Derivative Financial Instruments - Schedule of Gains (Losses) on Derivatives (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($) derivative	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) derivative	Jun. 30, 2018 USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Total gain on derivatives, net	$ 4	$ 10	$ 20	$ 70
Forward purchases
Derivative Instruments, Gain (Loss) [Line Items]
Total gain on derivatives, net	$ 3	13	$ 20	28
Forward Contracts, RINs
Derivative Instruments, Gain (Loss) [Line Items]
Outstanding positions | derivative	34,000,000		34,000,000
Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Total gain on derivatives, net	$ 0	(2)	$ 0	44
Commodity Swap
Derivative Instruments, Gain (Loss) [Line Items]
Outstanding positions | derivative	0		0
Futures
Derivative Instruments, Gain (Loss) [Line Items]
Total gain on derivatives, net	$ 1	$ (1)	$ 0	$ (2)