Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning of period balance	$ 92.7	$ 60.9	$ 138.9
Increases for tax positions taken during a prior period	3.4	9.1	5.6
Decreases for tax positions taken during a prior period	(4.9)	(5.8)	(85.8)
Increases for tax positions taken during the current period	43.8	28.8	19.3
Decreases for tax positions related to settlements	0.0	0.0	(15.8)
Decreases for tax positions related to lapse of statute	(1.2)	(0.3)	(1.3)
End of period balance	$ 133.8	$ 92.7	$ 60.9