Business Combinations, Goodwill and Intangible Assets - Summary of Purchase Price Allocation for Acquisition (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill	$ 187,952	$ 186,770	$ 171,535
Datasource Consulting, LLC
Business Acquisition [Line Items]
Tangible assets	3,582
Tangible liabilities	(1,503)
Goodwill	10,999
Total purchase price	20,318
Customer relationships | Datasource Consulting, LLC
Business Acquisition [Line Items]
Identifiable intangible assets	6,340
Developed technology | Datasource Consulting, LLC
Business Acquisition [Line Items]
Identifiable intangible assets	520
Trade names and trademarks | Datasource Consulting, LLC
Business Acquisition [Line Items]
Identifiable intangible assets	$ 380