISO Indiana Hub Power Price Swaps [Member]
Derivative [Line Items]
Power available | MWh	1,471,320
Fixed For Floating Swaps [Member]
Derivative [Line Items]
Open position to offset fixed prices | t	15,271
Nordpool Power Price Swap [Member] | Grundartangi [Member]
Derivative [Line Items]
Power available | MWh	1,693,958
Percentage of power purchases included in forward price contract, future (percent)	50.00%
FX Swap [Member]
Derivative [Line Items]
Derivative asset | €	€ 44.6

Derivatives - Assets and Liabil

Derivatives - Assets and Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Due from affiliates	$ 17.8	$ 30.1
Due from affiliates - less current portion	5.1	0.5
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative asset	58.3	19.7
Derivative liability	39.3	4.2
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivative [Line Items]
Derivative asset	58.3	19.7
Derivative liability	37.7	3.6
Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative asset	0	0
Derivative liability	1.6	0.6
Glencore [Member] | Commodity Contract [Member]
Derivative [Line Items]
Due from affiliates	8.1	0.2
Due from affiliates - less current portion	$ 5.1	$ 0.5

Derivatives - Net Gain (Loss) (

Derivatives - Net Gain (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Derivative [Line Items]
Derivative, (loss) gain on derivative, net	$ 3.8	$ (5.7)
Commodity Contract [Member]
Derivative [Line Items]
Derivative, (loss) gain on derivative, net	9	(5.5)
Commodity Contract [Member] | Glencore [Member]
Derivative [Line Items]
Derivative, (loss) gain on derivative, net	12.6	(1)
Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative, (loss) gain on derivative, net	$ (5.2)	$ (0.2)

