Marathon Petroleum (MPC) 10-Q 2 May 16 2016 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2016	Apr. 29, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus (Q1,Q2,Q3,FY)	Q1
Trading Symbol	MPC
Entity Registrant Name	Marathon Petroleum Corp
Entity Central Index Key	1,510,295
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		529,834,884

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Revenues and other income:
Sales and other operating revenues (including consumer excise taxes)	$ 12,755	$ 17,191
Income from equity method investments	22	15
Net gain on disposal of assets	25	5
Other income	28	29
Total revenues and other income	12,830	17,240
Costs and expenses:
Cost of revenues (excludes items below)	9,701	13,044
Purchases from related parties	107	76
Inventory market valuation charge	15	0
Consumer excise taxes	1,826	1,832
Impairment expense	129	0
Depreciation and amortization	490	363
Selling, general and administrative expenses	378	358
Other taxes	109	97
Total costs and expenses	12,755	15,770
Income from operations	75	1,470
Net interest and other financial income (costs)	(142)	(81)
Income (loss) before income taxes	(67)	1,389
Provision for income taxes	11	486
Net income (loss)	(78)	903
Less net income (loss) attributable to noncontrolling interests	(79)	12
Net income attributable to MPC	$ 1	$ 891
Basic:
Net income attributable to MPC per share	$ 0.003	$ 1.63
Weighted average shares outstanding (in shares)	529	545
Diluted:
Net income attributable to MPC per share	$ 0.003	$ 1.62
Weighted average shares outstanding (in shares)	531	549
Dividends paid (in USD per share)	$ 0.32	$ 0.25

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (78)	$ 903
Defined benefit postretirement and post-employment plans:
Actuarial changes, net of tax of $5 and $5	8	8
Prior service costs, net of tax of $-5 and $-5	(8)	(8)
Other comprehensive income (loss)	0	0
Comprehensive income (loss)	(78)	903
Less comprehensive income (loss) attributable to noncontrolling interests	(79)	12
Comprehensive income attributable to MPC	$ 1	$ 891

Consolidated Statements of Com4

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Actuarial changes, tax	$ 5	$ 5
Prior service costs, tax	$ (5)	$ (5)

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents (MPLX: $4 and $43, respectively)	$ 308	$ 1,127
Receivables, less allowance for doubtful accounts of $11 and $12 (MPLX: $256 and $257, respectively)	2,602	2,927
Inventories (MPLX: $45 and $51, respectively)	4,983	5,225
Other current assets (MPLX: $28 and $50, respectively)	204	192
Total current assets	8,097	9,471
Equity method investments (MPLX: $2,598 and $2,458, respectively)	3,807	3,622
Property, plant and equipment, net (MPLX: $10,195 and $9,997, respectively)	25,319	25,164
Goodwill (MPLX: $2,200 and $2,570, respectively)	3,649	4,019
Other noncurrent assets (MPLX: $531 and $478, respectively)	886	839
Total assets	41,758	43,115
Current liabilities:
Accounts payable (MPLX: $424 and $449, respectively)	4,083	4,743
Payroll and benefits payable (MPLX: $1 and $18, respectively)	302	503
Consumer excise taxes payable (MPLX: $1 and $1, respectively)	459	460
Accrued taxes (MPLX: $23 and $26, respectively)	145	184
Long-term debt due within one year (MPLX: $1 and $1, respectively)	215	29
Other current liabilities (MPLX: $69 and $65, respectively)	391	426
Total current liabilities	5,595	6,345
Long-term debt (MPLX: $4,715 and $5,255, respectively)	11,351	11,896
Deferred income taxes (MPLX: $382 and $378, respectively)	3,356	3,285
Defined benefit postretirement plan obligations	1,216	1,179
Deferred credits and other liabilities (MPLX: $172 and $170, respectively)	746	735
Total liabilities	$ 22,264	$ 23,440
Commitments and contingencies (see Note 22)
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 – 730 million and 729 million shares (par value 0.01 per share, 1 billion shares authorized)	7	7
Held in treasury, at cost – 200 million and 198 million shares	(7,353)	(7,275)
Additional paid-in capital	10,982	11,071
Retained earnings	9,584	9,752
Accumulated other comprehensive loss	(318)	(318)
Total MPC stockholders’ equity	12,902	13,237
Noncontrolling interests	6,592	6,438
Total equity	19,494	19,675
Total liabilities and equity	$ 41,758	$ 43,115

