Acquisitions (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) company	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Goodwill	$ 217,722	$ 251,868	$ 217,094
Series of Business Acquisitions
Business Acquisition [Line Items]
Number of companies acquired | company		3
Aggregate purchase price		$ 40,000
Goodwill		$ 20,000
Purchase adjustment due to remeasurement of assumed liabilities related to acquisitions	$ 5,300