Other Assets and Liabilities - Other Non-Current Assets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Other Assets, Noncurrent [Abstract]
Supply and Offtake receivable	$ 32.7	$ 32.7
Other equity Investments	8.9	0.0
Deferred financing costs	8.5	10.6
Note receivable - non-current portion (see Note 8)	6.2	0.0
Long-term derivative assets (see Note 12)	0.1	1.0
Other	11.4	8.6
Total	$ 67.8	$ 52.9