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, 2018 |
Mar. 31, 2017 |
|
| Debt, Interest Income, Expense and Other Finance Costs [Abstract] | ||
| Interest income | $ 0.6 | $ 1.0 |
| Interest expense and other financing costs | (16.9) | (13.7) |
| Interest income (expense) and other financing costs, net | $ (16.3) | $ (12.7) |