Components of Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Statement of Comprehensive Income [Abstract]
Net income	$ 37.0	$ 36.4	$ 71.0	$ 76.9
Other comprehensive income (loss)
Derivative contracts increase (decrease)	2.0	(0.2)	2.8	(3.1)
Total comprehensive income	$ 39.0	$ 36.2	$ 73.8	$ 73.8

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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+ Details