Derivatives and Financial Instruments - Recorded Amounts and Estimated Fair Values (Detail) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Derivative [Line Items]
Total debt	$ 2,084.3	$ 1,988.3
Recorded Amount
Derivative [Line Items]
Variable rate debt	1,282.7	1,187.5
Fixed rate debt	819.3	819.3
Total debt	2,102.0	2,006.8
Fair Value
Derivative [Line Items]
Variable rate debt	1,282.7	1,187.5
Fixed rate debt	808.0	824.5
Total debt	$ 2,090.7	$ 2,012.0