Components of Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 32.2	$ 43.5	$ 111.6	$ 145.9
Other comprehensive income
Derivative contracts increase	2.1	1.2	0.6	22.9
Total comprehensive income	$ 34.3	$ 44.7	$ 112.2	$ 168.8