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	$ 1,559.8	$ 2,155.0
Recorded Amount
Derivative [Line Items]
Variable rate debt	268.2	866.3
Fixed rate debt	1,300.0	1,300.0
Total debt	1,568.2	2,166.3
Fair Value
Derivative [Line Items]
Variable rate debt	268.2	866.3
Fixed rate debt	1,296.9	1,251.8
Total debt	$ 1,565.1	$ 2,118.1