Income Taxes - Components of Income Tax Provision (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current tax expense:
Federal		$ (14.2)	$ 62.3	$ 228.2
State and local		5.6	4.6	9.8
Foreign		69.9	64.1	59.8
Total current expense		61.3	131.0	297.8
Deferred tax expense (benefit):
Federal		59.4	(19.0)	56.8
State and local		11.8	4.0	(21.2)
Foreign		9.6	(39.4)	(25.9)
Total deferred tax expense (benefit)	$ (49.0)	80.8	(54.4)	9.7
Total income tax provision		$ 142.1	$ 76.6	$ 307.5