Accounts Payable And Accrued Expenses (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Accounts Payble And Accrued Expenses [Line Items]
Payables, trade and other	$ 82.2	$ 67.6
Employment costs	18.6	18.0
Current portion of pension and postretirement benefit liabilities	10.9	11.6
Other	11.6	11.2
Total accounts payable and accrued expenses	383.3	$ 108.4
Knauf [Member]
Schedule Of Accounts Payble And Accrued Expenses [Line Items]
Advance receipt of Knauf proceeds	237.6
Payable to WAVE for advance receipt of Knauf proceeds	$ 22.4