Marathon Petroleum (MPC) 10-K 27 Feb 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Billions, except Share data, unless otherwise specified	Dec. 31, 2014	Feb. 13, 2015	Jun. 30, 2014
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	FALSE
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus (Q1,Q2,Q3,FY)	FY
Trading Symbol	MPC
Entity Registrant Name	Marathon Petroleum Corp
Entity Central Index Key	1510295
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		273,062,880
Entity Public Float			$22.20

Consolidated_Statements_of_Inc

Consolidated Statements of Income (USD $)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues and other income:
Sales and other operating revenues (including consumer excise taxes)	$97,817	$100,160	$82,243
Income from equity method investments	153	36	26
Net gain on disposal of assets	21	6	177
Other income	111	52	46
Total revenues and other income	98,102	100,254	82,492
Costs and expenses:
Cost of revenues (excludes items below)	83,770	87,401	68,668
Purchases from related parties	505	357	280
Consumer excise taxes	6,685	6,263	5,709
Depreciation and amortization	1,326	1,220	995
Selling, general and administrative expenses	1,375	1,248	1,223
Other taxes	390	340	270
Total costs and expenses	94,051	96,829	77,145
Income from operations	4,051	3,425	5,347
Net interest and other financial income (costs)	-216	-179	-109
Income before income taxes	3,835	3,246	5,238
Provision for income taxes	1,280	1,113	1,845
Net income	2,555	2,133	3,393
Less net income attributable to noncontrolling interests	31	21	4
Net income attributable to MPC	$2,524	$2,112	$3,389
Basic:
Net income attributable to MPC per share	$8.84	$6.69	$9.95
Weighted average shares outstanding (in shares)	285	315	340
Diluted:
Net income attributable to MPC per share	$8.78	$6.64	$9.89
Weighted average shares outstanding (in shares)	287	317	342
Dividends paid (in USD per share)	$1.84	$1.54	$1.20

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income	$2,555	$2,133	$3,393
Defined benefit postretirement and post-employment plans:
Actuarial changes, net of tax of ($47), $174 and $47	-78	294	78
Prior service costs, net of tax of ($19), ($19) and $203	-31	-34	337
Other comprehensive income (loss)	-109	260	415
Comprehensive income	2,446	2,393	3,808
Less comprehensive income attributable to noncontrolling interests	31	21	4
Comprehensive income attributable to MPC	$2,415	$2,372	$3,804

Consolidated_Statements_of_Com1

Consolidated Statements of Comprehensive Income (Parenthetical) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Actuarial changes, tax	($47)	$174	$47
Prior service costs, tax	($19)	($19)	$203

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Current assets:
Cash and cash equivalents	$1,494	$2,292
Receivables, less allowance for doubtful accounts of $13 and $9	4,058	5,559
Inventories	5,642	4,689
Other current assets	145	197
Total current assets	11,339	12,737
Equity method investments	865	463
Property, plant and equipment, net	16,261	13,921
Goodwill	1,566	938
Other noncurrent assets	429	326
Total assets	30,460	28,385
Current liabilities:
Accounts payable	6,661	8,234
Payroll and benefits payable	427	406
Consumer excise taxes payable	463	373
Accrued taxes	647	513
Long-term debt due within one year	27	23
Other current liabilities	354	275
Total current liabilities	8,579	9,824
Long-term debt	6,610	3,373
Deferred income taxes	2,014	2,304
Defined benefit postretirement plan obligations	1,099	771
Deferred credits and other liabilities	768	781
Total liabilities	19,070	17,053
Commitments and contingencies (see Note 26)
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 – 89 million and 65 million shares	-6,299	-4,155
Additional paid-in capital	9,844	9,768
Retained earnings	7,515	5,507
Accumulated other comprehensive loss	-313	-204
Total MPC stockholders’ equity	10,751	10,920
Noncontrolling interests	639	412
Total equity	11,390	11,332
Total liabilities and equity	$30,460	$28,385

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, except Share data, unless otherwise specified
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$13	$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	-89,000,000	-65,000,000

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities:
Net income	$2,555	$2,133	$3,393
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,326	1,220	995
Pension and other postretirement benefits, net	151	-124	153
Deferred income taxes	-242	23	492
Net gain on disposal of assets	-21	-6	-177
Equity method investments, net	17	-18	11
Changes in the fair value of derivative instruments	-3	-21	59
Changes in:
Current receivables	1,642	-940	851
Inventories	-786	-305	-115
Current accounts payable and accrued liabilities	-1,547	1,464	-1,223
All other, net	18	-21	53
Net cash provided by operating activities	3,110	3,405	4,492
Investing activities:
Additions to property, plant and equipment	-1,480	-1,206	-1,369
Acquisitions, net of cash acquired	-2,821	-1,515	-190
Disposal of assets	27	16	53
Investments – acquisitions, loans and contributions	-413	-151	-57
Investments—redemptions, repayments and return of capital	9	77	108
All other, net	135	23	3
Net cash used in investing activities	-4,543	-2,756	-1,452
Financing activities:
Long-term debt – borrowings	3,793	0	0
Long-term debt – repayments	-548	-21	-17
Debt issuance costs	-22	-4	-6
Issuance of common stock	26	48	108
Common stock repurchased	-2,131	-2,793	-1,350
Dividends paid	-524	-484	-407
Net proceeds from issuance of MPLX LP common units	221	0	407
Distributions to noncontrolling interests	-27	-21	0
Tax settlement with Marathon Oil Corporation	0	39	0
Contingent consideration payment	-172	0	0
All other, net	19	19	6
Net cash provided by (used in) financing activities	635	-3,217	-1,259
Net increase (decrease) in cash and cash equivalents	-798	-2,568	1,781
Cash and cash equivalents at beginning of period	2,292	4,860	3,079
Cash and cash equivalents at end of period	$1,494	$2,292	$4,860

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, 2011	$9,505	$4	$0	$9,482	$898	($879)	$0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	3,393				3,389		4
Dividends declared	-407				-407
Other comprehensive income (loss)	415					415
Shares repurchased	-1,350		-1,250	-100
Shares returned - stock based compensation			-3
Shares issued - stock based compensation				108
Shares issued (returned) – stock-based compensation	105
Stock-based compensation	46			46			0
Issuance of MPLX LP common units	407						407
Other	-9			-9
Ending balance at Dec. 31, 2012	12,105	4	-1,253	9,527	3,880	-464	411
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,133				2,112		21
Dividends declared	-485				-485
Distributions to noncontrolling interests	-21						-21
Other comprehensive income (loss)	260					260
Shares repurchased	-2,793		-2,893	100
Shares returned - stock based compensation			-9
Shares issued - stock based compensation				47
Shares issued (returned) – stock-based compensation	38
Stock-based compensation	56			55			1
Tax settlement with Marathon Oil Corporation	39			39
Ending balance at Dec. 31, 2013	11,332	4	-4,155	9,768	5,507	-204	412
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,555				2,524		31
Dividends declared	-525				-525
Distributions to noncontrolling interests	-27						-27
Other comprehensive income (loss)	-109					-109
Shares repurchased	-2,131		-2,131	0
Shares returned - stock based compensation			-13
Shares issued - stock based compensation				26
Shares issued (returned) – stock-based compensation	13
Stock-based compensation	52			50			2
Issuance of MPLX LP common units	221						221
Other	9				9
Ending balance at Dec. 31, 2014	$11,390	$4	($6,299)	$9,844	$7,515	($313)	$639

Consolidated_Statements_of_Equ1

Consolidated Statements of Equity - Shares	Total		Common Stock	Treasury Stock
Number of shares held in treasury (beginning balance) at Dec. 31, 2011				0
Number of shares issued (beginning balance) at Dec. 31, 2011			357,000,000
Number of shares issued - stock-based compensation			4,000,000
Number of shares repurchased	-28,000,000			-28,000,000
Number of shares held in treasury (ending balance) at Dec. 31, 2012				-28,000,000
Number of shares issued (ending balance) at Dec. 31, 2012			361,000,000
Number of shares issued - stock-based compensation			1,000,000
Number of shares repurchased	-37,000,000	[1]		-37,000,000
Number of shares held in treasury (ending balance) at Dec. 31, 2013	-65,000,000			-65,000,000
Number of shares issued (ending balance) at Dec. 31, 2013	362,000,000		362,000,000
Number of shares issued - stock-based compensation			1,000,000
Number of shares repurchased	-24,000,000			-24,000,000
Number of shares held in treasury (ending balance) at Dec. 31, 2014	-89,000,000			-89,000,000
Number of shares issued (ending balance) at Dec. 31, 2014	363,000,000		363,000,000
[1]	Shares repurchased in 2013 includes 1 million shares received under the November 2012 ASR program, which were paid for in 2012.

Description_Of_The_Business_An

Description Of The Business And Basis Of Presentation	12 Months Ended
	Dec. 31, 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 and pipeline transportation operations conducted primarily in the Midwest, Gulf Coast, East Coast and Southeast regions of the United States, through subsidiaries, including Marathon Petroleum Company LP, Speedway LLC and its subsidiaries (“Speedway”) and MPLX LP and its subsidiaries (“MPLX”).
	See Note 11 for additional information about our operations.
	Spinoff – On May 25, 2011, the Marathon Oil board of directors approved the spinoff of its Refining, Marketing & Transportation Business (“RM&T Business”) into an independent, publicly traded company, MPC, through the distribution of MPC common stock to the stockholders of Marathon Oil common stock (the “Spinoff”). MPC became an independent, publicly traded company on July 1, 2011.
	Basis of Presentation – Our results of operations and cash flows consist of consolidated MPC activities. All significant intercompany transactions and accounts have been eliminated.
	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 year ended December 31, 2014 and for the year ended December 31, 2013 was immaterial.

Summary_Of_Principal_Accountin

Summary Of Principal Accounting Policies	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Summary Of Principal Accounting Policies	Summary of Principal Accounting Policies
	Principles applied in consolidation – These consolidated financial statements include the accounts of our majority-owned, controlled subsidiaries. We consolidate MPLX, in which we own a 71.5 percent controlling financial interest, and we record a noncontrolling interest for the 28.5 percent interest owned by the public.
	Investments in entities over which we have significant influence, but not control, are accounted for using the equity method of accounting. This includes entities in which we hold majority ownership but the minority shareholders have substantive participating rights in the investee. Income from equity method investments represents our proportionate share of net income generated by the equity method investees.
	Equity method investments are generally carried at our share of net assets plus loans and advances. Such investments are assessed for impairment whenever changes in the facts and circumstances indicate a loss in value has occurred, if the loss is deemed to be other than temporary. When the loss is deemed to be other than temporary, the carrying value of the equity method investment is written down to fair value, and the amount of the write-down is included in net income. Differences in the basis of the investments and the separate net asset values of the investees, if any, are amortized into net income over the remaining useful lives of the underlying assets and liabilities, except for the excess related to goodwill.
	Use of estimates – The preparation of financial statements in accordance with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities as of the date of the consolidated financial statements and the reported amounts of revenues and expenses during the respective reporting periods.
	Revenue recognition – Revenues are recognized when products are shipped or services are provided to customers, title is transferred, the sales price is fixed or determinable and collectability is reasonably assured. Costs associated with revenues are recorded in cost of revenues. Shipping and other transportation costs billed to our customers are presented on a gross basis in revenues and cost of revenues.
	Rebates from vendors are recognized as a reduction of cost of revenues when the initiating transaction occurs. Incentives that are derived from contractual provisions are accrued based on past experience and recognized in cost of revenues. Rebates to customers are reflected as a reduction of revenue and are accrued for in accounts payable on the consolidated balance sheets.
	Crude oil and refined product exchanges and matching buy/sell transactions – We enter into exchange contracts and matching buy/sell arrangements whereby we agree to deliver a particular quantity and quality of crude oil or refined products at a specified location and date to a particular counterparty and to receive from the same counterparty the same commodity at a specified location on the same or another specified date. The exchange receipts and deliveries are nonmonetary transactions, with the exception of associated grade or location differentials that are settled in cash. The matching buy/sell purchase and sale transactions are settled in cash. Both exchange and matching buy/sell transactions are accounted for as exchanges of inventory and no revenues are recorded. The exchange transactions are recognized at the carrying amount of the inventory transferred.
	Consumer excise taxes – We are required by various governmental authorities, including countries, states and municipalities, to collect and remit taxes on certain consumer products. Such taxes are presented on a gross basis in revenues and costs and expenses in the consolidated statements of income.
	Cash and cash equivalents – Cash and cash equivalents include cash on hand and on deposit and investments in highly liquid debt instruments with maturities of three months or less.
	Restricted cash – Restricted cash consists of cash advances to be used for the operation and maintenance of an operated pipeline system. At December 31, 2014 and 2013, the amount of restricted cash included in other current assets on the consolidated balance sheets were $4 million and $7 million, respectively.
	Accounts receivable and allowance for doubtful accounts – Our receivables primarily consist of customer accounts receivable. The allowance for doubtful accounts is the best estimate of the amount of probable credit losses in customer accounts receivable and is based on historical write-off experience. We review the allowance quarterly and past-due balances over 180 days are reviewed individually for collectability. All other customer receivables are recorded at the invoiced amounts and generally do not bear interest. Account balances for these customer receivables are generally charged directly to bad debt expense when it becomes probable the receivable will not be collected.
	Approximately 41 percent and 38 percent of our accounts receivable balances at December 31, 2014 and 2013, respectively, are related to sales of crude oil or refinery feedstocks to customers with whom we have master netting agreements. We have master netting agreements with more than 100 companies engaged in the crude oil or refinery feedstock trading and supply business or the petroleum refining industry. A master netting agreement generally provides for a once per month net cash settlement of the accounts receivable from and the accounts payable to a particular counterparty.
	Inventories – Inventories are carried at the lower of cost or market value. Cost of inventories is determined primarily under the last-in, first-out (“LIFO”) method. Costs for crude oil and refined product inventories are aggregated on a consolidated basis for purposes of assessing if the LIFO cost basis of these inventories may have to be written down to market value.
	Derivative instruments – We use derivatives to economically hedge a portion of our exposure to commodity price risk and, historically, to interest rate risk. We also have limited authority to use selective derivative instruments that assume market risk. All derivative instruments are recorded at fair value. Commodity derivatives are reflected on the consolidated balance sheets on a net basis by futures commission merchant, as they are governed by master netting agreements. Cash flows related to derivatives used to hedge commodity price risk and interest rate risk are classified in operating activities with the underlying transactions.
	Fair value accounting hedges – We used interest rate swaps to hedge our exposure to interest rate risk associated with fixed interest rate debt in our portfolio. Changes in the fair values of both the hedged item and the related derivative were recognized immediately in net income with an offsetting effect included in the basis of the hedged item. The net effect was to report in net income the extent to which the accounting hedge was not effective in achieving offsetting changes in fair value. We terminated our interest rate swap agreements during 2012. There was a gain on the termination of the agreements, which has been accounted for as an adjustment to our long-term debt balance. The gain is being amortized over the remaining life of the associated debt, which reduces our interest expense.
	Derivatives not designated as accounting hedges –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. Changes in the fair value of derivatives not designated as accounting hedges are recognized immediately in net income.
	Concentrations of credit risk – All of our financial instruments, including derivatives, involve elements of credit and market risk. The most significant portion of our credit risk relates to nonperformance by counterparties. The counterparties to our financial instruments consist primarily of major financial institutions and companies within the energy industry. To manage counterparty risk associated with financial instruments, we select and monitor counterparties based on an assessment of their financial strength and on credit ratings, if available. Additionally, we limit the level of exposure with any single counterparty.
	Property, plant and equipment – Property, plant and equipment are recorded at cost and depreciated on a straight-line basis over the estimated useful lives of the assets, which range from four to 42 years. Such assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. If the sum of the expected undiscounted future cash flows from the use of the asset and its eventual disposition is less than the carrying amount of the asset, an impairment loss is recognized based on the fair value of the asset.
	When items of property, plant and equipment are sold or otherwise disposed of, any gains or losses are reported in net income. Gains on the disposal of property, plant and equipment are recognized when earned, which is generally at the time of closing. If a loss on disposal is expected, such losses are recognized when the assets are classified as held for sale.
	Interest expense is capitalized for qualifying assets under construction. Capitalized interest costs are included in property, plant and equipment and are depreciated over the useful life of the related asset.
	Goodwill – Goodwill represents the excess of the purchase price over the estimated fair value of the net assets acquired in the acquisition of a business. Goodwill is not amortized, but rather is tested for impairment annually and when events or changes in circumstances indicate that the fair value of a reporting unit with goodwill has been reduced below carrying value. The impairment test requires allocating goodwill and other assets and liabilities to reporting units. The fair value of each reporting unit is determined and compared to the book value of the reporting unit. If the fair value of the reporting unit is less than the book value, including goodwill, the implied fair value of goodwill is calculated. The excess, if any, of the book value over the implied fair value of goodwill is charged to net income.
	Major maintenance activities – Costs for planned turnaround, major maintenance and engineered project activities are expensed in the period incurred. These types of costs include contractor repair services, materials and supplies, equipment rentals and our labor costs.
	Environmental costs – Environmental expenditures are capitalized if the costs mitigate or prevent future contamination or if the costs improve environmental safety or efficiency of the existing assets. We recognize remediation costs and penalties when the responsibility to remediate is probable and the amount of associated costs can be reasonably estimated. The timing of remediation accruals coincides with completion of a feasibility study or the commitment to a formal plan of action. Remediation liabilities are accrued based on estimates of known environmental exposure and are discounted when the estimated amounts are reasonably fixed and determinable. If recoveries of remediation costs from third parties are probable, a receivable is recorded and is discounted when the estimated amount is reasonably fixed and determinable.
	Asset retirement obligations – The fair value of asset retirement obligations is recognized in the period in which the obligations are incurred if a reasonable estimate of fair value can be made. Conditional asset retirement obligations for removal and disposal of fire-retardant material from certain refining facilities have been recognized. The fair values recorded for such obligations are based on the most probable current cost projections. The recorded asset retirement obligations are not material to the consolidated financial statements.
	Asset retirement obligations have not been recognized for some assets because the fair value cannot be reasonably estimated since the settlement dates of the obligations are indeterminate. Such obligations will be recognized in the period when sufficient information becomes available to estimate a range of potential settlement dates. The asset retirement obligations principally include the removal of underground storage tanks at our leased convenience stores at or near the time of closure and hazardous material disposal and removal or dismantlement requirements associated with the closure of certain refining, terminal and pipeline assets.
	Our practice is to keep our assets in good operating condition through routine repair and maintenance of component parts in the ordinary course of business and by continuing to make improvements based on technological advances. As a result, we believe that these assets have no expected settlement date for purposes of estimating asset retirement obligations since the dates or ranges of dates upon which we would retire these assets cannot be reasonably estimated at this time.
	Income taxes – Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between the financial statement carrying amounts of assets and liabilities and their tax bases. Deferred tax assets are recorded when it is more likely than not that they will be realized. The realization of deferred tax assets is assessed periodically based on several factors, primarily our expectation to generate sufficient future taxable income.
	Stock-based compensation arrangements – The fair value of stock options granted to our employees is estimated on the date of grant using the Black-Scholes option pricing model. The model employs various assumptions, based on management’s estimates at the time of grant, which impact the calculation of fair value and ultimately, the amount of expense that is recognized over the vesting period of the stock option award. Of the required assumptions, the expected life of the stock option award and the expected volatility of our stock price have the most significant impact on the fair value calculation. The average expected life is based on our historical employee exercise behavior. The assumption for expected volatility of our stock price reflects a weighting of 50 percent of our common stock implied volatility and 50 percent of MPC’s common stock historical volatility.
	The fair value of restricted stock awards granted to our employees is determined based on the fair market value of our common stock on the date of grant. The fair value of performance unit awards granted to our employees is estimated on the date of grant using a Monte Carlo valuation model.
	Our stock-based compensation expense is recognized based on management’s estimate of the awards that are expected to vest, using the straight-line attribution method for all service-based awards with a graded vesting feature. If actual forfeiture results are different than expected, adjustments to recognized compensation expense may be required in future periods. Unearned stock-based compensation is charged to equity when restricted stock awards are granted. Compensation expense is recognized over the vesting period and is adjusted if conditions of the restricted stock award are not met.
	Renewable fuel identification numbers (“RINs”) – We purchase RINs to satisfy a portion of our Renewable Fuel Standard (“RFS2”) compliance. We record a short-term intangible asset, included in other current assets on the balance sheet, for RINs owned in excess of our anticipated current period compliance requirements. The asset value is based on the product of the excess RINs as of the balance sheet date, if any, and the average cost of our RINs. We record a current liability, included in other current liabilities on the balance sheet, when we are deficient RINs based on the product of the deficient RINs as of the balance sheet date, if any, and the market price of the RINs at the balance sheet date. The cost of RINs used for compliance is reflected in cost of revenues. Any gains or losses on the sale or expiration of RINs are classified as other income.

Accounting_Standards

Accounting Standards	12 Months Ended
	Dec. 31, 2014
Accounting Changes and Error Corrections [Abstract]
Accounting Standards	Accounting Standards
	Not Yet Adopted
	In February 2015, the Financial Accounting Standards Board (“FASB”) issued an accounting standards update making targeted changes to the current consolidation guidance. The new standard changes the way certain decisions are made related to substantive rights, related parties, and decision making fees when applying the VIE consolidation model and eliminates certain guidance for limited partnerships and similar entities under the voting interest consolidation model. The update is effective for annual periods beginning after December 15, 2015. Early adoption is permitted. At this point, we have not determined the impact of the new standards update on our consolidated financial statements and related disclosures.
	In August 2014, the FASB issued an accounting standards update requiring management to assess an entity’s ability to continue as a going concern and to provide related footnote disclosures in certain circumstances. Management will be required to assess if there is substantial doubt about an entity’s ability to continue as a going concern within one year after the date that the financial statements are issued. Disclosures will be required if conditions give rise to substantial doubt and the type of disclosure will be determined based on whether management’s plans will be able to alleviate the substantial doubt. The accounting standards update will be effective for the first annual period ending after December 15, 2016, and for annual periods and interim periods thereafter with early application permitted.
	In June 2014, the 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, we have not determined the impact of the new standard on our consolidated financial statements.
	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 (or components) of an entity or the classification of a component (or components) 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	12 Months Ended
	Dec. 31, 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. In October 2012, MPLX completed its initial public offering of 19.9 million common units. Net proceeds to MPLX from the sale of the units were $407 million.
	As of December 31, 2014, we owned a 71.5 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 of cash on-hand.
	On March 1, 2014, we sold MPLX a 13 percent interest in Pipe Line Holdings for $310 million. MPLX financed this transaction with $40 million of cash on-hand and $270 million of borrowings on its bank revolving credit agreement.
	On December 1, 2014, we sold and contributed interests in Pipe Line Holdings totaling 30.5 percent to MPLX for $600 million in cash and 2.9 million MPLX common units valued at $200 million. MPLX financed the sales portion of this transaction with $600 million of borrowings on its bank revolving credit facility.
	The sales and contribution of our interests in Pipe Line Holdings to MPLX resulted in a change of our ownership in Pipe Line Holdings, but not a change in control. We accounted for these sales as transactions between entities under common control and did not record a gain or loss.
	On December 8, 2014, MPLX completed a public offering of 3.5 million common units at a price to the public of $66.68 per common unit, with net proceeds of $221 million. MPLX used the net proceeds from this offering to repay borrowings under its bank revolving credit facility and for general partnership purposes. On December 10, 2014, we exercised our right to maintain our two percent general partner interest in MPLX by purchasing 130 thousand general partner units for $9 million.
	Agreements
	MPLX generates revenue primarily by charging tariffs for transporting crude oil, refined products and other hydrocarbon-based products through their pipelines and at their barge dock and fees for storing crude oil and products at their storage facilities. They are also the operator of additional crude oil and product pipelines owned by us and third parties for which they are paid operating fees. They do not take ownership of the crude oil or products that they transport and store for their customers, and they do not engage in the trading of any commodities.
	We have various long-term, fee-based transportation and storage services agreements with MPLX. Under these agreements, MPLX provides transportation and storage services to us, and we commit to provide MPLX with minimum quarterly throughput volumes on crude oil and products systems and minimum storage volumes of crude oil, products and butane. We also have agreements with MPLX which establish fees for operational and management services provided between us and MPLX and for executive management services and certain general and administrative services provided by us to MPLX. These transactions are eliminated in consolidation.

Acquisitions_and_Investments

Acquisitions and Investments	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
Acquisitions and Investments	Acquisitions and Investments
	Acquisition of Hess’ Retail Operations and Related Assets
	On September 30, 2014, we acquired from Hess Corporation (“Hess”) all of Hess’ retail locations, transport operations and shipper history on various pipelines, including approximately 40,000 barrels per day on Colonial Pipeline, for $2.82 billion. We refer to these assets as “Hess’ Retail Operations and Related Assets.” The transaction was funded with a combination of debt and available cash.
	The transaction provides for an adjustment for working capital, which has not been finalized with Hess. If a change is made for working capital, the fair value of the assets acquired and liabilities assumed will be revised.
	The components of the fair value of consideration transferred are as follows:
	(In millions)
	Cash	$	2,824
	Net working capital adjustment estimate	(3		)
	Total fair value of consideration transferred	$	2,821
	During the fourth quarter of 2014, an independent appraisal of the assets acquired and liabilities assumed and other evaluations were completed and finalized. Updates to the preliminary fair value measurements of assets acquired and liabilities assumed were made during the fourth quarter of 2014. The following table summarizes the amounts assigned to the assets acquired and liabilities assumed as of the acquisition date.
	(In millions)
	Cash and cash equivalents	$	49
	Receivables	123
	Inventories	165
	Other current assets	8
	Property, plant and equipment, net	2,063
	Other noncurrent assets	111
	Total assets acquired	2,519
	Accounts payable	77
	Payroll and benefits payable	15
	Consumer excise taxes payable	64
	Accrued taxes	4
	Other current liabilities	10
	Defined benefit postretirement plan obligations	2
	Deferred credits and other liabilities	155
	Total liabilities assumed	327
	Net assets acquired excluding goodwill	2,192
	Goodwill	629
	Net assets acquired	$	2,821
	The purchase price allocation resulted in the recognition of $629 million in goodwill by our Speedway segment, which is deductible for tax purposes. Goodwill recognized for the acquisition primarily relates to the expected benefits of a significantly expanded retail platform that should enable growth in new markets, as well as the potential for higher merchandise sales at the acquired locations. We also expect strategic benefits from the financial and operational scale we expect to realize across our entire retail network. This acquisition significantly expands our Speedway presence from nine to 22 states throughout the East Coast and Southeast and is aligned with our strategy to grow higher-valued, stable cash flow businesses. This acquisition also enables 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.
	Other noncurrent assets includes a $22 million intangible asset related to a trade name and $72 million related to favorable lease contract terms. Deferred credits and other liabilities includes $90 million related to unfavorable lease contract terms. The trade name is being amortized over its estimated useful life of two years based on the utilization of the assets. The favorable and unfavorable lease contract amounts are being amortized over the terms of the leases.
	We recognized $14 million of acquisition-related costs associated with Hess’ Retail Operations and Related Assets acquisition. These costs were expensed and were included in selling, general and administrative expenses.
	The amounts of revenue and income from operations associated with Hess’ Retail Operations and Related Assets included in our consolidated statements of income for 2014 are as follows:
	(In millions)	2014
	Sales and other operating revenues (including consumer excise taxes)	$	2,403
	Income from operations	113
	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 the 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. During 2014, we paid BP $180 million for the first period’s contingent earnout. On the consolidated statements of cash flows, $172 million of the contingent earnout payment is included as a financing activity with the remainder included as an operating activity. See Note 18 for additional information on the contingent consideration.
	The transaction provided for a post-closing adjustment for inventory, which was finalized for $9 million, reducing our total consideration.
	The components of the fair value of consideration transferred are as follows:
	(In millions)
	Cash	$	1,491
	Fair value of contingent consideration as of acquisition date	600
	Payable to seller	6
	Post-closing adjustment	(9		)
	Total fair value of consideration transferred	$	2,088
	During the fourth quarter of 2013, an independent appraisal of the assets acquired and liabilities assumed and other evaluations were completed and finalized. The following table summarizes the final amounts assigned to the assets acquired and liabilities assumed as of the acquisition date.
	(In millions)
	Inventories	$	935
	Other current assets	1
	Property, plant and equipment, net	1,274
	Other noncurrent assets	88
	Total assets acquired	2,298
	Accounts payable	12
	Payroll and benefits payable	14
	Long-term debt due within one year(a)	2
	Other current liabilities	6
	Long-term debt(a)	58
	Defined benefit postretirement plan obligations	43
	Deferred credits and other liabilities	75
	Total liabilities assumed	210
	Net assets acquired	$	2,088
	(a)	Represents a capital lease obligation assumed.
	Neither goodwill nor a gain from a bargain purchase was recognized in conjunction with the Galveston Bay Refinery and Related Assets acquisition.
Other noncurrent assets consist of a $20 million intangible asset related to customer relationships and a $68 million intangible asset related to prepaid licensed refinery technology agreements. The intangible assets related to customer relationships and prepaid licensed refinery technology agreements are being amortized on a straight-line basis over four and 15 years, respectively. The weighted average life over which these acquired intangibles are being amortized is approximately 13 years.
We recognized $7 million of acquisition-related costs associated with the Galveston Bay Refinery and Related Assets acquisition. These costs were expensed and were included in selling, general and administrative expenses.
Our refineries and related assets are operated as an integrated system. As the information is not available by refinery, it is not practicable to disclose the revenues and net income associated with the acquisition that were included in our consolidated statements of income for 2013.
Unaudited Pro Forma Financial Information
The following unaudited pro forma financial information presents consolidated results assuming Hess’ Retail Operations and Related Assets acquisition occurred on January 1, 2013 and 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 acquisitions and is not necessarily indicative of the results of future operations.
(In millions, except per share data)	2014			2013
Sales and other operating revenues (including consumer excise taxes)	$	106,482		$	114,148
Net income attributable to MPC	2,547			2,142
Net income attributable to MPC per share – basic	$	8.94		$	6.8
Net income attributable to MPC per share – diluted	8.87			6.76
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, additional interest expense related to financing the acquisition of Hess’ Retail Operations and Related Assets, as well as the related income tax effects.
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.
In July 2012, Speedway acquired 10 convenience stores located in the northern Kentucky and southwestern Ohio regions from Road Ranger LLC in exchange for cash and a truck stop location in the Chicago metropolitan area. In connection with this acquisition, our Speedway segment recorded $5 million of goodwill.
In May 2012, Speedway acquired 87 convenience stores situated throughout Indiana and Ohio from GasAmerica Services, Inc., along with the associated inventory, intangible assets and two parcels of undeveloped real estate. In connection with this acquisition, our Speedway segment recorded $83 million of goodwill.
The goodwill associated with these acquisitions is deductible for income tax purposes.
These acquisitions support our strategic initiative to increase our Speedway segment sales and profitablity. 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 production 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 in 2013 and 2012 and the biodiesel facility in 2014 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 (“TAEI”), 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.
Investment in Pipeline Companies
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 2014, we made contributions of $120 million to Illinois Extension Pipeline to fund our portion of the construction costs incurred-to-date on the SAX project. We account for our ownership interest in Illinois Extension Pipeline as an equity method investment. See Note 26 for information on future contributions to Illinois Extension 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.
In November 2013, we agreed to serve as an anchor shipper for the Sandpiper pipeline project and fund 37.5 percent of the construction costs of the project, which will become part of Enbridge Energy Partners L.P.’s (“Enbridge Energy Partners”) North Dakota System. In exchange for these commitments, we will earn an approximate 27 percent equity interest in Enbridge Energy Partners’ North Dakota System when the Sandpiper pipeline is placed into service, which is expected to be in 2017. We also have the option to increase our ownership interest to approximately 30 percent through additional investments in future system improvements. We made contributions of $192 million to North Dakota Pipeline Company LLC (“North Dakota Pipeline”) during 2014. We have contributed $216 million since project inception. We account for our interest in North Dakota Pipeline using the equity method of accounting. See Note 26 for information on future contributions to North Dakota Pipeline.

Disposition

Disposition	12 Months Ended
	Dec. 31, 2014
Discontinued Operations and Disposal Groups [Abstract]
Disposition	Disposition
	On December 1, 2010, we completed the sale of most of our Minnesota assets. These assets included the 74,000 barrel per calendar day St. Paul Park refinery and associated terminals, 166 convenience stores primarily branded SuperAmerica® (including six stores in Wisconsin), along with the SuperMom’s bakery (a baked goods and sandwich supply operation) and certain associated trademarks, SuperAmerica Franchising LLC, interests in pipeline assets in Minnesota and associated inventories. We refer to these assets as the “Minnesota Assets.”
	In July 2012, the buyer of our Minnesota Assets successfully completed an initial public offering (“IPO”). The successful completion of this IPO triggered the provisions in our May 4, 2012 settlement agreement with the buyer to be effective. Under the settlement agreement, we were released from our obligation to pay margin support and the buyer was released from its obligation to pay us under the earnout provision contained in the original sales agreement. Also, the buyer redeemed our $80 million preferred equity interest, paid us $12 million for dividends accrued on our preferred equity interest and paid us $40 million of cash, for total cash receipts of $132 million. In addition, the buyer issued us a new preferred security valued at $45 million. As a result, we recognized income before income taxes of approximately $183 million during 2012, which included $86 million of the deferred gain that was recorded when the sale transaction was originally closed.
	During 2013, the buyer redeemed the second preferred security for $49 million, which included $4 million of accrued distributions.

