Acquisitions - Identifiable Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Aug. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill (Note 5)	$ 198,233		$ 68,969
Interface
Business Acquisition [Line Items]
Accounts receivable		$ 25,182
Inventories		17,313
Prepaid expenses and other current assets		2,382
Property, plant and equipment		40,902
Goodwill (Note 5)		130,462
Other intangible assets (Note 5)		107,800
Other assets		308
Total assets acquired, net of cash acquired		324,349
Current liabilities		(11,319)
Deferred tax liabilities		(25,275)
Benefit plan liabilities		(18,352)
Other long-term liabilities		(1,031)
Total liabilities assumed		(55,977)
Total purchase price, net of cash acquired		$ 268,372