Business Acquisitions - Additional Information (Detail) - USD ($)						2 Months Ended	3 Months Ended			12 Months Ended
	Aug. 04, 2016	Apr. 13, 2016	Jan. 08, 2016	Nov. 04, 2014	May 29, 2014	Apr. 30, 2018	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jan. 31, 2018
Business Acquisition [Line Items]
Payment for business acquisitions, net of cash acquired										$ 45,162,000	$ 21,363,000	$ 130,809,000
Goodwill							$ 1,069,408,000			1,069,408,000	1,038,346,000	1,057,214,000
Increase in Goodwill										(59,000)	(135,000)
Net sale proceeds										17,242,000
Gain on divestiture										5,214,000
Atyati Technologies Private Limited
Business Acquisition [Line Items]
Net sale proceeds								$ 17,155,000
Net of selling expenses								427,000
Cash divested								854,000
Net revenues										14,958,000
Net profit (loss)										64,000
Gain on divestiture								$ 5,214,000
PNMSoft Ltd
Business Acquisition [Line Items]
Percentage of equity interest acquired	100.00%
Purchase consideration	$ 35,341,000
Payment for business acquisitions, net of cash acquired	28,128,000
Cash and cash equivalents	2,853,000
Increase (decrease) in purchase consideration							(155,000)
Additional reserve for doubtful receivables							136,000			136,000
Non-current liability							19,000			19,000
Deferred tax assets							25,000			25,000
Contingent earn-out consideration-Low end	0
Contingent earn-out consideration-High end	$ 9,000,000
Acquired intangible assets, weighted average amortization period	2 years
Goodwill	$ 25,101,000
Acquisition related cost	1,273,000
Acquired assets	7,110,000
Liabilities assumed	4,366,000
Recognized net deferred tax liability	944,000
PNMSoft Ltd | Customer-Related Intangible Assets
Business Acquisition [Line Items]
Intangible assets	1,700,000
PNMSoft Ltd | Marketing-Related Intangible Assets
Business Acquisition [Line Items]
Intangible assets	1,630,000
PNMSoft Ltd | Other Intangible Assets
Business Acquisition [Line Items]
Intangible assets	$ 5,110,000
Endeavour Software Technologies Private Limited
Business Acquisition [Line Items]
Payment for business acquisitions, net of cash acquired		$ 10,028,000
Cash and cash equivalents		2,345,000
Contingent earn-out consideration-Low end		0
Contingent earn-out consideration-High end		$ 3,500,000
Acquired intangible assets, weighted average amortization period		3 years
Goodwill		$ 8,870,000
Acquisition related cost		338,000
Acquired assets		5,691,000
Liabilities assumed		$ 1,853,000
Ownership percentage acquired		100.00%
Preliminary estimated purchase consideration		$ 14,443,000
Cash withheld for seller		95,000
Deferred tax liability		915,000
Endeavour Software Technologies Private Limited | Customer-Related Intangible Assets
Business Acquisition [Line Items]
Intangible assets		800,000
Endeavour Software Technologies Private Limited | Marketing-Related Intangible Assets
Business Acquisition [Line Items]
Intangible assets		900,000
Endeavour Software Technologies Private Limited | Other Intangible Assets
Business Acquisition [Line Items]
Intangible assets		$ 950,000
Strategic Sourcing Excellence LLC
Business Acquisition [Line Items]
Purchase consideration			$ 14,541,000
Increase (decrease) in purchase consideration							51,000
Contingent earn-out consideration-High end			$ 20,000,000
Acquired intangible assets, weighted average amortization period			5 years
Goodwill			$ 14,445,000
Acquisition related cost			164,000
Acquired assets			412,000
Liabilities assumed			$ 617,000
Ownership percentage acquired			51.00%
Cash consideration to acquired certain assets and assumed certain liabilities			$ 2,550,000
Increase in Goodwill, current assets							69,000			69,000
Increase in Goodwill, non-current asset							16,000			$ 16,000
Increase in Goodwill							$ 34,000
Strategic Sourcing Excellence LLC | If either the call or put option is exercised
Business Acquisition [Line Items]
Contingent earn-out consideration-High end			$ 9,800,000
Equity method investment ownership percentage			49.00%
Strategic Sourcing Excellence LLC | Call Option | Scenario, Forecast
Business Acquisition [Line Items]
Equity method investment ownership percentage													49.00%
Strategic Sourcing Excellence LLC | Selling Equityholders Put Option | Scenario, Forecast
Business Acquisition [Line Items]
Equity method investment ownership percentage						49.00%
Strategic Sourcing Excellence LLC | Selling Equityholders Put Option | Scenario, Forecast | Minimum
Business Acquisition [Line Items]
Selling equity holders put option exercise price						$ 2,450,000
Strategic Sourcing Excellence LLC | Selling Equityholders Put Option | Scenario, Forecast | Maximum
Business Acquisition [Line Items]
Selling equity holders put option exercise price						$ 2,950,000
Strategic Sourcing Excellence LLC | Customer-Related Intangible Assets
Business Acquisition [Line Items]
Intangible assets			$ 300,000
Japan Finance And Accounting Service Delivery
Business Acquisition [Line Items]
Payment for business acquisitions, net of cash acquired				$ 7,108,000
Contingent earn-out consideration-Low end				0
Contingent earn-out consideration-High end				15,750,000
Goodwill				16,791,000
Acquisition related cost				796,000
Liabilities assumed				80,000
Preliminary estimated purchase consideration				21,737,000
Increase in Goodwill, current assets											147,000
Cash and cash equivalents				3,491,000
Increase in Goodwill, pension assets											$ 96,000
Japan Finance And Accounting Service Delivery | Customer-Related Intangible Assets
Business Acquisition [Line Items]
Intangible assets				$ 7,522,000
Acquired intangible assets, weighted average amortization period				7 years
Deferred tax liability				$ 2,496,000
Pharmalink Consulting Inc
Business Acquisition [Line Items]
Percentage of equity interest acquired					100.00%
Payment for business acquisitions, net of cash acquired					$ 123,701,000
Increase (decrease) in purchase consideration									$ 168,000
Non-current liability												$ 585,000
Contingent earn-out consideration-Low end					0
Contingent earn-out consideration-High end					27,405,000
Intangible assets					$ 29,923,000
Acquired intangible assets, weighted average amortization period					6 years
Goodwill					$ 110,121,000
Preliminary estimated purchase consideration					138,799,000
Cash and cash equivalents					$ 2,200,000