Stock-based compensation - Classification of expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Share-Based Compensation
Stock-based compensation expense	$ 8,650	$ 9,114	$ 18,125	$ 17,961
Stock options
Share-Based Compensation
Stock-based compensation expense	4,894	5,688	10,627	11,302
Restricted and performance stock units
Share-Based Compensation
Stock-based compensation expense	3,756	3,426	7,498	6,659
Research and development
Share-Based Compensation
Stock-based compensation expense	4,078	4,447	8,304	7,745
Selling, general and administrative
Share-Based Compensation
Stock-based compensation expense	$ 4,572	$ 4,667	$ 9,821	$ 10,216