Property, Plant And Equipment - Summary Of Property, Plant And Equipment (Detail) - USD ($)
$ in Millions
Feb. 01, 2018
Mar. 31, 2018
Dec. 31, 2017
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross   $ 41,176 $ 40,538
Less accumulated depreciation   14,558 14,095
Property, plant and equipment, net   26,618 26,443
Refining & Marketing      
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, transfers $ (830)    
Midstream      
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, transfers $ 830    
Operating Segments | Refining & Marketing      
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross   18,117 [1] 19,490
Operating Segments | Speedway      
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross   5,359 5,358
Operating Segments | Midstream      
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross   16,889 [1] 14,898
Corporate and Other      
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross   $ 811 $ 792
[1] On February 1, 2018, we contributed certain refining logistics assets and fuels distribution services to MPLX. In connection with this transaction, approximately $830 million of net property, plant and equipment was recorded to the Midstream segment with an offsetting reduction to the Refining & Marketing segment.