XML 102 R65.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Share-Based Compensation (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2017
Text block1 [abstract] |
Summary of Performance-Based RSU | The following table lists the inputs to the model used for the PSUs granted in 2017 and 2016:
|  | Year ended December 31, 2017 |  |  | Year ended December 31, 2016 |
Fair value at grant date (in Euros) |  |  | 11.52 |  |  |  | [6.76 – 9.86] |
Share price at grant date (in Euros) |  |  | 7.50 |  |  |  | [4.46 – 5.61] |
Dividend yield |  |  | — |  |  |  | — |
Expected volatility |  |  | 75% |  |  |  | [69% – 71%] |
Risk-free interest rate (U.S. government bond yield) |  |  | 1.51% |  |  |  | [0.76% – 1.27%] |
Model used |  |  | Monte Carlo |  |  |  | Monte Carlo |
Summary of Weighted-Average Fair Value | The following table illustrates the number, weighted-average fair value of, and movements in shares during the year:
|  | Performance-Based RSU |  |  | Restricted Stock Units |  |  | Equity Award Plans |
|  | Potential Shares |  |  | Weighted-Average Grant-Date Fair Value per Share |  |  | Potential Shares |  |  | Weighted-Average Grant-Date Fair Value per Share |  |  | Potential Shares |  |  | Weighted-Average Grant-Date Fair Value per Share |
At January 1, 2016 |  |  | 1,007,000 |  |  | € | 7.77 |  |  |  | 269,500 |  |  | € | 16.10 |  |  |  | 34,865 |  |  | € | 14.11 |
Granted(A) |  |  | 1,292,000 |  |  | € | 7.56 |  |  |  | 340,300 |  |  | € | 5.40 |  |  |  | 81,858 |  |  | € | 4.02 |
Over-performance(B) |  |  | 47,229 |  |  | € | 7.10 |  |  |  | — |  |  |  | — |  |  |  | — |  |  |  | — |
Vested |  |  | — |  |  |  | — |  |  |  | (87,300 | ) |  | € | 19.75 |  |  |  | (21,842 | ) |  | € | 15.84 |
Forfeited(C) |  |  | (279,394 | ) |  | € | 8.71 |  |  |  | (43,000 | ) |  | € | 16.40 |  |  |  | — |  |  |  | — |
At December 31, 2016 |  |  | 2,066,835 |  |  | € | 7.50 |  |  |  | 479,500 |  |  | € | 7.82 |  |  |  | 94,881 |  |  | € | 5.01 |
Granted(A) |  |  | 892,781 |  |  | € | 11.52 |  |  |  | 703,180 |  |  | € | 7.50 |  |  |  | 54,409 |  |  | € | 6.09 |
Over-performance(B) |  |  | 552,728 |  |  | € | 7.63 |  |  |  | — |  |  |  | — |  |  |  | — |  |  |  | — |
Vested |  |  | — |  |  |  | — |  |  |  | (125,000 | ) |  | € | 7.02 |  |  |  | (53,950 | ) |  | € | 5.76 |
Forfeited(C) |  |  | (254,504 | ) |  | € | 8.29 |  |  |  | (113,180 | ) |  | € | 7.27 |  |  |  | — |  |  |  | — |
At December 31, 2017 |  |  | 3,257,840 |  |  | € | 8.56 |  |  |  | 944,500 |  |  | € | 7.76 |  |  |  | 95,340 |  |  | € | 5.20 |
(A) | For PSUs, the number of potential shares granted is presented using a vesting multiplier of 100%.
(B) | When the achievement of TSR performance exceeds the vesting multiplier of 100%, the additional potential shares are presented as over-performance shares.
(C) | For potential shares related to PSUs, 175,837 were forfeited following the departure of certain beneficiaries and 78,667 were forfeited in relation to the non-fulfilment of performance conditions.

X
- Definition Text Block [Abstract] + References No definition available. + Details
Name: | cstm_TextBlock1Abstract
Namespace Prefix: | cstm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The disclosure of information about indirect, by reference to the fair value of the equity instruments granted, measurement of the fair value of goods or services received as consideration for the entity's other equity instruments (ie other than share options). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 2 -IssueDate 2017-01-01 -Paragraph 47 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2017-03-01&anchor=para_47_b&doctype=Standard -URIDate 2017-03-09 + Details
Name: | ifrs-full_DisclosureOfIndirectMeasurementOfFairValueOfGoodsOrServicesReceivedOtherEquityInstrumentsGrantedDuringPeriodExplanatory
Namespace Prefix: | ifrs-full_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition The disclosure of the number and weighted average exercise prices of other equity instruments (ie other than share options). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IFRS -Number 2 -IssueDate 2017-01-01 -Paragraph 45 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2017-03-01&anchor=para_45&doctype=Standard -URIDate 2017-03-09 + Details
Name: | ifrs-full_DisclosureOfNumberAndWeightedAverageExercisePricesOfOtherEquityInstrumentsExplanatory
Namespace Prefix: | ifrs-full_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration