Century Aluminum (CENX) 10-Q 4 May 18 2018 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 25, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	CENTURY ALUMINUM CO
Entity Central Index Key	949,157
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Amendment Flag	false
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		87,575,869

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
NET SALES:
Related parties	$ 296.2	$ 280.6
Other customers	158.3	85.2
Total net sales	454.5	365.8
Cost of goods sold	440	348.9
Gross profit	14.5	16.9
Selling, general and administrative expenses	10.7	10.7
Other operating expense, net	0.3	1
Operating income	3.5	5.2
Interest expense	(5.5)	(5.6)
Interest income	0.5	0.2
Net gain (loss) on forward and derivative contracts	0.7	(16.1)
Other income (expense) - net	(1.1)	0.4
Loss before income taxes and equity in earnings of joint ventures	(1.9)	(15.9)
Income tax benefit	1	0.3
Loss before equity in earnings of joint ventures	(0.9)	(15.6)
Equity in earnings of joint ventures	0.6	0.5
Net loss	(0.3)	(15.1)
Net loss allocated to common stockholders	$ (0.3)	$ (15.1)
LOSS PER COMMON SHARE:
Basic and diluted (in USD per share)	$ 0	$ (0.17)
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING:
Basic and diluted (shares)	87.6	87.3

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Comprehensive income (loss):
Net loss	$ (0.3)	$ (15.1)
Other comprehensive loss before income tax effect:
Net loss on foreign currency cash flow hedges reclassified as income	0	0
Defined benefit plans and other postretirement benefits:
Amortization of prior service benefit during the period	(1.8)	(0.3)
Amortization of net loss during the period	2.6	2.1
Other comprehensive income before income tax effect	0.8	1.8
Income tax effect	(0.4)	(1.1)
Other comprehensive income	0.4	0.7
Total comprehensive income (loss)	$ 0.1	$ (14.4)

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
ASSETS
Cash and cash equivalents	$ 130.8	$ 167.2
Restricted cash	0.8	0.8
Accounts receivable - net	83.4	43.1
Due from affiliates	8.7	10.4
Inventories	330.7	317.5
Prepaid and other current assets	14.2	14.7
Total current assets	568.6	553.7
Property, plant and equipment - net	955.1	971.9
Other assets	57.1	56
TOTAL	1,580.8	1,581.6
LIABILITIES:
Accounts payable, trade	95.8	89.9
Due to affiliates	14.6	20.4
Accrued and other current liabilities	68	61.4
Accrued employee benefits costs	11	11
Industrial revenue bonds	7.8	7.8
Total current liabilities	197.2	190.5
Senior notes payable	248.3	248.2
Accrued pension benefits costs - less current portion	37.4	38.9
Accrued postretirement benefits costs - less current portion	112.5	113
Other liabilities	54.5	57.9
Deferred taxes	100.5	103.5
Total noncurrent liabilities	553.2	561.5
COMMITMENTS AND CONTINGENCIES
SHAREHOLDERS’ EQUITY:
Preferred stock	0	0
Common stock	0.9	0.9
Additional paid-in capital	2,518.1	2,517.4
Treasury stock, at cost	(86.3)	(86.3)
Accumulated other comprehensive loss	(91.3)	(91.7)
Accumulated deficit	(1,511)	(1,510.7)
Total shareholders’ equity	830.4	829.6
TOTAL	$ 1,580.8	$ 1,581.6

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (0.3)	$ (15.1)
Adjustments to reconcile net loss to net cash used in operating activities:
Unrealized (gain) loss on forward and derivative contracts	(0.4)	14
Lower of cost or NRV inventory adjustment	(3.2)	(3.9)
Depreciation and amortization	21.5	20.9
Other non-cash items - net	(4.6)	1.2
Change in operating assets and liabilities:
Accounts receivable - net	(40.3)	(23.8)
Due from affiliates	1.7	4.9
Inventories	(10)	(4.7)
Prepaid and other current assets	0.8	4.7
Accounts payable, trade	5.4	(4.4)
Due to affiliates	(6)	3.3
Accrued and other current liabilities	6.2	(4.9)
Other - net	(3.8)	(3.5)
Net cash used in operating activities	(33)	(11.3)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property, plant and equipment	(3.5)	(9)
Proceeds from sale of Ravenswood	0	13.5
Net cash provided by (used in) investing activities	(3.5)	4.5
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings under revolving credit facilities	0.3	0.2
Repayments under revolving credit facilities	(0.3)	(0.2)
Issuance of common stock	0.1	0
Net cash provided by financing activities	0.1	0
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(36.4)	(6.8)
Cash, cash equivalents and restricted cash, beginning of period	168	133.5
Cash, cash equivalents and restricted cash, end of period	131.6	126.7
Supplemental Cash Flow Information:
Cash paid for interest	0.2	0.2
Cash paid for taxes	$ 0.5	$ 3

General

General	3 Months Ended
	Mar. 31, 2018
General [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, 2017 . 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 2018 are not necessarily indicative of the results that may be expected for the year ending December 31, 2018 . 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. The Company adopted Accounting Standards Update 2016-18 "Statement of Cash Flows (Topic 230) Restricted Cash" as of January 1, 2018 on a retrospective basis. The adoption of this standard did not have a material impact on the Company's consolidated financial statements.

Related party transactions

Related party transactions	3 Months Ended
	Mar. 31, 2018
Related Party Transactions [Abstract]
Related party transactions	Related party transactions The significant related party transactions occurring during the three months ended March 31, 2018 and 2017 are described below. We believe all of our transactions with Glencore and BHH were at prices that approximate market. Glencore ownership As of March 31, 2018 , Glencore plc and its affiliates (together "Glencore") beneficially owned 42.9% of Century’s outstanding common stock ( 47.4% 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, and certain forward financial contracts. Sales to Glencore For the three months ended March 31, 2018 and 2017 we derived approximately 65% and 77% , respectively, of our consolidated sales from Glencore. Glencore purchases the aluminum we produce for resale. We have entered into agreements with Glencore pursuant to which Glencore has agreed to purchase aluminum produced from our U.S. and Icelandic operations through 2018 and 2019, respectively. Glencore purchases aluminum produced at our North American smelters at prices based on the London Metal Exchange (the "LME") plus the Midwest regional delivery premium and any product premiums. Glencore purchases aluminum produced at our Grundartangi, Iceland smelter at prices based on the LME plus the European Duty Paid premium and any product premiums. Purchases from Glencore We purchase a portion of our alumina requirements from Glencore. Alumina purchases from Glencore during the three months ended March 31, 2018 were priced based on a published alumina index. Financial contracts with Glencore We have certain financial contracts with Glencore. See Note 13. Derivatives regarding these forward financial sales contracts. Transactions with Baise Haohai Carbon Co., Ltd. ("BHH") We own a 40% stake in BHH and purchase carbon anodes from them for use in our aluminum production operations. Summary A summary of the aforementioned significant related party transactions is as follows: Three months ended March 31, 2018 2017 Net sales to Glencore $ 296.2 $ 280.6 Purchases from Glencore 48.4 71.6 Purchases from BHH 7.4 2.8

Revenue

Revenue	3 Months Ended
	Mar. 31, 2018
Revenue Recognition and Deferred Revenue [Abstract]
Revenue	Revenue On January 1, 2018, we adopted ASC 606, “Revenue from Contracts with Customers” and the related amendments (“ASC 606”) to contracts not completed as of the adoption date using the modified retrospective method. Accordingly, the comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. The cumulative effect of initially applying this standard was zero . The adoption of ASC 606 did not result in a change to the amount or timing of our revenue recognition. We disaggregate our revenue by geographical region as follows: Net Sales For the quarter ended March 31, 2018 United States $ 268.2 Iceland 186.3 Total $ 454.5 We enter into contracts to sell primary aluminum to Glencore and other customers. Revenue is recognized when our contractual obligations with our customer are satisfied. Our obligations under the contracts are satisfied when we transfer control of our primary aluminum to our customer which is generally upon shipment or delivery to customer-directed locations. The amount of consideration we receive, thus the revenue we recognize, is a function of volume delivered, market price of primary aluminum, as determined on the LME, plus regional delivery premiums and any value-added product premiums. The payment terms and conditions in our contracts vary and are not significant to our revenue. We complete an appropriate credit evaluation for each customer at contract inception. Customer payments are due in arrears and are recognized as accounts receivable - net and due from affiliates in our consolidated balance sheets. Accounts receivable - net increased by $40.3 million during the three month period ended March 31, 2018 driven by the increase in direct sales to end users with longer payment terms than our related party customer. When the customer-directed location is our plant site, revenue is recognized only when the customer has specifically requested delivery to such location and control over the goods transfers upon delivery to such location. The goods must be complete, ready for physical transfer, separated from other inventory and we retain no further obligations.

Fair value measurements

Fair value measurements	3 Months Ended
	Mar. 31, 2018
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 - unobservable inputs for the asset or liability. Recurring Fair Value Measurements As of March 31, 2018 Level 1 Level 2 Level 3 Total ASSETS: Cash equivalents $ 80.0 $ — $ — $ 80.0 Trust assets (1) 1.3 — — 1.3 Surety bonds 1.6 — — 1.6 Derivative instruments — — 2.0 2.0 TOTAL $ 82.9 $ — $ 2.0 $ 84.9 LIABILITIES: Contingent obligation - net $ — $ — $ — $ — Derivative instruments — — 1.1 1.1 TOTAL $ — $ — $ 1.1 $ 1.1 Recurring Fair Value Measurements As of December 31, 2017 Level 1 Level 2 Level 3 Total ASSETS: Cash equivalents $ 142.8 $ — $ — $ 142.8 Trust assets (1) 1.8 — — 1.8 Surety bonds 1.6 — — 1.6 Derivative instruments — — 1.7 1.7 TOTAL $ 146.2 $ — $ 1.7 $ 147.9 LIABILITIES: Contingent obligation – net $ — $ — $ — $ — Derivative instruments — — 1.2 1.2 TOTAL $ — $ — $ 1.2 $ 1.2 (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. The following section describes the valuation techniques and inputs used for fair value measurements categorized within Level 2 or Level 3 of the fair value hierarchy: Level 2 and Level 3 Fair Value Measurements: Asset / Liability Level Valuation Techniques Inputs Fixed for floating swaps 3 Discounted cash flows Quoted LME forward market, management's estimates of future U.S. Midwest premium Power price swap 3 Discounted cash flows Quoted Nordpool forward market, discount rate Contingent obligation 3 Discounted cash flows Quoted LME forward market, management’s estimates of the LME forward market prices for periods beyond the quoted periods. management’s estimate of future level of operations and discount rate There were no transfers between Level 1 and 2 during the periods presented. There were no transfers into or out of Level 3 during the periods presented. It is our policy to recognize transfers into and transfers out of Level 3 as of the date of the event or change in circumstances that caused the transfer.

