Income taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2020
Operating Loss Carryforwards [Line Items]
Valuation allowance on tax losses that will not be realized	$ 0.6	$ 0.5
Cumulative tax losses	2.5	2.0
Decrease in valuation allowance resulting from recognition of previously unrecognized tax losses		0.3
Increase in valuation allowance resulting from an increase in deferred tax assets not recognized on current year tax losses	0.3
Net tax loss carryforwards	5.1	$ 11.7
Thailand
Operating Loss Carryforwards [Line Items]
Tax losses subject to expiration	$ 0.3
Weighted Average
Operating Loss Carryforwards [Line Items]
Tax rate	33.10%	15.30%	47.20%