Income Taxes (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
Income Tax Examination [Line Items]
Effective tax benefit rate	23.10%	21.60%	23.50%	19.20%
U.S. federal statutory rate	21.00%	21.00%	21.00%	21.00%
Effective Income Tax Rate Reconciliation, Tax Expense (Benefit), Share-based Payment Arrangement, Amount		$ 4.6	$ 22.4	$ 31.9
Unrecognized tax benefits	$ 39.2		39.2		$ 32.8
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 17.3		$ 17.3		$ 13.6
Other Tax Expense (Benefit)		17.0		37.1
State and Local Jurisdiction [Member]
Income Tax Examination [Line Items]
Other Tax Expense (Benefit)		$ 11.7		$ 11.2