Acquisition and Discontinued Operations (Summary of Total Depreciation and Amortization, Capital Expenditures and Estimated Losses) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Gain (loss) on disposal of discontinued business	$ 2.2	$ (17.7)
EMEA and Pacific Rim Business [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Gain (loss) on disposal of discontinued business	2.2	(17.7)
Purchases of property, plant and equipment	(0.4)	(1.2)
Operating lease cost	2.3
ROU assets obtained in exchange for lease obligations	24.6
EMEA and Pacific Rim Business [Member] | Knauf [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Gain (loss) on disposal of discontinued business	$ (2.2)	$ 17.7