Derivatives and Financial Instruments - Recorded Amounts and Estimated Fair Values of Long-term Debt and Derivative Financial Instruments (Detail) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Derivative [Line Items]
Total debt	$ 1,638.6	$ 1,638.7
Recorded Amount
Derivative [Line Items]
Variable rate debt	852.7	843.8
Fixed rate debt	800.0	819.3
Total debt	1,652.7	1,663.1
Fair Value
Derivative [Line Items]
Variable rate debt	852.7	843.8
Fixed rate debt	828.2	814.3
Total debt	$ 1,680.9	$ 1,658.1