Earnings (loss) per share

Earnings (loss) per share	3 Months Ended
	Mar. 31, 2018
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 dilutive securities. The following table shows the basic and diluted earnings (loss) per share: For the three months ended March 31, 2018 2017 Loss Shares (in millions) Per Share Loss Shares (in millions) Per Share Net loss $ (0.3 ) $ (15.1 ) Amount allocated to common stockholders 100.00 % 100.00 % Basic EPS: Net loss allocated to common stockholders $ (0.3 ) 87.6 $0.00 $ (15.1 ) 87.3 $ (0.17 ) Effect of Dilutive Securities: Share-based compensation — — — — Diluted EPS: Net loss allocated to common stockholders with assumed conversion $ (0.3 ) 87.6 $0.00 $ (15.1 ) 87.3 $ (0.17 ) Three months ended March 31, Securities excluded from the calculation of diluted EPS (in millions): 2018 2017 Share-based compensation (1) 1.4 1.2 (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 antidilutive effect on earnings (loss) per share.

Shareholders' equity

Shareholders' equity	3 Months Ended
	Mar. 31, 2018
Stockholders' Equity Note [Abstract]
Shareholders' equity	Shareholders’ equity Common Stock As of March 31, 2018 and December 31, 2017 , we had 195,000,000 shares of common stock, $0.01 cent par value per share, authorized under our Restated Certificate of Incorporation, of which 94,762,390 shares were issued and 87,575,869 shares were outstanding at March 31, 2018 ; 94,731,298 shares were issued and 87,544,777 shares were outstanding at December 31, 2017 . 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 At March 31, 2018 and December 31, 2017 we had 5,000,000 shares of preferred stock, $0.01 cent 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. At March 31, 2018 and December 31, 2017 , 74,231 and 74,364 shares of Series A Convertible Preferred Stock were outstanding, respectively, and held by Glencore. 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 of preferred to common shares is 100 shares of common for each share of preferred stock. Our Series A Convertible Preferred Stock has a par value of $0.01 per share. The Common and Preferred Stock table below contains additional information about preferred stock conversions during the three months ended March 31, 2018 and 2017 . Preferred stock Common stock Common and Preferred Stock Activity (in shares): Series A convertible Treasury Outstanding Beginning balance as of December 31, 2017 74,364 7,186,521 87,544,777 Conversion of convertible preferred stock (133 ) — 13,343 Issuance for share-based compensation plans — — 17,749 Ending balance as of March 31, 2018 74,231 7,186,521 87,575,869 Beginning balance as of December 31, 2016 75,625 7,186,521 87,250,897 Conversion of convertible preferred stock (48 ) — 4,795 Issuance for share-based compensation plans — — 6,423 Ending balance as of March 31, 2017 75,577 7,186,521 87,262,115 Stock Repurchase Program 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 the cost. The difference between the cost of the shares and the reissuance price is added to or deducted from additional paid-in capital. Through March 31, 2018 we had repurchased 7,186,521 shares of common stock for an aggregate purchase price of $86.3 million . We have made no share repurchases since April 2015 and we have $43.7 million remaining under the repurchase program authorization as of March 31, 2018 .

Income taxes

Income taxes	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income taxes	Income taxes We recorded an income tax benefit of $1.0 million for the three months ended March 31, 2018 and an income tax benefit of $0.3 million for the three months ended March 31, 2017 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 pretax accounting income/loss. As of March 31, 2018 , 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. We continue to assess the impact of the recently enacted Tax Cuts and Jobs Act (the “Act”) on our business and our consolidated financial statements through the measurement period allowed under Staff Accounting Bulletin ("SAB") 118. Adjustments to provisional amounts, if any, that are identified during the measurement period will be recorded in the reporting period in which the adjustment is determined. As of March 31, 2018, no adjustments have been recorded to the recorded provisional amounts related to the Act. On April 2, 2018, the Internal Revenue Service issued Notice 2018-26 which provides guidance on how to determine, report and pay the repatriation tax on deemed repatriated earnings of foreign subsidiaries provided in the Tax Reform Act and included in the consolidated financial statements for the year ended December 31, 2017. Notice 2018-26 is not expected to have a significant impact on the Company's consolidated financial statements.

Inventories

Inventories	3 Months Ended
	Mar. 31, 2018
Inventory, Net [Abstract]
Inventories	Inventories Inventories consist of the following: March 31, 2018 December 31, 2017 Raw materials $ 108.1 $ 106.2 Work-in-process 54.3 49.6 Finished goods 41.7 40.9 Operating and other supplies 126.6 120.8 Total inventories $ 330.7 $ 317.5 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, 2018
Debt Disclosure [Abstract]
Debt	Debt March 31, 2018 December 31, 2017 Debt classified as current liabilities: Hancock County industrial revenue bonds ("IRBs") due April 1, 2028, interest payable quarterly (variable interest rates (not to exceed 12%)) (1) $ 7.8 $ 7.8 Debt classified as non-current liabilities: 7.5% senior secured notes due June 1, 2021, net of debt discount of $1.7 million and $1.8 million, respectively, interest payable semiannually 248.3 248.2 Total $ 256.1 $ 256.0 (1) 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, 2018 was 1.78% . 7.5% Notes due 2021 General. On June 4, 2013, we issued $250.0 million of our 7.5% Notes due June 1, 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 bear interest at the 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. Fair Value. Fair value for our 2021 Notes was based on the latest trading data available and was $255.3 million and $258.3 million , as of March 31, 2018 and December 31, 2017 , 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. U.S. Revolving Credit Facility We and certain of our direct and indirect domestic subsidiaries are party to a senior secured revolving credit facility, dated May 24, 2013, as amended, with a syndicate of lenders which provides for borrowings of up to $150.0 million in the aggregate, including up to $110.0 million under a letter of credit sub-facility (the "U.S. revolving credit facility"). Our U.S. revolving credit facility matures in June 26, 2020. Any letters of credit issued and outstanding under the U.S. revolving credit facility reduce our borrowing availability on a dollar-for-dollar basis. The availability of funds under the U.S. revolving credit facility is limited by a specified borrowing base consisting of accounts receivable, inventory and qualified cash deposits of the borrowers which meet the eligibility criteria. Status of our U.S. revolving credit facility: March 31, 2018 Credit facility maximum amount $ 150.0 Borrowing availability 150.0 Outstanding letters of credit issued 39.1 Outstanding borrowings — Borrowing availability, net of outstanding letters of credit and borrowings 110.9 Iceland Revolving Credit Facility We have also entered into, through our wholly-owned subsidiary Nordural Grundartangi ehf, a $50.0 million revolving credit facility, dated November 27, 2013, as amended (the "Iceland revolving credit facility"). The Iceland revolving credit facility expires on November 27, 2020. The availability of funds under the Iceland revolving credit facility is limited by a specified borrowing base consisting of inventory and accounts receivable of Grundartangi. Status of our Iceland revolving credit facility: March 31, 2018 Credit facility maximum amount $ 50.0 Borrowing availability 50.0 Outstanding borrowings — Borrowing availability, net of borrowings 50.0

Commitments and contingencies

Commitments and contingencies	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and contingencies	Commitments and contingencies Environmental Contingencies Based upon all available information, we believe our current environmental liabilities do not have, and are not likely to have, a material adverse effect on our financial condition, results of operations or liquidity. However, because of the inherent uncertainties in estimating environmental liabilities primarily due to unknown facts and circumstances and changing governmental regulations and legal standards regarding liability, there can be no assurance that future capital expenditures and costs for environmental compliance at currently or formerly owned or operated properties will not result in liabilities that may have a material adverse effect on our financial condition, results of operations or liquidity. It is our policy to accrue for costs associated with environmental assessments and remedial efforts when it becomes probable that a liability has been incurred and the costs can be reasonably estimated. All accrued amounts have been recorded without giving effect to any possible future recoveries. Costs for ongoing environmental compliance, including maintenance and monitoring are expensed as incurred. 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 court ordered the stay lifted and reopened the case. The matter is in a preliminary stage in the U.S. District Court for the District of Delaware, and we cannot predict the ultimate outcome of this action or estimate a range of possible losses related to this matter at this time. 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. Through March 31, 2018 , our affiliate, Virgin Islands Alumina Corporation LLC, has expended approximately $1.1 million on the Hydrocarbon Recovery Plan. 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 possible losses for any of the foregoing actions relating to the St. Croix Alumina Refinery. Legal Contingencies In addition to the foregoing matters, we have pending against us or may be subject to various lawsuits, claims and proceedings related primarily to employment, commercial, stockholder, safety and health matters. While the results of such litigation matters and claims cannot be predicted with certainty, we believe that the final outcome of such matters 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, should the 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 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. When we have assessed that a loss associated with legal contingencies is reasonably possible, we determine if estimates of possible losses or ranges of possible losses are in excess of related accrued liabilities, if any. Based on current knowledge, management has ascertained estimates for losses that are reasonably possible and management does not believe that any reasonably possible outcomes in excess of our accruals, if any, either individually or in aggregate, would be material to our financial condition, results of operations or liquidity. We reevaluate and update our assessments and accruals as matters progress over time. Ravenswood Retiree Medical Benefits changes 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 agreed to pay the remaining amounts under the settlement agreement in annual increments of $2.0 million for nine years. At March 31, 2018 , we had $2.0 million in other current liabilities and $11.1 million in other liabilities related to this agreement. 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, 2018 and 2017. 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 . 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 2019, extending year to year thereafter 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 2019, extending year to year thereafter 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, 2018. The agreement with the other power supplier has a term through December 31, 2018. Both of these agreements 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 LME-based variable rates through October 2019 and at rates linked to the Nord Pool power market from November 2019 through the expiration of the agreement on December 31, 2023. 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 agreements. The first stage 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. We are in discussions with OR with respect to such conditions and other matters pertaining to this agreement. Other Commitments and Contingencies Labor Commitments The bargaining unit employees at our Grundartangi, Vlissingen, Hawesville and Sebree facilities are represented by labor unions, representing 63% of our total workforce. Approximately 85% of Grundartangi’s work force is represented by five labor unions, governed by a labor agreement which is effective through December 31, 2019 that establishes wages and work rules for covered employees. 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 to June 1, 2018. The FME negotiates working conditions with trade unions on behalf of its members. Approximately 51% of our U.S. based work force is represented by the USW. The labor agreement for Hawesville employees is effective through April 1, 2020. Century Sebree's labor agreement with the USW for its employees is effective through October 28, 2019. 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, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Components of accumulated other comprehensive loss	Components of accumulated other comprehensive loss March 31, 2018 December 31, 2017 Defined benefit plan liabilities $ (101.2 ) $ (102.1 ) Unrealized loss on financial instruments 2.6 2.7 Other comprehensive loss before income tax effect (98.6 ) (99.4 ) Income tax effect (1) 7.3 7.7 Accumulated other comprehensive loss $ (91.3 ) $ (91.7 ) (1) The allocation of the income tax effect to the components of other comprehensive loss is as follows: March 31, 2018 December 31, 2017 Defined benefit plan liabilities $ 7.8 $ 8.2 Unrealized loss on financial instruments (0.5 ) (0.5 ) The following table summarizes the changes in the accumulated balances for each component of accumulated other comprehensive loss ("AOCL"): Defined benefit plan and other postretirement liabilities Unrealized gain (loss) on financial instruments Total, net of tax Balance, January 1, 2018 $ (93.8 ) $ 2.1 $ (91.7 ) Net amount reclassified to net loss 0.4 0.0 0.4 Balance, March 31, 2018 $ (93.4 ) $ 2.1 $ (91.3 ) Balance, January 1, 2017 $ (116.2 ) $ 2.3 $ (113.9 ) Net amount reclassified to net loss 0.7 0.0 0.7 Balance, March 31, 2017 $ (115.5 ) $ 2.3 $ (113.2 ) Reclassifications out of AOCL were included in the consolidated statements of operations as follows: For the three months ended March 31, AOCL Components Location 2018 2017 Defined benefit plan and other postretirement liabilities Cost of goods sold $ 0.7 $ 1.3 Selling, general and administrative expenses (0.4 ) 0.1 Other operating expense, net 0.5 0.4 Income tax effect (0.4 ) (1.1 ) Net of tax $ 0.4 $ 0.7 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, 2018
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, 2018 2017 Service cost $ 1.1 $ 1.2 Interest cost 3.1 3.3 Expected return on plan assets (5.3 ) (4.7 ) Amortization of prior service costs 0.0 0.0 Amortization of net loss 1.5 1.2 Net periodic benefit cost $ 0.4 $ 1.0 Other Postretirement Benefits ("OPEB") Three months ended March 31, 2018 2017 Service cost $ 0.1 $ 0.2 Interest cost 1.1 1.4 Amortization of prior service cost (1.8 ) (0.3 ) Amortization of net loss 1.1 0.9 Net periodic benefit cost $ 0.5 $ 2.2