Variable_Interest_Entity

Variable Interest Entity	12 Months Ended
	Dec. 31, 2014
Variable Interest Entity [Abstract]
Variable Interest Entity	Variable Interest Entity
	As stated in Note 5, we have a 35 percent ownership interest in Illinois Extension Pipeline through our contributions to the SAX project. Illinois Extension Pipeline Company LLC is considered a variable interest entity (“VIE”) because it is a development stage entity and the equity in the entity is not sufficient to fund the current stage of development, which is the construction of the SAX pipeline. Our maximum exposure to loss due to this VIE at December 31, 2014 was $120 million, which equates to our contributions to-date to fund our portion of the construction costs for the project.
	We are not the primary beneficiary of this VIE and, therefore, do not consolidate it because we do not have the power to control the activities that significantly influence the economic activities of the entity. The activities that most significantly impact the VIE’s economic performance during the construction phase are the actual construction costs and risks associated with the construction process. Through our vote, we have shared power to direct the construction activities, but do not have the sole ability to control the construction activities.

Related_Party_Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2014
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions
	Our related parties included:
	•	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.
	•	TAAE, in which we have a 43 percent 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.
	•	Other equity method investees.
	We believe that transactions with related parties were conducted on terms comparable to those with unaffiliated 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:
	(In millions)	2014		2013		2012
	Centennial	$	—	$	—	$	1
	Other equity method investees	7		8		7
	Total	$	7	$	8	$	8
	Related party sales to Centennial consist primarily of petroleum products.
	The fees received for operating Centennial’s pipeline, which are included in other income on the consolidated statements of income, were $1 million in 2014, 2013 and 2012.
	Purchases from related parties were as follows:
	(In millions)	2014		2013		2012
	Centennial	$	7	$	3	$	7
	Explorer	39		—		—
	LOCAP	21		17		24
	LOOP	88		43		44
	TAAE	79		24		—
	TACE	121		130		73
	TAME	141		131		124
	Other equity method investees	9		9		8
	Total	$	505	$	357	$	280
	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. 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:
		December 31,
	(In millions)	2014		2013
	Centennial	$	2	$	1
	Explorer	2		—
	TAME	3		1
	Total	$	7	$	2
	Long-term receivable from Centennial, which is included in other noncurrent assets on the consolidated balance sheet, was less than $1 million at December 31, 2014 and $2 million at December 31, 2013.
	Payables to related parties, which are included in accounts payable on the consolidated balance sheets, were as follows:
		December 31,
	(In millions)	2014		2013
	Explorer	$	3	$	—
	LOCAP	2		2
	LOOP	4		3
	TAAE	2		2
	TACE	2		4
	TAME	5		5
	Total	$	18	$	16

Income_per_Common_Share

Income per Common Share	12 Months Ended
	Dec. 31, 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.
	(In millions, except per share data)	2014			2013			2012
	Basic earnings per share:
	Allocation of earnings:
	Net income attributable to MPC	$	2,524		$	2,112		$	3,389
	Income allocated to participating securities	4			4			6
	Income available to common stockholders – basic	$	2,520		$	2,108		$	3,383
	Weighted average common shares outstanding	285			315			340
	Basic earnings per share	$	8.84		$	6.69		$	9.95
	Diluted earnings per share:
	Allocation of earnings:
	Net income attributable to MPC	$	2,524		$	2,112		$	3,389
	Income allocated to participating securities	4			4			6
	Income available to common stockholders – diluted	$	2,520		$	2,108		$	3,383
	Weighted average common shares outstanding	285			315			340
	Effect of dilutive securities	2			2			2
	Weighted average common shares, including dilutive effect	287			317			342
	Diluted earnings per share	$	8.78		$	6.64		$	9.89
	The following table summarizes the shares that were anti-dilutive, and therefore, were excluded from the diluted share calculation.
	(In millions)	2014		2013			2012
	Shares issued under stock-based compensation plans	—		—			2

Equity

Equity	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Equity	Equity
	On July 30, 2014, our board of directors approved an additional $2.0 billion share repurchase authorization expiring in July 2016. As of December 31, 2014, our board of directors had approved $8.0 billion in total share repurchase authorizations since January 1, 2012 and we have repurchased a total of $6.27 billion of our common stock under these authorizations, leaving $1.73 billion available for repurchases. Under these authorizations, we have acquired 89 million shares at an average cost per share of $70.35.
	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.
	In February 2012 and November 2012, we entered into $850 million and $500 million accelerated share repurchase (“ASR”) programs, respectively, to repurchase shares of MPC common stock under the approved share repurchase plan authorized by our board of directors. The total number of shares repurchased under these ASR programs was based generally on the volume-weighted average price of our common stock during the repurchase periods. The shares repurchased under the ASR programs were accounted for as treasury stock purchase transactions, reducing the weighted average number of basic and diluted common shares outstanding by the shares repurchased, and as forward contracts indexed to our common stock. The forward contracts were accounted for as equity instruments.
	Total share repurchases were as follows for the respective periods:
	(In millions, except per share data)	2014		2013		2012
	Number of shares repurchased(a)	24		37		28
	Cash paid for shares repurchased	$	2,131	$	2,793	$	1,350
	Effective average cost per delivered share	$	88.63	$	76.14	$	46.73
	(a)	Shares repurchased in 2013 includes 1 million shares received under the November 2012 ASR program, which were paid for in 2012.
	At December 31, 2014, we had agreements to acquire 99,084 common shares for $9 million, which were settled in early January 2015.

Segment_Information

Segment Information	12 Months Ended
	Dec. 31, 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, buyers on the spot market, 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, East Coast and Southeast.
	•	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.
	On September 30, 2014, we acquired Hess’ Retail Operations and Related Assets, which are part of the Speedway and Refining & Marketing segments. 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 periods prior to each acquisition does not include amounts for these operations. See Note 5.
	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
	Year Ended December 31, 2014
	Revenues:
	Customer	$	80,822		$	16,927		$	70		$	97,819
	Intersegment(a)	10,912			5			527			11,444
	Segment revenues	$	91,734		$	16,932		$	597		$	109,263
	Segment income from operations(b)	$	3,609		$	544		$	280		$	4,433
	Income from equity method investments	96			—			57			153
	Depreciation and amortization(c)	1,045			152			77			1,274
	Capital expenditures and investments(d)(e)	1,104			2,981			543			4,628
	(In millions)	Refining & Marketing			Speedway			Pipeline Transportation			Total
	Year Ended December 31, 2013
	Revenues:
	Customer	$	85,616		$	14,471		$	79		$	100,166
	Intersegment(a)	9,294			4			458			9,756
	Segment revenues	$	94,910		$	14,475		$	537		$	109,922
	Segment income from operations(b)	$	3,206		$	375		$	210		$	3,791
	Income from equity method investments	28			—			8			36
	Depreciation and amortization(c)	1,011			112			74			1,197
	Capital expenditures and investments(d)(f)	2,094			296			234			2,624
	(In millions)	Refining & Marketing			Speedway			Pipeline Transportation			Total
	Year Ended December 31, 2012
	Revenues:
	Customer	$	67,928		$	14,239		$	78		$	82,245
	Intersegment(a)	8,782			4			381			9,167
	Segment revenues	$	76,710		$	14,243		$	459		$	91,412
	Segment income from operations(b)	$	5,098		$	310		$	216		$	5,624
	Income (loss) from equity method investments	(6		)	—			32			26
	Depreciation and amortization(c)	804			114			54			972
	Capital expenditures and investments(d)	705			340			211			1,256
	(a)	Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties.
	(b)	Included in the Pipeline Transportation segment for 2014, 2013 and 2012 are $19 million, $20 million and $4 million of corporate overhead expenses attributable to MPLX, which were included in items not allocated to segments prior to MPLX’s October 31, 2012 initial public offering. Corporate overhead expenses are not currently allocated to other 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 Speedway and Refining & Marketing segments include $2.66 billion and $52 million, respectively, for the acquisition of Hess’ Retail Operations and Related Assets. See Note 5.
	(f)	The Refining & Marketing and Pipeline Transportation segments include $1.29 billion and $70 million, respectively, for the acquisition of the Galveston Bay Refinery and Related Assets. See Note 5.
	The following reconciles segment income from operations to income before income taxes as reported in the consolidated statements of income:
	(In millions)	2014			2013			2012
	Segment income from operations	$	4,433		$	3,791		$	5,624
	Items not allocated to segments:
	Corporate and other unallocated items(a)(b)	(286		)	(271		)	(336		)
	Minnesota Assets sale settlement gain(c)	—			—			183
	Pension settlement expenses(d)	(96		)	(95		)	(124		)
	Net interest and other financial income (costs)	(216		)	(179		)	(109		)
	Income before income taxes	$	3,835		$	3,246		$	5,238
	(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 were included in the Pipeline Transportation segment subsequent to MPLX’s October 31, 2012 initial public offering. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments.
	(c)	See Note 6.
	(d)	See Note 23.
	The following reconciles segment capital expenditures and investments to total capital expenditures:
	(In millions)	2014			2013			2012
	Segment capital expenditures and investments	$	4,628		$	2,624		$	1,256
	Less: Investments in equity method investees	413			124			28
	Plus: Items not allocated to segments:
	Capital expenditures not allocated to segments	83			137			103
	Capitalized interest	27			28			101
	Total capital expenditures(a)(b)	$	4,325		$	2,665		$	1,432
(a)	Capital expenditures include changes in capital accruals.
(b)	See Note 21 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 total revenues to sales and other operating revenues (including consumer excise taxes) as reported in the consolidated statements of income:
(In millions)	2014			2013			2012
Customer revenues	$	97,819		$	100,166		$	82,245
Corporate and other unallocated items	(2		)	(6		)	(2		)
Sales and other operating revenues (including consumer excise taxes)	$	97,817		$	100,160		$	82,243
Revenues by product line were:
(In millions)	2014			2013			2012
Refined products	$	90,702		$	93,520		$	76,234
Merchandise	3,817			3,308			3,229
Crude oil and refinery feedstocks	2,917			2,988			2,514
Transportation and other	381			344			266
Sales and other operating revenues (including consumer excise taxes)	$	97,817		$	100,160		$	82,243
No single customer accounted for more than 10 percent of annual revenues for the years ended December 31, 2014 and 2012. Revenue from BP p.l.c. included in the Refining & Marketing segment represented 10 percent of our total annual revenues for the year ended December 31, 2013.
We do not have significant operations in foreign countries. Therefore, revenues in foreign countries and long-lived assets located in foreign countries, including property, plant and equipment and investments, are not material to our operations.
Total assets by reportable segment were:
	December 31,
(In millions)	2014			2013
Refining & Marketing	$	19,751		$	19,573
Speedway	5,296			2,064
Pipeline Transportation	2,407			1,947
Corporate and Other	3,006			4,801
Total consolidated assets	$	30,460		$	28,385

Other_Items

Other Items	12 Months Ended
	Dec. 31, 2014
Other Income and Expenses [Abstract]
Other Items	Other Items
	Net interest and other financial income (costs) was:
	(In millions)	2014			2013			2012
	Interest income	$	7		$	9		$	6
	Interest expense	(229		)	(195		)	(191		)
	Interest capitalized	27			28			101
	Other financial costs	(21		)	(21		)	(25		)
	Net interest and other financial income (costs)	$	(216	)	$	(179	)	$	(109	)

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes
	Income tax provisions (benefits) were:
		2014											2013							2012
	(In millions)	Current				Deferred				Total			Current		Deferred			Total		Current			Deferred		Total
	Federal	$	1,382			$	(199	)		$	1,183		$	954	$	20		$	974	$	1,185		$	432	$	1,617
	State and local	135				(37		)		98			131		8			139		169			57		226
	Foreign	5				(6		)		(1		)	5		(5		)	—		(1		)	3		2
	Total	$	1,522			$	(242	)		$	1,280		$	1,090	$	23		$	1,113	$	1,353		$	492	$	1,845
	A reconciliation of the federal statutory income tax rate (35 percent) applied to income before income taxes to the provision for income taxes follows:
		2014			2013			2012
	Statutory rate applied to income before income taxes	35	%		35	%		35	%
	State and local income taxes, net of federal income tax effects	2			3			2
	Domestic manufacturing deduction	(2	)		(2	)		(1	)
	Other	(2	)		(2	)		(1	)
	Provision for income taxes	33	%		34	%		35	%
	Deferred tax assets and liabilities resulted from the following:
		December 31,
	(In millions)	2014				2013
	Deferred tax assets:
	Employee benefits	$	616			$	483
	Environmental	54				37
	Investments in subsidiaries and affiliates	24				—
	Other	70				49
	Total deferred tax assets	764				569
	Deferred tax liabilities:
	Property, plant and equipment	2,411				2,290
	Inventories	614				614
	Investments in subsidiaries and affiliates	—				267
	Other	101				70
	Total deferred tax liabilities	3,126				3,241
	Net deferred tax liabilities	$	2,362			$	2,672
	Net deferred tax liabilities were classified in the consolidated balance sheets as follows:
		December 31,
	(In millions)	2014				2013
	Assets:
	Other noncurrent assets	$	7			$	2
	Liabilities:
	Accrued taxes	355				370
	Deferred income taxes	2,014				2,304
	Net deferred tax liabilities	$	2,362			$	2,672
	Tax carryforwards – At December 31, 2014, our federal operating loss carryforwards included $11 million acquired with the biodiesel facility acquisition, which expire in 2022 through 2034. State and local operating loss carryforwards of $1 million expire in 2015 through 2029.
	Valuation allowances – As of December 31, 2014 and 2013, $4 million and $3 million of valuation allowances were recognized related to income taxes. A federal valuation allowance was established for both December 31, 2014 and 2013 of $3 million, primarily due to the expected realizability of foreign tax credits. A state and local valuation allowance was established as of December 31, 2014 of $1 million, based on estimates of future financial income and expected realizability of state and local tax operating losses.
	MPC is continuously undergoing examination of its U.S. federal income tax returns by the Internal Revenue Service. Such audits have been completed through the 2009 tax year. We believe adequate provision has been made for federal income taxes and interest which may become payable for years not yet settled. Further, we are routinely involved in U.S. state income tax audits. We believe all other audits will be resolved with the amounts paid and/or provided for these liabilities. As of December 31, 2014, our income tax returns remain subject to examination in the following major tax jurisdictions for the tax years indicated:
	United States Federal	2010	-	2013
	States	2004	-	2013
	As a result of the Spinoff and pursuant to the tax sharing agreement by Marathon Oil and MPC, the unrecognized tax benefits related to MPC operations for which Marathon Oil was the taxpayer remain the responsibility of Marathon Oil and MPC has indemnified Marathon Oil. During 2013, we settled with Marathon Oil our U.S. federal and related state return liabilities for the 2008-2009 tax years, resulting in a reduction in unrecognized tax benefits of $21 million, which are also reflected in the table below as settlements.
	During 2013, we settled with Marathon Oil for the 2011 period prior to the spinoff based on filed tax returns and in accordance with the tax sharing agreement, resulting in a $39 million increase to additional paid-in capital.
	The following table summarizes the activity in unrecognized tax benefits:
	(In millions)	2014				2013				2012
	January 1 balance	$	13			$	40			$	20
	Additions for tax positions of prior years	7				30				32
	Reductions for tax positions of prior years	(10		)		(25		)		(6		)
	Settlements	2				(30		)		(6		)
	Statute of limitations	—				(2		)		—
	December 31 balance	$	12			$	13			$	40
	If the unrecognized tax benefits as of December 31, 2014 were recognized, $5 million would affect our effective income tax rate. There were $4 million of uncertain tax positions as of December 31, 2014 for which it is reasonably possible that the amount of unrecognized tax benefits would significantly decrease during the next twelve months.
	Interest and penalties related to income taxes are recorded as part of the provision for income taxes. Such interest and penalties were net receipts (expenses) of less than $1 million, ($11 million) and $1 million in 2014, 2013 and 2012, respectively. As of December 31, 2014 and 2013, $14 million and $15 million of interest and penalties were accrued related to income taxes.

Inventories

Inventories	12 Months Ended
	Dec. 31, 2014
Inventory Disclosure [Abstract]
Inventories	Inventories
		December 31,
	(In millions)	2014		2013
	Crude oil and refinery feedstocks	$	2,219	$	1,797
	Refined products	2,955		2,367
	Materials and supplies	302		425
	Merchandise	166		100
	Total (at cost)	$	5,642	$	4,689
	The LIFO method accounted for 94 percent and 90 percent of total inventory value at December 31, 2014 and 2013, respectively. Current acquisition costs of inventories were estimated to exceed the LIFO inventory value at December 31, 2014 and 2013 by $684 million and $4,084 million, respectively. There were no liquidations of LIFO inventories in 2014, 2013 and 2012.

Equity_Method_Investments

Equity Method Investments	12 Months Ended
	Dec. 31, 2014
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments	Equity Method Investments
		Ownership as of		Carrying value at
		December 31,		December 31,
	(In millions)	2014		2014				2013
	Centennial	50%		$	36			$	29
	Explorer	25%		95				—
	Illinois Extension Pipeline	35%		120				—
	LOCAP	59%		23				24
	LOOP	51%		230				214
	North Dakota Pipeline(a)	38%		216				24
	TAAE	43%		22				29
	TACE	60%		61				70
	TAEI	34%		19				23
	TAME(b)	50%		24				35
	Other			19				15
	Total			$	865			$	463
	(a)	We own a 38 percent interest in the Class B units of this entity. Our Class B units will be converted to an approximate 27 percent ownership interest in the Class A units of this entity upon completion of the Sandpiper pipeline construction project, which is expected to be in 2017.
	(b)	Excludes TAEI’s investment in TAME.
	Summarized financial information for equity method investees is as follows:
	(In millions)	2014				2013				2012
	Income statement data:
	Revenues and other income	$	1,430			$	1,067			$	1,025
	Income from operations	379				87				73
	Net income	316				63				47
	Balance sheet data – December 31:
	Current assets	$	990			$	339
	Noncurrent assets	2,166				1,238
	Current liabilities	280				145
	Noncurrent liabilities	957				618
	As of December 31, 2014, the carrying value of our equity method investments was $110 million higher than the underlying net assets of investees. This basis difference is being amortized or accreted into net income over the remaining estimated useful lives of the underlying net assets, except for $55 million of excess related to goodwill.
	Centennial experienced a significant reduction in shipment volumes in the second half of 2011 that has continued through 2014. At December 31, 2014, Centennial was not shipping product. As a result, we continued to evaluate the carrying value of our equity investment in Centennial and concluded that no impairment was required given our assessment of its fair value based on market participant assumptions for various potential uses of Centennial’s assets. If market conditions were to change and the owners of Centennial are unable to find an alternative use for the assets, there could be a future impairment of our Centennial interest. As of December 31, 2014, our equity investment in Centennial was $36 million and we had a $38 million guarantee associated with 50 percent of Centennial’s outstanding debt. See Note 26 for additional information on the debt guarantee.
	Dividends and partnership distributions received from equity method investees (excluding distributions that represented a return of capital previously contributed) were $170 million, $18 million and $37 million in 2014, 2013 and 2012.

Property_Plant_and_Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment
	(In millions)	Estimated	December 31,
		Useful Lives	2014		2013
	Refining & Marketing	4 - 25 years	$	18,001	$	16,982
	Speedway	4 - 25 years	4,639		2,344
	Pipeline Transportation	16 - 42 years	2,044		1,921
	Corporate and Other	4 - 40 years	618		546
	Total		25,302		21,793
	Less accumulated depreciation		9,041		7,872
	Property, plant and equipment, net		$	16,261	$	13,921
	Property, plant and equipment includes gross assets acquired under capital leases of $510 million at both December 31, 2014 and 2013, with related amounts in accumulated depreciation of $144 million and $111 million at December 31, 2014 and 2013. Property, plant and equipment includes construction in progress of $1,043 million and $747 million at December 31, 2014 and 2013, which primarily relates to refinery projects.
	Construction in progress at December 31, 2014 includes $90 million of costs associated with a residual fuel hydrocracker project at our Garyville refinery, intended to increase margins by upgrading residual fuel to ultra-low sulfur diesel and gas oil. We are deferring a final investment decision on this project with estimated total costs of $2.2 billion to $2.5 billion as we further evaluate the implications of current market conditions on the project. If a decision is made to not pursue this project, there could be a future impairment of the costs incurred for the project.

Goodwill

Goodwill	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	Goodwill
	Goodwill is tested for impairment on an annual basis and when events or changes in circumstances indicate the fair value of a reporting unit with goodwill has been reduced below the carrying value. We performed our annual impairment tests for 2014 and 2013, and no impairment was required.
	The changes in the carrying amount of goodwill for 2014 and 2013 were as follows:
	(In millions)	Refining & Marketing			Speedway		Pipeline Transportation		Total
	2013
	Beginning balance	$	551		$	217	$	162	$	930
	Acquisitions(a)	—			8		—		8
	Ending balance	$	551		$	225	$	162	$	938
	2014
	Beginning balance	$	551		$	225	$	162	$	938
	Acquisitions(a)	—			629		—		629
	Disposition	(1		)	—		—		(1		)
	Ending balance	$	550		$	854	$	162	$	1,566
	(a)	See Note 5 for information on the acquisitions.

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 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 December 31, 2014 and 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.
		December 31, 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	$	317		$	—	$	—		$	(258	)	$	59	$	—
	Other assets	2			—		—			N/A			2		—
	Total assets at fair value	$	319		$	—	$	—		$	(258	)	$	61	$	—
	Commodity derivative instruments, liabilities	$	180		$	—	$	—		$	(180	)	$	—	$	—
	Contingent consideration, liability(c)	—			—		478			N/A			478		—
	Total liabilities at fair value	$	180		$	—	$	478		$	(180	)	$	478	$	—
		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 December 31, 2014, cash collateral of $78 million was netted with mark-to-market derivative assets. As of December 31, 2013, cash collateral of $32 million 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 $174 million at December 31, 2014 and $159 million at December 31, 2013 classified as current.
	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 December 31, 2014 and 2013 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 5. 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 $13 to $15 per barrel; and (3) a range of risk-adjusted discount rates from 5 percent to 10 percent. An increase or decrease in crack spread forecasts or refinery throughput volume expectations will 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 will 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 net beginning and ending balances recorded for liabilities classified as Level 3 in the fair value hierarchy.
	(In millions)	2014			2013		2012
	Beginning balance	$	625		$	—	$	—
	Contingent consideration agreement	—			600		—
	Contingent consideration payment	(180		)	—		—
	Unrealized and realized losses included in net income	33			25		2
	Settlements of derivative instruments	—			—		(2		)
	Ending balance	$	478		$	625	$	—
	We did not hold any Level 3 derivative instruments during 2014, 2013 and 2012. See Note 19 for the income statement impacts of our derivative instruments. There was an unrealized loss of $33 million and $25 million in 2014 and 2013, respectively, related to the contingent consideration agreement.
	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.
		Year Ended December 31,
		2014					2013						2012
	(In millions)	Fair Value			Impairment		Fair Value			Impairment			Fair Value		Impairment
	Property, plant and equipment, net	$	—		$	—	$	1		$	8		$	—	$	—
	Other noncurrent assets	—			11		—			—			—		14
	Based on the financial and operational status of a company in which we have an interest, we fully impaired our $11 million investment in that company in 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.
	As a result of changing market conditions and declining throughput volumes, we impaired our Refining & Marketing segment’s prepaid tariff with Centennial by $14 million in 2012. The fair value measurement of the prepaid tariff was based on the income approach utilizing the probability of shipping sufficient volumes on Centennial’s pipeline over the remaining life of the throughput and deficiency credits, which expired March 31, 2014. This measurement is classified as Level 3.
	Fair Values – Reported
	The following table summarizes financial instruments on the basis of their nature, characteristics and risk at December 31, 2014 and 2013, excluding the derivative financial instruments and contingent consideration reported above.
		December 31,
		2014					2013
	(In millions)	Fair Value			Carrying Value		Fair Value			Carrying Value
	Financial assets:
	Investments	$	26		$	2	$	336		$	14
	Other	32			32		31			30
	Total financial assets	$	58		$	34	$	367		$	44
	Financial liabilities:
	Long-term debt(a)	$	6,571		$	6,265	$	3,306		$	3,001
	Deferred credits and other liabilities	17			17		21			21
	Total financial liabilities	$	6,588		$	6,282	$	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.

Derivatives

Derivatives	12 Months Ended
	Dec. 31, 2014
Summary of Derivative Instruments [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 18. See Note 2 for a discussion of the types of derivatives we use and the reasons for them. We do not designate any of our commodity derivative instruments as hedges for accounting purposes. Our interest rate derivative instruments were designated as fair value accounting hedges.
	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 December 31, 2014 and 2013:
		31-Dec-14
	(In millions)	Asset				Liability			Balance Sheet Location
	Commodity derivatives	$	317			$	180		Other current assets
		31-Dec-13
	(In millions)	Asset				Liability			Balance Sheet Location
	Commodity derivatives	$	21			$	53		Other current assets
	Derivatives Designated as Fair Value Accounting Hedges
	In 2012, we terminated interest rate swap agreements with a notional amount of $500 million that had been entered into as fair value accounting hedges on our 3.50 percent senior notes due in March 2016. There was a $20 million gain on the termination of the transactions, which has been accounted for as an adjustment to our long-term debt balance. The gain is being amortized over the remaining life of the 3.50 percent senior notes, which reduces our interest expense. The interest rate swaps had no accounting hedge ineffectiveness.
	The following table summarizes the pretax effect of derivative instruments designated as accounting hedges of fair value in our consolidated statements of income in 2012:
				Gain (Loss)
	(In millions)	Income Statement Location		2012
	Derivative
	Interest rate	Net interest and other financial income (costs)		$	1
	Hedged Item
	Long-term debt	Net interest and other financial income (costs)		$	(1	)
	Derivatives not Designated as Accounting Hedges
	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 table below summarizes open commodity derivative contracts for crude oil and refined products as of December 31, 2014.
		Position		Total Barrels
				(In thousands)
	Crude oil(a)
	Exchange-traded	Long		15,678
	Exchange-traded	Short		-25,257
	Refined Products(b)
	Exchange-traded	Long		2,948
	Exchange-traded	Short		-3,804
	(a )	97 percent of these contracts expire in the first quarter of 2015.
	(b)	100 percent of these contracts expire in the first quarter of 2015.
	The following table summarizes the effect of all commodity derivative instruments in our consolidated statements of income:
	(In millions)	Gain (Loss)
	Income Statement Location	2014				2013			2012
	Sales and other operating revenues	$	37			$	12		$	8
	Cost of revenues	456				(180		)	65
	Total	$	493			$	(168	)	$	73

Debt

Debt	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Debt	Debt
	Our outstanding borrowings at December 31, 2014 and 2013 consisted of the following:
		December 31,
	(In millions)	2014			2013
	Marathon Petroleum Corporation:
	Revolving credit agreement due 2017	$	—		$	—
	Term loan agreement due 2019	700			—
	3.500% senior notes due March 1, 2016	750			750
	5.125% senior notes due March 1, 2021	1,000			1,000
	3.625% senior notes due September 15, 2024	750			—
	6.500% senior notes due March 1, 2041	1,250			1,250
	4.750% senior notes due September 15, 2044	800			—
	5.000% senior notes due September 15, 2054	400			—
	Consolidated subsidiaries:
	Capital lease obligations due 2015-2028	372			395
	MPLX Operations LLC bank revolving credit agreement due 2017	—			—
	MPLX bank revolving credit facility due 2019	385			—
	MPLX term loan facility due 2019	250			—
	Trade receivables securitization facility due 2016	—			—
	Total	6,657			3,395
	Unamortized discount	(26		)	(10		)
	Fair value adjustments(a)	6			11
	Amounts due within one year	(27		)	(23		)
	Total long-term debt due after one year	$	6,610		$	3,373
	(a)	See Note 19 for information on interest rate swaps.
	The following table shows five years of scheduled debt payments.
	(In millions)
	2015	$	27
	2016	777
	2017	28
	2018	30
	2019	1,362
	MPC Revolving Credit Agreement – We have a $2.5 billion unsecured revolving credit agreement (“Credit Agreement”) in place with a maturity date of September 14, 2017. The Credit Agreement includes letter of credit issuing capacity of up to $2.0 billion and swingline loan capacity of up to $100 million. We may increase our borrowing capacity under the Credit Agreement by up to an additional $500 million, subject to certain conditions including the consent of the lenders whose commitments would be increased. In addition, the maturity date may be extended for up to two additional one-year periods subject to the approval of lenders holding greater than 50 percent of the commitments then outstanding, provided that the commitments of any non-consenting lenders will be terminated on the then-effective maturity date.
	Borrowings under the Credit Agreement bear interest at either the Adjusted LIBO Rate (as defined in the Credit Agreement) plus a margin or the Alternate Base Rate (as defined in the Credit Agreement) plus a margin. We are charged various fees and expenses in connection with the Credit Agreement, including administrative agent fees, commitment fees on the unused portion of our borrowing capacity and fees related to issued and outstanding letters of credit. The applicable interest rates and certain of the fees fluctuate based on the credit ratings in effect from time to time on our long-term debt.
	The Credit Agreement contains certain representations and warranties, affirmative and restrictive covenants and events of default that we consider to be usual and customary for arrangements of this type, including a financial covenant that requires us to maintain a ratio of Consolidated Net Debt (as defined in the Credit Agreement) to Total Capitalization (as defined in the Credit Agreement) of no greater than 0.65 to 1.00 as of the last day of each fiscal quarter. Other covenants, among other things, restrict our ability to incur debt, create liens on our assets or enter into transactions with affiliates. As of December 31, 2014, we were in compliance with the covenants contained in the Credit Agreement.
	There were no borrowings or letters of credit outstanding at December 31, 2014.
	MPC Term Loan Agreement – On August 26, 2014, we entered into a $700 million five-year senior unsecured term loan credit agreement (the “Term Loan Agreement”) with a syndicate of lenders to fund a portion of the purchase price for the acquisition of Hess’ Retail Operations and Related Assets. The Term Loan Agreement matures on September 24, 2019 and may be prepaid at any time without premium or penalty. We are obligated to pay certain customary fees under the Term Loan Agreement, including an annual administrative fee.
	Amounts outstanding under the Term Loan Agreement bear interest at either of the following rates at our election (i) the sum of the Adjusted LIBO Rate (as defined in the Term Loan Agreement), plus a margin ranging between 0.875 percent to 1.75 percent, depending on our credit ratings, or (ii) the sum of the Base Rate (as defined in the Term Loan Agreement), plus a margin ranging between zero percent to 0.75 percent, depending on our credit ratings. The borrowings under this facility during 2014 were at an average interest rate of 1.3 percent.
	The Term Loan Agreement contains representation and warranties, covenants and events of default that are substantially similar to those contained in the MPC revolving credit agreement, including a financial covenant, which requires us to maintain, as of the last day of each fiscal quarter, a ratio of Consolidated Net Debt to Total Capitalization (as defined in the Term Loan Agreement) of no greater than 0.65 to 1.00. As of December 31, 2014, we were in compliance with the covenants contained in the Credit Agreement.
	Senior Notes – On September 5, 2014, we completed a public offering of $1.95 billion aggregate principal amount of senior unsecured notes (the “Senior Notes”), consisting of $750 million aggregate principal amount of our Senior Notes due 2024, $800 million aggregate principal amount of our Senior Notes due 2044 and $400 million aggregate principal amount of our Senior Notes due 2054. The net proceeds from the offering of the Senior Notes were approximately $1.92 billion, after deducting underwriting discounts and estimated offering expenses. The net proceeds were used to fund a portion of the purchase price for the acquisition of Hess’ Retail Operations and Related Assets. Interest on each series of Senior Notes is payable semi-annually in arrears on March 15 and September 15 of each year, commencing on March 15, 2015.
	The Senior Notes are unsecured and unsubordinated obligations of ours and rank equally with all our other existing and future unsecured and unsubordinated indebtedness.
	MPLX Credit Agreement – On November 20, 2014, MPLX entered into a credit agreement with a syndicate of lenders (“MPLX Credit Agreement”), which provides for a five-year $1 billion bank revolving credit facility and a $250 million term loan facility. The maturity date on both facilities is November 20, 2019.
	The bank revolving credit facility includes letter of credit issuing capacity of up to $250 million and swingline loan capacity of up to $100 million. The borrowing capacity under the MPLX Credit Agreement may be increased by up to an additional $500 million, subject to certain conditions, including the consent of the lenders whose commitments would increase. In addition, the maturity date may be extended up to two additional one-year periods subject to the approval of lenders holding the majority of the commitments then outstanding, provided that the commitments of any non-consenting lenders will be terminated on the original maturity date.
	The term loan facility was drawn in full on November 20, 2014. The maturity date for the term loan facility may be extended for up to two additional one-year periods subject to the consent of the lenders holding a majority of the outstanding term loan borrowings, provided that the portion of the term loan borrowings held by any non-consenting lenders will continue to be due and payable on the original maturity date. The borrowings under this facility during 2014 were at an average interest rate of 1.4 percent.
	Borrowings under the MPLX Credit Agreement bear interest at either the Adjusted LIBO Rate or the Alternate Base Rate (as defined in the MPLX Credit Agreement) plus a specified margin. MPLX is charged various fees and expenses in connection with the agreement, including administrative agent fees, commitment fees on the unused portion of the bank revolving credit facility and fees with respect to issued and outstanding letters of credit. The applicable interest rates and certain of the fees fluctuate based on the credit ratings in effect from time to time on MPLX’s long-term debt.
	The MPLX Credit Agreement includes certain representations and warranties, affirmative and restrictive covenants and events of default that we consider to be usual and customary for an agreement of this type. The MPLX Credit Agreement includes a financial covenant that requires MPLX to maintain a ratio of Consolidated Total Debt as of the end of each fiscal quarter to Consolidated EBITDA (both as defined in the MPLX Credit Agreement) for the prior four fiscal quarters of no greater than 5.0 to 1.0 (or 5.5 to 1.0 for up to two fiscal quarters following certain acquisitions). Consolidated EBITDA is subject to adjustments for certain acquisitions completed and capital projects undertaken during the relevant period. Other covenants restrict MPLX from incurring debt, creating liens on its assets and entering into transactions with affiliates. As of December 31, 2014, MPLX was in compliance with the covenants contained in the MPLX Credit Agreement.
	In connection with entering into this new credit agreement, MPLX terminated its previously existing $500 million five-year MPLX Operations LLC bank revolving credit agreement, dated as of September 14, 2012. During 2014, MPLX borrowed $280 million under the MPLX Operations LLC bank revolving credit agreement, at an average interest rate of 1.5 percent, per annum, and repaid all of these borrowings.
	During 2014, MPLX borrowed $630 million under the new revolving credit agreement, at an average interest rate of 1.4 percent, per annum, and repaid $245 million of these borrowings. At December 31, 2014, MPLX had $385 million of borrowings and no letters of credit outstanding under the MPLX Credit Agreement, resulting in total unused loan availability of $615 million, or 61.5 percent of the borrowing capacity.
	Trade receivables securitization facility – On December 18, 2013, we entered into a three-year, $1.3 billion trade receivables securitization facility with a group of financial institutions that act as committed purchasers, conduit purchasers, letter of credit issuers and managing agents under the facility. The facility is evidenced by a Receivables Purchase Agreement and a Second Amended and Restated Receivables Sale Agreement and replaces the previously existing accounts receivable facility that was set to expire on June 30, 2014.
	The facility consists of one of our wholly-owned subsidiaries, Marathon Petroleum Company LP (“MPC LP”), selling or contributing on an on-going basis all of its trade receivables (including trade receivables acquired from Marathon Petroleum Trading Canada LLC, a wholly-owned subsidiary of MPC LP), together with all related security and interests in the proceeds thereof, without recourse, to another wholly-owned, bankruptcy-remote special purpose subsidiary, MPC Trade Receivables Company LLC (“TRC”), in exchange for a combination of cash, equity or a subordinated note issued by TRC to MPC LP. TRC, in turn, has the ability to finance its purchase of the receivables from MPC LP by selling undivided ownership interests in qualifying trade receivables, together with all related security and interests in the proceeds thereof, without recourse, to the purchasing group in exchange for cash proceeds. The facility also provides for the issuance of letters of credit of up to an initial amount of $1.25 billion, provided that the aggregate credit exposure of the purchasing group is limited to no more than $1.3 billion at any one time.
	To the extent that TRC retains an ownership interest in the receivables it has purchased or received from MPC LP, such interest will be included in our consolidated financial statements solely as a result of the consolidation of the financial statements of TRC with those of MPC. The receivables sold or contributed to TRC are available first and foremost to satisfy claims of the creditors of TRC and are not available to satisfy the claims of creditors of MPC. TRC has granted a security interest in all of its assets to the purchasing group to secure its obligations under the Receivables Purchase Agreement.
	Proceeds from the sale of undivided percentage ownership interests in qualifying receivables under the facility will be reflected as debt on our consolidated balance sheet. We will remain responsible for servicing the receivables sold to the purchasing group. TRC pays floating-rate interest charges and usage fees on amounts outstanding under the facility, if any, and certain other fees related to the administration of the facility and letters of credit that are issued and outstanding under the facility.
	The Receivables Purchase Agreement and Second Amended and Restated Receivables Sale Agreement include representations and covenants that we consider usual and customary for arrangements of this type. Trade receivables are subject to customary criteria, limits and reserves before being deemed to qualify for sale by TRC pursuant to the facility. In addition, further purchases of qualified trade receivables under the facility are subject to termination, and TRC may be subject to default fees, upon the occurrence of certain amortization events that are included in the Receivables Purchase Agreement, which we consider to be usual and customary for arrangements of this type. At December 31, 2014, we were in compliance with the covenants contained in the Receivables Purchase Agreement.
	As of December 31, 2014, eligible trade receivables supported borrowings of $1.28 billion. There were no borrowings outstanding at December 31, 2014. As of January 31, 2015, eligible trade receivables supported borrowings of $700 million.

