Derivatives and Financial Instruments - Recorded Amounts and Estimated Fair Values (Detail) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Derivative [Line Items]
Total debt	$ 1,835.7	$ 1,638.7
Recorded Amount
Derivative [Line Items]
Variable rate debt	1,030.7	843.8
Fixed rate debt	819.3	819.3
Total debt	1,850.0	1,663.1
Fair Value
Derivative [Line Items]
Variable rate debt	1,030.7	843.8
Fixed rate debt	823.8	814.3
Total debt	$ 1,854.5	$ 1,658.1