Derivatives

Derivatives	3 Months Ended
	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives	Derivatives As of March 31, 2018 , we had an open position of 3,090 tonnes related to LME forward financial sales contracts, all of which are with Glencore, to fix the forward LME price (the “forward financial sales contracts”). These forward financial sales contracts are expected to settle monthly, on a ratable basis, between November 1, 2019 and December 31, 2020. We also have financial contracts with various counterparties, including Glencore, to offset fixed price sales arrangements with certain of our customers (the “fixed for floating swaps”) to remain exposed to the LME price. As of March 31, 2018 , we had open positions related to such arrangements of 11,337 tonnes settling at various dates through June 2019. In 2017, we entered into financial contracts to fix the forward price of approximately 4% of Grundartangi's total power requirements for the period November 1, 2019 through December 31, 2020 (the “power price swaps”). The power price swaps are not designated as cash flow hedges. As of March 31, 2018 , we had an open position of 256,200 MWh related to the power price swaps. As of March 31, 2018 , we had a derivative asset and liability of $2.0 million and $1.1 million , respectively, in the consolidated balance sheets. We recognized gains of $0.7 million related to our derivative instruments during the three months ended March 31, 2018 in the consolidated statements of operations, a portion of which related to transactions with Glencore. At December 31, 2017 , we had a derivative asset and liability of $1.7 million and $1.2 million , respectively, in the consolidated balance sheets. We recognized losses of $16.1 million related to our derivative instruments during the three months ended March 31, 2017 , in the consolidated statements of operations, substantially all of which related to transactions with Glencore.

Condensed consolidating financi

Condensed consolidating financial information	3 Months Ended
	Mar. 31, 2018
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed consolidating financial information	Condensed consolidating financial information Our 2021 Notes are guaranteed by each of our material existing and future domestic subsidiaries (The "Guarantor 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 are full and unconditional; all guarantees are joint and several. These notes are not guaranteed by our foreign subsidiaries (such foreign subsidiaries, Nordural US LLC, Century Aluminum Development LLC and Century Aluminum of West Virginia, Inc., collectively 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, 2018 and 2017 , condensed consolidating balance sheets as of March 31, 2018 and December 31, 2017 and the condensed consolidating statements of cash flows for the three months ended March 31, 2018 and 2017 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, 2018 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated NET SALES: Related parties $ — $ 110.7 $ 185.5 $ — $ 296.2 Other customers — 157.5 0.8 — 158.3 Total net sales — 268.2 186.3 — 454.5 Cost of goods sold — 261.2 178.8 — 440.0 Gross profit — 7.0 7.5 — 14.5 Selling, general and administrative expenses 10.0 — 0.7 — 10.7 Other operating expense - net — — 0.3 — 0.3 Operating income (loss) (10.0 ) 7.0 6.5 — 3.5 Interest expense (5.1 ) (0.4 ) — — (5.5 ) Intercompany interest 9.0 2.3 (11.3 ) — — Interest income 0.2 — 0.3 — 0.5 Net gain (loss) on forward and derivative contracts — 0.3 0.4 — 0.7 Other income (expense) - net 0.5 — (1.6 ) — (1.1 ) Income (loss) before income taxes and equity in earnings of joint ventures (5.4 ) 9.2 (5.7 ) — (1.9 ) Income tax (expense) benefit (0.1 ) — 1.1 — 1.0 Income (loss) before equity in earnings of joint ventures (5.5 ) 9.2 (4.6 ) — (0.9 ) Equity in earnings (loss) of joint ventures 5.2 (0.3 ) 0.6 (4.9 ) 0.6 Net income (loss) $ (0.3 ) $ 8.9 $ (4.0 ) $ (4.9 ) $ (0.3 ) Other comprehensive income (loss) before income tax effect 0.8 0.7 0.4 (1.1 ) 0.8 Income tax effect (0.4 ) — — — (0.4 ) Other comprehensive income (loss) 0.4 0.7 0.4 (1.1 ) 0.4 Total comprehensive income (loss) $ 0.1 $ 9.6 $ (3.6 ) $ (6.0 ) $ 0.1 Condensed Consolidating Statements of Comprehensive Income (Loss) For the three months ended March 31, 2017 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated NET SALES: Related parties $ — $ 131.1 $ 149.5 $ — $ 280.6 Other customers — 85.2 — — 85.2 Total net sales — 216.3 149.5 — 365.8 Cost of goods sold — 213.8 135.1 — 348.9 Gross profit — 2.5 14.4 — 16.9 Selling, general and administrative expenses 10.2 — 0.5 — 10.7 Other operating expense - net — — 1.0 — 1.0 Operating income (loss) (10.2 ) 2.5 12.9 — 5.2 Interest expense (5.2 ) (0.4 ) — — (5.6 ) Intercompany interest 9.0 2.1 (11.1 ) — — Interest income 0.1 — 0.1 — 0.2 Net gain (loss) on forward and derivative contracts — (15.8 ) (0.3 ) — (16.1 ) Other income (expense) - net 0.8 — (0.4 ) — 0.4 Income (loss) before income taxes and equity in earnings of joint ventures (5.5 ) (11.6 ) 1.2 — (15.9 ) Income tax (expense) benefit 0.6 0.5 (0.8 ) — 0.3 Income (loss) before equity in earnings of joint ventures (4.9 ) (11.1 ) 0.4 — (15.6 ) Equity in earnings (loss) of joint ventures (10.2 ) 0.8 0.5 9.4 0.5 Net income (loss) $ (15.1 ) $ (10.3 ) $ 0.9 $ 9.4 $ (15.1 ) Other comprehensive income (loss) before income tax effect 1.8 1.3 0.4 (1.7 ) 1.8 Income tax effect (1.1 ) — — — (1.1 ) Other comprehensive income (loss) 0.7 1.3 0.4 (1.7 ) 0.7 Total comprehensive income (loss) $ (14.4 ) $ (9.0 ) $ 1.3 $ 7.7 $ (14.4 ) Condensed Consolidating Balance Sheet As of March 31, 2018 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated Cash & cash equivalents $ 8.5 $ (0.1 ) $ 122.4 $ — $ 130.8 Restricted cash — 0.8 — — 0.8 Accounts receivable - net — 83.2 0.2 — 83.4 Due from affiliates — 7.9 0.8 — 8.7 Inventories 0.2 216.8 113.7 — 330.7 Prepaid and other current assets 3.4 0.5 10.3 — 14.2 Total current assets 12.1 309.1 247.4 — 568.6 Property, plant and equipment - net 20.6 286.9 647.6 — 955.1 Investment in subsidiaries 758.2 53.6 — (811.8 ) — Due from affiliates - long term 546.1 339.6 9.4 (895.1 ) — Other assets 28.3 34.3 26.7 (32.2 ) 57.1 TOTAL $ 1,365.3 $ 1,023.5 $ 931.1 $ (1,739.1 ) $ 1,580.8 Accounts payable, trade $ 1.8 $ 55.3 $ 38.7 $ — $ 95.8 Due to affiliates 0.7 (0.5 ) 14.4 — 14.6 Accrued and other current liabilities 20.2 16.6 31.2 — 68.0 Accrued employee benefits costs 1.9 8.3 0.8 — 11.0 Industrial revenue bonds — 7.8 — — 7.8 Total current liabilities 24.6 87.5 85.1 — 197.2 Senior notes payable 248.3 — — — 248.3 Accrued pension benefits costs - less current portion 39.2 17.9 12.5 (32.2 ) 37.4 Accrued postretirement benefits costs - less current portion 0.8 110.0 1.7 — 112.5 Due to affiliates - long term 218.0 81.1 596.0 (895.1 ) — Other liabilities 4.0 28.1 22.4 — 54.5 Deferred taxes — 1.7 98.8 — 100.5 Total noncurrent liabilities 510.3 238.8 731.4 (927.3 ) 553.2 Preferred stock 0.0 — — — 0.0 Common stock 0.9 — 0.1 (0.1 ) 0.9 Other shareholders' equity 829.5 697.2 114.5 (811.7 ) 829.5 Total shareholders' equity 830.4 697.2 114.6 (811.8 ) 830.4 TOTAL $ 1,365.3 $ 1,023.5 $ 931.1 $ (1,739.1 ) $ 1,580.8 Condensed Consolidating Balance Sheet As of December 31, 2017 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated Cash & cash equivalents $ 64.3 $ (0.1 ) $ 103.0 $ — $ 167.2 Restricted cash — 0.8 — — 0.8 Accounts receivable - net — 42.8 0.3 — 43.1 Due from affiliates 0.1 10.3 — — 10.4 Inventories 0.2 205.1 112.2 — 317.5 Prepaid and other current assets 3.3 0.8 10.6 — 14.7 Total current assets 67.9 259.7 226.1 — 553.7 Property, plant and equipment - net 19.4 295.8 656.7 — 971.9 Investment in subsidiaries 751.8 54.0 — (805.8 ) — Due from affiliates - long term 513.3 349.6 9.4 (872.3 ) — Other assets 28.0 34.1 25.9 (32.0 ) 56.0 TOTAL $ 1,380.4 $ 993.2 $ 918.1 $ (1,710.1 ) $ 1,581.6 Accounts payable, trade $ 6.3 $ 51.4 $ 32.2 $ — $ 89.9 Due to affiliates 0.4 2.6 17.4 — 20.4 Accrued and other current liabilities 16.0 19.3 26.1 — 61.4 Accrued employee benefits costs 1.9 8.3 0.8 — 11.0 Industrial revenue bonds — 7.8 — — 7.8 Total current liabilities 24.6 89.4 76.5 — 190.5 Senior notes payable 248.2 — — — 248.2 Accrued pension benefits costs - less current portion 39.5 18.3 13.1 (32.0 ) 38.9 Accrued postretirement benefits costs - less current portion 0.9 110.4 1.7 — 113.0 Other liabilities 3.5 32.0 22.4 — 57.9 Due to affiliates - long term 234.1 53.8 584.4 (872.3 ) — Deferred taxes — 1.7 101.8 — 103.5 Total noncurrent liabilities 526.2 216.2 723.4 (904.3 ) 561.5 Preferred stock 0.0 — — — 0.0 Common stock 0.9 — 0.1 (0.1 ) 0.9 Other shareholders' equity 828.7 687.6 118.1 (805.7 ) 828.7 Total shareholders' equity 829.6 687.6 118.2 (805.8 ) 829.6 TOTAL $ 1,380.4 $ 993.2 $ 918.1 $ (1,710.1 ) $ 1,581.6 Condensed Consolidating Statement of Cash Flows For the three months ended March 31, 2018 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated Net cash provided by (used in) operating activities $ (26.8 ) $ (26.8 ) $ 20.6 $ — $ (33.0 ) Purchase of property, plant and equipment (1.5 ) (0.4 ) (1.6 ) — (3.5 ) Intercompany transactions (23.8 ) — — 23.8 — Net cash provided by (used in) investing activities (25.3 ) (0.4 ) (1.6 ) 23.8 (3.5 ) Borrowings under revolving credit facilities 0.3 — — — 0.3 Repayments under revolving credit facilities (0.3 ) — — — (0.3 ) Issuance of common stock 0.1 — — — 0.1 Intercompany transactions (3.8 ) 27.2 0.4 (23.8 ) — Net cash provided by (used in) financing activities (3.7 ) 27.2 0.4 (23.8 ) 0.1 CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH (55.8 ) — 19.4 — (36.4 ) Cash, cash equivalents and restricted cash, beginning of period 64.3 0.7 103.0 — 168.0 Cash, cash equivalents and restricted cash, end of period $ 8.5 $ 0.7 $ 122.4 $ — $ 131.6 Condensed Consolidating Statement of Cash Flows For the three months ended March 31, 2017 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated Net cash provided by (used in) operating activities $ (1.1 ) $ (21.8 ) $ 11.6 $ — $ (11.3 ) Purchase of property, plant and equipment (4.4 ) (2.3 ) (2.3 ) — (9.0 ) Proceeds from sale of property, plant and equipment — — 13.5 — 13.5 Intercompany transactions 19.2 23.6 (12.4 ) (30.4 ) — Net cash used in investing activities 14.8 21.3 (1.2 ) (30.4 ) 4.5 Borrowings under revolving credit facilities 0.2 — — — 0.2 Repayments under revolving credit facilities (0.2 ) — — — (0.2 ) Intercompany transactions (11.2 ) 0.8 (20.0 ) 30.4 — Net cash provided by (used in) financing activities (11.2 ) 0.8 (20.0 ) 30.4 — CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH 2.5 0.3 (9.6 ) — (6.8 ) Cash, cash equivalents and restricted cash, beginning of period 36.7 0.5 96.3 — 133.5 Cash, cash equivalents and restricted cash, end of period $ 39.2 $ 0.8 $ 86.7 $ — $ 126.7

