Acquisitions (Schedule of Assets Acquired and Liabilities Assumed - Andeavor) (Details) - USD ($) $ in Millions		Dec. 31, 2018	Oct. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill		$ 20,184		$ 3,586	$ 3,587
Andeavor
Cash and cash equivalents			$ 382
Receivables			2,744
Inventories			5,204
Other current assets			378
Equity method investments			865
Property, plant and equipment, net			16,545
Other noncurrent assets(a)	[1]		3,086
Total assets acquired			29,204
Accounts payable			4,003
Payroll and benefits payable			348
Accrued taxes			590
Debt due within one year			34
Other current liabilities			392
Long-term debt			8,875
Deferred income taxes			1,609
Defined benefit postretirement plan obligations			432
Deferred credit and other liabilities			714
Noncontrolling interests			5,059
Total liabilities and noncontrolling interest assumed			22,056
Net assets acquired excluding goodwill			7,148
Goodwill			16,314
Net assets acquired			$ 23,462

[1] Includes intangible assets.