Acquisitions - Summary of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Oct. 03, 2016	Dec. 31, 2015
Assets:
Goodwill	$ 25,118	$ 25,308		$ 11,265
Tebras And PBC [Member]
Assets:
Current assets			$ 5,165
Property, plant and equipment			5,716
Identifiable intangible assets			7,354
Goodwill			14,207
Total assets acquired			32,442
Liabilities:
Current liabilities			408
Deferred tax liability			3,079
Total liabilities assumed			3,487
Net assets acquired			$ 28,955