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Group information - Additional Information (Detail)
 12 Months Ended
Mar. 30, 2021
Dec. 31, 2020
Disclosure of non-adjusting events after reporting period [line items]    
Date of end of reporting period   Dec. 31, 2020
Authorization Of Financial Statements [Member]    
Disclosure of non-adjusting events after reporting period [line items]    
Date of authorisation for issue of financial statements Mar. 30, 2021