Other Assets and Liabilities Other Non-Current Assets (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Other Assets, Noncurrent [Line Items]
Total	$ 52.9	$ 126.8
Other long-term assets
Other Assets, Noncurrent [Line Items]
Prepaid tax asset	0.0	56.2
Deferred financing costs	10.6	5.9
Long-term income tax receivables	0.0	2.1
Supply and Offtake receivable	32.7	46.3
Long-term derivative assets	1.0	0.0
Other	8.6	16.3
Total	$ 52.9	$ 126.8