Components of Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 56.8	$ 25.5
Other comprehensive income
Net unrealized gain	19.5	9.3
Total comprehensive income	$ 76.3	$ 34.8

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

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+ Details