Acquisitions (First Quarter 2016) - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Business Acquisition, Contingent Consideration [Line Items]
Contingent consideration, current	$ 14,382		$ 16,322
Contingent consideration, non-current	18,040		17,387
Goodwill	$ 489,039		$ 487,484
Millimaki Eggert L L P [Member]
Business Acquisition, Contingent Consideration [Line Items]
Acquired entity, name		Millimaki Eggert, L.L.P.
Consideration paid in cash		$ 1,100
Contingent consideration		1,200
Contingent consideration, current		500
Contingent consideration, non-current		700
Annual revenue		2,400
Effective date of acquisition	Jan. 01, 2016
Goodwill		$ 988