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 11	$ 12
Preferred stock:
Shares issued	0	0
Shares outstanding	0	0
Par value	$ 0.01
Shares authorized	30,000,000
Common stock:
Shares issued	730,000,000	729,000,000
Par value	$ 0.01
Shares authorized	1,000,000,000
Treasury stock	(200,000,000)	(198,000,000)

Consolidated Balance Sheets (MP

Consolidated Balance Sheets (MPLX Parenthetical) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Cash and cash equivalents	$ 308	$ 1,127
Receivables, less allowance for doubtful accounts	2,602	2,927
Inventories	4,983	5,225
Other current assets	204	192
Other current assets	8,097	9,471
Equity method investments	3,807	3,622
Property, plant and equipment, net	25,319	25,164
Goodwill	3,649	4,019
Other noncurrent assets	886	839
Accounts payable	4,083	4,743
Payroll and benefits payable	302	503
Consumer excise taxes payable	459	460
Accrued taxes	145	184
Long-term debt due within one year	215	29
Other current liabilities	391	426
Total long-term debt due after one year	11,351	11,896
Deferred income taxes	3,356	3,285
Defined benefit postretirement plan obligations	1,216	1,179
Deferred credits and other liabilities	746	735
MPLX LP
Cash and cash equivalents	4	43
Receivables, less allowance for doubtful accounts	256	257
Inventories	45	51
Other current assets	28	50
Equity method investments	2,598	2,458
Property, plant and equipment, net	10,195	9,997
Goodwill	2,200	2,570
Other noncurrent assets	531	478
Accounts payable	424	449
Payroll and benefits payable	1	18
Consumer excise taxes payable	1	1
Accrued taxes	23	26
Long-term debt due within one year	1	1
Other current liabilities	69	65
Total long-term debt due after one year	4,715	5,255
Deferred income taxes	382	378
Defined benefit postretirement plan obligations	0	0
Deferred credits and other liabilities	$ 172	$ 170

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating activities:
Net income (loss)	$ (78)	$ 903
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Impairment expense	129	0
Depreciation and amortization	490	363
Inventory market valuation charge	15	0
Pension and other postretirement benefits, net	30	26
Deferred income taxes	(2)	(2)
Net gain on disposal of assets	(25)	(5)
Equity method investments, net	28	2
Changes in the fair value of derivative instruments	(18)	(12)
Changes in:
Current receivables	325	691
Inventories	226	205
Current accounts payable and accrued liabilities	(810)	(939)
All other, net	17	(42)
Net cash provided by operating activities	327	1,190
Investing activities:
Additions to property, plant and equipment	(745)	(389)
Disposal of assets	77	11
Investments – acquisitions, loans and contributions	(66)	(42)
Investments - redemptions, repayments and return of capital	0	1
All other, net	7	31
Net cash used in investing activities	(727)	(388)
Financing activities:
Commercial paper – issued	264	0
Commercial paper - repayments	(76)	0
Long-term debt – borrowings	586	528
Long-term debt – repayments	(1,145)	(421)
Debt issuance costs	(1)	(4)
Issuance of common stock	1	21
Common stock repurchased	(75)	(209)
Dividends paid	(169)	(136)
Issuance of MPLX LP common units	315	0
Distributions to noncontrolling interests	(121)	(9)
All other, net	2	12
Net cash used in financing activities	(419)	(218)
Net increase (decrease) in cash and cash equivalents	(819)	584
Cash and cash equivalents at beginning of period	1,127	1,494
Cash and cash equivalents at end of period	$ 308	$ 2,078

