Commitments and Contingencies (Details) MBbls in Thousands, $ in Millions		12 Months Ended			28 Months Ended	31 Months Ended
	Jan. 01, 2019 USD ($)	Dec. 31, 2019 USD ($) bbl / d renewal MBbls	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2019 USD ($) bbl / d renewal MBbls	Mar. 31, 2020 USD ($)
Commitments and Contingencies (Textual)
MVP Terminal construction costs		$ 44,294	$ 42,473		$ 44,294
Contributions to MVP		164	181	$ 406
Equity investment in MVP		942	542		$ 942
Cost of undivided interest in pipeline		$ 72	212	$ 72
MVP Terminalling, LLC (MVP) [Member]
Commitments and Contingencies (Textual)
Initial term of terminal agreement		12 years
Number of available automatic renewals | renewal		2			2
Automatic renewal term of terminalling agreement		5 years
Construction in Progress [Member]
Commitments and Contingencies (Textual)
MVP Terminal construction costs		$ 1,731	1,960		$ 1,731
MVP Terminal [Member]
Commitments and Contingencies (Textual)
Approximate storage capacity of terminal (in thousands of barrels) | MBbls		5			5
Contributions to MVP		$ 157			$ 404
Equity investment in MVP		$ 401			$ 401
MVP Terminal [Member] | Topic 842 [Member]
Commitments and Contingencies (Textual)
Derecognized assets related to MVP	$ (539)
Derecognized liability related to MVP	(292)
Equity investment in MVP recorded due to derecognition of assets and liabilities	$ 247
MVP Terminal [Member] | Magellan Midstream Partners LP (Magellan) [Member]
Commitments and Contingencies (Textual)
Long-term liability recorded			292
MVP Terminal [Member] | Expected Impact [Member]
Commitments and Contingencies (Textual)
Contributions to MVP						$ 420
MVP Terminal [Member] | Construction in Progress [Member]
Commitments and Contingencies (Textual)
MVP Terminal construction costs			$ 539
MVP Terminal [Member] | Minimum [Member] | Construction in Progress [Member] | Expected Impact [Member]
Commitments and Contingencies (Textual)
MVP Terminal construction costs						840
MVP Terminal [Member] | Maximum [Member] | Construction in Progress [Member] | Expected Impact [Member]
Commitments and Contingencies (Textual)
MVP Terminal construction costs						$ 1,400
MVP Terminal [Member] | Valero Energy Corporation [Member]
Commitments and Contingencies (Textual)
Approximate storage capacity of terminal (in thousands of barrels) | MBbls		4			4
Central Texas Pipeline [Member]
Commitments and Contingencies (Textual)
Undivided interest in project (percent)		40.00%			40.00%
Pipeline capacity (barrels per day) | bbl / d		150,000			150,000
Cost of undivided interest in pipeline		$ 80			$ 160
MVP Terminalling, LLC (MVP) [Member]
Commitments and Contingencies (Textual)
Membership interest (percent)		50.00%
MVP Terminalling, LLC (MVP) [Member] | Expected Impact [Member]
Commitments and Contingencies (Textual)
Membership interest (percent)						50.00%