Components of Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 29.6	$ 20.4
Other comprehensive (loss) income
Derivative contracts (decrease) increase	(3.8)	2.5
Total comprehensive income	$ 25.8	$ 22.9

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

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