Fair value measurements (Polici

Fair value measurements (Policies)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair value transfer	It is our policy to recognize transfers into and transfers out of Level 3 as of the date of the event or change in circumstances that caused the transfer.

Related party transactions (Tab

Related party transactions (Tables)	3 Months Ended
	Mar. 31, 2018
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, 2018 2017 Net sales to Glencore $ 296.2 $ 280.6 Purchases from Glencore 48.4 71.6 Purchases from BHH 7.4 2.8

Revenue (Tables)

Revenue (Tables)	3 Months Ended
	Mar. 31, 2018
Revenue Recognition and Deferred Revenue [Abstract]
Disaggregation of revenue	We disaggregate our revenue by geographical region as follows: Net Sales For the quarter ended March 31, 2018 United States $ 268.2 Iceland 186.3 Total $ 454.5

Fair value measurements (Tables

Fair value measurements (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Financial assets and liabilities at fair value on a recurring basis	Recurring Fair Value Measurements As of March 31, 2018 Level 1 Level 2 Level 3 Total ASSETS: Cash equivalents $ 80.0 $ — $ — $ 80.0 Trust assets (1) 1.3 — — 1.3 Surety bonds 1.6 — — 1.6 Derivative instruments — — 2.0 2.0 TOTAL $ 82.9 $ — $ 2.0 $ 84.9 LIABILITIES: Contingent obligation - net $ — $ — $ — $ — Derivative instruments — — 1.1 1.1 TOTAL $ — $ — $ 1.1 $ 1.1 Recurring Fair Value Measurements As of December 31, 2017 Level 1 Level 2 Level 3 Total ASSETS: Cash equivalents $ 142.8 $ — $ — $ 142.8 Trust assets (1) 1.8 — — 1.8 Surety bonds 1.6 — — 1.6 Derivative instruments — — 1.7 1.7 TOTAL $ 146.2 $ — $ 1.7 $ 147.9 LIABILITIES: Contingent obligation – net $ — $ — $ — $ — Derivative instruments — — 1.2 1.2 TOTAL $ — $ — $ 1.2 $ 1.2 (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.
Schedule of valuation methodology for assets and liabilities at fair value	The following section describes the valuation techniques and inputs used for fair value measurements categorized within Level 2 or Level 3 of the fair value hierarchy: Level 2 and Level 3 Fair Value Measurements: Asset / Liability Level Valuation Techniques Inputs Fixed for floating swaps 3 Discounted cash flows Quoted LME forward market, management's estimates of future U.S. Midwest premium Power price swap 3 Discounted cash flows Quoted Nordpool forward market, discount rate Contingent obligation 3 Discounted cash flows Quoted LME forward market, management’s estimates of the LME forward market prices for periods beyond the quoted periods. management’s estimate of future level of operations and discount rate

Earnings (loss) per share (Tabl

Earnings (loss) per share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Basic and diluted earnings (loss) per share	The following table shows the basic and diluted earnings (loss) per share: For the three months ended March 31, 2018 2017 Loss Shares (in millions) Per Share Loss Shares (in millions) Per Share Net loss $ (0.3 ) $ (15.1 ) Amount allocated to common stockholders 100.00 % 100.00 % Basic EPS: Net loss allocated to common stockholders $ (0.3 ) 87.6 $0.00 $ (15.1 ) 87.3 $ (0.17 ) Effect of Dilutive Securities: Share-based compensation — — — — Diluted EPS: Net loss allocated to common stockholders with assumed conversion $ (0.3 ) 87.6 $0.00 $ (15.1 ) 87.3 $ (0.17 )
Securities excluded from the calculation of diluted EPS	Three months ended March 31, Securities excluded from the calculation of diluted EPS (in millions): 2018 2017 Share-based compensation (1) 1.4 1.2 (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 antidilutive effect on earnings (loss) per share.

Shareholders' equity (Tables)

Shareholders' equity (Tables)	3 Months Ended
	Mar. 31, 2018
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, 2018 and 2017 . Preferred stock Common stock Common and Preferred Stock Activity (in shares): Series A convertible Treasury Outstanding Beginning balance as of December 31, 2017 74,364 7,186,521 87,544,777 Conversion of convertible preferred stock (133 ) — 13,343 Issuance for share-based compensation plans — — 17,749 Ending balance as of March 31, 2018 74,231 7,186,521 87,575,869 Beginning balance as of December 31, 2016 75,625 7,186,521 87,250,897 Conversion of convertible preferred stock (48 ) — 4,795 Issuance for share-based compensation plans — — 6,423 Ending balance as of March 31, 2017 75,577 7,186,521 87,262,115

Inventories (Tables)

Inventories (Tables)	3 Months Ended
	Mar. 31, 2018
Inventory, Net [Abstract]
Schedule of Inventories	Inventories consist of the following: March 31, 2018 December 31, 2017 Raw materials $ 108.1 $ 106.2 Work-in-process 54.3 49.6 Finished goods 41.7 40.9 Operating and other supplies 126.6 120.8 Total inventories $ 330.7 $ 317.5

