Supplementary Statistics (Operating Statistics) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 BPD		Dec. 31, 2012 BPD		Dec. 31, 2011 BPD
Operating Statistics [Line Items ]
MPC Consolidated Refined Product Sales Volumes (thousands of barrels per day)	2,086,000	[1],[2]	1,618,000	[1],[2]	1,599,000	[1],[2]
Refining & Marketing [Member]
Operating Statistics [Line Items ]
Refining & Marketing Refined Product Sales Volume (thousands of barrels per day)	2,075,000	[2],[3]	1,599,000	[2],[3]	1,581,000	[2],[3]
Refining & Marketing Gross Margin (dollars per barrel)	13.24	[2],[4]	17.85	[2],[4]	14.26	[2],[4]
Crude Oil Capacity Utilization percent	96.00%	[2],[5]	100.00%	[2],[5]	103.00%	[2],[5]
Refinery Throughputs (thousands of barrels per day):
Total	1,802,000	[2],[6]	1,363,000	[2],[6]	1,358,000	[2],[6]
Sour Crude Oil Throughput percent	53.00%	[2]	53.00%	[2]	52.00%	[2]
WTI-Priced Crude Oil Throughput percent	21.00%	[2]	28.00%	[2]	27.00%	[2]
Refined Product Yields (thousands of barrels per day):
Total	1,836,000	[2],[6]	1,386,000	[2],[6]	1,383,000	[2],[6]
Refinery Direct Operating Costs in Refining & Marketing Gross Margin (dollars per barrel): [Abstract]
Turnaround Maintenance And Engineered Project Expenses Per Barrel	1.20	[2],[7]	1.00	[2],[7]	0.78	[2],[7]
Depreciation and amortization	1.36	[2],[7]	1.44	[2],[7]	1.29	[2],[7]
Other Manufacturing Costs Per Barrel	4.14	[2],[7],[8]	3.15	[2],[7],[8]	3.16	[2],[7],[8]
Total	6.70	[2],[7]	5.59	[2],[7]	5.23	[2],[7]
Pipeline throughput (thousands of barrels per day)(h):
Inter-refinery transfers	36,000		25,000		28,000
Refining & Marketing [Member] | Gulf Coast [Member]
Refinery Throughputs (thousands of barrels per day):
Total	1,159,000	[2],[9]
Sour Crude Oil Throughput percent	65.00%	[2]
WTI-Priced Crude Oil Throughput percent	7.00%	[2]
Refined Product Yields (thousands of barrels per day):
Total	1,186,000	[2],[9]
Refinery Direct Operating Costs in Refining & Marketing Gross Margin (dollars per barrel): [Abstract]
Turnaround Maintenance And Engineered Project Expenses Per Barrel	1.00	[2],[7]
Depreciation and amortization	1.09	[2],[7]
Other Manufacturing Costs Per Barrel	3.98	[2],[7],[8]
Total	6.07	[2],[7]
Refining & Marketing [Member] | Midwest [Member]
Refinery Throughputs (thousands of barrels per day):
Total	679,000	[9]
Sour Crude Oil Throughput percent	35.00%
WTI-Priced Crude Oil Throughput percent	42.00%
Refined Product Yields (thousands of barrels per day):
Total	686,000	[9]
Refinery Direct Operating Costs in Refining & Marketing Gross Margin (dollars per barrel): [Abstract]
Turnaround Maintenance And Engineered Project Expenses Per Barrel	1.47	[7]
Depreciation and amortization	1.74	[7]
Other Manufacturing Costs Per Barrel	4.21	[7],[8]
Total	7.42	[7]
Refining & Marketing [Member] | Crude Oil [Member]
Refinery Throughputs (thousands of barrels per day):
Total	1,589,000	[2],[6]	1,195,000	[2],[6]	1,177,000	[2],[6]
Refining & Marketing [Member] | Crude Oil [Member] | Gulf Coast [Member]
Refinery Throughputs (thousands of barrels per day):
Total	964,000	[2],[9]
Refining & Marketing [Member] | Crude Oil [Member] | Midwest [Member]
Refinery Throughputs (thousands of barrels per day):
Total	625,000	[9]
Refining & Marketing [Member] | OtherChargeAndBlendstock [Member]
Refinery Throughputs (thousands of barrels per day):
Total	213,000	[2],[6]	168,000	[2],[6]	181,000	[2],[6]
Refining & Marketing [Member] | OtherChargeAndBlendstock [Member] | Gulf Coast [Member]
Refinery Throughputs (thousands of barrels per day):
Total	195,000	[2],[9]
Refining & Marketing [Member] | OtherChargeAndBlendstock [Member] | Midwest [Member]
Refinery Throughputs (thousands of barrels per day):
Total	54,000	[9]
Refining & Marketing [Member] | Gasoline [Member]
Refined Product Yields (thousands of barrels per day):
Total	921,000	[2],[6]	738,000	[2],[6]	739,000	[2],[6]
Refining & Marketing [Member] | Gasoline [Member] | Gulf Coast [Member]
Refined Product Yields (thousands of barrels per day):
Total	551,000	[2],[9]
Refining & Marketing [Member] | Gasoline [Member] | Midwest [Member]
Refined Product Yields (thousands of barrels per day):
Total	371,000	[9]
Refining & Marketing [Member] | Distillates [Member]
Refined Product Yields (thousands of barrels per day):
Total	572,000	[2],[6]	433,000	[2],[6]	433,000	[2],[6]
Refining & Marketing [Member] | Distillates [Member] | Gulf Coast [Member]
Refined Product Yields (thousands of barrels per day):
Total	365,000	[2],[9]
