Crude Oil Supply and Inventory Purchase Agreement - Interest Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Oil and Gas, Delivery Commitment [Line Items]
Gain (Loss) On Financing Interest Expense	$ 0.0	$ (3.9)
Interest expense | J. Aron
Oil and Gas, Delivery Commitment [Line Items]
Financing Interest Expense	4.2	9.1
El Dorado Refinery | Interest expense | J. Aron
Oil and Gas, Delivery Commitment [Line Items]
Financing Interest Expense	2.4	3.6
Big Spring refinery | Interest expense | J. Aron
Oil and Gas, Delivery Commitment [Line Items]
Financing Interest Expense	0.7	4.1
Krotz Spring Refinery | Interest expense | J. Aron
Oil and Gas, Delivery Commitment [Line Items]
Financing Interest Expense	$ 1.1	$ 1.4