Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Taxes Disclosure [Line Items]
Decrease in unrecognized tax benefits within the next twelve months	$ 250.0		$ 250.0
Increase in unrecognized tax benefits within the next twelve months	20.0		20.0
Amount of potential additional income tax expense related to an IRS revenue agents report subject to interest and penalties	370.0		370.0
Provision for income taxes	$ 16.8	$ 9.7	$ 71.1	$ 1.2
Effective tax rate	10.40%	3.80%	12.80%	0.30%
Goodwill impairment				$ 612.0
U.S. corporate income tax rate			21.00%
Tax Reform and AHV Financing [Member]
Income Taxes Disclosure [Line Items]
Provision for income taxes			$ (10.0)