Condensed Consolidating Finan_3

Condensed Consolidating Financial Information - Statement of Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
NET SALES
Related parties	$ 271	$ 311.3
Other customers	150.2	178.7
Total net sales	421.2	490
Cost of goods sold	416.4	502.8
Gross profit (loss)	4.8	(12.8)
Selling, general and administrative expenses	8.9	14.7
Other operating (income) expense - net	0.3	0.3
Operating income (loss)	(4.4)	(27.8)
Interest expense - term loan	(0.7)	0
Interest expense	(6)	(5.8)
Intercompany interest	0	0
Interest income	0.1	0.2
Net gain (loss) on forward and derivative contracts	3.8	(5.7)
Other income (expense) - net	1.7	1.1
Income (loss) before income taxes and equity in earnings of joint ventures	(5.5)	(38)
Income tax benefit (expense)	2.8	2.9
Income (loss) before equity in earnings of joint ventures	(2.7)	(35.1)
Equity in earnings of joint ventures	0	0.5
Net income (loss)	(2.7)	(34.6)
Other comprehensive income before income tax effect	1.7	0.6
Income tax effect	(0.3)	(0.3)
Other comprehensive income (loss)	1.4	0.3
Total comprehensive income (loss)	(1.3)	(34.3)
Consolidating Adjustments [Member]
NET SALES
Related parties	0	0
Other customers	0	0
Total net sales	0	0
Cost of goods sold	0	0
Gross profit (loss)	0	0
Selling, general and administrative expenses	0	0
Other operating (income) expense - net	0	0
Operating income (loss)	0	0
Interest expense - term loan	0
Interest expense	0	0
Intercompany interest	0	0
Interest income	0	0
Net gain (loss) on forward and derivative contracts	0	0
Other income (expense) - net	0	0
Income (loss) before income taxes and equity in earnings of joint ventures	0	0
Income tax benefit (expense)	0	0
Income (loss) before equity in earnings of joint ventures	0	0
Equity in earnings of joint ventures	29.9	20.6
Net income (loss)	29.9	20.6
Other comprehensive income before income tax effect	(1.5)	(0.9)
Income tax effect	0	0
Other comprehensive income (loss)	(1.5)	(0.9)
Total comprehensive income (loss)	28.4	19.7
The Company [Member] | Reportable Legal Entities [Member]
NET SALES
Related parties	0	0
Other customers	0	0
Total net sales	0	0
Cost of goods sold	0	0
Gross profit (loss)	0	0
Selling, general and administrative expenses	8.4	14.1
Other operating (income) expense - net	0	0
Operating income (loss)	(8.4)	(14.1)
Interest expense - term loan	(0.7)
Interest expense	(5.1)	(5.4)
Intercompany interest	8.4	8.7
Interest income	0	0
Net gain (loss) on forward and derivative contracts	32.6	(4.7)
Other income (expense) - net	0.3	0.8
Income (loss) before income taxes and equity in earnings of joint ventures	27.1	(14.7)
Income tax benefit (expense)	0.5	1
Income (loss) before equity in earnings of joint ventures	27.6	(13.7)
Equity in earnings of joint ventures	(30.4)	(20.9)
Net income (loss)	(2.8)	(34.6)
Other comprehensive income before income tax effect	1.7	0.6
Income tax effect	(0.3)	(0.3)
Other comprehensive income (loss)	1.4	0.3
Total comprehensive income (loss)	(1.4)	(34.3)
Combined Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
NET SALES
Related parties	147.9	152.5
Other customers	126.3	172.7
Total net sales	274.2	325.2
Cost of goods sold	281	327.2
Gross profit (loss)	(6.8)	(2)
Selling, general and administrative expenses	0	0
Other operating (income) expense - net	0	0
Operating income (loss)	(6.8)	(2)
Interest expense - term loan	0
Interest expense	(0.4)	(0.4)
Intercompany interest	2.7	2.5
Interest income	0	0
Net gain (loss) on forward and derivative contracts	0.4	0.4
Other income (expense) - net	(0.1)	(0.5)
Income (loss) before income taxes and equity in earnings of joint ventures	(4.2)	0
Income tax benefit (expense)	0	0
Income (loss) before equity in earnings of joint ventures	(4.2)	0
Equity in earnings of joint ventures	0.5	0.3
Net income (loss)	(3.7)	0.3
Other comprehensive income before income tax effect	1.1	0.6
Income tax effect	0	0
Other comprehensive income (loss)	1.1	0.6
Total comprehensive income (loss)	(2.6)	0.9
Combined Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
NET SALES
Related parties	123.1	158.8
Other customers	23.9	6
Total net sales	147	164.8
Cost of goods sold	135.4	175.6
Gross profit (loss)	11.6	(10.8)
Selling, general and administrative expenses	0.5	0.6
Other operating (income) expense - net	0.3	0.3
Operating income (loss)	10.8	(11.7)
Interest expense - term loan	0
Interest expense	(0.5)	0
Intercompany interest	(11.1)	(11.2)
Interest income	0.1	0.2
Net gain (loss) on forward and derivative contracts	(29.2)	(1.4)
Other income (expense) - net	1.5	0.8
Income (loss) before income taxes and equity in earnings of joint ventures	(28.4)	(23.3)
Income tax benefit (expense)	2.3	1.9
Income (loss) before equity in earnings of joint ventures	(26.1)	(21.4)
Equity in earnings of joint ventures	0	0.5
Net income (loss)	(26.1)	(20.9)
Other comprehensive income before income tax effect	0.4	0.3
Income tax effect	0	0
Other comprehensive income (loss)	0.4	0.3
Total comprehensive income (loss)	$ (25.7)	$ (20.6)
Century Aluminum [Member] | Combined Guarantor Subsidiaries [Member]
Condensed Statement of Income Captions [Line Items]
Ownership percentage	100.00%