Supplemental_Cash_Flow_Informa

Supplemental Cash Flow Information	12 Months Ended
	Dec. 31, 2014
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information
	(In millions)	2014		2013		2012
	Net cash provided by operating activities included:
	Interest paid (net of amounts capitalized)	$	166	$	161	$	67
	Net income taxes paid to taxing authorities(a)	1,362		1,099		1,211
	Non-cash investing and financing activities:
	Capital lease obligations increase	$	—	$	61	$	62
	Property, plant and equipment sold	4		43		—
	Property, plant and equipment acquired	4		—		—
	Preferred equity interest received in contract settlement(b)	—		—		45
	Preferred equity interest dividend received in-kind	—		—		1
	Acquisition:
	Contingent consideration(c)	—		600		—
	Payable to seller(c)	—		6		—
	Intangible asset acquired	—		—		3
	Liability assumed	—		—		2
	(a)	U.S. and most state income taxes, if incurred, were paid by Marathon Oil for periods prior to the Spinoff. The amount for 2012 includes payments of $181 million for 2011 return period income taxes made to Marathon Oil under our tax sharing agreement, and in return we received an equal amount of tax credits. See Note 26.
	(b)	See Note 6.
	(c)	See Note 5.
	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:
	(In millions)	2014		2013		2012
	Additions to property, plant and equipment per consolidated statements of cash flows	$	1,480	$	1,206	$	1,369
	Non-cash additions to property, plant and equipment	4		—		—
	Asset retirement expenditures(a)	2		—		—
	Increase (decrease) in capital accruals	95		73		(117		)
	Total capital expenditures before acquisitions	1,581		1,279		1,252
	Acquisitions(b)	2,744		1,386		180
	Total capital expenditures	$	4,325	$	2,665	$	1,432
	(a)	Included in All other, net – Operating activities on the consolidated statements of cash flows.
	(a)	The 2014 acquisitions include the acquisition of Hess’ Retail Operations and Related Assets. The 2013 acquisitions include the acquisition of the Galveston Bay Refinery and Related Assets. The acquisition numbers above include property, plant and equipment and intangibles. See Note 5.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Loss	12 Months Ended
	Dec. 31, 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	198			(13		)	—		4			189
	Amounts reclassified from accumulated other comprehensive loss:
	Amortization – prior service credit(a)	(45		)	(4		)	—		—			(49		)
	– actuarial loss(a)	66			3			—		—			69
	– settlement loss(a)	95			—			—		—			95
	Other(b)	—			—			—		(1		)	(1		)
	Tax effect	(43		)	—			—		—			(43		)
	Other comprehensive income (loss)	271			(14		)	—		3			260
	Balance as of December 31, 2013	$	(161	)	$	(50	)	$	4	$	3		$	(204	)
	(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	(119		)	(53		)	—		2			(170		)
	Amounts reclassified from accumulated other comprehensive loss:
	Amortization – prior service credit(a)	(46		)	(4		)	—		—			(50		)
	– actuarial loss(a)	51			2			—		—			53
	– settlement loss(a)	96			—			—		—			96
	Other(b)	—			—			—		(1		)	(1		)
	Tax effect	(38		)	1			—		—			(37		)
	Other comprehensive income (loss)	(56		)	(54		)	—		1			(109		)
	Balance as of December 31, 2014	$	(217	)	$	(104	)	$	4	$	4		$	(313	)
	(a)	These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 23.
	(b)	This amount was reclassified out of accumulated other comprehensive loss and is included in selling, general and administrative expenses on the consolidated statements of income.

Defined_Benefit_Pension_and_Ot

Defined Benefit Pension and Other Postretirement Plans	12 Months Ended
	Dec. 31, 2014
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]
Defined Benefit Pension and Other Postretirement Plans	Defined Benefit Pension and Other Postretirement Plans
	We have noncontributory defined benefit pension plans covering substantially all employees. Benefits under these plans have been based primarily on age, years of service and final average pensionable earnings. The years of service component of this formula was frozen as of December 31, 2009. Benefits for service beginning January 1, 2010 are based on a cash balance formula with an annual percentage of eligible pay credited based upon age and years of service. Eligible Speedway employees accrue benefits under a defined contribution plan for service years beginning January 1, 2010.
	We also have other postretirement benefits covering most employees. Health care benefits are provided through comprehensive hospital, surgical and major medical benefit provisions subject to various cost-sharing features. Retiree life insurance benefits are provided to a closed group of retirees. Other postretirement benefits are not funded in advance.
	Due to the Galveston Bay Refinery and Related Assets acquisition during 2013, we remeasured certain pension and retiree medical plans resulting in a $122 million decrease in liabilities. The decrease in liabilities was due to a 0.2 percent increase in discount rates and an increase in pension plan asset value from December 31, 2012 to the remeasurement date. The net periodic benefit costs for 2013 reflect these remeasurements. The purchase accounting for the Galveston Bay Refinery and Related Assets acquisition includes a $43 million liability related to retiree medical assumed at the acquisition date. See Note 5.
	Obligations and funded status – The accumulated benefit obligation for all defined benefit pension plans was $2,009 million and $1,912 million as of December 31, 2014 and 2013.
	The following summarizes our defined benefit pension plans that have accumulated benefit obligations in excess of plan assets.
		December 31,
	(In millions)	2014				2013
	Projected benefit obligations	$	2,075			$	1,927
	Accumulated benefit obligations	2,009				1,912
	Fair value of plan assets	1,744				1,800
	The following summarizes the projected benefit obligations and funded status for our defined benefit pension and other postretirement plans:
		Pension Benefits								Other Benefits
	(In millions)	2014				2013				2014			2013
	Change in benefit obligations:
	Benefit obligations at January 1	$	1,927			$	2,192			$	687		$	591
	Service cost	88				93				27			25
	Interest cost	74				73				33			26
	Actuarial (gain) loss	257				(183		)		86			17
	Benefits paid	(271		)		(248		)		(23		)	(20		)
	Other(a)	—				—				2			48
	Benefit obligations at December 31	2,075				1,927				812			687
	Change in plan assets:
	Fair value of plan assets at January 1	1,800				1,478				—			—
	Actual return on plan assets	175				241				—			—
	Employer contributions	40				329				—			—
	Benefits paid from plan assets	(271		)		(248		)		—			—
	Fair value of plan assets at December 31	1,744				1,800				—			—
	Funded status of plans at December 31	$	(331	)		$	(127	)		$	(812	)	$	(687	)
	Amounts recognized in the consolidated balance sheets:
	Current liabilities	$	(17	)		$	(18	)		$	(27	)	$	(25	)
	Noncurrent liabilities	(314		)		(109		)		(785		)	(662		)
	Accrued benefit cost	$	(331	)		$	(127	)		$	(812	)	$	(687	)
	Pretax amounts recognized in accumulated other comprehensive loss:(b)
	Net loss	$	710			$	668			$	191		$	107
	Prior service credit	(369		)		(415		)		(26		)	(30		)
	(a)	Includes adjustments related to Hess’ Retail Operations and Related Assets acquisition in 2014. For 2013, it includes adjustments related to plan amendments and adjustments related to the Galveston Bay Refinery and Related Assets acquisition.
	(b)	Amounts exclude those related to LOOP and Explorer Pipeline, equity method investees with defined benefit pension and postretirement plans for which net losses of $18 million and $1 million were recorded in accumulated other comprehensive loss in 2014, reflecting our ownership share.
	Components of net periodic benefit cost and other comprehensive loss – The following summarizes the net periodic benefit costs and the amounts recognized as other comprehensive loss for our defined benefit pension and other postretirement plans.
		Pension Benefits											Other Benefits
	(In millions)	2014				2013				2012			2014				2013			2012
	Components of net periodic benefit cost:
	Service cost	$	88			$	93			$	66		$	27			$	25		$	20
	Interest cost	74				73				94			33				26			24
	Expected return on plan assets	(107		)		(107		)		(104		)	—				—			—
	Amortization – prior service cost (credit)	(46		)		(45		)		(18		)	(4		)		(4		)	(2		)
	– actuarial loss	51				66				93			2				3			2
	– settlement loss	96				95				125			—				—			—
	Net periodic benefit cost(a)	$	156			$	175			$	256		$	58			$	50		$	44
	Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax):
	Actuarial (gain) loss	$	188			$	(317	)		$	46		$	86			$	17		$	53
	Prior service cost (credit)(b)	—				—				(520		)	—				4			(40		)
	Amortization of actuarial loss	(147		)		(161		)		(218		)	(2		)		(3		)	(2		)
	Amortization of prior service cost	46				45				18			4				4			2
	Other	—				—				—			—				—			—
	Total recognized in other comprehensive loss	$	87			$	(433	)		$	(674	)	$	88			$	22		$	13
	Total recognized in net periodic benefit cost and other comprehensive loss	$	243			$	(258	)		$	(418	)	$	146			$	72		$	57
	(a)	Net periodic benefit cost reflects a calculated market-related value of plan assets which recognizes changes in fair value over three years.
	(b)	Includes adjustments due to plan amendments approved in 2013 and adjustments due to changes made to the defined pension plans and the post-65 medical plan coverage effective January 1, 2013.
	Lump sum payments to employees retiring in 2014, 2013 and 2012 exceeded the plan’s total service and interest costs expected for those years. Settlement losses are required to be recorded when lump sum payments exceed total service and interest costs. As a result, pension settlement expenses were recorded in 2014, 2013 and 2012 related to our cumulative lump sum payments made during those years.
	The estimated net gain/loss and prior service credit for our defined benefit pension plans that will be amortized from accumulated other comprehensive loss into net periodic benefit cost in 2015 are $51 million and $46 million. The estimated net loss and prior service credit for our other defined benefit postretirement plans that will be amortized from accumulated other comprehensive loss into net periodic benefit cost in 2015 is $9 million and $4 million, respectively.
	Plan assumptions – The following summarizes the assumptions used to determine the benefit obligations at December 31, and net periodic benefit cost for the defined benefit pension and other postretirement plans for 2014, 2013 and 2012.
		Pension Benefits									Other Benefits
		2014			2013			2012			2014		2013			2012
Weighted-average assumptions used to determine benefit obligation:
Discount rate	3.65	%		4.3	%		3.45	%		4.15	%	4.95	%		4.05	%
Rate of compensation increase	3.7	%		3.7	%		5	%		3.7	%	3.7	%		5	%
Weighted-average assumptions used to determine net periodic benefit cost:
Discount rate	4.05	%		3.88	%		4.06	%		4.95	%	4.11	%		4.54	%
Expected long-term return on plan assets(a)	7	%		7.5	%		7.5	%		—	%	—	%		—	%
Rate of compensation increase	3.7	%		5	%		5	%		3.7	%	5	%		5	%
(a)	Effective January 1, 2015, the expected long-term rate of return on plan assets is 6.75 percent due to a continuation of a change in our primary plan investment strategy, which began January 1, 2014.
Expected long-term return on plan assets
The overall expected long-term return on plan assets assumption is determined based on an asset rate-of-return modeling tool developed by a third-party investment group. The tool utilizes underlying assumptions based on actual returns by asset category and inflation and takes into account our asset allocation to derive an expected long-term rate of return on those assets. Capital market assumptions reflect the long-term capital market outlook. The assumptions for equity and fixed income investments are developed using a building-block approach, reflecting observable inflation information and interest rate information available in the fixed income markets. Long-term assumptions for other asset categories are based on historical results, current market characteristics and the professional judgment of our internal and external investment teams.
Assumed health care cost trend
The following summarizes the assumed health care cost trend rates.
	December 31,
	2014			2013			2012
Health care cost trend rate assumed for the following year:
Medical Pre-65	8	%		8	%		8	%
Prescription drugs	7	%		7	%		7	%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate):
Medical Pre-65	5	%		5	%		5	%
Prescription drugs	5	%		5	%		5	%
Year that the rate reaches the ultimate trend rate:
Medical Pre-65	2021			2020			2020
Prescription drugs	2021			2018			2018
Effective 2013, as a result of changes in the post-65 medical plan coverage of the Marathon Petroleum Health Plan and the Marathon Petroleum Retiree Health Plan, increases are the lower of the trend rate or four percent.
Assumed health care cost trend rates have a significant effect on the amounts reported for defined benefit retiree health care plans. A one percentage point change in assumed health care cost trend rates would have the following effects:
	1-Percentage-				1-Percentage-
(In millions)	Point Increase				Point Decrease
Effect on total of service and interest cost components	$	5			$	(4	)
Effect on other postretirement benefit obligations	45				(39		)
Plan investment policies and strategies
The investment policies for our pension plan assets reflect the funded status of the plans and expectations regarding our future ability to make further contributions. Long-term investment goals are to: (1) manage the assets in accordance with the legal requirements of all applicable laws; (2) diversify plan investments across asset classes to achieve an optimal balance between risk and return and between income and growth of assets through capital appreciation; and (3) source benefit payments primarily through existing plan assets and anticipated future returns.
The investment goals are implemented to manage the plans’ funded status volatility and minimize future cash contributions. The asset allocation strategy will change over time in response to changes primarily in funded status, which is dictated by current and anticipated market conditions, the independent actions of our investment committee, required cash flows to and from the plans and other factors deemed appropriate. Such changes in asset allocation are intended to allocate additional assets to the fixed income asset class should the funded status improve. The fixed income asset class shall be invested in such a manner that its interest rate sensitivity correlates highly with that of the plans’ liabilities. Other asset classes are intended to provide additional return with associated higher levels of risk. Investment performance and risk is measured and monitored on an ongoing basis through quarterly investment meetings and periodic asset and liability studies. At December 31, 2014, the primary plan’s targeted asset allocation was 51 percent equity, private equity, real estate, and timber securities and 49 percent fixed income securities.
Fair value measurements
Plan assets are measured at fair value. The following provides a description of the valuation techniques employed for each major plan asset category at December 31, 2014 and 2013.
Cash and cash equivalents – Cash and cash equivalents include a collective fund serving as the investment vehicle for the cash reserves and cash held by third-party investment managers. The collective fund is valued at net asset value (“NAV”) on a scheduled basis using a cost approach, and is considered a Level 2 asset. Cash and cash equivalents held by third-party investment managers are valued using a cost approach and are considered Level 2.
Equity – Equity investments includes common stock, mutual and pooled funds. Common stock investments are valued using a market approach, which are priced daily in active markets and are considered Level 1. Mutual and pooled equity funds are well diversified portfolios, representing a mix of strategies in domestic, international and emerging market strategies. Mutual funds are publicly registered, valued at NAV on a daily basis using a market approach and are considered Level 1 assets. Pooled funds are valued at NAV using a market approach and are considered Level 2 assets.
Fixed Income – Fixed income investments include corporate bonds, U.S. dollar treasury bonds and municipal bonds. These securities are priced on observable inputs using a combination of market, income and cost approaches. These securities are considered Level 2 assets. Fixed income also includes a well diversified bond portfolio structured as a pooled fund. This fund is valued at NAV on a daily basis using a combination of market, income and cost approaches. It is considered a Level 2 asset.
Private Equity – Private equity investments include interests in limited partnerships which are valued using information provided by external managers for each individual investment held in the fund. These holdings are considered Level 3.
Real Estate – Real estate investments consist of interests in limited partnerships. These holdings are either appraised or valued using investment manager’s assessment of assets held. These holdings are considered Level 3.
Other – Other investments include two limited liability companies (“LLCs”) with no public market. The LLCs were formed to acquire timberland in the northwest United States. These holdings are either appraised or valued using investment manager’s assessment of assets held. These holdings are considered Level 3.
The following tables present the fair values of our defined benefit pension plans’ assets, by level within the fair value hierarchy, as of December 31, 2014 and 2013.
	31-Dec-14
(In millions)	Level 1				Level 2				Level 3			Total
Cash and cash equivalents	$	—			$	29			$	—		$	29
Equity:
Common stocks	63				—				—			63
Mutual funds	155				—				—			155
Pooled funds	—				442				—			442
Fixed income:
Corporate	—				554				—			554
Government	—				99				—			99
Pooled funds	—				254				—			254
Private equity	—				—				66			66
Real estate	—				—				57			57
Other	2				2				21			25
Total investments, at fair value	$	220			$	1,380			$	144		$	1,744
	31-Dec-13
(In millions)	Level 1				Level 2				Level 3			Total
Cash and cash equivalents	$	—			$	189			$	—		$	189
Equity:
Common stocks	69				—				—			69
Mutual funds	217				—				—			217
Pooled funds	—				590				—			590
Fixed income:
Corporate	—				356				—			356
Government	—				22				—			22
Pooled funds	—				218				—			218
Private equity	—				—				57			57
Real estate	—				—				60			60
Other	2				—				20			22
Total investments, at fair value	$	288			$	1,375			$	137		$	1,800
The following is a reconciliation of the beginning and ending balances recorded for plan assets classified as Level 3 in the fair value hierarchy:
	2014
(In millions)	Private Equity				Real Estate				Other			Total
Beginning balance	$	57			$	60			$	20		$	137
Actual return on plan assets:
Realized	6				4				—			10
Unrealized	6				4				1			11
Purchases	10				5				—			15
Sales	(13		)		(16		)		—			(29		)
Ending balance	$	66			$	57			$	21		$	144
	2013
(In millions)	Private				Real				Other			Total
	Equity				Estate
Beginning balance	$	56			$	54			$	17		$	127
Actual return on plan assets:
Realized	13				3				—			16
Unrealized	3				10				3			16
Purchases	7				5				—			12
Sales	(22		)		(12		)		—			(34		)
Ending balance	$	57			$	60			$	20		$	137
Cash Flows
Contributions to defined benefit plans – Our funding policy with respect to the funded pension plans is to contribute amounts necessary to satisfy minimum pension funding requirements, including requirements of the Pension Protection Act of 2006, plus such additional, discretionary, amounts from time to time as determined appropriate by management. In 2014, we made pension contributions totaling $16 million. We have no required funding for 2015, but may make voluntary contributions at our discretion. Cash contributions to be paid from our general assets for the unfunded pension and postretirement plans are estimated to be approximately $18 million and $27 million in 2015.
Estimated future benefit payments – The following gross benefit payments, which reflect expected future service, as appropriate, are expected to be paid in the years indicated.
(In millions)	Pension Benefits				Other Benefits
2015	$	179			$	27
2016	181				30
2017	181				33
2018	181				37
2019	179				40
2020 through 2024	810				236
Contributions to defined contribution plans – We also contribute to several defined contribution plans for eligible employees. Contributions to these plans totaled $86 million, $76 million and $60 million in 2014, 2013 and 2012, respectively.
Multiemployer Pension Plan
We contribute to one multiemployer defined benefit pension plan under the terms of a collective-bargaining agreement that covers some of our union-represented employees. The risks of participating in this multiemployer plan are different from single-employer plans in the following aspects:
•	Assets contributed to the multiemployer plan by one employer may be used to provide benefits to employees of other participating employers.
•	If a participating employer stops contributing to the plan, the unfunded obligations of the plan may be borne by the remaining participating employers.
•	If we choose to stop participating in the multiemployer plan, we may be required to pay that plan an amount based on the underfunded status of the plan, referred to as a withdrawal liability.
Our participation in this plan for 2014, 2013 and 2012 is outlined in the table below. The “EIN” column provides the Employee Identification Number for the plan. The most recent Pension Protection Act zone status available in 2014 and 2013 is for the plan’s year ended December 31, 2013 and December 31, 2012, respectively. The zone status is based on information that we received from the plan and is certified by the plan’s actuary. Among other factors, plans in the red zone are generally less than 65 percent funded. The “FIP/RP Status Pending/Implemented” column indicates a financial improvement plan or a rehabilitation plan has been implemented. The last column lists the expiration date of the collective-bargaining agreement to which the plan is subject. There have been no significant changes that affect the comparability of 2014, 2013 and 2012 contributions. Our portion of the contributions does not make up more than five percent of total contributions to the plan.
				Pension Protection				FIP/RP Status		MPC Contributions (In millions)										Surcharge		Expiration Date of
				Act Zone Status				Pending/Implemented												Imposed		Collective – Bargaining
Pension Fund		EIN		2014		2013				2014			2013				2012					Agreement
Central States, Southeast and Southwest Areas Pension Plan(a)		36-6044243		Red		Red		Implemented		$	4		$	3			$	4		No		January 31, 2019
(a)	This agreement has a minimum contribution requirement of $280 per week per employee for 2015. A total of 267 employees participated in the plan as of December 31, 2014.
Multiemployer Health and Welfare Plan
We contribute to one multiemployer health and welfare plan that covers both active employees and retirees. Through the health and welfare plan employees receive medical, dental, vision, prescription and disability coverage. Our contributions to this plan totaled $6 million, $5 million and $5 million for 2014, 2013 and 2012.

StockBased_Compensation_Plans

Stock-Based Compensation Plans	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation Plans	Stock-Based Compensation Plans
	Description of the Plans
	Effective April 26, 2012, our employees and non-employee directors became eligible to receive equity awards under the Marathon Petroleum Corporation 2012 Incentive Compensation Plan (“MPC 2012 Plan”). The MPC 2012 Plan authorizes the Compensation Committee of our board of directors (“Committee”) to grant non-qualified or incentive stock options, stock appreciation rights, stock awards (including restricted stock and restricted stock unit awards), cash awards and performance awards to our employees and non-employee directors. Under the MPC 2012 Plan, no more than 25 million shares of our common stock may be delivered and no more than 10 million shares of our common stock may be the subject of awards that are not stock options or stock appreciation rights. In the sole discretion of the Committee, 10 million shares of our common stock may be granted as incentive stock options. Shares issued as a result of awards granted under these plans are funded through the issuance of new MPC common shares.
	Prior to April 26, 2012, our employees and non-employee directors were eligible to receive equity awards under the Marathon Petroleum Corporation 2011 Second Amended and Restated Incentive Compensation Plan (“MPC 2011 Plan”).
	Stock-based awards under the Plans
	We expense all share-based payments to employees and non-employee directors based on the grant date fair value of the awards over the requisite service period, adjusted for estimated forfeitures.
	Stock Options – We grant stock options to certain officer and non-officer employees. All of the stock options granted in 2014 fell under the MPC 2012 Plan. Stock options awarded under the MPC 2011 Plan and the MPC 2012 Plan represent the right to purchase shares of our common stock at its fair market value, which is the closing price of MPC’s common stock on the date of grant. Stock options have a maximum term of ten years from the date they are granted, and vest over a requisite service period of three years. We use the Black Scholes option-pricing model to estimate the fair value of stock options granted, which requires the input of subjective assumptions.
	Stock Appreciation Rights (“SARs”) – SARs were granted under the Marathon Oil Corporation incentive compensation plan in effect prior to the Spinoff. No SARs have been granted under the MPC 2011 Plan or the MPC 2012 Plan. Similar to stock options, SARs represent the right to receive a payment equal to the excess of the fair market value of shares of MPC or Marathon Oil common stock on the date the right is exercised over the grant price. SARs have a maximum term of ten years from the date they are granted and generally vest over a requisite service period of three years. We use the Black Scholes option-pricing model to estimate the fair value of SARs granted, which requires the input of subjective assumptions. All outstanding SAR’s expired or were exercised in 2014.
	Restricted Stock and Restricted Stock Units – We grant restricted stock and restricted stock units to employees and non-employee directors. In general, restricted stock and restricted stock units granted to employees vest over a requisite service period of three years. Restricted stock and restricted stock unit awards granted after 2011 to officers are subject to an additional one year holding period after the completion of the three-year requisite service period. Prior to vesting, restricted stock recipients who received grants prior to 2012 have the right to vote such stock and receive dividends at the same time regular shareholders are paid. Restricted stock recipients who received grants in 2012 and after have the right to vote such stock; however, dividends are accrued and will be paid upon vesting. Restricted stock units granted to non-employee directors are considered to vest immediately at the time of the grant for accounting purposes, as they are non-forfeitable, but are not issued until the director’s departure from the board of directors. Restricted stock unit recipients do not have the right to vote such shares and receive dividend equivalents. The non-vested shares are not transferable and are held by our transfer agent. The fair values of restricted stock are equal to the market price of our common stock on the grant date.
	Performance Units – We grant performance unit awards to certain officer employees. The target value of all performance units is $1.00, with actual payout up to $2.00 per unit (up to 200% of target). Performance units issued under the MPC 2011 and MPC 2012 Plans have a 36-month requisite service period. The payout value of these awards will be determined by the relative ranking of the total shareholder return (“TSR”) of MPC common stock compared to the TSR of a select group of peer companies, as well as the Standard & Poor’s 500 Energy Index fund over an average of four measurement periods. These awards will be settled 25 percent in MPC common stock and 75 percent in cash. The number of shares actually distributed will be determined by dividing 25 percent of the final payout by the closing price of MPC common stock on the day the Committee certifies the final TSR rankings, or the next trading day if the certification is made outside of normal trading hours. The performance units paying out in cash are accounted for as liability awards and recorded at fair value with a mark-to-market adjustment made each quarter. The performance units that settle in shares are accounted for as equity awards.
	Total Stock-Based Compensation Expense
	The following table reflects activity related to our stock-based compensation arrangements:
	(In millions)	2014				2013				2012
	Stock-based compensation expense	$	40			$	42			$	35
	Tax benefit recognized on stock-based compensation expense	15				15				13
	Cash received by MPC upon exercise of stock option awards	26				48				108
	Tax benefit received for tax deductions for stock awards exercised	19				18				16
	Stock Option Awards
	The Black Scholes option-pricing model values used to value stock option awards granted were determined based on the following weighted average assumptions:
		2014				2013				2012
	Weighted average exercise price per share	$	85.02			$	84.65			$	42.02
	Expected life in years	5.8				6				5.8
	Expected volatility	36		%		40		%		47		%
	Expected dividend yield	1.9		%		2		%		2.6		%
	Risk-free interest rate	1.8		%		1		%		1.1		%
	Weighted average grant date fair value of stock option awards granted	$	25.37			$	27.13			$	14.45
	The expected life of stock options granted is based on historical data and represents the period of time that options granted are expected to be held prior to exercise. The 2014 assumption for expected volatility of our stock price reflects a weighting of 50 percent of our common stock implied volatility and 50 percent of MPC’s common stock historical volatility. Prior to 2014, we used a weighting of our common stock implied volatility and the historical volatility of a selected group of peers. Expected dividend yield is based on annualized dividends at the date of grant. The risk-free interest rate for periods within the expected life of the option is based on the U.S. Treasury yield curve in effect at the time of the grant.
	The following is a summary of our common stock option activity in 2014:
		Number of			Weighted Average Exercise Price				Weighted Average Remaining Contractual Terms (in years)		Aggregate Intrinsic Value (in millions)
		of Shares(a)
	Outstanding at December 31, 2013	5,147,837			$	40.08
	Granted	446,310			85.02
	Exercised	(821,948	)		33.04
	Forfeited, canceled or expired	(20,761	)		49.67
	Outstanding at December 31, 2014	4,751,438			45.47
	Vested and expected to vest at December 31, 2014	4,746,653			45.43				5.7		$	213
	Exercisable at December 31, 2014	3,795,031			38.3				5		197
	(a)	Includes an immaterial number of stock appreciation rights.
	The intrinsic value of options exercised by MPC employees during 2014, 2013 and 2012 was $48 million, $60 million and $37 million, respectively.
	As of December 31, 2014, unrecognized compensation cost related to stock option awards was $5 million, which is expected to be recognized over a weighted average period of 1.1 years.
	Restricted Stock Awards
	The following is a summary of restricted stock award activity of our common stock in 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	251,351			87.64				26,725			85.9
	RS’s Vested/RSU’s Issued	(330,971	)		55.36				(578	)		51.99
	Forfeited	(29,429	)		70.29				(133	)		76.1
	Outstanding at December 31, 2014	515,073			77.23				411,093			37.3
	Of the 411,093 restricted stock units outstanding, 409,805 are vested and have a weighted average grant date fair value of $37.16. These vested but unissued units are held by our non-employee directors, are non-forfeitable and are issuable upon the director’s departure from our board of directors.
	The following is a summary of the values related to restricted stock and restricted stock unit awards held by MPC employees and non-employee directors:
		Restricted Stock								Restricted Stock Units
		Intrinsic Value of Awards Vested During the Period (in millions)				Weighted Average Grant Date Fair Value of Awards Granted During the Period				Intrinsic Value of Awards Vested During the Period (in millions)				Weighted Average Grant Date Fair Value of Awards Granted During the Period
	2014	$	28			$	87.64			$	—			$	85.9
	2013	20				87.06				—				73.48
	2012	5				43.11				—				44.38
	As of December 31, 2014, unrecognized compensation cost related to restricted stock awards was $26 million, which is expected to be recognized over a weighted average period of 1.1 years. There was no material unrecognized compensation cost related to restricted stock unit awards.
	Performance Unit Awards
	The following table presents a summary of the 2014 activity for performance unit awards to be settled in shares:
		Number of Units			Weighted Average Grant Date Fair Value
	Outstanding at December 31, 2013	3,822,500			$	0.9
	Granted	2,033,700			0.85
	Canceled	(64,375	)		0.87
	Outstanding at December 31, 2014	5,791,825			0.88
The number of shares that would be issued upon target vesting, using the closing price of our common stock on December 31, 2014 would be 64,168 shares.
As of December 31, 2014, unrecognized compensation cost related to equity-classified performance unit awards was $2 million, which is expected to be recognized over a weighted average period of 1.5 years.
Performance units paying out in units have a grant date fair value calculated using a Monte Carlo valuation model, which requires the input of subjective assumptions. The following table provides a summary of these assumptions:
	2014				2013				2012
Risk-free interest rate	0.63		%		0.35		%		0.41		%
Look-back period	2.84 years				2.84 years				2.84 years
Expected volatility	38.51		%		41.67		%		56.06		%
Grant date fair value of performance units granted	$	0.85			$	0.95			$	0.8
The risk-free interest rate for the remaining performance period as of the grant date is based on the U.S. Treasury yield curve in effect at the time of the grant. The look-back period reflects the remaining performance period at the grant date. The assumption for the expected volatility of our stock price reflects the average MPC common stock historical volatility.
MPLX Awards
Our wholly-owned subsidiary and the general partner of MPLX, MPLX GP LLC (“MXGP”), maintains a unit-based compensation plan for officers, directors and employees (including any other individual who may be considered an “employee” under a Registration Statement on Form S-8 or any successor form) of MXGP.
The MPLX 2012 Incentive Compensation Plan (“MPLX Plan”) permits various types of equity awards including but not limited to grants of restricted phantom units and performance units. Awards granted under the MPLX Plan will be settled with MPLX units. Compensation expense for these awards was not material to our consolidated financial statements for the years ended December 31, 2014, 2013 and 2012.

