Business Segment Information - Segment Assets (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Segment assets, excluding tax assets	$ 1,654.4	$ 1,751.6
Income tax receivable	7.4	2.2
Total assets	1,661.8	1,753.8
Operating Segments | Domestic Coke
Segment Reporting Information [Line Items]
Segment assets, excluding tax assets	1,352.8	1,434.2
Operating Segments | Brazil Coke
Segment Reporting Information [Line Items]
Segment assets, excluding tax assets	14.4	14.6
Operating Segments | Logistics
Segment Reporting Information [Line Items]
Segment assets, excluding tax assets	196.4	200.8
Corporate and Other
Segment Reporting Information [Line Items]
Segment assets, excluding tax assets	$ 90.8	$ 102.0