Supplementary Statistics - Operating Statistics (Detail)
bbl / d in Thousands, gal in Millions, CFPD in Millions, $ in Millions
 3 Months Ended
Mar. 31, 2018
USD ($)
bbl / d
Store
CFPD
$ / gal
$ / bbl
gal
Mar. 31, 2017
USD ($)
bbl / d
Store
CFPD
$ / gal
$ / bbl
gal
Operating Statistics [Line Items ]    
MPC Consolidated Refined Product Sales Volumes (thousands of barrels per day) [1] 2,275 2,085
Refining & Marketing    
Refining & Marketing Operating Statistics    
Refining & Marketing refined product sales volume (thousands of barrels per day) [2] 2,261 2,070
Refining & Marketing margin (dollars per barrel) | $ / bbl [3] 10.58 11.65
Crude oil capacity utilization percent [4] 93.00% 83.00%
Refinery throughputs (thousands of barrels per day) [5] 1,905 1,708
Sour crude oil throughput percent 52.00% 67.00%
WTI-priced crude oil throughput percent 26.00% 15.00%
Refined product yields (thousands of barrels per day) [5] 1,936 1,748
Inter-refinery transfers 42 55
Refinery direct operating costs (dollars per barrel):    
Planned turnaround and major maintenance | $ / bbl [6] 2.22 3.10
Depreciation and amortization | $ / bbl [6] 1.37 1.63
Other manufacturing | $ / bbl [6],[7] 4.09 4.72
Total | $ / bbl [6] 7.68 9.45
Refining & Marketing | Crude oil refined    
Refining & Marketing Operating Statistics    
Refinery throughputs (thousands of barrels per day) [5] 1,745 1,511
Refining & Marketing | Other charge and blendstocks    
Refining & Marketing Operating Statistics    
Refinery throughputs (thousands of barrels per day) [5] 160 197
Refining & Marketing | Gasoline    
Refining & Marketing Operating Statistics    
Refined product yields (thousands of barrels per day) [5] 917 867
Refining & Marketing | Distillates    
Refining & Marketing Operating Statistics    
Refined product yields (thousands of barrels per day) [5] 609 544
Refining & Marketing | Propane    
Refining & Marketing Operating Statistics    
Refined product yields (thousands of barrels per day) [5] 31 28
Refining & Marketing | Feedstocks and special products    
Refining & Marketing Operating Statistics    
Refined product yields (thousands of barrels per day) [5] 287 224
Refining & Marketing | Heavy fuel oil    
Refining & Marketing Operating Statistics    
Refined product yields (thousands of barrels per day) [5] 34 29
Refining & Marketing | Asphalt    
Refining & Marketing Operating Statistics    
Refined product yields (thousands of barrels per day) [5] 58 56
Refining & Marketing | Gulf Coast:    
Refining & Marketing Operating Statistics    
Refinery throughputs (thousands of barrels per day) [8] 1,223 1,072
Sour crude oil throughput percent 60.00% 84.00%
WTI-priced crude oil throughput percent 13.00% 4.00%
Refined product yields (thousands of barrels per day) [8] 1,251 1,104
Refinery direct operating costs (dollars per barrel):    
Planned turnaround and major maintenance | $ / bbl [6] 2.87 4.31
Depreciation and amortization | $ / bbl [6] 1.09 1.35
Other manufacturing | $ / bbl [6],[7] 3.91 4.62
Total | $ / bbl [6] 7.87 10.28
Refining & Marketing | Gulf Coast: | Crude oil refined    
Refining & Marketing Operating Statistics    
Refinery throughputs (thousands of barrels per day) [8] 1,056 850
Refining & Marketing | Gulf Coast: | Other charge and blendstocks    
Refining & Marketing Operating Statistics    
Refinery throughputs (thousands of barrels per day) [8] 167 222
Refining & Marketing | Gulf Coast: | Gasoline    
Refining & Marketing Operating Statistics    
Refined product yields (thousands of barrels per day) [8] 534 499
Refining & Marketing | Gulf Coast: | Distillates    
Refining & Marketing Operating Statistics    
Refined product yields (thousands of barrels per day) [8] 360 309
Refining & Marketing | Gulf Coast: | Propane    
Refining & Marketing Operating Statistics    
Refined product yields (thousands of barrels per day) [8] 19 21
Refining & Marketing | Gulf Coast: | Feedstocks and special products    
Refining & Marketing Operating Statistics    
Refined product yields (thousands of barrels per day) [8] 298 243
Refining & Marketing | Gulf Coast: | Heavy fuel oil    
Refining & Marketing Operating Statistics    
Refined product yields (thousands of barrels per day) [8] 23 18
Refining & Marketing | Gulf Coast: | Asphalt    
Refining & Marketing Operating Statistics    
