Commitments and Contingent Liabilities (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($) facility payment shares	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Sep. 30, 2015 USD ($)	Feb. 03, 2014 USD ($)
Environmental remediation
ZAI PD Account Funding						$ 34.4
ZAI P D Account, Payment on Third Anniversary of Effective Date of Joint Plan					$ 30.0
Deferred payment obligations		$ 29.1	$ 28.2
ZAI P D Account, Maximum Number of Contingent Deferred Payments | payment		10
ZAI P D Account, Deferred Payments, Each Year for Twenty Years		$ 8.0
Period in Which ZAI PD Contingent Deferred Payments Will be Made		20 years
Minimum ZAI P D Account Assets for Condition in Relation to Contingent Obligation Payments		$ 10.0
Frequency of PD Trust Payments		6 months
Number of Shares Issuable under Warrant | shares		77,372,257
Gain from emergence from bankruptcy	$ 9.0
Estimated liability for environmental investigative and remediation costs		$ 55.6	61.7
Pre-tax charges for environmental matters		6.6	13.8	$ 8.2
Net cash expenditures		12.7	12.4	$ 14.0
Claim payments related to emergence from bankruptcy			76.5
Vermiculite Related Matters [Member]
Environmental remediation
Estimated liability for environmental investigative and remediation costs		$ 18.7	19.4
Maximum number of operating plants under U.S. Environmental Protection Agency (EPA) reinvestigation | facility		105
Non Vermiculite Related Matters [Member]
Environmental remediation
Estimated liability for environmental investigative and remediation costs		$ 36.9	$ 42.3