Marathon Petroleum (MPC) 10-Q 4 Aug 14 2014 Q2 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	6 Months Ended
	Jun. 30, 2014	Jul. 31, 2014
Document Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Jun-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus (Q1,Q2,Q3,FY)	'Q2	'
Trading Symbol	'MPC	'
Entity Registrant Name	'Marathon Petroleum Corp	'
Entity Central Index Key	'0001510295	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	283,325,153

Consolidated_Statements_of_Inc

Consolidated Statements of Income (USD $)	3 Months Ended		6 Months Ended
In Millions, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Revenues and other income:	'	'	'	'
Sales and other operating revenues (including consumer excise taxes)	$26,844	$25,677	$50,129	$49,007
Income from equity method investments	57	7	92	7
Net gain on disposal of assets	11	1	12	2
Other income	21	18	45	32
Total revenues and other income	26,933	25,703	50,278	49,048
Costs and expenses:	'	'	'	'
Cost of revenues (excludes items below)	23,096	22,320	43,636	42,354
Purchases from related parties	130	79	289	151
Consumer excise taxes	1,599	1,596	3,114	3,054
Depreciation and amortization	325	302	645	589
Selling, general and administrative expenses	316	358	662	607
Other taxes	98	88	202	177
Total costs and expenses	25,564	24,743	48,548	46,932
Income from operations	1,369	960	1,730	2,116
Net interest and other financial income (costs)	-48	-45	-94	-93
Income before income taxes	1,321	915	1,636	2,023
Provision for income taxes	457	316	565	694
Net income	864	599	1,071	1,329
Less net income attributable to noncontrolling interests	9	6	17	11
Net income attributable to MPC	$855	$593	$1,054	$1,318
Basic:	'	'	'	'
Net income attributable to MPC per share	$2.97	$1.84	$3.63	$4.03
Weighted average shares outstanding (in shares)	287	322	290	326
Diluted:	'	'	'	'
Net income attributable to MPC per share	$2.95	$1.83	$3.60	$4.01
Weighted average shares outstanding (in shares)	289	324	292	328
Dividends paid (in USD per share)	$0.42	$0.35	$0.84	$0.70

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement of Comprehensive Income [Abstract]	'	'	'	'
Net income	$864	$599	$1,071	$1,329
Defined benefit postretirement and post-employment plans:	'	'	'	'
Actuarial changes, net of tax of ($3), $81, $1 and $135	-5	135	2	225
Prior service costs, net of tax of ($4), ($4), ($9) and ($9)	-8	-7	-16	-15
Other comprehensive income (loss)	-13	128	-14	210
Comprehensive income	851	727	1,057	1,539
Less comprehensive income attributable to noncontrolling interests	9	6	17	11
Comprehensive income attributable to MPC	$842	$721	$1,040	$1,528

Consolidated_Statements_of_Com1

Consolidated Statements of Comprehensive Income (Parenthetical) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement of Comprehensive Income [Abstract]	'	'	'	'
Actuarial changes, tax	($3)	$81	$1	$135
Prior service costs, tax	($4)	($4)	($9)	($9)

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$2,125	$2,292
Receivables, less allowance for doubtful accounts of $9 and $9	5,725	5,559
Inventories	5,621	4,689
Other current assets	125	197
Total current assets	13,596	12,737
Equity method investments	690	463
Property, plant and equipment, net	13,850	13,921
Goodwill	937	938
Other noncurrent assets	303	326
Total assets	29,376	28,385
Current liabilities:	'	'
Accounts payable	8,934	8,234
Payroll and benefits payable	286	406
Consumer excise taxes payable	381	373
Accrued taxes	909	513
Long-term debt due within one year	26	23
Other current liabilities	519	275
Total current liabilities	11,055	9,824
Long-term debt	3,612	3,373
Deferred income taxes	2,170	2,304
Defined benefit postretirement plan obligations	906	771
Deferred credits and other liabilities	596	781
Total liabilities	18,339	17,053
Commitments and contingencies (see Note 20)	'	'
MPC stockholders’ equity:	'	'
Preferred stock, no shares issued and outstanding (par value $0.01 per share, 30 million shares authorized)	0	0
Common stock:	'	'
Issued - 363 million and 362 million shares (par value $0.01 per share, 1 billion shares authorized)	4	4
Held in treasury, at cost - 78 million and 65 million shares	-5,313	-4,155
Additional paid-in capital	9,822	9,768
Retained earnings	6,325	5,507
Accumulated other comprehensive loss	-218	-204
Total MPC stockholders’ equity	10,620	10,920
Noncontrolling interests	417	412
Total equity	11,037	11,332
Total liabilities and equity	$29,376	$28,385

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, except Share data, unless otherwise specified
Statement of Financial Position [Abstract]	'	'
Allowance for doubtful accounts	$9	$9
Preferred stock:	'	'
Shares issued	0	0
Shares outstanding	0	0
Par value	$0.01	'
Shares authorized	30,000,000	'
Common stock:	'	'
Shares issued	363,000,000	362,000,000
Par value	$0.01	'
Shares authorized	1,000,000,000	'
Treasury stock	-78,000,000	-65,000,000

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
Operating activities:	'	'
Net income	$1,071	$1,329
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation and amortization	645	589
Pension and other postretirement benefits, net	109	-42
Deferred income taxes	-91	34
Net gain on disposal of assets	-12	-2
Equity method investments, net	-44	3
Changes in the fair value of derivative instruments	-2	-57
Changes in:	'	'
Current receivables	-161	-1,539
Inventories	-923	-455
Current accounts payable and accrued liabilities	994	1,789
All other, net	58	-6
Net cash provided by operating activities	1,644	1,643
Investing activities:	'	'
Additions to property, plant and equipment	-569	-424
Acquisitions	-42	-1,515
Disposal of assets	17	9
Investments—acquisitions, loans and contributions	-164	-38
Investments—redemptions and repayments	3	28
All other, net	74	22
Net cash used in investing activities	-681	-1,918
Financing activities:	'	'
Long-term debt – borrowings	270	0
Long-term debt – repayments	-26	-10
Debt issuance costs	0	-2
Issuance of common stock	17	34
Common stock repurchased	-1,148	-1,313
Dividends paid	-245	-229
Distributions to noncontrolling interests	-12	-9
All other, net	14	13
Net cash used in financing activities	-1,130	-1,516
Net decrease in cash and cash equivalents	-167	-1,791
Cash and cash equivalents at beginning of period	2,292	4,860
Cash and cash equivalents at end of period	$2,125	$3,069

Consolidated_Statements_of_Equ

Consolidated Statements of Equity (USD $)		Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests
In Millions, unless otherwise specified
Beginning balance at Dec. 31, 2012		$12,105	$4	($1,253)	$9,527	$3,880	($464)	$411
Number of shares held in treasury (beginning balance) at Dec. 31, 2012		-28	'	'	'	'	'	'
Number of common shares issued (beginning balance) at Dec. 31, 2012		361	'	'	'	'	'	'
Increase (Decrease) in Stockholders' Equity [Roll Forward]		'	'	'	'	'	'	'
Net income		1,329	'	'	'	1,318	'	11
Dividends declared		-229	'	'	'	-229	'	'
Distributions to noncontrolling interests		-9	'	'	'	'	'	-9
Other comprehensive loss		210	'	'	'	'	210	'
Shares repurchased		-1,313	'	-1,413	100	'	'	'
Shares returned - stock based compensation		'	'	-6	'	'	'	'
Shares issued - stock based compensation		'	'	'	33	'	'	'
Net shares issued — stock based compensation		27	'	'	'	'	'	'
Stock-based compensation		38	'	'	38	'	'	0
Tax settlement with Marathon Oil Corporation		39	'	'	39	'	'	'
Number of shares issued - stock-based compensation		1	'	'	'	'	'	'
Number of shares repurchased		-17	'	'	'	'	'	'
Ending balance at Jun. 30, 2013		12,197	4	-2,672	9,737	4,969	-254	413
Number of shares held in treasury (ending balance) at Jun. 30, 2013		-45	'	'	'	'	'	'
Number of common shares issued (ending balance) at Jun. 30, 2013		362	'	'	'	'	'	'
Beginning balance at Dec. 31, 2013		11,332	4	-4,155	9,768	5,507	-204	412
Number of shares held in treasury (beginning balance) at Dec. 31, 2013		-65	'	'	'	'	'	'
Number of common shares issued (beginning balance) at Dec. 31, 2013		362	'	'	'	'	'	'
Increase (Decrease) in Stockholders' Equity [Roll Forward]		'	'	'	'	'	'	'
Net income		1,071	'	'	'	1,054	'	17
Dividends declared		-245	'	'	'	-245	'	'
Distributions to noncontrolling interests		-12	'	'	'	'	'	-12
Other comprehensive loss		-14	'	'	'	'	-14	'
Shares repurchased		-1,148	'	-1,148	0	'	'	'
Shares returned - stock based compensation		'	'	-10	'	'	'	'
Shares issued - stock based compensation		'	'	'	17	'	'	'
Net shares issued — stock based compensation		7	'	'	'	'	'	'
Stock-based compensation		37	'	'	37	'	'	0
Other		9	'	'	'	9	'	'
Number of shares issued - stock-based compensation		1	'	'	'	'	'	'
Number of shares repurchased	[1]	-13	'	'	'	'	'	'
Ending balance at Jun. 30, 2014		$11,037	$4	($5,313)	$9,822	$6,325	($218)	$417
Number of shares held in treasury (ending balance) at Jun. 30, 2014		-78	'	'	'	'	'	'
Number of common shares issued (ending balance) at Jun. 30, 2014		363	'	'	'	'	'	'
[1]	The six months ended June 30, 2013 includes one million shares received under the November 2012 accelerated share repurchase program, which were paid for in 2012.

Description_of_the_Business_an

Description of the Business and Basis of Presentation	6 Months Ended
	Jun. 30, 2014
Accounting Policies [Abstract]	'
Description of the Business and Basis of Presentation	'
	Description of the Business and Basis of Presentation
	Description of the Business—As used in this report, the terms “MPC,” “we,” “us,” “the Company” or “our” may refer to Marathon Petroleum Corporation, one or more of its consolidated subsidiaries or all of them taken as a whole.
	Our business consists of refining and marketing, retail marketing and pipeline transportation operations conducted primarily in the Midwest, Gulf Coast and Southeast regions of the United States, through subsidiaries, including Marathon Petroleum Company LP, Speedway LLC and MPLX LP and its subsidiaries (“MPLX”).
	See Note 8 for additional information about our operations.
	Basis of Presentation—All significant intercompany transactions and accounts have been eliminated.
	These interim consolidated financial statements are unaudited; however, in the opinion of our management, these statements reflect all adjustments necessary for a fair statement of the results for the periods reported. All such adjustments are of a normal, recurring nature unless otherwise disclosed. These interim consolidated financial statements, including the notes, have been prepared in accordance with the rules of the Securities and Exchange Commission applicable to interim period financial statements and do not include all of the information and disclosures required by United States generally accepted accounting principles (“U.S. GAAP”) for complete financial statements.
	These interim consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2013. The results of operations for the three and six months ended June 30, 2014 are not necessarily indicative of the results to be expected for the full year.
	During the first quarter of 2014, we recorded an out-of-period adjustment for additional expenses related to the prior year's bonus programs of $29 million, included in total costs and expenses on the consolidated statements of income. The impact to our consolidated results of operations for the six months ended June 30, 2014 and for the year ended December 31, 2013 was immaterial. We do not expect this adjustment to have a material impact to our results of operations for the year ended December 31, 2014.

Accounting_Standards

Accounting Standards	6 Months Ended
	Jun. 30, 2014
Accounting Changes and Error Corrections [Abstract]	'
Accounting Standards	'
	Accounting Standards
	Not Yet Adopted
	In June 2014, the Financial Accounting Standards Board ("FASB") issued an accounting standards update for the elimination of the concept of development stage entity ("DSE") from U.S. GAAP and removes the related incremental reporting. The standards update eliminates the additional financial statement requirements specific to a DSE. In addition, it amends the consolidation model by eliminating the special provisions in the variable interest entity rules for assessing the sufficiency of the equity of a DSE. The portion of the accounting standards update related to the amendment to the consolidation guidance will be effective on a retrospective basis for annual reporting periods beginning after December 15, 2015, and interim periods within those years, with early adoption permitted. The portion of the accounting standards update related to the removal of the DSE reporting requirements will be effective on a retrospective basis for annual reporting periods beginning after December 15, 2014, and interim periods within those years, with early adoption permitted. Adoption of this standards update in the first quarters of 2015 and 2016 is not expected to have an impact on our consolidated results of operations, financial position or cash flows.
	In May 2014, the FASB issued an accounting standards update for revenue recognition that is aligned with the International Accounting Standards Board's revenue recognition standard issued on the same day. The guidance in the update states that revenue is recognized when a customer obtains control of a good or service. Recognition of the revenue will involve a multiple step approach including identifying the contract, identifying the separate performance obligations, determining the transaction price, allocating the price to the performance obligations and then recognizing the revenue as the obligations are satisfied. Additional disclosures will be required to provide adequate information to understand the nature, amount, timing and uncertainty of reported revenues and revenues expected to be recognized. The accounting standards update will be effective on a retrospective or modified retrospective basis for annual reporting periods beginning after December 15, 2016, and interim periods within those years, with no early adoption permitted. At this point, a final determination has not been made as to the impact of the adoption of this standards update in the first quarter of 2017. However, we do not expect it to have a material impact on our consolidated results of operations, financial position or cash flows.
	In April 2014, the FASB issued an accounting standards update that redefines the criteria for determining discontinued operations and introduces new disclosures related to these disposals. The updated definition of a discontinued operation is the disposal of a component(s) of an entity or the classification of a component(s) of an entity as held for sale that represents a strategic shift for an entity and has (or will have) a major impact on an entity's operations and financial results. The standard requires disclosure of additional financial information for discontinued operations and individually material components not qualifying for discontinued operation presentation, as well as information regarding an entity's continuing involvement with the discontinued operation. The accounting standards update is effective prospectively for annual periods beginning on or after December 15, 2014, and interim periods within those years. Early adoption is permitted. Adoption of this standards update in the first quarter of 2015 is not expected to have an impact on our consolidated results of operations, financial position or cash flows.

MPLX_LP

MPLX LP	6 Months Ended
	Jun. 30, 2014
Noncontrolling Interest [Abstract]	'
MPLX LP	'
	MPLX LP
	MPLX is a publicly traded master limited partnership that was formed by us to own, operate, develop and acquire pipelines and other midstream assets related to the transportation and storage of crude oil, refined products and other hydrocarbon-based products. We own a 73.6 percent interest in MPLX, including the two percent general partner interest. We consolidate this entity for financial reporting purposes since we have a controlling financial interest, and we record a noncontrolling interest for the interest owned by the public.
	MPLX’s initial assets consisted of a 51 percent general partner interest in MPLX Pipe Line Holdings LP (“Pipe Line Holdings”), which owns a network of common carrier crude oil and product pipeline systems and associated storage assets in the Midwest and Gulf Coast regions of the United States, and a 100 percent interest in a butane storage cavern in West Virginia. On May 1, 2013, we sold a five percent interest in Pipe Line Holdings to MPLX for $100 million.
	Effective March 1, 2014, we sold MPLX a 13 percent interest in Pipe Line Holdings for $310 million, increasing MPLX's ownership interest in Pipe Line Holdings to 69 percent. MPLX financed this transaction with $40 million of cash on-hand and $270 million of borrowings on its bank revolving credit agreement.
	The sales of interests in Pipeline Holdings to MPLX resulted in a change of our ownership in Pipeline Holdings, but not a change in control. We accounted for the sales as equity transactions, with the excess cash paid over historical carrying value recorded as a change within equity. We did not record a gain or loss on the transactions.

Acquisitions_and_Investments

Acquisitions and Investments	6 Months Ended
	Jun. 30, 2014
Business Combinations [Abstract]	'
Acquisitions and Investments	'
	Acquisitions and Investments
	Acquisition of Refinery and Related Logistics and Marketing Assets
	On February 1, 2013, we acquired from BP Products North America Inc. and BP Pipelines (North America) Inc. (collectively, “BP”) the 451,000 barrel per calendar day refinery in Texas City, Texas, three intrastate natural gas liquid pipelines originating at the refinery, four light product terminals, branded-jobber marketing contract assignments for the supply of approximately 1,200 branded sites, a 1,040 megawatt electric cogeneration facility and a 50,000 barrel per day allocation of space on Colonial Pipeline. We refer to these assets as the “Galveston Bay Refinery and Related Assets.” We paid $1.49 billion for these assets, which included $935 million for inventory. The transaction was funded with cash on hand. Pursuant to the purchase and sale agreement, we may also be required to pay to BP a contingent earnout of up to an additional $700 million over six years, subject to certain conditions. In July 2014, we paid BP $180 million for the first period's contingent earnout. See Note 13 for additional information on the contingent consideration.
	The following unaudited pro forma financial information presents consolidated results assuming the Galveston Bay Refinery and Related Assets acquisition occurred on January 1, 2012. The pro forma financial information does not give effect to potential synergies that could result from the acquisition and is not necessarily indicative of the results of future operations.
	(In millions, except per share data)	Six Months Ended June 30, 2013
	Sales and other operating revenues (including consumer excise taxes)	$	50,975
	Net income attributable to MPC	1,373
	Net income attributable to MPC per share - basic	$	4.21
	Net income attributable to MPC per share - diluted	4.19
	The pro forma information includes adjustments to align accounting policies, an adjustment to depreciation expense to reflect the fair value of property, plant and equipment, increased amortization expense related to identifiable intangible assets and the related income tax effects.
	Pending Acquisition of Hess Retail Holdings LLC
	On May 21, 2014, Speedway entered into a purchase and sale agreement with Hess Corporation to purchase Hess Retail Holdings LLC ("Hess Retail"). This acquisition will incorporate all of Hess' retail locations, transport operations and shipper history on various pipelines, including approximately 40,000 barrels per day on Colonial Pipeline. The total consideration is $2.874 billion comprised of a cash purchase price of $2.37 billion, an estimated $230 million of net working capital and $274 million of capital lease obiligations. The acquisition is expected to be funded with a combination of debt and available cash and is anticipated to close later this year, subject to customary closing conditions.
	This acquisition will significantly expand our Speedway presence from nine to 23 states throughout the East Coast and Southeast and is aligned with our strategy to grow higher-valued, stable cash flow businesses. This acquisition will also enable us to further leverage our integrated refining and transportation operations, providing an outlet for an incremental 200,000 barrels per day of assured sales from our refining system.
	Acquisitions of Convenience Stores
	During 2013, Speedway acquired nine convenience stores located in Tennessee, western Indiana and western Pennsylvania. In connection with these acquisitions, our Speedway segment recorded $8 million of goodwill, which is deductible for income tax purposes.
	The principal factors contributing to a purchase price resulting in goodwill included the acquired stores complementing our existing network in our Midwest market, access to our refined product transportation systems and the potential for higher merchandise sales.
	Acquisition of Biodiesel Facility
	On April 1, 2014, we purchased a facility in Cincinnati, Ohio from Felda Iffco Sdn Bhd, Malaysia for $40 million. The plant currently produces biodiesel, glycerin and other by-products. The capacity of the plant is approximately 60 million gallons per year.
	Neither goodwill nor a gain from a bargain purchase was recognized in conjunction with the biodiesel facility acquisition.
	Assuming the acquisitions of the convenience stores and the biodiesel facility had been made at the beginning of any period presented, the consolidated pro forma results would not be materially different from reported results.
	Investments in Ethanol Companies
	On August 1, 2013, we acquired from Mitsui & Co. (U.S.A.), Inc. its interests in three ethanol companies for $75 million. Under the purchase agreement, we acquired an additional 24 percent interest in The Andersons Clymers Ethanol LLC ("TACE"), bringing our ownership interest to 60 percent; a 34 percent interest in The Andersons Ethanol Investment LLC, which holds a 50 percent ownership in The Andersons Marathon Ethanol LLC ("TAME"), bringing our direct and indirect ownership interest in TAME to 67 percent; and a 40 percent interest in The Andersons Albion Ethanol LLC ("TAAE"), which owns an ethanol production facility in Albion, Michigan. On October 1, 2013, our ownership interest in TAAE increased to 43 percent as a result of TAAE acquiring one of the owner's interest. We hold a noncontrolling interest in each of these entities and account for them using the equity method of accounting since the minority owners have substantive participating rights.
	Investments in Pipeline Companies
	We made contributions of $75 million to North Dakota Pipeline Company LLC ("North Dakota Pipeline") during the six months ended June 30, 2014. We have contributed $99 million since project inception. These contributions funded 37.5 percent of the construction costs incurred to-date on the Sandpiper pipeline project. In conjunction with our commitment to be an anchor shipper for the Sandpiper pipeline and our investment in the project, we will earn an approximate 27 percent equity interest in Enbridge Energy Partner L.P.'s North Dakota System when the Sandpiper pipeline is placed into service, which is projected to occur in early 2016. We also have the option to increase our ownership interest to approximately 30 percent through additional investments in future system improvements. We account for our interest in North Dakota Pipeline using the equity method of accounting. See Note 20 for information on future contributions to North Dakota Pipeline.
	In March 2014, we acquired from Chevron Raven Ridge Pipe Line Company an additional seven percent interest in Explorer Pipeline Company ("Explorer") for $77 million, bringing our ownership interest to 25 percent. As a result of this increase in our ownership, we now account for our investment in Explorer using the equity method of accounting rather than the cost method. The cumulative impact of the change was applied as an adjustment to 2014 retained earnings.