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Millions	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests
Beginning balance at Dec. 31, 2014	$ 11,390	$ 7	$ (6,299)	$ 9,841	$ 7,515	$ (313)	$ 639
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	903				891		12
Dividends declared	(137)				(137)
Distributions to noncontrolling interests	(9)						(9)
Shares repurchased	(209)		(209)
Shares returned - stock based compensation			(4)
Shares issued - stock based compensation				21
Net shares issued - stock based compensation	17
Stock-based compensation	25			25			0
Ending balance at Mar. 31, 2015	11,980	7	(6,512)	9,887	8,269	(313)	642
Beginning balance at Dec. 31, 2015	19,675	7	(7,275)	11,071	9,752	(318)	6,438
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(78)				1		(79)
Dividends declared	(169)				(169)
Distributions to noncontrolling interests	(121)						(121)
Shares repurchased	(75)		(75)
Shares returned - stock based compensation			(3)
Shares issued - stock based compensation				1
Net shares issued - stock based compensation	(2)
Stock-based compensation	17			15			2
Issuance of MPLX LP common units, inclusive of deferred income tax of $8	323			(32)			355
Issuance of MPLX LP common units, tax	8			8
Deferred income tax effect from changes in noncontrolling interest - contribution of inland marine	42			42
Deferred income tax effect from changes in noncontrolling interest - MarkWest Merger	115			115
Other							(3)
Ending balance at Mar. 31, 2016	$ 19,494	$ 7	$ (7,353)	$ 10,982	$ 9,584	$ (318)	$ 6,592

Consolidated Statement of Equit

Consolidated Statement of Equity - Shares - shares shares in Millions	Total	Common Stock	Treasury Stock
Number of common shares issued (beginning balance) at Dec. 31, 2014		726
Number of shares issued - stock-based compensation		2
Number of common shares issued (ending balance) at Mar. 31, 2015		728
Number of shares held in treasury (beginning balance) at Dec. 31, 2014			(179)
Number of shares repurchased	(4)		(5)
Number of shares held in treasury (ending balance) at Mar. 31, 2015			(184)
Number of common shares issued (beginning balance) at Dec. 31, 2015	729	729
Number of shares issued - stock-based compensation		1
Number of common shares issued (ending balance) at Mar. 31, 2016	730	730
Number of shares held in treasury (beginning balance) at Dec. 31, 2015	(198)		(198)
Number of shares repurchased	(2)		(2)
Number of shares held in treasury (ending balance) at Mar. 31, 2016	(200)		(200)

Description of the Business and

Description of the Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2016
Accounting Policies [Abstract]
Description of the Business and Basis of Presentation	Description of the Business and Basis of Presentation Description of the Business— Our business consists of refining and marketing, retail and midstream services conducted primarily in the Midwest, Gulf Coast, East Coast, Northeast 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 9 for additional information about our operations. Basis of Presentation— All significant intercompany transactions and accounts have been eliminated. These interim consolidated financial statements are unaudited; however, in the opinion of our management, these statements reflect all adjustments necessary for a fair statement of the results for the periods reported. All such adjustments are of a normal, recurring nature unless otherwise disclosed. These interim consolidated financial statements, including the notes, have been prepared in accordance with the rules of the SEC applicable to interim period financial statements and do not include all of the information and disclosures required by U.S. GAAP for complete financial statements. These interim consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2015 . The results of operations for the three months ended March 31, 2016 are not necessarily indicative of the results to be expected for the full year. We completed a two-for-one stock split in June 2015. All historical share and per share data included in these consolidated financial statements has been retroactively restated on a post-split basis. In the first quarter of 2016, we revised our segment reporting of the operating results for our inland marine business and our investment in an ocean vessel joint venture, Crowley Ocean Partners LLC (“Crowley Ocean Partners”) in connection with the contribution of our inland marine business to MPLX. See Note 3 for additional information. These operating results are now reported in our Midstream segment. Previously they were reported as part of our Refining & Marketing segment. Comparable prior period information has been recast to reflect our revised segment presentation. See Note 9 for additional information.

