Supplementary Statistics - Operating Statistics (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013 MBPD		Sep. 30, 2012 MBPD		Sep. 30, 2013 MBPD		Sep. 30, 2012 MBPD
Operating Statistics [Line Items ]
MPC Consolidated Refined Product Sales Volumes (thousands of barrels per day)	2,155,000	[1],[2]	1,622,000	[1],[2]	2,063,000	[1],[2]	1,590,000	[1],[2]
Refining & Marketing [Member]
Refining & Marketing Operating Statistics [Abstract]
Refinery Throughputs (thousands of barrels per day)	1,877,000	[2]	1,345,000	[2]	1,805,000	[2]	1,335,000	[2]
Crude Oil Capacity Utilization percent	99.00%	[2],[3]	99.00%	[2],[3]	97.00%	[2],[3]	99.00%	[2],[3]
Refined Product Yields (thousands of barrels per day)	1,915,000	[2]	1,375,000	[2]	1,839,000	[2]	1,359,000	[2]
Refining & Marketing Refined Product Sales Volume (thousands of barrels per day)	2,148,000	[2],[4]	1,605,000	[2],[4]	2,052,000	[2],[4]	1,569,000	[2],[4]
Refining & Marketing Gross Margin (dollars per barrel)	2.55	[2],[5]	13.12	[2],[5]	5.42	[2],[5]	10.92	[2],[5]
Refinery Direct Operating Costs in Refining & Marketing Gross Margin (dollars per barrel): [Abstract]
Turnaround and major maintenance	0.96	[2],[6]	1.18	[2],[6]	0.94	[2],[6]	1.04	[2],[6]
Depreciation and amortization	1.27	[2],[6]	1.44	[2],[6]	1.32	[2],[6]	1.40	[2],[6]
Other manufacturing	4.10	[2],[6],[7]	3.16	[2],[6],[7]	4.00	[2],[6],[7]	3.13	[2],[6],[7]
Total	6.33	[2],[6]	5.78	[2],[6]	6.26	[2],[6]	5.57	[2],[6]
Refining & Marketing [Member] | Crude Oil [Member]
Refining & Marketing Operating Statistics [Abstract]
Refinery Throughputs (thousands of barrels per day)	1,682,000	[2]	1,186,000	[2]	1,603,000	[2]	1,180,000	[2]
Refining & Marketing [Member] | OtherChargeAndBlendstock [Member]
Refining & Marketing Operating Statistics [Abstract]
Refinery Throughputs (thousands of barrels per day)	195,000	[2]	159,000	[2]	202,000	[2]	155,000	[2]
Refining & Marketing [Member] | Gasoline [Member]
Refining & Marketing Operating Statistics [Abstract]
Refined Product Yields (thousands of barrels per day)	938,000	[2]	728,000	[2]	917,000	[2]	723,000	[2]
Refining & Marketing [Member] | Distillates [Member]
Refining & Marketing Operating Statistics [Abstract]
Refined Product Yields (thousands of barrels per day)	578,000	[2]	439,000	[2]	570,000	[2]	420,000	[2]
Refining & Marketing [Member] | Propane [Member]
Refining & Marketing Operating Statistics [Abstract]
Refined Product Yields (thousands of barrels per day)	39,000	[2]	25,000	[2]	37,000	[2]	25,000	[2]
Refining & Marketing [Member] | Feedstocks and Special Products [Member]
Refining & Marketing Operating Statistics [Abstract]
Refined Product Yields (thousands of barrels per day)	259,000	[2]	95,000	[2]	227,000	[2]	109,000	[2]
Refining & Marketing [Member] | Heavy Fuel Oil [Member]
Refining & Marketing Operating Statistics [Abstract]
Refined Product Yields (thousands of barrels per day)	31,000	[2]	21,000	[2]	31,000	[2]	18,000	[2]
Refining & Marketing [Member] | Asphalt [Member]
Refining & Marketing Operating Statistics [Abstract]
Refined Product Yields (thousands of barrels per day)	70,000	[2]	67,000	[2]	57,000	[2]	64,000	[2]
Speedway [Member]
Speedway Operating Statistics
Convenience stores at period-end	1,471		1,463		1,471		1,463
Gasoline & distillate sales (millions of gallons)	803,000,000		779,000,000		2,329,000,000		2,241,000,000
Gasoline & distillate gross margin (dollars per gallon)	0.1404	[8]	0.1100	[8]	0.1483	[8]	0.1281	[8]
Merchandise sales (in millions)	$ 843		$ 826		$ 2,360		$ 2,297
Merchandise gross margin (in millions)	$ 224		$ 217		$ 620		$ 599
Same store gasoline sales volume (period over period)	1.00%		(3.90%)		0.60%		(1.10%)
Same store merchandise sales excluding cigarettes (period over period)	5.60%		4.10%		3.80%		8.00%
Pipeline Transportation [Member]
Pipeline Transportation Operating Statistics
Pipeline Throughputs (thousands of barrels per day)	2,230,000	[9]	2,180,000	[9]	2,238,000	[9]	2,122,000	[9]
Crude Oil Pipelines [Member] | Pipeline Transportation [Member]
Pipeline Transportation Operating Statistics
Pipeline Throughputs (thousands of barrels per day)	1,317,000	[9]	1,136,000	[9]	1,308,000	[9]	1,150,000	[9]
Refined Products Pipelines [Member] | Pipeline Transportation [Member]
Pipeline Transportation Operating Statistics
Pipeline Throughputs (thousands of barrels per day)	913,000	[9]	1,044,000	[9]	930,000	[9]	972,000	[9]

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

[4] Includes intersegment sales.

[5] Sales revenue less cost of refinery inputs, purchased products and refinery direct operating costs (including turnaround and major maintenance, depreciation and amortization and other manufacturing expenses), divided by Refining & Marketing segment refined product sales volume.

[6] Per barrel of total refinery throughputs.

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

[8] 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.

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