Debt, Interest Income, Expense and Other Finance Costs - Interest Income, Expense and Other Financing Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt, Interest Income, Expense and Other Finance Costs [Abstract]
Interest income	$ 6.2	$ 3.9	$ 6.0
Interest expense and other financing costs	(80.0)	(74.8)	(66.3)
Interest expense and other financing costs, net	$ (73.9)	$ (71.0)	$ (60.3)