Leases

Leases	12 Months Ended
	Dec. 31, 2014
Leases [Abstract]
Leases	Leases
	We lease a wide variety of facilities and equipment under operating leases, including land and building space, office equipment, storage facilities and transportation equipment. Most long-term leases include renewal options and, in certain leases, purchase options. Future minimum commitments as of December 31, 2014, for capital lease obligations and for operating lease obligations having initial or remaining non-cancelable lease terms in excess of one year are as follows:
	(In millions)	Capital		Operating
		Lease		Lease
		Obligations		Obligations
	2015	$	52	$	249
	2016	51		209
	2017	50		150
	2018	49		136
	2019	45		114
	Later years	300		468
	Total minimum lease payments	547		$	1,326
	Less imputed interest costs	176
	Present value of net minimum lease payments	$	371
	Operating lease rental expense was:
	(In millions)	2014		2013		2012
	Rental expense	$	256	$	213	$	139

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 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, including those resulting from the acquisition of Hess’ Retail Operations and Related Assets. 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 December 31, 2014 and 2013, accrued liabilities for remediation totaled $185 million and $123 million. 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, were $67 million and $51 million at December 31, 2014 and 2013, respectively.
	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 LLC. Both LOOP and LOCAP LLC have secured various financings by assigning certain of their rights under throughput and deficiency agreements that they have entered into with us. 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 follow the terms of the underlying debt obligations, some of which extend through 2037. Our maximum potential undiscounted payments under these agreements for the debt principal totaled $172 million as of December 31, 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 $38 million as of December 31, 2014.
	Marathon Oil indemnifications – In conjunction with the Spinoff, we have entered into arrangements with Marathon Oil providing indemnities and guarantees with recorded values of $2 million as of December 31, 2014, which consist of unrecognized tax benefits related to MPC, its consolidated subsidiaries and the RM&T Business operations prior to the Spinoff which are not already reflected in the unrecognized tax benefits described in Note 13, 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 the 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 $81 million as of December 31, 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 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 both December 31, 2014 and 2013, our contractual commitments to acquire property, plant and equipment and advance funds to equity method investees totaled $1.7 billion. The contractual commitments at December 31, 2014 includes $520 million of contingent consideration associated with the acquisition of the Galveston Bay Refinery and Related Assets, $703 million for contributions to North Dakota Pipeline and $185 million for contributions to the SAX project. The contractual commitments at December 31, 2013 included the $700 million contingent consideration associated with the acquisition of the Galveston Bay Refinery and Related Assets and $892 million for contributions to North Dakota Pipeline. See Note 5.

Subsequent_Event

Subsequent Event	12 Months Ended
	Dec. 31, 2014
Subsequent Events [Abstract]
Subsequent Events	Subsequent Event
	On February 12, 2015, MPLX completed an initial underwritten public offering of $500 million aggregate principal amount of four percent unsecured senior notes due February 15, 2025 (the “MPLX Senior Notes”). The MPLX Senior Notes were offered at a price to the public of 99.64 percent of par. The net proceeds of this offering were used to repay the amounts outstanding under the MPLX Credit Agreement, as well as for general partnership purposes.

Selected_Quarterly_Financial_D

Selected Quarterly Financial Data	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Data [Abstract]
Selected Quarterly Financial Data	Selected Quarterly Financial Data (Unaudited)
		2014								2013
	(In millions, except per share data)	1st Qtr.		2nd Qtr.		3rd Qtr.		4th Qtr.		1st Qtr.		2nd Qtr.		3rd Qtr.		4th Qtr.
	Revenues	$	23,285	$	26,844	$	25,438	$	22,250	$	23,330	$	25,677	$	26,256	$	24,897
	Income from operations	361		1,369		1,062		1,259		1,156		960		301		1,008
	Net income	207		864		679		805		730		599		173		631
	Net income attributable to MPC	199		855		672		798		725		593		168		626
	Net income attributable to MPC per share:
	Basic	$	0.68	$	2.97	$	2.38	$	2.88	$	2.19	$	1.84	$	0.54	$	2.09
	Diluted	0.67		2.95		2.36		2.86		2.17		1.83		0.54		2.07
	Dividends paid per share	0.42		0.42		0.5		0.5		0.35		0.35		0.42		0.42

Supplementary_Statistics

Supplementary Statistics	12 Months Ended
	Dec. 31, 2014
Text Block [Abstract]
Supplementary Statistics	Supplementary Statistics (Unaudited)
	(In millions)	2014			2013			2012
	Income from Operations by segment
	Refining & Marketing	$	3,609		$	3,206		$	5,098
	Speedway	544			375			310
	Pipeline Transportation(a)	280			210			216
	Items not allocated to segments:
	Corporate and other unallocated items(a)	(286		)	(271		)	(336		)
	Minnesota Assets sale settlement gain	—			—			183
	Pension settlement expenses	(96		)	(95		)	(124		)
	Income from operations	$	4,051		$	3,425		$	5,347
	Capital Expenditures and Investments(b)(c)
	Refining & Marketing	$	1,104		$	2,094		$	705
	Speedway	2,981			296			340
	Pipeline Transportation	543			234			211
	Corporate and Other(d)	110			165			204
	Total	$	4,738		$	2,789		$	1,460
	(a)	Included in the Pipeline Transportation segment for 2014, 2013 and 2012 are $19 million, $20 million and $4 million of corporate overhead expenses attributable to MPLX, which were included in items not allocated to segments prior to MPLX’s October 31, 2012 initial public offering. Corporate overhead expenses are not currently allocated to other segments.
	(b)	Capital expenditures include changes in capital accruals.
	(c)	Includes $2.71 billion in 2014 for the acquisition of Hess’ Retail Operations and Related Assets and $1.36 billion in 2013 for the acquisition of the Galveston Bay Refinery and Related Assets. See Note 5 to the audited consolidated financial statements.
	(d)	Includes capitalized interest of $27 million, $28 million and $101 million for 2014, 2013 and 2012, respectively.
	Supplementary Statistics (Unaudited)
		2014			2013			2012
	MPC Consolidated Refined Product Sales Volumes (thousands of barrels per day)(a)(b)	2,138			2,086			1,618
	Refining & Marketing Operating Statistics(b)
	Refining & Marketing refined product sales volume (thousands of barrels per day)(c)	2,125			2,075			1,599
	Refining & Marketing gross margin (dollars per barrel)(d)	$	15.05		$	13.24		$	17.85
	Crude oil capacity utilization percent(e)	95			96			100
	Refinery throughputs (thousands of barrels per day):(f)
	Crude oil refined	1,622			1,589			1,195
	Other charge and blendstocks	184			213			168
	Total	1,806			1,802			1,363
	Sour crude oil throughput percent	52			53			53
	WTI-priced crude oil throughput percent	19			21			28
	Refined product yields (thousands of barrels per day):(f)
	Gasoline	869			921			738
	Distillates	580			572			433
	Propane	35			37			26
	Feedstocks and special products	276			221			109
	Heavy fuel oil	25			31			18
	Asphalt	54			54			62
	Total	1,839			1,836			1,386
	Refinery direct operating costs (dollars per barrel):(g)
	Planned turnaround and major maintenance	$	1.8		$	1.2		$	1
	Depreciation and amortization	1.41			1.36			1.44
	Other manufacturing(h)	4.86			4.14			3.15
	Total	$	8.07		$	6.7		$	5.59
	Refining & Marketing Operating Statistics By Region – Gulf Coast(b)
	Refinery throughputs (thousands of barrels per day):(i)
	Crude oil refined	991			964
	Other charge and blendstocks	182			195
	Total	1,173			1,159
	Sour crude oil throughput percent	64			65
	WTI-priced crude oil throughput percent	3			7
	Refined product yields (thousands of barrels per day):(i)
	Gasoline	508			551
	Distillates	368			365
	Propane	23			23
	Feedstocks and special products	274			215
	Heavy fuel oil	13			19
	Asphalt	13			13
	Total	1,199			1,186
	Refinery direct operating costs (dollars per barrel):(g)
	Planned turnaround and major maintenance	$	1.82		$	1
Depreciation and amortization	1.15			1.09
Other manufacturing(h)	4.73			3.98
Total	$	7.7		$	6.07
Supplementary Statistics (Unaudited)
	2014			2013			2012
Refining & Marketing Operating Statistics By Region – Midwest
Refinery throughputs (thousands of barrels per day):(i)
Crude oil refined	631			625
Other charge and blendstocks	45			54
Total	676			679
Sour crude oil throughput percent	33			35
WTI-priced crude oil throughput percent	44			42
Refined product yields (thousands of barrels per day):(i)
Gasoline	361			371
Distillates	212			207
Propane	13			14
Feedstocks and special products	43			41
Heavy fuel oil	13			12
Asphalt	41			41
Total	683			686
Refinery direct operating costs (dollars per barrel):(g)
Planned turnaround and major maintenance	$	1.66		$	1.47
Depreciation and amortization	1.78			1.74
Other manufacturing(h)	4.76			4.21
Total	$	8.2		$	7.42
Speedway Operating Statistics(j)
Convenience stores at period-end	2,746			1,478			1,464
Gasoline and distillate sales (millions of gallons)	3,942			3,146			3,027
Gasoline & distillate gross margin (dollars per gallon)(k)	$	0.1775		$	0.1441		$	0.1318
Merchandise sales (in millions)	$	3,611		$	3,135		$	3,058
Merchandise gross margin (in millions)	$	975		$	825		$	795
Merchandise gross margin percent	27		%	26.3		%	26		%
Same store gasoline sales volume (period over period)	(0.7		)%	0.5		%	(0.8		)%
Same store merchandise sales (period over period)(l)	5		%	4.3		%	7		%
Pipeline Transportation Operating Statistics
Pipeline throughputs (thousands of barrels per day):(m)
Crude oil pipelines	1,241			1,293			1,191
Refined products pipelines	878			911			980
Total	2,119			2,204			2,171
(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. Starting in the fourth quarter of 2013, direct operating costs are no longer included in the Refining & Marketing gross margin and the gross margin is calculated based on total refinery throughput. All prior periods presented have been recalculated to reflect a consistent approach.
(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 thousand barrels per day (“mbpd”), 36 mbpd and 25 mbpd for 2014, 2013 and 2012, 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)	Includes the impact of Hess’ Retail Operations and Related Assets beginning on the September 30, 2014 acquisition date.
(k)	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.
(l)	Excludes cigarettes.
(m)	On owned common-carrier pipelines, excluding equity method investments.

Summary_Of_Principal_Accountin1

Summary Of Principal Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Principles applied in consolidation	Principles applied in consolidation – These consolidated financial statements include the accounts of our majority-owned, controlled subsidiaries. We consolidate MPLX, in which we own a 71.5 percent controlling financial interest, and we record a noncontrolling interest for the 28.5 percent interest owned by the public.
	Investments in entities over which we have significant influence, but not control, are accounted for using the equity method of accounting. This includes entities in which we hold majority ownership but the minority shareholders have substantive participating rights in the investee. Income from equity method investments represents our proportionate share of net income generated by the equity method investees.
	Equity method investments are generally carried at our share of net assets plus loans and advances. Such investments are assessed for impairment whenever changes in the facts and circumstances indicate a loss in value has occurred, if the loss is deemed to be other than temporary. When the loss is deemed to be other than temporary, the carrying value of the equity method investment is written down to fair value, and the amount of the write-down is included in net income. Differences in the basis of the investments and the separate net asset values of the investees, if any, are amortized into net income over the remaining useful lives of the underlying assets and liabilities, except for the excess related to goodwill.
Use of estimates	Use of estimates – The preparation of financial statements in accordance with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities as of the date of the consolidated financial statements and the reported amounts of revenues and expenses during the respective reporting periods.
Revenue recognition	Revenue recognition – Revenues are recognized when products are shipped or services are provided to customers, title is transferred, the sales price is fixed or determinable and collectability is reasonably assured. Costs associated with revenues are recorded in cost of revenues. Shipping and other transportation costs billed to our customers are presented on a gross basis in revenues and cost of revenues.
	Rebates from vendors are recognized as a reduction of cost of revenues when the initiating transaction occurs. Incentives that are derived from contractual provisions are accrued based on past experience and recognized in cost of revenues. Rebates to customers are reflected as a reduction of revenue and are accrued for in accounts payable on the consolidated balance sheets.
Crude oil and refined product exchanges and matching buy/sell transactions	Crude oil and refined product exchanges and matching buy/sell transactions – We enter into exchange contracts and matching buy/sell arrangements whereby we agree to deliver a particular quantity and quality of crude oil or refined products at a specified location and date to a particular counterparty and to receive from the same counterparty the same commodity at a specified location on the same or another specified date. The exchange receipts and deliveries are nonmonetary transactions, with the exception of associated grade or location differentials that are settled in cash. The matching buy/sell purchase and sale transactions are settled in cash. Both exchange and matching buy/sell transactions are accounted for as exchanges of inventory and no revenues are recorded. The exchange transactions are recognized at the carrying amount of the inventory transferred.
Consumer excise taxes	Consumer excise taxes – We are required by various governmental authorities, including countries, states and municipalities, to collect and remit taxes on certain consumer products. Such taxes are presented on a gross basis in revenues and costs and expenses in the consolidated statements of income.
Cash and cash equivalents	Cash and cash equivalents – Cash and cash equivalents include cash on hand and on deposit and investments in highly liquid debt instruments with maturities of three months or less.
Restricted cash	Restricted cash – Restricted cash consists of cash advances to be used for the operation and maintenance of an operated pipeline system. At December 31, 2014 and 2013, the amount of restricted cash included in other current assets on the consolidated balance sheets were $4 million and $7 million, respectively.
Accounts receivable and allowance for doubtful accounts	Accounts receivable and allowance for doubtful accounts – Our receivables primarily consist of customer accounts receivable. The allowance for doubtful accounts is the best estimate of the amount of probable credit losses in customer accounts receivable and is based on historical write-off experience. We review the allowance quarterly and past-due balances over 180 days are reviewed individually for collectability. All other customer receivables are recorded at the invoiced amounts and generally do not bear interest. Account balances for these customer receivables are generally charged directly to bad debt expense when it becomes probable the receivable will not be collected.
	Approximately 41 percent and 38 percent of our accounts receivable balances at December 31, 2014 and 2013, respectively, are related to sales of crude oil or refinery feedstocks to customers with whom we have master netting agreements. We have master netting agreements with more than 100 companies engaged in the crude oil or refinery feedstock trading and supply business or the petroleum refining industry. A master netting agreement generally provides for a once per month net cash settlement of the accounts receivable from and the accounts payable to a particular counterparty.
Inventories	Inventories – Inventories are carried at the lower of cost or market value. Cost of inventories is determined primarily under the last-in, first-out (“LIFO”) method. Costs for crude oil and refined product inventories are aggregated on a consolidated basis for purposes of assessing if the LIFO cost basis of these inventories may have to be written down to market value.
Derivative instruments	Derivative instruments – We use derivatives to economically hedge a portion of our exposure to commodity price risk and, historically, to interest rate risk. We also have limited authority to use selective derivative instruments that assume market risk. All derivative instruments are recorded at fair value. Commodity derivatives are reflected on the consolidated balance sheets on a net basis by futures commission merchant, as they are governed by master netting agreements. Cash flows related to derivatives used to hedge commodity price risk and interest rate risk are classified in operating activities with the underlying transactions.
	Fair value accounting hedges – We used interest rate swaps to hedge our exposure to interest rate risk associated with fixed interest rate debt in our portfolio. Changes in the fair values of both the hedged item and the related derivative were recognized immediately in net income with an offsetting effect included in the basis of the hedged item. The net effect was to report in net income the extent to which the accounting hedge was not effective in achieving offsetting changes in fair value. We terminated our interest rate swap agreements during 2012. There was a gain on the termination of the agreements, which has been accounted for as an adjustment to our long-term debt balance. The gain is being amortized over the remaining life of the associated debt, which reduces our interest expense.
	Derivatives not designated as accounting hedges –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. Changes in the fair value of derivatives not designated as accounting hedges are recognized immediately in net income.
	Concentrations of credit risk – All of our financial instruments, including derivatives, involve elements of credit and market risk. The most significant portion of our credit risk relates to nonperformance by counterparties. The counterparties to our financial instruments consist primarily of major financial institutions and companies within the energy industry. To manage counterparty risk associated with financial instruments, we select and monitor counterparties based on an assessment of their financial strength and on credit ratings, if available. Additionally, we limit the level of exposure with any single counterparty.
Property, plant and equipment	Property, plant and equipment – Property, plant and equipment are recorded at cost and depreciated on a straight-line basis over the estimated useful lives of the assets, which range from four to 42 years. Such assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. If the sum of the expected undiscounted future cash flows from the use of the asset and its eventual disposition is less than the carrying amount of the asset, an impairment loss is recognized based on the fair value of the asset.
	When items of property, plant and equipment are sold or otherwise disposed of, any gains or losses are reported in net income. Gains on the disposal of property, plant and equipment are recognized when earned, which is generally at the time of closing. If a loss on disposal is expected, such losses are recognized when the assets are classified as held for sale.
	Interest expense is capitalized for qualifying assets under construction. Capitalized interest costs are included in property, plant and equipment and are depreciated over the useful life of the related asset.
Goodwill	Goodwill – Goodwill represents the excess of the purchase price over the estimated fair value of the net assets acquired in the acquisition of a business. Goodwill is not amortized, but rather is tested for impairment annually and when events or changes in circumstances indicate that the fair value of a reporting unit with goodwill has been reduced below carrying value. The impairment test requires allocating goodwill and other assets and liabilities to reporting units. The fair value of each reporting unit is determined and compared to the book value of the reporting unit. If the fair value of the reporting unit is less than the book value, including goodwill, the implied fair value of goodwill is calculated. The excess, if any, of the book value over the implied fair value of goodwill is charged to net income.
Major maintenance activities	Major maintenance activities – Costs for planned turnaround, major maintenance and engineered project activities are expensed in the period incurred. These types of costs include contractor repair services, materials and supplies, equipment rentals and our labor costs.
Environmental costs	Environmental costs – Environmental expenditures are capitalized if the costs mitigate or prevent future contamination or if the costs improve environmental safety or efficiency of the existing assets. We recognize remediation costs and penalties when the responsibility to remediate is probable and the amount of associated costs can be reasonably estimated. The timing of remediation accruals coincides with completion of a feasibility study or the commitment to a formal plan of action. Remediation liabilities are accrued based on estimates of known environmental exposure and are discounted when the estimated amounts are reasonably fixed and determinable. If recoveries of remediation costs from third parties are probable, a receivable is recorded and is discounted when the estimated amount is reasonably fixed and determinable.
Asset retirement obligations	Asset retirement obligations – The fair value of asset retirement obligations is recognized in the period in which the obligations are incurred if a reasonable estimate of fair value can be made. Conditional asset retirement obligations for removal and disposal of fire-retardant material from certain refining facilities have been recognized. The fair values recorded for such obligations are based on the most probable current cost projections. The recorded asset retirement obligations are not material to the consolidated financial statements.
	Asset retirement obligations have not been recognized for some assets because the fair value cannot be reasonably estimated since the settlement dates of the obligations are indeterminate. Such obligations will be recognized in the period when sufficient information becomes available to estimate a range of potential settlement dates. The asset retirement obligations principally include the removal of underground storage tanks at our leased convenience stores at or near the time of closure and hazardous material disposal and removal or dismantlement requirements associated with the closure of certain refining, terminal and pipeline assets.
	Our practice is to keep our assets in good operating condition through routine repair and maintenance of component parts in the ordinary course of business and by continuing to make improvements based on technological advances. As a result, we believe that these assets have no expected settlement date for purposes of estimating asset retirement obligations since the dates or ranges of dates upon which we would retire these assets cannot be reasonably estimated at this time.
Income taxes	Income taxes – Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between the financial statement carrying amounts of assets and liabilities and their tax bases. Deferred tax assets are recorded when it is more likely than not that they will be realized. The realization of deferred tax assets is assessed periodically based on several factors, primarily our expectation to generate sufficient future taxable income.
Stock-based compensation arrangements	Stock-based compensation arrangements – The fair value of stock options granted to our employees is estimated on the date of grant using the Black-Scholes option pricing model. The model employs various assumptions, based on management’s estimates at the time of grant, which impact the calculation of fair value and ultimately, the amount of expense that is recognized over the vesting period of the stock option award. Of the required assumptions, the expected life of the stock option award and the expected volatility of our stock price have the most significant impact on the fair value calculation. The average expected life is based on our historical employee exercise behavior. The assumption for expected volatility of our stock price reflects a weighting of 50 percent of our common stock implied volatility and 50 percent of MPC’s common stock historical volatility.
	The fair value of restricted stock awards granted to our employees is determined based on the fair market value of our common stock on the date of grant. The fair value of performance unit awards granted to our employees is estimated on the date of grant using a Monte Carlo valuation model.
	Our stock-based compensation expense is recognized based on management’s estimate of the awards that are expected to vest, using the straight-line attribution method for all service-based awards with a graded vesting feature. If actual forfeiture results are different than expected, adjustments to recognized compensation expense may be required in future periods. Unearned stock-based compensation is charged to equity when restricted stock awards are granted. Compensation expense is recognized over the vesting period and is adjusted if conditions of the restricted stock award are not met.
Renewable fuel identification numbers (RINs)	Renewable fuel identification numbers (“RINs”) – We purchase RINs to satisfy a portion of our Renewable Fuel Standard (“RFS2”) compliance. We record a short-term intangible asset, included in other current assets on the balance sheet, for RINs owned in excess of our anticipated current period compliance requirements. The asset value is based on the product of the excess RINs as of the balance sheet date, if any, and the average cost of our RINs. We record a current liability, included in other current liabilities on the balance sheet, when we are deficient RINs based on the product of the deficient RINs as of the balance sheet date, if any, and the market price of the RINs at the balance sheet date. The cost of RINs used for compliance is reflected in cost of revenues. Any gains or losses on the sale or expiration of RINs are classified as other income.

Acquisitions_and_Investments_T

Acquisitions and Investments (Tables)	12 Months Ended
	Dec. 31, 2014
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Information [Table Text Block]	The following unaudited pro forma financial information presents consolidated results assuming Hess’ Retail Operations and Related Assets acquisition occurred on January 1, 2013 and 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 acquisitions and is not necessarily indicative of the results of future operations.
	(In millions, except per share data)	2014			2013
	Sales and other operating revenues (including consumer excise taxes)	$	106,482		$	114,148
	Net income attributable to MPC	2,547			2,142
	Net income attributable to MPC per share – basic	$	8.94		$	6.8
	Net income attributable to MPC per share – diluted	8.87			6.76
Hess Retail Operations and Related Assets
Business Acquisition [Line Items]
Components Of The Fair Value Of Consideration Transferred [Table Text Block]	The components of the fair value of consideration transferred are as follows:
	(In millions)
	Cash	$	2,824
	Net working capital adjustment estimate	(3		)
	Total fair value of consideration transferred	$	2,821
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	During the fourth quarter of 2014, an independent appraisal of the assets acquired and liabilities assumed and other evaluations were completed and finalized. Updates to the preliminary fair value measurements of assets acquired and liabilities assumed were made during the fourth quarter of 2014. The following table summarizes the amounts assigned to the assets acquired and liabilities assumed as of the acquisition date.
	(In millions)
	Cash and cash equivalents	$	49
	Receivables	123
	Inventories	165
	Other current assets	8
	Property, plant and equipment, net	2,063
	Other noncurrent assets	111
	Total assets acquired	2,519
	Accounts payable	77
	Payroll and benefits payable	15
	Consumer excise taxes payable	64
	Accrued taxes	4
	Other current liabilities	10
	Defined benefit postretirement plan obligations	2
	Deferred credits and other liabilities	155
	Total liabilities assumed	327
	Net assets acquired excluding goodwill	2,192
	Goodwill	629
	Net assets acquired	$	2,821
Business Acquisition, Pro Forma Information [Table Text Block]	The amounts of revenue and income from operations associated with Hess’ Retail Operations and Related Assets included in our consolidated statements of income for 2014 are as follows:
	(In millions)	2014
	Sales and other operating revenues (including consumer excise taxes)	$	2,403
	Income from operations	113
Galveston Bay Refinery and Related Assets
Business Acquisition [Line Items]
Components Of The Fair Value Of Consideration Transferred [Table Text Block]	The components of the fair value of consideration transferred are as follows:
	(In millions)
	Cash	$	1,491
	Fair value of contingent consideration as of acquisition date	600
	Payable to seller	6
	Post-closing adjustment	(9		)
	Total fair value of consideration transferred	$	2,088
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	During the fourth quarter of 2013, an independent appraisal of the assets acquired and liabilities assumed and other evaluations were completed and finalized. The following table summarizes the final amounts assigned to the assets acquired and liabilities assumed as of the acquisition date.
	(In millions)
	Inventories	$	935
	Other current assets	1
	Property, plant and equipment, net	1,274
	Other noncurrent assets	88
	Total assets acquired	2,298
	Accounts payable	12
	Payroll and benefits payable	14
	Long-term debt due within one year(a)	2
	Other current liabilities	6
	Long-term debt(a)	58
	Defined benefit postretirement plan obligations	43
	Deferred credits and other liabilities	75
	Total liabilities assumed	210
	Net assets acquired	$	2,088
	(a)	Represents a capital lease obligation assumed.

Related_Party_Transactions_Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 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:
	(In millions)	2014		2013		2012
	Centennial	$	—	$	—	$	1
	Other equity method investees	7		8		7
	Total	$	7	$	8	$	8
Purchases From Related Parties	Purchases from related parties were as follows:
	(In millions)	2014		2013		2012
	Centennial	$	7	$	3	$	7
	Explorer	39		—		—
	LOCAP	21		17		24
	LOOP	88		43		44
	TAAE	79		24		—
	TACE	121		130		73
	TAME	141		131		124
	Other equity method investees	9		9		8
	Total	$	505	$	357	$	280
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:
		December 31,
	(In millions)	2014		2013
	Centennial	$	2	$	1
	Explorer	2		—
	TAME	3		1
	Total	$	7	$	2
Payables To Related Parties	Payables to related parties, which are included in accounts payable on the consolidated balance sheets, were as follows:
		December 31,
	(In millions)	2014		2013
	Explorer	$	3	$	—
	LOCAP	2		2
	LOOP	4		3
	TAAE	2		2
	TACE	2		4
	TAME	5		5
	Total	$	18	$	16

Income_per_Common_Share_Tables

Income per Common Share (Tables)	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Summary of Earnings Per Common Share
	(In millions, except per share data)	2014			2013			2012
	Basic earnings per share:
	Allocation of earnings:
	Net income attributable to MPC	$	2,524		$	2,112		$	3,389
	Income allocated to participating securities	4			4			6
	Income available to common stockholders – basic	$	2,520		$	2,108		$	3,383
	Weighted average common shares outstanding	285			315			340
	Basic earnings per share	$	8.84		$	6.69		$	9.95
	Diluted earnings per share:
	Allocation of earnings:
	Net income attributable to MPC	$	2,524		$	2,112		$	3,389
	Income allocated to participating securities	4			4			6
	Income available to common stockholders – diluted	$	2,520		$	2,108		$	3,383
	Weighted average common shares outstanding	285			315			340
	Effect of dilutive securities	2			2			2
	Weighted average common shares, including dilutive effect	287			317			342
	Diluted earnings per share	$	8.78		$	6.64		$	9.89
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following table summarizes the shares that were anti-dilutive, and therefore, were excluded from the diluted share calculation.
	(In millions)	2014		2013			2012
	Shares issued under stock-based compensation plans	—		—			2

Equity_Tables

Equity (Tables)	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Share Repurchases	Total share repurchases were as follows for the respective periods:
	(In millions, except per share data)	2014		2013		2012
	Number of shares repurchased(a)	24		37		28
	Cash paid for shares repurchased	$	2,131	$	2,793	$	1,350
	Effective average cost per delivered share	$	88.63	$	76.14	$	46.73
	(a)	Shares repurchased in 2013 includes 1 million shares received under the November 2012 ASR program, which were paid for in 2012.

Segment_Information_Tables

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Income From Operations Attributable To Operating Segments
	(In millions)	Refining & Marketing			Speedway			Pipeline Transportation			Total
	Year Ended December 31, 2014
	Revenues:
	Customer	$	80,822		$	16,927		$	70		$	97,819
	Intersegment(a)	10,912			5			527			11,444
	Segment revenues	$	91,734		$	16,932		$	597		$	109,263
	Segment income from operations(b)	$	3,609		$	544		$	280		$	4,433
	Income from equity method investments	96			—			57			153
	Depreciation and amortization(c)	1,045			152			77			1,274
	Capital expenditures and investments(d)(e)	1,104			2,981			543			4,628
	(In millions)	Refining & Marketing			Speedway			Pipeline Transportation			Total
	Year Ended December 31, 2013
	Revenues:
	Customer	$	85,616		$	14,471		$	79		$	100,166
	Intersegment(a)	9,294			4			458			9,756
	Segment revenues	$	94,910		$	14,475		$	537		$	109,922
	Segment income from operations(b)	$	3,206		$	375		$	210		$	3,791
	Income from equity method investments	28			—			8			36
	Depreciation and amortization(c)	1,011			112			74			1,197
	Capital expenditures and investments(d)(f)	2,094			296			234			2,624
	(In millions)	Refining & Marketing			Speedway			Pipeline Transportation			Total
	Year Ended December 31, 2012
	Revenues:
	Customer	$	67,928		$	14,239		$	78		$	82,245
	Intersegment(a)	8,782			4			381			9,167
	Segment revenues	$	76,710		$	14,243		$	459		$	91,412
	Segment income from operations(b)	$	5,098		$	310		$	216		$	5,624
	Income (loss) from equity method investments	(6		)	—			32			26
	Depreciation and amortization(c)	804			114			54			972
	Capital expenditures and investments(d)	705			340			211			1,256
	(a)	Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties.
	(b)	Included in the Pipeline Transportation segment for 2014, 2013 and 2012 are $19 million, $20 million and $4 million of corporate overhead expenses attributable to MPLX, which were included in items not allocated to segments prior to MPLX’s October 31, 2012 initial public offering. Corporate overhead expenses are not currently allocated to other 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 Speedway and Refining & Marketing segments include $2.66 billion and $52 million, respectively, for the acquisition of Hess’ Retail Operations and Related Assets. See Note 5.
	(f)	The Refining & Marketing and Pipeline Transportation segments include $1.29 billion and $70 million, respectively, for the acquisition of the Galveston Bay Refinery and Related Assets. See Note 5.
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:
	(In millions)	2014			2013			2012
	Segment income from operations	$	4,433		$	3,791		$	5,624
	Items not allocated to segments:
	Corporate and other unallocated items(a)(b)	(286		)	(271		)	(336		)
	Minnesota Assets sale settlement gain(c)	—			—			183
	Pension settlement expenses(d)	(96		)	(95		)	(124		)
	Net interest and other financial income (costs)	(216		)	(179		)	(109		)
	Income before income taxes	$	3,835		$	3,246		$	5,238
	(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 were included in the Pipeline Transportation segment subsequent to MPLX’s October 31, 2012 initial public offering. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments.
	(c)	See Note 6.
	(d)	See Note 23.
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures	The following reconciles segment capital expenditures and investments to total capital expenditures:
	(In millions)	2014			2013			2012
	Segment capital expenditures and investments	$	4,628		$	2,624		$	1,256
	Less: Investments in equity method investees	413			124			28
	Plus: Items not allocated to segments:
	Capital expenditures not allocated to segments	83			137			103
	Capitalized interest	27			28			101
	Total capital expenditures(a)(b)	$	4,325		$	2,665		$	1,432
	(a)	Capital expenditures include changes in capital accruals.
	(b)	See Note 21 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 total revenues to sales and other operating revenues (including consumer excise taxes) as reported in the consolidated statements of income:
	(In millions)	2014			2013			2012
	Customer revenues	$	97,819		$	100,166		$	82,245
	Corporate and other unallocated items	(2		)	(6		)	(2		)
	Sales and other operating revenues (including consumer excise taxes)	$	97,817		$	100,160		$	82,243
Schedule Of Revenues By Product Line	Revenues by product line were:
	(In millions)	2014			2013			2012
	Refined products	$	90,702		$	93,520		$	76,234
	Merchandise	3,817			3,308			3,229
	Crude oil and refinery feedstocks	2,917			2,988			2,514
	Transportation and other	381			344			266
	Sales and other operating revenues (including consumer excise taxes)	$	97,817		$	100,160		$	82,243
Total Assets by Reportable Segment	Total assets by reportable segment were:
		December 31,
	(In millions)	2014			2013
	Refining & Marketing	$	19,751		$	19,573
	Speedway	5,296			2,064
	Pipeline Transportation	2,407			1,947
	Corporate and Other	3,006			4,801
	Total consolidated assets	$	30,460		$	28,385

Other_Items_Tables

Other Items (Tables)	12 Months Ended
	Dec. 31, 2014
Other Income and Expenses [Abstract]
Net Interest And Other Financial Income (Costs)	Net interest and other financial income (costs) was:
	(In millions)	2014			2013			2012
	Interest income	$	7		$	9		$	6
	Interest expense	(229		)	(195		)	(191		)
	Interest capitalized	27			28			101
	Other financial costs	(21		)	(21		)	(25		)
	Net interest and other financial income (costs)	$	(216	)	$	(179	)	$	(109	)