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Schedule of Debt	March 31, 2018 December 31, 2017 Debt classified as current liabilities: Hancock County industrial revenue bonds ("IRBs") due April 1, 2028, interest payable quarterly (variable interest rates (not to exceed 12%)) (1) $ 7.8 $ 7.8 Debt classified as non-current liabilities: 7.5% senior secured notes due June 1, 2021, net of debt discount of $1.7 million and $1.8 million, respectively, interest payable semiannually 248.3 248.2 Total $ 256.1 $ 256.0 (1) 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, 2018 was 1.78% .
Schedule of Line of Credit Facilities	Status of our Iceland revolving credit facility: March 31, 2018 Credit facility maximum amount $ 50.0 Borrowing availability 50.0 Outstanding borrowings — Borrowing availability, net of borrowings 50.0 Status of our U.S. revolving credit facility: March 31, 2018 Credit facility maximum amount $ 150.0 Borrowing availability 150.0 Outstanding letters of credit issued 39.1 Outstanding borrowings — Borrowing availability, net of outstanding letters of credit and borrowings 110.9

Components of accumulated oth28

Components of accumulated other comprehensive loss (Tables)	3 Months Ended
	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated balances for each component of AOCI	March 31, 2018 December 31, 2017 Defined benefit plan liabilities $ (101.2 ) $ (102.1 ) Unrealized loss on financial instruments 2.6 2.7 Other comprehensive loss before income tax effect (98.6 ) (99.4 ) Income tax effect (1) 7.3 7.7 Accumulated other comprehensive loss $ (91.3 ) $ (91.7 ) (1) The allocation of the income tax effect to the components of other comprehensive loss is as follows: March 31, 2018 December 31, 2017 Defined benefit plan liabilities $ 7.8 $ 8.2 Unrealized loss on financial instruments (0.5 ) (0.5 ) The following table summarizes the changes in the accumulated balances for each component of accumulated other comprehensive loss ("AOCL"): Defined benefit plan and other postretirement liabilities Unrealized gain (loss) on financial instruments Total, net of tax Balance, January 1, 2018 $ (93.8 ) $ 2.1 $ (91.7 ) Net amount reclassified to net loss 0.4 0.0 0.4 Balance, March 31, 2018 $ (93.4 ) $ 2.1 $ (91.3 ) Balance, January 1, 2017 $ (116.2 ) $ 2.3 $ (113.9 ) Net amount reclassified to net loss 0.7 0.0 0.7 Balance, March 31, 2017 $ (115.5 ) $ 2.3 $ (113.2 )
Reclassification out of AOCI	Reclassifications out of AOCL were included in the consolidated statements of operations as follows: For the three months ended March 31, AOCL Components Location 2018 2017 Defined benefit plan and other postretirement liabilities Cost of goods sold $ 0.7 $ 1.3 Selling, general and administrative expenses (0.4 ) 0.1 Other operating expense, net 0.5 0.4 Income tax effect (0.4 ) (1.1 ) Net of tax $ 0.4 $ 0.7 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 be29

Components of net periodic benefit cost (Tables)	3 Months Ended
	Mar. 31, 2018
Components of net periodic benefit cost [Abstract]
Schedule of net periodic benefit cost	Pension Benefits Three months ended March 31, 2018 2017 Service cost $ 1.1 $ 1.2 Interest cost 3.1 3.3 Expected return on plan assets (5.3 ) (4.7 ) Amortization of prior service costs 0.0 0.0 Amortization of net loss 1.5 1.2 Net periodic benefit cost $ 0.4 $ 1.0 Other Postretirement Benefits ("OPEB") Three months ended March 31, 2018 2017 Service cost $ 0.1 $ 0.2 Interest cost 1.1 1.4 Amortization of prior service cost (1.8 ) (0.3 ) Amortization of net loss 1.1 0.9 Net periodic benefit cost $ 0.5 $ 2.2

Condensed consolidating finan30

Condensed consolidating financial information (Tables)	3 Months Ended
	Mar. 31, 2018
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed Consolidating Statements of Comprehensive Income (Loss)	Condensed Consolidating Statements of Comprehensive Income (Loss) For the three months ended March 31, 2018 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated NET SALES: Related parties $ — $ 110.7 $ 185.5 $ — $ 296.2 Other customers — 157.5 0.8 — 158.3 Total net sales — 268.2 186.3 — 454.5 Cost of goods sold — 261.2 178.8 — 440.0 Gross profit — 7.0 7.5 — 14.5 Selling, general and administrative expenses 10.0 — 0.7 — 10.7 Other operating expense - net — — 0.3 — 0.3 Operating income (loss) (10.0 ) 7.0 6.5 — 3.5 Interest expense (5.1 ) (0.4 ) — — (5.5 ) Intercompany interest 9.0 2.3 (11.3 ) — — Interest income 0.2 — 0.3 — 0.5 Net gain (loss) on forward and derivative contracts — 0.3 0.4 — 0.7 Other income (expense) - net 0.5 — (1.6 ) — (1.1 ) Income (loss) before income taxes and equity in earnings of joint ventures (5.4 ) 9.2 (5.7 ) — (1.9 ) Income tax (expense) benefit (0.1 ) — 1.1 — 1.0 Income (loss) before equity in earnings of joint ventures (5.5 ) 9.2 (4.6 ) — (0.9 ) Equity in earnings (loss) of joint ventures 5.2 (0.3 ) 0.6 (4.9 ) 0.6 Net income (loss) $ (0.3 ) $ 8.9 $ (4.0 ) $ (4.9 ) $ (0.3 ) Other comprehensive income (loss) before income tax effect 0.8 0.7 0.4 (1.1 ) 0.8 Income tax effect (0.4 ) — — — (0.4 ) Other comprehensive income (loss) 0.4 0.7 0.4 (1.1 ) 0.4 Total comprehensive income (loss) $ 0.1 $ 9.6 $ (3.6 ) $ (6.0 ) $ 0.1 Condensed Consolidating Statements of Comprehensive Income (Loss) For the three months ended March 31, 2017 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated NET SALES: Related parties $ — $ 131.1 $ 149.5 $ — $ 280.6 Other customers — 85.2 — — 85.2 Total net sales — 216.3 149.5 — 365.8 Cost of goods sold — 213.8 135.1 — 348.9 Gross profit — 2.5 14.4 — 16.9 Selling, general and administrative expenses 10.2 — 0.5 — 10.7 Other operating expense - net — — 1.0 — 1.0 Operating income (loss) (10.2 ) 2.5 12.9 — 5.2 Interest expense (5.2 ) (0.4 ) — — (5.6 ) Intercompany interest 9.0 2.1 (11.1 ) — — Interest income 0.1 — 0.1 — 0.2 Net gain (loss) on forward and derivative contracts — (15.8 ) (0.3 ) — (16.1 ) Other income (expense) - net 0.8 — (0.4 ) — 0.4 Income (loss) before income taxes and equity in earnings of joint ventures (5.5 ) (11.6 ) 1.2 — (15.9 ) Income tax (expense) benefit 0.6 0.5 (0.8 ) — 0.3 Income (loss) before equity in earnings of joint ventures (4.9 ) (11.1 ) 0.4 — (15.6 ) Equity in earnings (loss) of joint ventures (10.2 ) 0.8 0.5 9.4 0.5 Net income (loss) $ (15.1 ) $ (10.3 ) $ 0.9 $ 9.4 $ (15.1 ) Other comprehensive income (loss) before income tax effect 1.8 1.3 0.4 (1.7 ) 1.8 Income tax effect (1.1 ) — — — (1.1 ) Other comprehensive income (loss) 0.7 1.3 0.4 (1.7 ) 0.7 Total comprehensive income (loss) $ (14.4 ) $ (9.0 ) $ 1.3 $ 7.7 $ (14.4 )
Condensed Consolidating Balance Sheet	Condensed Consolidating Balance Sheet As of March 31, 2018 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated Cash & cash equivalents $ 8.5 $ (0.1 ) $ 122.4 $ — $ 130.8 Restricted cash — 0.8 — — 0.8 Accounts receivable - net — 83.2 0.2 — 83.4 Due from affiliates — 7.9 0.8 — 8.7 Inventories 0.2 216.8 113.7 — 330.7 Prepaid and other current assets 3.4 0.5 10.3 — 14.2 Total current assets 12.1 309.1 247.4 — 568.6 Property, plant and equipment - net 20.6 286.9 647.6 — 955.1 Investment in subsidiaries 758.2 53.6 — (811.8 ) — Due from affiliates - long term 546.1 339.6 9.4 (895.1 ) — Other assets 28.3 34.3 26.7 (32.2 ) 57.1 TOTAL $ 1,365.3 $ 1,023.5 $ 931.1 $ (1,739.1 ) $ 1,580.8 Accounts payable, trade $ 1.8 $ 55.3 $ 38.7 $ — $ 95.8 Due to affiliates 0.7 (0.5 ) 14.4 — 14.6 Accrued and other current liabilities 20.2 16.6 31.2 — 68.0 Accrued employee benefits costs 1.9 8.3 0.8 — 11.0 Industrial revenue bonds — 7.8 — — 7.8 Total current liabilities 24.6 87.5 85.1 — 197.2 Senior notes payable 248.3 — — — 248.3 Accrued pension benefits costs - less current portion 39.2 17.9 12.5 (32.2 ) 37.4 Accrued postretirement benefits costs - less current portion 0.8 110.0 1.7 — 112.5 Due to affiliates - long term 218.0 81.1 596.0 (895.1 ) — Other liabilities 4.0 28.1 22.4 — 54.5 Deferred taxes — 1.7 98.8 — 100.5 Total noncurrent liabilities 510.3 238.8 731.4 (927.3 ) 553.2 Preferred stock 0.0 — — — 0.0 Common stock 0.9 — 0.1 (0.1 ) 0.9 Other shareholders' equity 829.5 697.2 114.5 (811.7 ) 829.5 Total shareholders' equity 830.4 697.2 114.6 (811.8 ) 830.4 TOTAL $ 1,365.3 $ 1,023.5 $ 931.1 $ (1,739.1 ) $ 1,580.8 Condensed Consolidating Balance Sheet As of December 31, 2017 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated Cash & cash equivalents $ 64.3 $ (0.1 ) $ 103.0 $ — $ 167.2 Restricted cash — 0.8 — — 0.8 Accounts receivable - net — 42.8 0.3 — 43.1 Due from affiliates 0.1 10.3 — — 10.4 Inventories 0.2 205.1 112.2 — 317.5 Prepaid and other current assets 3.3 0.8 10.6 — 14.7 Total current assets 67.9 259.7 226.1 — 553.7 Property, plant and equipment - net 19.4 295.8 656.7 — 971.9 Investment in subsidiaries 751.8 54.0 — (805.8 ) — Due from affiliates - long term 513.3 349.6 9.4 (872.3 ) — Other assets 28.0 34.1 25.9 (32.0 ) 56.0 TOTAL $ 1,380.4 $ 993.2 $ 918.1 $ (1,710.1 ) $ 1,581.6 Accounts payable, trade $ 6.3 $ 51.4 $ 32.2 $ — $ 89.9 Due to affiliates 0.4 2.6 17.4 — 20.4 Accrued and other current liabilities 16.0 19.3 26.1 — 61.4 Accrued employee benefits costs 1.9 8.3 0.8 — 11.0 Industrial revenue bonds — 7.8 — — 7.8 Total current liabilities 24.6 89.4 76.5 — 190.5 Senior notes payable 248.2 — — — 248.2 Accrued pension benefits costs - less current portion 39.5 18.3 13.1 (32.0 ) 38.9 Accrued postretirement benefits costs - less current portion 0.9 110.4 1.7 — 113.0 Other liabilities 3.5 32.0 22.4 — 57.9 Due to affiliates - long term 234.1 53.8 584.4 (872.3 ) — Deferred taxes — 1.7 101.8 — 103.5 Total noncurrent liabilities 526.2 216.2 723.4 (904.3 ) 561.5 Preferred stock 0.0 — — — 0.0 Common stock 0.9 — 0.1 (0.1 ) 0.9 Other shareholders' equity 828.7 687.6 118.1 (805.7 ) 828.7 Total shareholders' equity 829.6 687.6 118.2 (805.8 ) 829.6 TOTAL $ 1,380.4 $ 993.2 $ 918.1 $ (1,710.1 ) $ 1,581.6
Condensed Consolidating Statement of Cash Flows	Condensed Consolidating Statement of Cash Flows For the three months ended March 31, 2018 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated Net cash provided by (used in) operating activities $ (26.8 ) $ (26.8 ) $ 20.6 $ — $ (33.0 ) Purchase of property, plant and equipment (1.5 ) (0.4 ) (1.6 ) — (3.5 ) Intercompany transactions (23.8 ) — — 23.8 — Net cash provided by (used in) investing activities (25.3 ) (0.4 ) (1.6 ) 23.8 (3.5 ) Borrowings under revolving credit facilities 0.3 — — — 0.3 Repayments under revolving credit facilities (0.3 ) — — — (0.3 ) Issuance of common stock 0.1 — — — 0.1 Intercompany transactions (3.8 ) 27.2 0.4 (23.8 ) — Net cash provided by (used in) financing activities (3.7 ) 27.2 0.4 (23.8 ) 0.1 CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH (55.8 ) — 19.4 — (36.4 ) Cash, cash equivalents and restricted cash, beginning of period 64.3 0.7 103.0 — 168.0 Cash, cash equivalents and restricted cash, end of period $ 8.5 $ 0.7 $ 122.4 $ — $ 131.6 Condensed Consolidating Statement of Cash Flows For the three months ended March 31, 2017 The Company Combined Guarantor Subsidiaries Combined Non-Guarantor Subsidiaries Consolidating Adjustments Total Consolidated Net cash provided by (used in) operating activities $ (1.1 ) $ (21.8 ) $ 11.6 $ — $ (11.3 ) Purchase of property, plant and equipment (4.4 ) (2.3 ) (2.3 ) — (9.0 ) Proceeds from sale of property, plant and equipment — — 13.5 — 13.5 Intercompany transactions 19.2 23.6 (12.4 ) (30.4 ) — Net cash used in investing activities 14.8 21.3 (1.2 ) (30.4 ) 4.5 Borrowings under revolving credit facilities 0.2 — — — 0.2 Repayments under revolving credit facilities (0.2 ) — — — (0.2 ) Intercompany transactions (11.2 ) 0.8 (20.0 ) 30.4 — Net cash provided by (used in) financing activities (11.2 ) 0.8 (20.0 ) 30.4 — CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH 2.5 0.3 (9.6 ) — (6.8 ) Cash, cash equivalents and restricted cash, beginning of period 36.7 0.5 96.3 — 133.5 Cash, cash equivalents and restricted cash, end of period $ 39.2 $ 0.8 $ 86.7 $ — $ 126.7