Accounting Standards

Accounting Standards	3 Months Ended
	Mar. 31, 2016
Accounting Changes and Error Corrections [Abstract]
Accounting Standards	Accounting Standards Recently Adopted In September 2015, the FASB issued an accounting standard update that eliminates the requirement to restate prior period financial statements for measurement period adjustments for business combinations. This update requires that the cumulative impact of a measurement period adjustment be recognized in the reporting period in which the adjustment is identified. The standard was effective for interim and annual periods beginning after December 15, 2015 with early application permitted. We recognized measurement period adjustments during the three months ended March 31, 2016 as additional analysis was completed on the preliminary purchase price allocation for the acquisition of MarkWest Energy Partners, L.P. (“MarkWest”). See Note 4 for further discussion and detail related to the adjustment. In May 2015, the FASB issued an accounting standard update that eliminates the requirement to categorize in the fair value hierarchy investments that are measured at net asset value using the practical expedient. The standard was effective for fiscal years beginning after December 15, 2015 and interim periods within the fiscal year. Retrospective application is required and early adoption is permitted. Adoption of this standard update in the first quarter of 2016 did not have a material impact on our disclosures. In April 2015, the FASB issued an accounting standard update clarifying whether a customer should account for a cloud computing arrangement as an acquisition of a software license or as a service arrangement by providing characteristics that a cloud computing arrangement must have in order to be accounted for as a software license acquisition. The change was effective for fiscal years and interim periods within those fiscal years beginning after December 15, 2015. Retrospective or prospective application is allowed and early adoption is permitted. We adopted this standard prospectively in the first quarter of 2016 and it did not have a material impact on our consolidated results of operations, financial position or cash flows. In February 2015, the FASB issued an accounting standard update making targeted changes to the current consolidation guidance. The new standard changes the considerations 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 was effective for fiscal years and interim periods within those fiscal years beginning after December 15, 2015. Under the new standard, we continue to consolidate our master limited partnership, MPLX, but it is now considered to be a VIE. The standard update did impact our disclosures for this consolidated VIE, but did not have a material impact on our results of operations, financial position or cash flows. In June 2014, the FASB issued an accounting standard 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 and was adopted in the first quarter of 2015. In addition, the portion of the standard to amend the consolidation model that eliminates the special provisions in the VIE rules for assessing the sufficiency of the equity of a DSE was adopted in the first quarter of 2016. Adoption of this standards update in the first quarter of 2015 and 2016 did not have an impact on our consolidated results of operations, financial position or cash flows. Not Yet Adopted In March 2016, the FASB issued an accounting standard update to simplify some provisions in stock compensation accounting. The areas for simplification of this update involve the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities and classification of the statement of cash flows. This update will be effective for annual reporting periods beginning after December 15, 2016, and interim periods within those years and early adoption is permitted. We do not expect application of this standard to have a material impact on our consolidated financial statements. In March 2016, the FASB issued an accounting standard update eliminating the requirement that an investor retrospectively apply equity method accounting when an investment that it had accounted for by another method initially qualifies for the equity method. This update will be effective for annual reporting periods beginning after December 15, 2016, and interim periods within those years. The guidance will be applied prospectively and early adoption is permitted. We do not expect application of this standard to have a material impact on our consolidated financial statements. In February 2016, the FASB issued an accounting standard update on lease accounting. This update requires lessees to record most leases on their balance sheets. The new standard also requires new disclosures to help financial statement users better understand the amount, timing and uncertainty of cash flows arising from leases. The accounting standard update will be effective on a retrospective or modified retrospective basis for annual reporting periods beginning after December 15, 2018, and interim periods within those years, with early adoption permitted. We are in the process of determining the impact of the new standard on the consolidated financial statements. In January 2016, the FASB issued an accounting standard update requiring unconsolidated equity investments, not accounted for under the equity method, to be measured at fair value with changes in fair value recognized in net income. The update also requires the use of the exit price notion when measuring the fair value of financial instruments for disclosure purposes and the separate presentation of financial assets and liabilities by measurement category and form on the balance sheet and accompanying notes. The update eliminates the requirement to disclose the methods and assumptions used in estimating the fair value of financial instruments measured at amortized cost. Lastly, the update requires separate presentation in other comprehensive income of the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when electing to measure the liability at fair value in accordance with the fair value option for financial instruments. The changes are effective for fiscal years and interim periods within those fiscal years beginning after December 15, 2017. Upon adoption, entities will be required to make a cumulative-effect adjustment to the consolidated results of operations as of the beginning of the first reporting period the guidance is effective. Early adoption is permitted only for the amendment regarding presentation of a liability’s credit risk. We do not expect application of this standard to have a material impact on our consolidated financial statements. In August 2014, the FASB issued an accounting standard 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 standard 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. We do not expect application of this standard to have an impact on our financial reporting. In May 2014, the FASB issued an accounting standard update for revenue recognition. 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 standard update will be effective on a retrospective or modified retrospective basis for annual reporting periods beginning after December 15, 2017, and interim periods within those years, with early adoption permitted, no earlier than January 1, 2017. We are in the process of determining the impact of the new standard on our consolidated financial statements.