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Components Of Income Tax Provisions (Benefits)	Income tax provisions (benefits) were:
		2014											2013							2012
	(In millions)	Current				Deferred				Total			Current		Deferred			Total		Current			Deferred		Total
	Federal	$	1,382			$	(199	)		$	1,183		$	954	$	20		$	974	$	1,185		$	432	$	1,617
	State and local	135				(37		)		98			131		8			139		169			57		226
	Foreign	5				(6		)		(1		)	5		(5		)	—		(1		)	3		2
	Total	$	1,522			$	(242	)		$	1,280		$	1,090	$	23		$	1,113	$	1,353		$	492	$	1,845
Reconciliation Of Federal Statutory Income Tax Rate	A reconciliation of the federal statutory income tax rate (35 percent) applied to income before income taxes to the provision for income taxes follows:
		2014			2013			2012
	Statutory rate applied to income before income taxes	35	%		35	%		35	%
	State and local income taxes, net of federal income tax effects	2			3			2
	Domestic manufacturing deduction	(2	)		(2	)		(1	)
	Other	(2	)		(2	)		(1	)
	Provision for income taxes	33	%		34	%		35	%
Components Of Deferred Tax Assets And Liabilities	Deferred tax assets and liabilities resulted from the following:
		December 31,
	(In millions)	2014				2013
	Deferred tax assets:
	Employee benefits	$	616			$	483
	Environmental	54				37
	Investments in subsidiaries and affiliates	24				—
	Other	70				49
	Total deferred tax assets	764				569
	Deferred tax liabilities:
	Property, plant and equipment	2,411				2,290
	Inventories	614				614
	Investments in subsidiaries and affiliates	—				267
	Other	101				70
	Total deferred tax liabilities	3,126				3,241
	Net deferred tax liabilities	$	2,362			$	2,672
Components Of Net Deferred Tax Liabilities Classified In Consolidated Balance Sheets	Net deferred tax liabilities were classified in the consolidated balance sheets as follows:
		December 31,
	(In millions)	2014				2013
	Assets:
	Other noncurrent assets	$	7			$	2
	Liabilities:
	Accrued taxes	355				370
	Deferred income taxes	2,014				2,304
	Net deferred tax liabilities	$	2,362			$	2,672
Summary Of Income Tax Returns Subject To Examination	As of December 31, 2014, our income tax returns remain subject to examination in the following major tax jurisdictions for the tax years indicated:
	United States Federal	2010	-	2013
	States	2004	-	2013
Summary Of Activity In Unrecognized Tax Benefits	The following table summarizes the activity in unrecognized tax benefits:
	(In millions)	2014				2013				2012
	January 1 balance	$	13			$	40			$	20
	Additions for tax positions of prior years	7				30				32
	Reductions for tax positions of prior years	(10		)		(25		)		(6		)
	Settlements	2				(30		)		(6		)
	Statute of limitations	—				(2		)		—
	December 31 balance	$	12			$	13			$	40

Inventories_Tables

Inventories (Tables)	12 Months Ended
	Dec. 31, 2014
Inventory Disclosure [Abstract]
Summary Of Inventories
		December 31,
	(In millions)	2014		2013
	Crude oil and refinery feedstocks	$	2,219	$	1,797
	Refined products	2,955		2,367
	Materials and supplies	302		425
	Merchandise	166		100
	Total (at cost)	$	5,642	$	4,689

Equity_Method_Investments_Tabl

Equity Method Investments (Tables)	12 Months Ended
	Dec. 31, 2014
Equity Method Investments and Joint Ventures [Abstract]
Schedule Of Equity Method Investments
		Ownership as of		Carrying value at
		December 31,		December 31,
	(In millions)	2014		2014				2013
	Centennial	50%		$	36			$	29
	Explorer	25%		95				—
	Illinois Extension Pipeline	35%		120				—
	LOCAP	59%		23				24
	LOOP	51%		230				214
	North Dakota Pipeline(a)	38%		216				24
	TAAE	43%		22				29
	TACE	60%		61				70
	TAEI	34%		19				23
	TAME(b)	50%		24				35
	Other			19				15
	Total			$	865			$	463
	(a)	We own a 38 percent interest in the Class B units of this entity. Our Class B units will be converted to an approximate 27 percent ownership interest in the Class A units of this entity upon completion of the Sandpiper pipeline construction project, which is expected to be in 2017.
	(b)	Excludes TAEI’s investment in TAME.
Summarized Financial Information For Equity Method Investees	Summarized financial information for equity method investees is as follows:
	(In millions)	2014				2013				2012
	Income statement data:
	Revenues and other income	$	1,430			$	1,067			$	1,025
	Income from operations	379				87				73
	Net income	316				63				47
	Balance sheet data – December 31:
	Current assets	$	990			$	339
	Noncurrent assets	2,166				1,238
	Current liabilities	280				145
	Noncurrent liabilities	957				618

Property_Plant_and_Equipment_T

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Summary Of Property, Plant And Equipment
	(In millions)	Estimated	December 31,
		Useful Lives	2014		2013
	Refining & Marketing	4 - 25 years	$	18,001	$	16,982
	Speedway	4 - 25 years	4,639		2,344
	Pipeline Transportation	16 - 42 years	2,044		1,921
	Corporate and Other	4 - 40 years	618		546
	Total		25,302		21,793
	Less accumulated depreciation		9,041		7,872
	Property, plant and equipment, net		$	16,261	$	13,921

Goodwill_Tables

Goodwill (Tables)	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in Carrying Amount of Goodwill	The changes in the carrying amount of goodwill for 2014 and 2013 were as follows:
	(In millions)	Refining & Marketing			Speedway		Pipeline Transportation		Total
	2013
	Beginning balance	$	551		$	217	$	162	$	930
	Acquisitions(a)	—			8		—		8
	Ending balance	$	551		$	225	$	162	$	938
	2014
	Beginning balance	$	551		$	225	$	162	$	938
	Acquisitions(a)	—			629		—		629
	Disposition	(1		)	—		—		(1		)
	Ending balance	$	550		$	854	$	162	$	1,566
	(a)	See Note 5 for information on the acquisitions.

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 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 December 31, 2014 and 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.
		December 31, 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	$	317		$	—	$	—		$	(258	)	$	59	$	—
	Other assets	2			—		—			N/A			2		—
	Total assets at fair value	$	319		$	—	$	—		$	(258	)	$	61	$	—
	Commodity derivative instruments, liabilities	$	180		$	—	$	—		$	(180	)	$	—	$	—
	Contingent consideration, liability(c)	—			—		478			N/A			478		—
	Total liabilities at fair value	$	180		$	—	$	478		$	(180	)	$	478	$	—
		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 December 31, 2014, cash collateral of $78 million was netted with mark-to-market derivative assets. As of December 31, 2013, cash collateral of $32 million 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 $174 million at December 31, 2014 and $159 million at December 31, 2013 classified as current.
Reconciliation of Net Beginning and Ending Balances Recorded for Net Assets and Liabilities Classified as Level 3	The following is a reconciliation of the net beginning and ending balances recorded for liabilities classified as Level 3 in the fair value hierarchy.
	(In millions)	2014			2013		2012
	Beginning balance	$	625		$	—	$	—
	Contingent consideration agreement	—			600		—
	Contingent consideration payment	(180		)	—		—
	Unrealized and realized losses included in net income	33			25		2
	Settlements of derivative instruments	—			—		(2		)
	Ending balance	$	478		$	625	$	—
Assets Measured at Fair Value on a Nonrecurring Basis	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.
		Year Ended December 31,
		2014					2013						2012
	(In millions)	Fair Value			Impairment		Fair Value			Impairment			Fair Value		Impairment
	Property, plant and equipment, net	$	—		$	—	$	1		$	8		$	—	$	—
	Other noncurrent assets	—			11		—			—			—		14
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 December 31, 2014 and 2013, excluding the derivative financial instruments and contingent consideration reported above.
		December 31,
		2014					2013
	(In millions)	Fair Value			Carrying Value		Fair Value			Carrying Value
	Financial assets:
	Investments	$	26		$	2	$	336		$	14
	Other	32			32		31			30
	Total financial assets	$	58		$	34	$	367		$	44
	Financial liabilities:
	Long-term debt(a)	$	6,571		$	6,265	$	3,306		$	3,001
	Deferred credits and other liabilities	17			17		21			21
	Total financial liabilities	$	6,588		$	6,282	$	3,327		$	3,022
	(a)	Excludes capital leases

Derivatives_Tables

Derivatives (Tables)	12 Months Ended
	Dec. 31, 2014
Summary of Derivative Instruments [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 December 31, 2014 and 2013:
		31-Dec-14
	(In millions)	Asset				Liability			Balance Sheet Location
	Commodity derivatives	$	317			$	180		Other current assets
		31-Dec-13
	(In millions)	Asset				Liability			Balance Sheet Location
	Commodity derivatives	$	21			$	53		Other current assets
Pretax Effect Of Derivative Instruments Designated As Accounting Hedges Of Fair Value	The following table summarizes the pretax effect of derivative instruments designated as accounting hedges of fair value in our consolidated statements of income in 2012:
				Gain (Loss)
	(In millions)	Income Statement Location		2012
	Derivative
	Interest rate	Net interest and other financial income (costs)		$	1
	Hedged Item
	Long-term debt	Net interest and other financial income (costs)		$	(1	)
Open Commodity Derivative Contracts	The table below summarizes open commodity derivative contracts for crude oil and refined products as of December 31, 2014.
		Position		Total Barrels
				(In thousands)
	Crude oil(a)
	Exchange-traded	Long		15,678
	Exchange-traded	Short		-25,257
	Refined Products(b)
	Exchange-traded	Long		2,948
	Exchange-traded	Short		-3,804
	(a )	97 percent of these contracts expire in the first quarter of 2015.
	(b)	100 percent of these contracts expire in the first quarter of 2015.
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:
	(In millions)	Gain (Loss)
	Income Statement Location	2014				2013			2012
	Sales and other operating revenues	$	37			$	12		$	8
	Cost of revenues	456				(180		)	65
	Total	$	493			$	(168	)	$	73

Debt_Tables

Debt (Tables)	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Outstanding Borrowings	Our outstanding borrowings at December 31, 2014 and 2013 consisted of the following:
		December 31,
	(In millions)	2014			2013
	Marathon Petroleum Corporation:
	Revolving credit agreement due 2017	$	—		$	—
	Term loan agreement due 2019	700			—
	3.500% senior notes due March 1, 2016	750			750
	5.125% senior notes due March 1, 2021	1,000			1,000
	3.625% senior notes due September 15, 2024	750			—
	6.500% senior notes due March 1, 2041	1,250			1,250
	4.750% senior notes due September 15, 2044	800			—
	5.000% senior notes due September 15, 2054	400			—
	Consolidated subsidiaries:
	Capital lease obligations due 2015-2028	372			395
	MPLX Operations LLC bank revolving credit agreement due 2017	—			—
	MPLX bank revolving credit facility due 2019	385			—
	MPLX term loan facility due 2019	250			—
	Trade receivables securitization facility due 2016	—			—
	Total	6,657			3,395
	Unamortized discount	(26		)	(10		)
	Fair value adjustments(a)	6			11
	Amounts due within one year	(27		)	(23		)
	Total long-term debt due after one year	$	6,610		$	3,373
	(a)	See Note 19 for information on interest rate swaps.
Schedule Of Debt Payments	The following table shows five years of scheduled debt payments.
	(In millions)
	2015	$	27
	2016	777
	2017	28
	2018	30
	2019	1,362

Supplemental_Cash_Flow_Informa1

Supplemental Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2014
Supplemental Cash Flow Information [Abstract]
Summary of Supplemental Cash Flow Information
	(In millions)	2014		2013		2012
	Net cash provided by operating activities included:
	Interest paid (net of amounts capitalized)	$	166	$	161	$	67
	Net income taxes paid to taxing authorities(a)	1,362		1,099		1,211
	Non-cash investing and financing activities:
	Capital lease obligations increase	$	—	$	61	$	62
	Property, plant and equipment sold	4		43		—
	Property, plant and equipment acquired	4		—		—
	Preferred equity interest received in contract settlement(b)	—		—		45
	Preferred equity interest dividend received in-kind	—		—		1
	Acquisition:
	Contingent consideration(c)	—		600		—
	Payable to seller(c)	—		6		—
	Intangible asset acquired	—		—		3
	Liability assumed	—		—		2
	(a)	U.S. and most state income taxes, if incurred, were paid by Marathon Oil for periods prior to the Spinoff. The amount for 2012 includes payments of $181 million for 2011 return period income taxes made to Marathon Oil under our tax sharing agreement, and in return we received an equal amount of tax credits. See Note 26.
	(b)	See Note 6.
	(c)	See Note 5.
Schedule Of 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:
	(In millions)	2014		2013		2012
	Additions to property, plant and equipment per consolidated statements of cash flows	$	1,480	$	1,206	$	1,369
	Non-cash additions to property, plant and equipment	4		—		—
	Asset retirement expenditures(a)	2		—		—
	Increase (decrease) in capital accruals	95		73		(117		)
	Total capital expenditures before acquisitions	1,581		1,279		1,252
	Acquisitions(b)	2,744		1,386		180
	Total capital expenditures	$	4,325	$	2,665	$	1,432
	(a)	Included in All other, net – Operating activities on the consolidated statements of cash flows.
	(a)	The 2014 acquisitions include the acquisition of Hess’ Retail Operations and Related Assets. The 2013 acquisitions include the acquisition of the Galveston Bay Refinery and Related Assets. The acquisition numbers above include property, plant and equipment and intangibles. See Note 5.

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Loss (Tables)	12 Months Ended
	Dec. 31, 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	198			(13		)	—		4			189
	Amounts reclassified from accumulated other comprehensive loss:
	Amortization – prior service credit(a)	(45		)	(4		)	—		—			(49		)
	– actuarial loss(a)	66			3			—		—			69
	– settlement loss(a)	95			—			—		—			95
	Other(b)	—			—			—		(1		)	(1		)
	Tax effect	(43		)	—			—		—			(43		)
	Other comprehensive income (loss)	271			(14		)	—		3			260
	Balance as of December 31, 2013	$	(161	)	$	(50	)	$	4	$	3		$	(204	)
	(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	(119		)	(53		)	—		2			(170		)
	Amounts reclassified from accumulated other comprehensive loss:
	Amortization – prior service credit(a)	(46		)	(4		)	—		—			(50		)
	– actuarial loss(a)	51			2			—		—			53
	– settlement loss(a)	96			—			—		—			96
	Other(b)	—			—			—		(1		)	(1		)
	Tax effect	(38		)	1			—		—			(37		)
	Other comprehensive income (loss)	(56		)	(54		)	—		1			(109		)
	Balance as of December 31, 2014	$	(217	)	$	(104	)	$	4	$	4		$	(313	)
	(a)	These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 23.
	(b)	This amount was reclassified out of accumulated other comprehensive loss and is included in selling, general and administrative expenses on the consolidated statements of income.

Defined_Benefit_Pension_and_Ot1

Defined Benefit Pension and Other Postretirement Plans (Tables)	12 Months Ended
	Dec. 31, 2014
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]
Summary Of Defined Benefit Plans With Accumulated Benefit Obligations In Excess Of Plan Assets	The following summarizes our defined benefit pension plans that have accumulated benefit obligations in excess of plan assets.
		December 31,
	(In millions)	2014				2013
	Projected benefit obligations	$	2,075			$	1,927
	Accumulated benefit obligations	2,009				1,912
	Fair value of plan assets	1,744				1,800
Summary Of Projected Benefit Obligations And Funded Status For Defined Benefit Pension And Other Postretirement Plans	The following summarizes the projected benefit obligations and funded status for our defined benefit pension and other postretirement plans:
		Pension Benefits								Other Benefits
	(In millions)	2014				2013				2014			2013
	Change in benefit obligations:
	Benefit obligations at January 1	$	1,927			$	2,192			$	687		$	591
	Service cost	88				93				27			25
	Interest cost	74				73				33			26
	Actuarial (gain) loss	257				(183		)		86			17
	Benefits paid	(271		)		(248		)		(23		)	(20		)
	Other(a)	—				—				2			48
	Benefit obligations at December 31	2,075				1,927				812			687
	Change in plan assets:
	Fair value of plan assets at January 1	1,800				1,478				—			—
	Actual return on plan assets	175				241				—			—
	Employer contributions	40				329				—			—
	Benefits paid from plan assets	(271		)		(248		)		—			—
	Fair value of plan assets at December 31	1,744				1,800				—			—
	Funded status of plans at December 31	$	(331	)		$	(127	)		$	(812	)	$	(687	)
	Amounts recognized in the consolidated balance sheets:
	Current liabilities	$	(17	)		$	(18	)		$	(27	)	$	(25	)
	Noncurrent liabilities	(314		)		(109		)		(785		)	(662		)
	Accrued benefit cost	$	(331	)		$	(127	)		$	(812	)	$	(687	)
	Pretax amounts recognized in accumulated other comprehensive loss:(b)
	Net loss	$	710			$	668			$	191		$	107
	Prior service credit	(369		)		(415		)		(26		)	(30		)
	(a)	Includes adjustments related to Hess’ Retail Operations and Related Assets acquisition in 2014. For 2013, it includes adjustments related to plan amendments and adjustments related to the Galveston Bay Refinery and Related Assets acquisition.
	(b)	Amounts exclude those related to LOOP and Explorer Pipeline, equity method investees with defined benefit pension and postretirement plans for which net losses of $18 million and $1 million were recorded in accumulated other comprehensive loss in 2014, reflecting our ownership share.
Components of Net Periodic Benefit Costs	Components of net periodic benefit cost and other comprehensive loss – The following summarizes the net periodic benefit costs and the amounts recognized as other comprehensive loss for our defined benefit pension and other postretirement plans.
		Pension Benefits											Other Benefits
	(In millions)	2014				2013				2012			2014				2013			2012
	Components of net periodic benefit cost:
	Service cost	$	88			$	93			$	66		$	27			$	25		$	20
	Interest cost	74				73				94			33				26			24
	Expected return on plan assets	(107		)		(107		)		(104		)	—				—			—
	Amortization – prior service cost (credit)	(46		)		(45		)		(18		)	(4		)		(4		)	(2		)
	– actuarial loss	51				66				93			2				3			2
	– settlement loss	96				95				125			—				—			—
	Net periodic benefit cost(a)	$	156			$	175			$	256		$	58			$	50		$	44
	Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax):
	Actuarial (gain) loss	$	188			$	(317	)		$	46		$	86			$	17		$	53
	Prior service cost (credit)(b)	—				—				(520		)	—				4			(40		)
	Amortization of actuarial loss	(147		)		(161		)		(218		)	(2		)		(3		)	(2		)
	Amortization of prior service cost	46				45				18			4				4			2
	Other	—				—				—			—				—			—
	Total recognized in other comprehensive loss	$	87			$	(433	)		$	(674	)	$	88			$	22		$	13
	Total recognized in net periodic benefit cost and other comprehensive loss	$	243			$	(258	)		$	(418	)	$	146			$	72		$	57
	(a)	Net periodic benefit cost reflects a calculated market-related value of plan assets which recognizes changes in fair value over three years.
	(b)	Includes adjustments due to plan amendments approved in 2013 and adjustments due to changes made to the defined pension plans and the post-65 medical plan coverage effective January 1, 2013.
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Loss (Pretax)	Components of net periodic benefit cost and other comprehensive loss – The following summarizes the net periodic benefit costs and the amounts recognized as other comprehensive loss for our defined benefit pension and other postretirement plans.
		Pension Benefits											Other Benefits
	(In millions)	2014				2013				2012			2014				2013			2012
	Components of net periodic benefit cost:
	Service cost	$	88			$	93			$	66		$	27			$	25		$	20
	Interest cost	74				73				94			33				26			24
	Expected return on plan assets	(107		)		(107		)		(104		)	—				—			—
	Amortization – prior service cost (credit)	(46		)		(45		)		(18		)	(4		)		(4		)	(2		)
	– actuarial loss	51				66				93			2				3			2
	– settlement loss	96				95				125			—				—			—
	Net periodic benefit cost(a)	$	156			$	175			$	256		$	58			$	50		$	44
	Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax):
	Actuarial (gain) loss	$	188			$	(317	)		$	46		$	86			$	17		$	53
	Prior service cost (credit)(b)	—				—				(520		)	—				4			(40		)
	Amortization of actuarial loss	(147		)		(161		)		(218		)	(2		)		(3		)	(2		)
	Amortization of prior service cost	46				45				18			4				4			2
	Other	—				—				—			—				—			—
	Total recognized in other comprehensive loss	$	87			$	(433	)		$	(674	)	$	88			$	22		$	13
	Total recognized in net periodic benefit cost and other comprehensive loss	$	243			$	(258	)		$	(418	)	$	146			$	72		$	57
	(a)	Net periodic benefit cost reflects a calculated market-related value of plan assets which recognizes changes in fair value over three years.
	(b)	Includes adjustments due to plan amendments approved in 2013 and adjustments due to changes made to the defined pension plans and the post-65 medical plan coverage effective January 1, 2013.
Plan Assumptions	Plan assumptions – The following summarizes the assumptions used to determine the benefit obligations at December 31, and net periodic benefit cost for the defined benefit pension and other postretirement plans for 2014, 2013 and 2012.
		Pension Benefits									Other Benefits
		2014			2013			2012			2014		2013			2012
	Weighted-average assumptions used to determine benefit obligation:
	Discount rate	3.65	%		4.3	%		3.45	%		4.15	%	4.95	%		4.05	%
	Rate of compensation increase	3.7	%		3.7	%		5	%		3.7	%	3.7	%		5	%
	Weighted-average assumptions used to determine net periodic benefit cost:
	Discount rate	4.05	%		3.88	%		4.06	%		4.95	%	4.11	%		4.54	%
	Expected long-term return on plan assets(a)	7	%		7.5	%		7.5	%		—	%	—	%		—	%
	Rate of compensation increase	3.7	%		5	%		5	%		3.7	%	5	%		5	%
	(a)	Effective January 1, 2015, the expected long-term rate of return on plan assets is 6.75 percent due to a continuation of a change in our primary plan investment strategy, which began January 1, 2014.
Assumed Health Care Cost Trend Rates	The following summarizes the assumed health care cost trend rates.
		December 31,
		2014			2013			2012
	Health care cost trend rate assumed for the following year:
	Medical Pre-65	8	%		8	%		8	%
	Prescription drugs	7	%		7	%		7	%
	Rate to which the cost trend rate is assumed to decline (the ultimate trend rate):
	Medical Pre-65	5	%		5	%		5	%
	Prescription drugs	5	%		5	%		5	%
	Year that the rate reaches the ultimate trend rate:
	Medical Pre-65	2021			2020			2020
	Prescription drugs	2021			2018			2018
Effects Of One Percentage Point Change In Assumed Health Care Cost Trend Rates	A one percentage point change in assumed health care cost trend rates would have the following effects:
		1-Percentage-				1-Percentage-
	(In millions)	Point Increase				Point Decrease
	Effect on total of service and interest cost components	$	5			$	(4	)
	Effect on other postretirement benefit obligations	45				(39		)
Fair Values Of Defined Benefit Pension Plan Assets	The following tables present the fair values of our defined benefit pension plans’ assets, by level within the fair value hierarchy, as of December 31, 2014 and 2013.
		31-Dec-14
	(In millions)	Level 1				Level 2				Level 3			Total
	Cash and cash equivalents	$	—			$	29			$	—		$	29
	Equity:
	Common stocks	63				—				—			63
	Mutual funds	155				—				—			155
	Pooled funds	—				442				—			442
	Fixed income:
	Corporate	—				554				—			554
	Government	—				99				—			99
	Pooled funds	—				254				—			254
	Private equity	—				—				66			66
	Real estate	—				—				57			57
	Other	2				2				21			25
	Total investments, at fair value	$	220			$	1,380			$	144		$	1,744
		31-Dec-13
	(In millions)	Level 1				Level 2				Level 3			Total
	Cash and cash equivalents	$	—			$	189			$	—		$	189
	Equity:
	Common stocks	69				—				—			69
	Mutual funds	217				—				—			217
	Pooled funds	—				590				—			590
	Fixed income:
	Corporate	—				356				—			356
	Government	—				22				—			22
	Pooled funds	—				218				—			218
	Private equity	—				—				57			57
	Real estate	—				—				60			60
	Other	2				—				20			22
	Total investments, at fair value	$	288			$	1,375			$	137		$	1,800
Reconciliation Of Beginning And Ending Balances Of Plan Assets Classified As Level 3	The following is a reconciliation of the beginning and ending balances recorded for plan assets classified as Level 3 in the fair value hierarchy:
		2014
	(In millions)	Private Equity				Real Estate				Other			Total
	Beginning balance	$	57			$	60			$	20		$	137
	Actual return on plan assets:
	Realized	6				4				—			10
	Unrealized	6				4				1			11
	Purchases	10				5				—			15
	Sales	(13		)		(16		)		—			(29		)
	Ending balance	$	66			$	57			$	21		$	144
		2013
	(In millions)	Private				Real				Other			Total
		Equity				Estate
	Beginning balance	$	56			$	54			$	17		$	127
	Actual return on plan assets:
	Realized	13				3				—			16
	Unrealized	3				10				3			16
	Purchases	7				5				—			12
	Sales	(22		)		(12		)		—			(34		)
	Ending balance	$	57			$	60			$	20		$	137
Estimated Future Benefit Payment	Estimated future benefit payments – The following gross benefit payments, which reflect expected future service, as appropriate, are expected to be paid in the years indicated.
	(In millions)	Pension Benefits				Other Benefits
	2015	$	179			$	27
	2016	181				30
	2017	181				33
	2018	181				37
	2019	179				40
	2020 through 2024	810				236
Multi Employer Pension Plan	Our participation in this plan for 2014, 2013 and 2012 is outlined in the table below. The “EIN” column provides the Employee Identification Number for the plan. The most recent Pension Protection Act zone status available in 2014 and 2013 is for the plan’s year ended December 31, 2013 and December 31, 2012, respectively. The zone status is based on information that we received from the plan and is certified by the plan’s actuary. Among other factors, plans in the red zone are generally less than 65 percent funded. The “FIP/RP Status Pending/Implemented” column indicates a financial improvement plan or a rehabilitation plan has been implemented. The last column lists the expiration date of the collective-bargaining agreement to which the plan is subject. There have been no significant changes that affect the comparability of 2014, 2013 and 2012 contributions. Our portion of the contributions does not make up more than five percent of total contributions to the plan.
					Pension Protection				FIP/RP Status		MPC Contributions (In millions)										Surcharge		Expiration Date of
					Act Zone Status				Pending/Implemented												Imposed		Collective – Bargaining
	Pension Fund		EIN		2014		2013				2014			2013				2012					Agreement
	Central States, Southeast and Southwest Areas Pension Plan(a)		36-6044243		Red		Red		Implemented		$	4		$	3			$	4		No		January 31, 2019
	(a)	This agreement has a minimum contribution requirement of $280 per week per employee for 2015. A total of 267 employees participated in the plan as of December 31, 2014.

StockBased_Compensation_Plans_

Stock-Based Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award	The following table reflects activity related to our stock-based compensation arrangements:
	(In millions)	2014				2013				2012
	Stock-based compensation expense	$	40			$	42			$	35
	Tax benefit recognized on stock-based compensation expense	15				15				13
	Cash received by MPC upon exercise of stock option awards	26				48				108
	Tax benefit received for tax deductions for stock awards exercised	19				18				16
Weighted Average Assumptions Used To Value Stock Options Awards	The Black Scholes option-pricing model values used to value stock option awards granted were determined based on the following weighted average assumptions:
		2014				2013				2012
	Weighted average exercise price per share	$	85.02			$	84.65			$	42.02
	Expected life in years	5.8				6				5.8
	Expected volatility	36		%		40		%		47		%
	Expected dividend yield	1.9		%		2		%		2.6		%
	Risk-free interest rate	1.8		%		1		%		1.1		%
	Weighted average grant date fair value of stock option awards granted	$	25.37			$	27.13			$	14.45
Summary of Stock Option Award Activity	The following is a summary of our common stock option activity in 2014:
		Number of			Weighted Average Exercise Price				Weighted Average Remaining Contractual Terms (in years)		Aggregate Intrinsic Value (in millions)
		of Shares(a)
	Outstanding at December 31, 2013	5,147,837			$	40.08
	Granted	446,310			85.02
	Exercised	(821,948	)		33.04
	Forfeited, canceled or expired	(20,761	)		49.67
	Outstanding at December 31, 2014	4,751,438			45.47
	Vested and expected to vest at December 31, 2014	4,746,653			45.43				5.7		$	213
	Exercisable at December 31, 2014	3,795,031			38.3				5		197
	(a)	Includes an immaterial number of stock appreciation rights.
Summary of Restricted Stock Award Activity	The following is a summary of restricted stock award activity of our common stock in 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	251,351			87.64				26,725			85.9
	RS’s Vested/RSU’s Issued	(330,971	)		55.36				(578	)		51.99
	Forfeited	(29,429	)		70.29				(133	)		76.1
	Outstanding at December 31, 2014	515,073			77.23				411,093			37.3
Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity, Vested And Unvested	The following is a summary of the values related to restricted stock and restricted stock unit awards held by MPC employees and non-employee directors:
		Restricted Stock								Restricted Stock Units
		Intrinsic Value of Awards Vested During the Period (in millions)				Weighted Average Grant Date Fair Value of Awards Granted During the Period				Intrinsic Value of Awards Vested During the Period (in millions)				Weighted Average Grant Date Fair Value of Awards Granted During the Period
	2014	$	28			$	87.64			$	—			$	85.9
	2013	20				87.06				—				73.48
	2012	5				43.11				—				44.38
Schedule of Performance Unit Awards	The following table presents a summary of the 2014 activity for performance unit awards to be settled in shares:
		Number of Units			Weighted Average Grant Date Fair Value
	Outstanding at December 31, 2013	3,822,500			$	0.9
	Granted	2,033,700			0.85
	Canceled	(64,375	)		0.87
	Outstanding at December 31, 2014	5,791,825			0.88
Schedule of Share-based Compensation, Performance Unit Awards, Valuation Assumptions	Performance units paying out in units have a grant date fair value calculated using a Monte Carlo valuation model, which requires the input of subjective assumptions. The following table provides a summary of these assumptions:
		2014				2013				2012
	Risk-free interest rate	0.63		%		0.35		%		0.41		%
	Look-back period	2.84 years				2.84 years				2.84 years
	Expected volatility	38.51		%		41.67		%		56.06		%
	Grant date fair value of performance units granted	$	0.85			$	0.95			$	0.8

Leases_Tables

Leases (Tables)	12 Months Ended
	Dec. 31, 2014
Leases [Abstract]
Schedule Of Future Minimum Commitments	Future minimum commitments as of December 31, 2014, for capital lease obligations and for operating lease obligations having initial or remaining non-cancelable lease terms in excess of one year are as follows:
	(In millions)	Capital		Operating
		Lease		Lease
		Obligations		Obligations
	2015	$	52	$	249
	2016	51		209
	2017	50		150
	2018	49		136
	2019	45		114
	Later years	300		468
	Total minimum lease payments	547		$	1,326
	Less imputed interest costs	176
	Present value of net minimum lease payments	$	371
Schedule Of Operating Lease Rental Expense	Operating lease rental expense was:
	(In millions)	2014		2013		2012
	Rental expense	$	256	$	213	$	139

Selected_Quarterly_Financial_D1

Selected Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Data [Abstract]
Schedule Of Quarterly Financial Information
		2014								2013
	(In millions, except per share data)	1st Qtr.		2nd Qtr.		3rd Qtr.		4th Qtr.		1st Qtr.		2nd Qtr.		3rd Qtr.		4th Qtr.
	Revenues	$	23,285	$	26,844	$	25,438	$	22,250	$	23,330	$	25,677	$	26,256	$	24,897
	Income from operations	361		1,369		1,062		1,259		1,156		960		301		1,008
	Net income	207		864		679		805		730		599		173		631
	Net income attributable to MPC	199		855		672		798		725		593		168		626
	Net income attributable to MPC per share:
	Basic	$	0.68	$	2.97	$	2.38	$	2.88	$	2.19	$	1.84	$	0.54	$	2.09
	Diluted	0.67		2.95		2.36		2.86		2.17		1.83		0.54		2.07
	Dividends paid per share	0.42		0.42		0.5		0.5		0.35		0.35		0.42		0.42

Supplementary_Statistics_Table

Supplementary Statistics (Tables)	12 Months Ended
	Dec. 31, 2014
Text Block [Abstract]
Supplementary Statistics
	(In millions)	2014			2013			2012
	Income from Operations by segment
	Refining & Marketing	$	3,609		$	3,206		$	5,098
	Speedway	544			375			310
	Pipeline Transportation(a)	280			210			216
	Items not allocated to segments:
	Corporate and other unallocated items(a)	(286		)	(271		)	(336		)
	Minnesota Assets sale settlement gain	—			—			183
	Pension settlement expenses	(96		)	(95		)	(124		)
	Income from operations	$	4,051		$	3,425		$	5,347
	Capital Expenditures and Investments(b)(c)
	Refining & Marketing	$	1,104		$	2,094		$	705
	Speedway	2,981			296			340
	Pipeline Transportation	543			234			211
	Corporate and Other(d)	110			165			204
	Total	$	4,738		$	2,789		$	1,460
	(a)	Included in the Pipeline Transportation segment for 2014, 2013 and 2012 are $19 million, $20 million and $4 million of corporate overhead expenses attributable to MPLX, which were included in items not allocated to segments prior to MPLX’s October 31, 2012 initial public offering. Corporate overhead expenses are not currently allocated to other segments.
	(b)	Capital expenditures include changes in capital accruals.
	(c)	Includes $2.71 billion in 2014 for the acquisition of Hess’ Retail Operations and Related Assets and $1.36 billion in 2013 for the acquisition of the Galveston Bay Refinery and Related Assets. See Note 5 to the audited consolidated financial statements.
	(d)	Includes capitalized interest of $27 million, $28 million and $101 million for 2014, 2013 and 2012, respectively.
Operating Statistics
		2014			2013			2012
	MPC Consolidated Refined Product Sales Volumes (thousands of barrels per day)(a)(b)	2,138			2,086			1,618
	Refining & Marketing Operating Statistics(b)
	Refining & Marketing refined product sales volume (thousands of barrels per day)(c)	2,125			2,075			1,599
	Refining & Marketing gross margin (dollars per barrel)(d)	$	15.05		$	13.24		$	17.85
	Crude oil capacity utilization percent(e)	95			96			100
	Refinery throughputs (thousands of barrels per day):(f)
	Crude oil refined	1,622			1,589			1,195
	Other charge and blendstocks	184			213			168
	Total	1,806			1,802			1,363
	Sour crude oil throughput percent	52			53			53
	WTI-priced crude oil throughput percent	19			21			28
	Refined product yields (thousands of barrels per day):(f)
	Gasoline	869			921			738
	Distillates	580			572			433
	Propane	35			37			26
	Feedstocks and special products	276			221			109
	Heavy fuel oil	25			31			18
	Asphalt	54			54			62
	Total	1,839			1,836			1,386
	Refinery direct operating costs (dollars per barrel):(g)
	Planned turnaround and major maintenance	$	1.8		$	1.2		$	1
	Depreciation and amortization	1.41			1.36			1.44
	Other manufacturing(h)	4.86			4.14			3.15
	Total	$	8.07		$	6.7		$	5.59
	Refining & Marketing Operating Statistics By Region – Gulf Coast(b)
	Refinery throughputs (thousands of barrels per day):(i)
	Crude oil refined	991			964
	Other charge and blendstocks	182			195
	Total	1,173			1,159
	Sour crude oil throughput percent	64			65
	WTI-priced crude oil throughput percent	3			7
	Refined product yields (thousands of barrels per day):(i)
	Gasoline	508			551
	Distillates	368			365
	Propane	23			23
	Feedstocks and special products	274			215
	Heavy fuel oil	13			19
	Asphalt	13			13
	Total	1,199			1,186
	Refinery direct operating costs (dollars per barrel):(g)
	Planned turnaround and major maintenance	$	1.82		$	1
	Depreciation and amortization	1.15			1.09
	Other manufacturing(h)	4.73			3.98
	Total	$	7.7		$	6.07
	Supplementary Statistics (Unaudited)
		2014			2013			2012
	Refining & Marketing Operating Statistics By Region – Midwest
	Refinery throughputs (thousands of barrels per day):(i)
	Crude oil refined	631			625
	Other charge and blendstocks	45			54
	Total	676			679
	Sour crude oil throughput percent	33			35
	WTI-priced crude oil throughput percent	44			42
	Refined product yields (thousands of barrels per day):(i)
	Gasoline	361			371
	Distillates	212			207
	Propane	13			14
	Feedstocks and special products	43			41
	Heavy fuel oil	13			12
	Asphalt	41			41
	Total	683			686
	Refinery direct operating costs (dollars per barrel):(g)
Planned turnaround and major maintenance	$	1.66		$	1.47
Depreciation and amortization	1.78			1.74
Other manufacturing(h)	4.76			4.21
Total	$	8.2		$	7.42
Speedway Operating Statistics(j)
Convenience stores at period-end	2,746			1,478			1,464
Gasoline and distillate sales (millions of gallons)	3,942			3,146			3,027
Gasoline & distillate gross margin (dollars per gallon)(k)	$	0.1775		$	0.1441		$	0.1318
Merchandise sales (in millions)	$	3,611		$	3,135		$	3,058
Merchandise gross margin (in millions)	$	975		$	825		$	795
Merchandise gross margin percent	27		%	26.3		%	26		%
Same store gasoline sales volume (period over period)	(0.7		)%	0.5		%	(0.8		)%
Same store merchandise sales (period over period)(l)	5		%	4.3		%	7		%
Pipeline Transportation Operating Statistics
Pipeline throughputs (thousands of barrels per day):(m)
Crude oil pipelines	1,241			1,293			1,191
Refined products pipelines	878			911			980
Total	2,119			2,204			2,171
(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. Starting in the fourth quarter of 2013, direct operating costs are no longer included in the Refining & Marketing gross margin and the gross margin is calculated based on total refinery throughput. All prior periods presented have been recalculated to reflect a consistent approach.
(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 thousand barrels per day (“mbpd”), 36 mbpd and 25 mbpd for 2014, 2013 and 2012, 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)	Includes the impact of Hess’ Retail Operations and Related Assets beginning on the September 30, 2014 acquisition date.
(k)	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.
(l)	Excludes cigarettes.
(m)	On owned common-carrier pipelines, excluding equity method investments.

