Other Assets and Liabilities - Other Non-Current Assets (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Schedule of Other Assets and Liabilities [Line Items]
Supply and Offtake receivable	$ 32.7	$ 32.7
Other Equity investment	9.4	8.9
Deferred financing costs	8.1	8.5
Note receivable	0.0	6.2
Long-term derivative assets (see Note 9)	3.2	0.1
Other	10.0	11.4
Total	$ 63.4	$ 67.8