Financial instruments - Fair values and risk management (Details) € in Millions	12 Months Ended
Mar. 31, 2021 EUR (€)
Disclosure of detailed information about financial instruments [line items]
Hedging instrument, fiscal year 2023	50
Commodity risk \| Maximum
Disclosure of detailed information about financial instruments [line items]
Hedging percentage	90.00%
EU-ETS Carbon Credits
Disclosure of detailed information about financial instruments [line items]
Hedging percentage, fiscal year 2022	100
Hedging instrument, fiscal year 2023	55
Financial instruments designated as hedging instruments, at fair value	€ 24

The fair value of financial instruments designated as hedging instruments. Hedging instruments are designated derivatives or (for a hedge of the risk of changes in foreign currency exchange rates only) designated non-derivative financial assets or non-derivative financial liabilities whose fair value or cash flows are expected to offset changes in the fair value or cash flows of a designated hedged item. [Refer: At fair value [member]; Derivatives [member]; Derivative financial assets; Derivative financial liabilities; Financial instruments, class [member]; Financial assets; Financial liabilities]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2021-01-01
-Name IFRS
-Number 7
-IssueDate 2020-01-01
-Paragraph 22
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2017-en-b&anchor=para_22_b&doctype=Standard&book=b
-URIDate 2020-01-01

Name:	ifrs-full_FinancialInstrumentsDesignatedAsHedgingInstrumentsAtFairValue
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant