Post-effective amendment to a registration statement that is not immediately effective upon filing

Business Combinations and Acquisitions - Narrative (Details)

v3.22.0.1
Business Combinations and Acquisitions - Narrative (Details) - USD ($)
$ / shares in Units, $ in Millions
1 Months Ended 2 Months Ended 4 Months Ended 12 Months Ended
Oct. 20, 2021
Feb. 28, 2021
Dec. 31, 2021
Oct. 19, 2021
Jun. 30, 2021
Jun. 30, 2020
Business Combination, Separately Recognized Transactions [Line Items]            
Payments to acquire businesses gross $ 1,300.0          
Statutory income tax rate (as a percent)     21.00%     25.00%
Intermediate Co            
Business Combination, Separately Recognized Transactions [Line Items]            
Payments to acquire businesses gross $ 1,300.0          
Business acquisition share price (in dollars per share) $ 10.00          
Mirion TopCo            
Business Combination, Separately Recognized Transactions [Line Items]            
Pro forma adjustments     $ 2.2 $ 26.2    
Mirion TopCo | Fair Value Adjustment to Inventory            
Business Combination, Separately Recognized Transactions [Line Items]            
Pro forma adjustments     15.8 15.8 $ 15.8  
Mirion TopCo | Acquisition-related Costs            
Business Combination, Separately Recognized Transactions [Line Items]            
Pro forma adjustments     28.4 $ 28.4 28.4  
CIRS | Medical            
Business Combination, Separately Recognized Transactions [Line Items]            
Transaction expenses     $ 0.4      
SNC | Medical            
Business Combination, Separately Recognized Transactions [Line Items]            
Payments to acquire businesses gross   $ 261.9        
Transaction expenses         1.2  
Biodex and SNC | Fair Value Adjustment to Inventory            
Business Combination, Separately Recognized Transactions [Line Items]            
Pro forma adjustments         5.2 $ 5.2
Biodex and SNC | Acquisition-related Costs            
Business Combination, Separately Recognized Transactions [Line Items]            
Pro forma adjustments         4.8 4.8
Biodex and SNC | Reduction In Revenues Due To The Elimination Of Deferred Contract Revenue            
Business Combination, Separately Recognized Transactions [Line Items]            
Pro forma adjustments         $ 14.8 $ 14.8
Class A Common Stock | Intermediate Co            
Business Combination, Separately Recognized Transactions [Line Items]            
Business acquisition equity interest issued or issuable (in shares) 30,401,902          
Class B Common Stock | Intermediate Co            
Business Combination, Separately Recognized Transactions [Line Items]            
Business acquisition equity interest issued or issuable (in shares) 8,560,540