Accounts Payable And Accrued Expenses (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Schedule Of Accounts Payble And Accrued Expenses [Line Items]
Payables, trade and other	$ 76.0	$ 82.2
Current portion of lease liabilities	5.2
Employment costs	6.6	18.6
Current portion of pension and postretirement liabilities	11.1	10.9
Current portion of environmental liabilities	9.6	0.7
Other	22.4	10.9
Total accounts payable and accrued expenses	390.9	383.3
Knauf [Member]
Schedule Of Accounts Payble And Accrued Expenses [Line Items]
Advance receipt of Knauf proceeds	237.6	237.6
Payable to WAVE for advance receipt of Knauf proceeds	$ 22.4	$ 22.4