Changes in and Reclassifications out of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2022	Mar. 31, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]	$ 1,916.4
Interest and other borrowing costs		27.9	$ 36.0
Income tax effect		(18.4)	(7.7)
Ending balance		1,899.0	1,776.5
Accumulated Gain (Loss) Net Cash Flow Hedge Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(1.9)	(25.3)
Amounts recorded in AOCL related to Unrealized gain (loss) on derivative contracts, before tax		14.8	8.7
Amounts recorded in AOCI related to Unrealized gain (loss) on derivative contracts, income tax effect		(3.7)	(2.1)
Net other comprehensive income		19.5	9.3
Ending balance		17.6	(16.0)
Accumulated Gain (Loss) Net Cash Flow Hedge Parent | Amounts reclassified out of AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and other borrowing costs		11.1	3.5
Income tax effect		$ (2.7)	$ (0.8)

[1] The December 31, 2021 balance sheet has been derived from audited financial statements.