XML 60 R48.htm IDEA: XBRL DOCUMENT
v3.19.1

Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2019 | Mar. 31, 2018 | Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |
Other comprehensive loss before income tax effect | $ (104.3) |  | $ (104.8)
Income tax effect | 4.6 |  | 6.1
Accumulated other comprehensive loss | (99.7) |  | (98.7)
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |
Balance, start | 762.2 | $ 829.6 |
Net amount reclassified to net income (loss) | 0.3 | 0.4 |
Balance, end | 728.1 | 830.4 |
Defined benefit plan and other postretirement liabilities [Member] |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |
Other comprehensive loss before income tax effect | (106.7) |  | (107.3)
Income tax effect | (5.1) |  | (6.6)
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |
Balance, start | (100.7) | (93.8) |
Impact of ASU 2018-02 | (1.3) |  |
Net amount reclassified to net income (loss) | 0.3 | 0.4 |
Balance, end | (101.7) | (93.4) |
Unrealized gain (loss) on financial instruments [Member] |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |
Other comprehensive loss before income tax effect | 2.4 |  | 2.5
Income tax effect | 0.5 |  | $ 0.5
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |
Balance, start | 2.0 | 2.1 |
Impact of ASU 2018-02 | 0.0 |  |
Net amount reclassified to net income (loss) | 0.0 | 0.0 |
Balance, end | 2.0 | 2.1 |
Accumulated other comprehensive loss [Member] |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |
Balance, start | (98.7) | (91.7) |
Impact of ASU 2018-02 | (1.3) |  |
Balance, end | $ (99.7) | $ (91.3) |

X
- Definition The tax effect of AOCI as reported on the balance sheet. + References No definition available. + Details
Name: | cenx_AccumulatedOtherComprehensiveIncomeTaxEffect
Namespace Prefix: | cenx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Tax Cuts and Jobs Act of 2017, Reclassification from AOCI to Retained Earnings, Tax Effect + References No definition available. + Details
Name: | cenx_TaxCutsandJobsActof2017ReclassificationfromAOCItoRetainedEarningsTaxEffect
Namespace Prefix: | cenx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | us-gaap_AOCIAttributableToParentNetOfTaxRollForward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount before tax of increase (decrease) in accumulated equity from transactions and other events and circumstances from non-owner sources, including portion attributable to noncontrolling interest. Excludes net income (loss), and accumulated changes in equity from transactions resulting from investments by owners (distributions to owners). + References No definition available. + Details
Name: | us-gaap_AccumulatedOtherComprehensiveIncomeLossBeforeTax1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=114867106&loc=d3e637-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669686-108580 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=114867106&loc=d3e681-108580 + Details
Name: | us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount after tax of reclassification adjustments of other comprehensive income (loss) attributable to parent. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669686-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 55 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=109228884&loc=d3e1436-108581 + Details
Name: | us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB Topic 4.E) -URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74512-122707 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(31)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(30)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_StockholdersEquity
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedOtherComprehensiveIncomeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |