Income Taxes - Narrative (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Tax Expense (Benefit)	$ 9.9	$ (8.7)	$ 14.1	$ (4.7)
Effective Income Tax Rate Reconciliation, Percent			21.00%	38.00%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent				21.00%
Other Tax Expense (Benefit)			$ 7.0