Segment Information - Income From Operations Attributable To Operating Segments (Detail) - USD ($)
$ in Millions
 3 Months Ended
Feb. 01, 2018
Mar. 31, 2018
Mar. 31, 2017
Segment Reporting Information [Line Items]      
Sales and other operating revenues [1]   $ 18,694 $ 16,134
Sales to related parties   172 154
Income from operations   440 291
Income from equity method investments   86 57
Depreciation and amortization   528 536
Capital expenditures and investments [2]   748 1,325
MarEn Bakken      
Segment Reporting Information [Line Items]      
Cash paid to acquire equity method investments     500
Intersegment Eliminations      
Segment Reporting Information [Line Items]      
Sales and other operating revenues   3,011 2,935 [3]
Operating Segments      
Segment Reporting Information [Line Items]      
Sales and other operating revenues   21,877 19,223
Income from operations   529 374
Income from equity method investments   86 57
Depreciation and amortization [4]   512 522
Capital expenditures and investments [5]   712 1,297
Cash paid to acquire equity method investments   41 566 [6]
Refining & Marketing      
Segment Reporting Information [Line Items]      
Sales and other operating revenues   13,412 11,221
Sales to related parties   170 152
Income from operations $ (181)    
Refining & Marketing | Intersegment Eliminations      
Segment Reporting Information [Line Items]      
Sales and other operating revenues   2,379 2,590
Refining & Marketing | Operating Segments      
Segment Reporting Information [Line Items]      
Sales and other operating revenues   15,961 13,963
Income from operations   (133) (70)
Income from equity method investments   3 2
Depreciation and amortization   252 267
Capital expenditures and investments   191 192
Speedway      
Segment Reporting Information [Line Items]      
Sales and other operating revenues   4,569 4,381
Sales to related parties   2 2
Speedway | Intersegment Eliminations      
Segment Reporting Information [Line Items]      
Sales and other operating revenues   1 1
Speedway | Operating Segments      
Segment Reporting Information [Line Items]      
Sales and other operating revenues   4,572 4,384
Income from operations   95 135
Income from equity method investments   14 13
Depreciation and amortization   79 64
Capital expenditures and investments   39 35
Midstream      
Segment Reporting Information [Line Items]      
Sales and other operating revenues   713 532
Sales to related parties   0 0
Income from operations $ 181    
Midstream | Ozark Pipeline      
Segment Reporting Information [Line Items]      
Capital expenditures and investments     220
Midstream | Intersegment Eliminations      
Segment Reporting Information [Line Items]      
Sales and other operating revenues   631 344
Midstream | Operating Segments      
Segment Reporting Information [Line Items]      
Sales and other operating revenues   1,344 876
Income from operations   567 [7] 309
Income from equity method investments   69 42
Depreciation and amortization   181 191
Capital expenditures and investments   482 1,070 [8]
Reportable Segment      
Segment Reporting Information [Line Items]      
Sales and other operating revenues   $ 18,694 $ 16,134
[1] The 2018 period reflects an election to present certain taxes on a net basis. See Notes 2 and 3 for further information.
[2] Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
[3] Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties
[4] Differences between segment totals and MPC totals represent amounts related to unallocated items and are included in “Items not allocated to segments” in the reconciliation below.
[5] Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
[6] The three months ended March 31, 2017 includes an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system.
[7] 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.
[8] 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.