XML 39 R25.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Shareholders' equity (Tables) | 9 Months Ended
--- | ---
Sep. 30, 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 nine months ended September 30, 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 | (272 | ) |  | — |  |  | 27,263 |
Issuance for share-based compensation plans | — |  |  | — |  |  | 36,266 |
Ending balance as of September 30, 2018 | 74,092 |  |  | 7,186,521 |  |  | 87,608,306 |
Beginning balance as of December 31, 2016 | 75,625 |  |  | 7,186,521 |  |  | 87,250,897 |
Conversion of convertible preferred stock | (326 | ) |  | — |  |  | 32,619 |
Issuance for share-based compensation plans | — |  |  | — |  |  | 43,436 |
Ending balance as of September 30, 2017 | 75,299 |  |  | 7,186,521 |  |  | 87,326,952 |

X
- Definition Tabular disclosure of the change in preferred stock, treasury stock and common stock outstanding. + References No definition available. + Details
Name: | cenx_ScheduleOfCommonandPreferredStockRollForwardTableTextBlock
Namespace Prefix: | cenx_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_StockholdersEquityNoteAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration