Commitments and Contingent Liabilities - Asbestos-Related Liabilities (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($) payment shares	Dec. 31, 2017 USD ($)	Feb. 03, 2017 USD ($)	Feb. 03, 2014 USD ($)
Other Commitments Chapter 11 [Abstract]
ZAI PD account funding			$ 30.0	$ 34.4
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
Estimated annual expenses related to PD Trust	$ 0.2
Number of shares issuable under warrant (in shares) | shares	77,372,257
Environmental remediation
Estimated liability for environmental investigative and remediation costs	$ 61.2	$ 70.3
Vermiculite Related Matters
Environmental remediation
Estimated liability for environmental investigative and remediation costs	18.1	25.8
Non-Vermiculite Related Matters
Environmental remediation
Estimated liability for environmental investigative and remediation costs	$ 43.1	$ 44.5