Condensed Consolidating Finan_4

Condensed Consolidating Financial Information - Balance Sheet (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Condensed Balance Sheet Statements, Captions [Line Items]
Cash & cash equivalents	$ 147.6	$ 38.9
Restricted cash	1.8	0.8
Accounts receivable - net	52.9	70.1
Due from affiliates	17.8	30.1
Inventories	317.6	320.6
Derivative assets	32.7	14.6
Prepaid and other current assets	13.4	12.2
Total current assets	583.8	487.3
Property, plant and equipment - net	935.4	949.2
Investment in subsidiaries	0	0
Due from affiliates - long term	5.1	0.5
Other assets	66.8	62.7
TOTAL	1,591.1	1,499.7
Accounts payable, trade	87.1	97.1
Due to affiliates	29.5	32.9
Accrued and other current liabilities	50.6	65.5
Derivative liabilities	34.5	4.3
Accrued employee benefits costs	10.4	10.4
Hawesville term loan	20	20
U.S. revolving credit facility	45	4
Industrial revenue bonds	7.8	7.8
Total current liabilities	284.9	233.7
Senior notes payable	249.3	249.2
Hawesville term loan - less current portion	15	20
Iceland revolving credit facility	45	0
Accrued pension benefits costs - less current portion	59.3	60.8
Accrued postretirement benefits costs - less current portion	100.1	100.7
Due to affiliates - long term	0	0
Other liabilities	47.1	42.4
Leases - right of use liabilities	21.9	22.8
Deferred taxes	94.7	95.1
Total noncurrent liabilities	632.4	591
Preferred stock	0	0
Common stock	1	1
Other shareholders' equity	672.8	674
Total shareholders’ equity	673.8	675	$ 728.1	$ 762.2
TOTAL	1,591.1	1,499.7
Consolidating Adjustments [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash & cash equivalents	0	0
Restricted cash	0	0
Accounts receivable - net	0	0
Due from affiliates	0	0
Inventories	0	0
Derivative assets	0	0
Prepaid and other current assets	0	0
Total current assets	0	0
Property, plant and equipment - net	0	0
Investment in subsidiaries	(646.7)	(672.2)
Due from affiliates - long term	(1,304.3)	(1,292)
Other assets	0	0
TOTAL	(1,951)	(1,964.2)
Accounts payable, trade	0	0
Due to affiliates	0	0
Accrued and other current liabilities	0	0
Derivative liabilities	0
Accrued employee benefits costs	0	0
Hawesville term loan	0	0
U.S. revolving credit facility	0
Industrial revenue bonds	0	0
Total current liabilities	0	0
Senior notes payable	0	0
Hawesville term loan - less current portion	0	0
Iceland revolving credit facility	0
Accrued pension benefits costs - less current portion	0	0
Accrued postretirement benefits costs - less current portion	0	0
Due to affiliates - long term	(1,304.3)	(1,292)
Other liabilities	0	0
Leases - right of use liabilities	0	0
Deferred taxes	0	0
Total noncurrent liabilities	(1,304.3)	(1,292)
Preferred stock	0	0
Common stock	(0.1)	(0.1)
Other shareholders' equity	(646.6)	(672.1)
Total shareholders’ equity	(646.7)	(672.2)
TOTAL	(1,951)	(1,964.2)
The Company [Member] | Reportable Legal Entities [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash & cash equivalents	82.5	0.3
Restricted cash	0	0
Accounts receivable - net	2.2	0.7
Due from affiliates	7.5	0
Inventories	0	0
Derivative assets	32.7	12.2
Prepaid and other current assets	4.9	3
Total current assets	129.8	16.2
Property, plant and equipment - net	16.5	17.2
Investment in subsidiaries	583.4	609.5
Due from affiliates - long term	734.3	749.5
Other assets	44.7	38.1
TOTAL	1,508.7	1,430.5
Accounts payable, trade	3.8	2.3
Due to affiliates	0	0
Accrued and other current liabilities	17.1	23.5
