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Stock Based Compensation - Narrative (Details)
$ in Millions
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2024
USD ($)
shares
Sep. 30, 2023
USD ($)
Sep. 30, 2024
USD ($)
shares
Sep. 30, 2023
USD ($)
shares
Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Stock based compensation expense $ 2.3 $ 1.5 $ 12.7 $ 10.1  
Employee Stock Option          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Stock based compensation expense 0.2 0.3 $ 0.5 $ 0.9  
Award vesting period         3 years
Award expiration period         10 years
Share Units          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Award vesting period     3 years    
Number of units granted (in shares) | shares     195,363 168,688  
Value of units share units granted     $ 16.1 $ 11.3  
Share based compensation expense attributable to share units 1.7 1.1 10.9 8.7  
Performance Shares          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Stock based compensation expense $ 0.4 $ 0.2 $ 1.3 $ 0.5  
Award vesting period     3 years    
Number of units granted (in shares) | shares     29,475 24,580  
Value of units share units granted     $ 2.4 $ 1.7  
Performance Shares | Minimum          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Potential payouts range 0   0    
Performance Shares | Maximum          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Potential payouts range 1.50   1.50    
A.O. Smith Combined Compensation Plan          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of shares available for granting of options or share units (in shares) | shares 2,289,392   2,289,392