Annual report pursuant to Section 13 and 15(d)

Goodwill and Intangible Assets - Schedule of Goodwill (Details)

v3.22.0.1
Goodwill and Intangible Assets - Schedule of Goodwill (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
Oct. 20, 2021
Jun. 30, 2019
Goodwill [Roll Forward]            
Goodwill, beginning balance $ 1,662.6 $ 677.4 $ 681.5 $ 522.6 $ 0.0 $ 511.6
Translation adjustment (13.7) (5.0) 16.0 (6.1)    
Goodwill, ending balance 1,662.6 677.4 681.5 522.6    
Capintec            
Goodwill [Roll Forward]            
Goodwill acquired during period       6.0    
Premium Analyse            
Goodwill [Roll Forward]            
Goodwill acquired during period       4.3    
Selmic            
Goodwill [Roll Forward]            
Goodwill acquired during period       2.7    
AWST            
Goodwill [Roll Forward]            
Goodwill acquired during period       4.1    
SNC            
Goodwill [Roll Forward]            
Goodwill acquired during period     130.2      
Biodex            
Goodwill [Roll Forward]            
Goodwill acquired during period     11.1      
Dosimetrics            
Goodwill [Roll Forward]            
Goodwill acquired during period     1.6      
Dosimetry Badge            
Goodwill [Roll Forward]            
Goodwill acquired during period   0.9        
Mirion TopCo            
Goodwill [Roll Forward]            
Goodwill, beginning balance         1,639.0  
Goodwill acquired during period 1,639.0          
CHP            
Goodwill [Roll Forward]            
Goodwill acquired during period 1.5          
Safeline            
Goodwill [Roll Forward]            
Goodwill acquired during period 0.8          
CIRS            
Goodwill [Roll Forward]            
Goodwill acquired during period 35.0          
Medical            
Goodwill [Roll Forward]            
Goodwill, beginning balance 712.5 250.0 249.5 106.8 0.0 96.7
Translation adjustment 0.0 (0.4) (0.2) 0.0    
Goodwill, ending balance 712.5 250.0 249.5 106.8    
Medical | Capintec            
Goodwill [Roll Forward]            
Goodwill acquired during period       6.0    
Medical | Premium Analyse            
Goodwill [Roll Forward]            
Goodwill acquired during period       0.0    
Medical | Selmic            
Goodwill [Roll Forward]            
Goodwill acquired during period       0.0    
Medical | AWST            
Goodwill [Roll Forward]            
Goodwill acquired during period       4.1    
Medical | SNC            
Goodwill [Roll Forward]            
Goodwill acquired during period     130.2      
Medical | Biodex            
Goodwill [Roll Forward]            
Goodwill acquired during period     11.1      
Medical | Dosimetrics            
Goodwill [Roll Forward]            
Goodwill acquired during period     1.6      
Medical | Dosimetry Badge            
Goodwill [Roll Forward]            
Goodwill acquired during period   0.9        
Medical | Mirion TopCo            
Goodwill [Roll Forward]            
Goodwill acquired during period 675.2          
Medical | CHP            
Goodwill [Roll Forward]            
Goodwill acquired during period 1.5          
Medical | Safeline            
Goodwill [Roll Forward]            
Goodwill acquired during period 0.8          
Medical | CIRS            
Goodwill [Roll Forward]            
Goodwill acquired during period 35.0          
Industrial            
Goodwill [Roll Forward]            
Goodwill, beginning balance 950.1 427.4 432.0 415.8 $ 0.0 $ 414.9
Translation adjustment (13.7) (4.6) 16.2 (6.1)    
Goodwill, ending balance 950.1 427.4 432.0 415.8    
Industrial | Capintec            
Goodwill [Roll Forward]            
Goodwill acquired during period       0.0    
Industrial | Premium Analyse            
Goodwill [Roll Forward]            
Goodwill acquired during period       4.3    
Industrial | Selmic            
Goodwill [Roll Forward]            
Goodwill acquired during period       2.7    
Industrial | AWST            
Goodwill [Roll Forward]            
Goodwill acquired during period       $ 0.0    
Industrial | SNC            
Goodwill [Roll Forward]            
Goodwill acquired during period     0.0      
Industrial | Biodex            
Goodwill [Roll Forward]            
Goodwill acquired during period     0.0      
Industrial | Dosimetrics            
Goodwill [Roll Forward]            
Goodwill acquired during period     $ 0.0      
Industrial | Dosimetry Badge            
Goodwill [Roll Forward]            
Goodwill acquired during period   $ 0.0        
Industrial | Mirion TopCo            
Goodwill [Roll Forward]            
Goodwill acquired during period 963.8          
Industrial | CHP            
Goodwill [Roll Forward]            
Goodwill acquired during period 0.0          
Industrial | Safeline            
Goodwill [Roll Forward]            
Goodwill acquired during period 0.0          
Industrial | CIRS            
Goodwill [Roll Forward]            
Goodwill acquired during period $ 0.0