Derivative liabilities	15.5
Accrued employee benefits costs	1.9	1.9
Hawesville term loan	20	20
U.S. revolving credit facility	45
Industrial revenue bonds	0	0
Total current liabilities	103.3	47.7
Senior notes payable	249.3	249.2
Hawesville term loan - less current portion	15	20
Iceland revolving credit facility	0
Accrued pension benefits costs - less current portion	24.8	25.1
Accrued postretirement benefits costs - less current portion	1	1.1
Due to affiliates - long term	432.2	403.4
Other liabilities	3.9	3.5
Leases - right of use liabilities	5.4	5.5
Deferred taxes	0	0
Total noncurrent liabilities	731.6	707.8
Preferred stock	0	0
Common stock	1	1
Other shareholders' equity	672.8	674
Total shareholders’ equity	673.8	675
TOTAL	1,508.7	1,430.5
Combined Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash & cash equivalents	0.2	0.1
Restricted cash	1.8	0.8
Accounts receivable - net	49.6	64.1
Due from affiliates	9.6	10.9
Inventories	187.9	205.5
Derivative assets	0	0
Prepaid and other current assets	0.5	2.8
Total current assets	249.6	284.2
Property, plant and equipment - net	332.8	334.8
Investment in subsidiaries	63.3	62.7
Due from affiliates - long term	570	537.9
Other assets	3.9	5.7
TOTAL	1,219.6	1,225.3
Accounts payable, trade	58.1	66.2
Due to affiliates	11.1	2.2
Accrued and other current liabilities	18.4	27.3
Derivative liabilities	0
Accrued employee benefits costs	7.7	7.7
Hawesville term loan	0	0
U.S. revolving credit facility	0
Industrial revenue bonds	7.8	7.8
Total current liabilities	103.1	111.2
Senior notes payable	0	0
Hawesville term loan - less current portion	0	0
Iceland revolving credit facility	0
Accrued pension benefits costs - less current portion	26.8	27.3
Accrued postretirement benefits costs - less current portion	97.3	97.8
Due to affiliates - long term	320.2	315.9
Other liabilities	21.4	22.2
Leases - right of use liabilities	0.1	0.4
Deferred taxes	0.4	0.4
Total noncurrent liabilities	466.2	464
Preferred stock	0	0
Common stock	0	0
Other shareholders' equity	650.3	650.1
Total shareholders’ equity	650.3	650.1
TOTAL	1,219.6	1,225.3
Combined Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash & cash equivalents	64.9	38.5
Restricted cash	0	0
Accounts receivable - net	1.1	5.3
Due from affiliates	0.7	19.2
Inventories	129.7	115.1
Derivative assets	0	2.4
Prepaid and other current assets	8	6.4
Total current assets	204.4	186.9
Property, plant and equipment - net	586.1	597.2
Investment in subsidiaries	0	0
Due from affiliates - long term	5.1	5.1
Other assets	18.2	18.9
TOTAL	813.8	808.1
Accounts payable, trade	25.2	28.6
Due to affiliates	18.4	30.7
Accrued and other current liabilities	15.1	14.7
Derivative liabilities	19
Accrued employee benefits costs	0.8	0.8
Hawesville term loan	0	0
U.S. revolving credit facility	0
Industrial revenue bonds	0	0
Total current liabilities	78.5	74.8
Senior notes payable	0	0
Hawesville term loan - less current portion	0	0
Iceland revolving credit facility	45
Accrued pension benefits costs - less current portion	7.7	8.4
Accrued postretirement benefits costs - less current portion	1.8	1.8
Due to affiliates - long term	551.9	572.7
Other liabilities	21.8	16.7
Leases - right of use liabilities	16.4	16.9
Deferred taxes	94.3	94.7
Total noncurrent liabilities	738.9	711.2
Preferred stock	0	0
Common stock	0.1	0.1
Other shareholders' equity	(3.7)	22
Total shareholders’ equity	(3.6)	22.1
TOTAL	$ 813.8	$ 808.1