Related_Party_Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2014
Related Party Transactions [Abstract]	'
Related Party Transactions	'
	Related Party Transactions
	Our related parties include:
	•	TAAE, in which we have a 43 percent noncontrolling interest, TACE, in which we have a 60 percent noncontrolling interest and TAME, in which we have a 67 percent direct and indirect noncontrolling interest. These companies each own an ethanol production facility.
	•	Centennial Pipeline LLC (“Centennial”), in which we have a 50 percent noncontrolling interest. Centennial owns a refined products pipeline and storage facility.
	•	Explorer, in which we have a 25 percent interest. Explorer owns and operates a refined products pipeline.
	•	LOCAP LLC ("LOCAP"), in which we have a 59 percent noncontrolling interest. LOCAP owns and operates a crude oil pipeline.
	•	LOOP LLC (“LOOP”), in which we have a 51 percent noncontrolling interest. LOOP owns and operates the only U.S. deepwater oil port.
	•	Other equity method investees.
	Sales to related parties, which are included in sales and other operating revenues (including consumer excise taxes) on the consolidated statements of income, were as follows:
		Three Months Ended					Six Months Ended
		June 30,					June 30,
	(In millions)	2014			2013		2014		2013
	Other equity method investees	$	2		$	2	$	4	$	4
	Fees received for operating Centennial's pipeline, which are included in other income on the consolidated statements of income, were $1 million for the three and six months ended June 30, 2014 and 2013.
	Purchases from related parties were as follows:
		Three Months Ended					Six Months Ended
		June 30,					June 30,
	(In millions)	2014			2013		2014		2013
	Centennial	$	(2	)	$	—	$	7	$	—
	Explorer	9			—		22		—
	LOCAP	5			4		10		8
	LOOP	12			11		65		21
	TAAE	26			—		42		—
	TACE	30			24		57		50
	TAME	48			37		82		67
	Other equity method investees	2			3		4		5
	Total	$	130		$	79	$	289	$	151
	Related party purchases from Centennial consist primarily of refinery feedstocks and refined product transportation costs. Related party purchases from Explorer consist primarily of refined product transportation costs. Related party purchases from LOCAP, LOOP and other equity method investees consist primarily of crude oil transportation costs and crude oil purchases. Related party purchases from TAAE, TACE and TAME consist of ethanol purchases.
	Receivables from related parties, which are included in receivables, less allowance for doubtful accounts on the consolidated balance sheets, were as follows:
	(In millions)	June 30,			December 31,
		2014			2013
	Centennial	$	1		$	1
	TAME	2			1
	Total	$	3		$	2
	We also had a long-term receivable from Centennial of $2 million at June 30, 2014 and December 31, 2013, which is included in other noncurrent assets on the consolidated balance sheets.
	Payables to related parties, which are included in accounts payable on the consolidated balance sheets, were as follows:
	(In millions)	June 30,			December 31,
		2014			2013
	Explorer	$	3		$	—
	LOCAP	1			2
	LOOP	4			3
	TAAE	3			2
	TACE	2			4
	TAME	4			5
	Other equity method investees	1			—
	Total	$	18		$	16

Income_per_Common_Share

Income per Common Share	6 Months Ended
	Jun. 30, 2014
Earnings Per Share [Abstract]	'
Income per Common Share	'
	Income per Common Share
	We compute basic earnings per share by dividing net income attributable to MPC by the weighted average number of shares of common stock outstanding. Diluted income per share assumes exercise of certain stock-based compensation awards, provided the effect is not anti-dilutive.
	MPC grants certain incentive compensation awards to employees and non-employee directors that are considered to be participating securities. Due to the presence of participating securities, we have calculated our earnings per share using the two-class method.
		Three Months Ended						Six Months Ended
		June 30,						June 30,
	(In millions, except per share data)	2014			2013			2014		2013
	Basic earnings per share:
	Allocation of earnings:
	Net income attributable to MPC	$	855		$	593		$	1,054	$	1,318
	Income allocated to participating securities	1			1			2		2
	Income available to common stockholders - basic	$	854		$	592		$	1,052	$	1,316
	Weighted average common shares outstanding	287			322			290		326
	Basic earnings per share	$	2.97		$	1.84		$	3.63	$	4.03
	Diluted earnings per share:
	Allocation of earnings:
	Net income attributable to MPC	$	855		$	593		$	1,054	$	1,318
	Income allocated to participating securities	1			1			2		2
	Income available to common stockholders - diluted	$	854		$	592		$	1,052	$	1,316
	Weighted average common shares outstanding	287			322			290		326
	Effect of dilutive securities	2			2			2		2
	Weighted average common shares, including dilutive effect	289			324			292		328
	Diluted earnings per share	$	2.95		$	1.83		$	3.6	$	4.01
	The following table summarizes the shares that were anti-dilutive and, therefore, were excluded from the diluted share calculation.
		Three Months Ended					Six Months Ended
		June 30,					June 30,
	(In millions)	2014		2013			2014		2013
	Shares issued under stock-based compensation plans	—		1			—		1

Equity

Equity	6 Months Ended
	Jun. 30, 2014
Equity [Abstract]	'
Equity	'
	Equity
	As of June 30, 2014, our board of directors had approved $6.0 billion in total share repurchase authorizations since January 1, 2012 and we have repurchased a total of $5.29 billion of our common stock, leaving $709 million available for repurchases through September 2015. Under these authorizations, we have acquired 78 million shares at an average cost per share of $67.65. On July 30, 2014, our board of directors approved an additional $2.0 billion share repurchase authorization expiring in July 2016.
	We may utilize various methods to effect the repurchases, which could include open market repurchases, negotiated block transactions, accelerated share repurchases or open market solicitations for shares, some of which may be effected through Rule 10b5-1 plans. The timing and amount of future repurchases, if any, will depend upon several factors, including market and business conditions, and such repurchases may be discontinued at any time.
	Total share repurchases were as follows for the three and six months ended June 30, 2014 and 2013:
		Three Months Ended				Six Months Ended
		June 30,				June 30,
	(In millions, except per share data)	2014		2013		2014		2013
	Number of shares repurchased(a)	5		11		13		17
	Cash paid for shares repurchased	$	459	$	882	$	1,148	$	1,313
	Effective average cost per delivered share	$	88.14	$	80.31	$	87.82	$	80.54
	(a)	The six months ended June 30, 2013 includes one million shares received under the November 2012 accelerated share repurchase program, which were paid for in 2012.
	At June 30, 2014, we had agreements to acquire additional common shares for $12 million, which were settled in early July 2014.

Segment_Information

Segment Information	6 Months Ended
	Jun. 30, 2014
Segment Reporting [Abstract]	'
Segment Information	'
	Segment Information
	We have three reportable segments: Refining & Marketing; Speedway; and Pipeline Transportation. Each of these segments is organized and managed based upon the nature of the products and services it offers.
	•	Refining & Marketing – refines crude oil and other feedstocks at our refineries in the Gulf Coast and Midwest regions of the United States, purchases ethanol and refined products for resale and distributes refined products through various means, including barges, terminals and trucks that we own or operate. We sell refined products to wholesale marketing customers domestically and internationally, to buyers on the spot market, to our Speedway segment and to independent entrepreneurs who operate Marathon® retail outlets;
	•	Speedway – sells transportation fuels and convenience products in retail markets in the Midwest, primarily through Speedway® convenience stores; and
	•	Pipeline Transportation – transports crude oil and other feedstocks to our refineries and other locations, delivers refined products to wholesale and retail market areas and includes the aggregated operations of MPLX and MPC’s retained pipeline assets and investments.
	On February 1, 2013, we acquired the Galveston Bay Refinery and Related Assets, which are part of the Refining & Marketing and Pipeline Transportation segments. Segment information for the period prior to the acquisition does not include amounts for these operations. See Note 4.
	Segment income represents income from operations attributable to the reportable segments. Corporate administrative expenses and costs related to certain non-operating assets are not allocated to the reportable segments. In addition, certain items that affect comparability (as determined by the chief operating decision maker) are not allocated to the reportable segments.
	(In millions)	Refining & Marketing			Speedway			Pipeline Transportation			Total
	Three Months Ended June 30, 2014
	Revenues:
	Customer	$	22,917		$	3,908		$	19		$	26,844
	Intersegment(a)	2,590			1			131			2,722
	Segment revenues	$	25,507		$	3,909		$	150		$	29,566
	Segment income from operations(b)	$	1,260		$	94		$	81		$	1,435
	Income from equity method investments	35			—			22			57
	Depreciation and amortization(c)	264			29			19			312
	Capital expenditures and investments(d)	235			44			64			343
	(In millions)	Refining & Marketing			Speedway			Pipeline Transportation			Total
	Three Months Ended June 30, 2013
	Revenues:
	Customer	$	21,890		$	3,768		$	19		$	25,677
	Intersegment(a)	2,434			1			119			2,554
	Segment revenues	$	24,324		$	3,769		$	138		$	28,231
	Segment income from operations(b)	$	903		$	123		$	58		$	1,084
	Income from equity method investments	3			—			4			7
	Depreciation and amortization(c)	252			27			18			297
	Capital expenditures and investments(d)	134			76			41			251
	(In millions)	Refining & Marketing			Speedway			Pipeline Transportation			Total
	Six Months Ended June 30, 2014
	Revenues:
	Customer	$	42,727		$	7,366		$	36		$	50,129
	Intersegment(a)	4,823			2			260			5,085
	Segment revenues	$	47,550		$	7,368		$	296		$	55,214
	Segment income from operations(b)	$	1,622		$	152		$	153		$	1,927
	Income from equity method investments	59			—			33			92
	Depreciation and amortization(c)	525			57			38			620
	Capital expenditures and investments(d)	413			76			194			683
	(In millions)	Refining & Marketing			Speedway			Pipeline Transportation			Total
	Six Months Ended June 30, 2013
	Revenues:
	Customer	$	41,764		$	7,209		$	40		$	49,013
	Intersegment(a)	4,633			2			223			4,858
	Segment revenues	$	46,397		$	7,211		$	263		$	53,871
	Segment income from operations(b)	$	2,008		$	190		$	109		$	2,307
	Income (loss) from equity method investments	(1		)	—			8			7
	Depreciation and amortization(c)	488			54			36			578
	Capital expenditures and investments(d)(e)	1,554			112			131			1,797
	(a)	Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties.
	(b)	Corporate overhead expenses attributable to MPLX are included in the Pipeline Transportation segment. These expenses are not allocated to the Refining & Marketing and Speedway segments.
	(c)	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.
	(d)	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
	(e)	The Refining & Marketing and Pipeline Transportation segments include the acquisition of the Galveston Bay Refinery and Related Assets. See Note 4.
	The following reconciles segment income from operations to income before income taxes as reported in the consolidated statements of income:
		Three Months Ended						Six Months Ended
		June 30,						June 30,
	(In millions)	2014			2013			2014			2013
	Segment income from operations	$	1,435		$	1,084		$	1,927		$	2,307
	Items not allocated to segments:
	Corporate and other unallocated items(a)(b)	(61		)	(64		)	(128		)	(131		)
	Pension settlement expenses(c)	(5		)	(60		)	(69		)	(60		)
	Net interest and other financial income (costs)	(48		)	(45		)	(94		)	(93		)
	Income before income taxes	$	1,321		$	915		$	1,636		$	2,023
	(a)	Corporate and other unallocated items consists primarily of MPC’s corporate administrative expenses and costs related to certain non-operating assets.
(b)	Corporate overhead expenses attributable to MPLX are included in the Pipeline Transportation segment. These expenses are not allocated to the Refining & Marketing and Speedway segments.
(c)	See Note 18.
The following reconciles segment capital expenditures and investments to total capital expenditures:
	Three Months Ended						Six Months Ended
	June 30,						June 30,
(In millions)	2014			2013			2014			2013
Segment capital expenditures and investments	$	343		$	251		$	683		$	1,797
Less: Investments in equity method investees	41			6			164			11
Plus: Items not allocated to segments:
Capital expenditures not allocated to segments	13			28			38			52
Capitalized interest	7			4			13			8
Total capital expenditures(a)(b)	$	322		$	277		$	570		$	1,846
(a)	Capital expenditures include changes in capital accruals and acquisitions.
(b)	See Note 16 for a reconciliation of total capital expenditures to additions to property, plant and equipment as reported in the consolidated statements of cash flows.
The following reconciles customer revenues to sales and other operating revenues (including consumer excise taxes) as reported in the consolidated statements of income:
	Three Months Ended						Six Months Ended
	June 30,						June 30,
(In millions)	2014			2013			2014			2013
Customer revenues (as reported above)	$	26,844		$	25,677		$	50,129		$	49,013
Corporate and other unallocated items	—			—			—			(6		)
Sales and other operating revenues (including consumer excise taxes)	$	26,844		$	25,677		$	50,129		$	49,007
Total assets by reportable segment were:
(In millions)	June 30,			December 31, 2013
	2014
Refining & Marketing	$	20,708		$	19,573
Speedway	2,185			2,064
Pipeline Transportation	2,135			1,947
Corporate and Other	4,348			4,801
Total consolidated assets	$	29,376		$	28,385

Other_Items

Other Items	6 Months Ended
	Jun. 30, 2014
Other Income and Expenses [Abstract]	'
Other Items	'
	Other Items
	Net interest and other financial income (costs) was:
		Three Months Ended						Six Months Ended
		June 30,						June 30,
	(In millions)	2014			2013			2014			2013
	Interest:
	Interest income	$	1		$	3		$	3		$	5
	Interest expense	(49		)	(49		)	(98		)	(97		)
	Interest capitalized	7			4			13			8
	Total net interest	(41		)	(42		)	(82		)	(84		)
	Other:
	Net foreign currency gains (losses)	(1		)	2			(1		)	1
	Bank service and other fees	(6		)	(5		)	(11		)	(10		)
	Total other	(7		)	(3		)	(12		)	(9		)
	Net interest and other financial income (costs)	$	(48	)	$	(45	)	$	(94	)	$	(93	)

Income_Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2014
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	Income Taxes
	The combined federal, state and foreign income tax rate was 35 percent for both the three months ended June 30, 2014 and 2013 and 35 percent and 34 percent for the six months ended June 30, 2014 and 2013, respectively. The effective tax rate for the three and six months ended June 30, 2014 and 2013 is equivalent to or slightly less than the U.S. statutory rate of 35 percent primarily due to certain permanent benefit differences, including the domestic manufacturing deduction, partially offset by state and local tax expense.
	Prior to the June 30, 2011 spinoff transaction from Marathon Oil Corporation (“Marathon Oil”), we were included in Marathon Oil’s income tax returns for all applicable years. During 2011, we anticipated a future settlement between Marathon Oil and us upon the filing of Marathon Oil’s consolidated U.S. federal and state income tax returns for the period prior to June 30, 2011. During the second quarter of 2013, we settled with Marathon Oil for the 2011 period based on filed tax returns, resulting in a $39 million increase to additional paid-in capital.
	We are continuously undergoing examination of our income tax returns, which have been completed for our U.S. federal and state income tax returns through the 2009 and 2003 tax years, respectively. We had $20 million of unrecognized tax benefits as of June 30, 2014. Pursuant to our tax sharing agreement with Marathon Oil, the unrecognized tax benefits related to pre-spinoff operations for which Marathon Oil was the taxpayer remain the responsibility of Marathon Oil and we have indemnified Marathon Oil accordingly. See Note 20 for indemnification information.

Inventories

Inventories	6 Months Ended
	Jun. 30, 2014
Inventory Disclosure [Abstract]	'
Inventories	'
	Inventories
	(In millions)	June 30,		December 31,
		2014		2013
	Crude oil and refinery feedstocks	$	2,835	$	1,797
	Refined products	2,367		2,367
	Materials and supplies	333		425
	Merchandise	86		100
	Total (at cost)	$	5,621	$	4,689
	Inventories are carried at the lower of cost or market value. The cost of inventories of crude oil and refinery feedstocks, refined products and merchandise is determined primarily under the last-in, first-out (“LIFO”) method. There were no liquidations of LIFO inventories for the six months ended June 30, 2014 and 2013.

Property_Plant_and_Equipment

Property, Plant and Equipment	6 Months Ended
	Jun. 30, 2014
Property, Plant and Equipment [Abstract]	'
Property, Plant and Equipment	'
	Property, Plant and Equipment
	(In millions)	June 30,		December 31,
		2014		2013
	Refining & Marketing	$	17,329	$	16,982
	Speedway	2,412		2,344
	Pipeline Transportation	1,948		1,921
	Corporate and Other	588		546
	Total	22,277		21,793
	Less accumulated depreciation	8,427		7,872
	Property, plant and equipment, net	$	13,850	$	13,921

Fair_Value_Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2014
Fair Value Disclosures [Abstract]	'
Fair Value Measurements	'
	Fair Value Measurements
	Fair Values—Recurring
	The following tables present assets and liabilities accounted for at fair value on a recurring basis as of June 30, 2014 and December 31, 2013 by fair value hierarchy level. We have elected to offset the fair value amounts recognized for multiple derivative contracts executed with the same counterparty, including any related cash collateral as shown below; however, fair value amounts by hierarchy level are presented on a gross basis in the following tables.
		June 30, 2014
		Fair Value Hierarchy
	(In millions)	Level 1		Level 2		Level 3		Netting and Collateral(a)			Net Carrying Value on Balance Sheet(b)		Collateral Pledged Not Offset
	Commodity derivative instruments, assets	$	44	$	—	$	—	$	(44	)	$	—	$	60
	Other assets	2		—		—		N/A			2		—
	Total assets at fair value	$	46	$	—	$	—	$	(44	)	$	2	$	60
	Commodity derivative instruments, liabilities	$	91	$	—	$	—	$	(91	)	$	—	$	—
	Contingent consideration, liability(c)	—		—		647		N/A			647		—
	Total liabilities at fair value	$	91	$	—	$	647	$	(91	)	$	647	$	—
		December 31, 2013
		Fair Value Hierarchy
	(In millions)	Level 1		Level 2		Level 3		Netting and Collateral(a)			Net Carrying Value on Balance Sheet(b)		Collateral Pledged Not Offset
	Commodity derivative instruments, assets	$	21	$	—	$	—	$	(21	)	$	—	$	61
	Other assets	2		—		—		N/A			2		—
	Total assets at fair value	$	23	$	—	$	—	$	(21	)	$	2	$	61
	Commodity derivative instruments, liabilities	$	53	$	—	$	—	$	(53	)	$	—	$	—
	Contingent consideration, liability(c)	—		—		625		N/A			625		—
	Total liabilities at fair value	$	53	$	—	$	625	$	(53	)	$	625	$	—
	(a)	Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of June 30, 2014 and December 31, 2013, cash collateral of $47 million and $32 million, respectively, was netted with mark-to-market derivative liabilities.
	(b)	We have no derivative contracts that are subject to master netting arrangements that are reflected gross on the balance sheet.
	(c)	Includes $370 million and $159 million classified as current at June 30, 2014 and December 31, 2013, respectively.
	Commodity derivatives in Level 1 are exchange-traded contracts for crude oil and refined products measured at fair value with a market approach using the close-of-day settlement prices for the market. Commodity derivatives are covered under master netting agreements with an unconditional right to offset. Collateral deposits in futures commission merchant accounts covered by master netting agreements related to Level 1 commodity derivatives are classified as Level 1 in the fair value hierarchy.
	The contingent consideration represents the fair value as of June 30, 2014 of the amount we expect to pay to BP related to the earnout provision for the Galveston Bay Refinery and Related Assets acquisition. See Note 4. The fair value of the contingent consideration was estimated using an income approach and is therefore a Level 3 liability. The amount of cash to be paid under the arrangement is based on both a market-based crack spread and refinery throughput volumes for the months during which the contract applies, as well as established thresholds that cap the annual and total payment. The earnout payment cannot exceed $200 million per year for the first three years of the arrangement or $250 million per year for the last three years of the arrangement, with the total cumulative payment capped at $700 million over the six-year period. Any excess or shortfall from the annual cap for a current year’s earnout calculation will not affect subsequent years’ calculations. The fair value calculation used significant unobservable inputs, including (1) an estimate of refinery throughput volumes; (2) a range of internal and external crack spread forecasts from $14 to $19 per barrel; and (3) a range of risk-adjusted discount rates from five percent to 10 percent. An increase or decrease in crack spread forecasts or refinery throughput volume expectations may result in a corresponding increase or decrease in the fair value. Increases to the fair value as a result of increasing forecasts for both of these unobservable inputs, however, are limited as the earnout payment is subject to annual thresholds. An increase or decrease in the discount rate may result in a decrease or increase to the fair value, respectively. The fair value of the contingent consideration is reassessed each quarter, with changes in fair value recorded in cost of revenues.
	The following is a reconciliation of the beginning and ending balances recorded for liabilities classified as Level 3 in the fair value hierarchy.
		Three Months Ended				Six Months Ended
		June 30,				June 30,
	(In millions)	2014		2013		2014		2013
	Beginning balance	$	639	$	600	$	625	$	—
	Contingent consideration agreement	—		—		—		600
	Unrealized losses included in net income	8		11		22		11
	Ending balance	$	647	$	611	$	647	$	611
	We did not hold any Level 3 derivative instruments during the three and six months ended June 30, 2014 and 2013. See Note 14 for the income statement impacts of our derivative instruments.
	Fair Values – Nonrecurring
	The following table shows the values of assets, by major category, measured at fair value on a nonrecurring basis in periods subsequent to their initial recognition.
		Six Months Ended June 30,
		2014				2013
	(In millions)	Fair Value		Impairment		Fair Value		Impairment
	Property, plant and equipment, net	$	—	$	—	$	1	$	8
	Other noncurrent assets	—		11		—		—
	Based on the financial and operational status of a company in which we have an interest in, we fully impaired our $11 million investment in that company during the second quarter of 2014. Our investment in this company was accounted for using the cost method and was included in our Refining & Marketing segment. The impairment is included in other income on the consolidated statements of income. The fair value of our investment in this cost company was measured using an income approach. This measurement is classified as Level 3.
	Due to changing market conditions, we assessed one of our light products terminals for impairment. The terminal is operated by our Refining & Marketing segment. We recorded an impairment charge of $8 million for this terminal in 2013. The impairment is included in depreciation and amortization on the consolidated statements of income. The fair value of the terminal was measured using a market approach based on comparable area property values, which are Level 3 inputs.
	Fair Values – Reported
	The following table summarizes financial instruments on the basis of their nature, characteristics and risk at June 30, 2014 and December 31, 2013, excluding the derivative financial instruments and contingent consideration reported above.
		June 30, 2014				December 31, 2013
	(In millions)	Fair Value		Carrying Value		Fair Value		Carrying Value
	Financial assets:
	Investments	$	25	$	2	$	336	$	14
	Other	31		29		31		30
	Total financial assets	$	56	$	31	$	367	$	44
	Financial liabilities:
	Long-term debt(a)	$	3,691	$	3,254	$	3,306	$	3,001
	Deferred credits and other liabilities	20		20		21		21
	Total financial liabilities	$	3,711	$	3,274	$	3,327	$	3,022
	(a)	Excludes capital leases
	Our current assets and liabilities include financial instruments, the most significant of which are trade accounts receivable and payables. We believe the carrying values of our current assets and liabilities approximate fair value. Our fair value assessment incorporates a variety of considerations, including (1) the short-term duration of the instruments, (2) our investment-grade credit rating and (3) our historical incurrence of and expected future insignificance of bad debt expense, which includes an evaluation of counterparty credit risk.
	Fair values of our financial assets included in investments and other financial assets and of our financial liabilities included in deferred credits and other liabilities are measured primarily using an income approach and most inputs are internally generated, which results in a Level 3 classification. Estimated future cash flows are discounted using a rate deemed appropriate to obtain the fair value. Other financial assets primarily consist of environmental remediation receivables. Deferred credits and other liabilities primarily consist of insurance liabilities and environmental remediation liabilities.
	Fair value of fixed-rate long-term debt is measured using a market approach, based upon the average of quotes from major financial institutions and a third-party service for our debt. Because these quotes cannot be independently verified to the market, they are considered Level 3 inputs. Fair value of variable-rate long-term debt approximates the carrying value.

