Purchase Price Allocated Based on Fair Value of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	May 29, 2014
Recognized amounts of identifiable assets acquired and liabilities assumed
Goodwill	$ 1,069,408	$ 1,038,346	$ 1,057,214
Pharmalink Consulting Inc
Business Acquisition [Line Items]
Purchase price				$ 138,799
Acquisition-related costs included in selling, general and administrative expenses as incurred				1,977
Recognized amounts of identifiable assets acquired and liabilities assumed
Net assets acquired				7,174
Intangible assets				29,923
Deferred tax asset (liability), net				(8,419)
Total identifiable net assets acquired				28,678
Goodwill				110,121
Total estimated purchase consideration				$ 138,799