Acquisitions - Fair Values of Identifiable Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Aug. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill (Note 6)	$ 196,963		$ 68,969	$ 63,606
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 6)		130,991
Other intangible assets (Note 6)		106,900
Other assets		308
Total assets acquired, net of cash acquired		323,978
Current liabilities		(11,319)
Deferred tax liabilities (Note 14)		(24,904)
Benefit plan liabilities (Note 10)		(18,352)
Other long-term liabilities		(1,031)
Total liabilities assumed		(55,606)
Total purchase price, net of cash acquired		$ 268,372