Related party transactions - Na

Related party transactions - Narrative (Details)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
BHH [Member]
Related Party Transaction [Line Items]
Ownership percentage	40.00%
Consolidated Sales [Member] | Customer Concentration Risk [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Major customer, percentage of revenue, net (percent)	65.00%	77.00%
Glencore [Member]
Related Party Transaction [Line Items]
Ownership percentage by majority shareholder	47.40%
Common Stock [Member] | Glencore [Member]
Related Party Transaction [Line Items]
Ownership percentage by majority shareholder	42.90%

Related party transactions - Su

Related party transactions - Summary of related party transactions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Related Party Transaction [Line Items]
Net sales to Glencore	$ 296.2	$ 280.6
Glencore [Member]
Related Party Transaction [Line Items]
Net sales to Glencore	296.2	280.6
Purchases from Glencore	48.4	71.6
BHH [Member]
Related Party Transaction [Line Items]
Purchases from BHH	$ 7.4	$ 2.8

Revenue (Details)

Revenue (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Retained earnings (accumulated deficit)	$ (1,511,000,000)		$ (1,510,700,000)
Revenue	454,500,000
increase in accounts receivable	40,300,000	$ 23,800,000
United States [Member]
Disaggregation of Revenue [Line Items]
Revenue	268,200,000
Iceland [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 186,300,000
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Disaggregation of Revenue [Line Items]
Retained earnings (accumulated deficit)			$ 0

Fair value measurements (Detail

Fair value measurements (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
ASSETS:
Derivative instruments	$ 2	$ 1.7
Fair Value, Measurements, Recurring [Member]
ASSETS:
Cash equivalents	80	142.8
Trust assets	1.3	1.8
Surety bonds	1.6	1.6
Derivative instruments	2	1.7
TOTAL	84.9	147.9
LIABILITIES:
Contingent obligation - net	0	0
Derivative instruments	1.1	1.2
TOTAL	1.1	1.2
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
ASSETS:
Cash equivalents	80	142.8
Trust assets	1.3	1.8
Surety bonds	1.6	1.6
Derivative instruments	0	0
TOTAL	82.9	146.2
LIABILITIES:
Contingent obligation - net	0	0
Derivative instruments	0	0
TOTAL	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
ASSETS:
Cash equivalents	0	0
Trust assets	0	0
Surety bonds	0	0
Derivative instruments	0	0
TOTAL	0	0
LIABILITIES:
Contingent obligation - net	0	0
Derivative instruments	0	0
TOTAL	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
ASSETS:
Cash equivalents	0	0
Trust assets	0	0
Surety bonds	0	0
Derivative instruments	2	1.7
TOTAL	2	1.7
LIABILITIES:
Contingent obligation - net	0	0
Derivative instruments	1.1	1.2
TOTAL	$ 1.1	$ 1.2

Earnings (loss) per share (Deta

Earnings (loss) per share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Net loss	$ (0.3)	$ (15.1)
Amount allocated to common stockholders (as percent)	100.00%	100.00%
Basic EPS:
Net loss allocated to common stockholders	$ (0.3)	$ (15.1)
Net loss allocated to common stockholders (shares)	87.6	87.3
Net loss allocated to common stockholders, per share (in USD per share)	$ 0	$ (0.17)
Effect of Dilutive Securities:
Share-based compensation	$ 0	$ 0
Share-based compensation (shares)	0	0
Diluted EPS:
Net loss allocated to common stockholders with assumed conversion	$ (0.3)	$ (15.1)
Net loss allocated to common stockholders with assumed conversion (shares)	87.6	87.3
Net loss allocated to common stockholders with assumed conversion, per share (in USD per share)	$ 0	$ (0.17)
Securities excluded from calculation of diluted EPS (shares)	1.4	1.2

Shareholders' equity (Details)

Shareholders' equity (Details) - USD ($)	3 Months Ended		36 Months Ended	87 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2018	Dec. 31, 2017	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
Common stock, shares issued (in shares)	94,762,390		94,762,390	94,762,390	94,731,298
Common stock, shares, outstanding (in shares)	87,575,869		87,575,869	87,575,869	87,544,777
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	$ 70,000,000	$ 60,000,000
Treasury stock, shares, acquired (in shares)			0	7,186,521
Treasury stock, value, acquired, cost method				$ 86,276,000
Stock repurchase program, remaining authorized repurchase amount	$ 43,700,000		$ 43,700,000	$ 43,700,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, Ending balance (in shares)		87,262,115
Series A Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock par value (in dollars per share)	$ 0.01		$ 0.01	$ 0.01
Preferred stock, shares outstanding (in shares)	74,231		74,231	74,231	74,364,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, Beginning balance (in shares)	74,364	75,625
Conversion of convertible preferred stock (in shares)	(133)	(48)
Issuance for stock compensation plans (in shares)	0	0
Shares, Ending balance (in shares)	74,231	75,577	74,231	74,231
Treasury Stock [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)	87,544,777	87,250,897
Conversion of convertible preferred stock (in shares)	13,343	4,795
Issuance for stock compensation plans (in shares)	17,749	6,423
Shares, Ending balance (in shares)	87,575,869		87,575,869	87,575,869

Income taxes (Details)

Income taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Income tax benefit	$ 1	$ 0.3

Inventories (Details)

Inventories (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Inventory, Net [Abstract]
Raw materials	$ 108.1	$ 106.2
Work-in-process	54.3	49.6
Finished goods	41.7	40.9
Operating and other supplies	126.6	120.8
Total inventories	$ 330.7	$ 317.5

Debt (Details)

Debt (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Jun. 04, 2013
Debt Instrument [Line Items]
Hancock County industrial revenue bonds (IRBs) due 2028, interest payable quarterly (variable interest rates (not to exceed 12%)) (1)	$ 7.8	$ 7.8
Total debt	256.1	256
Long-term Debt [Member] | Senior secured notes due June 01, 2021 [Member]
Debt Instrument [Line Items]
7.5% senior secured notes due June 1, 2021, net of debt discount of $1.7 million and $1.8 million, respectively, interest payable semiannually	$ 248.3	$ 248.2
Maturity date	Jun. 1, 2021	Jun. 1, 2021
Stated interest rate, percentage	7.50%	7.50%	7.50%
Debt discount	$ 1.7	$ 1.8
Short-term Debt [Member] | Industrial revenue bonds due 2028 [Member]
Debt Instrument [Line Items]
Hancock County industrial revenue bonds (IRBs) due 2028, interest payable quarterly (variable interest rates (not to exceed 12%)) (1)	$ 7.8	$ 7.8
Maturity date	Apr. 1, 2028	Apr. 1, 2028
Stated interest rate, percentage	1.78%
Short-term Debt [Member] | Industrial revenue bonds due 2028 [Member] | Maximum [Member]
Debt Instrument [Line Items]
Effective interest rate, maximum	12.00%	12.00%

