Segment information - Reconciliation of Segment Results to Income Before Tax (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting [Abstract]
Segment Adjusted EBITDA	$ 53,298	$ 52,472	$ 43,021
Corporate and consolidation entries	(8,366)	(8,631)	(9,018)
Loss contingency	(233)	15	17
Expected credit losses	0	64	0
Operating lease costs	(1,610)	(988)	0
Product development costs	(1,363)	(1,449)	(1,162)
Depreciation and amortization	(19,972)	(16,368)	(15,524)
Impairment of long-lived assets	(6)	(62)	(199)
Stock-based compensation costs	(660)	(511)	(797)
Decrease/(increase) in restructuring costs	1	(221)	57
Net profit on sale of property and equipment	270	43	98
Net foreign exchange (losses)/gains	(610)	28	(390)
Net interest income	67	233	385
Income before income tax expense	$ 20,816	24,625	$ 16,488
Middle East and Australia
Segment Reporting Information [Line Items]
Restructuring costs		100
Africa
Segment Reporting Information [Line Items]
Restructuring costs		$ 100