Refining & Marketing [Member] | Distillates [Member] | Midwest [Member]
Refined Product Yields (thousands of barrels per day):
Total	207,000	[9]
Refining & Marketing [Member] | Propane [Member]
Refined Product Yields (thousands of barrels per day):
Total	37,000	[2],[6]	26,000	[2],[6]	25,000	[2],[6]
Refining & Marketing [Member] | Propane [Member] | Gulf Coast [Member]
Refined Product Yields (thousands of barrels per day):
Total	23,000	[2],[9]
Refining & Marketing [Member] | Propane [Member] | Midwest [Member]
Refined Product Yields (thousands of barrels per day):
Total	14,000	[9]
Refining & Marketing [Member] | Feedstocks and Special Products [Member]
Refined Product Yields (thousands of barrels per day):
Total	221,000	[2],[6]	109,000	[2],[6]	109,000	[2],[6]
Refining & Marketing [Member] | Feedstocks and Special Products [Member] | Gulf Coast [Member]
Refined Product Yields (thousands of barrels per day):
Total	215,000	[2],[9]
Refining & Marketing [Member] | Feedstocks and Special Products [Member] | Midwest [Member]
Refined Product Yields (thousands of barrels per day):
Total	41,000	[9]
Refining & Marketing [Member] | Heavy Fuel Oil [Member]
Refined Product Yields (thousands of barrels per day):
Total	31,000	[2],[6]	18,000	[2],[6]	21,000	[2],[6]
Refining & Marketing [Member] | Heavy Fuel Oil [Member] | Gulf Coast [Member]
Refined Product Yields (thousands of barrels per day):
Total	19,000	[2],[9]
Refining & Marketing [Member] | Heavy Fuel Oil [Member] | Midwest [Member]
Refined Product Yields (thousands of barrels per day):
Total	12,000	[9]
Refining & Marketing [Member] | Asphalt [Member]
Refined Product Yields (thousands of barrels per day):
Total	54,000	[2],[6]	62,000	[2],[6]	56,000	[2],[6]
Refining & Marketing [Member] | Asphalt [Member] | Gulf Coast [Member]
Refined Product Yields (thousands of barrels per day):
Total	13,000	[2],[9]
Refining & Marketing [Member] | Asphalt [Member] | Midwest [Member]
Refined Product Yields (thousands of barrels per day):
Total	41,000	[9]
Speedway [Member]
Refinery Direct Operating Costs in Refining & Marketing Gross Margin (dollars per barrel): [Abstract]
Convenience stores at period-end (in number of stores)	1,478		1,464		1,371
Gasoline And Distillate Sales (in millions of gallons)	3,146,000,000		3,027,000,000		2,938,000,000
Gasoline And Distillate Gross Margin (in dollars per gallon)	0.1441	[10]	0.1318	[10]	0.1308	[10]
Merchandise sales (in millions)	$ 3,135		$ 3,058		$ 2,924
Merchandise gross margin (in millions)	$ 825		$ 795		$ 719
Same store gasoline sales volume percentage (period over period)	0.50%		(0.80%)		(1.70%)
Same store merchandise sales excluding cigarettes percentage (period over period)	4.30%	[11]	7.00%	[11]	6.70%	[11]
Pipeline Transportation [Member]
Pipeline throughput (thousands of barrels per day)(h):
Total	2,191,000	[12]	2,170,000	[12]	2,215,000	[12]
Pipeline Transportation [Member] | Crude Oil Pipelines [Member]
Pipeline throughput (thousands of barrels per day)(h):
Total	1,280,000	[12]	1,190,000	[12]	1,184,000	[12]
Pipeline Transportation [Member] | Refined Products Pipelines [Member]
Pipeline throughput (thousands of barrels per day)(h):
Total	911,000	[12]	980,000	[12]	1,031,000	[12]

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

[2] Includes the impact of the Galveston Bay Refinery and Related Assets beginning on the February 1, 2013 acquisition date.

[3] Includes intersegment sales.

[4] Sales revenue less cost of refinery inputs and purchased products, divided by total refinery throughputs. Starting in the fourth quarter of 2013, direct operating costs are no longer included in the Refining & Marketing gross margin and the gross margin is calculated based on total refinery throughput. All prior periods presented have been recalculated to reflect a consistent approach.

[5] Based on calendar day capacity, which is an annual average that includes downtime for planned maintenance and other normal operating activities.

[6] Excludes inter-refinery volumes of 36 thousand barrels per day ("mbpd"), 25 mbpd and 28 mbpd for 2013, 2012 and 2011, respectively

[7] Per barrel of total refinery throughputs.

[8] Includes utilities, labor, routine maintenance and other operating costs.

[9] Includes inter-refinery transfer volumes.

[10] 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.

[11] Excludes cigarettes.

[12] On owned common-carrier pipelines, excluding equity method investments.