Goodwill and Intangible Assets - Other Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule Of Finite And Indefinite Lived Intangible Assets [Line Items]
Total intangible assets, accumulated amortization	$ 84,236	$ 78,330
Total intangible assets, cost	232,625	237,943
Total intangible assets, net	148,389	159,613
Customer Relationships [Member]
Schedule Of Finite And Indefinite Lived Intangible Assets [Line Items]
Intangible assets subject to amortization, cost	172,966	177,207
Total intangible assets, accumulated amortization	78,880	72,970
Intangible assets subject to amortization, net	94,086	104,237
Product Technology and Patents [Member]
Schedule Of Finite And Indefinite Lived Intangible Assets [Line Items]
Intangible assets subject to amortization, cost	6,039	5,853
Total intangible assets, accumulated amortization	5,356	5,360
Intangible assets subject to amortization, net	683	493
Tradenames and Trademarks [Member]
Schedule Of Finite And Indefinite Lived Intangible Assets [Line Items]
Intangible assets not subject to amortization, cost	$ 53,620	$ 54,883