Debt - Credit Facility (Details

Debt - Credit Facility (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017	Nov. 27, 2013	Jun. 04, 2013
Line of Credit Facility [Line Items]
Fair value of debt instrument	$ 255,300,000	$ 258,300,000
U.S. revolving credit facility [Member] | Long-term Debt [Member]
Line of Credit Facility [Line Items]
Credit facility face amount	150,000,000
Credit facility maximum amount	150,000,000
Borrowing availability	150,000,000
Borrowing availability, net	110,900,000
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
Borrowing availability, net of outstanding letters of credit and borrowings	39,100,000
Outstanding borrowings	0
Iceland revolving line of credit [Member] | Long-term Debt [Member]
Line of Credit Facility [Line Items]
Credit facility face amount			$ 50,000,000
Credit facility maximum amount	50,000,000
Borrowing availability	50,000,000
Outstanding borrowings	0
Borrowing availability, net	$ 50,000,000
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%		7.50%

Commitments and contingencies (

Commitments and contingencies (Details)	Mar. 31, 2018LaborUnionsMW	Aug. 18, 2017USD ($)	Sep. 30, 2017USD ($)	Mar. 31, 2018USD ($)LaborUnionsMW	Mar. 31, 2017USD ($)	Dec. 31, 2013USD ($)	Mar. 31, 2018USD ($)LaborUnionsMW
Environmental Contingencies [Abstract]
Environmental remediation expense for Hydrocarbon Recovery Plan							$ 1,100,000
Labor Commitments [Abstract]
Percentage of total work force in union	63.00%			63.00%			63.00%
Percentage of Grundartangi work force represented by the labor unions (in hundredths)	85.00%			85.00%			85.00%
Number of labor unions Grundartangi subsidiary entered into a new labor agreement with | LaborUnions	5			5			5
Percentage of U.S. based work force represented by a union (in hundredths)	51.00%			51.00%			51.00%
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 supply agreement, termination notice period				60 days
Power agreement, power supply from source one, percentage				25.00%
Power agreement, power supply from source two, percentage				75.00%
Grundartangi - HS, Landsvirkjun and OR [Member]
Power Contingencies [Abstract]
Power currently available under the power purchase agreement (in megawatts) | MW	525			525			525
Grundartangi - Landsvirkjun [Member]
Power Contingencies [Abstract]
Power currently available under the power purchase agreement (in megawatts) | MW	161			161			161
Helguvik [Member]
Power Contingencies [Abstract]
Power currently available under the power purchase agreement (in megawatts) | MW	47.5			47.5			47.5
NETHERLANDS
Labor Commitments [Abstract]
Percentage of Vlissingen work force represented by the labor union (in hundredths)	100.00%			100.00%			100.00%
Ravenswood Retiree Medical Benefits Changes [Member]
Ravenswood litigation [Abstract]
Ravenswood litigation settlement amount		$ 23,000,000
Ravenswood litigation settlement installment period	9 years	10 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				$ 11,100,000

Components of accumulated oth42

Components of accumulated other comprehensive loss (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive loss before income tax effect	$ (98.6)		$ (99.4)
Income tax effect	7.3		7.7
Accumulated other comprehensive loss	(91.3)		(91.7)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity, beginning balance	829.6
Equity, ending balance	830.4
Defined benefit plan and other postretirement liabilities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive loss before income tax effect	(101.2)		(102.1)
Income tax effect	7.8		8.2
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity, beginning balance	(93.8)	$ (116.2)
Net amount reclassified to net loss	0.4	0.7
Equity, ending balance	(93.4)	(115.5)
Unrealized gain (loss) on financial instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive loss before income tax effect	2.6		2.7
Income tax effect	(0.5)		$ (0.5)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity, beginning balance	2.1	2.3
Net amount reclassified to net loss	0	0
Equity, ending balance	2.1	2.3
AOCI Attributable to Parent [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity, beginning balance	(91.7)	(113.9)
Net amount reclassified to net loss	0.4	0.7
Equity, ending balance	$ (91.3)	$ (113.2)

Components of accumulated oth43

Components of accumulated other comprehensive loss - Reclassifications out of AOCI (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Cost of goods sold	$ 440	$ 348.9
Selling, general and administrative expenses	10.7	10.7
Other operating expense, net	0.3	1
Income tax effect	(1)	(0.3)
Net of tax	0.3	15.1
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	0.7	1.3
Selling, general and administrative expenses	(0.4)	0.1
Other operating expense, net	0.5	0.4
Income tax effect	(0.4)	(1.1)
Net of tax	0.4	0.7
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized gain (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 be44

Components of net periodic benefit cost (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 1.1	$ 1.2
Interest cost	3.1	3.3
Expected return on plan assets	(5.3)	(4.7)
Amortization of prior service costs	0	0
Amortization of net loss	1.5	1.2
Net periodic benefit cost	0.4	1
Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	0.1	0.2
Interest cost	1.1	1.4
Amortization of prior service costs	(1.8)	(0.3)
Amortization of net loss	1.1	0.9
Net periodic benefit cost	$ 0.5	$ 2.2

Derivatives (Details)

Derivatives (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018USD ($)MWht	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)
Derivative [Line Items]
Derivative asset	$ 2		$ 1.7
Derivative liability	1.1		1.2
Net gain (loss) on forward and derivative contracts	$ 0.7	$ (16.1)	$ (16.1)
LME Swap [Member]
Derivative [Line Items]
Other forward delivery contracts to sell primary aluminum (in tonnes) | t	3,090
Price Swap [Member]
Derivative [Line Items]
Open position to offset fixed prices | t	11,337
Power Price Swap [Member] | Grundartangi [Member]
Derivative [Line Items]
Percentage of power purchases included in forward price contract (percent)	4.00%
Power available | MWh	256,200

Condensed consolidating finan46

Condensed consolidating financial information - Statement of Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Revenue, Net [Abstract]
Related parties	$ 296.2	$ 280.6
Other customers	158.3	85.2
Total net sales	454.5	365.8
Cost of goods sold	440	348.9
Gross profit	14.5	16.9
Selling, general and administrative expenses	10.7	10.7
Other operating expense, net	0.3	1
Operating income	3.5	5.2
Interest expense	(5.5)	(5.6)
Intercompany interest	0	0
Interest income	0.5	0.2
Net gain (loss) on forward and derivative contracts	0.7	(16.1)	$ (16.1)
Other income (expense) - net	(1.1)	0.4
Loss before income taxes and equity in earnings of joint ventures	(1.9)	(15.9)
Income tax (expense) benefit	1	0.3
Loss before equity in earnings of joint ventures	(0.9)	(15.6)
Equity in earnings (loss) of joint ventures	0.6	0.5
Net loss	(0.3)	(15.1)
Other comprehensive income (loss) before income tax effect	0.8	1.8
Income tax effect	(0.4)	(1.1)
Other comprehensive income	0.4	0.7
Total comprehensive income (loss)	0.1	(14.4)
Consolidating Adjustments [Member]
Revenue, Net [Abstract]
Related parties	0	0
Other customers	0	0
Total net sales	0	0
Cost of goods sold	0	0
Gross profit	0	0
Selling, general and administrative expenses	0	0
Other operating expense, net	0	0
Operating income	0	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
Loss before income taxes and equity in earnings of joint ventures	0	0
Income tax (expense) benefit	0	0
Loss before equity in earnings of joint ventures	0	0
Equity in earnings (loss) of joint ventures	(4.9)	9.4
Net loss	(4.9)	9.4
Other comprehensive income (loss) before income tax effect	(1.1)	(1.7)
Income tax effect	0	0
Other comprehensive income	(1.1)	(1.7)
Total comprehensive income (loss)	(6)	7.7
The Company [Member] | Reportable Legal Entities [Member]
Revenue, Net [Abstract]
Related parties	0	0
Other customers	0	0
Total net sales	0	0
Cost of goods sold	0	0
Gross profit	0	0
Selling, general and administrative expenses	10	10.2
Other operating expense, net	0	0
Operating income	(10)	(10.2)
Interest expense	(5.1)	(5.2)
Intercompany interest	9	9
Interest income	0.2	0.1
Net gain (loss) on forward and derivative contracts	0	0
Other income (expense) - net	0.5	0.8
Loss before income taxes and equity in earnings of joint ventures	(5.4)	(5.5)
Income tax (expense) benefit	(0.1)	0.6
Loss before equity in earnings of joint ventures	(5.5)	(4.9)
Equity in earnings (loss) of joint ventures	5.2	(10.2)
Net loss	(0.3)	(15.1)
Other comprehensive income (loss) before income tax effect	0.8	1.8
Income tax effect	(0.4)	(1.1)
Other comprehensive income	0.4	0.7
Total comprehensive income (loss)	$ 0.1	(14.4)
Combined Guarantor Subsidiaries [Member]
Condensed Statement of Income Captions [Line Items]
Ownership percentage	100.00%
Combined Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Revenue, Net [Abstract]
Related parties	$ 110.7	131.1
Other customers	157.5	85.2
Total net sales	268.2	216.3
Cost of goods sold	261.2	213.8
Gross profit	7	2.5
Selling, general and administrative expenses	0	0
Other operating expense, net	0	0
Operating income	7	2.5
Interest expense	(0.4)	(0.4)
Intercompany interest	2.3	2.1
Interest income	0	0
Net gain (loss) on forward and derivative contracts	0.3	(15.8)
Other income (expense) - net	0	0
Loss before income taxes and equity in earnings of joint ventures	9.2	(11.6)
Income tax (expense) benefit	0	0.5
Loss before equity in earnings of joint ventures	9.2	(11.1)
Equity in earnings (loss) of joint ventures	(0.3)	0.8
Net loss	8.9	(10.3)
Other comprehensive income (loss) before income tax effect	0.7	1.3
Income tax effect	0	0
Other comprehensive income	0.7	1.3
Total comprehensive income (loss)	9.6	(9)
Combined Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Revenue, Net [Abstract]
Related parties	185.5	149.5
Other customers	0.8	0
Total net sales	186.3	149.5
Cost of goods sold	178.8	135.1
Gross profit	7.5	14.4
Selling, general and administrative expenses	0.7	0.5
Other operating expense, net	0.3	1
Operating income	6.5	12.9
Interest expense	0	0
Intercompany interest	(11.3)	(11.1)
Interest income	0.3	0.1
Net gain (loss) on forward and derivative contracts	0.4	(0.3)
Other income (expense) - net	(1.6)	(0.4)
Loss before income taxes and equity in earnings of joint ventures	(5.7)	1.2
Income tax (expense) benefit	1.1	(0.8)
Loss before equity in earnings of joint ventures	(4.6)	0.4
Equity in earnings (loss) of joint ventures	0.6	0.5
Net loss	(4)	0.9
Other comprehensive income (loss) before income tax effect	0.4	0.4
Income tax effect	0	0
Other comprehensive income	0.4	0.4
Total comprehensive income (loss)	$ (3.6)	$ 1.3

