Repurchase of common stock - Narrative (Details) - USD ($)	12 Months Ended
	Mar. 31, 2020	May 08, 2019
Equity [Abstract]
Amount authorized under share repurchase program		$ 25,000,000
Total shares repurchased (in shares)	564,468
Stock repurchased during period	$ 7,904,000
Average price per share (in USD per share)	$ 14.03
Remaining authorized repurchase amount	$ 17,100,000