Contingent Liabilities (Details) - USD ($) $ in Millions		1 Months Ended
	May 20, 2016	Jan. 31, 2020	Mar. 31, 2020
Loss Contingencies [Line Items]
Customer Refund Liability, Current			$ 248
Accrued environmental loss liabilities			30
Former Alaska Refinery [Member]
Loss Contingencies [Line Items]
Loss Contingency, Damages Awarded, Value		$ 86
Energy Transfer Merger [Member]
Loss Contingencies [Line Items]
Loss contingency, damages sought, value	$ 1,480
Gas Pipeline [Member]
Loss Contingencies [Line Items]
Accrued environmental loss liabilities			4
Natural Gas Under Ground Storage Facilities [Member]
Loss Contingencies [Line Items]
Accrued environmental loss liabilities			6
Former Operations [Member]
Loss Contingencies [Line Items]
Accrued environmental loss liabilities			$ 20