Significant accounting policies - Intangible Assets (Details)	12 Months Ended
	Mar. 31, 2021
Trademarks
Disclosure of detailed information about intangible assets [line items]
Useful life measured as period of time, intangible assets other than goodwill	20 years
Minimum | Customer relationships
Disclosure of detailed information about intangible assets [line items]
Useful life measured as period of time, intangible assets other than goodwill	9 years
Minimum | Software
Disclosure of detailed information about intangible assets [line items]
Useful life measured as period of time, intangible assets other than goodwill	3 years
Maximum | Customer relationships
Disclosure of detailed information about intangible assets [line items]
Useful life measured as period of time, intangible assets other than goodwill	20 years 6 months
Maximum | Software
Disclosure of detailed information about intangible assets [line items]
Useful life measured as period of time, intangible assets other than goodwill	5 years