Description_Of_The_Business_An1

Description Of The Business And Basis Of Presentation Basis of Presentation (Details) (Increase in Prior Year Bonus Expense, Total costs and expenses, USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014
Increase in Prior Year Bonus Expense | Total costs and expenses
Quantifying misstatement in current year financial statements, amount	$29

Summary_Of_Principal_Accountin2

Summary Of Principal Accounting Policies (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Summary Of Principal Accounting Policies [Line Items]
Restricted cash and cash equivalents	4	7
Accounts receivable number of days past-due evaluated for doubtful accounts	180 days
Stock Options
Summary Of Principal Accounting Policies [Line Items]
Implied volatility rate weighting (in percentage)	50.00%
Historical volatility rate weighting (in percentage)	50.00%
Minimum
Summary Of Principal Accounting Policies [Line Items]
Number of companies engaged in crude oil or refinery feedstock trading agreement	100
Estimated useful lives (in years)	4 years
Maximum
Summary Of Principal Accounting Policies [Line Items]
Estimated useful lives (in years)	42 years
Accounts Receivable with Master Netting Arrangements | Customer Concentration Risk
Summary Of Principal Accounting Policies [Line Items]
Percentage of accounts receivable related to sales of crude oil refinery feed stocks to customers with master netting agreements	41.00%	38.00%
MPLX LP
Summary Of Principal Accounting Policies [Line Items]
MPC's partnership interest in MPLX (in percentage)	71.50%
Percentage of noncontrolling interest (in percentage)	28.50%

MPLX_LP_Narrative_Detail

MPLX LP (Narrative) (Detail) (USD $)	12 Months Ended			0 Months Ended				6 Months Ended	1 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 02, 2014	Mar. 01, 2014	1-May-13	Dec. 08, 2014	Apr. 30, 2013	Oct. 31, 2012	Dec. 01, 2014	Dec. 10, 2014
Noncontrolling Interest [Line Items]
Net proceeds from issuance of MPLX LP common units	$221	$0	$407
MPLX Pipe Line Holdings LP
Noncontrolling Interest [Line Items]
Additional interest sold					13.00%	5.00%				30.50%
Proceeds from sale of ownership interest				600	310	100
MPLX LP
Noncontrolling Interest [Line Items]
Net proceeds from issuance of MPLX LP common units							221
MPC's partnership interest in MPLX (in percentage)	71.50%
General partner units issued											130,000
General partners' contributed capital											9
MPLX LP | MPLX Revolver
Noncontrolling Interest [Line Items]
Cash paid for acquisition				600	270
MPLX LP | Cash and cash equivalents
Noncontrolling Interest [Line Items]
Cash paid for acquisition					40
MPLX LP | Butane Cavern
Noncontrolling Interest [Line Items]
MPLX's partnership percent indirect interest in assets									100.00%
MPLX LP | General Partner and Limited Partner
Noncontrolling Interest [Line Items]
MPC's partnership interest in MPLX (in percentage)	71.50%
MPLX LP | General Partner
Noncontrolling Interest [Line Items]
MPC's partnership interest in MPLX (in percentage)	2.00%
MPLX LP | Limited Partner
Noncontrolling Interest [Line Items]
Public offering of common units (in number of common units)							3,500,000
Equity interest issued, number of shares				2,900,000
Equity interest issued, value assigned										200
Shares issued, price per share							$66.68
MPLX LP | MPLX Pipe Line Holdings LP
Noncontrolling Interest [Line Items]
Ownership interest (in percentage)								51.00%
MPLX LP | IPO
Noncontrolling Interest [Line Items]
Initial public offering date of MPLX LP									Oct-12
Net proceeds from issuance of MPLX LP common units									$407
MPLX LP | IPO | Limited Partner
Noncontrolling Interest [Line Items]
Public offering of common units (in number of common units)									19,900,000

Acquisitions_and_Investments_A

Acquisitions and Investments (Acquisition of Hess' Retail Operations and Related Assets) (Details) (USD $)	0 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jun. 30, 2014
					Store
Business Acquisition [Line Items]
Goodwill		$1,566	$938	$930
Speedway
Business Acquisition [Line Items]
Goodwill		854	225	217
Number of states in which entity operates					9
Hess Retail Operations and Related Assets
Business Acquisition [Line Items]
Allocation of space on Colonial Pipeline (in barrels per day)	40,000
Cash paid for acquisition	2,824
Goodwill	629
Assured sales volume (bpd)	200,000
Other noncurrent assets	111
Deferred credits and other liabilities	155
Acquisition-related costs	14
Hess Retail Operations and Related Assets | Trade Names
Business Acquisition [Line Items]
Finite-lived intangibles	22
Finite-lived intangible asset, useful life	2 years
Hess Retail Operations and Related Assets | Favorable Leases
Business Acquisition [Line Items]
Other noncurrent assets	72
Hess Retail Operations and Related Assets | Unfavorable Leases
Business Acquisition [Line Items]
Deferred credits and other liabilities	$90
Hess Retail Operations and Related Assets | Speedway
Business Acquisition [Line Items]
Number of states in which entity operates	22

Acquisitions_and_Investments_F

Acquisitions and Investments (Fair Value of Consideration Transferred - Hess Retail) (Details) (Hess Retail Operations and Related Assets, USD $)	0 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014
Hess Retail Operations and Related Assets
Business Acquisition [Line Items]
Cash paid for acquisition	$2,824
Net working capital adjustment estimate	-3
Total fair value of consideration transferred	$2,821

Acquisitions_and_Investments_S

Acquisitions and Investments (Schedule of Assets Acquired and Liabilities Assumed - Hess Retail) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2014
In Millions, unless otherwise specified
Business Acquisition [Line Items]
Goodwill	$1,566	$938	$930
Hess Retail Operations and Related Assets
Business Acquisition [Line Items]
Cash and cash equivalents				49
Receivables				123
Inventories				165
Other current assets				8
Property, plant and equipment, net				2,063
Other noncurrent assets				111
Total assets acquired				2,519
Accounts payable				77
Payroll and benefits payable				15
Consumer excise taxes payable				64
Accrued taxes				4
Other current liabilities				10
Defined benefit postretirement plan obligations				2
Deferred credits and other liabilities				155
Total liabilities assumed				327
Net assets acquired excluding goodwill				2,192
Goodwill				629
Net assets acquired				$2,821

Acquisitions_and_Investments_R

Acquisitions and Investments (Revenues and Earnings of Hess Retail Included in Consolidated Statement of Operations) (Details) (Hess Retail Operations and Related Assets, USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014
Hess Retail Operations and Related Assets
Business Acquisition [Line Items]
Sales and other operating revenues (including consumer excise taxes)	$2,403
Income from operations	$113

Acquisitions_and_Investments_A1

Acquisitions and Investments (Acquisition of Refinery and Related Logistics and Marketing Assets) (Detail) (USD $)	9 Months Ended	12 Months Ended			1 Months Ended
	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 01, 2013
					Pipeline
					site
					Terminal
					BPCD
					MW
Business Acquisition [Line Items]
Contingent consideration payment	$172,000,000	$172,000,000	$0	$0
Galveston Bay Refinery and Related Assets
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		180,000,000			1,491,000,000
Inventories					935,000,000
Maximum earnout provision payable to the company		520,000,000	700,000,000		700,000,000
Term of payment of maximum earnout provision payable to the company, years					6 years
Post-closing adjustment					9,000,000
Finite-lived intangible assets, weighted average useful life					13 years
Acquisition related costs					7,000,000
Galveston Bay Refinery and Related Assets | Customer Relationships
Business Acquisition [Line Items]
Finite-lived intangibles					20,000,000
Finite-lived intangible asset, useful life					4 years
Galveston Bay Refinery and Related Assets | Prepaid Licensed Refinery Technology Agreements
Business Acquisition [Line Items]
Finite-lived intangibles					$68,000,000
Finite-lived intangible asset, useful life					15 years

Acquisitions_and_Investments_F1

Acquisitions and Investments (Fair Value of Consideration Transferred - Galveston Bay) (Details) (USD $)	12 Months Ended				1 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013		Dec. 31, 2012	Feb. 01, 2013
Business Acquisition [Line Items]
Fair value of contingent consideration as of acquisition date	$0	$600	[1]	$0
Payable to seller	0	6	[1]	0
Galveston Bay Refinery and Related Assets
Business Acquisition [Line Items]
Cash paid for acquisition	180				1,491
Fair value of contingent consideration as of acquisition date					600
Payable to seller					6
Post-closing adjustment					-9
Total fair value of consideration transferred					$2,088
[1]	See Note 5.

Acquisitions_and_Investments_S1

Acquisitions and Investments (Schedule of Assets Acquired and Liabilities Assumed - Galveston Bay) (Details) (Galveston Bay Refinery and Related Assets, USD $)	Feb. 01, 2013
In Millions, unless otherwise specified
Galveston Bay Refinery and Related Assets
Business Acquisition [Line Items]
Inventories	$935
Other current assets	1
Property, plant and equipment, net	1,274
Other noncurrent assets	88
Total assets acquired	2,298
Accounts payable	12
Payroll and benefits payable	14
Long-term debt due within one year	2	[1]
Other current liabilities	6
Long-term debt	58	[1]
Defined benefit postretirement plan obligations	43
Deferred credits and other liabilities	75
Total liabilities assumed	210
Net assets acquired excluding goodwill	$2,088
[1]	Represents a capital lease obligation assumed.

Acquisitions_and_Investments_S2

Acquisitions and Investments (Schedule of Acquisition Related Pro Forma Financial Information (Details) (USD $)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Business Combinations [Abstract]
Sales and other operating revenues (including consumer excise taxes)	$106,482	$114,148
Net income attributable to MPC	$2,547	$2,142
Net income attributable to MPC per share – basic	$8.94	$6.80
Net income attributable to MPC per share – diluted	$8.87	$6.76

Acquisitions_and_Investments_A2

Acquisitions and Investments (Acquisitions of Convenience Stores) (Details) (USD $)	1 Months Ended				12 Months Ended
In Millions, unless otherwise specified	Jul. 31, 2012		31-May-12		Dec. 31, 2014		Dec. 31, 2013
	Store		Parcels				Store
			Store
Business Acquisition [Line Items]
Goodwill acquired during period					$629	[1]	$8	[1]
Speedway
Business Acquisition [Line Items]
Number of convenience stores acquired	10		87				9
Goodwill acquired during period	$5	[1]	$83	[1]	$629	[1]	$8	[1]
Number of undeveloped real estate parcels acquired for future development			2
[1]	See Note 5 for information on the acquisitions.

Acquisitions_and_Investments_A3

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

Acquisitions_and_Investments_I

Acquisitions and Investments (Investments in Ethanol Companies) (Details) (USD $)	1 Months Ended
In Millions, unless otherwise specified	Aug. 01, 2013	Dec. 31, 2014
	Company
TACE
Business Acquisition [Line Items]
Equity method investments, ownership percentage		60.00%
TAEI
Business Acquisition [Line Items]
Equity method investments, ownership percentage		34.00%
TAME
Business Acquisition [Line Items]
Equity method investments, ownership percentage		67.00%
TAME | TAEI
Business Acquisition [Line Items]
Equity method investments, ownership percentage		50.00%
TAAE
Business Acquisition [Line Items]
Equity method investments, ownership percentage		43.00%
Ethanol Interests From Mitsui
Business Acquisition [Line Items]
Number of businesses in which ownership interests acquired	3
Cash paid to acquire equity method investments	$75
Ethanol Interests From Mitsui | TACE
Business Acquisition [Line Items]
Ownership percentage acquired	24.00%
Ethanol Interests From Mitsui | TAEI
Business Acquisition [Line Items]
Ownership percentage acquired	34.00%
Ethanol Interests From Mitsui | TAAE
Business Acquisition [Line Items]
Ownership percentage acquired	40.00%

Acquisitions_and_Investments_I1

Acquisitions and Investments (Investment in Pipeline Companies) (Details) (USD $)	12 Months Ended	0 Months Ended	15 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Mar. 04, 2014	Dec. 31, 2014	Jul. 01, 2014	Jan. 01, 2017
Illinois Extension Pipeline Company LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	35.00%		35.00%	35.00%
Cash paid to acquire equity method investments	$120
Explorer
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	25.00%		25.00%
Cash paid to acquire equity method investments		77
Ownership percentage acquired		7.00%
North Dakota Pipeline
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	37.50%		37.50%
Cash paid to acquire equity method investments	$192		$216
North Dakota Pipeline Class A Units | Scenario, Forecast
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage					27.00%
North Dakota Pipeline Class A Units | Scenario, Forecast | Maximum
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage					30.00%

Disposition_Detail

Disposition (Detail) (USD $)	12 Months Ended				1 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012		Jul. 31, 2012	Dec. 01, 2010
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Buyer redeemed preferred equity interest	$27	$16	$53
Preferred equity interest	0	0	45	[1]
Minnesota Assets
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Refinery capacity (in barrels per calendar day)						74,000
Minnesota Assets | Variable Interest Entity
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Buyer redeemed preferred equity interest		49			80
Cash proceeds, dividends on preferred equity interest		4			12
Cash proceeds, distribution from VIE's offering					40
Cash proceeds, total					132
Preferred equity interest					45
Income before income taxes recognized by the company as a result of the Minnesota Assets' successful IPO			183
Disposal group, amortization of deferred gain on disposal			$86
Super America
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Convenience stores						166
Wisconsin
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Convenience stores						6
[1]	See Note 6.

Variable_Interest_Entity_Varia

Variable Interest Entity Variable Interest Entity (Details) (Illinois Extension Pipeline Company LLC, Variable Interest Entity, Not Primary Beneficiary, USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Illinois Extension Pipeline Company LLC | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
VIE, maximum loss exposure, amount	$120

Related_Party_Transactions_Nar

Related Party Transactions (Narrative) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Centennial
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	50.00%
Operating pipeline revenue from related parties included in other income	$1	$1	$1
Long-term receivable from related party	$1	$2
Explorer
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	25.00%
LOCAP
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	59.00%
LOOP
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	51.00%
TAAE
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	43.00%
TACE
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	60.00%
TAME
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	67.00%

Related_Party_Transactions_Sal

Related Party Transactions (Sales To Related Parties) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Related Party Transaction [Line Items]
Sales to related parties	$7	$8	$8
Centennial
Related Party Transaction [Line Items]
Sales to related parties	0	0	1
Other equity method investees
Related Party Transaction [Line Items]
Sales to related parties	$7	$8	$7

Related_Party_Transactions_Pur

Related Party Transactions (Purchases From Related Parties) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Related Party Transaction [Line Items]
Purchases from related parties	$505	$357	$280
Centennial
Related Party Transaction [Line Items]
Purchases from related parties	7	3	7
Explorer
Related Party Transaction [Line Items]
Purchases from related parties	39	0	0
LOCAP
Related Party Transaction [Line Items]
Purchases from related parties	21	17	24
LOOP
Related Party Transaction [Line Items]
Purchases from related parties	88	43	44
TAAE
Related Party Transaction [Line Items]
Purchases from related parties	79	24	0
TACE
Related Party Transaction [Line Items]
Purchases from related parties	121	130	73
TAME
Related Party Transaction [Line Items]
Purchases from related parties	141	131	124
Other equity method investees
Related Party Transaction [Line Items]
Purchases from related parties	$9	$9	$8

Related_Party_Transactions_Rec

Related Party Transactions (Receivables From Related Parties) (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Related Party Transaction [Line Items]
Current receivables from related parties	$7	$2
Centennial
Related Party Transaction [Line Items]
Current receivables from related parties	2	1
Explorer
Related Party Transaction [Line Items]
Current receivables from related parties	2	0
TAME
Related Party Transaction [Line Items]
Current receivables from related parties	$3	$1

Related_Party_Transactions_Pay

Related Party Transactions (Payables To Related Parties) (Detail) (USD $)	Dec. 31, 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	2	2
LOOP
Related Party Transaction [Line Items]
Payables to related parties	4	3
TAAE
Related Party Transaction [Line Items]
Payables to related parties	2	2
TACE
Related Party Transaction [Line Items]
Payables to related parties	2	4
TAME
Related Party Transaction [Line Items]
Payables to related parties	$5	$5

Income_per_Common_Share_Summar

Income per Common Share (Summary Of Earnings Per Common Share) (Detail) (USD $)	3 Months Ended								12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Basic earnings per share:
Net income attributable to MPC	$798	$672	$855	$199	$626	$168	$593	$725	$2,524	$2,112	$3,389
Income allocated to participating securities, basic									4	4	6
Income available to common stockholders – basic									2,520	2,108	3,383
Weighted average common shares outstanding (in shares)									285	315	340
Basic (in USD per share)	$2.88	$2.38	$2.97	$0.68	$2.09	$0.54	$1.84	$2.19	$8.84	$6.69	$9.95
Diluted earnings per share:
Net income attributable to MPC	798	672	855	199	626	168	593	725	2,524	2,112	3,389
Income allocated to participating securities, diluted									4	4	6
Income available to common stockholders – diluted									$2,520	$2,108	$3,383
Weighted average common shares outstanding (in shares)									285	315	340
Effect of dilutive securities (in shares)									2	2	2
Weighted average common shares, including dilutive effect (in shares)									287	317	342
Diluted (in USD per share)	$2.86	$2.36	$2.95	$0.67	$2.07	$0.54	$1.83	$2.17	$8.78	$6.64	$9.89

Income_per_Common_Share_Income

Income per Common Share Income Per Common Share (Anti-dilutive Shares) (Detail) (Shares issued under stock-based compensation plans)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
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	0	2

Equity_Narrative_Detail

Equity (Narrative) (Detail) (USD $)	12 Months Ended				36 Months Ended	1 Months Ended	0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2014	Jan. 31, 2015	Jul. 30, 2014	Feb. 28, 2012	Nov. 30, 2012
Stockholders Equity [Line Items]
Stock repurchase plan authorized amount	$8,000,000,000				$8,000,000,000
Cash paid for shares repurchased	2,131,000,000	2,793,000,000		1,350,000,000	6,270,000,000
Stock repurchase plan remaining authorized amount	1,730,000,000				1,730,000,000
Number of shares repurchased	24,000,000	37,000,000	[1]	28,000,000	89,000,000
Effective average cost per delivered share	$88.63	$76.14		$46.73	$70.35
Scenario, Forecast
Stockholders Equity [Line Items]
Cash paid for shares repurchased						9,000,000
Number of shares repurchased						99,084
Share Repurchase Authorization July 2014
Stockholders Equity [Line Items]
Stock repurchase plan authorized amount							2,000,000,000
Ending date of share repurchase authorization							30-Jul-16
Accelerated Share Repurchase Program February 2012
Stockholders Equity [Line Items]
Repurchase shares of MPC common stock under ASR program								850,000,000
Accelerated Share Repurchase Program November 2012
Stockholders Equity [Line Items]
Number of shares repurchased		1,000,000
Repurchase shares of MPC common stock under ASR program									$500,000,000
[1]	Shares repurchased in 2013 includes 1 million shares received under the November 2012 ASR program, which were paid for in 2012.

Equity_Share_Repurchases_Detai

Equity (Share Repurchases) (Details) (USD $)	12 Months Ended				36 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2014
Stockholders Equity [Line Items]
Number of shares repurchased	24,000,000	37,000,000	[1]	28,000,000	89,000,000
Cash paid for shares repurchased	$2,131	$2,793		$1,350	$6,270
Effective average cost per delivered share	$88.63	$76.14		$46.73	$70.35
Accelerated Share Repurchase Program November 2012
Stockholders Equity [Line Items]
Number of shares repurchased		1,000,000
[1]	Shares repurchased in 2013 includes 1 million shares received under the November 2012 ASR program, which were paid for in 2012.

Segment_Information_Narrative_

Segment Information (Narrative) (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2012	Dec. 31, 2013
	Segment
Segment Reporting Information [Line Items]
Number of reportable segments	3
None | Maximum
Segment Reporting Information [Line Items]
Percent of annual revenues		10.00%	10.00%
BP plc
Segment Reporting Information [Line Items]
Percent of annual revenues				10.00%

Segment_Information_Income_Fro

Segment Information (Income From Operations Attributable To Operating Segments) (Detail) (USD $)	3 Months Ended								12 Months Ended						0 Months Ended	1 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012		Sep. 30, 2014	Feb. 01, 2013
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)									$97,817		$100,160		$82,243
Income from operations	1,259	1,062	1,369	361	1,008	301	960	1,156	4,051		3,425		5,347
Income (loss) from equity method investments									153		36		26
Depreciation and amortization									1,326		1,220		995
Segment capital expenditures and investments									4,738	[1],[2]	2,789	[1],[2]	1,460	[1],[2]
Hess Retail Operations and Related Assets
Segment Reporting Information [Line Items]
Segment capital expenditures and investments									2,710
Galveston Bay Refinery and Related Assets
Segment Reporting Information [Line Items]
Segment capital expenditures and investments											1,360
Refining & Marketing
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)									80,822		85,616		67,928
Speedway
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)									16,927		14,471		14,239
Pipeline Transportation
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)									70		79		78
Reportable Segment
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)									97,819		100,166		82,245
Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)									11,444	[3]	9,756	[3]	9,167	[3]
Intersegment Eliminations | Refining & Marketing
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)									10,912	[3]	9,294	[3]	8,782	[3]
Intersegment Eliminations | Speedway
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)									5	[3]	4	[3]	4	[3]
Intersegment Eliminations | Pipeline Transportation
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)									527	[3]	458	[3]	381	[3]
Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)									109,263		109,922		91,412
Income from operations									4,433	[4]	3,791	[4]	5,624	[4]
Income (loss) from equity method investments									153		36		26
Depreciation and amortization									1,274	[5]	1,197	[5]	972	[5]
Segment capital expenditures and investments									4,628	[6],[7]	2,624	[6],[8]	1,256	[6]
Operating Segments | Refining & Marketing
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)									91,734		94,910		76,710
Income from operations									3,609	[4]	3,206	[4]	5,098	[4]
Income (loss) from equity method investments									96		28		-6
Depreciation and amortization									1,045	[5]	1,011	[5]	804	[5]
Segment capital expenditures and investments									1,104	[6],[7]	2,094	[6],[8]	705	[6]
Operating Segments | Refining & Marketing | Hess Retail Operations and Related Assets
Segment Reporting Information [Line Items]
Segment capital expenditures and investments															52
Operating Segments | Refining & Marketing | Galveston Bay Refinery and Related Assets
Segment Reporting Information [Line Items]
Segment capital expenditures and investments																1,290
Operating Segments | Speedway
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)									16,932		14,475		14,243
Income from operations									544	[4]	375	[4]	310	[4]
Income (loss) from equity method investments									0		0		0
Depreciation and amortization									152	[5]	112	[5]	114	[5]
Segment capital expenditures and investments									2,981	[6],[7]	296	[6],[8]	340	[6]
Operating Segments | Speedway | Hess Retail Operations and Related Assets
Segment Reporting Information [Line Items]
Segment capital expenditures and investments															2,660
Operating Segments | Pipeline Transportation
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)									597		537		459
Income from operations									280	[4]	210	[4]	216	[4]
Income (loss) from equity method investments									57		8		32
Depreciation and amortization									77	[5]	74	[5]	54	[5]
Segment capital expenditures and investments									543	[6],[7]	234	[6],[8]	211	[6]
Operating Segments | Pipeline Transportation | Galveston Bay Refinery and Related Assets
Segment Reporting Information [Line Items]
Segment capital expenditures and investments																70
Operating Segments | Pipeline Transportation | MPLX LP
Segment Reporting Information [Line Items]
Cost of services, overhead									$19		$20		$4
[1]	Capital expenditures include changes in capital accruals.
[2]	Includes $2.71 billion in 2014 for the acquisition of Hess’ Retail Operations and Related Assets and $1.36 billion in 2013 for the acquisition of the Galveston Bay Refinery and Related Assets. See Note 5 to the audited consolidated financial statements.
[3]	Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties.
[4]	Included in the Pipeline Transportation segment for 2014, 2013 and 2012 are $19 million, $20 million and $4 million of corporate overhead expenses attributable to MPLX, which were included in items not allocated to segments prior to MPLX’s October 31, 2012 initial public offering. Corporate overhead expenses are not currently allocated to other segments.
[5]	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.
[6]	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
[7]	The Speedway and Refining & Marketing segments include $2.66 billion and $52 million, respectively, for the acquisition of Hess’ Retail Operations and Related Assets. See Note 5.
[8]	The Refining & Marketing and Pipeline Transportation segments include $1.29 billion and $70 million, respectively, for the acquisition of the Galveston Bay Refinery and Related Assets. See Note 5.

Segment_Information_Reconcilia

Segment Information (Reconciliation Of Segment Income From Operations To Income Before Income Taxes) (Detail) (USD $)

3 Months Ended

12 Months Ended

In Millions, unless otherwise specified

Dec. 31, 2014

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]

Income from operations

$1,259

$1,062

$1,369

$361

$1,008

$301

$960

$1,156

$4,051

$3,425

$5,347

Minnesota Assets sale settlement gain

21

6

177

Net interest and other financial income (costs)

216

179

109

Income before income taxes

3,835

3,246

5,238

Operating Segments

Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]

Income from operations

4,433

[1]

3,791

[1]

5,624

[1]

Corporate and Other

Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]

Income from operations

-286

[2],[3]

-271

[2],[3]

-336

[2],[3]

Segment Reconciling Items

Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]

Minnesota Assets sale settlement gain

0

[4]

0

[4]

183

[4]

Pension settlement expenses

($96)

[5]

($95)

[5]

($124)

[5]

[1]

Included in the Pipeline Transportation segment for 2014, 2013 and 2012 are $19 million, $20 million and $4 million of corporate overhead expenses attributable to MPLX, which were included in items not allocated to segments prior to MPLX’s October 31, 2012 initial public offering. Corporate overhead expenses are not currently allocated to other segments.

[2]

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

[3]

Corporate overhead expenses attributable to MPLX were included in the Pipeline Transportation segment subsequent to MPLX’s October 31, 2012 initial public offering. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments.

[4]

See Note 6.

[5]

See Note 23.

Segment_Information_Reconcilia1

Segment Information (Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Segment Reporting, Other Significant Reconciling Item [Line Items]
Segment capital expenditures and investments	$4,738	[1],[2]	$2,789	[1],[2]	$1,460	[1],[2]
Plus: Items not allocated to segments:
Total capital expenditures	4,325	[1],[3]	2,665	[1],[3]	1,432	[1],[3]
Operating Segments
Segment Reporting, Other Significant Reconciling Item [Line Items]
Segment capital expenditures and investments	4,628	[4],[5]	2,624	[4],[6]	1,256	[4]
Less: Investments in equity method investees	413		124		28
Corporate and Other
Segment Reporting, Other Significant Reconciling Item [Line Items]
Segment capital expenditures and investments	110	[7]	165	[7]	204	[7]
Plus: Items not allocated to segments:
Capital expenditures not allocated to segments	83		137		103
Capitalized interest	$27		$28		$101
[1]	Capital expenditures include changes in capital accruals.
[2]	Includes $2.71 billion in 2014 for the acquisition of Hess’ Retail Operations and Related Assets and $1.36 billion in 2013 for the acquisition of the Galveston Bay Refinery and Related Assets. See Note 5 to the audited consolidated financial statements.
[3]	See Note 21 for a reconciliation of total capital expenditures to additions to property, plant and equipment as reported in the consolidated statements of cash flows.
[4]	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
[5]	The Speedway and Refining & Marketing segments include $2.66 billion and $52 million, respectively, for the acquisition of Hess’ Retail Operations and Related Assets. See Note 5.
[6]	The Refining & Marketing and Pipeline Transportation segments include $1.29 billion and $70 million, respectively, for the acquisition of the Galveston Bay Refinery and Related Assets. See Note 5.
[7]	Includes capitalized interest of $27 million, $28 million and $101 million for 2014, 2013 and 2012, respectively.

