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Stock-based compensation - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Mar. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Closing stock price (in USD per share)	$ 29.05		$ 29.05
Service-based Vesting Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	$ 200,000	$ 500,000	$ 500,000	$ 1,100,000
Unrecognized stock-based compensation cost	1,000,000		$ 1,000,000
Unrecognized stock-based compensation cost, expected weighted-average period of recognition			1 year 8 months 12 days
Performance-based and Market-based Vesting Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation cost	$ 0	0	$ 0	0
Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested RSAs outstanding (in shares)	986,361		986,361
Restricted Stock Awards and Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	$ 4,900,000	$ 4,900,000	$ 8,900,000	$ 8,900,000
Unrecognized stock-based compensation cost, expected weighted-average period of recognition			2 years 3 months 18 days
Unvested RSAs outstanding (in shares)	2,515,734		2,515,734		2,289,615
Unrecognized stock-based compensation cost	$ 37,900,000		$ 37,900,000