Other Financial Information - Other Income (Expense), Net (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Other Financial Information [Abstract]
Interest income	$ 23.5	$ 14.9
Interest expense	(24.2)	(26.0)
Gain (loss) on investments, net	1.6	(0.5)
Other	0.9	(2.5)
Other income (expense), net	$ 1.8	$ (14.1)