Fair value of common stock per share.

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Increase in number of common shares reserved for future issuance.

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Number of shares upon each option exercised.

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Percentage of automatic increase in ordinary shares.

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Risk free rate description.

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- Definition

Sharebased compensation arrangement by sharebased payment award options grants in period fair value.

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- Definition

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Aggregate number of common shares reserved for future issuance.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Number of equity instruments other than options outstanding, including both vested and non-vested instruments.

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Number of shares authorized for issuance under share-based payment arrangement.

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Gross number of share options (or share units) granted during the period.

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Description of modification of award under share-based payment arrangement. Includes, but is not limited to, terms for expiration date, vesting rights and exercise price.

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Weighted average remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted average remaining contractual term of outstanding stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Share-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019	Oct. 29, 2020	Oct. 31, 2018	Oct. 28, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	$ 4,984	$ 4,467	$ 4,957
Number of Options Granted	258,026	110,623	189,552
Total fair value of stock options granted	$ 889	$ 588	$ 676
Risk-free interest rate, Description	Risk-Free Interest Rate. The risk-free interest rate is based on the UK Government 10 year bond yield curve in effect at the time of grant prior to the initial public offering and 10 year U.S. Treasury Stock for awards from April 2014 onwards.
Total compensation cost not yet recognized related to share options and RSUs	$ 4,608
Total compensation cost not yet recognized related to share options, RSUs, weighted average remaining amortization period	18 months
Ordinary Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair value of ordinary shares per share	$ 3.68
Restricted Stock Units (RSUs) [Member] \| Time Based Vesting [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of restricted stock units outstanding	783,759
Weighted average remaining vesting period	10 months
Restricted Stock Units (RSUs) [Member] \| Milestone Vesting [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of restricted stock units outstanding	118,650
Employee Stock Option [Member] \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	1 year
Employee Stock Option [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	3 years
2012 Option Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares upon each option exercised	1
Maximum number of shares authorized for grant	839,509
Vesting period	3 years
Contractual life	10 years
Options exercisable percentage description	Options were not exercisable before the Company became a public company and all outstanding options become exercisable in the event of an acquisition of 75% or more of the share capital of the Company by a third party. No further awards will be granted under the 2012 Option Plan.
Number of Options Granted	0
2014 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Ordinary shares reserved for issuance	1,500,000
Percentage of automatic increase in ordinary shares	0.75%
Increase in number of shares reserved for future issuance				750,000	550,000	750,000