Other Financial Information - Other Expense, Net (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Other Financial Information [Abstract]
Interest income	$ 6.1	$ 19.7	$ 30.4	$ 63.0
Interest expense	(19.1)	(22.1)	(58.5)	(68.3)
Loss on extinguishment of debt	0.0	(15.3)	0.0	(15.3)
Gain (loss) on investments, net	2.0	(3.4)	2.7	(4.6)
Other	(2.5)	0.7	(3.6)	2.0
Other expense, net	$ (13.5)	$ (20.4)	$ (29.0)	$ (23.2)