Crude Oil Supply and Inventory Purchase Agreement - Interest Expense (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Oil and Gas, Delivery Commitment [Line Items]
Gain (Loss) On Financing Interest Expense		$ 0.0		$ 7.7	$ (3.9)	$ 11.4
Interest expense | J. Aron
Oil and Gas, Delivery Commitment [Line Items]
Financing Interest Expense	$ 3.3		$ 8.4		17.2	23.3
El Dorado Refinery | Interest expense | J. Aron
Oil and Gas, Delivery Commitment [Line Items]
Financing Interest Expense	1.5		3.7		7.8	10.9
Krotz Spring Refinery | Interest expense | J. Aron
Oil and Gas, Delivery Commitment [Line Items]
Financing Interest Expense	1.1		2.7		3.5	8.8
Big Spring refinery | Interest expense | J. Aron
Oil and Gas, Delivery Commitment [Line Items]
Financing Interest Expense	$ 0.7		$ 2.0		$ 5.9	$ 3.6