Segment_Information_Reconcilia2

Segment Information (Reconciliation Of Total Revenues To Sales And Other Operating Revenues) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting, Revenue Reconciling Item [Line Items]
Sales and other operating revenues (including consumer excise taxes)	$97,817	$100,160	$82,243
Corporate and Other
Segment Reporting, Revenue Reconciling Item [Line Items]
Sales and other operating revenues (including consumer excise taxes)	-2	-6	-2
Reportable Segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Sales and other operating revenues (including consumer excise taxes)	$97,819	$100,166	$82,245

Segment_Information_Schedule_O

Segment Information (Schedule Of Revenues By Product Line) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)	$97,817	$100,160	$82,243
Refined products
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)	90,702	93,520	76,234
Merchandise
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)	3,817	3,308	3,229
Crude oil and refinery feedstocks
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)	2,917	2,988	2,514
Transportation and other
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)	$381	$344	$266

Segment_Information_Total_Asse

Segment Information (Total Assets By Reportable Segment) (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Segment Reporting, Asset Reconciling Item [Line Items]
Total consolidated assets	$30,460	$28,385
Operating Segments | Refining & Marketing
Segment Reporting, Asset Reconciling Item [Line Items]
Total consolidated assets	19,751	19,573
Operating Segments | Speedway
Segment Reporting, Asset Reconciling Item [Line Items]
Total consolidated assets	5,296	2,064
Operating Segments | Pipeline Transportation
Segment Reporting, Asset Reconciling Item [Line Items]
Total consolidated assets	2,407	1,947
Corporate and Other
Segment Reporting, Asset Reconciling Item [Line Items]
Total consolidated assets	$3,006	$4,801

Other_Items_Net_Interest_And_O

Other Items (Net Interest And Other Financial Income (Costs)) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Other Income and Expenses [Abstract]
Interest income	$7	$9	$6
Interest expense	-229	-195	-191
Interest capitalized	27	28	101
Other financial costs	-21	-21	-25
Net interest and other financial income (costs)	($216)	($179)	($109)

Income_Taxes_Components_Of_Inc

Income Taxes (Components Of Income Tax Provisions (Benefits)) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current
Federal	$1,382	$954	$1,185
State and local	135	131	169
Foreign	5	5	-1
Total	1,522	1,090	1,353
Deferred
Federal	-199	20	432
State and local	-37	8	57
Foreign	-6	-5	3
Total	-242	23	492
Total
Federal	1,183	974	1,617
State and local	98	139	226
Foreign	-1		2
Total	$1,280	$1,113	$1,845

Income_Taxes_Narrative_Detail

Income Taxes (Narrative) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Statutory rate applied to income before income taxes	35.00%	35.00%	35.00%
Valuation allowance	$4	$3
Tax credit carryforward, valuation allowance	3	3
Operating loss carryforwards, valuation allowance	1
Unrecognized tax benefits, increase (decrease)		-21
Tax settlement with Marathon Oil Corporation		39
Unrecognized tax benefits that would impact effective income tax rate	5
Uncertain tax positions, reasonably possible increase or decrease during the next twelve months	4
Unrecognized tax benefits income tax net penalties and interest receipts (expenses)	1	-11	1
Interest and penalties accrued	$14	$15

Income_Taxes_Income_Taxes_Tax_

Income Taxes Income Taxes (Tax Carryforwards) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014
States
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	1
Felda Iffco Sdn Bhd | United States Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	11
Minimum | United States Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, expiration date	1-Jan-22
Minimum | States
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, expiration date	1-Jan-15
Maximum | United States Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, expiration date	31-Dec-34
Maximum | States
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, expiration date	31-Dec-29

Income_Taxes_Reconciliation_Of

Income Taxes (Reconciliation Of Federal Statutory Income Tax Rate) (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Statutory rate applied to income before income taxes	35.00%	35.00%	35.00%
State and local income taxes, net of federal income tax effects	2.00%	3.00%	2.00%
Domestic manufacturing deduction	-2.00%	-2.00%	-1.00%
Other	-2.00%	-2.00%	-1.00%
Provision for income taxes	33.00%	34.00%	35.00%

Income_Taxes_Components_Of_Def

Income Taxes (Components Of Deferred Tax Assets And Liabilities) (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Deferred tax assets:
Employee benefits	$616	$483
Environmental	54	37
Investments in subsidiaries and affiliates	24	0
Other	70	49
Total deferred tax assets	764	569
Deferred tax liabilities:
Property, plant and equipment	2,411	2,290
Inventories	614	614
Investments in subsidiaries and affiliates	0	267
Other	101	70
Total deferred tax liabilities	3,126	3,241
Net deferred tax liabilities	$2,362	$2,672

Income_Taxes_Components_Of_Net

Income Taxes (Components Of Net Deferred Tax Liabilities Classified In Consolidated Balance Sheets (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Assets
Other noncurrent assets	$7	$2
Liabilities
Accrued taxes	355	370
Deferred income taxes	2,014	2,304
Net deferred tax liabilities	$2,362	$2,672

Income_Taxes_Summary_Of_Income

Income Taxes (Summary Of Income Tax Returns Subject To Examination) (Detail)	12 Months Ended
	Dec. 31, 2014
United States Federal | Minimum
Income Tax Examination [Line Items]
Tax years	2010
United States Federal | Maximum
Income Tax Examination [Line Items]
Tax years	2013
States | Minimum
Income Tax Examination [Line Items]
Tax years	2004
States | Maximum
Income Tax Examination [Line Items]
Tax years	2013

Income_Taxes_Summary_Of_Activi

Income Taxes (Summary Of Activity In Unrecognized Tax Benefits) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
January 1 balance	$13	$40	$20
Additions for tax positions of prior years	7	30	32
Reductions for tax positions of prior years	-10	-25	-6
Settlements	2	-30	-6
Statute of limitations	0	-2	0
December 31 balance	$12	$13	$40

Inventories_Summary_Of_Invento

Inventories (Summary Of Inventories) (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Inventory Disclosure [Abstract]
Crude oil and refinery feedstocks	$2,219	$1,797
Refined products	2,955	2,367
Materials and supplies	302	425
Merchandise	166	100
Total (at cost)	$5,642	$4,689

Inventories_Narrative_Detail

Inventories (Narrative) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Inventory Disclosure [Abstract]
Total inventory LIFO percentage	94.00%	90.00%
Excess of current acquisition costs over stated LIFO value	$684	$4,084
Impact on revenues and costs as a result of LIFO liquidations	$0	$0	$0

Equity_Method_Investments_Sche

Equity Method Investments (Schedule Of Equity Method Investments) (Detail) (USD $)	Dec. 31, 2014		Dec. 31, 2013	Jul. 01, 2014	Jan. 01, 2017
In Millions, unless otherwise specified
Schedule of Equity Method Investments [Line Items]
Equity method investments	$865		$463
Centennial
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	50.00%
Equity method investments	36		29
Explorer
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	25.00%
Equity method investments	95		0
Illinois Extension Pipeline Company LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	35.00%			35.00%
Equity method investments	120		0
LOCAP
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	59.00%
Equity method investments	23		24
LOOP
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	51.00%
Equity method investments	230		214
North Dakota Pipeline Class B Units
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	38.00%	[1]
Equity method investments	216	[1]	24
TAAE
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	43.00%
Equity method investments	22		29
TACE
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	60.00%
Equity method investments	61		70
TAEI
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	34.00%
Equity method investments	19		23
TAME
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	67.00%
Equity method investments	24	[2]	35
TAME | Direct Ownership Interest
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	50.00%	[2]
Other equity method investees
Schedule of Equity Method Investments [Line Items]
Equity method investments	$19		$15
North Dakota Pipeline Class A Units | Scenario, Forecast
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage					27.00%
[1]	We own a 38 percent interest in the Class B units of this entity. Our Class B units will be converted to an approximate 27 percent ownership interest in the Class A units of this entity upon completion of the Sandpiper pipeline construction project, which is expected to be in 2017.
[2]	Excludes TAEI’s investment in TAME.

Equity_Method_Investments_Summ

Equity Method Investments (Summarized Financial Information For Equity Method Investees) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income statement data:
Revenues and other income	$1,430	$1,067	$1,025
Income from operations	379	87	73
Net income	316	63	47
Balance sheet data – December 31:
Current assets	990	339
Noncurrent assets	2,166	1,238
Current liabilities	280	145
Noncurrent liabilities	$957	$618

Equity_Method_Investments_Narr

Equity Method Investments (Narrative) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Equity method investment difference between carrying amount and underlying equity	$110
Equity method investment difference between carrying amount and underlying equity, portion related to goodwill which is not being amortized	55
Equity method investments	865	463
Dividends and partnership distributions received from equity method investees	170	18	37
Centennial
Schedule of Equity Method Investments [Line Items]
Equity method investments	36	29
Percent of debt outstanding	50.00%
Master Shelf Agreement | Financial Guarantee | Centennial
Schedule of Equity Method Investments [Line Items]
Maximum potential undiscounted payments	$38

Property_Plant_And_Equipment_S

Property, Plant And Equipment (Summary Of Property, Plant And Equipment) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	25,302	$21,793
Less accumulated depreciation	9,041	7,872
Net property, plant and equipment	16,261	13,921
Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	4 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	42 years
Operating Segments | Refining & Marketing
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	18,001	16,982
Operating Segments | Refining & Marketing | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	4 years
Operating Segments | Refining & Marketing | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	25 years
Operating Segments | Speedway
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	4,639	2,344
Operating Segments | Speedway | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	4 years
Operating Segments | Speedway | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	25 years
Operating Segments | Pipeline Transportation
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,044	1,921
Operating Segments | Pipeline Transportation | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	16 years
Operating Segments | Pipeline Transportation | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	42 years
Corporate and Other
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	618	$546
Corporate and Other | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	4 years
Corporate and Other | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	40 years

Property_Plant_And_Equipment_N

Property, Plant And Equipment (Narrative) (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015
In Millions, unless otherwise specified
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$25,302	$21,793
Property, plant and equipment, accumulated depreciation	9,041	7,872
Assets Held Under Capital Leases
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	510	510
Property, plant and equipment, accumulated depreciation	144	111
Construction In Progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,043	747
Residual Fuel Hydrocracker - Garyville | Construction In Progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	90
Residual Fuel Hydrocracker - Garyville | Scenario, Forecast | Minimum | Construction In Progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross			2,200
Residual Fuel Hydrocracker - Garyville | Scenario, Forecast | Maximum | Construction In Progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross			$2,500

Goodwill_Narrative_Detail

Goodwill (Narrative) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Goodwill and Intangible Assets Disclosure [Abstract]
Amount of required impairment	$0	$0

Goodwill_Changes_In_Carrying_A

Goodwill (Changes In Carrying Amount Of Goodwill) (Detail) (USD $)	1 Months Ended				12 Months Ended
In Millions, unless otherwise specified	Jul. 31, 2012		31-May-12		Dec. 31, 2014		Dec. 31, 2013
Goodwill [Line Items]
Beginning balance					$938		$930
Goodwill acquired during period					629	[1]	8	[1]
Goodwill, disposition					-1
Ending balance					1,566		938
Refining & Marketing
Goodwill [Line Items]
Beginning balance					551		551
Goodwill acquired during period					0		0
Goodwill, disposition					-1
Ending balance					550		551
Speedway
Goodwill [Line Items]
Beginning balance					225		217
Goodwill acquired during period	5	[1]	83	[1]	629	[1]	8	[1]
Goodwill, disposition					0
Ending balance					854		225
Pipeline Transportation
Goodwill [Line Items]
Beginning balance					162		162
Goodwill acquired during period					0		0
Goodwill, disposition					0
Ending balance					$162		$162
[1]	See Note 5 for information on the acquisitions.

Fair_Value_Measurements_Assets

Fair Value Measurements (Assets And Liabilities Accounted For At Fair Value On Recurring Basis) (Detail) (USD $)	Dec. 31, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash collateral netted with derivative assets	$78
Cash collateral netted with derivative liabilities			32
Contingent consideration, current	174		159
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - collateral and netting	-258	[1]	-21	[1]
Commodity derivative instruments, assets - net	59	[2]	0	[2]
Commodity derivative instruments, assets - collateral pledged not offset	0		61
Other assets	2		2
Total assets at fair value	61		2
Commodity derivative instruments, liabilities - netting and collateral	-180	[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	478	[3]	625	[3]
Total liabilities at fair value	478		625
Level 1 | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - gross	317		21
Other assets	2		2
Total assets at fair value	319		23
Commodity derivative instruments, liabilities - gross	180		53
Contingent consideration, liability	0		0
Total liabilities at fair value	180		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	478	[3]	625	[3]
Total liabilities at fair value	$478		$625
[1]	Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of December 31, 2014, cash collateral of $78 million was netted with mark-to-market derivative assets. As of December 31, 2013, cash collateral of $32 million 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 $174 million at December 31, 2014 and $159 million at December 31, 2013 classified as current.

Fair_Value_Measurements_Narrat

Fair Value Measurements (Narrative) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 01, 2013
Fair Value, Measurements, Recurring | Derivative
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized losses included in net income	$0	$0	$0
Fair Value, Measurements, Recurring | Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized losses included in net income	33,000,000	25,000,000
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other noncurrent assets, impairment	11,000,000	0
Impairment charge	0	8,000,000	0
Fair Value, Measurements, Nonrecurring | Centennial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other noncurrent assets, impairment			14,000,000
Galveston Bay Refinery and Related Assets
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
Maximum earnout provision payable to the company	$520,000,000	$700,000,000		$700,000,000
Galveston Bay Refinery and Related Assets | Fair Value, Measurements, Recurring | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range of internal and external crack spread forecast per barrel	13
Discount rate	5.00%
Galveston Bay Refinery and Related Assets | Fair Value, Measurements, Recurring | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range of internal and external crack spread forecast per barrel	15
Discount rate	10.00%

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 $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair Value Disclosures [Abstract]
Beginning balance	$625	$0	$0
Contingent consideration agreement	0	600	0
Contingent consideration payment	-180	0	0
Unrealized and realized losses included in net income	33	25	2
Settlements of derivative instruments	0	0	-2
Ending balance	$478	$625	$0

Fair_Value_Measurements_Assets1

Fair Value Measurements (Assets Measured At Fair Value On Nonrecurring Basis) (Detail) (Fair Value, Measurements, Nonrecurring, USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, plant and equipment, net, fair value	$0	$1	$0
Property, plant and equipment, net, impairment	0	8	0
Other noncurrent assets, fair value	0	0	0
Other noncurrent assets, impairment	11	0
Centennial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other noncurrent assets, impairment			$14

Fair_Value_Measurements_Financ

Fair Value Measurements (Financial Instruments At Fair Value, Excluding Derivative Financial Instruments) (Detail) (USD $)	Dec. 31, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
Fair Value
Financial assets:
Investments	$26		$336
Other	32		31
Total financial assets	58		367
Financial liabilities:
Long-term debt	6,571	[1]	3,306	[1]
Deferred credits and other liabilities	17		21
Total financial liabilities	6,588		3,327
Carrying Value
Financial assets:
Investments	2		14
Other	32		30
Total financial assets	34		44
Financial liabilities:
Long-term debt	6,265	[1]	3,001	[1]
Deferred credits and other liabilities	17		21
Total financial liabilities	$6,282		$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 $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Commodity derivatives | Other current assets
Derivatives, Fair Value [Line Items]
Asset	$317	$21
Liability	$180	$53

Derivatives_Narrative_Detail

Derivatives (Narrative) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2012
Notes Payable And Other Payables | 3.500% senior notes due March 1, 2016
Derivative [Line Items]
Debt instrument, interest rate (in percentage)	3.50%
Maturity period of senior notes	Mar-16
Interest Rate Swap
Derivative [Line Items]
Notional amount of interest rate swap agreements	500
Hedge agreements	3.50 percent senior notes due in March 2016
Deferred gain on discontinuation of interest rate fair value hedge	20
Hedge ineffectiveness of interest rate swaps	0

Derivatives_Pretax_Effect_Of_D

Derivatives (Pretax Effect Of Derivative Instruments Designated As Accounting Hedges Of Fair Value) (Detail) (Net interest and other financial income (costs), USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2012
Derivative | Interest rate
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	$1
Hedged Item | Long-term debt
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	($1)

Derivatives_Open_Commodity_Der

Derivatives (Open Commodity Derivative Contracts) (Detail)	12 Months Ended
	Dec. 31, 2014
Crude Oil Exchange-Traded
Derivative [Line Items]
Percentage of derivative contracts expiring in the period	97.00%
Derivative contract expiration date	31-Mar-15
Refined Products Exchange-Traded
Derivative [Line Items]
Percentage of derivative contracts expiring in the period	100.00%
Derivative contract expiration date	31-Mar-15
Long | Crude Oil Exchange-Traded
Derivative [Line Items]
Notional Contracts (in thousands of Total Barrels)	15,678,000	[1]
Long | Refined Products Exchange-Traded
Derivative [Line Items]
Notional Contracts (in thousands of Total Barrels)	2,948,000	[2]
Short | Crude Oil Exchange-Traded
Derivative [Line Items]
Notional Contracts (in thousands of Total Barrels)	25,257,000	[1]
Short | Refined Products Exchange-Traded
Derivative [Line Items]
Notional Contracts (in thousands of Total Barrels)	3,804,000	[2]
[1]	97 percent of these contracts expire in the first quarter of 2015.
[2]	100 percent of these contracts expire in the first quarter of 2015.

Derivatives_Effect_Of_Commodit

Derivatives (Effect Of Commodity Derivative Instruments In Statements Of Income) (Detail) (Commodity derivatives, USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	$493	($168)	$73
Sales and other operating revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	37	12	8
Cost of revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	$456	($180)	$65

Debt_Outstanding_Borrowings_De

Debt (Outstanding Borrowings) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Debt Instrument [Line Items]
Total	$6,657		$3,395
Unamortized discount	-26		-10
Fair value adjustments	6	[1]	11	[1]
Amounts due within one year	-27		-23
Total long-term debt due after one year	6,610		3,373
Capital Lease Obligations [Member] | Consolidated subsidiaries:
Debt Instrument [Line Items]
Capital lease obligations	372		395
Debt instrument maturity year, start	1-Jan-15
Debt instrument maturity year, end	31-Dec-28
MPC Revolver | Line of Credit
Debt Instrument [Line Items]
Long-term debt, gross	0		0
Line of credit facility, expiration date	14-Sep-17
Term loan agreement due 2019 | Unsecured Debt
Debt Instrument [Line Items]
Long-term debt, gross	700		0
Line of credit facility, expiration date	30-Sep-19
3.500% senior notes due March 1, 2016 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross	750		750
Debt instrument, maturity date	1-Mar-16
Debt instrument, interest rate	3.50%
5.125% senior notes due March 1, 2021 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross	1,000		1,000
Debt instrument, maturity date	1-Mar-21
Debt instrument, interest rate	5.13%
3.625% senior notes due September 15, 2024 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross	750		0
Debt instrument, maturity date	15-Sep-24
Debt instrument, interest rate	3.63%
6.500% senior notes due March 1, 2041 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross	1,250		1,250
Debt instrument, maturity date	1-Mar-41
Debt instrument, interest rate	6.50%
4.750% senior notes due September 15, 2044 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross	800		0
Debt instrument, maturity date	15-Sep-44
Debt instrument, interest rate	4.75%
5.000% senior notes due September 15, 2054 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross	400		0
Debt instrument, maturity date	15-Sep-54
Debt instrument, interest rate	5.00%
MPLX Revolver | Line of Credit | MPLX Operations LLC
Debt Instrument [Line Items]
Long-term debt, gross	0		0
MPLX Revolver | Line of Credit | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross	385		0
Line of credit facility, expiration date	20-Dec-19
MPLX Revolver | Unsecured Debt | MPLX Operations LLC
Debt Instrument [Line Items]
Line of credit facility, expiration date	31-Oct-17
MPLX Term Loan | Unsecured Debt | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross	250		0
Line of credit facility, expiration date	20-Dec-19
Trade Receivables Securitization | Secured Debt | Consolidated subsidiaries:
Debt Instrument [Line Items]
Long-term debt, gross	$0		$0
Line of credit facility, expiration date	31-Dec-16
[1]	See Note 19 for information on interest rate swaps.

Debt_Schedule_Of_Debt_Payments

Debt (Schedule Of Debt Payments) (Detail) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Debt Disclosure [Abstract]
2015	$27
2016	777
2017	28
2018	30
2019	$1,362

MPC_Revolving_Credit_Agreement

MPC Revolving Credit Agreement (Detail) (USD $)	0 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Sep. 14, 2012	Nov. 21, 2014	Dec. 31, 2014	Nov. 20, 2014
				Period
MPC Revolver
Line of Credit Facility [Line Items]
Line of credit facility, current borrowing capacity	$2,500
Number of renewal periods	2
Line of credit facility duration of renewal period	1 year
MPC Revolver | Letter of Credit
Line of Credit Facility [Line Items]
Letters of credit outstanding			0
MPC Revolver | Maximum
Line of Credit Facility [Line Items]
Line of credit facility additional borrowing capacity	500
Ratio of indebtedness to net capital	0.65
MPC Revolver | Maximum | Bridge Loan
Line of Credit Facility [Line Items]
Line of credit facility, current borrowing capacity	100
MPC Revolver | Maximum | Letter of Credit
Line of Credit Facility [Line Items]
Line of credit facility, current borrowing capacity	2,000
MPC Revolver | Minimum
Line of Credit Facility [Line Items]
Lender holding percentage of outstanding commitments needed to approve increase in borrowing capacity	50.00%
MPLX LP | MPLX Term Loan
Line of Credit Facility [Line Items]
Number of renewal periods				2
Line of credit facility duration of renewal period		1 year
MPLX LP | MPLX Revolver
Line of Credit Facility [Line Items]
Line of credit facility, current borrowing capacity				1,000
Number of renewal periods				2
Line of credit facility duration of renewal period		1 year
MPLX LP | MPLX Revolver | Letter of Credit
Line of Credit Facility [Line Items]
Letters of credit outstanding			0
MPLX LP | MPLX Revolver | Maximum
Line of Credit Facility [Line Items]
Line of credit facility additional borrowing capacity				500
MPLX LP | MPLX Revolver | Maximum | Bridge Loan
Line of Credit Facility [Line Items]
Line of credit facility, current borrowing capacity				100
MPLX LP | MPLX Revolver | Maximum | Letter of Credit
Line of Credit Facility [Line Items]
Line of credit facility, current borrowing capacity				250
MPLX LP | Unsecured Debt | MPLX Term Loan
Line of Credit Facility [Line Items]
Line of credit facility, expiration date			20-Dec-19
MPLX Operations LLC | MPLX Revolver | Maximum
Line of Credit Facility [Line Items]
Line of credit facility, current borrowing capacity	$500
MPLX Operations LLC | Unsecured Debt | MPLX Revolver
Line of Credit Facility [Line Items]
Line of credit facility, expiration date			31-Oct-17

Debt_MPC_Term_Loan_Details

Debt MPC Term Loan (Details) (MPC Term Loan, USD $)	0 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Aug. 26, 2014	Dec. 31, 2014	Aug. 26, 2014
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$700		$700
Debt instrument, term	5 years
Debt instrument, description of variable rate basis	Adjusted LIBO Rate (as defined in the Term Loan Agreement)
Line of credit facility, interest rate during period		1.30%
Minimum | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	0.88%
Minimum | Base Rate
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	0.00%
Maximum
Debt Instrument [Line Items]
Ratio of indebtedness to net capital	0.65		0.65
Maximum | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	1.75%
Maximum | Base Rate
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	0.75%

Debt_Senior_Notes_Details

Debt Senior Notes (Details) (Senior Notes, USD $)	12 Months Ended
	Dec. 31, 2014	Sep. 05, 2014
Debt Instrument [Line Items]
Debt instrument, face amount		$1,950,000,000
Proceeds from debt	1,920,000,000
3.625% senior notes due September 15, 2024
Debt Instrument [Line Items]
Debt instrument, face amount		750,000,000
4.750% senior notes due September 15, 2044
Debt Instrument [Line Items]
Debt instrument, face amount		800,000,000
5.000% senior notes due September 15, 2054
Debt Instrument [Line Items]
Debt instrument, face amount		$400,000,000

Debt_MPLX_Credit_Agreement_Det

Debt MPLX Credit Agreement (Details) (USD $)	0 Months Ended	12 Months Ended	0 Months Ended
In Millions, unless otherwise specified	Nov. 21, 2014	Dec. 31, 2014	Sep. 14, 2012	Nov. 20, 2014	Dec. 31, 2013
				Period
MPLX LP | MPLX Term Loan
Debt Instrument [Line Items]
Debt instrument, term	5 years
Line of credit facility, maximum borrowing capacity				$250
Number of renewal periods				2
Line of credit facility duration of renewal period	1 year
Line of credit facility, interest rate during period		1.40%
Debt instrument, description of variable rate basis	Adjusted LIBO Rate or the Alternate Base Rate (as defined in the MPLX Credit Agreement)
MPLX LP | MPLX Revolver
Debt Instrument [Line Items]
Debt instrument, term	5 years
Line of credit facility, current borrowing capacity				1,000
Number of renewal periods				2
Line of credit facility duration of renewal period	1 year
Line of credit facility, interest rate during period		1.40%
Debt instrument, description of variable rate basis	Adjusted LIBO Rate or the Alternate Base Rate (as defined in the MPLX Credit Agreement)
Line of credit facility, borrowings during period		630
Line of credit facility, repayments during period		245
Remaining borrowing capacity		615
Remaining borrowing capacity, percentage		61.50%
MPLX LP | Line of Credit | MPLX Revolver
Debt Instrument [Line Items]
Long-term debt, gross		385			0
MPLX LP | Maximum | MPLX Term Loan
Debt Instrument [Line Items]
Number of prior quarterly reporting periods covenant				4
Covenant ratio debt to EBITDA				5
Covenant ratio debt to EBITDA post acquisition				5.5
MPLX LP | Maximum | MPLX Revolver
Debt Instrument [Line Items]
Line of credit facility additional borrowing capacity				500
Number of prior quarterly reporting periods covenant				4
Covenant ratio debt to EBITDA				5
Covenant ratio debt to EBITDA post acquisition				5.5
MPLX LP | Letter of Credit | MPLX Revolver
Debt Instrument [Line Items]
Letters of credit outstanding		0
MPLX LP | Letter of Credit | Maximum | MPLX Revolver
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity				250
MPLX LP | Bridge Loan | Maximum | MPLX Revolver
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity				100
MPLX Operations LLC | MPLX Revolver
Debt Instrument [Line Items]
Debt instrument, term			5 years
Line of credit facility, interest rate during period		1.50%
Line of credit facility, borrowings during period		280
MPLX Operations LLC | Line of Credit | MPLX Revolver
Debt Instrument [Line Items]
Line of credit facility, repayments during period		280
Long-term debt, gross		0			0
MPLX Operations LLC | Maximum | MPLX Revolver
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity			500

Debt_Trade_Receivables_Securit

Debt Trade Receivables Securitization Facility (Details) (Trade Receivables Securitization, USD $)	0 Months Ended
In Millions, unless otherwise specified	Dec. 18, 2013	Dec. 31, 2014	Jan. 31, 2015
Debt Instrument [Line Items]
Line of credit facility, expiration period	3 years
Line of credit facility, maximum borrowing capacity	$1,300
Line of credit facility, current borrowing capacity		1,280
Scenario, Forecast
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity			700
Letter of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$1,250

Supplemental_Cash_Flow_Informa2

Supplemental Cash Flow Information (Summary Of Supplemental Cash Flow Information) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013		Dec. 31, 2012
Net cash provided by operating activities included:
Interest paid (net of amounts capitalized)	$166	$161		$67
Net income taxes paid to taxing authorities	1,362	1,099		1,211	[1]
Non-cash investing and financing activities:
Capital lease obligations increase	0	61		62
Property, plant and equipment sold	4	43		0
Property, plant and equipment acquired	4	0		0
Preferred equity interest received in contract settlement	0	0		45	[2]
Preferred equity interest dividend received in-kind	0	0		1
Acquisition:
Contingent consideration	0	600	[3]	0
Payable to seller	0	6	[3]	0
Intangible asset acquired	0	0		3
Liability assumed	0	0		2
Marathon Oil Companies
Net cash provided by operating activities included:
Related party tax payments				$181
[1]	U.S. and most state income taxes, if incurred, were paid by Marathon Oil for periods prior to the Spinoff. The amount for 2012 includes payments of $181 million for 2011 return period income taxes made to Marathon Oil under our tax sharing agreement, and in return we received an equal amount of tax credits. See Note 26.
[2]	See Note 6.
[3]	See Note 5.

Supplemental_Cash_Flow_Informa3

Supplemental Cash Flow Information (Reconciliation Of Additions To Property, Plant And Equipment To Total Capital Expenditures) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Supplemental Cash Flow Information [Abstract]
Additions to property, plant and equipment per consolidated statements of cash flows	$1,480		$1,206		$1,369
Non-cash additions to property, plant and equipment	4		0		0
Asset retirement expenditures	2	[1]	0		0
Increase (decrease) in capital accruals	95		73		-117
Total capital expenditures before acquisitions	1,581		1,279		1,252
Acquisitions	2,744	[2]	1,386	[2]	180
Total capital expenditures	$4,325	[3],[4]	$2,665	[3],[4]	$1,432	[3],[4]
[1]	Included in All other, net – Operating activities on the consolidated statements of cash flows.
[2]	The 2014 acquisitions include the acquisition of Hess’ Retail Operations and Related Assets. The 2013 acquisitions include the acquisition of the Galveston Bay Refinery and Related Assets. The acquisition numbers above include property, plant and equipment and intangibles. See Note 5.
[3]	See Note 21 for a reconciliation of total capital expenditures to additions to property, plant and equipment as reported in the consolidated statements of cash flows.
[4]	Capital expenditures include changes in capital accruals.

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Loss (Changes in Accumulated Other Comprehensive Loss by Component) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	($204)		($464)
Other comprehensive income (loss) before reclassifications	-170		189
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit	-50	[1]	-49	[1]
Amortization– actuarial loss	53	[1]	69	[1]
Amortization– settlement loss	96	[1]	95	[1]
Other	-1	[2]	-1	[2]
Tax effect	-37		-43
Other comprehensive income (loss)	-109		260		415
Ending balance	-313		-204		-464
Pension Benefits
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit	-46		-45		-18
Other Benefits
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit	-4		-4		-2
Accumulated Defined Benefit Plans Adjustment | Pension Benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	-161		-432
Other comprehensive income (loss) before reclassifications	-119		198
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit	-46		-45
Amortization– actuarial loss	51		66
Amortization– settlement loss	96		95
Tax effect	-38		-43
Other comprehensive income (loss)	-56		271
Ending balance	-217		-161
Accumulated Defined Benefit Plans Adjustment | Other Benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	-50		-36
Other comprehensive income (loss) before reclassifications	-53		-13
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit	-4		-4
Amortization– actuarial loss	2		3
Amortization– settlement loss	0		0
Tax effect	1		0
Other comprehensive income (loss)	-54		-14
Ending balance	-104		-50
Gain on Cash Flow Hedge
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
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
Workers Compensation
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	3		0
Other comprehensive income (loss) before reclassifications	2		4
Amounts reclassified from accumulated other comprehensive loss:
Other	-1		-1
Tax effect	0		0
Other comprehensive income (loss)	1		3
Ending balance	$4		$3
[1]	These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 23.
[2]	This amount was reclassified out of accumulated other comprehensive loss and is included in selling, general and administrative expenses on the consolidated statements of income.

Recovered_Sheet1

Defined Benefit Pension And Other Postretirement Plans (Narrative) (Detail) (USD $)	12 Months Ended			1 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 01, 2013
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$2,009	$1,912
Defined benefit plan investment goals	The overall expected long-term return on plan assets assumption is determined based on an asset rate-of-return modeling tool developed by a third-party investment group. The tool utilizes underlying assumptions based on actual returns by asset category and inflation and takes into account our asset allocation to derive an expected long-term rate of return on those assets. Capital market assumptions reflect the long-term capital market outlook. The assumptions for equity and fixed income investments are developed using a building-block approach, reflecting observable inflation information and interest rate information available in the fixed income markets. Long-term assumptions for other asset categories are based on historical results, current market characteristics and the professional judgment of our internal and external investment teams.
Defined benefit plan, diversification	The asset allocation strategy will change over time in response to changes primarily in funded status, which is dictated by current and anticipated market conditions, the independent actions of our investment committee, required cash flows to and from the plans and other factors deemed appropriate. Such changes in asset allocation are intended to allocate additional assets to the fixed income asset class should the funded status improve. The fixed income asset class shall be invested in such a manner that its interest rate sensitivity correlates highly with that of the plans’ liabilities. Other asset classes are intended to provide additional return with associated higher levels of risk.
Plan investment policies and strategies	Investment performance and risk is measured and monitored on an ongoing basis through quarterly investment meetings and periodic asset and liability studies.
Contributions to defined contribution plans	86	76	60
Multiemployer pension plans percentage funded	65.00%
Marathon Petroleum's contributions as a percentage of total contributions to the multi-employer pension plan, maximum	5.00%
Multiemployer Plans, Pension
Defined Benefit Plan Disclosure [Line Items]
Number of multiemployer defined benefit pension or health and welfare plan	1
Multi employer pension plans	There have been no significant changes that affect the comparability of 2014, 2013 and 2012 contributions.
Multiemployer Plans, Postretirement Benefit
Defined Benefit Plan Disclosure [Line Items]
Number of multiemployer defined benefit pension or health and welfare plan	1
MPC contributions	6	5	5
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Targeted asset allocation	51.00%
Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Targeted asset allocation	49.00%
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Estimated net gain (loss) that will be amortized from accumulated other comprehensive loss in 2014	51
Estimated prior service cost that will be amortized from accumulated other comprehensive loss in 2014	46
Pension contributions	16
Defined benefit plans, estimated future employer contributions in next fiscal year	0
Medical Post-65 | Maximum
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for the following year:	4.00%
Unfunded Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plans, estimated future employer contributions in next fiscal year	18
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Estimated net gain (loss) that will be amortized from accumulated other comprehensive loss in 2014	9
Estimated prior service cost that will be amortized from accumulated other comprehensive loss in 2014	4
Defined benefit plans, estimated future employer contributions in next fiscal year	27
Galveston Bay Refinery and Related Assets
Defined Benefit Plan Disclosure [Line Items]
Decrease in liabilities				-122
Galveston Bay Refinery and Related Assets | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage increase in discount rates				0.20%
Galveston Bay Refinery and Related Assets | Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Liability related to retiree medical assumed at the acquisition date				$43

Recovered_Sheet2

Defined Benefit Pension And Other Postretirement Plans (Summary Of Defined Benefit Plans With Accumulated Benefit Obligations In Excess Of Plan Assets) (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Projected benefit obligations	$2,075	$1,927
Accumulated benefit obligations	2,009	1,912
Fair value of plan assets	$1,744	$1,800

Defined_Benefit_Pension_And_Ot2

Defined Benefit Pension And Other Postretirement Plans (Summary Of Projected Benefit Obligations And Funded Status For Defined Benefit Pension And Other Postretirement Plans) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Change in plan assets:
Fair value of plan assets at December 31	$1,744		$1,800
Amounts recognized in the consolidated balance sheets:
Noncurrent liabilities	-1,099		-771
Pension Benefits
Change in benefit obligations:
Benefit obligations at January 1	1,927		2,192
Service cost	88		93		66
Interest cost	74		73		94
Actuarial (gain) loss	257		-183
Benefits paid	-271		-248
Other	0	[1]	0	[1]
Benefit obligations at December 31	2,075		1,927		2,192
Change in plan assets:
Fair value of plan assets at January 1	1,800		1,478
Actual return on plan assets	175		241
Employer contributions	40		329
Benefits paid	-271		-248
Fair value of plan assets at December 31	1,744		1,800		1,478
Funded status of plans at December 31	-331		-127
Amounts recognized in the consolidated balance sheets:
Current liabilities	-17		-18
Noncurrent liabilities	-314		-109
Accrued benefit cost	-331		-127
Pretax amounts recognized in accumulated other comprehensive loss:
Net loss	710	[2]	668	[2]
Prior service credit	-369	[2]	-415	[2]
Pension Benefits | LOOP LLC and Explorer Pipeline [Member]
Pretax amounts recognized in accumulated other comprehensive loss:
Net loss	18	[2]
Other Benefits
Change in benefit obligations:
Benefit obligations at January 1	687		591
Service cost	27		25		20
Interest cost	33		26		24
Actuarial (gain) loss	86		17
Benefits paid	-23		-20
Other	2	[1]	48	[1]
Benefit obligations at December 31	812		687		591
Change in plan assets:
Benefits paid	-23		-20
Funded status of plans at December 31	-812		-687
Amounts recognized in the consolidated balance sheets:
Current liabilities	-27		-25
Noncurrent liabilities	-785		-662
Accrued benefit cost	-812		-687
Pretax amounts recognized in accumulated other comprehensive loss:
Net loss	191	[2]	107	[2]
Prior service credit	-26	[2]	-30	[2]
Other Benefits | LOOP LLC and Explorer Pipeline [Member]
Pretax amounts recognized in accumulated other comprehensive loss:
Net loss	$1	[2]
[1]	Includes adjustments related to Hess’ Retail Operations and Related Assets acquisition in 2014. For 2013, it includes adjustments related to plan amendments and adjustments related to the Galveston Bay Refinery and Related Assets acquisition.
[2]	Amounts exclude those related to LOOP and Explorer Pipeline, equity method investees with defined benefit pension and postretirement plans for which net losses of $18 million and $1 million were recorded in accumulated other comprehensive loss in 2014, reflecting our ownership share.

