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v3.19.1

Goodwill - Sensitivity to changes in assumptions (Details) - USD ($) $ in Thousands | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2018 | Dec. 23, 2015
Disclosure of significant unobservable inputs used in fair value measurement of assets [abstract] |  |  |  |
Goodwill | $ 205,287 | $ 230,210 | $ 202,848 |
Impairment charge related to goodwill | 30,618 | 194,612 |  |
Electrometallurgy - North America |  |  |  |
Disclosure of significant unobservable inputs used in fair value measurement of assets [abstract] |  |  |  |
Goodwill | 205,287 |  | 202,848 |
Electrometallurgy United States Segment |  |  |  |
Disclosure of significant unobservable inputs used in fair value measurement of assets [abstract] |  |  |  |
Goodwill |  |  | 172,900 |
Excess of recoverable value over carrying value |  |  | 43,200 |
Electrometallurgy United States Segment | Sensitivity On Discount Rate, Decrease By Ten Percent |  |  |  |
Disclosure of significant unobservable inputs used in fair value measurement of assets [abstract] |  |  |  |
Increase (decrease) in value of cash generating units |  |  | 94,400 |
Electrometallurgy United States Segment | Sensitivity On Discount Rate, Increase By Ten Percent |  |  |  |
Disclosure of significant unobservable inputs used in fair value measurement of assets [abstract] |  |  |  |
Increase (decrease) in value of cash generating units |  |  | (73,700) |
Electrometallurgy United States Segment | Sensitivity On Long Term Growth Rate, Decrease By Ten Percent |  |  |  |
Disclosure of significant unobservable inputs used in fair value measurement of assets [abstract] |  |  |  |
Increase (decrease) in value of cash generating units |  |  | (11,000) |
Electrometallurgy United States Segment | Sensitivity On Long Term Growth Rate, Increase By Ten Percent |  |  |  |
Disclosure of significant unobservable inputs used in fair value measurement of assets [abstract] |  |  |  |
Increase (decrease) in value of cash generating units |  |  | 11,500 |
Electrometallurgy United States Segment | Sensitivity On Cash Flows, Decrease By Ten Percent |  |  |  |
Disclosure of significant unobservable inputs used in fair value measurement of assets [abstract] |  |  |  |
Increase (decrease) in value of cash generating units |  |  | (59,700) |
Electrometallurgy United States Segment | Sensitivity On Cash Flows, Increase By Ten Percent |  |  |  |
Disclosure of significant unobservable inputs used in fair value measurement of assets [abstract] |  |  |  |
Increase (decrease) in value of cash generating units |  |  | 59,700 |
Electrometallurgy Canada Segment |  |  |  |
Disclosure of significant unobservable inputs used in fair value measurement of assets [abstract] |  |  |  |
Goodwill |  |  | 29,900 |
Excess of recoverable value over carrying value |  |  | 4,800 |
Electrometallurgy Canada Segment | Sensitivity On Discount Rate, Decrease By Ten Percent |  |  |  |
Disclosure of significant unobservable inputs used in fair value measurement of assets [abstract] |  |  |  |
Increase (decrease) in value of cash generating units |  |  | 17,700 |
Electrometallurgy Canada Segment | Sensitivity On Discount Rate, Increase By Ten Percent |  |  |  |
Disclosure of significant unobservable inputs used in fair value measurement of assets [abstract] |  |  |  |
Increase (decrease) in value of cash generating units |  |  | (13,800) |
Electrometallurgy Canada Segment | Sensitivity On Long Term Growth Rate, Decrease By Ten Percent |  |  |  |
Disclosure of significant unobservable inputs used in fair value measurement of assets [abstract] |  |  |  |
Increase (decrease) in value of cash generating units |  |  | (2,200) |
Electrometallurgy Canada Segment | Sensitivity On Long Term Growth Rate, Increase By Ten Percent |  |  |  |
Disclosure of significant unobservable inputs used in fair value measurement of assets [abstract] |  |  |  |
Increase (decrease) in value of cash generating units |  |  | 2,300 |
Electrometallurgy Canada Segment | Sensitivity On Cash Flows, Decrease By Ten Percent |  |  |  |
Disclosure of significant unobservable inputs used in fair value measurement of assets [abstract] |  |  |  |
Increase (decrease) in value of cash generating units |  |  | (12,100) |
Electrometallurgy Canada Segment | Sensitivity On Cash Flows, Increase By Ten Percent |  |  |  |
Disclosure of significant unobservable inputs used in fair value measurement of assets [abstract] |  |  |  |
Increase (decrease) in value of cash generating units |  |  | 12,100 |
Globe Specialty Metals Inc |  |  |  |
Disclosure of significant unobservable inputs used in fair value measurement of assets [abstract] |  |  |  |
Percentage of equity interests acquired |  |  |  | 100.00%
Goodwill | 205,287 | $ 230,210 | 202,848 |
Impairment charge related to goodwill | $ 30,618 |  |  |
Globe Specialty Metals Inc | Electrometallurgy United States Segment |  |  |  |
Disclosure of significant unobservable inputs used in fair value measurement of assets [abstract] |  |  |  |
Goodwill |  |  | 172,913 |
Globe Specialty Metals Inc | Electrometallurgy Canada Segment |  |  |  |
Disclosure of significant unobservable inputs used in fair value measurement of assets [abstract] |  |  |  |
Goodwill |  |  | $ 29,935 |

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