Crude Oil Supply and Inventory Purchase Agreement - Interest Expense (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Oil and Gas, Delivery Commitment [Line Items]
Gain (Loss) On Financing Interest Expense		$ 0.0		$ (1.4)	$ (3.9)	$ 3.7
Interest expense | J. Aron
Oil and Gas, Delivery Commitment [Line Items]
Financing Interest Expense	$ 4.8		$ 8.7		13.9	14.9
El Dorado Refinery | Interest expense | J. Aron
Oil and Gas, Delivery Commitment [Line Items]
Financing Interest Expense	2.7		4.1		6.3	7.3
Krotz Spring Refinery | Interest expense | J. Aron
Oil and Gas, Delivery Commitment [Line Items]
Financing Interest Expense	1.0		2.9		2.4	6.0
Big Spring refinery | Interest expense | J. Aron
Oil and Gas, Delivery Commitment [Line Items]
Financing Interest Expense	$ 1.1		$ 1.7		$ 5.2	$ 1.6