Defined_Benefit_Pension_And_Ot3

Defined Benefit Pension And Other Postretirement Plans (Components Of Net Periodic Benefit Cost And Other Comprehensive Loss) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax):
Amortization of prior service cost	$50	[1]	$49	[1]
Pension Benefits
Components of net periodic benefit cost:
Service cost	88		93		66
Interest cost	74		73		94
Expected return on plan assets	-107		-107		-104
Amortization – prior service cost (credit)	-46		-45		-18
Amortization – actuarial loss	51		66		93
Amortization – settlement loss	96		95		125
Net periodic benefit cost	156	[2]	175	[2]	256	[2]
Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax):
Actuarial (gain) loss	188		-317		46
Prior service cost (credit)	0	[3]	0	[3]	-520	[3]
Amortization of actuarial loss	-147		-161		-218
Amortization of prior service cost	46		45		18
Other	0		0		0
Total recognized in other comprehensive loss	87		-433		-674
Total recognized in net periodic benefit cost and other comprehensive loss	243		-258		-418
Other Benefits
Components of net periodic benefit cost:
Service cost	27		25		20
Interest cost	33		26		24
Expected return on plan assets	0		0		0
Amortization – prior service cost (credit)	-4		-4		-2
Amortization – actuarial loss	2		3		2
Amortization – settlement loss	0		0		0
Net periodic benefit cost	58	[2]	50	[2]	44	[2]
Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax):
Actuarial (gain) loss	86		17		53
Prior service cost (credit)	0	[3]	4	[3]	-40	[3]
Amortization of actuarial loss	-2		-3		-2
Amortization of prior service cost	4		4		2
Other	0		0		0
Total recognized in other comprehensive loss	88		22		13
Total recognized in net periodic benefit cost and other comprehensive loss	$146		$72		$57
[1]	These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 23.
[2]	Net periodic benefit cost reflects a calculated market-related value of plan assets which recognizes changes in fair value over three years.
[3]	Includes adjustments due to plan amendments approved in 2013 and adjustments due to changes made to the defined pension plans and the post-65 medical plan coverage effective January 1, 2013.

Defined_Benefit_Pension_And_Ot4

Defined Benefit Pension And Other Postretirement Plans (Summary Of Assumptions Used To Determine Benefit Obligations And Net Periodic Benefit Cost) (Detail)	12 Months Ended						1 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012		Jan. 31, 2015
Pension Benefits
Weighted-average assumptions used to determine benefit obligation:
Discount rate	3.65%		4.30%		3.45%
Rate of compensation increase	3.70%		3.70%		5.00%
Weighted-average assumptions used to determine net periodic benefit cost:
Discount rate	4.05%		3.88%		4.06%
Expected long-term return on plan assets	7.00%	[1]	7.50%	[1]	7.50%	[1]
Rate of compensation increase	3.70%		5.00%		5.00%
Pension Benefits | Scenario, Forecast
Weighted-average assumptions used to determine net periodic benefit cost:
Expected long-term return on plan assets							6.75%	[1]
Other Benefits
Weighted-average assumptions used to determine benefit obligation:
Discount rate	4.15%		4.95%		4.05%
Rate of compensation increase	3.70%		3.70%		5.00%
Weighted-average assumptions used to determine net periodic benefit cost:
Discount rate	4.95%		4.11%		4.54%
Expected long-term return on plan assets	0.00%	[1]	0.00%	[1]	0.00%	[1]
Rate of compensation increase	3.70%		5.00%		5.00%
[1]	Effective January 1, 2015, the expected long-term rate of return on plan assets is 6.75 percent due to a continuation of a change in our primary plan investment strategy, which began January 1, 2014.

Defined_Benefit_Pension_And_Ot5

Defined Benefit Pension And Other Postretirement Plans (Summarizes Assumed Health Care Cost Trend Rates) (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Medical Pre-65
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for the following year:	8.00%	8.00%	8.00%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate):	5.00%	5.00%	5.00%
Year that the rate reaches the ultimate trend rate:	2021	2020	2020
Prescription drugs
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for the following year:	7.00%	7.00%	7.00%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate):	5.00%	5.00%	5.00%
Year that the rate reaches the ultimate trend rate:	2021	2018	2018

Defined_Benefit_Pension_And_Ot6

Defined Benefit Pension And Other Postretirement Plans (Effects Of One Percentage Point Change In Assumed Health Care Cost Trend Rates) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Effect on total of service and interest cost components, 1-Percentage-Point-Increase	$5
Effect on other postretirement benefit obligations, 1-Percentage-Point-Increase	45
Effect on total of service and interest cost components, 1-Percentage-Point Decrease	-4
Effect on other postretirement benefit obligations, 1-Percentage-Point-Decrease	($39)

Defined_Benefit_Pension_And_Ot7

Defined Benefit Pension And Other Postretirement Plans (Fair Values Of Defined Benefit Pension Plan Assets) (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	$1,744	$1,800
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	29	189
Equity investments, common stocks
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	63	69
Equity funds, mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	155	217
Equity funds, pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	442	590
Fixed income, corporate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	554	356
Fixed income, government
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	99	22
Fixed income, pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	254	218
Private equity
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	66	57
Real estate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	57	60
Other
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	25	22
Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	220	288
Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 1 | Equity investments, common stocks
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	63	69
Level 1 | Equity funds, mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	155	217
Level 1 | Equity funds, pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 1 | Fixed income, corporate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 1 | Fixed income, government
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 1 | Fixed income, pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 1 | Private equity
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 1 | Real estate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 1 | Other
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	2	2
Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	1,380	1,375
Level 2 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	29	189
Level 2 | Equity investments, common stocks
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 2 | Equity funds, mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 2 | Equity funds, pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	442	590
Level 2 | Fixed income, corporate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	554	356
Level 2 | Fixed income, government
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	99	22
Level 2 | Fixed income, pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	254	218
Level 2 | Private equity
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 2 | Real estate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 2 | Other
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	2	0
Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	144	137	127
Level 3 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 3 | Equity investments, common stocks
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 3 | Equity funds, mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 3 | Equity funds, pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 3 | Fixed income, corporate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 3 | Fixed income, government
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 3 | Fixed income, pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 3 | Private equity
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	66	57	56
Level 3 | Real estate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	57	60	54
Level 3 | Other
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	$21	$20	$17

Defined_Benefit_Pension_And_Ot8

Defined Benefit Pension And Other Postretirement Plans (Reconciliation Of Beginning And Ending Balances Of Plan Assets Classified As Level 3) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Actual return on plan assets:
Fair value of plan assets at December 31	$1,744	$1,800
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	137	127
Actual return on plan assets:
Realized	10	16
Unrealized	11	16
Purchases	15	12
Sales	-29	-34
Fair value of plan assets at December 31	144	137
Private equity
Actual return on plan assets:
Fair value of plan assets at December 31	66	57
Private equity | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	57	56
Actual return on plan assets:
Realized	6	13
Unrealized	6	3
Purchases	10	7
Sales	-13	-22
Fair value of plan assets at December 31	66	57
Real estate
Actual return on plan assets:
Fair value of plan assets at December 31	57	60
Real estate | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	60	54
Actual return on plan assets:
Realized	4	3
Unrealized	4	10
Purchases	5	5
Sales	-16	-12
Fair value of plan assets at December 31	57	60
Other
Actual return on plan assets:
Fair value of plan assets at December 31	25	22
Other | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	20	17
Actual return on plan assets:
Realized	0	0
Unrealized	1	3
Purchases	0	0
Sales	0	0
Fair value of plan assets at December 31	$21	$20

Defined_Benefit_Pension_And_Ot9

Defined Benefit Pension And Other Postretirement Plans (Estimated Future Benefit Payments) (Detail) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
2015	$179
2016	181
2017	181
2018	181
2019	179
2020 through 2024	810
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
2015	27
2016	30
2017	33
2018	37
2019	40
2020 through 2024	$236

Recovered_Sheet3

Defined Benefit Pension And Other Postretirement Plans (Multi Employer Pension Plan) (Detail) (Multiemployer Plans, Pension, USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Multiemployer Plans [Line Items]
Multiemployer pension plan, minimum contribution requirement per week per employee	$280
Number of employees participated in the plan	267
Central States, Southeast and Southwest Pension Plan [Member]
Multiemployer Plans [Line Items]
MPC contributions	$4,000,000	[1]	$3,000,000	[1]	$4,000,000	[1]
[1]	This agreement has a minimum contribution requirement of $280 per week per employee for 2015. A total of 267 employees participated in the plan as of December 31, 2014.

StockBased_Compensation_Plans_1

Stock-Based Compensation Plans (Narrative) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted units outstanding	411,093
Non-Employee Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted units vested	409,805
Weighted average fair value, vested	$37.16
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	0
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, expiration period	10 years
Vesting period of awards	3 years
Implied volatility rate weighting (in percentage)	50.00%
Historical volatility rate weighting (in percentage)	50.00%
Intrinsic value of options exercised	48,000,000	60,000,000	37,000,000
Unrecognized compensation cost	5,000,000
Weighted average recognition period, in years	1 year 1 month 6 days
Stock Appreciation Rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, expiration period	10 years
Vesting period of awards	3 years
Restricted Stock Awards and Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards	3 years
Restricted stock and restricted stock unit awards granted in 2012, additional holding period	1 year
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	26,000,000
Weighted average recognition period, in years	1 year 1 month 6 days
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target payout	$1
Unrecognized compensation cost	$2,000,000
Weighted average recognition period, in years	1 year 6 months
Shares issued in period	64,168
Maximum | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Actual payout	$2
Target payout percentage	200.00%
MPC 2012 Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock authorized to be delivered under the compensation plan	25,000,000
MPC 2012 Plan | Maximum | Awards Other Than Stock Options Or Stock Appreciation Rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock authorized to be delivered under the compensation plan	10,000,000
MPC 2012 Plan | Maximum | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock authorized to be delivered under the compensation plan	10,000,000
MPC 2012 and 2011 Plans | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards	36 months
Pay-out percentage in MPC common stock (in percentage)	25.00%
Pay-out percentage in cash (in percentage)	75.00%

StockBased_Compensation_Plans_2

Stock-Based Compensation Plans (Stock-Based Compensation Expense) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-based compensation expense	$40	$42	$35
Tax benefit recognized on stock-based compensation expense	15	15	13
Cash received by MPC upon exercise of stock option awards	26	48	108
Tax benefit received for tax deductions for stock awards exercised	$19	$18	$16

StockBased_Compensation_Plans_3

Stock-Based Compensation Plans (Weighted Average Assumptions Used To Value Stock Options Awards) (Detail) (Stock Options, USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average exercise price per share	$85.02	$84.65	$42.02
Expected life in years	5 years 9 months 19 days	6 years	5 years 9 months 18 days
Expected volatility	36.00%	40.00%	47.00%
Expected dividend yield	1.90%	2.00%	2.60%
Risk-free interest rate	1.80%	1.00%	1.10%
Weighted average grant date fair value of stock option awards granted	$25.37	$27.13	$14.45

StockBased_Compensation_Plans_4

Stock-Based Compensation Plans (Summary Of Stock Option Award Activity) (Detail) (Stock Options, USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Stock Options
Number of Shares
Outstanding, beginning balance	5,147,837	[1]
Granted	446,310	[1]
Exercised	-821,948	[1]
Forfeited, canceled or expired	-20,761	[1]
Outstanding, ending balance	4,751,438	[1]	5,147,837	[1]
Vested and expected to vest at December 31, 2014 (in shares)	4,746,653	[1]
Exercisable at December 31, 2014 (in shares)	3,795,031	[1]
Weighted Average Exercise Price
Outstanding, beginning balance (in USD per share)	$40.08
Granted (in USD per share)	$85.02		$84.65		$42.02
Exercised (in USD per share)	$33.04
Forfeited, canceled or expired (in USD per share)	$49.67
Outstanding, ending balance (in USD per share)	$45.47		$40.08
Vested and expected to vest at December 31, 2014 (in USD per share)	$45.43
Exercisable at December 31, 2014 (in USD per share)	$38.30
Weighted Average Remaining Contractual Terms (in years)
Vested and expected to vest at December 31, 2013 (in years)	5 years 8 months
Exercisable at December 31, 2013 (in years)	5 years 15 days
Aggregate Intrinsic Value (in millions)
Vested and expected to vest at December 31, 2013 (in USD)	$213
Exercisable at December 31, 2013 (in USD)	$197
[1]	Includes an immaterial number of stock appreciation rights.

StockBased_Compensation_Plans_5

Stock-Based Compensation Plans (Summary Of Restricted Stock Award Activity) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restricted Stock
Number of Shares
Outstanding, beginning balance	624,122
Granted	251,351
RS’s Vested/RSU’s Issued	-330,971
Forfeited	-29,429
Outstanding, ending balance	515,073	624,122
Weighted Average Grant Date Fair Value
Outstanding, beginning balance (in USD per share)	$61.11
Granted (in USD per share)	$87.64	$87.06	$43.11
RS's Vested/RSU's Issued (in USD per share)	$55.36
Forfeited (in USD per share)	$70.29
Outstanding, ending balance (in USD per share)	$77.23	$61.11
Restricted Stock Units
Number of Shares
Outstanding, beginning balance	385,079
Granted	26,725
RS’s Vested/RSU’s Issued	-578
Forfeited	-133
Outstanding, ending balance	411,093	385,079
Weighted Average Grant Date Fair Value
Outstanding, beginning balance (in USD per share)	$33.96
Granted (in USD per share)	$85.90	$73.48	$44.38
RS's Vested/RSU's Issued (in USD per share)	$51.99
Forfeited (in USD per share)	$76.10
Outstanding, ending balance (in USD per share)	$37.30	$33.96

StockBased_Compensation_Plans_6

Stock-Based Compensation Plans (Summary Of Values Related To Vested And Unvested Restricted Stock Awards) (Detail) (USD $)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic Value of Awards Vested During the Period (in millions)	$28	$20	$5
Weighted Average Grant Date Fair Value of Awards Granted During the Period	$87.64	$87.06	$43.11
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic Value of Awards Vested During the Period (in millions)	$0	$0	$0
Weighted Average Grant Date Fair Value of Awards Granted During the Period	$85.90	$73.48	$44.38

StockBased_Compensation_Plans_7

Stock-Based Compensation Plans (Summary Of Performance Unit Awards) (Detail) (Performance Shares, USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Performance Shares
Number of Shares
Outstanding, beginning balance	3,822,500
Granted	2,033,700
Canceled	-64,375
Outstanding, ending balance	5,791,825	3,822,500
Weighted Average Grant Date Fair Value
Outstanding, beginning balance (in USD per share)	$0.90
Granted (in USD per share)	$0.85	$0.95	$0.80
Forfeited (in USD per share)	$0.87
Outstanding, ending balance (in USD per share)	$0.88	$0.90

StockBased_Compensation_Plans_8

Stock-Based Compensation Plans (Weighted Average Assumptions Used to Value Performance Unit Awards) (Details) (Performance Shares, USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.63%	0.35%	0.41%
Look-back period	2 years 10 months 3 days	2 years 10 months 3 days	2 years 10 months 3 days
Expected volatility	38.51%	41.67%	56.06%
Grant date fair value of performance units granted	$0.85	$0.95	$0.80

Leases_Schedule_Of_Future_Mini

Leases (Schedule Of Future Minimum Commitments) (Detail) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Capital Lease Obligations, 2015	$52
Capital Lease Obligations, 2016	51
Capital Lease Obligations, 2017	50
Capital Lease Obligations, 2018	49
Capital Lease Obligations, 2019	45
Capital Lease Obligations, Later years	300
Total minimum lease payments	547
Less imputed interest costs	-176
Present value of net minimum lease payments	371
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Operating Lease Obligations, 2015	249
Operating Lease Obligations, 2016	209
Operating Lease Obligations, 2017	150
Operating Lease Obligations, 2018	136
Operating Lease Obligations, 2019	114
Operating Lease Obligations, Later years	468
Total minimum lease payments	$1,326

Leases_Schedule_Of_Operating_L

Leases (Schedule Of Operating Lease Rental Expense) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Leases [Abstract]
Rental expense	$256	$213	$139

Commitments_And_Contingencies_

Commitments And Contingencies (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Feb. 01, 2013
Loss Contingencies [Line Items]
Accrued liabilities for remediation	$185,000,000	$123,000,000
Receivables for recoverable costs	67,000,000	51,000,000
Contractual commitments to acquire property, plant and equipment and advance funds to equity method investees	1,700,000,000	1,700,000,000
Galveston Bay Refinery and Related Assets
Loss Contingencies [Line Items]
Maximum earnout provision payable to the company	520,000,000	700,000,000	700,000,000
North Dakota Pipeline
Loss Contingencies [Line Items]
Contractual commitments to acquire property, plant and equipment and advance funds to equity method investees	703,000,000	892,000,000
Illinois Extension Pipeline Company LLC
Loss Contingencies [Line Items]
Contractual commitments to acquire property, plant and equipment and advance funds to equity method investees	185,000,000
Indemnification Agreement | Marathon Oil Companies
Loss Contingencies [Line Items]
Guarantee obligation current carrying value	2,000,000
Other Guarantees | Equity Method Investees
Loss Contingencies [Line Items]
Maximum potential undiscounted payments	81,000,000
Guarantee obligations maximum exposure per event	50,000,000
Guarantee of Indebtedness of Others | Financial Guarantee | LOOP and LOCAP LLC
Loss Contingencies [Line Items]
Line of credit facility, expiration date	31-Dec-37
Maximum potential undiscounted payments	172,000,000
Master Shelf Agreement | Financial Guarantee | Centennial
Loss Contingencies [Line Items]
Line of credit facility, expiration date	31-Dec-24
Maximum potential undiscounted payments	38,000,000
Pending Litigation
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.
Pending Litigation | Emergency Pricing And Consumer Protection Laws
Loss Contingencies [Line Items]
Plaintiff	Commonwealth of Kentucky
Alleged amount overcharged from customers	$89,000,000
Loss contingency, period of occurrence	during September and October 2005

Subsequent_Event_Subsequent_Ev

Subsequent Event Subsequent Event (Details) (USD $)	0 Months Ended
In Millions, unless otherwise specified	Feb. 12, 2015	Sep. 05, 2014
Senior Notes Due Two Thousand Twenty Five [Member] | MPLX LP | Subsequent Event
Subsequent Event [Line Items]
Price to the public	99.64%
Senior Notes
Subsequent Event [Line Items]
Debt instrument, face amount		$1,950
Senior Notes | Senior Notes Due Two Thousand Twenty Five [Member] | MPLX LP | Subsequent Event
Subsequent Event [Line Items]
Debt instrument, face amount	$500
Debt instrument, interest rate	4.00%
Debt instrument, maturity date	15-Feb-25

Selected_Quarterly_Financial_D2

Selected Quarterly Financial Data (Schedule Of Quarterly Financial Information) (Detail) (USD $)	3 Months Ended								12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Data [Abstract]
Revenues	$22,250	$25,438	$26,844	$23,285	$24,897	$26,256	$25,677	$23,330
Income from operations	1,259	1,062	1,369	361	1,008	301	960	1,156	4,051	3,425	5,347
Net income	805	679	864	207	631	173	599	730	2,555	2,133	3,393
Net income attributable to MPC	$798	$672	$855	$199	$626	$168	$593	$725	$2,524	$2,112	$3,389
Net income attributable to MPC per share:
Basic (in USD per share)	$2.88	$2.38	$2.97	$0.68	$2.09	$0.54	$1.84	$2.19	$8.84	$6.69	$9.95
Diluted (in USD per share)	$2.86	$2.36	$2.95	$0.67	$2.07	$0.54	$1.83	$2.17	$8.78	$6.64	$9.89
Dividends paid per share (in USD per share)	$0.50	$0.50	$0.42	$0.42	$0.42	$0.42	$0.35	$0.35	$1.84	$1.54	$1.20

Supplementary_Statistics_Suppl

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

3 Months Ended

12 Months Ended

0 Months Ended

1 Months Ended

In Millions, unless otherwise specified

Dec. 31, 2014

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Sep. 30, 2014

Feb. 01, 2013

Supplementary Statistics [Line Items]

Income from operations

$1,259

$1,062

$1,369

$361

$1,008

$301

$960

$1,156

$4,051

$3,425

$5,347

Minnesota Assets sale settlement gain

21

6

177

Segment capital expenditures and investments

4,738

[1],[2]

2,789

[1],[2]

1,460

[1],[2]

Hess Retail Operations and Related Assets

Supplementary Statistics [Line Items]

Segment capital expenditures and investments

2,710

Galveston Bay Refinery and Related Assets

Supplementary Statistics [Line Items]

Segment capital expenditures and investments

1,360

Operating Segments

Supplementary Statistics [Line Items]

Income from operations

4,433

[3]

3,791

[3]

5,624

[3]

Segment capital expenditures and investments

4,628

[4],[5]

2,624

[4],[6]

1,256

[4]

Operating Segments | Refining & Marketing

Supplementary Statistics [Line Items]

Income from operations

3,609

[3]

3,206

[3]

5,098

[3]

Segment capital expenditures and investments

1,104

[4],[5]

2,094

[4],[6]

705

[4]

Operating Segments | Refining & Marketing | Hess Retail Operations and Related Assets

Supplementary Statistics [Line Items]

Segment capital expenditures and investments

52

Operating Segments | Refining & Marketing | Galveston Bay Refinery and Related Assets

Supplementary Statistics [Line Items]

Segment capital expenditures and investments

1,290

Operating Segments | Speedway

Supplementary Statistics [Line Items]

Income from operations

544

[3]

375

[3]

310

[3]

Segment capital expenditures and investments

2,981

[4],[5]

296

[4],[6]

340

[4]

Operating Segments | Speedway | Hess Retail Operations and Related Assets

Supplementary Statistics [Line Items]

Segment capital expenditures and investments

2,660

Operating Segments | Pipeline Transportation

Supplementary Statistics [Line Items]

Income from operations

280

[3]

210

[3]

216

[3]

Segment capital expenditures and investments

543

[4],[5]

234

[4],[6]

211

[4]

Operating Segments | Pipeline Transportation | Galveston Bay Refinery and Related Assets

Supplementary Statistics [Line Items]

Segment capital expenditures and investments

70

Operating Segments | Pipeline Transportation | MPLX LP

Supplementary Statistics [Line Items]

Cost of services, overhead

19

20

4

Corporate and Other

Supplementary Statistics [Line Items]

Income from operations

-286

[7],[8]

-271

[7],[8]

-336

[7],[8]

Segment capital expenditures and investments

110

[9]

165

[9]

204

[9]

Capitalized interest

27

28

101

Segment Reconciling Items

Supplementary Statistics [Line Items]

Minnesota Assets sale settlement gain

0

[10]

0

[10]

183

[10]

Pension settlement expenses

($96)

[11]

($95)

[11]

($124)

[11]

[1]

Capital expenditures include changes in capital accruals.

[2]

Includes $2.71 billion in 2014 for the acquisition of Hess’ Retail Operations and Related Assets and $1.36 billion in 2013 for the acquisition of the Galveston Bay Refinery and Related Assets. See Note 5 to the audited consolidated financial statements.

[3]

Included in the Pipeline Transportation segment for 2014, 2013 and 2012 are $19 million, $20 million and $4 million of corporate overhead expenses attributable to MPLX, which were included in items not allocated to segments prior to MPLX’s October 31, 2012 initial public offering. Corporate overhead expenses are not currently allocated to other segments.

[4]

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

[5]

The Speedway and Refining & Marketing segments include $2.66 billion and $52 million, respectively, for the acquisition of Hess’ Retail Operations and Related Assets. See Note 5.

[6]

The Refining & Marketing and Pipeline Transportation segments include $1.29 billion and $70 million, respectively, for the acquisition of the Galveston Bay Refinery and Related Assets. See Note 5.

[7]

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

[8]

Corporate overhead expenses attributable to MPLX were included in the Pipeline Transportation segment subsequent to MPLX’s October 31, 2012 initial public offering. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments.

[9]

Includes capitalized interest of $27 million, $28 million and $101 million for 2014, 2013 and 2012, respectively.

[10]

See Note 6.

[11]

See Note 23.

Supplementary_Statistics_Opera

Supplementary Statistics (Operating Statistics) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Operating Statistics [Line Items ]
MPC Consolidated Refined Product Sales Volumes (thousands of barrels per day)	2,138,000	[1],[2]	2,086,000	[1],[2]	1,618,000	[1],[2]
Refining & Marketing
Refining & Marketing Operating Statistics
Refining & Marketing refined product sales volume (thousands of barrels per day)	2,125,000	[1],[3]	2,075,000	[1],[3]	1,599,000	[1],[3]
Refining & Marketing gross margin (dollars per barrel)	15.05	[1],[4]	13.24	[1],[4]	17.85	[1],[4]
Crude oil capacity utilization percent	95.00%	[1],[5]	96.00%	[1],[5]	100.00%	[1],[5]
Refinery throughputs (thousands of barrels per day)	1,806,000	[1],[6]	1,802,000	[1],[6]	1,363,000	[1],[6]
Sour crude oil throughput percent	52.00%	[1]	53.00%	[1]	53.00%	[1]
WTI-priced crude oil throughput percent	19.00%	[1]	21.00%	[1]	28.00%	[1]
Refined product yields (thousands of barrels per day)	1,839,000	[1],[6]	1,836,000	[1],[6]	1,386,000	[1],[6]
Refinery direct operating costs (dollars per barrel):
Planned turnaround and major maintenance	1.8	[1],[7]	1.2	[1],[7]	1	[1],[7]
Depreciation and amortization	1.41	[1],[7]	1.36	[1],[7]	1.44	[1],[7]
Other manufacturing	4.86	[1],[7],[8]	4.14	[1],[7],[8]	3.15	[1],[7],[8]
Total	8.07	[1],[7]	6.7	[1],[7]	5.59	[1],[7]
Pipeline Transportation Operating Statistics
Inter-refinery transfers	43,000		36,000		25,000
Refining & Marketing | Gulf Coast:
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	1,173,000	[1],[9]	1,159,000	[1],[9]
Sour crude oil throughput percent	64.00%	[1]	65.00%	[1]
WTI-priced crude oil throughput percent	3.00%	[1]	7.00%	[1]
Refined product yields (thousands of barrels per day)	1,199,000	[1],[9]	1,186,000	[1],[9]
Refinery direct operating costs (dollars per barrel):
Planned turnaround and major maintenance	1.82	[1],[7]	1	[1],[7]
Depreciation and amortization	1.15	[1],[7]	1.09	[1],[7]
Other manufacturing	4.73	[1],[7],[8]	3.98	[1],[7],[8]
Total	7.7	[1],[7]	6.07	[1],[7]
Refining & Marketing | Midwest:
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	676,000	[9]	679,000	[9]
Sour crude oil throughput percent	33.00%		35.00%
WTI-priced crude oil throughput percent	44.00%		42.00%
Refined product yields (thousands of barrels per day)	683,000	[9]	686,000	[9]
Refinery direct operating costs (dollars per barrel):
Planned turnaround and major maintenance	1.66	[7]	1.47	[7]
Depreciation and amortization	1.78	[7]	1.74	[7]
Other manufacturing	4.76	[7],[8]	4.21	[7],[8]
Total	8.2	[7]	7.42	[7]
Refining & Marketing | Crude oil refined
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	1,622,000	[1],[5]	1,589,000	[1],[5]	1,195,000	[1],[5]
Refining & Marketing | Crude oil refined | Gulf Coast:
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	991,000	[1],[9]	964,000	[1],[9]
Refining & Marketing | Crude oil refined | Midwest:
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	631,000	[9]	625,000	[9]
Refining & Marketing | Other charge and blendstocks
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	184,000	[1],[5]	213,000	[1],[5]	168,000	[1],[5]
Refining & Marketing | Other charge and blendstocks | Gulf Coast:
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	182,000	[1],[9]	195,000	[1],[9]
Refining & Marketing | Other charge and blendstocks | Midwest:
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	45,000	[9]	54,000	[9]
Refining & Marketing | Gasoline
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	869,000	[1],[6]	921,000	[1],[6]	738,000	[1],[6]
Refining & Marketing | Gasoline | Gulf Coast:
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	508,000	[1],[9]	551,000	[1],[9]
Refining & Marketing | Gasoline | Midwest:
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	361,000	[9]	371,000	[9]
Refining & Marketing | Distillates
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	580,000	[1],[6]	572,000	[1],[6]	433,000	[1],[6]
Refining & Marketing | Distillates | Gulf Coast:
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	368,000	[1],[9]	365,000	[1],[9]
Refining & Marketing | Distillates | Midwest:
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	212,000	[9]	207,000	[9]
Refining & Marketing | Propane
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	35,000	[1],[6]	37,000	[1],[6]	26,000	[1],[6]
Refining & Marketing | Propane | Gulf Coast:
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	23,000	[1],[9]	23,000	[1],[9]
Refining & Marketing | Propane | Midwest:
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	13,000	[9]	14,000	[9]
Refining & Marketing | Feedstocks and special products
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	276,000	[1],[6]	221,000	[1],[6]	109,000	[1],[6]
Refining & Marketing | Feedstocks and special products | Gulf Coast:
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	274,000	[1],[9]	215,000	[1],[9]
Refining & Marketing | Feedstocks and special products | Midwest:
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	43,000	[9]	41,000	[9]
Refining & Marketing | Heavy fuel oil
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	25,000	[1],[6]	31,000	[1],[6]	18,000	[1],[6]
Refining & Marketing | Heavy fuel oil | Gulf Coast:
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	13,000	[1],[9]	19,000	[1],[9]
Refining & Marketing | Heavy fuel oil | Midwest:
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	13,000	[9]	12,000	[9]
Refining & Marketing | Asphalt
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	54,000	[1],[6]	54,000	[1],[6]	62,000	[1],[6]
Refining & Marketing | Asphalt | Gulf Coast:
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	13,000	[1],[9]	13,000	[1],[9]
Refining & Marketing | Asphalt | Midwest:
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	41,000	[9]	41,000	[9]
Speedway
Speedway Operating Statistics(j)
Convenience stores at period-end	2,746	[10]	1,478		1,464
Gasoline and distillate sales (millions of gallons)	3,942,000,000	[10]	3,146,000,000		3,027,000,000
Gasoline and distillate gross margin (dollars per gallon)	0.1775	[10],[11]	0.1441	[11]	0.1318	[11]
Merchandise sales (in millions)	3,611	[10]	3,135		3,058
Merchandise gross margin (in millions)	975	[10]	825		795
Merchandise margin percent	27.00%	[10]	26.30%		26.00%
Same store gasoline sales volume (period over period) percentage	-0.70%	[10]	0.50%		-0.80%
Merchandise sales excluding cigarettes (period over period) percentage	5.00%	[10],[12]	4.30%	[12]	7.00%	[12]
Pipeline Transportation
Pipeline Transportation Operating Statistics
Pipeline throughputs (thousands of barrels per day)	2,119,000	[13]	2,204,000	[13]	2,171,000	[13]
Pipeline Transportation | Crude oil pipelines
Pipeline Transportation Operating Statistics
Pipeline throughputs (thousands of barrels per day)	1,241,000	[13]	1,293,000	[13]	1,191,000	[13]
Pipeline Transportation | Refined products pipelines
Pipeline Transportation Operating Statistics
Pipeline throughputs (thousands of barrels per day)	878,000	[13]	911,000	[13]	980,000	[13]
[1]	Includes the impact of the Galveston Bay Refinery and Related Assets beginning on the February 1, 2013 acquisition date.
[2]	Total average daily volumes of refined product sales to wholesale, branded and retail (Speedway segment) customers.
[3]	Includes intersegment sales.
[4]	Sales revenue less cost of refinery inputs and purchased products, divided by total refinery throughputs. Starting in the fourth quarter of 2013, direct operating costs are no longer included in the Refining & Marketing gross margin and the gross margin is calculated based on total refinery throughput. All prior periods presented have been recalculated to reflect a consistent approach.
[5]	Based on calendar day capacity, which is an annual average that includes downtime for planned maintenance and other normal operating activities.
[6]	Excludes inter-refinery volumes of 43 thousand barrels per day (“mbpd”), 36 mbpd and 25 mbpd for 2014, 2013 and 2012, respectively
[7]	Per barrel of total refinery throughputs.
[8]	Includes utilities, labor, routine maintenance and other operating costs.
[9]	Includes inter-refinery transfer volumes.
[10]	Includes the impact of Hess’ Retail Operations and Related Assets beginning on the September 30, 2014 acquisition date.
[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.