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Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
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	(20,000)	$ 666,000	$ 125,000
Unused lines of credit	78,290,000
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	$ 89,900,000
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	$ 3,751,000
Currency risk [member] | United Kingdom 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	$ 24,107,000
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	$ 27,282,000
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)	$ 1,015,000
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)	$ 995,000
Reclassification period for cash flow hedges	48 months

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