Stock-based compensation plan - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 1,325	$ 1,273	$ 660
Deferred tax benefit recognized	(100)	100	400
Tax benefits realized on awards exercised	$ 600	$ 100	$ 200
LTIP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares reserved for future issuance (in shares)	34,965,000

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

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Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

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Amount of tax benefit from exercise of option under share-based payment arrangement.

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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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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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