Condensed Consolidating Finan_5

Condensed Consolidating Financial Information - Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	$ 34.6	$ (21.5)
Net cash provided by (used in) investing activities
Purchase of property, plant and equipment	(6)	(10.6)
Proceeds from sale of joint venture	0.1
Intercompany transactions	0	0
Net cash provided by (used in) investing activities	(5.9)	(10.6)
Net cash provided by (used in) financing activities
Repayments on term loan	(5)	0
Borrowings under revolving credit facilities	121.8	169.6
Repayments under revolving credit facilities	(35.8)	(157.6)
Debt issuance costs		3.4
Intercompany transactions	0	0
Net cash provided by (used in) financing activities	81	15.4
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	109.7	(16.7)
Cash, cash equivalents and restricted cash, beginning of period	39.7	39.7
Cash, cash equivalents and restricted cash, end of period	149.4	23
Consolidating Adjustments [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	0	0
Net cash provided by (used in) investing activities
Purchase of property, plant and equipment	0	0
Proceeds from sale of joint venture	0
Intercompany transactions	(1)	32.8
Net cash provided by (used in) investing activities	(1)	32.8
Net cash provided by (used in) financing activities
Repayments on term loan	0
Borrowings under revolving credit facilities	0	0
Repayments under revolving credit facilities	0	0
Debt issuance costs		0
Intercompany transactions	1	(32.8)
Net cash provided by (used in) financing activities	1	(32.8)
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	0	0
Cash, cash equivalents and restricted cash, beginning of period	0	0
Cash, cash equivalents and restricted cash, end of period	0	0
The Company [Member] | Reportable Legal Entities [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	(13)	(17.6)
Net cash provided by (used in) investing activities
Purchase of property, plant and equipment	(0.1)	(0.6)
Proceeds from sale of joint venture	0
Intercompany transactions	30.5	(15.2)
Net cash provided by (used in) investing activities	30.4	(15.8)
Net cash provided by (used in) financing activities
Repayments on term loan	(5)
Borrowings under revolving credit facilities	76.8	169.6
Repayments under revolving credit facilities	(35.8)	(157.6)
Debt issuance costs		3.4
Intercompany transactions	28.9	17.8
Net cash provided by (used in) financing activities	64.9	33.2
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	82.3	(0.2)
Cash, cash equivalents and restricted cash, beginning of period	0.2	0.1
Cash, cash equivalents and restricted cash, end of period	82.5	(0.1)
Combined Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	34.1	(5.3)
Net cash provided by (used in) investing activities
Purchase of property, plant and equipment	(5.6)	(6.8)
Proceeds from sale of joint venture	0
Intercompany transactions	(29.4)	(17.7)
Net cash provided by (used in) investing activities	(35)	(24.5)
Net cash provided by (used in) financing activities
Repayments on term loan	0
Borrowings under revolving credit facilities	0	0
Repayments under revolving credit facilities	0	0
Debt issuance costs		0
Intercompany transactions	1.9	29.9
Net cash provided by (used in) financing activities	1.9	29.9
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	1	0.1
Cash, cash equivalents and restricted cash, beginning of period	1	0.8
Cash, cash equivalents and restricted cash, end of period	2	0.9
Combined Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	13.5	1.4
Net cash provided by (used in) investing activities
Purchase of property, plant and equipment	(0.3)	(3.2)
Proceeds from sale of joint venture	0.1
Intercompany transactions	(0.1)	0.1
Net cash provided by (used in) investing activities	(0.3)	(3.1)
Net cash provided by (used in) financing activities
Repayments on term loan	0
Borrowings under revolving credit facilities	45	0
Repayments under revolving credit facilities	0	0
Debt issuance costs		0
Intercompany transactions	(31.8)	(14.9)
Net cash provided by (used in) financing activities	13.2	(14.9)
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	26.4	(16.6)
Cash, cash equivalents and restricted cash, beginning of period	38.5	38.8
Cash, cash equivalents and restricted cash, end of period	$ 64.9	$ 22.2

Uncategorized Items - a20200331

Label	Element	Value	[1]
AOCI Attributable to Parent [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (1,300,000)
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 1,300,000
[1]	ASU 2018-02. See Note 7. Income Taxes for further information regarding our adoption of ASU 2018-02.