Income Taxes - Provision for Income Taxes and Effective Income Tax Rate (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Income (loss) before income taxes	$ 135.9	$ 42.8	$ 388.1	$ (138.9)
Provision for income taxes	$ 2.7	$ 12.8	$ 25.8	$ 24.3
Effective income tax provision rate (as a percent)	2.00%	29.90%	6.60%	(17.50%)