Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			19.00%	19.00%	19.30%
Gross unrecognized tax benefits		$ 51.4	$ 47.4	$ 51.4	$ 13.8	$ 46.3
Amount of tax benefits that, if recognized, would impact the effective tax rate			47.0
Payment of penalties		0.5	0.4	0.5
Payment of interest expense		3.6	3.7	$ 3.6
Foreign credit carryforwards			29.6
Tax loss carryforwards			2,957.4
Deferred tax assets, valuation allowance			663.1
Deferred Tax Assets, Operating Loss Carryforwards, Foreign			2,843.1
Deferred Tax Assets, Operating Loss Carryforwards, Foreign (jurisdictions with unlimited tax loss carryforward periods)			1,763.9
Deferred Tax Assets, Operating Loss Carryforwards, Domestic			99.7
State tax losses available for carry forward			64.0
Provisional income tax expense		$ 2.2
Measurement period adjustment	$ 3.6
Income tax decrease			1.4
Decrease of income tax expense related to remeasurement of deferred tax assets and liabilities			28.0
Transition tax expense			$ 26.6