Income Taxes - Unrecognized Tax Benefits and Effect on Effective Income Tax Rate (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance of unrecognized tax benefits	$ 390.3	$ 356.4	$ 214.3
Additions for tax positions of current year	2.7	3.4	106.0
Additions for tax positions of prior years	8.3	47.9	59.5
Reductions for tax positions of prior years	(18.2)	(16.0)	(7.0)
Reductions for lapses of statutes of limitation and settlements	(3.5)	(1.4)	(16.4)
Ending balance of unrecognized tax benefits	$ 379.6	$ 390.3	$ 356.4