v3.25.2
Fair Value of Marketable Securities (Detail) - USD ($)
$ in Millions
Jun. 30, 2025
Dec. 31, 2024
Jun. 30, 2024
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Trading Securities $ 6.1 $ 6.3 $ 5.8
Deferred Compensation Plan [Member]      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Trading Securities 2.9 2.2 1.9
Fair Value, Inputs, Level 1      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Trading Securities 6.1 6.3 5.8
Fair Value, Inputs, Level 1 | Deferred Compensation Plan [Member]      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Trading Securities 2.9 2.2 1.9
Fair Value, Inputs, Level 1 | Equity Funds | Deferred Compensation Plan [Member]      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Trading Securities 2.7 2.0 1.7
Fair Value, Inputs, Level 1 | Fixed Income Funds [Member]      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Trading Securities 4.2 3.8 4.0
Fair Value, Inputs, Level 1 | Fixed Income Funds [Member] | Deferred Compensation Plan [Member]      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Trading Securities 0.1 0.1 0.1
Fair Value, Inputs, Level 1 | Money Market Funds      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Trading Securities 1.9 2.5 1.8
Fair Value, Inputs, Level 1 | Money Market Funds | Deferred Compensation Plan [Member]      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Trading Securities $ 0.1 $ 0.1 $ 0.1