Condensed consolidating finan47

Condensed consolidating financial information - Balance Sheet (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Condensed Balance Sheet Statements, Captions [Line Items]
Cash & cash equivalents	$ 130.8	$ 167.2
Restricted cash	0.8	0.8
Accounts receivable - net	83.4	43.1
Due from affiliates	8.7	10.4
Inventories	330.7	317.5
Prepaid and other current assets	14.2	14.7
Total current assets	568.6	553.7
Property, plant and equipment - net	955.1	971.9
Investment in subsidiaries	0	0
Due from affiliates - long term	0	0
Other assets	57.1	56
TOTAL	1,580.8	1,581.6
Accounts payable, trade	95.8	89.9
Due to affiliates	14.6	20.4
Accrued and other current liabilities	68	61.4
Accrued employee benefits costs	11	11
Industrial revenue bonds	7.8	7.8
Total current liabilities	197.2	190.5
Senior notes payable	248.3	248.2
Accrued pension benefits costs - less current portion	37.4	38.9
Accrued postretirement benefits costs - less current portion	112.5	113
Due to affiliates - long term	0
Other liabilities	54.5	57.9
Intercompany loan		0
Deferred taxes	100.5	103.5
Total noncurrent liabilities	553.2	561.5
Preferred stock	0	0
Common stock	0.9	0.9
Other shareholders' equity	829.5	828.7
Total shareholders’ equity	830.4	829.6
TOTAL	1,580.8	1,581.6
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
Prepaid and other current assets	0	0
Total current assets	0	0
Property, plant and equipment - net	0	0
Investment in subsidiaries	(811.8)	(805.8)
Due from affiliates - long term	(895.1)	(872.3)
Other assets	(32.2)	(32)
TOTAL	(1,739.1)	(1,710.1)
Accounts payable, trade	0	0
Due to affiliates	0	0
Accrued and other current liabilities	0	0
Accrued employee benefits costs	0	0
Industrial revenue bonds	0	0
Total current liabilities	0	0
Senior notes payable	0	0
Accrued pension benefits costs - less current portion	(32.2)	(32)
Accrued postretirement benefits costs - less current portion	0	0
Due to affiliates - long term	(895.1)
Other liabilities	0	0
Intercompany loan		(872.3)
Deferred taxes	0	0
Total noncurrent liabilities	(927.3)	(904.3)
Preferred stock	0	0
Common stock	(0.1)	(0.1)
Other shareholders' equity	(811.7)	(805.7)
Total shareholders’ equity	(811.8)	(805.8)
TOTAL	(1,739.1)	(1,710.1)
The Company [Member] | Reportable Legal Entities [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash & cash equivalents	8.5	64.3
Restricted cash	0	0
Accounts receivable - net	0	0
Due from affiliates	0	0.1
Inventories	0.2	0.2
Prepaid and other current assets	3.4	3.3
Total current assets	12.1	67.9
Property, plant and equipment - net	20.6	19.4
Investment in subsidiaries	758.2	751.8
Due from affiliates - long term	546.1	513.3
Other assets	28.3	28
TOTAL	1,365.3	1,380.4
Accounts payable, trade	1.8	6.3
Due to affiliates	0.7	0.4
Accrued and other current liabilities	20.2	16
Accrued employee benefits costs	1.9	1.9
Industrial revenue bonds	0	0
Total current liabilities	24.6	24.6
Senior notes payable	248.3	248.2
Accrued pension benefits costs - less current portion	39.2	39.5
Accrued postretirement benefits costs - less current portion	0.8	0.9
Due to affiliates - long term	218
Other liabilities	4	3.5
Intercompany loan		234.1
Deferred taxes	0	0
Total noncurrent liabilities	510.3	526.2
Preferred stock	0	0
Common stock	0.9	0.9
Other shareholders' equity	829.5	828.7
Total shareholders’ equity	830.4	829.6
TOTAL	1,365.3	1,380.4
Combined Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash & cash equivalents	(0.1)	(0.1)
Restricted cash	0.8	0.8
Accounts receivable - net	83.2	42.8
Due from affiliates	7.9	10.3
Inventories	216.8	205.1
Prepaid and other current assets	0.5	0.8
Total current assets	309.1	259.7
Property, plant and equipment - net	286.9	295.8
Investment in subsidiaries	53.6	54
Due from affiliates - long term	339.6	349.6
Other assets	34.3	34.1
TOTAL	1,023.5	993.2
Accounts payable, trade	55.3	51.4
Due to affiliates	(0.5)	2.6
Accrued and other current liabilities	16.6	19.3
Accrued employee benefits costs	8.3	8.3
Industrial revenue bonds	7.8	7.8
Total current liabilities	87.5	89.4
Senior notes payable	0	0
Accrued pension benefits costs - less current portion	17.9	18.3
Accrued postretirement benefits costs - less current portion	110	110.4
Due to affiliates - long term	81.1
Other liabilities	28.1	32
Intercompany loan		53.8
Deferred taxes	1.7	1.7
Total noncurrent liabilities	238.8	216.2
Preferred stock	0	0
Common stock	0	0
Other shareholders' equity	697.2	687.6
Total shareholders’ equity	697.2	687.6
TOTAL	1,023.5	993.2
Combined Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash & cash equivalents	122.4	103
Restricted cash	0	0
Accounts receivable - net	0.2	0.3
Due from affiliates	0.8	0
Inventories	113.7	112.2
Prepaid and other current assets	10.3	10.6
Total current assets	247.4	226.1
Property, plant and equipment - net	647.6	656.7
Investment in subsidiaries	0	0
Due from affiliates - long term	9.4	9.4
Other assets	26.7	25.9
TOTAL	931.1	918.1
Accounts payable, trade	38.7	32.2
Due to affiliates	14.4	17.4
Accrued and other current liabilities	31.2	26.1
Accrued employee benefits costs	0.8	0.8
Industrial revenue bonds	0	0
Total current liabilities	85.1	76.5
Senior notes payable	0	0
Accrued pension benefits costs - less current portion	12.5	13.1
Accrued postretirement benefits costs - less current portion	1.7	1.7
Due to affiliates - long term	596
Other liabilities	22.4	22.4
Intercompany loan		584.4
Deferred taxes	98.8	101.8
Total noncurrent liabilities	731.4	723.4
Preferred stock	0	0
Common stock	0.1	0.1
Other shareholders' equity	114.5	118.1
Total shareholders’ equity	114.6	118.2
TOTAL	$ 931.1	$ 918.1

Condensed consolidating finan48

Condensed consolidating financial information - Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	$ (33)	$ (11.3)
Net cash provided by (used in) investing activities
Purchase of property, plant and equipment	(3.5)	(9)
Proceeds from sale of property, plant and equipment		13.5
Intercompany transactions	0	0
Net cash provided by (used in) investing activities	(3.5)	4.5
Net cash provided by (used in) financing activities
Borrowings under revolving credit facilities	0.3	0.2
Repayments under revolving credit facilities	(0.3)	(0.2)
Issuance of common stock	0.1	0
Intercompany transactions	0	0
Net cash provided by financing activities	0.1	0
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(36.4)	(6.8)
Cash, cash equivalents and restricted cash, beginning of period	168	133.5
Cash, cash equivalents and restricted cash, end of period	131.6	126.7
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 property, plant and equipment		0
Intercompany transactions	23.8	(30.4)
Net cash provided by (used in) investing activities	23.8	(30.4)
Net cash provided by (used in) financing activities
Borrowings under revolving credit facilities	0	0
Repayments under revolving credit facilities	0	0
Issuance of common stock	0
Intercompany transactions	(23.8)	30.4
Net cash provided by financing activities	(23.8)	30.4
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	(26.8)	(1.1)
Net cash provided by (used in) investing activities
Purchase of property, plant and equipment	(1.5)	(4.4)
Proceeds from sale of property, plant and equipment		0
Intercompany transactions	(23.8)	19.2
Net cash provided by (used in) investing activities	(25.3)	14.8
Net cash provided by (used in) financing activities
Borrowings under revolving credit facilities	0.3	0.2
Repayments under revolving credit facilities	(0.3)	(0.2)
Issuance of common stock	0.1
Intercompany transactions	(3.8)	(11.2)
Net cash provided by financing activities	(3.7)	(11.2)
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(55.8)	2.5
Cash, cash equivalents and restricted cash, beginning of period	64.3	36.7
Cash, cash equivalents and restricted cash, end of period	8.5	39.2
Combined Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	(26.8)	(21.8)
Net cash provided by (used in) investing activities
Purchase of property, plant and equipment	(0.4)	(2.3)
Proceeds from sale of property, plant and equipment		0
Intercompany transactions	0	23.6
Net cash provided by (used in) investing activities	(0.4)	21.3
Net cash provided by (used in) financing activities
Borrowings under revolving credit facilities	0	0
Repayments under revolving credit facilities	0	0
Issuance of common stock	0
Intercompany transactions	27.2	0.8
Net cash provided by financing activities	27.2	0.8
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	0	0.3
Cash, cash equivalents and restricted cash, beginning of period	0.7	0.5
Cash, cash equivalents and restricted cash, end of period	0.7	0.8
Combined Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	20.6	11.6
Net cash provided by (used in) investing activities
Purchase of property, plant and equipment	(1.6)	(2.3)
Proceeds from sale of property, plant and equipment		13.5
Intercompany transactions	0	(12.4)
Net cash provided by (used in) investing activities	(1.6)	(1.2)
Net cash provided by (used in) financing activities
Borrowings under revolving credit facilities	0	0
Repayments under revolving credit facilities	0	0
Issuance of common stock	0
Intercompany transactions	0.4	(20)
Net cash provided by financing activities	0.4	(20)
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	19.4	(9.6)
Cash, cash equivalents and restricted cash, beginning of period	103	96.3
Cash, cash equivalents and restricted cash, end of period	$ 122.4	$ 86.7