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Financial Instruments - Additional Information (Detail) - USD ($) | 12 Months Ended |
--- | --- | ---
Mar. 31, 2019 | Mar. 31, 2018 | Mar. 31, 2017 | Apr. 01, 2018
Disclosure of detailed information about financial instruments [line items] |  |  |  |
Transfers between Level 1 and Level 2 fair value measurements, financial assets | $ 0 | $ 0 |  |
Transfers between Level 1 and Level 2 fair value measurements, financial liabilities | 0 | 0 |  |
Transfers between Level 2 and Level 1 fair value measurements, financial assets | 0 | 0 |  |
Transfers between Level 2 and Level 1 fair value measurements, financial liabilities | 0 | 0 |  |
Transfers into Level 3 fair value measurements, financial assets | 0 | 0 |  |
Transfers into Level 3 fair value measurements, financial liabilities | 0 | 0 |  |
Transfers out of Level 3 fair value measurements, financial assets | 0 | 0 |  |
Transfers out of Level 3 fair value measurements, financial liabilities | 0 | 0 |  |
Gain (loss) recognized due to discontinuation of cash flow hedge accounting | (2,000) | (20,000) | $ 666,000 |
Trade receivables | 73,872,000 | 71,388,000 |  | $ 71,462,000
Unbilled revenue | 66,752,000 | $ 61,721,000 |  | $ 61,721,000
Unused lines of credit | 74,274,000 |  |  |
Level 3 [member] |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |
Discount rate used to determine fair value of the contingent consideration liability |  | 2.50% |  |
Level 3 [member] | Non-recurring fair value measurement [member] |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |
Fair value measurement for Auto Claim BPM CGU | 38,492,000 |  |  |
Disposal cost | 656,000 |  |  |
Interest rate swap contracts [member] |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |
Outstanding swap agreement | $ 61,800,000 |  |  |
Currency risk [member] |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |
Rate of appreciation or depreciation of the foreign currencies against the functional currency of the company | 5.00% |  |  |
Effect on statement of profit before tax from operating activities due to appreciation or depreciation of the foreign currencies against the functional currency of the company | $ 3,152,000 |  |  |
Currency risk [member] | UK Pound Sterling [member] |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |
Rate of appreciation or depreciation of the foreign currencies against the functional currency of the company | 10.00% |  |  |
Effect on statement of profit before tax from operating activities due to appreciation or depreciation of the foreign currencies against the functional currency of the company | $ 23,451,000 |  |  |
Currency risk [member] | Indian Rupees [member] |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |
Rate of appreciation or depreciation of the foreign currencies against the functional currency of the company | 10.00% |  |  |
Effect on statement of profit before tax from operating activities due to appreciation or depreciation of the foreign currencies against the functional currency of the company | $ 30,976,000 |  |  |
Credit risk [member] |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |
Trade receivables | 73,872,000 | $ 71,388,000 |  |
Unbilled revenue | 66,752,000 | $ 61,721,000 |  |
Forward and option contracts [member] |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |
Gain (loss) on cash flow hedges, expected to be reclassified from other comprehensive income into profit (loss) | $ 5,578,000 |  |  |
Reclassification period for cash flow hedges | 24 months |  |  |
Interest rate swap contracts [member] |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |
Gain (loss) on cash flow hedges, expected to be reclassified from other comprehensive income into profit (loss) | $ 376,000 |  |  |
Reclassification period for cash flow hedges | 36 months |  |  |

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