Other Assets and Liabilities - Other Non-Current Assets (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Schedule of Other Assets and Liabilities [Line Items]
Supply and Offtake receivable	$ 32.7	$ 32.7
Other Equity investment	10.4	8.9
Deferred financing costs	7.5	8.5
Long-term derivative assets (see Note 9)	0.0	0.1
Other	13.8	17.6
Total	$ 64.4	$ 67.8