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Income Tax - Additional Information (Detail) - USD ($)			12 Months Ended
Income Tax - Additional Information (Detail) - USD ($)	Apr. 01, 2018	Mar. 21, 2009	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2015
Disclosure of income taxes [Line Items]
Provision for income taxes			$ 25,719,000	$ 15,431,000	$ 17,530,000
Corporate tax rate				0.00%
Deferred tax liability derecognized	$ 11,816,000		10,706,000	$ 11,812,000
Provision for income taxes			$ 15,743,000	$ 9,368,000	$ 5,171,000
Decrease in basic earnings loss per share			$ 0.31	$ 0.19	$ 0.10
Decrease in diluted earnings loss per share			$ 0.30	$ 0.18	$ 0.10
Unused tax losses for which no deferred tax asset recognized			$ 18,270,000
Temporary difference on which deferred tax liability has not been recognized amounts			617,038,000	$ 494,571,000	$ 401,857,000
Income tax reserve			11,658,000	12,370,000
Deposit of disputed amounts with tax authorities			12,644,000	13,416,000
Payment of service tax and related penalty		$ 5,034,000
Value Edge Research Services Private Limited [member]
Disclosure of income taxes [Line Items]
Deferred tax liability derecognized				1,686,000
Legal proceedings contingent liability [member]
Disclosure of income taxes [Line Items]
Estimated amount of additional taxes			55,135,000	45,002,000
Estimated amount of additional taxes, interest			$ 18,413,000	13,897,000
Domestic [member]
Disclosure of income taxes [Line Items]
Provision for income taxes				$ 0
Pune Mumbai and Chennai in India [member] \| 2017 - 2026 [member]
Disclosure of income taxes [Line Items]
Percentage of income tax exemption					50.00%
New Pune and Gurgaon in India [member] \| Until 2019 [member]
Disclosure of income taxes [Line Items]
Percentage of income tax exemption						100.00%
New Pune and Gurgaon in India [member] \| 2020 - 2029 [member]
Disclosure of income taxes [Line Items]
Percentage of income tax exemption						50.00%
New Pune and Gurgaon in India [member] \| Until 2022 [member]
Disclosure of income taxes [Line Items]
Percentage of income tax exemption				100.00%
New Pune and Gurgaon in India [member] \| 2023 - 2032 [member]
Disclosure of income taxes [Line Items]
Percentage of income tax exemption				50.00%
India [member]
Disclosure of income taxes [Line Items]
Percentage of minimum alternative tax			21.55%
Estimated amount of additional taxes			$ 31,796,000	$ 43,583,000
Estimated amount of additional taxes, interest			$ 10,926,000	$ 17,234,000
Costa Rica [Member] \| 2018 - 2021 [member]
Disclosure of income taxes [Line Items]
Percentage of income tax exemption			50.00%
Sri Lanka [member] \| Changes in tax rates or tax laws enacted or announced [member]
Disclosure of income taxes [Line Items]
Corporate tax rate	14.00%
New Noida and Pune India [member] \| Until 2023 [member]
Disclosure of income taxes [Line Items]
Percentage of income tax exemption			100.00%
New Noida and Pune India [member] \| 2024 - 2023 [member]
Disclosure of income taxes [Line Items]
Percentage of income tax exemption			50.00%
USA [Member
Disclosure of income taxes [Line Items]
Corporate tax rate					35.00%
USA [Member \| Changes in tax rates or tax laws enacted or announced [member]
Disclosure of income taxes [Line Items]
Corporate tax rate				21.00%
Tax effect from change in tax rate			$ 414,000	$ (5,212,000)
Reduction in effective tax rate			0.30%