Derivatives

Derivatives	6 Months Ended
	Jun. 30, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Derivatives	'
	Derivatives
	For further information regarding the fair value measurement of derivative instruments, including any effect of master netting agreements or collateral, see Note 13. We do not designate any of our commodity derivative instruments as hedges for accounting purposes.
	Derivatives that are not designated as accounting hedges may include commodity derivatives used to hedge price risk on (1) inventories, (2) fixed price sales of refined products, (3) the acquisition of foreign-sourced crude oil and (4) the acquisition of ethanol for blending with refined products.
	The following table presents the gross fair values of derivative instruments, excluding cash collateral, and where they appear on the consolidated balance sheets as of June 30, 2014 and December 31, 2013:
		June 30, 2014
	(In millions)	Asset				Liability		Balance Sheet Location
	Commodity derivatives	$	44			$	91	Other current assets
		December 31, 2013
	(In millions)	Asset				Liability		Balance Sheet Location
	Commodity derivatives	$	21			$	53	Other current assets
	The table below summarizes open commodity derivative contracts as of June 30, 2014.
		Position		Total Barrels (In thousands)
	Crude oil(a)
	Exchange-traded	Long		14,775
	Exchange-traded	Short		(33,812	)
	Refined Products(a)
	Exchange-traded	Long		4,618
	Exchange-traded	Short		(2,541	)
	(a)	100 percent of these contracts expire in the third quarter of 2014.
	The following table summarizes the effect of all commodity derivative instruments in our consolidated statements of income:
		Gain (Loss)						Gain (Loss)
	(In millions)	Three Months Ended June 30,						Six Months Ended June 30,
	Income Statement Location	2014				2013		2014			2013
	Sales and other operating revenues	$	(2	)		$	3	$	8		$	4
	Cost of revenues	(114		)		51		(175		)	(9		)
	Total	$	(116	)		$	54	$	(167	)	$	(5	)

Debt

Debt	6 Months Ended
	Jun. 30, 2014
Debt Disclosure [Abstract]	'
Debt	'
	Debt
	Our outstanding borrowings at June 30, 2014 and December 31, 2013 consisted of the following:
	(In millions)	June 30,			December 31,
		2014			2013
	Marathon Petroleum Corporation:
	Revolving credit agreement due 2017	$	—		$	—
	3.500% senior notes due March 1, 2016	750			750
	5.125% senior notes due March 1, 2021	1,000			1,000
	6.500% senior notes due March 1, 2041	1,250			1,250
	Consolidated subsidiaries:
	Capital lease obligations due 2014-2028	384			395
	MPLX Operations LLC revolving credit agreement due 2017	255			—
	Trade receivables securitization facility due 2016	—			—
	Total	3,639			3,395
	Unamortized discount	(10		)	(10		)
	Fair value adjustments(a)	9			11
	Amounts due within one year	(26		)	(23		)
	Total long-term debt due after one year	$	3,612		$	3,373
	(a)	The $20 million gain on the termination of our interest rate swap agreements in 2012 is being amortized over the remaining life of the 3.50 percent senior notes.
	There were no borrowings or letters of credit outstanding under the MPC revolving credit agreement or the trade receivables securitization facility at June 30, 2014. During the six months ended June 30, 2014, MPLX borrowed $270 million under the MPLX Operations LLC revolving credit agreement (the "MPLX Credit Agreement"), at an average interest rate of 1.5 percent, per annum, and had repayments of $15 million. The borrowings were used to fund MPLX's acquisition of an additional interest in Pipe Line Holdings. At June 30, 2014, MPLX had $255 million of borrowings and no letters of credit outstanding under the MPLX Credit Agreement, resulting in total unused loan availability of $245 million, or 49 percent of the borrowing capacity. The MPLX Credit Agreement is scheduled to mature on October 31, 2017.

Supplemental_Cash_Flow_Informa

Supplemental Cash Flow Information	6 Months Ended
	Jun. 30, 2014
Supplemental Cash Flow Elements [Abstract]	'
Supplemental Cash Flow Information	'
	Supplemental Cash Flow Information
		Six Months Ended
		June 30,
	(In millions)	2014			2013
	Net cash provided by operating activities included:
	Interest paid (net of amounts capitalized)	$	82		$	86
	Net income taxes paid to taxing authorities	299			719
	Non-cash investing and financing activities:
	Capital lease obligations increase	$	—		$	61
	Property, plant and equipment sold	4			—
	Property, plant and equipment acquired	4			—
	Acquisition:
	Contingent consideration(a)	—			600
	Payable to seller(a)	—			6
	(a)	Acquisition-date fair value of non-cash consideration associated with the Galveston Bay Refinery and Related Assets acquisition.
	The consolidated statements of cash flows exclude changes to the consolidated balance sheets that did not affect cash. The following is a reconciliation of additions to property, plant and equipment to total capital expenditures:
		Six Months Ended
		June 30,
	(In millions)	2014			2013
	Additions to property, plant and equipment per consolidated statements of cash flows	$	569		$	424
	Non-cash additions to property, plant and equipment	4			—
	Acquisitions(a)	27			1,391
	Asset retirement expenditures	1			—
	Increase (decrease) in capital accruals	(31		)	31
	Total capital expenditures	$	570		$	1,846
	(a)	The 2014 acquisition excludes the inventory and other current assets acquired but includes assumed liabilities. The 2013 acquisition includes the acquisition of the Galveston Bay Refinery and Related Assets, comprised of total consideration, excluding inventory and other current assets, plus assumed liabilities. Total consideration for the Galveston Bay Refinery and Related Assets includes the base purchase price and a fair-value estimate of $600 million for the contingent consideration. See Note 4.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Loss	6 Months Ended
	Jun. 30, 2014
Equity [Abstract]	'
Accumulated Other Comprehensive Loss	'
	Accumulated Other Comprehensive Loss
	The following table shows the changes in accumulated other comprehensive loss by component. Amounts in parentheses indicate debits.
	(In millions)	Pension Benefits			Other Benefits			Gain on Cash Flow Hedge		Workers Compensation			Total
	Balance as of December 31, 2012	$	(432	)	$	(36	)	$	4	$	—		$	(464	)
	Other comprehensive income before reclassifications	158			3			—		2			163
	Amounts reclassified from accumulated other comprehensive loss:
	Amortization – prior service credit(a)	(22		)	(2		)	—		—			(24		)
	– actuarial loss(a)	39			1			—		—			40
	– settlement loss(a)	60			—			—		—			60
	Tax effect	(29		)	—			—		—			(29		)
	Other comprehensive income	206			2			—		2			210
	Balance as of June 30, 2013	$	(226	)	$	(34	)	$	4	$	2		$	(254	)
	(In millions)	Pension Benefits			Other Benefits			Gain on Cash Flow Hedge		Workers Compensation			Total
	Balance as of December 31, 2013	$	(161	)	$	(50	)	$	4	$	3		$	(204	)
	Other comprehensive income (loss) before reclassifications	(65		)	8			—		(1		)	(58		)
	Amounts reclassified from accumulated other comprehensive loss:
	Amortization – prior service credit(a)	(23		)	(2		)	—		—			(25		)
	– actuarial loss(a)	26			1			—		—			27
	– settlement loss(a)	69			—			—		—			69
	Tax effect	(28		)	1			—		—			(27		)
	Other comprehensive income (loss)	(21		)	8			—		(1		)	(14		)
	Balance as of June 30, 2014	$	(182	)	$	(42	)	$	4	$	2		$	(218	)
	(a)	These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 18.

Defined_Benefit_Pension_and_Ot

Defined Benefit Pension and Other Postretirement Plans	6 Months Ended
	Jun. 30, 2014
Compensation and Retirement Disclosure [Abstract]	'
Defined Benefit Pension and Other Postretirement Plans	'
	Defined Benefit Pension and Other Postretirement Plans
	The following summarizes the components of net periodic benefit costs:
		Three Months Ended June 30,
		Pension Benefits						Other Benefits
	(In millions)	2014			2013			2014			2013
	Components of net periodic benefit cost:
	Service cost	$	20		$	23		$	6		$	6
	Interest cost	18			18			9			6
	Expected return on plan assets	(26		)	(26		)	—			—
	Amortization – prior service credit	(11		)	(11		)	(1		)	—
	– actuarial loss	13			18			—			—
	– settlement loss	5			60			—			—
	Net periodic benefit cost	$	19		$	82		$	14		$	12
		Six Months Ended June 30,
		Pension Benefits						Other Benefits
	(In millions)	2014			2013			2014			2013
	Components of net periodic benefit cost:
	Service cost	$	43		$	46		$	13		$	12
	Interest cost	38			36			17			13
	Expected return on plan assets	(54		)	(53		)	—			—
	Amortization – prior service credit	(23		)	(22		)	(2		)	(2		)
	– actuarial loss	26			39			1			1
	– settlement loss	69			60			—			—
	Net periodic benefit cost	$	99		$	106		$	29		$	24
	During the six months ended June 30, 2014, we made no contributions to our funded pension plans. We have no required funding for 2014, but may do so at our discretion. Current benefit payments related to unfunded pension and other postretirement benefit plans were $9 million and $10 million, respectively, during the six months ended June 30, 2014.
	During the six months ended June 30, 2014 and 2013, we determined that lump sum payments to employees retiring in the respective years will exceed the plans’ total service and interest costs for the year. Settlement losses are required to be recorded when lump sum payments exceed total service and interest costs. As a result, during the six months ended June 30, 2014 and 2013, we recorded pension settlement expenses of $69 million and $60 million related to our cumulative lump sum payments made during the first six months of 2014 and 2013, respectively.

StockBased_Compensation_Plans

Stock-Based Compensation Plans	6 Months Ended
	Jun. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Stock-Based Compensation Plans	'
	Stock-Based Compensation Plans
	Stock Option Awards
	The following table presents a summary of our stock option award activity for the six months ended June 30, 2014:
		Number of Shares(a)		Weighted Average Exercise Price
	Outstanding at December 31, 2013	5,147,837		$	40.08
	Granted	446,310		85.02
	Exercised	(583,773	)	31.21
	Forfeited, canceled or expired	(20,761	)	49.67
	Outstanding at June 30, 2014	4,989,613		45.09
	(a)	Includes an immaterial number of stock appreciation rights.
	The grant date fair value of stock option awards granted during the six months ended June 30, 2014 was $25.37 per share. The fair value of stock options granted to our employees is estimated on the date of the grant using the Black Scholes option-pricing model, which employs various assumptions. Beginning in the first quarter of 2014, the assumption for expected volatility of our stock price was refined to reflect a weighting of 50 percent of MPC’s common stock implied volatility and 50 percent of MPC's common stock historical volatility.
	Restricted Stock Awards
	The following table presents a summary of restricted stock award activity for the six months ended June 30, 2014:
		Shares of Restricted Stock ("RS")				Restricted Stock Units ("RSU")
		Number of Shares		Weighted Average Grant Date Fair Value		Number of Units		Weighted Average Grant Date Fair Value
	Outstanding at December 31, 2013	624,122		$	61.11	385,079		$	33.96
	Granted	232,594		88.19		12,889		89.16
	RS's Vested/RSU's Issued	(264,470	)	58.48		(398	)	60.11
	Forfeited	(16,446	)	65.72		(133	)	76.1
	Outstanding at June 30, 2014	575,800		73.13		397,437		35.71
	Performance Unit Awards
	The following table presents a summary of the activity for performance unit awards to be settled in shares for the six months ended June 30, 2014:
		Number of Units
	Outstanding at December 31, 2013	3,822,500
	Granted	2,033,700
	Settled	—
	Canceled	—
	Outstanding at June 30, 2014	5,856,200
	The performance unit awards granted in 2014 have a grant date fair value of $1.02 per unit, as calculated using a Monte Carlo valuation model.
	MPLX Awards
	During the six months ended June 30, 2014, MPLX granted equity-based compensation awards under the MPLX LP 2012 Incentive Compensation Plan. The compensation expense for these awards is not material to our consolidated financial statements.

Commitments_and_Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	Commitments and Contingencies
	We are the subject of, or a party to, a number of pending or threatened legal actions, contingencies and commitments involving a variety of matters, including laws and regulations relating to the environment. Some of these matters are discussed below. For matters for which we have not recorded an accrued liability, we are unable to estimate a range of possible loss because the issues involved have not been fully developed through pleadings and discovery. However, the ultimate resolution of some of these contingencies could, individually or in the aggregate, be material.
	Environmental matters—We are subject to federal, state, local and foreign laws and regulations relating to the environment. These laws generally provide for control of pollutants released into the environment and require responsible parties to undertake remediation of hazardous waste disposal sites and certain other locations including presently or formerly owned or operated retail marketing sites. Penalties may be imposed for noncompliance.
	At June 30, 2014 and December 31, 2013, accrued liabilities for remediation totaled $137 million and $123 million, respectively. It is not presently possible to estimate the ultimate amount of all remediation costs that might be incurred or the penalties if any that may be imposed. Receivables for recoverable costs from certain states, under programs to assist companies in clean-up efforts related to underground storage tanks at presently or formerly owned or operated retail marketing sites, was $51 million at both June 30, 2014 and December 31, 2013.
	We are involved in a number of environmental enforcement matters arising in the ordinary course of business. While the outcome and impact on us cannot be predicted with certainty, management believes the resolution of these environmental matters will not, individually or collectively, have a material adverse effect on our consolidated results of operations, financial position or cash flows.
	Lawsuits—In May 2007, the Kentucky attorney general filed a lawsuit against us and Marathon Oil in state court in Franklin County, Kentucky for alleged violations of Kentucky’s emergency pricing and consumer protection laws following Hurricanes Katrina and Rita in 2005. The lawsuit alleges that we overcharged customers by $89 million during September and October 2005. The complaint seeks disgorgement of these sums, as well as penalties, under Kentucky’s emergency pricing and consumer protection laws. We are vigorously defending this litigation. We believe that this is the first lawsuit for damages and injunctive relief under the Kentucky emergency pricing laws to progress this far and it contains many novel issues. In May 2011, the Kentucky attorney general amended his complaint to include a request for immediate injunctive relief as well as unspecified damages and penalties related to our wholesale gasoline pricing in April and May 2011 under statewide price controls that were activated by the Kentucky governor on April 26, 2011 and which have since expired. The court denied the attorney general’s request for immediate injunctive relief, and the remainder of the 2011 claims likely will be resolved along with those dating from 2005. If the lawsuit is resolved unfavorably in its entirety, it could materially impact our consolidated results of operations, financial position or cash flows. However, management does not believe the ultimate resolution of this litigation will have a material adverse effect.
	We are a defendant in a number of other lawsuits and other proceedings arising in the ordinary course of business. While the ultimate outcome and impact to us cannot be predicted with certainty, we believe that the resolution of these other lawsuits and proceedings will not have a material adverse effect on our consolidated financial position, results of operations or cash flows.
	Guarantees—We have provided certain guarantees, direct and indirect, of the indebtedness of other companies. Under the terms of most of these guarantee arrangements, we would be required to perform should the guaranteed party fail to fulfill its obligations under the specified arrangements. In addition to these financial guarantees, we also have various performance guarantees related to specific agreements.
	Guarantees related to indebtedness of equity method investees—We hold interests in an offshore oil port, LOOP, and a crude oil pipeline system, LOCAP. Both LOOP and LOCAP have secured various project financings with throughput and deficiency agreements. Under the agreements, we are required to advance funds if the investees are unable to service their debt. Any such advances are considered prepayments of future transportation charges. The duration of the agreements vary but tend to follow the terms of the underlying debt, which extend through 2037. Our maximum potential undiscounted payments under these agreements for the debt principal totaled $172 million as of June 30, 2014.
	We hold an interest in a refined products pipeline through our investment in Centennial, and have guaranteed the payment of Centennial’s principal, interest and prepayment costs, if applicable, under a Master Shelf Agreement, which is scheduled to expire in 2024. The guarantee arose in order for Centennial to obtain adequate financing. Our maximum potential undiscounted payments under this agreement for debt principal totaled $40 million as of June 30, 2014.
	We hold an interest in an ethanol production facility through our investment in TAME, and through our participation as a lender under TAME’s revolving credit agreement, have agreed to reimburse the bank for 50 percent of any amounts drawn on a letter of credit that has been issued to secure TAME’s repayment of the tax exempt bonds. The credit agreement expires in 2018. Our maximum potential undiscounted payments under this arrangement were $25 million at June 30, 2014.
	Marathon Oil indemnifications—In conjunction with our spinoff from Marathon Oil, we have entered into arrangements with Marathon Oil providing indemnities and guarantees with recorded values of $2 million as of June 30, 2014, which consist of unrecognized tax benefits related to MPC, its consolidated subsidiaries and the refining, marketing and transportation business operations prior to our spinoff which are not already reflected in the unrecognized tax benefits described in Note 10, and other contingent liabilities Marathon Oil may incur related to taxes. Furthermore, the separation and distribution agreement and other agreements with Marathon Oil to effect our spinoff provide for cross-indemnities between Marathon Oil and us. In general, Marathon Oil is required to indemnify us for any liabilities relating to Marathon Oil’s historical oil and gas exploration and production operations, oil sands mining operations and integrated gas operations, and we are required to indemnify Marathon Oil for any liabilities relating to Marathon Oil’s historical refining, marketing and transportation operations. The terms of these indemnifications are indefinite and the amounts are not capped.
	Other guarantees—We have entered into other guarantees with maximum potential undiscounted payments totaling $122 million as of June 30, 2014, which primarily consist of a commitment to contribute cash to an equity method investee for certain catastrophic events, up to $50 million per event, in lieu of procuring insurance coverage, an indemnity to the co-lenders associated with an equity method investee’s credit agreement, and leases of assets containing general lease indemnities and guaranteed residual values.
	General guarantees associated with dispositions – Over the years, we have sold various assets in the normal course of our business. Certain of the related agreements contain performance and general guarantees, including guarantees regarding inaccuracies in representations, warranties, covenants and agreements, and environmental and general indemnifications that require us to perform upon the occurrence of a triggering event or condition. These guarantees and indemnifications are part of the normal course of selling assets. We are typically not able to calculate the maximum potential amount of future payments that could be made under such contractual provisions because of the variability inherent in the guarantees and indemnities. Most often, the nature of the guarantees and indemnities is such that there is no appropriate method for quantifying the exposure because the underlying triggering event has little or no past experience upon which a reasonable prediction of the outcome can be based.
	Contractual commitments—At June 30, 2014, our contractual commitments to acquire property, plant and equipment and advance funds to equity method investees totaled $4.2 billion, which includes $2.37 billion for the pending acquisition of Hess Retail, $700 million of contingent consideration associated with the acquisition of the Galveston Bay Refinery and Related Assets and $825 million for contributions to North Dakota Pipeline. See Note 4 for additional information on the pending acquisition of Hess Retail and our investment in North Dakota Pipeline. See Notes 4 and 13 for additional information on the contingent consideration.

