Business Combinations, Goodwill and Intangible Assets - Summary of Purchase Price Allocation for Acquisitions (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Oct. 22, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill	$ 186,770		$ 171,535	$ 139,599
Liss Systems Limited
Business Acquisition [Line Items]
Tangible assets	517
Tangible liabilities	(993)
Deferred tax liability	(643)
Goodwill	2,510
Total purchase price	5,111
Liss Systems Limited | Customer relationships
Business Acquisition [Line Items]
Identifiable intangible assets	1,918
Liss Systems Limited | Developed technology
Business Acquisition [Line Items]
Identifiable intangible assets	1,571
Liss Systems Limited | Trade names and trademarks
Business Acquisition [Line Items]
Identifiable intangible assets	231
IQR Consulting Inc.
Business Acquisition [Line Items]
Tangible assets	1,449
Tangible liabilities	(420)
Deferred tax liability	(836)
Goodwill	2,599
Total purchase price	5,092
IQR Consulting Inc. | Customer relationships
Business Acquisition [Line Items]
Identifiable intangible assets	$ 2,300
Datasource Consulting, LLC
Business Acquisition [Line Items]
Tangible assets		$ 3,582
Tangible liabilities		(1,503)
Goodwill		10,999
Total purchase price		20,318
Datasource Consulting, LLC | Customer relationships
Business Acquisition [Line Items]
Identifiable intangible assets		6,340
Datasource Consulting, LLC | Developed technology
Business Acquisition [Line Items]
Identifiable intangible assets		520
Datasource Consulting, LLC | Trade names and trademarks
Business Acquisition [Line Items]
Identifiable intangible assets		$ 380