Represents the total increase (decrease) in the fair value of a business acquisition.

No definition available.

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- Definition

Represents the excess of recoverable value over carrying value of a business acquisition in determination of goodwill impairment.

+ References

No definition available.

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- References

No definition available.

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- Definition

The amount of assets representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognised. [Refer: Business combinations [member]]

+ References

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- Definition

The amount of impairment loss recognised in profit or loss for goodwill. [Refer: Impairment loss recognised in profit or loss; Goodwill]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

The percentage of voting equity interests acquired in a business combination. [Refer: Business combinations [member]]

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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