Refined product yields (thousands of barrels per day) [8] 17 14
Refining & Marketing | Midwest:    
Refining & Marketing Operating Statistics    
Refinery throughputs (thousands of barrels per day) [8] 724 691
Sour crude oil throughput percent 38.00% 45.00%
WTI-priced crude oil throughput percent 47.00% 29.00%
Refined product yields (thousands of barrels per day) [8] 727 699
Refinery direct operating costs (dollars per barrel):    
Planned turnaround and major maintenance | $ / bbl [6] 0.99 0.98
Depreciation and amortization | $ / bbl [6] 1.77 1.93
Other manufacturing | $ / bbl [6],[7] 4.16 4.50
Total | $ / bbl [6] 6.92 7.41
Refining & Marketing | Midwest: | Crude oil refined    
Refining & Marketing Operating Statistics    
Refinery throughputs (thousands of barrels per day) [8] 689 661
Refining & Marketing | Midwest: | Other charge and blendstocks    
Refining & Marketing Operating Statistics    
Refinery throughputs (thousands of barrels per day) [8] 35 30
Refining & Marketing | Midwest: | Gasoline    
Refining & Marketing Operating Statistics    
Refined product yields (thousands of barrels per day) [8] 383 368
Refining & Marketing | Midwest: | Distillates    
Refining & Marketing Operating Statistics    
Refined product yields (thousands of barrels per day) [8] 249 235
Refining & Marketing | Midwest: | Propane    
Refining & Marketing Operating Statistics    
Refined product yields (thousands of barrels per day) [8] 12 8
Refining & Marketing | Midwest: | Feedstocks and special products    
Refining & Marketing Operating Statistics    
Refined product yields (thousands of barrels per day) [8] 31 35
Refining & Marketing | Midwest: | Heavy fuel oil    
Refining & Marketing Operating Statistics    
Refined product yields (thousands of barrels per day) [8] 11 11
Refining & Marketing | Midwest: | Asphalt    
Refining & Marketing Operating Statistics    
Refined product yields (thousands of barrels per day) [8] 41 42
Speedway    
Speedway Operating Statistics    
Convenience stores at period-end | Store 2,742 2,731
Gasoline and distillate sales (millions of gallons) | gal 1,393 1,393
Gasoline and distillate margin (dollars per gallon) | $ / gal [9] 0.1561 0.1566
Merchandise sales (in millions) | $ $ 1,129 $ 1,127
Merchandise margin (in millions) | $ $ 319 $ 320
Merchandise margin percent 28.30% 28.40%
Same store gasoline sales volume (period over period) percentage (1.50%) (1.00%)
Merchandise sales excluding cigarettes (period over period) percentage [10] 2.30% 2.10%
Midstream    
Midstream Operating Statistics    
Crude oil and refined product pipeline throughputs (thousands of barrels per day) [11] 3,459 2,888
Terminal throughput (thousands of barrels per day) 1,445 1,424
Gathering system throughput (MMcf/d) | CFPD [12] 4,171 3,184
Natural gas processed (MMcf/d) | CFPD [12] 6,629 6,132
C2 and NGLs fractionated (thousands barrels per day) [12] 423 367
[1] Total average daily volumes of refined product sales to wholesale, branded and retail customers.
[2] Includes intersegment sales.
[3] Sales revenue less cost of refinery inputs and purchased products, divided by total refinery throughputs.
[4] Based on calendar-day capacity, which is an annual average that includes down time for planned maintenance and other normal operating activities.
[5] Excludes inter-refinery volumes of 42 mbpd and 55 mbpd for the three months ended March 31, 2018 and 2017, respectively
[6] Per barrel of total refinery throughputs. Effective with the February 1, 2018 dropdown, direct operating costs related to certain refining logistics assets are now reported in the Midstream segment. No effect was given to prior periods as this entity was not considered a business prior to February 1, 2018.
[7] Includes utilities, labor, routine maintenance and other operating costs.
[8] Includes inter-refinery transfer volumes.
[9] The price paid by consumers less the cost of refined products, including transportation, consumer excise taxes and bank card processing fees, divided by gasoline and distillate sales volume.
[10] Excludes cigarettes.
[11] Includes common-carrier pipelines and private pipelines owned or operated by MPLX, excluding equity method investments.
[12] Includes amounts related to unconsolidated equity method investments on a 100 percent basis.