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Income Tax - Additional Information (Detail) - USD ($) |  |  | 12 Months Ended
--- | --- | --- | ---
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% |  |  |

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