Long-term Debt - Interest Expense, Net (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Debt Instrument [Line Items]
Interest expense	$ (143.3)	$ (134.2)	$ (409.4)	$ (401.8)
Interest income	0.3	0.6	0.7	1.2
Capitalized interest	0.7	0.1	1.6	0.1
Interest expense, net	(142.3)	$ (133.5)	(407.1)	$ (400.5)
Coupon interest	2.3		3.5
Amortization of debt discount	2.9		4.3
Amortization of debt issuance costs	0.2		0.3
Convertible Notes interest expense	$ 5.4		$ 8.1