Earnings per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Basic earnings per share
Net income attributable to ordinary shareholders	$ 1,299	$ 3,452	$ 4,830	$ 5,874
Weighted average number of ordinary shares in issue (in shares)	552,386	548,008	552,124	547,569
Basic earnings per share (in dollars per share)	$ 0.002	$ 0.01	$ 0.01	$ 0.01
Weighted average number of American Depository Shares in issue (in shares)	22,095	21,920	22,085	21,903
Basic earnings per American Depository Share (in dollars per share)	$ 0.06	$ 0.16	$ 0.22	$ 0.27
Diluted earnings per share
Diluted weighted average number of ordinary shares in issue (in shares)	565,622	558,951	565,322	558,829
Diluted earnings per share (in dollars per share)	$ 0.002	$ 0.01	$ 0.01	$ 0.01
Diluted weighted average number of American Depository Shares in issue (in shares)	22,625	22,358	22,613	22,353
Diluted earnings per American Depository Share (in dollars per share)	$ 0.06	$ 0.15	$ 0.21	$ 0.26
Stock Appreciation Rights
Diluted earnings per share
Potentially dilutive effect of share-based payment arrangements (in shares)	11,778	9,339	11,809	9,517
Restricted Share Units
Diluted earnings per share
Potentially dilutive effect of share-based payment arrangements (in shares)	1,458	599	1,389	618
Stock Options
Diluted earnings per share
Potentially dilutive effect of share-based payment arrangements (in shares)	0	1,005	0	1,125