Debt, Interest Income, Expense and Other Finance Costs - Interest Income (Expense), and Other Financing Costs, net (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Debt, Interest Income, Expense and Other Finance Costs [Abstract]
Interest income	$ 2.3	$ 0.9
Interest expense and other financing costs	(11.1)	(16.2)
Interest income (expense) and other financing costs, net	$ (8.7)	$ (15.4)