Supplementary Statistics - Operating Statistics (Detail) bbl / d in Thousands, gal in Millions, CFPD in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2016 USD ($) Store CFPD bbl / d $ / bbl $ / gal gal	Mar. 31, 2015 USD ($) Store bbl / d $ / bbl $ / gal gal
Operating Statistics [Line Items ]
MPC Consolidated Refined Product Sales Volumes (thousands of barrels per day)	[1]	2,158	2,246
Refining & Marketing Operating Statistics
Inventory market valuation charge | $		$ 15	$ 0
Refining & Marketing
Refining & Marketing Operating Statistics
Refining & Marketing refined product sales volume (thousands of barrels per day)		2,148	2,233
Refining & Marketing gross margin (dollars per barrel) | $ / bbl	[2],[3]	9.98	16.14
Inventory market valuation charge | $		$ 15
Crude oil capacity utilization percent	[4]	89.00%	97.00%
Refinery throughputs (thousands of barrels per day)	[5]	1,774	1,852
Sour crude oil throughput percent		61.00%	56.00%
WTI-priced crude oil throughput percent		18.00%	20.00%
Refined product yields (thousands of barrels per day)	[5]	1,810	1,878
Inter-refinery transfers		82	35
Refinery direct operating costs (dollars per barrel):
Planned turnaround and major maintenance | $ / bbl	[6]	2.43	0.79
Depreciation and amortization | $ / bbl	[6]	1.54	1.42
Other manufacturing | $ / bbl	[6],[7]	4.14	4.26
Total | $ / bbl	[6]	8.11	6.47
Refining & Marketing | Crude oil refined
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[5]	1,603	1,672
Refining & Marketing | Other charge and blendstocks
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[5]	171	180
Refining & Marketing | Gasoline
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	899	911
Refining & Marketing | Distillates
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	571	553
Refining & Marketing | Propane
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	32	36
Refining & Marketing | Feedstocks and special products
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	234	298
Refining & Marketing | Heavy fuel oil
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	30	30
Refining & Marketing | Asphalt
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	44	50
Refining & Marketing | Gulf Coast:
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	1,208	1,210
Sour crude oil throughput percent		75.00%	70.00%
WTI-priced crude oil throughput percent		3.00%	5.00%
Refined product yields (thousands of barrels per day)	[8]	1,239	1,226
Refinery direct operating costs (dollars per barrel):
Planned turnaround and major maintenance | $ / bbl	[6]	2.62	0.80
Depreciation and amortization | $ / bbl	[6]	1.17	1.14
Other manufacturing | $ / bbl	[6],[7]	3.74	3.99
Total | $ / bbl	[6]	7.53	5.93
Refining & Marketing | Gulf Coast: | Crude oil refined
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	991	1,031
Refining & Marketing | Gulf Coast: | Other charge and blendstocks
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	217	179
Refining & Marketing | Gulf Coast: | Gasoline
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	533	523
Refining & Marketing | Gulf Coast: | Distillates
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	375	342
Refining & Marketing | Gulf Coast: | Propane
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	25	25
Refining & Marketing | Gulf Coast: | Feedstocks and special products
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	280	307
Refining & Marketing | Gulf Coast: | Heavy fuel oil
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	18	15
Refining & Marketing | Gulf Coast: | Asphalt
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	8	14
Refining & Marketing | Midwest:
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	648	677
Sour crude oil throughput percent		39.00%	34.00%
WTI-priced crude oil throughput percent		42.00%	43.00%
Refined product yields (thousands of barrels per day)	[8]	653	687
Refinery direct operating costs (dollars per barrel):
Planned turnaround and major maintenance | $ / bbl	[6]	1.76	0.73
Depreciation and amortization | $ / bbl	[6]	2.03	1.85
Other manufacturing | $ / bbl	[6],[7]	4.36	4.51
Total | $ / bbl	[6]	8.15	7.09
Refining & Marketing | Midwest: | Crude oil refined
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	612	641
Refining & Marketing | Midwest: | Other charge and blendstocks
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	36	36
Refining & Marketing | Midwest: | Gasoline
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	366	388
Refining & Marketing | Midwest: | Distillates
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	196	211
Refining & Marketing | Midwest: | Propane
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	9	13
Refining & Marketing | Midwest: | Feedstocks and special products
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	34	23
Refining & Marketing | Midwest: | Heavy fuel oil
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	12	16
Refining & Marketing | Midwest: | Asphalt
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	36	36
Speedway
Speedway Operating Statistics
Convenience stores at period-end | Store		2,771	2,753
Gasoline and distillate sales (millions of gallons) | gal		1,483	1,432
Gasoline and distillate gross margin (dollars per gallon) | $ / gal	[9]	0.1682	0.1970
Merchandise sales (in millions) | $		$ 1,152	$ 1,111
Merchandise gross margin (in millions) | $		$ 330	$ 311
Merchandise margin percent		29.00%	28.00%
Same store gasoline sales volume (period over period) percentage		1.00%	(1.20%)
Merchandise sales excluding cigarettes (period over period) percentage	[10]	3.10%	6.20%
Midstream
Midstream Operating Statistics
Crude oil and refined product pipeline throughputs (thousands of barrels per day)		2,181	2,107
Gathering system throughput (MMcf/d) | CFPD		3,345
Natural gas processed (MMcf/d) | CFPD		5,636
C2 and NGLs fractionated (thousands barrels per day)		312

[1] Total average daily volumes of refined product sales to wholesale, branded and retail (Speedway segment) customers.

[2] Excludes the lower of cost or market inventory valuation charge of $15 million for the first quarter of 2016.

[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 downtime for planned maintenance and other normal operating activities.

[5] Excludes inter-refinery volumes of 82 mbpd and 35 mbpd for the three months ended March 31, 2016 and 2015, respectively.

[6] Per barrel of total refinery throughputs.

[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 bankcard processing fees, divided by gasoline and distillate sales volume.

[10] Excludes cigarettes.