Property, Plant and Equipment (Summary of Property, Plant And Equipment) (Detail) - USD ($) $ in Millions	Jun. 30, 2020		Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 66,004		$ 64,623
Less accumulated depreciation	20,979	[1]	19,008
Property, plant and equipment, net	45,025		45,615
Operating Segments | Refining & Marketing
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	29,781		29,037
Operating Segments | Retail
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	7,199		7,104
Operating Segments | Midstream
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	27,696		27,193
Corporate
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 1,328		$ 1,289

[1] The June 30, 2020 balance includes property, plant and equipment impairment charges recorded during 2020. See Note 4 for additional information.