Supplementary Statistics - Supplementary Statistics (Detail) - USD ($)
$ in Millions
 3 Months Ended
Feb. 01, 2018
Mar. 31, 2018
Mar. 31, 2017
Supplementary Statistics [Line Items]      
Income from operations   $ 440 $ 291
Capital expenditures and investments [1]   748 1,325
MarEn Bakken      
Supplementary Statistics [Line Items]      
Cash paid to acquire equity method investments     500
Refining & Marketing      
Supplementary Statistics [Line Items]      
Income from operations $ (181)    
Midstream      
Supplementary Statistics [Line Items]      
Income from operations $ 181    
Midstream | Ozark Pipeline      
Supplementary Statistics [Line Items]      
Capital expenditures and investments     220
Operating Segments      
Supplementary Statistics [Line Items]      
Income from operations   529 374
Capital expenditures and investments [2]   712 1,297
Cash paid to acquire equity method investments   41 566 [3]
Operating Segments | Refining & Marketing      
Supplementary Statistics [Line Items]      
Income from operations   (133) (70)
Capital expenditures and investments   191 192
Operating Segments | Speedway      
Supplementary Statistics [Line Items]      
Income from operations   95 135
Capital expenditures and investments   39 35
Operating Segments | Midstream      
Supplementary Statistics [Line Items]      
Income from operations   567 [4] 309
Capital expenditures and investments   482 1,070 [5]
Corporate and Other      
Supplementary Statistics [Line Items]      
Income from operations [6]   (88) (83)
Capital expenditures and investments [7]   36 28
Capitalized interest   18 12
Segment Reconciling Items      
Supplementary Statistics [Line Items]      
Pension settlement expenses   $ (1) $ 0
[1] Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
[2] Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
[3] The three months ended March 31, 2017 includes an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system.
[4] On February 1, 2018, we contributed certain refining logistics assets and fuels distributions services to MPLX. The results of these new businesses are reported in the Midstream segment prospectively from February 1, resulting in a net reduction of $181 million to Refining & Marketing segment results and a net increase to Midstream segment results of the same amount. No effect was given to prior periods as these entities were not considered businesses prior to February 1, 2018.
[5] The Midstream segment includes $220 million for the acquisition of the Ozark pipeline and an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system for the three months ended March 31, 2017.
[6] Corporate and other unallocated items consists primarily of MPC’s corporate administrative expenses and costs related to certain non-operating assets, except for corporate overhead expenses attributable to MPLX, which are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments.
[7] Includes capitalized interest of $18 million and $12 million for the three months ended March 31, 2018 and 2017, respectively