Acquisitions - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions		6 Months Ended
	Nov. 01, 2017	Jun. 30, 2018	Dec. 31, 2017
Acquisitions
Goodwill		$ 1,448.0	$ 1,452.1
Accella Performance Materials
Acquisitions
Total cash consideration transferred		671.4
Cash and cash equivalents		16.5
Receivables		66.8
Inventories		47.5
Prepaid expenses and other current assets		0.9
Property, plant and equipment		59.6
Definite-lived intangible assets		240.0
Other long-term assets		15.6
Accounts payable		(45.5)
Income tax payable		2.0
Accrued expenses		(13.7)
Other long-term liabilities		(15.6)
Deferred income tax liabilities		(83.5)
Total identifiable net assets		290.6
Goodwill		380.8
Balances Without Adoption of ASC 606 | Accella Performance Materials
Acquisitions
Total cash consideration transferred	$ 670.7
Cash and cash equivalents	16.5
Receivables	66.8
Inventories	48.5
Prepaid expenses and other current assets	0.9
Property, plant and equipment	59.6
Definite-lived intangible assets	240.0
Other long-term assets	15.6
Accounts payable	(45.5)
Income tax payable	2.0
Accrued expenses	(23.2)
Other long-term liabilities	(15.6)
Deferred income tax liabilities	(83.5)
Total identifiable net assets	282.1
Goodwill	$ 388.6
Adjustment | Accella Performance Materials
Acquisitions
Total cash consideration transferred		0.7
Cash and cash equivalents		0.0
Receivables		0.0
Inventories		(1.0)
Prepaid expenses and other current assets		0.0
Property, plant and equipment		0.0
Definite-lived intangible assets		0.0
Other long-term assets		0.0
Accounts payable		0.0
Income tax payable		0.0
Accrued expenses		9.5
Other long-term liabilities		0.0
Deferred income tax liabilities		0.0
Total identifiable net assets		8.5
Goodwill		$ (7.8)