Subsequent_Event_Subsequent_Ev

Subsequent Event Subsequent Event	6 Months Ended
	Jun. 30, 2014
Subsequent Events [Abstract]	'
Subsequent Events	'
	Subsequent Event
	Southern Access Extension Pipeline project
	In July 2014, we exercised our option to acquire a 35 percent ownership interest in Enbridge Inc.'s Southern Access Extension pipeline ("SAX") through our investment in Illinois Extension Pipeline Company, LLC ("Illinois Extension Pipeline"). During July, we made an initial contribution of $69 million to Illinois Extension Pipeline to fund our portion of the construction costs incurred-to-date on the SAX project. In return for our investment in the SAX project, we received a 35 percent equity interest in Illinois Extension Pipeline. We expect to make future contributions of approximately $226 million related to the ongoing construction of the pipeline, which is expected to be operational in mid 2015.

Supplementary_Statistics

Supplementary Statistics	6 Months Ended
	Jun. 30, 2014
Text Block [Abstract]	'
Supplementary Statistics	'
	Supplementary Statistics (Unaudited)
		Three Months Ended						Six Months Ended
		June 30,						June 30,
	(In millions)	2014			2013			2014			2013
	Income from Operations by segment
	Refining & Marketing	$	1,260		$	903		$	1,622		$	2,008
	Speedway	94			123			152			190
	Pipeline Transportation(a)	81			58			153			109
	Items not allocated to segments:
	Corporate and other unallocated items(a)	(61		)	(64		)	(128		)	(131		)
	Pension settlement expenses	(5		)	(60		)	(69		)	(60		)
	Income from operations	$	1,369		$	960		$	1,730		$	2,116
	Capital Expenditures and Investments(b)(c)
	Refining & Marketing	$	235		$	134		$	413		$	1,554
	Speedway	44			76			76			112
	Pipeline Transportation	64			41			194			131
	Corporate and Other(d)	20			32			51			60
	Total	$	363		$	283		$	734		$	1,857
	(a)	Corporate overhead expenses attributable to MPLX are included in the Pipeline Transportation segment. These expenses are not allocated to the Refining & Marketing and Speedway segments.
	(b)	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
	(c)	The six months ended June 30, 2013 includes the acquisition of the Galveston Bay Refinery and Related Assets, comprised of total consideration, excluding inventory and other current assets, plus assumed liabilities. Total consideration includes the base purchase price and a fair-value estimate of $600 million for the contingent consideration. See Note 4 to the unaudited consolidated financial statements.
	(d)	Includes capitalized interest $7 million and $4 million for the three months ended June 30, 2014 and 2013, respectively, and $13 million and $8 million for the six months ended June 30, 2014 and 2013, respectively.
	Supplementary Statistics (Unaudited)
		Three Months Ended						Six Months Ended
		June 30,						June 30,
		2014			2013			2014			2013
	MPC Consolidated Refined Product Sales Volumes (thousands of barrels per day)(a)(b)	2,153			2,135			2,059			2,016
	Refining & Marketing Operating Statistics(b)
	Refining & Marketing refined product sales volume (thousands of barrels per day)(c)	2,145			2,125			2,048			2,004
	Refining & Marketing gross margin (dollars per barrel)(d)	$	16.02		$	13.11		$	15.28		$	14.14
	Crude oil capacity utilization percent(e)	98			99			91			96
	Refinery throughputs (thousands of barrels per day):(f)
	Crude oil refined	1,674			1,690			1,563			1,562
	Other charge and blendstocks	158			174			178			206
	Total	1,832			1,864			1,741			1,768
	Sour crude oil throughput percent	54			52			52			53
	WTI-priced crude oil throughput percent	17			22			19			22
	Refined product yields (thousands of barrels per day):(f)
	Gasoline	852			923			844			906
	Distillates	610			609			562			566
	Propane	37			40			36			36
	Feedstocks and special products	288			240			255			212
	Heavy fuel oil	27			31			28			31
	Asphalt	51			54			47			50
	Total	1,865			1,897			1,772			1,801
	Refinery direct operating costs (dollars per barrel):(g)
	Planned turnaround and major maintenance	$	0.94		$	0.73		$	1.98		$	0.93
	Depreciation and amortization	1.39			1.28			1.47			1.35
	Other manufacturing(h)	4.77			4.06			5.32			3.94
	Total	$	7.1		$	6.07		$	8.77		$	6.22
	Refining & Marketing Operating Statistics By Region - Gulf Coast(b)
	Refinery throughputs (thousands of barrels per day):(i)
	Crude oil refined	1,031			1,037			946			938
	Other charge and blendstocks	156			157			183			184
	Total	1,187			1,194			1,129			1,122
	Sour crude oil throughput percent	67			64			64			66
	WTI-priced crude oil throughput percent	2			11			3			9
	Refined product yields (thousands of barrels per day):(i)
	Gasoline	500			542			494			536
	Distillates	390			398			355			360
	Propane	25			25			23			22
	Feedstocks and special products	270			223			258			201
	Heavy fuel oil	16			20			15			19
Asphalt	13			13			10			10
Total	1,214			1,221			1,155			1,148
Refinery direct operating costs (dollars per barrel):(g)
Planned turnaround and major maintenance	$	0.57		$	0.6		$	2.11		$	0.72
Depreciation and amortization	1.13			1			1.19			1.06
Other manufacturing(h)	4.77			4.01			5.28			3.68
Total	$	6.47		$	5.61		$	8.58		$	5.46
Supplementary Statistics (Unaudited)
	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2014			2013			2014			2013
Refining & Marketing Operating Statistics By Region - Midwest
Refinery throughputs (thousands of barrels per day):(i)
Crude oil refined	643			653			617			624
Other charge and blendstocks	45			54			46			55
Total	688			707			663			679
Sour crude oil throughput percent	34			34			34			35
WTI-priced crude oil throughput percent	40			40			43			42
Refined product yields (thousands of barrels per day):(i)
Gasoline	352			383			350			371
Distillates	220			211			207			206
Propane	13			15			14			14
Feedstocks and special products	60			52			47			43
Heavy fuel oil	11			11			13			12
Asphalt	38			41			37			40
Total	694			713			668			686
Refinery direct operating costs (dollars per barrel):(g)
Planned turnaround and major maintenance	$	1.53		$	0.9		$	1.62		$	1.22
Depreciation and amortization	1.75			1.68			1.83			1.75
Other manufacturing(h)	4.47			3.96			4.97			4.2
Total	$	7.75		$	6.54		$	8.42		$	7.17
Speedway Operating Statistics
Convenience stores at period-end	1,492			1,468
Gasoline and distillate sales (millions of gallons)	806			781			1,579			1,526
Gasoline and distillate gross margin (dollars per gallon)(j)	$	0.1282		$	0.1738		$	0.122		$	0.1525
Merchandise sales (in millions)	$	830		$	806		$	1,552		$	1,517
Merchandise gross margin (in millions)	$	224		$	212		$	416		$	396
Merchandise gross margin percent	27.1		%	26.3		%	26.8		%	26.1		%
Same store gasoline sales volume (period over period)	(1.5		%)	—		%	(1.1		%)	0.3		%
Same store merchandise sales (period over period)(k)	4.6		%	4.5		%	4.9		%	2.8		%
Pipeline Transportation Operating Statistics
Pipeline throughputs (thousands of barrels per day):(l)
Crude oil pipelines	1,281			1,334			1,213			1,303
Refined products pipelines	871			959			845			939
Total	2,152			2,293			2,058			2,242
(a)	Total average daily volumes of refined product sales to wholesale, branded and retail (Speedway segment) customers.
(b)	Includes the impact of the Galveston Bay Refinery and Related Assets beginning on the February 1, 2013 acquisition date.
(c)	Includes intersegment sales.
(d)	Sales revenue less cost of refinery inputs and purchased products, divided by total refinery throughputs.
(e)	Based on calendar day capacity, which is an annual average that includes downtime for planned maintenance and other normal operating activities.
(f)	Excludes inter-refinery volumes of 43 mbpd and 37 mbpd for the three months ended June 30, 2014 and 2013, respectively, and 51 mbpd and 33 mbpd for the six months ended June 30, 2014 and 2013, respectively.
(g)	Per barrel of total refinery throughputs.
(h)	Includes utilities, labor, routine maintenance and other operating costs.
(i)	Includes inter-refinery transfer volumes.
(j)	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.
(k)	Excludes cigarettes.
(l)	On owned common-carrier pipelines, excluding equity method investments.

Description_of_the_Business_an1

Description of the Business and Basis of Presentation (Policies)	6 Months Ended
	Jun. 30, 2014
Accounting Policies [Abstract]	'
Use of estimates	'
	These interim consolidated financial statements are unaudited; however, in the opinion of our management, these statements reflect all adjustments necessary for a fair statement of the results for the periods reported. All such adjustments are of a normal, recurring nature unless otherwise disclosed. These interim consolidated financial statements, including the notes, have been prepared in accordance with the rules of the Securities and Exchange Commission applicable to interim period financial statements and do not include all of the information and disclosures required by United States generally accepted accounting principles (“U.S. GAAP”) for complete financial statements.
Inventories	'
	Inventories are carried at the lower of cost or market value. The cost of inventories of crude oil and refinery feedstocks, refined products and merchandise is determined primarily under the last-in, first-out (“LIFO”) method.
Derivative instruments	'
	Derivatives that are not designated as accounting hedges may include commodity derivatives used to hedge price risk on (1) inventories, (2) fixed price sales of refined products, (3) the acquisition of foreign-sourced crude oil and (4) the acquisition of ethanol for blending with refined products.
Stock-based compensation arrangements	'
	The fair value of stock options granted to our employees is estimated on the date of the grant using the Black Scholes option-pricing model, which employs various assumptions. Beginning in the first quarter of 2014, the assumption for expected volatility of our stock price was refined to reflect a weighting of 50 percent of MPC’s common stock implied volatility and 50 percent of MPC's common stock historical volatility.

Acquisitions_and_Investments_A

Acquisitions and Investments Acquisitions and Investments (Tables)	6 Months Ended
	Jun. 30, 2014
Business Combinations [Abstract]	'
Business Acquisition, Pro Forma Information [Table Text Block]	'
	The following unaudited pro forma financial information presents consolidated results assuming the Galveston Bay Refinery and Related Assets acquisition occurred on January 1, 2012. The pro forma financial information does not give effect to potential synergies that could result from the acquisition and is not necessarily indicative of the results of future operations.
	(In millions, except per share data)	Six Months Ended June 30, 2013
	Sales and other operating revenues (including consumer excise taxes)	$	50,975
	Net income attributable to MPC	1,373
	Net income attributable to MPC per share - basic	$	4.21
	Net income attributable to MPC per share - diluted	4.19

Related_Party_Transactions_Tab

Related Party Transactions (Tables)	6 Months Ended
	Jun. 30, 2014
Related Party Transactions [Abstract]	'
Sales To Related Parties	'
	Sales to related parties, which are included in sales and other operating revenues (including consumer excise taxes) on the consolidated statements of income, were as follows:
		Three Months Ended					Six Months Ended
		June 30,					June 30,
	(In millions)	2014			2013		2014		2013
	Other equity method investees	$	2		$	2	$	4	$	4
Purchases From Related Parties	'
	Purchases from related parties were as follows:
		Three Months Ended					Six Months Ended
		June 30,					June 30,
	(In millions)	2014			2013		2014		2013
	Centennial	$	(2	)	$	—	$	7	$	—
	Explorer	9			—		22		—
	LOCAP	5			4		10		8
	LOOP	12			11		65		21
	TAAE	26			—		42		—
	TACE	30			24		57		50
	TAME	48			37		82		67
	Other equity method investees	2			3		4		5
	Total	$	130		$	79	$	289	$	151
Receivables From Related Parties	'
	Receivables from related parties, which are included in receivables, less allowance for doubtful accounts on the consolidated balance sheets, were as follows:
	(In millions)	June 30,			December 31,
		2014			2013
	Centennial	$	1		$	1
	TAME	2			1
	Total	$	3		$	2
Payables To Related Parties	'
	Payables to related parties, which are included in accounts payable on the consolidated balance sheets, were as follows:
	(In millions)	June 30,			December 31,
		2014			2013
	Explorer	$	3		$	—
	LOCAP	1			2
	LOOP	4			3
	TAAE	3			2
	TACE	2			4
	TAME	4			5
	Other equity method investees	1			—
	Total	$	18		$	16

Income_per_Common_Share_Tables

Income per Common Share (Tables)	6 Months Ended
	Jun. 30, 2014
Earnings Per Share [Abstract]	'
Summary of Earnings Per Common Share	'
		Three Months Ended						Six Months Ended
		June 30,						June 30,
	(In millions, except per share data)	2014			2013			2014		2013
	Basic earnings per share:
	Allocation of earnings:
	Net income attributable to MPC	$	855		$	593		$	1,054	$	1,318
	Income allocated to participating securities	1			1			2		2
	Income available to common stockholders - basic	$	854		$	592		$	1,052	$	1,316
	Weighted average common shares outstanding	287			322			290		326
	Basic earnings per share	$	2.97		$	1.84		$	3.63	$	4.03
	Diluted earnings per share:
	Allocation of earnings:
	Net income attributable to MPC	$	855		$	593		$	1,054	$	1,318
	Income allocated to participating securities	1			1			2		2
	Income available to common stockholders - diluted	$	854		$	592		$	1,052	$	1,316
	Weighted average common shares outstanding	287			322			290		326
	Effect of dilutive securities	2			2			2		2
	Weighted average common shares, including dilutive effect	289			324			292		328
	Diluted earnings per share	$	2.95		$	1.83		$	3.6	$	4.01
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	'
		Three Months Ended					Six Months Ended
		June 30,					June 30,
	(In millions)	2014		2013			2014		2013
	Shares issued under stock-based compensation plans	—		1			—		1

Equity_Tables

Equity (Tables)	6 Months Ended
	Jun. 30, 2014
Equity [Abstract]	'
Share Repurchases Transacted Through ASR Programs and Open Market Transactions	'
	Total share repurchases were as follows for the three and six months ended June 30, 2014 and 2013:
		Three Months Ended				Six Months Ended
		June 30,				June 30,
	(In millions, except per share data)	2014		2013		2014		2013
	Number of shares repurchased(a)	5		11		13		17
	Cash paid for shares repurchased	$	459	$	882	$	1,148	$	1,313
	Effective average cost per delivered share	$	88.14	$	80.31	$	87.82	$	80.54
	(a)	The six months ended June 30, 2013 includes one million shares received under the November 2012 accelerated share repurchase program, which were paid for in 2012.

Segment_Information_Tables

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2014
Segment Reporting [Abstract]	'
Income From Operations Attributable To Operating Segments	'
	(In millions)	Refining & Marketing			Speedway			Pipeline Transportation			Total
	Three Months Ended June 30, 2014
	Revenues:
	Customer	$	22,917		$	3,908		$	19		$	26,844
	Intersegment(a)	2,590			1			131			2,722
	Segment revenues	$	25,507		$	3,909		$	150		$	29,566
	Segment income from operations(b)	$	1,260		$	94		$	81		$	1,435
	Income from equity method investments	35			—			22			57
	Depreciation and amortization(c)	264			29			19			312
	Capital expenditures and investments(d)	235			44			64			343
	(In millions)	Refining & Marketing			Speedway			Pipeline Transportation			Total
	Three Months Ended June 30, 2013
	Revenues:
	Customer	$	21,890		$	3,768		$	19		$	25,677
	Intersegment(a)	2,434			1			119			2,554
	Segment revenues	$	24,324		$	3,769		$	138		$	28,231
	Segment income from operations(b)	$	903		$	123		$	58		$	1,084
	Income from equity method investments	3			—			4			7
	Depreciation and amortization(c)	252			27			18			297
	Capital expenditures and investments(d)	134			76			41			251
	(In millions)	Refining & Marketing			Speedway			Pipeline Transportation			Total
	Six Months Ended June 30, 2014
	Revenues:
	Customer	$	42,727		$	7,366		$	36		$	50,129
	Intersegment(a)	4,823			2			260			5,085
	Segment revenues	$	47,550		$	7,368		$	296		$	55,214
	Segment income from operations(b)	$	1,622		$	152		$	153		$	1,927
	Income from equity method investments	59			—			33			92
	Depreciation and amortization(c)	525			57			38			620
	Capital expenditures and investments(d)	413			76			194			683
	(In millions)	Refining & Marketing			Speedway			Pipeline Transportation			Total
	Six Months Ended June 30, 2013
	Revenues:
	Customer	$	41,764		$	7,209		$	40		$	49,013
	Intersegment(a)	4,633			2			223			4,858
	Segment revenues	$	46,397		$	7,211		$	263		$	53,871
	Segment income from operations(b)	$	2,008		$	190		$	109		$	2,307
	Income (loss) from equity method investments	(1		)	—			8			7
	Depreciation and amortization(c)	488			54			36			578
	Capital expenditures and investments(d)(e)	1,554			112			131			1,797
	(a)	Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties.
	(b)	Corporate overhead expenses attributable to MPLX are included in the Pipeline Transportation segment. These expenses are not allocated to the Refining & Marketing and Speedway segments.
	(c)	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.
	(d)	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
	(e)	The Refining & Marketing and Pipeline Transportation segments include the acquisition of the Galveston Bay Refinery and Related Assets. See Note 4.
Reconciliation Of Segment Income From Operations To Income Before Income Taxes	'
	The following reconciles segment income from operations to income before income taxes as reported in the consolidated statements of income:
		Three Months Ended						Six Months Ended
		June 30,						June 30,
	(In millions)	2014			2013			2014			2013
	Segment income from operations	$	1,435		$	1,084		$	1,927		$	2,307
	Items not allocated to segments:
	Corporate and other unallocated items(a)(b)	(61		)	(64		)	(128		)	(131		)
	Pension settlement expenses(c)	(5		)	(60		)	(69		)	(60		)
	Net interest and other financial income (costs)	(48		)	(45		)	(94		)	(93		)
	Income before income taxes	$	1,321		$	915		$	1,636		$	2,023
	(a)	Corporate and other unallocated items consists primarily of MPC’s corporate administrative expenses and costs related to certain non-operating assets.
	(b)	Corporate overhead expenses attributable to MPLX are included in the Pipeline Transportation segment. These expenses are not allocated to the Refining & Marketing and Speedway segments.
	(c)	See Note 18.
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures	'
	The following reconciles segment capital expenditures and investments to total capital expenditures:
		Three Months Ended						Six Months Ended
		June 30,						June 30,
	(In millions)	2014			2013			2014			2013
	Segment capital expenditures and investments	$	343		$	251		$	683		$	1,797
	Less: Investments in equity method investees	41			6			164			11
	Plus: Items not allocated to segments:
	Capital expenditures not allocated to segments	13			28			38			52
	Capitalized interest	7			4			13			8
	Total capital expenditures(a)(b)	$	322		$	277		$	570		$	1,846
	(a)	Capital expenditures include changes in capital accruals and acquisitions.
	(b)	See Note 16 for a reconciliation of total capital expenditures to additions to property, plant and equipment as reported in the consolidated statements of cash flows.
Reconciliation Of Total Revenues To Sales And Other Operating Revenues	'
	The following reconciles customer revenues to sales and other operating revenues (including consumer excise taxes) as reported in the consolidated statements of income:
		Three Months Ended						Six Months Ended
		June 30,						June 30,
	(In millions)	2014			2013			2014			2013
	Customer revenues (as reported above)	$	26,844		$	25,677		$	50,129		$	49,013
	Corporate and other unallocated items	—			—			—			(6		)
	Sales and other operating revenues (including consumer excise taxes)	$	26,844		$	25,677		$	50,129		$	49,007
Total Assets By Reportable Segment	'
	Total assets by reportable segment were:
	(In millions)	June 30,			December 31, 2013
		2014
	Refining & Marketing	$	20,708		$	19,573
	Speedway	2,185			2,064
	Pipeline Transportation	2,135			1,947
	Corporate and Other	4,348			4,801
	Total consolidated assets	$	29,376		$	28,385

Other_Items_Tables

Other Items (Tables)	6 Months Ended
	Jun. 30, 2014
Other Income and Expenses [Abstract]	'
Net Interest And Other Financial Income (Costs)	'
	Net interest and other financial income (costs) was:
		Three Months Ended						Six Months Ended
		June 30,						June 30,
	(In millions)	2014			2013			2014			2013
	Interest:
	Interest income	$	1		$	3		$	3		$	5
	Interest expense	(49		)	(49		)	(98		)	(97		)
	Interest capitalized	7			4			13			8
	Total net interest	(41		)	(42		)	(82		)	(84		)
	Other:
	Net foreign currency gains (losses)	(1		)	2			(1		)	1
	Bank service and other fees	(6		)	(5		)	(11		)	(10		)
	Total other	(7		)	(3		)	(12		)	(9		)
	Net interest and other financial income (costs)	$	(48	)	$	(45	)	$	(94	)	$	(93	)

