Crude Oil Supply and Inventory Purchase Agreement - Recurring Cash Fee Paid (Details) - Interest Expense - J. Aron & Company - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Oil and Gas, Delivery Commitment [Line Items]
Recurring cash fees paid	$ 28.1	$ 24.5	$ 16.8
El Dorado
Oil and Gas, Delivery Commitment [Line Items]
Recurring cash fees paid	11.6	10.7	9.7
Big Spring
Oil and Gas, Delivery Commitment [Line Items]
Recurring cash fees paid	6.2	7.1	4.1
Krotz Springs
Oil and Gas, Delivery Commitment [Line Items]
Recurring cash fees paid	$ 10.3	$ 6.7	$ 3.0