Commitments and Contingent Liabilities (Details)	3 Months Ended			6 Months Ended	12 Months Ended	36 Months Ended	77 Months Ended
	Jun. 30, 2020 USD ($) shares	Dec. 31, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2020 USD ($) payment shares	Dec. 31, 2019 USD ($)	Feb. 03, 2017 USD ($)	Jun. 30, 2020 USD ($) shares
Other Commitments [Abstract]
ZAI PD account funding						$ 49,400,000
ZAI P D account, maximum number of contingent deferred payments | payment				10
ZAI P D account, deferred payments, each year for twenty years				$ 8,000,000
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	$ 10,000,000			$ 10,000,000			$ 10,000,000
ZAI PD Claims and Expenses paid by the Trust							34,000,000
ZAI PD Attorney's fees paid by the Trust						$ 15,000,000
ZAI PD Trust Balance	$ 20,000,000			$ 20,000,000			$ 20,000,000
Frequency of PD trust payments				6 months
Estimated annual expenses related to PD Trust				$ 200,000
Number of shares issuable under warrant (in shares) | shares	77,372,257			77,372,257			77,372,257
Period within which contingent funding obligations are reasonably estimable				5 years
Period Covered by Reserve for Loss Contingency				5 years
Legacy Matters
Accrual for Environmental Loss Contingencies	$ 111,800,000	$ 115,300,000		$ 111,800,000	$ 115,300,000		$ 111,800,000
Legacy Product Charge		24,000,000.0
Remaining Period in Which ZAI PD Contingent Deferred Payments May be Made				19 years
Total Maximum Financial Obligation for ZAI PD Account Contingent Deferred Payments				$ 80,000,000.0
Maximum Annual Obligation for ZAI PD Account Contingent Deferred Payments				8,000,000.0
Non-Vermiculite Related Matters
Legacy Matters
Accrual for Environmental Loss Contingencies	38,800,000	39,300,000		38,800,000	39,300,000		38,800,000
Vermiculite Related Matters
Legacy Matters
Accrual for Environmental Loss Contingencies	73,000,000.0	$ 76,000,000.0		73,000,000.0	76,000,000.0		73,000,000.0
Operable Unit 3 [Member]
Legacy Matters
Environmental Remediation Expense			$ 70,000,000.0
Spillway [Member]
Legacy Matters
Loss Contingency, Loss in Period					$ 68,000,000.0
Minimum | Operable Unit 3 [Member]
Legacy Matters
Loss Contingency, Estimate of Possible Loss	30,000,000			30,000,000			30,000,000
Minimum | Spillway [Member]
Legacy Matters
Loss Contingency, Estimate of Possible Loss	$ 50,000,000			50,000,000			50,000,000
Site Contingency, Time Frame of Disbursements	three years
Maximum | Operable Unit 3 [Member]
Legacy Matters
Loss Contingency, Estimate of Possible Loss	$ 170,000,000			170,000,000			170,000,000
Maximum | Spillway [Member]
Legacy Matters
Loss Contingency, Estimate of Possible Loss	$ 100,000,000			100,000,000			100,000,000
Site Contingency, Time Frame of Disbursements	P4Y
ZAI PD Trust [Member] | Minimum
Legacy Matters
Loss Contingency, Estimate of Possible Loss	$ 16,000,000			16,000,000			16,000,000
ZAI PD Trust [Member] | Maximum
Legacy Matters
Loss Contingency, Estimate of Possible Loss	$ 24,000,000			$ 24,000,000			$ 24,000,000