Inventories_Tables

Inventories (Tables)	6 Months Ended
	Jun. 30, 2014
Inventory Disclosure [Abstract]	'
Summary Of Inventories	'
	(In millions)	June 30,		December 31,
		2014		2013
	Crude oil and refinery feedstocks	$	2,835	$	1,797
	Refined products	2,367		2,367
	Materials and supplies	333		425
	Merchandise	86		100
	Total (at cost)	$	5,621	$	4,689

Property_Plant_and_Equipment_T

Property, Plant and Equipment (Tables)	6 Months Ended
	Jun. 30, 2014
Property, Plant and Equipment [Abstract]	'
Summary Of Property, Plant And Equipment	'
	(In millions)	June 30,		December 31,
		2014		2013
	Refining & Marketing	$	17,329	$	16,982
	Speedway	2,412		2,344
	Pipeline Transportation	1,948		1,921
	Corporate and Other	588		546
	Total	22,277		21,793
	Less accumulated depreciation	8,427		7,872
	Property, plant and equipment, net	$	13,850	$	13,921

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2014
Fair Value Disclosures [Abstract]	'
Assets and Liabilities Accounted for at Fair Value on Recurring Basis	'
	The following tables present assets and liabilities accounted for at fair value on a recurring basis as of June 30, 2014 and December 31, 2013 by fair value hierarchy level. We have elected to offset the fair value amounts recognized for multiple derivative contracts executed with the same counterparty, including any related cash collateral as shown below; however, fair value amounts by hierarchy level are presented on a gross basis in the following tables.
		June 30, 2014
		Fair Value Hierarchy
	(In millions)	Level 1		Level 2		Level 3		Netting and Collateral(a)			Net Carrying Value on Balance Sheet(b)		Collateral Pledged Not Offset
	Commodity derivative instruments, assets	$	44	$	—	$	—	$	(44	)	$	—	$	60
	Other assets	2		—		—		N/A			2		—
	Total assets at fair value	$	46	$	—	$	—	$	(44	)	$	2	$	60
	Commodity derivative instruments, liabilities	$	91	$	—	$	—	$	(91	)	$	—	$	—
	Contingent consideration, liability(c)	—		—		647		N/A			647		—
	Total liabilities at fair value	$	91	$	—	$	647	$	(91	)	$	647	$	—
		December 31, 2013
		Fair Value Hierarchy
	(In millions)	Level 1		Level 2		Level 3		Netting and Collateral(a)			Net Carrying Value on Balance Sheet(b)		Collateral Pledged Not Offset
	Commodity derivative instruments, assets	$	21	$	—	$	—	$	(21	)	$	—	$	61
	Other assets	2		—		—		N/A			2		—
	Total assets at fair value	$	23	$	—	$	—	$	(21	)	$	2	$	61
	Commodity derivative instruments, liabilities	$	53	$	—	$	—	$	(53	)	$	—	$	—
	Contingent consideration, liability(c)	—		—		625		N/A			625		—
	Total liabilities at fair value	$	53	$	—	$	625	$	(53	)	$	625	$	—
	(a)	Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of June 30, 2014 and December 31, 2013, cash collateral of $47 million and $32 million, respectively, was netted with mark-to-market derivative liabilities.
	(b)	We have no derivative contracts that are subject to master netting arrangements that are reflected gross on the balance sheet.
	(c)	Includes $370 million and $159 million classified as current at June 30, 2014 and December 31, 2013, respectively.
Reconciliation of Net Beginning and Ending Balances Recorded for Net Assets and Liabilities Classified as Level 3	'
	The following is a reconciliation of the beginning and ending balances recorded for liabilities classified as Level 3 in the fair value hierarchy.
		Three Months Ended				Six Months Ended
		June 30,				June 30,
	(In millions)	2014		2013		2014		2013
	Beginning balance	$	639	$	600	$	625	$	—
	Contingent consideration agreement	—		—		—		600
	Unrealized losses included in net income	8		11		22		11
	Ending balance	$	647	$	611	$	647	$	611
Fair Value Measurements, Nonrecurring	'
		Six Months Ended June 30,
		2014				2013
	(In millions)	Fair Value		Impairment		Fair Value		Impairment
	Property, plant and equipment, net	$	—	$	—	$	1	$	8
	Other noncurrent assets	—		11		—		—
Financial Instruments at Fair Value, Excluding Derivative Financial Instruments and Contingent Consideration	'
	The following table summarizes financial instruments on the basis of their nature, characteristics and risk at June 30, 2014 and December 31, 2013, excluding the derivative financial instruments and contingent consideration reported above.
		June 30, 2014				December 31, 2013
	(In millions)	Fair Value		Carrying Value		Fair Value		Carrying Value
	Financial assets:
	Investments	$	25	$	2	$	336	$	14
	Other	31		29		31		30
	Total financial assets	$	56	$	31	$	367	$	44
	Financial liabilities:
	Long-term debt(a)	$	3,691	$	3,254	$	3,306	$	3,001
	Deferred credits and other liabilities	20		20		21		21
	Total financial liabilities	$	3,711	$	3,274	$	3,327	$	3,022
	(a)	Excludes capital leases

Derivatives_Tables

Derivatives (Tables)	6 Months Ended
	Jun. 30, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Classification of Fair Values of Derivative Instruments, Excluding Cash Collateral	'
	The following table presents the gross fair values of derivative instruments, excluding cash collateral, and where they appear on the consolidated balance sheets as of June 30, 2014 and December 31, 2013:
		June 30, 2014
	(In millions)	Asset				Liability		Balance Sheet Location
	Commodity derivatives	$	44			$	91	Other current assets
		December 31, 2013
	(In millions)	Asset				Liability		Balance Sheet Location
	Commodity derivatives	$	21			$	53	Other current assets
Open Commodity Derivative Contracts	'
	The table below summarizes open commodity derivative contracts as of June 30, 2014.
		Position		Total Barrels (In thousands)
	Crude oil(a)
	Exchange-traded	Long		14,775
	Exchange-traded	Short		(33,812	)
	Refined Products(a)
	Exchange-traded	Long		4,618
	Exchange-traded	Short		(2,541	)
	(a)	100 percent of these contracts expire in the third quarter of 2014.
Effect of Commodity Derivative Instruments in Statements of Income	'
	The following table summarizes the effect of all commodity derivative instruments in our consolidated statements of income:
		Gain (Loss)						Gain (Loss)
	(In millions)	Three Months Ended June 30,						Six Months Ended June 30,
	Income Statement Location	2014				2013		2014			2013
	Sales and other operating revenues	$	(2	)		$	3	$	8		$	4
	Cost of revenues	(114		)		51		(175		)	(9		)
	Total	$	(116	)		$	54	$	(167	)	$	(5	)

Debt_Tables

Debt (Tables)	6 Months Ended
	Jun. 30, 2014
Debt Disclosure [Abstract]	'
Outstanding Borrowings	'
	Our outstanding borrowings at June 30, 2014 and December 31, 2013 consisted of the following:
	(In millions)	June 30,			December 31,
		2014			2013
	Marathon Petroleum Corporation:
	Revolving credit agreement due 2017	$	—		$	—
	3.500% senior notes due March 1, 2016	750			750
	5.125% senior notes due March 1, 2021	1,000			1,000
	6.500% senior notes due March 1, 2041	1,250			1,250
	Consolidated subsidiaries:
	Capital lease obligations due 2014-2028	384			395
	MPLX Operations LLC revolving credit agreement due 2017	255			—
	Trade receivables securitization facility due 2016	—			—
	Total	3,639			3,395
	Unamortized discount	(10		)	(10		)
	Fair value adjustments(a)	9			11
	Amounts due within one year	(26		)	(23		)
	Total long-term debt due after one year	$	3,612		$	3,373
	(a)	The $20 million gain on the termination of our interest rate swap agreements in 2012 is being amortized over the remaining life of the 3.50 percent senior notes.

Supplemental_Cash_Flow_Informa1

Supplemental Cash Flow Information (Tables)	6 Months Ended
	Jun. 30, 2014
Supplemental Cash Flow Elements [Abstract]	'
Summary of Supplemental Cash Flow Information	'
		Six Months Ended
		June 30,
	(In millions)	2014			2013
	Net cash provided by operating activities included:
	Interest paid (net of amounts capitalized)	$	82		$	86
	Net income taxes paid to taxing authorities	299			719
	Non-cash investing and financing activities:
	Capital lease obligations increase	$	—		$	61
	Property, plant and equipment sold	4			—
	Property, plant and equipment acquired	4			—
	Acquisition:
	Contingent consideration(a)	—			600
	Payable to seller(a)	—			6
	(a)	Acquisition-date fair value of non-cash consideration associated with the Galveston Bay Refinery and Related Assets acquisition.
Reconciliation of Additions to Property, Plant and Equipment to Total Capital Expenditures	'
	The consolidated statements of cash flows exclude changes to the consolidated balance sheets that did not affect cash. The following is a reconciliation of additions to property, plant and equipment to total capital expenditures:
		Six Months Ended
		June 30,
	(In millions)	2014			2013
	Additions to property, plant and equipment per consolidated statements of cash flows	$	569		$	424
	Non-cash additions to property, plant and equipment	4			—
	Acquisitions(a)	27			1,391
	Asset retirement expenditures	1			—
	Increase (decrease) in capital accruals	(31		)	31
	Total capital expenditures	$	570		$	1,846
	(a)	The 2014 acquisition excludes the inventory and other current assets acquired but includes assumed liabilities. The 2013 acquisition includes the acquisition of the Galveston Bay Refinery and Related Assets, comprised of total consideration, excluding inventory and other current assets, plus assumed liabilities. Total consideration for the Galveston Bay Refinery and Related Assets includes the base purchase price and a fair-value estimate of $600 million for the contingent consideration. See Note 4.

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Loss (Tables)	6 Months Ended
	Jun. 30, 2014
Equity [Abstract]	'
Changes in Accumulated Other Comprehensive Loss by Component	'
	The following table shows the changes in accumulated other comprehensive loss by component. Amounts in parentheses indicate debits.
	(In millions)	Pension Benefits			Other Benefits			Gain on Cash Flow Hedge		Workers Compensation			Total
	Balance as of December 31, 2012	$	(432	)	$	(36	)	$	4	$	—		$	(464	)
	Other comprehensive income before reclassifications	158			3			—		2			163
	Amounts reclassified from accumulated other comprehensive loss:
	Amortization – prior service credit(a)	(22		)	(2		)	—		—			(24		)
	– actuarial loss(a)	39			1			—		—			40
	– settlement loss(a)	60			—			—		—			60
	Tax effect	(29		)	—			—		—			(29		)
	Other comprehensive income	206			2			—		2			210
	Balance as of June 30, 2013	$	(226	)	$	(34	)	$	4	$	2		$	(254	)
	(In millions)	Pension Benefits			Other Benefits			Gain on Cash Flow Hedge		Workers Compensation			Total
	Balance as of December 31, 2013	$	(161	)	$	(50	)	$	4	$	3		$	(204	)
	Other comprehensive income (loss) before reclassifications	(65		)	8			—		(1		)	(58		)
	Amounts reclassified from accumulated other comprehensive loss:
	Amortization – prior service credit(a)	(23		)	(2		)	—		—			(25		)
	– actuarial loss(a)	26			1			—		—			27
	– settlement loss(a)	69			—			—		—			69
	Tax effect	(28		)	1			—		—			(27		)
	Other comprehensive income (loss)	(21		)	8			—		(1		)	(14		)
	Balance as of June 30, 2014	$	(182	)	$	(42	)	$	4	$	2		$	(218	)
	(a)	These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 18.

Defined_Benefit_Pension_and_Ot1

Defined Benefit Pension and Other Postretirement Plans (Tables)	6 Months Ended
	Jun. 30, 2014
Compensation and Retirement Disclosure [Abstract]	'
Components of Net Periodic Benefit Costs	'
	The following summarizes the components of net periodic benefit costs:
		Three Months Ended June 30,
		Pension Benefits						Other Benefits
	(In millions)	2014			2013			2014			2013
	Components of net periodic benefit cost:
	Service cost	$	20		$	23		$	6		$	6
	Interest cost	18			18			9			6
	Expected return on plan assets	(26		)	(26		)	—			—
	Amortization – prior service credit	(11		)	(11		)	(1		)	—
	– actuarial loss	13			18			—			—
	– settlement loss	5			60			—			—
	Net periodic benefit cost	$	19		$	82		$	14		$	12
		Six Months Ended June 30,
		Pension Benefits						Other Benefits
	(In millions)	2014			2013			2014			2013
	Components of net periodic benefit cost:
	Service cost	$	43		$	46		$	13		$	12
	Interest cost	38			36			17			13
	Expected return on plan assets	(54		)	(53		)	—			—
	Amortization – prior service credit	(23		)	(22		)	(2		)	(2		)
	– actuarial loss	26			39			1			1
	– settlement loss	69			60			—			—
	Net periodic benefit cost	$	99		$	106		$	29		$	24

StockBased_Compensation_Plans_

Stock-Based Compensation Plans (Tables)	6 Months Ended
	Jun. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Summary of Stock Option Award Activity	'
	The following table presents a summary of our stock option award activity for the six months ended June 30, 2014:
		Number of Shares(a)		Weighted Average Exercise Price
	Outstanding at December 31, 2013	5,147,837		$	40.08
	Granted	446,310		85.02
	Exercised	(583,773	)	31.21
	Forfeited, canceled or expired	(20,761	)	49.67
	Outstanding at June 30, 2014	4,989,613		45.09
	(a)	Includes an immaterial number of stock appreciation rights.
Summary of Restricted Stock Award Activity	'
	The following table presents a summary of restricted stock award activity for the six months ended June 30, 2014:
		Shares of Restricted Stock ("RS")				Restricted Stock Units ("RSU")
		Number of Shares		Weighted Average Grant Date Fair Value		Number of Units		Weighted Average Grant Date Fair Value
	Outstanding at December 31, 2013	624,122		$	61.11	385,079		$	33.96
	Granted	232,594		88.19		12,889		89.16
	RS's Vested/RSU's Issued	(264,470	)	58.48		(398	)	60.11
	Forfeited	(16,446	)	65.72		(133	)	76.1
	Outstanding at June 30, 2014	575,800		73.13		397,437		35.71
Schedule of Performance Unit Awards	'
	The following table presents a summary of the activity for performance unit awards to be settled in shares for the six months ended June 30, 2014:
		Number of Units
	Outstanding at December 31, 2013	3,822,500
	Granted	2,033,700
	Settled	—
	Canceled	—
	Outstanding at June 30, 2014	5,856,200

Supplementary_Statistics_Table

Supplementary Statistics (Tables)	6 Months Ended
	Jun. 30, 2014
Text Block [Abstract]	'
Supplementary Statistics	'
	Supplementary Statistics (Unaudited)
		Three Months Ended						Six Months Ended
		June 30,						June 30,
	(In millions)	2014			2013			2014			2013
	Income from Operations by segment
	Refining & Marketing	$	1,260		$	903		$	1,622		$	2,008
	Speedway	94			123			152			190
	Pipeline Transportation(a)	81			58			153			109
	Items not allocated to segments:
	Corporate and other unallocated items(a)	(61		)	(64		)	(128		)	(131		)
	Pension settlement expenses	(5		)	(60		)	(69		)	(60		)
	Income from operations	$	1,369		$	960		$	1,730		$	2,116
	Capital Expenditures and Investments(b)(c)
	Refining & Marketing	$	235		$	134		$	413		$	1,554
	Speedway	44			76			76			112
	Pipeline Transportation	64			41			194			131
	Corporate and Other(d)	20			32			51			60
	Total	$	363		$	283		$	734		$	1,857
	(a)	Corporate overhead expenses attributable to MPLX are included in the Pipeline Transportation segment. These expenses are not allocated to the Refining & Marketing and Speedway segments.
	(b)	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
	(c)	The six months ended June 30, 2013 includes the acquisition of the Galveston Bay Refinery and Related Assets, comprised of total consideration, excluding inventory and other current assets, plus assumed liabilities. Total consideration includes the base purchase price and a fair-value estimate of $600 million for the contingent consideration. See Note 4 to the unaudited consolidated financial statements.
	(d)	Includes capitalized interest $7 million and $4 million for the three months ended June 30, 2014 and 2013, respectively, and $13 million and $8 million for the six months ended June 30, 2014 and 2013, respectively.
Operating Statistics	'
	Supplementary Statistics (Unaudited)
		Three Months Ended						Six Months Ended
		June 30,						June 30,
		2014			2013			2014			2013
	MPC Consolidated Refined Product Sales Volumes (thousands of barrels per day)(a)(b)	2,153			2,135			2,059			2,016
	Refining & Marketing Operating Statistics(b)
	Refining & Marketing refined product sales volume (thousands of barrels per day)(c)	2,145			2,125			2,048			2,004
	Refining & Marketing gross margin (dollars per barrel)(d)	$	16.02		$	13.11		$	15.28		$	14.14
	Crude oil capacity utilization percent(e)	98			99			91			96
	Refinery throughputs (thousands of barrels per day):(f)
	Crude oil refined	1,674			1,690			1,563			1,562
	Other charge and blendstocks	158			174			178			206
	Total	1,832			1,864			1,741			1,768
	Sour crude oil throughput percent	54			52			52			53
	WTI-priced crude oil throughput percent	17			22			19			22
	Refined product yields (thousands of barrels per day):(f)
	Gasoline	852			923			844			906
	Distillates	610			609			562			566
	Propane	37			40			36			36
	Feedstocks and special products	288			240			255			212
	Heavy fuel oil	27			31			28			31
	Asphalt	51			54			47			50
	Total	1,865			1,897			1,772			1,801
	Refinery direct operating costs (dollars per barrel):(g)
	Planned turnaround and major maintenance	$	0.94		$	0.73		$	1.98		$	0.93
	Depreciation and amortization	1.39			1.28			1.47			1.35
	Other manufacturing(h)	4.77			4.06			5.32			3.94
	Total	$	7.1		$	6.07		$	8.77		$	6.22
	Refining & Marketing Operating Statistics By Region - Gulf Coast(b)
	Refinery throughputs (thousands of barrels per day):(i)
	Crude oil refined	1,031			1,037			946			938
	Other charge and blendstocks	156			157			183			184
	Total	1,187			1,194			1,129			1,122
	Sour crude oil throughput percent	67			64			64			66
	WTI-priced crude oil throughput percent	2			11			3			9
	Refined product yields (thousands of barrels per day):(i)
	Gasoline	500			542			494			536
	Distillates	390			398			355			360
	Propane	25			25			23			22
	Feedstocks and special products	270			223			258			201
	Heavy fuel oil	16			20			15			19
	Asphalt	13			13			10			10
	Total	1,214			1,221			1,155			1,148
	Refinery direct operating costs (dollars per barrel):(g)
	Planned turnaround and major maintenance	$	0.57		$	0.6		$	2.11		$	0.72
	Depreciation and amortization	1.13			1			1.19			1.06
	Other manufacturing(h)	4.77			4.01			5.28			3.68
	Total	$	6.47		$	5.61		$	8.58		$	5.46
	Supplementary Statistics (Unaudited)
		Three Months Ended						Six Months Ended
		June 30,						June 30,
		2014			2013			2014			2013
	Refining & Marketing Operating Statistics By Region - Midwest
	Refinery throughputs (thousands of barrels per day):(i)
	Crude oil refined	643			653			617			624
	Other charge and blendstocks	45			54			46			55
	Total	688			707			663			679
	Sour crude oil throughput percent	34			34			34			35
	WTI-priced crude oil throughput percent	40			40			43			42
	Refined product yields (thousands of barrels per day):(i)
	Gasoline	352			383			350			371
	Distillates	220			211			207			206
	Propane	13			15			14			14
Feedstocks and special products	60			52			47			43
Heavy fuel oil	11			11			13			12
Asphalt	38			41			37			40
Total	694			713			668			686
Refinery direct operating costs (dollars per barrel):(g)
Planned turnaround and major maintenance	$	1.53		$	0.9		$	1.62		$	1.22
Depreciation and amortization	1.75			1.68			1.83			1.75
Other manufacturing(h)	4.47			3.96			4.97			4.2
Total	$	7.75		$	6.54		$	8.42		$	7.17
Speedway Operating Statistics
Convenience stores at period-end	1,492			1,468
Gasoline and distillate sales (millions of gallons)	806			781			1,579			1,526
Gasoline and distillate gross margin (dollars per gallon)(j)	$	0.1282		$	0.1738		$	0.122		$	0.1525
Merchandise sales (in millions)	$	830		$	806		$	1,552		$	1,517
Merchandise gross margin (in millions)	$	224		$	212		$	416		$	396
Merchandise gross margin percent	27.1		%	26.3		%	26.8		%	26.1		%
Same store gasoline sales volume (period over period)	(1.5		%)	—		%	(1.1		%)	0.3		%
Same store merchandise sales (period over period)(k)	4.6		%	4.5		%	4.9		%	2.8		%
Pipeline Transportation Operating Statistics
Pipeline throughputs (thousands of barrels per day):(l)
Crude oil pipelines	1,281			1,334			1,213			1,303
Refined products pipelines	871			959			845			939
Total	2,152			2,293			2,058			2,242
(a)	Total average daily volumes of refined product sales to wholesale, branded and retail (Speedway segment) customers.
(b)	Includes the impact of the Galveston Bay Refinery and Related Assets beginning on the February 1, 2013 acquisition date.
(c)	Includes intersegment sales.
(d)	Sales revenue less cost of refinery inputs and purchased products, divided by total refinery throughputs.
(e)	Based on calendar day capacity, which is an annual average that includes downtime for planned maintenance and other normal operating activities.
(f)	Excludes inter-refinery volumes of 43 mbpd and 37 mbpd for the three months ended June 30, 2014 and 2013, respectively, and 51 mbpd and 33 mbpd for the six months ended June 30, 2014 and 2013, respectively.
(g)	Per barrel of total refinery throughputs.
(h)	Includes utilities, labor, routine maintenance and other operating costs.
(i)	Includes inter-refinery transfer volumes.
(j)	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.
(k)	Excludes cigarettes.
(l)	On owned common-carrier pipelines, excluding equity method investments.

