Business Acquisitions - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Business Combinations [Abstract]
Cash consideration for acquisition	$ 183,000	$ 123,000
Contingent consideration period	2 years
Earnout contingent consideration paid for business acquisition	$ 8,000
Contingent consideration included as part of fair value of assets and liabilities as on acquisition date	6,375
Aggregate contingent consideration outstanding for acquisition	6,000
Estimated fair value of earnout liabilities	$ 1,000