Derivatives and Financial Instruments - Recorded Amounts and Estimated Fair Values (Detail) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Derivative [Line Items]
Total debt	$ 1,484.1	$ 1,638.6
Recorded Amount
Derivative [Line Items]
Variable rate debt	700.7	852.7
Fixed rate debt	800.0	800.0
Total debt	1,500.7	1,652.7
Fair Value
Derivative [Line Items]
Variable rate debt	700.7	852.7
Fixed rate debt	785.1	828.2
Total debt	$ 1,485.8	$ 1,680.9

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

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+ Details