Fair Value Measurements - Change in Level 3 Fair Values of Contingent Purchase Price Liability (Detail) - Level 3 [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ (33,368)
Ending balance	(24,817)	$ (33,368)
Contingent Purchase Price Liabilities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	(33,368)	(25,196)
Additions from business acquisitions	(8,522)	(19,353)
Payment of contingent purchase price payable	14,364	5,230
Change in fair value of contingency	2,709	5,951
Ending balance	$ (24,817)	$ (33,368)