Description_of_the_Business_an2

Description of the Business and Basis of Presentation Basis of Presentation (Details) (Total costs and expenses, Increase in prior year bonus expense, USD $)	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014
Total costs and expenses | Increase in prior year bonus expense	'
Quantifying Misstatement in Current Year Financial Statements [Line Items]	'
Quantifying misstatement in current year financial statements, amount	$29

MPLX_LP_MPLX_LP_Detail

MPLX LP MPLX LP (Detail) (USD $)	6 Months Ended		0 Months Ended					0 Months Ended			6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Mar. 01, 2014	1-May-13	Mar. 01, 2014	Mar. 01, 2014	Oct. 31, 2012	Mar. 01, 2014	Jun. 30, 2014	Jun. 30, 2014	Apr. 30, 2013
			MPLX Pipe Line Holdings LP	MPLX Pipe Line Holdings LP	MPLX LP	MPLX LP	MPLX LP	MPLX LP	MPLX LP	MPLX LP	MPLX LP
					MPLX Revolver	Cash and cash equivalents	Butane Cavern	MPLX Pipe Line Holdings LP	General Partner and Limited Partner	General Partner	General Partner
											MPLX Pipe Line Holdings LP
Noncontrolling Interest [Line Items]	'	'	'	'	'	'	'	'	'	'	'
MPC's partnership interest in MPLX (in percentage)	'	'	'	'	'	'	'	'	73.60%	2.00%	'
Ownership interest (in percentage)	'	'	'	'	'	'	'	69.00%	'	'	51.00%
MPLX's partnership percent indirect interest in assets	'	'	'	'	'	'	100.00%	'	'	'	'
Additional interest sold	'	'	13.00%	5.00%	'	'	'	'	'	'	'
Proceeds from sale of ownership interest	'	'	$310	$100	'	'	'	'	'	'	'
Cash paid for acquisition	$42	$1,515	'	'	$270	$40	'	'	'	'	'

Acquisitions_and_Investments_A1

Acquisitions and Investments (Acquisition of Refinery and Related Logistics and Marketing Assets) (Detail) (USD $)	6 Months Ended		1 Months Ended			3 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Feb. 01, 2013	Jun. 30, 2014	Dec. 31, 2013	Sep. 30, 2014
			Galveston Bay Refinery and Related Assets	Galveston Bay Refinery and Related Assets	Galveston Bay Refinery and Related Assets	Galveston Bay Refinery and Related Assets
			site			Subsequent Event
			Pipeline
			Terminal
			BPCD
			BPD
			MW
Business Acquisition [Line Items]	'	'	'	'	'	'
Refinery capacity (in barrels per calendar day)	'	'	451,000	'	'	'
Intrastate natural gas liquid pipelines (in number of pipelines)	'	'	3	'	'	'
Number of light product terminals (in number of terminals)	'	'	4	'	'	'
Number of branded sites (in number of sites)	'	'	1,200	'	'	'
Electric cogeneration capacity, megawatt	'	'	1,040	'	'	'
Allocation of space on Colonial Pipeline (in barrels per day)	'	'	50,000	'	'	'
Cash paid for acquisition	$42,000,000	$1,515,000,000	$1,490,000,000	'	'	$180,000,000
Inventories	'	'	'	'	935,000,000	'
Total cumulative payment capped over six-year period	'	'	$700,000,000	$700,000,000	'	'
Term of payment of maximum earnout provision payable to the company, years	'	'	'6 years	'	'	'

Acquisitions_and_Investments_A2

Acquisitions and Investments Acquisition and Investments (Schedule of Acquisition Related Pro Forma Financial Information) (Details) (Galveston Bay Refinery and Related Assets, USD $)	6 Months Ended
In Millions, except Per Share data, unless otherwise specified	Jun. 30, 2013
Galveston Bay Refinery and Related Assets	'
Business Acquisition [Line Items]	'
Sales and other operating revenues (including consumer excise taxes)	$50,975
Net income attributable to MPC	$1,373
Net income attributable to MPC per share - basic	$4.21
Net income attributable to MPC per share - diluted	$4.19

Acquisitions_and_Investments_A3

Acquisitions and Investments Acquisitions and Investments (Pending Acquisition of Hess Retail Holdings LLC) (Details) (USD $)	6 Months Ended				3 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013		Jun. 30, 2014	Jun. 30, 2014	Sep. 30, 2014	Sep. 30, 2014
				Speedway	Hess Retail	Hess Retail	Hess Retail
				Store		Scenario, Forecast	Scenario, Forecast
						BPD	Speedway
							Store
Business Acquisition [Line Items]	'	'		'	'	'	'
Date of acquisition agreement	'	'		'	21-May-14	'	'
Allocation of space on Colonial Pipeline (in barrels per day)	'	'		'	'	40,000	'
Total consideration transferred	'	'		'	'	$2,874	'
Cash paid for acquisition	42	1,515		'	'	2,370	'
Consideration transferred, working capital	'	'		'	'	230	'
Consideration transferred, capital leases	$0	$6	[1]	'	'	$274	'
Number of states in which entity operates	'	'		9	'	'	23
Reason for business combination	'	'		'	'	'This acquisition will significantly expand our Speedway presence from nine to 23 states throughout the East Coast and Southeast and is aligned with our strategy to grow higher-valued, stable cash flow businesses. This acquisition will also enable us to further leverage our integrated refining and transportation operations, providing an outlet for an incremental 200,000 barrels per day of assured sales from our refining system.	'
[1]	Acquisition-date fair value of non-cash consideration associated with the Galveston Bay Refinery and Related Assets acquisition.

Acquisitions_and_Investments_A4

Acquisitions and Investments Acquisitions and Investments (Acquisitions of Convenience Stores) (Details) (Speedway, USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013
	Store
Speedway	'
Business Acquisition [Line Items]	'
Number of convenience stores acquired	9
Goodwill acquired during period	$8

Acquisitions_and_Investments_A5

Acquisitions and Investments Acquisitions and Investments (Acquisition of Biodiesel Facility) (Details) (USD $)	6 Months Ended		1 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Apr. 30, 2014	Apr. 01, 2014
			Felda Iffco Sdn Bhd [Member]	Felda Iffco Sdn Bhd [Member]
				gallons_per_year
Business Acquisition [Line Items]	'	'	'	'
Cash paid for acquisition	$42	$1,515	$40	'
Plant capacity volume	'	'	'	60,000,000

Acquisitions_and_Investments_A6

Acquisitions and Investments Acquisitions and Investments (Investments in Ethanol Companies) (Details) (USD $)	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2014	Oct. 01, 2013	Aug. 01, 2013	Aug. 01, 2013	Aug. 01, 2013	Aug. 01, 2013
In Millions, unless otherwise specified	TACE	TAME	TAME	TAAE	TAAE	Ethanol Interests From Mitsui	Ethanol Interests From Mitsui	Ethanol Interests From Mitsui	Ethanol Interests From Mitsui
			TAEI			Companies	TACE	TAEI	TAAE
Schedule of Equity Method Investments [Line Items]	'	'	'	'	'	'	'	'	'
Number of businesses in which ownership interests acquired	'	'	'	'	'	3	'	'	'
Cash paid to acquire equity method investments	'	'	'	'	'	$75	'	'	'
Ownership percentage acquired	'	'	'	'	'	'	24.00%	34.00%	40.00%
Equity method investments, ownership percentage	60.00%	67.00%	50.00%	43.00%	43.00%	'	'	'	'

Acquisitions_and_Investments_A7

Acquisitions and Investments Acquisitions and Investments (Investments in Pipeline Companies) (Details) (USD $)	6 Months Ended	9 Months Ended			0 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2014	Jan. 02, 2016	Jan. 02, 2016	Mar. 04, 2014	Jun. 30, 2014
	North Dakota Pipeline	North Dakota Pipeline	North Dakota Pipeline Class A Units	North Dakota Pipeline Class A Units	Explorer Pipeline	Explorer Pipeline
			Scenario, Forecast	Scenario, Forecast
				Maximum
Schedule of Equity Method Investments [Line Items]	'	'	'	'	'	'
Cash paid to acquire equity method investments	$75	$99	'	'	$77	'
Equity method investments, ownership percentage	37.50%	37.50%	27.00%	30.00%	'	25.00%
Ownership percentage acquired	'	'	'	'	7.00%	'

Related_Party_Transactions_Add

Related Party Transactions - Additional Information (Detail) (USD $)

Jun. 30, 2014

Oct. 01, 2013

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Dec. 31, 2013

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

In Millions, unless otherwise specified

TAAE

TAAE

TACE

TAME

Centennial

Centennial

Centennial

Centennial

Centennial

Explorer

LOCAP

LOOP

Related Party Transaction [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

Equity method investments, ownership percentage

43.00%

43.00%

60.00%

67.00%

50.00%

'

50.00%

'

'

25.00%

59.00%

51.00%

Operating pipeline revenue from related parties included in other income, Centennial

'

'

'

'

$1

$1

$1

$1

'

'

'

'

Long-term receivable from related party

'

'

'

'

$2

'

$2

'

$2

'

'

'

Related_Party_Transactions_Sal

Related Party Transactions - Sales to Related Parties (Detail) (Other equity method investees, USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Other equity method investees	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'
Sales to related parties	$2	$2	$4	$4

Related_Party_Transactions_Pur

Related Party Transactions - Purchases from Related Parties (Detail) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Related Party Transaction [Line Items]	'	'	'	'
Purchases from related parties	$130	$79	$289	$151
Centennial	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'
Purchases from related parties	-2	0	7	0
Explorer	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'
Purchases from related parties	9	0	22	0
LOCAP	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'
Purchases from related parties	5	4	10	8
LOOP	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'
Purchases from related parties	12	11	65	21
TAAE	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'
Purchases from related parties	26	0	42	0
TACE	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'
Purchases from related parties	30	24	57	50
TAME	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'
Purchases from related parties	48	37	82	67
Other equity method investees	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'
Purchases from related parties	$2	$3	$4	$5

Related_Party_Transactions_Rel

Related Party Transactions Related Party Transactions - Receivables From Related Parties (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Related Party Transaction [Line Items]	'	'
Current receivables from related parties	$3	$2
Centennial	'	'
Related Party Transaction [Line Items]	'	'
Current receivables from related parties	1	1
TAME	'	'
Related Party Transaction [Line Items]	'	'
Current receivables from related parties	$2	$1

Related_Party_Transactions_Pay

Related Party Transactions - Payables To Related Parties (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Related Party Transaction [Line Items]	'	'
Payables to related parties	$18	$16
Explorer	'	'
Related Party Transaction [Line Items]	'	'
Payables to related parties	3	0
LOCAP	'	'
Related Party Transaction [Line Items]	'	'
Payables to related parties	1	2
LOOP	'	'
Related Party Transaction [Line Items]	'	'
Payables to related parties	4	3
TAAE	'	'
Related Party Transaction [Line Items]	'	'
Payables to related parties	3	2
TACE	'	'
Related Party Transaction [Line Items]	'	'
Payables to related parties	2	4
TAME	'	'
Related Party Transaction [Line Items]	'	'
Payables to related parties	4	5
Other equity method investees	'	'
Related Party Transaction [Line Items]	'	'
Payables to related parties	$1	$0

Income_Per_Common_Share_Summar

Income Per Common Share - Summary of Earnings Per Common Share (Detail) (USD $)	3 Months Ended		6 Months Ended
In Millions, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Basic earnings per share:	'	'	'	'
Net income attributable to MPC	$855	$593	$1,054	$1,318
Income allocated to participating securities, basic	1	1	2	2
Income available to common stockholders - basic	854	592	1,052	1,316
Weighted average common shares outstanding (in shares)	287	322	290	326
Basic (in USD per share)	$2.97	$1.84	$3.63	$4.03
Diluted earnings per share:	'	'	'	'
Net income attributable to MPC	855	593	1,054	1,318
Income allocated to participating securities, diluted	1	1	2	2
Income available to common stockholders - diluted	$854	$592	$1,052	$1,316
Weighted average common shares outstanding (in shares)	287	322	290	326
Effect of dilutive securities (in shares)	2	2	2	2
Weighted average common shares, including dilutive effect (in shares)	289	324	292	328
Diluted (in USD per share)	$2.95	$1.83	$3.60	$4.01

Income_Per_Common_Share_Income

Income Per Common Share Income Per Common Share - Anti-dilutive Shares (Details) (Shares issued under stock-based compensation plans)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Shares issued under stock-based compensation plans	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive securities excluded from computation of earnings per share, amount	0	1	0	1

Equity_Additional_Information_

Equity - Additional Information (Detail) (USD $)	3 Months Ended			6 Months Ended			30 Months Ended	1 Months Ended	6 Months Ended	1 Months Ended
Share data in Millions, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013	Jun. 30, 2014	Jul. 31, 2014	Jun. 30, 2013	Jul. 31, 2014	Jul. 30, 2014
								Scenario, Forecast	Accelerated Share Repurchase Program November 2012	Subsequent Event	Subsequent Event
										Share Repurchase Authorization July 2014	Share Repurchase Authorization July 2014
Equity, Class of Treasury Stock [Line Items]	'	'		'		'	'	'	'	'	'
Stock repurchase plan authorized amount	$6,000,000,000	'		$6,000,000,000		'	$6,000,000,000	'	'	'	$2,000,000,000
Cash paid for shares repurchased	459,000,000	882,000,000		1,148,000,000		1,313,000,000	5,290,000,000	12,000,000	'	'	'
Stock repurchase plan remaining authorized amount	$709,000,000	'		$709,000,000		'	$709,000,000	'	'	'	'
Ending date of share repurchase authorization	'	'		30-Sep-15		'	'	'	'	30-Jul-16	'
Number of shares repurchased	5	11	[1]	13	[1]	17	78	'	1	'	'
Effective average cost per delivered share	$88.14	$80.31		$87.82		$80.54	$67.65	'	'	'	'
[1]	The six months ended June 30, 2013 includes one million shares received under the November 2012 accelerated share repurchase program, which were paid for in 2012.

Equity_Share_Repurchases_Trans

Equity - Share Repurchases Transacted Through ASR Programs and Open Market Transactions (Detail) (USD $)	3 Months Ended			6 Months Ended			30 Months Ended
In Millions, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013	Jun. 30, 2014
Equity, Class of Treasury Stock [Line Items]	'	'		'		'	'
Number of shares repurchased	5	11	[1]	13	[1]	17	78
Cash paid for shares repurchased	$459	$882		$1,148		$1,313	$5,290
Effective average cost per delivered share	$88.14	$80.31		$87.82		$80.54	$67.65
Accelerated Share Repurchase Program November 2012	'	'		'		'	'
Equity, Class of Treasury Stock [Line Items]	'	'		'		'	'
Number of shares repurchased	'	'		'		1	'
[1]	The six months ended June 30, 2013 includes one million shares received under the November 2012 accelerated share repurchase program, which were paid for in 2012.

Segment_Information_Additional

Segment Information - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2014
	Segment
Segment Reporting [Abstract]	'
Number of reportable segments	3

Segment_Information_Income_Fro

Segment Information - Income From Operations Attributable To Operating Segments (Detail) (USD $)	3 Months Ended				6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	($26,844)		($25,677)		($50,129)		($49,007)
Income from operations	1,369		960		1,730		2,116
Income (loss) from equity method investments	57		7		92		7
Depreciation and amortization	325		302		645		589
Capital expenditures and investments	363	[1],[2],[3]	283	[1],[2],[3]	734	[1],[2]	1,857	[1],[2]
Refining & Marketing	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	-22,917		-21,890		-42,727		-41,764
Speedway	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	-3,908		-3,768		-7,366		-7,209
Pipeline Transportation	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	-19		-19		-36		-40
Reportable Segment	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	-26,844		-25,677		-50,129		-49,013
Intersegment Eliminations	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	2,722	[4]	2,554	[4]	5,085	[4]	4,858	[4]
Intersegment Eliminations | Refining & Marketing	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	2,590	[4]	2,434	[4]	4,823	[4]	4,633	[4]
Intersegment Eliminations | Speedway	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	1	[4]	1	[4]	2	[4]	2	[4]
Intersegment Eliminations | Pipeline Transportation	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	131	[4]	119	[4]	260	[4]	223	[4]
Operating Segments	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	-29,566		-28,231		-55,214		-53,871
Income from operations	1,435	[5]	1,084	[5]	1,927	[5]	2,307	[5]
Income (loss) from equity method investments	57		7		92		7
Depreciation and amortization	312	[6]	297	[6]	620	[6]	578	[6]
Capital expenditures and investments	343	[2]	251	[2]	683	[2]	1,797	[2],[7]
Operating Segments | Refining & Marketing	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	-25,507		-24,324		-47,550		-46,397
Income from operations	1,260		903		1,622		2,008
Income (loss) from equity method investments	35		3		59		-1
Depreciation and amortization	264	[6]	252	[6]	525	[6]	488	[6]
Capital expenditures and investments	235	[2]	134	[2],[7]	413	[2]	1,554	[2],[7]
Operating Segments | Speedway	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	-3,909		-3,769		-7,368		-7,211
Income from operations	94		123		152		190
Income (loss) from equity method investments	0		0		0		0
Depreciation and amortization	29	[6]	27	[6]	57	[6]	54	[6]
Capital expenditures and investments	44	[2]	76	[2]	76	[2]	112	[2]
Operating Segments | Pipeline Transportation	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Revenues	-150		-138		-296		-263
Income from operations	81	[5]	58	[5]	153	[5]	109	[5]
Income (loss) from equity method investments	22		4		33		8
Depreciation and amortization	19	[6]	18	[6]	38	[6]	36	[6]
Capital expenditures and investments	$64	[2]	$41	[2],[7]	$194	[2]	$131	[2],[7]
[1]	The six months ended June 30, 2013 includes the acquisition of the Galveston Bay Refinery and Related Assets, comprised of total consideration, excluding inventory and other current assets, plus assumed liabilities. Total consideration includes the base purchase price and a fair-value estimate of $600 million for the contingent consideration. See Note 4 to the unaudited consolidated financial statements.
[2]	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
[3]	Includes capitalized interest $7 million and $4 million for the three months ended June 30, 2014 and 2013, respectively, and $13 million and $8 million for the six months ended June 30, 2014 and 2013, respectively.
[4]	Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties
[5]	Corporate overhead expenses attributable to MPLX are included in the Pipeline Transportation segment. These expenses are not allocated to the Refining & Marketing and Speedway segments.
[6]	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.
[7]	The Refining & Marketing and Pipeline Transportation segments include the acquisition of the Galveston Bay Refinery and Related Assets. See Note 4.

Segment_Information_Reconcilia

Segment Information - Reconciliation Of Segment Income From Operations To Income Before Income Taxes (Detail) (USD $)	3 Months Ended				6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]	'		'		'		'
Income from operations	$1,369		$960		$1,730		$2,116
Net interest and other financial income (costs)	-48		-45		-94		-93
Income before income taxes	1,321		915		1,636		2,023
Operating Segments	'		'		'		'
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]	'		'		'		'
Income from operations	1,435	[1]	1,084	[1]	1,927	[1]	2,307	[1]
Corporate and Other	'		'		'		'
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]	'		'		'		'
Income from operations	-61	[1],[2]	-64	[1],[2]	-128	[1],[3]	-131	[1],[2]
Segment Reconciling Items	'		'		'		'
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]	'		'		'		'
Pension settlement expenses	($5)	[4]	($60)	[4]	($69)	[4]	($60)	[4]
[1]	Corporate overhead expenses attributable to MPLX are included in the Pipeline Transportation segment. These expenses are not allocated to the Refining & Marketing and Speedway segments.
[2]	Corporate and other unallocated items consists primarily of MPC’s corporate administrative expenses and costs related to certain non-operating assets.
[3]	Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties
[4]	See Note 18.

Segment_Information_Reconcilia1

Segment Information - Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures (Detail) (USD $)	3 Months Ended				6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures [Line Items]	'		'		'		'
Capital expenditures and investments	$363	[1],[2],[3]	$283	[1],[2],[3]	$734	[1],[2]	$1,857	[1],[2]
Plus: Items not allocated to segments:	'		'		'		'
Capital expenditures	322	[4],[5]	277	[4],[5]	570	[4],[5]	1,846	[4],[5]
Operating Segments	'		'		'		'
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures [Line Items]	'		'		'		'
Capital expenditures and investments	343	[2]	251	[2]	683	[2]	1,797	[2],[6]
Less: Investments in equity method investees	41		6		164		11
Corporate and Other	'		'		'		'
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures [Line Items]	'		'		'		'
Capital expenditures and investments	20	[2],[3]	32	[2],[3]	51	[1],[2]	60	[1],[2]
Plus: Items not allocated to segments:	'		'		'		'
Capital expenditures not allocated to segments	13		28		38		52
Capitalized interest	$7		$4		$13		$8
[1]	The six months ended June 30, 2013 includes the acquisition of the Galveston Bay Refinery and Related Assets, comprised of total consideration, excluding inventory and other current assets, plus assumed liabilities. Total consideration includes the base purchase price and a fair-value estimate of $600 million for the contingent consideration. See Note 4 to the unaudited consolidated financial statements.
[2]	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
[3]	Includes capitalized interest $7 million and $4 million for the three months ended June 30, 2014 and 2013, respectively, and $13 million and $8 million for the six months ended June 30, 2014 and 2013, respectively.
[4]	Capital expenditures include changes in capital accruals and acquisitions.
[5]	See Note 16 for a reconciliation of total capital expenditures to additions to property, plant and equipment as reported in the consolidated statements of cash flows.
[6]	The Refining & Marketing and Pipeline Transportation segments include the acquisition of the Galveston Bay Refinery and Related Assets. See Note 4.

