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Restructuring Charges (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restructuring Cost and Reserve [Line Items]
Reduction in workforce (in hundredths)	10.00%
Annualized savings from reduction of workforce	$ 20us-gaap_EffectOnFutureEarningsAmount
Restructuring and Other Charges [Abstract]
Impairment of assets	23.7us-gaap_AssetImpairmentCharges	0us-gaap_AssetImpairmentCharges	0us-gaap_AssetImpairmentCharges
Severance and other employee costs	18.8us-gaap_SeveranceCosts1
Other	0.7us-gaap_OtherRestructuringCosts
Total restructuring and other charges	43.2us-gaap_RestructuringCharges	0us-gaap_RestructuringCharges	0us-gaap_RestructuringCharges
Restructuring Reserve [Roll Forward]
Restructuring liability, beginning of period	0us-gaap_RestructuringReserve
Additional provisions	18.8us-gaap_SeveranceCosts1
Cash payments	(4.2)us-gaap_PaymentsForRestructuring
Restructuring liability, end of period	14.6us-gaap_RestructuringReserve	0us-gaap_RestructuringReserve
Performance Materials [Member]
Restructuring and Other Charges [Abstract]
Impairment of assets	0.4
Severance and other employee costs	5.6
Restructuring Reserve [Roll Forward]
Additional provisions	5.6
Specialty Minerals [Member]
Restructuring and Other Charges [Abstract]
Severance and other employee costs	3.0
Restructuring Reserve [Roll Forward]
Additional provisions	3.0
Refractories [Member]
Restructuring and Other Charges [Abstract]
Severance and other employee costs	0.7
Restructuring Reserve [Roll Forward]
Additional provisions	0.7
Construction Technologies [Member]
Restructuring and Other Charges [Abstract]
Impairment of assets	11.7
Severance and other employee costs	5.8
Restructuring Reserve [Roll Forward]
Additional provisions	5.8
Energy Services [Member]
Restructuring and Other Charges [Abstract]
Impairment of assets	11.6
Severance and other employee costs	3.7
Restructuring Reserve [Roll Forward]
Additional provisions	$ 3.7