Changes in and Reclassifications out of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]			$ 1,916.4
Interest and other borrowing costs		$ 29.4	$ 32.0	57.3	$ 68.0
Income tax effect		(14.9)	(11.4)	(33.3)	(19.1)
Ending balance		1,946.7	1,813.7	1,946.7	1,813.7
Accumulated Gain (Loss) Net Cash Flow Hedge Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		17.6	(16.0)	(1.9)	(25.3)
Unrealized (loss) gain on derivative contracts		(13.6)	(3.6)	1.2	5.1
Amounts recorded in AOCI related to Unrealized gain (loss) on derivative contracts, income tax effect		3.4	0.9	(0.3)	(1.2)
Net other comprehensive income (loss)		2.2	(0.4)	21.7	8.9
Ending balance		19.8	(16.4)	19.8	(16.4)
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		16.5	3.1	27.6	6.6
Income tax effect		$ (4.1)	$ (0.8)	$ (6.8)	$ (1.6)

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