Derivatives (Offsetting Derivative Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	$ (9.5)	$ (13.7)
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	2.3	13.7
Derivative Liability	(7.2)	0.0
Not Designated as Hedging Instrument | Fuel Product | Supply and Offtake Agreements
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	(7.2)	0.0
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0.0	0.0
Derivative Liability	(7.2)	0.0
Not Designated as Hedging Instrument | Fuel Product | WCS Crude Oil Basis Swaps
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	(1.3)	(1.6)
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	1.3	1.6
Derivative Liability	0.0	0.0
Not Designated as Hedging Instrument | Fuel Product | WCS Crude Oil Percentage Basis Swaps
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	0.0	(6.1)
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0.0	6.1
Derivative Liability	0.0	0.0
Not Designated as Hedging Instrument | Fuel Product | Gasoline Crack Spread Swaps
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	(0.5)	0.0
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0.5	0.0
Derivative Liability	0.0	0.0
Not Designated as Hedging Instrument | Fuel Product | Diesel Crack Spread Swaps
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	(0.5)	0.0
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0.5	0.0
Derivative Liability	0.0	0.0
Not Designated as Hedging Instrument | Fuel Product | Diesel Percent Basis Crack Spread Swaps
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	0.0	(6.0)
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0.0	6.0
Derivative Liability	$ 0.0	$ 0.0