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Loss Per Share - Summary Of Calculation Of Basic And Diluted Loss Per Common Share (Detail)

v3.21.2
Loss Per Share - Summary Of Calculation Of Basic And Diluted Loss Per Common Share (Detail) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2019
Schedule Of Earnings Per Share Basic And Diluted [Line Items]      
Net loss attributable to Mirion Technologies (TopCo), Ltd. stockholders $ (158.3) $ (119.1) $ (122.0)
Weighted average common shares outstanding – basic and diluted 6.549 6.453 6.300
Loss per share attributable to Mirion Technologies (TopCo), Ltd. stockholders – basic and diluted $ (24.18) $ (18.45) $ (19.36)
Anti-dilutive employee share-based awards, excluded 0 0 0
Share-based Payment Arrangement, Option [Member]      
Schedule Of Earnings Per Share Basic And Diluted [Line Items]      
Anti-dilutive employee share-based awards, excluded 0.3 0.4 0.5