Acquisitions (First Quarter 2018) - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Business Acquisition, Contingent Consideration [Line Items]
Contingent consideration, current	$ 16,293	$ 15,151
Contingent consideration, non-current	$ 28,331	$ 22,423
Laurus Transaction Advisors, LLC [Member]
Business Acquisition, Contingent Consideration [Line Items]
Effective date of acquisition	Feb. 01, 2018
Acquired entity, name	Laurus Transaction Advisors, LLC
Consideration paid in cash	$ 15,500
Contingent consideration	8,300
Contingent consideration, current	2,200
Contingent consideration, non-current	6,100
Annual revenue	$ 5,600