Basis of Financial Statement Presentation - Narrative (Details) - USD ($) $ in Thousands			3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 12, 2018	Jan. 01, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2017
New Accounting Pronouncement, Early Adoption [Line Items]
Business acquisitions, net of cash acquired					$ 269,972	$ 335
Effect on revenue			$ 197,886	$ 180,041	575,959	520,407
Effect on retained earnings		$ 376,381	404,141		404,141			$ 374,783
Cost of sales			162,747	139,987	465,186	396,528
Selling, product development and administrative expenses			25,406	24,700	74,755	73,339
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
New Accounting Pronouncement, Early Adoption [Line Items]
Effect on revenue		19,600	(1,063)		6,799
Effect on retained earnings		1,598	2,652		2,652
Cost of sales			(2,046)		5,458
Selling, product development and administrative expenses			0		$ 0
Accounting Standards Update 2017-07
New Accounting Pronouncement, Early Adoption [Line Items]
Cost of sales				100		200
Selling, product development and administrative expenses				$ 100		$ 400
Thermal Acoustical Solutions | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
New Accounting Pronouncement, Early Adoption [Line Items]
Effect on revenue		$ 16,300	$ (1,100)
Precision Filtration Division of Precision Custom Coatings
New Accounting Pronouncement, Early Adoption [Line Items]
Payments to acquire business	$ 1,600
Possible additional cash payments (less than)	$ 2,000
Interface
New Accounting Pronouncement, Early Adoption [Line Items]
Business acquisitions, net of cash acquired							$ 268,400
Cash acquired from acquisition							$ 5,200