Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2018	Jun. 30, 2018
Net operating loss carry-forwards and tax credit carry-forwards
Anticipated tax expense associated with the base-erosion and anti-abuse tax (“BEAT”) provision of the 2017 Tax Act		$ 0
Additional tax expense due to change in tax status	$ 22
Tax expense on Federal blender’s credits recognized as revenue	4
One-time Federal blender's credits recognized as revenue	$ 42
Maximum
Net operating loss carry-forwards and tax credit carry-forwards
Anticipated tax expense associated with the global intangible low-taxed income (“GILTI”) provision of the 2017 Tax Act		$ 1