Segment_Information_Reconcilia2

Segment Information - Reconciliation Of Total Revenues To Sales And Other Operating Revenues (Detail) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Reporting, Revenue Reconciling Item [Line Items]	'	'	'	'
Sales and other operating revenues (including consumer excise taxes)	$26,844	$25,677	$50,129	$49,007
Corporate and Other	'	'	'	'
Segment Reporting, Revenue Reconciling Item [Line Items]	'	'	'	'
Sales and other operating revenues (including consumer excise taxes)	0	0	0	-6
Reportable Segment	'	'	'	'
Segment Reporting, Revenue Reconciling Item [Line Items]	'	'	'	'
Sales and other operating revenues (including consumer excise taxes)	$26,844	$25,677	$50,129	$49,013

Segment_Information_Segment_In

Segment Information Segment Information - Total Assets By Reportable Segment (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Segment Reporting, Asset Reconciling Item [Line Items]	'	'
Assets	$29,376	$28,385
Operating Segments | Refining & Marketing	'	'
Segment Reporting, Asset Reconciling Item [Line Items]	'	'
Assets	20,708	19,573
Operating Segments | Speedway	'	'
Segment Reporting, Asset Reconciling Item [Line Items]	'	'
Assets	2,185	2,064
Operating Segments | Pipeline Transportation	'	'
Segment Reporting, Asset Reconciling Item [Line Items]	'	'
Assets	2,135	1,947
Corporate and Other	'	'
Segment Reporting, Asset Reconciling Item [Line Items]	'	'
Assets	$4,348	$4,801

Other_Items_Net_Interest_And_O

Other Items - Net Interest And Other Financial Income (Costs) (Detail) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Interest:	'	'	'	'
Interest income	$1	$3	$3	$5
Interest expense	-49	-49	-98	-97
Interest capitalized	7	4	13	8
Total net interest	-41	-42	-82	-84
Other:	'	'	'	'
Net foreign currency gains (losses)	-1	2	-1	1
Bank service and other fees	-6	-5	-11	-10
Total other	-7	-3	-12	-9
Net interest and other financial income (costs)	($48)	($45)	($94)	($93)

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Income Tax Disclosure [Abstract]	'	'	'	'
Combined federal, state and foreign income tax rate	35.00%	35.00%	35.00%	34.00%
Statutory rate applied to income before income taxes	'	'	35.00%	'
Tax settlement with Marathon Oil Corporation	'	$39	'	$39
Unrecognized benefits	$20	'	$20	'

Inventories_Summary_Of_Invento

Inventories - Summary Of Inventories (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Inventory Disclosure [Abstract]	'	'
Crude oil and refinery feedstocks	$2,835	$1,797
Refined products	2,367	2,367
Materials and supplies	333	425
Merchandise	86	100
Total (at cost)	$5,621	$4,689

Inventories_Additional_Informa

Inventories - Additional Information (Detail) (USD $)	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
Inventory Disclosure [Abstract]	'	'
Impact on revenues and costs as a result of LIFO liquidations	$0	$0

Property_Plant_And_Equipment_S

Property, Plant And Equipment - Summary Of Property, Plant And Equipment (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Property, Plant and Equipment [Line Items]	'	'
Property, plant and equipment, gross	$22,277	$21,793
Less accumulated depreciation	8,427	7,872
Net property, plant and equipment	13,850	13,921
Operating Segments | Refining & Marketing	'	'
Property, Plant and Equipment [Line Items]	'	'
Property, plant and equipment, gross	17,329	16,982
Operating Segments | Speedway	'	'
Property, Plant and Equipment [Line Items]	'	'
Property, plant and equipment, gross	2,412	2,344
Operating Segments | Pipeline Transportation	'	'
Property, Plant and Equipment [Line Items]	'	'
Property, plant and equipment, gross	1,948	1,921
Corporate and Other	'	'
Property, Plant and Equipment [Line Items]	'	'
Property, plant and equipment, gross	$588	$546

Fair_Value_Measurements_Assets

Fair Value Measurements - Assets and Liabilities Accounted for at Fair Value on Recurring Basis (Detail) (USD $)	Jun. 30, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Cash collateral netted with derivative liabilities	$47		$32
Liabilities, current	370		159
Fair Value, Measurements, Recurring	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Commodity derivative instruments, assets - netting and collateral	-44	[1]	-21	[1]
Commodity derivative instruments, assets - net	0	[2]	0	[2]
Commodity derivative instruments, assets - collateral pledged not offset	60		61
Other assets	2		2
Total assets at fair value	2		2
Commodity derivative instruments, liabilities - netting and collateral	91	[1]	53	[1]
Commodity derivative instruments, liabilities - net	0	[2]	0	[2]
Commodity derivative instruments, liabilities - collateral pledged not offset	0		0
Contingent consideration, liability	647	[3]	625	[3]
Total liabilities at fair value	647		625
Level 1 | Fair Value, Measurements, Recurring	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Commodity derivative instruments, assets - gross	44		21
Other assets	2		2
Total assets at fair value	46		23
Commodity derivative instruments, liabilities - gross	91		53
Contingent consideration, liability	0		0
Total liabilities at fair value	91		53
Level 2 | Fair Value, Measurements, Recurring	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Commodity derivative instruments, assets - gross	0		0
Other assets	0		0
Total assets at fair value	0		0
Commodity derivative instruments, liabilities - gross	0		0
Contingent consideration, liability	0		0
Total liabilities at fair value	0		0
Level 3 | Fair Value, Measurements, Recurring	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'
Commodity derivative instruments, assets - gross	0		0
Other assets	0		0
Total assets at fair value	0		0
Commodity derivative instruments, liabilities - gross	0		0
Contingent consideration, liability	647	[3]	625	[3]
Total liabilities at fair value	$647		$625
[1]	Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of June 30, 2014 and December 31, 2013, cash collateral of $47 million and $32 million, respectively, was netted with mark-to-market derivative liabilities.
[2]	We have no derivative contracts that are subject to master netting arrangements that are reflected gross on the balance sheet.
[3]	Includes $370 million and $159 million classified as current at June 30, 2014 and December 31, 2013, respectively.

Fair_Value_Measurements_Narrat

Fair Value Measurements - Narrative (Detail) (USD $)

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

6 Months Ended

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Feb. 01, 2013

Jun. 30, 2014

Jun. 30, 2014

Fair Value, Measurements, Recurring

Fair Value, Measurements, Recurring

Fair Value, Measurements, Recurring

Fair Value, Measurements, Recurring

Fair Value, Measurements, Recurring

Fair Value, Measurements, Recurring

Fair Value, Measurements, Recurring

Fair Value, Measurements, Recurring

Fair Value, Measurements, Nonrecurring

Fair Value, Measurements, Nonrecurring

Galveston Bay Refinery and Related Assets

Galveston Bay Refinery and Related Assets

Galveston Bay Refinery and Related Assets

Galveston Bay Refinery and Related Assets

Derivative

Derivative

Derivative

Derivative

Contingent Consideration

Contingent Consideration

Contingent Consideration

Contingent Consideration

Fair Value, Measurements, Recurring

Fair Value, Measurements, Recurring

Minimum

Maximum

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum earnout payment, year one

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$200,000,000

'

'

Maximum earnout payment, year two

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

200,000,000

'

'

Maximum earnout payment, year three

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

200,000,000

'

'

Maximum earnout payment, year four

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

250,000,000

'

'

Maximum earnout payment, year five

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

250,000,000

'

'

Maximum earnout payment, year six

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

250,000,000

'

'

Total cumulative payment capped over six-year period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

700,000,000

700,000,000

'

'

Range of internal and external crack spread forecast per barrel

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

14

19

Discount rate

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5.00%

10.00%

Unrealized losses included in net income

-8,000,000

-11,000,000

-22,000,000

-11,000,000

0

0

0

0

-8,000,000

-11,000,000

-22,000,000

-11,000,000

'

'

'

'

'

'

Other asset impairment charges

'

'

'

'

'

'

'

'

'

'

'

'

11,000,000

0

'

'

'

'

Impairment of long-lived assets held-for-use

'

'

'

'

'

'

'

'

'

'

'

'

$0

$8,000,000

'

'

'

'

Fair_Value_Measurements_Reconc

Fair Value Measurements - Reconciliation of Net Beginning and Ending Balances Recorded for Net Assets and Liabilities Classified as Level 3 (Detail) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'	'	'	'
Beginning balance	$639	$600	$625	$0
Contingent consideration agreement	0	0	0	600
Unrealized losses included in net income	-8	-11	-22	-11
Ending balance	$647	$611	$647	$611

Fair_Value_Measurements_Fair_V

Fair Value Measurements Fair Value Measurements - Assets Measured at Fair Value on Nonrecurring Basis (Details) (Fair Value, Measurements, Nonrecurring, USD $)	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
Fair Value, Measurements, Nonrecurring	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Property, plant, and equipment, fair value	$0	$1
Impairment of long-lived assets held-for-use	0	8
Other assets, fair value	0	0
Other asset impairment charges	$11	$0

Fair_Value_Measurements_Financ

Fair Value Measurements - Financial Instruments at Fair Value, Excluding Derivative Financial Instruments and Contingent Consideration (Detail) (USD $)	Jun. 30, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
Fair Value	'		'
Financial assets:	'		'
Investments	$25		$336
Other assets	31		31
Total financial assets	56		367
Financial liabilities:	'		'
Long-term debt	3,691	[1]	3,306	[1]
Deferred credits and other liabilities	20		21
Total financial liabilities	3,711		3,327
Carrying Value	'		'
Financial assets:	'		'
Investments	2		14
Other assets	29		30
Total financial assets	31		44
Financial liabilities:	'		'
Long-term debt	3,254	[1]	3,001	[1]
Deferred credits and other liabilities	20		21
Total financial liabilities	$3,274		$3,022
[1]	Excludes capital leases

Derivatives_Classification_of_

Derivatives - Classification of Gross Fair Values of Derivative Instruments, Excluding Cash Collateral (Detail) (Commodity derivatives, Other current assets, USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Commodity derivatives | Other current assets	'	'
Derivatives, Fair Value [Line Items]	'	'
Asset	$44	$21
Liability	$91	$53

Derivatives_Open_Commodity_Der

Derivatives - Open Commodity Derivative Contracts (Detail)	6 Months Ended
	Jun. 30, 2014
Crude Oil Exchange-Traded	'
Derivative [Line Items]	'
Percentage of derivative contracts expiring in the period	100.00%
Derivative contract expiration date	30-Sep-14
Crude Oil Exchange-Traded | Long	'
Derivative [Line Items]	'
Notional Contracts (in thousands of Total Barrels)	14,775,000	[1]
Crude Oil Exchange-Traded | Short	'
Derivative [Line Items]	'
Notional Contracts (in thousands of Total Barrels)	33,812,000	[1]
Refined Products Exchange-Traded	'
Derivative [Line Items]	'
Percentage of derivative contracts expiring in the period	100.00%
Derivative contract expiration date	30-Sep-14
Refined Products Exchange-Traded | Long	'
Derivative [Line Items]	'
Notional Contracts (in thousands of Total Barrels)	4,618,000
Refined Products Exchange-Traded | Short	'
Derivative [Line Items]	'
Notional Contracts (in thousands of Total Barrels)	2,541,000
[1]	100 percent of these contracts expire in the third quarter of 2014.

Derivatives_Effect_of_Commodit

Derivatives - Effect of Commodity Derivative Instruments in Statements of Income (Detail) (Commodity derivatives, USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Gain (Loss)	($116)	$54	($167)	($5)
Sales and other operating revenues	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Gain (Loss)	-2	3	8	4
Cost of revenues	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Gain (Loss)	($114)	$51	($175)	($9)

Debt_Outstanding_Borrowings_De

Debt - Outstanding Borrowings (Detail) (USD $)	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014		Dec. 31, 2013
Debt Instrument [Line Items]	'		'
Total	$3,639		$3,395
Unamortized discount	-10		-10
Fair value adjustments	9	[1]	11	[1]
Amounts due within one year	-26		-23
Total long-term debt due after one year	3,612		3,373
Interest Rate Swap	'		'
Debt Instrument [Line Items]	'		'
Deferred gain on discontinuation of interest rate fair value hedge	20		'
Consolidated subsidiaries: | Capital Lease Obligations	'		'
Debt Instrument [Line Items]	'		'
Capital lease obligations	384		395
Debt instrument maturity year, start	1-Jan-14		'
Debt instrument maturity year, end	31-Dec-28		'
MPC Revolver	'		'
Debt Instrument [Line Items]	'		'
Borrowings outstanding	0		0
Line of credit facility, expiration date	14-Sep-17		'
3.500% senior notes due March 1, 2016	'		'
Debt Instrument [Line Items]	'		'
Senior notes	750		750
Debt instrument, maturity date	1-Mar-16		'
Debt instrument, interest rate	3.50%		'
5.125% senior notes due March 1, 2021	'		'
Debt Instrument [Line Items]	'		'
Senior notes	1,000		1,000
Debt instrument, maturity date	1-Mar-21		'
Debt instrument, interest rate	5.13%		'
6.500% senior notes due March 1, 2041	'		'
Debt Instrument [Line Items]	'		'
Senior notes	1,250		1,250
Debt instrument, maturity date	1-Mar-41		'
Debt instrument, interest rate	6.50%		'
MPLX Revolver | MPLX Operations LLC	'		'
Debt Instrument [Line Items]	'		'
Borrowings outstanding	255		0
Line of credit facility, expiration date	31-Oct-17		'
Trade Receivables Securitization | Consolidated subsidiaries:	'		'
Debt Instrument [Line Items]	'		'
Trade receivables securitization facility	$0		$0
Line of credit facility, expiration date	31-Dec-16		'
[1]	The $20 million gain on the termination of our interest rate swap agreements in 2012 is being amortized over the remaining life of the 3.50 percent senior notes.

Debt_Additional_Information_De

Debt - Additional Information (Detail) (USD $)	3 Months Ended	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2014	Dec. 31, 2013
MPC Revolver	'	'	'
Line of Credit Facility [Line Items]	'	'	'
Borrowings outstanding	$0	$0	$0
Line of credit facility, expiration date	'	14-Sep-17	'
MPLX Operations LLC | MPLX Revolver	'	'	'
Line of Credit Facility [Line Items]	'	'	'
Borrowings outstanding	255	255	0
Line of credit facilitiy, borrowings during period	'	270	'
Interest rate during period	1.50%	'	'
Line of credit facility, repayments during period	'	15	'
Remaining borrowing capacity	245	245	'
Remaining borrowing capacity, percentage	49.00%	49.00%	'
Line of credit facility, expiration date	'	31-Oct-17	'
Revolving Credit Facility | MPLX Operations LLC | MPLX Revolver	'	'	'
Line of Credit Facility [Line Items]	'	'	'
Borrowings outstanding	255	255	'
Letter of Credit | MPLX Operations LLC | MPLX Revolver	'	'	'
Line of Credit Facility [Line Items]	'	'	'
Borrowings outstanding	$0	$0	'

Supplemental_Cash_Flow_Informa2

Supplemental Cash Flow Information - Summary of Supplemental Cash Flow Information (Detail) (USD $)	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
Net cash provided by operating activities included:	'	'
Interest paid (net of amounts capitalized)	$82	$86
Net income taxes paid to taxing authorities	299	719
Non-cash investing and financing activities:	'	'
Capital lease obligations increase	0	61
Property, plant and equipment sold	4	0
Property, plant and equipment acquired	4	0
Acquisition:	'	'
Contingent consideration	0	600	[1]
Payable to seller	$0	$6	[1]
[1]	Acquisition-date fair value of non-cash consideration associated with the Galveston Bay Refinery and Related Assets acquisition.

Supplemental_Cash_Flow_Informa3

Supplemental Cash Flow Information - Reconciliation of Additions to Property, Plant and Equipment to Total Capital Expenditures (Detail) (USD $)	3 Months Ended				6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Supplemental Cash Flow Elements [Abstract]	'		'		'		'
Additions to property, plant and equipment per consolidated statements of cash flows	'		'		$569		$424
Non-cash additions to property, plant and equipment	'		'		4		0
Acquisitions	'		'		27	[1]	1,391	[1]
Asset retirement expenditures	'		'		1		0
Increase (decrease) in capital accruals	'		'		-31		31
Total capital expenditures	$322	[2],[3]	$277	[2],[3]	$570	[2],[3]	$1,846	[2],[3]
[1]	The 2014 acquisition excludes the inventory and other current assets acquired but includes assumed liabilities. The 2013 acquisition includes the acquisition of the Galveston Bay Refinery and Related Assets, comprised of total consideration, excluding inventory and other current assets, plus assumed liabilities. Total consideration for the Galveston Bay Refinery and Related Assets includes the base purchase price and a fair-value estimate of $600 million for the contingent consideration. See Note 4.
[2]	Capital expenditures include changes in capital accruals and acquisitions.
[3]	See Note 16 for a reconciliation of total capital expenditures to additions to property, plant and equipment as reported in the consolidated statements of cash flows.

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Loss - Changes in Accumulated Other Comprehensive Loss by Component (Detail) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014		Jun. 30, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'		'
Beginning balance	'	'	($204)		($464)
Other comprehensive income (loss) before reclassifications	'	'	-58		163
Amounts reclassified from accumulated other comprehensive loss:	'	'	'		'
Amortization - prior service credit	'	'	-25	[1]	-24	[1]
Amortization of actuarial loss	'	'	27	[1]	40	[1]
Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Settlement Gain Loss Before Tax	'	'	69		60
Tax effect	'	'	-27		-29
Other comprehensive income (loss)	-13	128	-14		210
Ending balance	-218	-254	-218		-254
Accumulated Defined Benefit Plans Adjustment | Pension Benefits	'	'	'		'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'		'
Beginning balance	'	'	-161		-432
Other comprehensive income (loss) before reclassifications	'	'	-65		158
Amounts reclassified from accumulated other comprehensive loss:	'	'	'		'
Amortization - prior service credit	'	'	-23	[1]	-22	[1]
Amortization of actuarial loss	'	'	26	[1]	39	[1]
Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Settlement Gain Loss Before Tax	'	'	69		60
Tax effect	'	'	-28		-29
Other comprehensive income (loss)	'	'	-21		206
Ending balance	-182	-226	-182		-226
Accumulated Defined Benefit Plans Adjustment | Other Benefits	'	'	'		'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'		'
Beginning balance	'	'	-50		-36
Other comprehensive income (loss) before reclassifications	'	'	8		3
Amounts reclassified from accumulated other comprehensive loss:	'	'	'		'
Amortization - prior service credit	'	'	-2	[1]	-2	[1]
Amortization of actuarial loss	'	'	1	[1]	1	[1]
Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Settlement Gain Loss Before Tax	'	'	0		0
Tax effect	'	'	1		0
Other comprehensive income (loss)	'	'	8		2
Ending balance	-42	-34	-42		-34
Gain on Cash Flow Hedge	'	'	'		'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'		'
Beginning balance	'	'	4		4
Other comprehensive income (loss) before reclassifications	'	'	0		0
Amounts reclassified from accumulated other comprehensive loss:	'	'	'		'
Tax effect	'	'	0		0
Other comprehensive income (loss)	'	'	0		0
Ending balance	4	4	4		4
Workers Compensation	'	'	'		'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'		'
Beginning balance	'	'	3		0
Other comprehensive income (loss) before reclassifications	'	'	-1		2
Amounts reclassified from accumulated other comprehensive loss:	'	'	'		'
Tax effect	'	'	0		0
Other comprehensive income (loss)	'	'	-1		2
Ending balance	$2	$2	$2		$2
[1]	These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 18.

