Annual report pursuant to Section 13 and 15(d)

Income Taxes - Summary of Valuation Allowance (Details)

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Income Taxes - Summary of Valuation Allowance (Details) - USD ($)
$ in Millions
2 Months Ended 4 Months Ended 12 Months Ended
Dec. 31, 2021
Oct. 19, 2021
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2019
Income Tax Examination [Line Items]          
Valuation allowance $ 20.7 $ 30.7 $ 29.1 $ 29.0 $ 18.7
Increases/(decreases) resulting from the Mirion Business Combination 19.7 0.0 0.0 0.0  
Increases resulting from other business combinations 0.0 0.0 0.5 0.3  
Other increases 0.0 1.6 8.6 10.0  
Other decreases $ 0.0 0.0 $ (9.0) $ 0.0  
GSAH          
Income Tax Examination [Line Items]          
Valuation allowance   $ 1.0