Crude Oil Supply and Inventory Purchase Agreement - Recurring Cash Fee Paid (Details) - Interest expense - J. Aron - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Oil and Gas Delivery Commitments and Contracts [Line Items]
Recurring cash fees paid	$ 6.9	$ 6.3	$ 20.5	$ 18.7
El Dorado Refinery
Oil and Gas Delivery Commitments and Contracts [Line Items]
Recurring cash fees paid	2.9	2.7	8.5	8.3
Krotz Spring Refinery
Oil and Gas Delivery Commitments and Contracts [Line Items]
Recurring cash fees paid	2.5	1.8	7.6	5.0
Big Spring refinery
Oil and Gas Delivery Commitments and Contracts [Line Items]
Recurring cash fees paid	$ 1.5	$ 1.8	$ 4.4	$ 5.4