Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Mar. 31, 2019
Income Taxes Disclosure [Line Items]
Decrease in unrecognized tax benefits within the next twelve months	$ 280.0
Increase in unrecognized tax benefits within the next twelve months	30.0
Provisional net tax benefit	$ (5.2)			$ (45.5)
Effective tax rate	(1.00%)			15.60%
Goodwill impairment	$ 612.0
U.S. corporate income tax rate	21.00%
Tax Reform and AHV Financing [Member]
Income Taxes Disclosure [Line Items]
Provisional net tax benefit		$ 51.2	$ 263.8