Goodwill and Other Intangible Assets - Narrative (Details) - USD ($)		9 Months Ended
	Aug. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Additional goodwill acquired		$ 130,980,000
Gross intangible assets		159,084,000	$ 51,992,000
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Gross intangible assets		143,651,000	39,474,000
Trade Names
Finite-Lived Intangible Assets [Line Items]
Gross intangible assets		7,368,000	$ 4,288,000
Interface
Finite-Lived Intangible Assets [Line Items]
Goodwill expected to be deductible for income tax purposes		0
Gross intangible assets	$ 107,800,000
Interface | Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Gross intangible assets	$ 104,600,000
Weighted-average useful life of acquired intangible assets	13 years
Interface | Trade Names
Finite-Lived Intangible Assets [Line Items]
Gross intangible assets	$ 3,200,000
Weighted-average useful life of acquired intangible assets	3 years
Performance Materials
Finite-Lived Intangible Assets [Line Items]
Additional goodwill acquired		130,980,000
Performance Materials | Interface
Finite-Lived Intangible Assets [Line Items]
Additional goodwill acquired		$ 130,500,000