Defined_Benefit_Pension_and_Ot2

Defined Benefit Pension and Other Postretirement Plans - Components of Net Periodic Benefit Costs (Detail) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Pension Benefits	'	'	'	'
Components of net periodic benefit cost:	'	'	'	'
Service cost	$20	$23	$43	$46
Interest cost	18	18	38	36
Expected return on plan assets	-26	-26	-54	-53
Amortization – prior service credit	-11	-11	-23	-22
Amortization – actuarial loss	13	18	26	39
Amortization - settlement loss	-5	-60	-69	-60
Net periodic benefit cost	19	82	99	106
Other Benefits	'	'	'	'
Components of net periodic benefit cost:	'	'	'	'
Service cost	6	6	13	12
Interest cost	9	6	17	13
Expected return on plan assets	0	0	0	0
Amortization – prior service credit	-1	0	-2	-2
Amortization – actuarial loss	0	0	1	1
Amortization - settlement loss	0	0	0	0
Net periodic benefit cost	$14	$12	$29	$24

Defined_Benefit_Pension_and_Ot3

Defined Benefit Pension and Other Postretirement Plans - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Pension Benefits	'	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'	'
Amortization - settlement loss	($5)	($60)	($69)	($60)
Pension Benefits | Funded Pension Plans	'	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'	'
Employer contributions	'	'	0	'
Pension Benefits | Unfunded Pension Plans	'	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'	'
Defined benefit plan, benefits paid	'	'	9	'
Other Benefits	'	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'	'
Amortization - settlement loss	0	0	0	0
Other Benefits | Unfunded Pension Plans	'	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'	'
Defined benefit plan, benefits paid	'	'	$10	'

StockBased_Compensation_Plans_1

Stock-Based Compensation Plans - Summary of Stock Option Award Activity (Detail) (Stock Options, USD $)	6 Months Ended
	Jun. 30, 2014
Stock Options	'
Number of Shares	'
Outstanding, beginning balance	5,147,837	[1]
Granted	446,310	[1]
Exercised	-583,773	[1]
Forfeited, canceled or expired	-20,761	[1]
Outstanding, ending balance	4,989,613	[1]
Weighted Average Exercise Price	'
Outstanding, beginning balance (in USD per share)	$40.08
Granted (in USD per share)	$85.02
Exercised (in USD per share)	$31.21
Forfeited, canceled or expired (in USD per share)	$49.67
Outstanding, ending balance (in USD per share)	$45.09
[1]	Includes an immaterial number of stock appreciation rights.

StockBased_Compensation_Plans_2

Stock-Based Compensation Plans - Narrative (Detail) (USD $)	6 Months Ended
	Jun. 30, 2014
Stock Options	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Grant date fair value (in USD per share)	$25.37
Implied volatility rate weighting (in percentage)	50.00%
Historical volatility rate weighting (in percentage)	50.00%
Performance Unit Awards	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Grant date fair value (in USD per unit)	$1.02

StockBased_Compensation_Plans_3

Stock-Based Compensation Plans - Summary of Restricted Stock Award Activity (Detail) (USD $)	6 Months Ended
	Jun. 30, 2014
Restricted Stock	'
Number of Shares	'
Outstanding, beginning balance	624,122
Granted	232,594
RS's Vested/RSU's Issued	-264,470
Forfeited	-16,446
Outstanding, ending balance	575,800
Weighted Average Grant Date Fair Value	'
Outstanding, beginning balance (in USD per share)	$61.11
Granted (in USD per share)	$88.19
RS's Vested/RSU's Issued (in USD per share)	$58.48
Forfeited (in USD per share)	$65.72
Outstanding, ending balance (in USD per share)	$73.13
Restricted Stock Units	'
Number of Shares	'
Outstanding, beginning balance	385,079
Granted	12,889
RS's Vested/RSU's Issued	-398
Forfeited	-133
Outstanding, ending balance	397,437
Weighted Average Grant Date Fair Value	'
Outstanding, beginning balance (in USD per share)	$33.96
Granted (in USD per share)	$89.16
RS's Vested/RSU's Issued (in USD per share)	$60.11
Forfeited (in USD per share)	$76.10
Outstanding, ending balance (in USD per share)	$35.71

StockBased_Compensation_Plans_4

Stock-Based Compensation Plans - Summary of Performance Unit Awards (Detail) (Performance Unit Awards)	6 Months Ended
	Jun. 30, 2014
Performance Unit Awards	'
Number of Units	'
Outstanding, beginning balance	3,822,500
Granted	2,033,700
Settled	0
Canceled	0
Outstanding, ending balance	5,856,200

Commitments_and_Contingencies_

Commitments and Contingencies (Detail) (USD $)

6 Months Ended

6 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Jun. 30, 2014

Feb. 01, 2013

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Hess Retail

Galveston Bay Refinery and Related Assets

Galveston Bay Refinery and Related Assets

North Dakota Pipeline

Indemnification Agreement

Other Guarantees

Guarantee of Indebtedness of Others

Master Shelf Agreement

Standby Letters of Credit

Pending Litigation

Pending Litigation

Marathon Oil Companies

Equity method investees

Financial Guarantee

Financial Guarantee

Financial Guarantee

Emergency Pricing And Consumer Protection Laws

LOOP and LOCAP LLC

Centennial

TAME

Loss Contingencies [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

Loss contingency, inestimable loss

'

'

'

'

'

'

'

'

'

'

'

'For matters for which we have not recorded an accrued liability, we are unable to estimate a range of possible loss because the issues involved have not been fully developed through pleadings and discovery.

'

Accrued liabilities for remediation

$137,000,000

$123,000,000

'

'

'

'

'

'

'

'

'

'

'

Receivables for recoverable costs

51,000,000

51,000,000

'

'

'

'

'

'

'

'

'

'

'

Alleged amount overcharged from customers

'

'

'

'

'

'

'

'

'

'

'

'

89,000,000

Loss contingency, period of occurrence

'

'

'

'

'

'

'

'

'

'

'

'

'during September and October 2005

Plaintiff

'

'

'

'

'

'

'

'

'

'

'

'

'Commonwealth of Kentucky

Line of credit facility, expiration date

'

'

'

'

'

'

'

'

31-Dec-37

31-Dec-24

31-Dec-18

'

'

Maximum potential undiscounted payments

'

'

'

'

'

'

'

122,000,000

172,000,000

40,000,000

25,000,000

'

'

Percentage of credit agreement agreed to reimburse

'

'

'

'

'

'

'

'

'

'

50.00%

'

'

Guarantee obligation current carrying value

'

'

'

'

'

'

2,000,000

'

'

'

'

'

'

Guarantee obligations maximum exposure per event

'

'

'

'

'

'

'

50,000,000

'

'

'

'

'

Contractual commitments to acquire property, plant and equipment and advance funds to equity method investees

4,200,000,000

'

2,370,000,000

'

'

825,000,000

'

'

'

'

'

'

'

Maximum earnout provision payable to the company

'

'

'

$700,000,000

$700,000,000

'

'

'

'

'

'

'

'

Subsequent_Event_Subsequent_Ev1

Subsequent Event Subsequent Event (Detail) (Subsequent Event, Illinois Extension Pipeline Company LLC, USD $)	1 Months Ended		17 Months Ended
In Millions, unless otherwise specified	Jul. 31, 2014	Jul. 01, 2014	Dec. 31, 2015
			Scenario, Forecast
Subsequent Event [Line Items]	'	'	'
Equity method investments, ownership percentage	'	35.00%	'
Cash paid to acquire equity method investments	$69	'	$226

Supplementary_Statistics_Suppl

Supplementary Statistics - Supplementary Statistics (Detail) (USD $)

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

In Millions, unless otherwise specified

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Mar. 31, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Galveston Bay Refinery and Related Assets

Operating Segments

Operating Segments

Operating Segments

Operating Segments

Operating Segments

Operating Segments

Operating Segments

Operating Segments

Operating Segments

Operating Segments

Operating Segments

Operating Segments

Operating Segments

Operating Segments

Operating Segments

Operating Segments

Corporate and Other

Corporate and Other

Corporate and Other

Corporate and Other

Segment Reconciling Items

Segment Reconciling Items

Segment Reconciling Items

Segment Reconciling Items

Refining & Marketing

Refining & Marketing

Refining & Marketing

Refining & Marketing

Speedway

Speedway

Speedway

Speedway

Pipeline Transportation

Pipeline Transportation

Pipeline Transportation

Pipeline Transportation

Supplementary Statistics [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Income from operations

$1,369

$960

$1,730

$2,116

'

$1,435

[1]

$1,084

[1]

$1,927

[1]

$2,307

[1]

$1,260

$903

$1,622

$2,008

$94

$123

$152

$190

$81

[1]

$58

[1]

$153

[1]

$109

[1]

($61)

[1],[2]

($64)

[1],[2]

($128)

[1],[3]

($131)

[1],[2]

'

'

'

'

Pension settlement expenses

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

-5

[4]

-60

[4]

-69

[4]

-60

[4]

Capital expenditures and investments

363

[5],[6],[7]

283

[5],[6],[7]

734

[5],[6]

1,857

[5],[6]

'

343

[6]

251

[6]

683

[6]

1,797

[6],[8]

235

[6]

134

[6],[8]

413

[6]

1,554

[6],[8]

44

[6]

76

[6]

76

[6]

112

[6]

64

[6]

41

[6],[8]

194

[6]

131

[6],[8]

20

[6],[7]

32

[6],[7]

51

[5],[6]

60

[5],[6]

'

'

'

'

Fair value of contingent consideration as of acquisition date

'

'

'

'

600

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capitalized interest

'

'

'

'

'

'

'

'

'

'

'

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$7

$4

$13

$8

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[1]

Corporate overhead expenses attributable to MPLX are included in the Pipeline Transportation segment. These expenses are not allocated to the Refining & Marketing and Speedway segments.

[2]

Corporate and other unallocated items consists primarily of MPC’s corporate administrative expenses and costs related to certain non-operating assets.

[3]

Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties

[4]

See Note 18.

[5]

The six months ended June 30, 2013 includes the acquisition of the Galveston Bay Refinery and Related Assets, comprised of total consideration, excluding inventory and other current assets, plus assumed liabilities. Total consideration includes the base purchase price and a fair-value estimate of $600 million for the contingent consideration. See Note 4 to the unaudited consolidated financial statements.

[6]

Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.

[7]

Includes capitalized interest $7 million and $4 million for the three months ended June 30, 2014 and 2013, respectively, and $13 million and $8 million for the six months ended June 30, 2014 and 2013, respectively.

[8]

The Refining & Marketing and Pipeline Transportation segments include the acquisition of the Galveston Bay Refinery and Related Assets. See Note 4.

Supplementary_Statistics_Opera

Supplementary Statistics - Operating Statistics (Detail) (USD $)	3 Months Ended				6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
	BPD		BPD		BPD		BPD
Operating Statistics [Line Items ]	'		'		'		'
MPC Consolidated Refined Product Sales Volumes (thousands of barrels per day)	2,153,000	[1],[2]	2,135,000	[1],[2]	2,059,000	[1],[2]	2,016,000	[1],[2]
Refining & Marketing	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refining & Marketing refined product sales volume (thousands of barrels per day)	2,145,000	[2],[3]	2,125,000	[2],[3]	2,048,000	[2],[4]	2,004,000	[2],[4]
Refining & Marketing gross margin (dollars per barrel)	16.02	[2],[5]	13.11	[2],[5]	15.28	[2],[5]	14.14	[2],[5]
Crude oil capacity utilization percent	98.00%	[2],[6]	99.00%	[2],[6]	91.00%	[2],[6]	96.00%	[2],[6]
Refinery throughputs (thousands of barrels per day)	1,832,000	[2],[7]	1,864,000	[2],[7]	1,741,000	[2],[7]	1,768,000	[2],[7]
Sour crude oil throughput percent	54.00%	[2]	52.00%	[2]	52.00%	[2]	53.00%	[2]
WTI-priced crude oil throughput percent	17.00%	[2]	22.00%	[2]	19.00%	[2]	22.00%	[2]
Refined product yields (thousands of barrels per day)	1,865,000	[2],[7]	1,897,000	[2],[7]	1,772,000	[2],[7]	1,801,000	[2],[7]
Inter-refinery transfers	43,000		37,000		51,000		33,000
Refinery direct operating costs (dollars per barrel):	'		'		'		'
Planned turnaround and major maintenance	0.94	[2],[8]	0.73	[2],[8]	1.98	[2],[8]	0.93	[2],[8]
Depreciation and amortization	1.39	[2],[8]	1.28	[2],[8]	1.47	[2],[8]	1.35	[2],[8]
Other manufacturing	4.77	[2],[8],[9]	4.06	[2],[8],[9]	5.32	[2],[8],[9]	3.94	[2],[8],[9]
Total	7.1	[2],[8]	6.07	[2],[8]	8.77		6.22
Refining & Marketing | Crude oil refined	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refinery throughputs (thousands of barrels per day)	1,674,000	[2],[7]	1,690,000	[2],[7]	1,563,000	[2],[7]	1,562,000	[2],[7]
Refining & Marketing | Other charge and blendstocks	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refinery throughputs (thousands of barrels per day)	158,000	[2],[7]	174,000	[2],[7]	178,000	[2],[7]	206,000	[2],[7]
Refining & Marketing | Gasoline	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refined product yields (thousands of barrels per day)	852,000	[2],[7]	923,000	[2],[7]	844,000	[2],[7]	906,000	[2],[7]
Refining & Marketing | Distillates	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refined product yields (thousands of barrels per day)	610,000	[2],[7]	609,000	[2],[7]	562,000	[2],[7]	566,000	[2],[7]
Refining & Marketing | Propane	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refined product yields (thousands of barrels per day)	37,000	[2],[7]	40,000	[2],[7]	36,000	[2],[7]	36,000	[2],[7]
Refining & Marketing | Feedstocks and special products	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refined product yields (thousands of barrels per day)	288,000	[2],[7]	240,000	[2],[7]	255,000	[2],[7]	212,000	[2],[7]
Refining & Marketing | Heavy fuel oil	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refined product yields (thousands of barrels per day)	27,000	[2],[7]	31,000	[2],[7]	28,000	[2],[7]	31,000	[2],[7]
Refining & Marketing | Asphalt	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refined product yields (thousands of barrels per day)	51,000	[2],[7]	54,000	[2],[7]	47,000	[2],[7]	50,000	[2],[7]
Refining & Marketing | Gulf Coast:	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refinery throughputs (thousands of barrels per day)	1,187,000	[10],[2]	1,194,000	[10],[2]	1,129,000	[10],[2]	1,122,000	[10],[2]
Sour crude oil throughput percent	67.00%	[2]	64.00%	[2]	64.00%	[2]	66.00%	[2]
WTI-priced crude oil throughput percent	2.00%	[2]	11.00%	[2]	3.00%	[2]	9.00%	[2]
Refined product yields (thousands of barrels per day)	1,214,000	[10],[2]	1,221,000	[10],[2]	1,155,000	[10],[2]	1,148,000	[10],[2]
Refinery direct operating costs (dollars per barrel):	'		'		'		'
Planned turnaround and major maintenance	0.57	[2],[8]	0.6	[2],[8]	2.11	[2],[8]	0.72	[2],[8]
Depreciation and amortization	1.13	[2],[8]	1	[2],[8]	1.19	[2],[8]	1.06	[2],[8]
Other manufacturing	4.77	[2],[8],[9]	4.01	[2],[8],[9]	5.28	[2],[8],[9]	3.68	[2],[8],[9]
Total	6.47	[2],[8]	5.61	[2],[8]	8.58		5.46
Refining & Marketing | Gulf Coast: | Crude oil refined	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refinery throughputs (thousands of barrels per day)	1,031,000	[10],[2]	1,037,000	[10],[2]	946,000	[10],[2]	938,000	[10],[2]
Refining & Marketing | Gulf Coast: | Other charge and blendstocks	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refinery throughputs (thousands of barrels per day)	156,000	[10],[2]	157,000	[10],[2]	183,000	[10],[2]	184,000	[10],[2]
Refining & Marketing | Gulf Coast: | Gasoline	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refined product yields (thousands of barrels per day)	500,000	[10],[2]	542,000	[10],[2]	494,000	[10],[2]	536,000	[10],[2]
Refining & Marketing | Gulf Coast: | Distillates	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refined product yields (thousands of barrels per day)	390,000	[10],[2]	398,000	[10],[2]	355,000	[10],[2]	360,000	[10],[2]
Refining & Marketing | Gulf Coast: | Propane	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refined product yields (thousands of barrels per day)	25,000	[10],[2]	25,000	[10],[2]	23,000	[10],[2]	22,000	[10],[2]
Refining & Marketing | Gulf Coast: | Feedstocks and special products	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refined product yields (thousands of barrels per day)	270,000	[10],[2]	223,000	[10],[2]	258,000	[10],[2]	201,000	[10],[2]
Refining & Marketing | Gulf Coast: | Heavy fuel oil	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refined product yields (thousands of barrels per day)	16,000	[10],[2]	20,000	[10],[2]	15,000	[10],[2]	19,000	[10],[2]
Refining & Marketing | Gulf Coast: | Asphalt	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refined product yields (thousands of barrels per day)	13,000	[10],[2]	13,000	[10],[2]	10,000	[10],[2]	10,000	[10],[2]
Refining & Marketing | Midwest:	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refinery throughputs (thousands of barrels per day)	688,000	[10]	707,000	[10]	663,000	[10]	679,000	[10]
Sour crude oil throughput percent	34.00%		34.00%		34.00%		35.00%
WTI-priced crude oil throughput percent	40.00%		40.00%		43.00%		42.00%
Refined product yields (thousands of barrels per day)	694,000	[10]	713,000	[10]	668,000	[10]	686,000	[10]
Refinery direct operating costs (dollars per barrel):	'		'		'		'
Planned turnaround and major maintenance	1.53	[8]	0.9	[8]	1.62	[2],[8]	1.22	[2],[8]
Depreciation and amortization	1.75	[8]	1.68	[8]	1.83	[8]	1.75	[8]
Other manufacturing	4.47	[8],[9]	3.96	[8],[9]	4.97	[2],[8],[9]	4.2	[2],[8],[9]
Total	7.75	[8]	6.54	[8]	8.42		7.17
Refining & Marketing | Midwest: | Crude oil refined	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refinery throughputs (thousands of barrels per day)	643,000	[10]	653,000	[10]	617,000	[10]	624,000	[10]
Refining & Marketing | Midwest: | Other charge and blendstocks	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refinery throughputs (thousands of barrels per day)	45,000	[10]	54,000	[10]	46,000	[10]	55,000	[10]
Refining & Marketing | Midwest: | Gasoline	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refined product yields (thousands of barrels per day)	352,000	[10]	383,000	[10]	350,000	[10]	371,000	[10]
Refining & Marketing | Midwest: | Distillates	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refined product yields (thousands of barrels per day)	220,000	[10]	211,000	[10]	207,000	[10]	206,000	[10]
Refining & Marketing | Midwest: | Propane	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refined product yields (thousands of barrels per day)	13,000	[10]	15,000	[10]	14,000	[10]	14,000	[10]
Refining & Marketing | Midwest: | Feedstocks and special products	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refined product yields (thousands of barrels per day)	60,000	[10]	52,000	[10]	47,000	[10]	43,000	[10]
Refining & Marketing | Midwest: | Heavy fuel oil	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refined product yields (thousands of barrels per day)	11,000	[10]	11,000	[10]	13,000	[10]	12,000	[10]
Refining & Marketing | Midwest: | Asphalt	'		'		'		'
Refining & Marketing Operating Statistics	'		'		'		'
Refined product yields (thousands of barrels per day)	38,000	[10]	41,000	[10]	37,000	[10]	40,000	[10]
Speedway	'		'		'		'
Speedway Operating Statistics	'		'		'		'
Convenience stores at period-end	1,492		1,468		1,492		1,468
Gasoline and distillate sales (millions of gallons)	806,000,000		781,000,000		1,579,000,000		1,526,000,000
Gasoline and distillate gross margin (dollars per gallon)	0.1282	[11]	0.1738	[11]	0.122	[11]	0.1525	[11]
Merchandise sales (in millions)	830		806		1,552		1,517
Merchandise gross margin (in millions)	224		212		416		396
Merchandise margin percent	27.10%		26.30%		26.80%		26.10%
Same store gasoline sales volume (period over period) percentage	-1.50%		0.00%		-1.10%		0.30%
Merchandise sales excluding cigarettes (period over period) percentage	4.60%	[12]	4.50%	[12]	4.90%	[12]	2.80%	[12]
Pipeline Transportation	'		'		'		'
Pipeline Transportation Operating Statistics	'		'		'		'
Pipeline throughputs (thousands of barrels per day)	2,152,000	[13]	2,293,000	[13]	2,058,000	[13]	2,242,000	[13]
Pipeline Transportation | Crude oil pipelines	'		'		'		'
Pipeline Transportation Operating Statistics	'		'		'		'
Pipeline throughputs (thousands of barrels per day)	1,281,000	[13]	1,334,000	[13]	1,213,000	[13]	1,303,000	[13]
Pipeline Transportation | Refined products pipelines	'		'		'		'
Pipeline Transportation Operating Statistics	'		'		'		'
Pipeline throughputs (thousands of barrels per day)	871,000	[13]	959,000	[13]	845,000	[13]	939,000	[13]
[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]	The six months ended June 30, 2013 includes the acquisition of the Galveston Bay Refinery and Related Assets, comprised of total consideration, excluding inventory and other current assets, plus assumed liabilities. Total consideration includes the base purchase price and a fair-value estimate of $600 million for the contingent consideration. See Note 4 to the unaudited consolidated financial statements.
[5]	Sales revenue less cost of refinery inputs and purchased products, divided by total refinery throughputs.
[6]	Based on calendar day capacity, which is an annual average that includes downtime for planned maintenance and other normal operating activities.
[7]	Excludes inter-refinery volumes of 43 mbpd and 37 mbpd for the three months ended June 30, 2014 and 2013, respectively, and 51 mbpd and 33 mbpd for the six months ended June 30, 2014 and 2013, respectively.
[8]	Per barrel of total refinery throughputs.
[9]	Includes utilities, labor, routine maintenance and other operating costs.
[10]	Includes inter-refinery transfer volumes.
[11]	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.
[12]	Excludes cigarettes.
[13]	On owned common-carrier pipelines, excluding equity method investments.