Senior Secured Credit Facility (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Jun. 30, 2016
Senior Secured Credit Facility
Debt and Lease Obligation	$ 3,616.0		$ 3,616.0		$ 3,657.0
Letters of Credit Outstanding, Amount	0.1		0.1
Incremental Borrowings, Amount	$ 1,000.0		$ 1,000.0
Incremental Borrowings Criteria, Percentage of Consolidated EBITDA	100.00%		100.00%
Incremental Borrowings Criteria, Senior Secured Leverage ratio	4.25		4.25
Net Leverage Ratio Requirement	5.5		5.5
Covenant Dividend Restriction Amount	$ 75.0		$ 75.0
Covenant Dividend Restriction Percentage of Consolidated EBITDA	7.50%		7.50%
Net Leverage Ratio Requirement, Dividends	4.75		4.75
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	$ (5.0)	$ 4.8	$ 36.8	$ 41.2
Hedge instruments: Net change on interest rate cap	0.0	0.4	(4.1)	12.2
2020 3 year Interest Rate Swap [Member]
Senior Secured Credit Facility
Derivative, Notional Amount	$ 1,110.0		$ 1,110.0
2020 3 year Interest Rate Swap [Member] | Minimum [Member]
Senior Secured Credit Facility
Derivative, Fixed Interest Rate	0.9125%		0.9125%
2020 3 year Interest Rate Swap [Member] | Maximum [Member]
Senior Secured Credit Facility
Derivative, Fixed Interest Rate	0.928%		0.928%
2020 2 year Interest Rate Swap [Member]
Senior Secured Credit Facility
Derivative, Notional Amount	$ 1,145.0		$ 1,145.0
2020 2 year Interest Rate Swap [Member] | Minimum [Member]
Senior Secured Credit Facility
Derivative, Fixed Interest Rate	0.52%		0.52%
2020 2 year Interest Rate Swap [Member] | Maximum [Member]
Senior Secured Credit Facility
Derivative, Fixed Interest Rate	0.5295%		0.5295%
Interest Rate Swap [Member]
Senior Secured Credit Facility
Derivative, Notional Amount	$ 1,415.0		$ 1,415.0
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	5.0	4.5	39.9	33.0
Interest Expense, Hedge, gross of tax	(10.3)	(1.5)	(21.9)	(2.6)
Hedge instruments: Net change on interest rate cap	6.4	5.6	53.3	43.7
Interest Expense, Hedge, net of tax	$ (8.0)	(1.3)	(16.5)	(2.0)
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months			$ (40.4)
Interest Rate Swap [Member] | Minimum [Member]
Senior Secured Credit Facility
Derivative, Fixed Interest Rate	2.702%		2.702%
Interest Rate Swap [Member] | Maximum [Member]
Senior Secured Credit Facility
Derivative, Fixed Interest Rate	2.706%		2.706%
Interest Rate Cap [Member]
Senior Secured Credit Facility
Derivative, Cap Interest Rate						0.75%
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax		0.4		9.2
Interest Expense, Hedge, gross of tax		0.3	$ (6.7)	3.2
Hedge instruments: Net change on interest rate cap		0.4		12.2
Interest Expense, Hedge, net of tax		$ 0.2	(5.1)	$ 2.5
Net recognized loss into income on Hedge			4.1
Net recognized loss into income on Hedge, net of tax			$ 3.1
Senior Loans [Member]
Senior Secured Credit Facility
Debt Instrument, Description of Variable Rate Basis			LIBOR
Senior Secured Term Loan B-5 [Member]
Senior Secured Credit Facility
Debt and Lease Obligation	$ 2,490.6		$ 2,490.6		2,508.5
Debt Instrument, Fair Value Disclosure	2,442.9		2,442.9
Senior Secured Revolving Line of Credit
Senior Secured Credit Facility
Debt and Lease Obligation	0.0		0.0		0.0
Line of Credit Facility, Remaining Borrowing Capacity	299.9		299.9
Senior Secured Term Loan A-3 [Member]
Senior Secured Credit Facility
Debt and Lease Obligation	1,124.0		1,124.0		$ 1,144.5
Debt Instrument, Fair Value Disclosure	$ 1,112.9		$ 1,112.9