Summary of significant accounting policies - Schedule of Useful Lives by Major Asset Class (Details)	12 Months Ended
	Mar. 31, 2020
Machinery, equipment and software | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years
Machinery, equipment and software | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years
Furniture and fixtures | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	2 years
Furniture and fixtures | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years
Store fixtures | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	2 years
Store fixtures | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years