Goodwill and Other Intangible Assets - Schedule of Changes in Carrying Amount of Goodwill (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Beginning balance	$ 584,634	$ 530,845
Acquisitions	111,852	57,619
Divestitures	(40,963)
Ending balance	$ 655,523	$ 588,464