MPLX LP

MPLX LP	3 Months Ended
	Mar. 31, 2016
Noncontrolling Interest [Abstract]
MPLX LP	MPLX LP MPLX is a publicly traded master limited partnership formed by us to own, operate, develop and acquire pipelines and other midstream assets related to the transportation and storage of hydrocarbon-based products, including crude oil, refined products, natural gas and NGLs. On December 4, 2015, MPLX and MarkWest completed a merger, whereby MarkWest became a wholly-owned subsidiary of MPLX (the “MarkWest Merger”). MarkWest’s operations include: natural gas gathering, processing and transportation; and NGL gathering, transportation, fractionation, storage and marketing. MPLX’s other assets include a 100 percent interest in MPLX Pipe Line Holdings LLC (“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 cavern in Neal, West Virginia. And effective March 31, 2016 (as described below), MPLX also owns an inland marine business, which is comprised of 18 tow boats and 205 barges and transports primarily crude oil and refined products in the Midwest and Gulf Coast regions of the United States principally for MPC. As of March 31, 2016 , we owned a 25 percent interest in MPLX, including a two percent general partner interest. MPLX is a VIE because the limited partners of MPLX do not have substantive kick-out or substantive participating rights over the general partner. We are the primary beneficiary of MPLX because in addition to significant economic interest, we also have the power, through our 100 percent ownership of the general partner interest, to control the decisions that most significantly impact MPLX. We therefore consolidate MPLX and record a noncontrolling interest for the 75 percent interest owned by the public. The creditors of MPLX do not have recourse to MPC’s general credit through guarantees or other financial arrangements. Contribution of Inland Marine Business to MPLX On March 31, 2016, we contributed our inland marine business to MPLX in exchange for 23 million MPLX common units and 460 thousand general partner units. The number of units we received from MPLX was determined by dividing $600 million by the volume weighted average NYSE price of MPLX common units for the 10 trading days preceding March 14, 2016, pursuant to the Membership Interests Contribution Agreement. We also agreed to waive first-quarter 2016 common unit distributions, IDRs and general partner distributions, with respect to the common units issued in this transaction. The contribution of our inland marine business was accounted for as a transaction between entities under common control and we did not record a gain or loss. ATM Program On March 4, 2016, MPLX filed a prospectus supplement to its shelf registration statement filed with the SEC on March 27, 2015, authorizing the continuous issuance of up to an aggregate of $500 million of common units, in amounts, at prices and on terms to be determined by market conditions and other factors at the time of any offerings (such continuous offering program, or at-the-market program, referred to as the “ATM Program”). MPLX expects to use the net proceeds from sales under the ATM Program for general partnership purposes. During the three months ended March 31, 2016 , MPLX issued an aggregate of 12 million common units under the ATM Program, generating net proceeds of approximately $315 million . As a result of common units issued under the ATM Program during the period, we contributed approximately $6 million to MPLX in exchange for general partner units to maintain our two percent general partner interest. Agreements 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 refined products systems and minimum storage volumes of crude oil, refined products and butane. We also have agreements with MPLX that 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	3 Months Ended
	Mar. 31, 2016
Business Combinations [Abstract]
Acquisitions and Investments	Acquisition and Investments Merger with MarkWest Energy Partners, L.P. On December 4, 2015, MPLX completed the MarkWest Merger. The total value of consideration transferred was $8.61 billion , consisting of $7.33 billion in equity and $1.28 billion in cash. At closing, we made a payment of $1.23 billion to MarkWest common unitholders and the remaining $50 million will be paid in equal amounts in July 2016 and July 2017, respectively, in connection with the conversion of the MPLX Class B units to MPLX common units. Our financial results and operating statistics reflect the results of MarkWest from the date of the MarkWest Merger. The following table summarizes the preliminary purchase price allocation. Subsequent to December 31, 2015 , additional analysis was completed and adjustments were made to the preliminary purchase price allocation as noted in the table below. The estimated fair value of assets acquired and liabilities and noncontrolling interests assumed at the acquisition date as of March 31, 2016 , are as follows: (In millions) As originally reported Adjustments As adjusted Cash and cash equivalents $ 12 $ — $ 12 Receivables 164 — 164 Inventories 33 (1 ) 32 Other current assets 44 — 44 Equity method investments 2,457 143 2,600 Property, plant and equipment, net 8,474 43 8,517 Other noncurrent assets (a) 473 65 538 Total assets acquired 11,657 250 11,907 Accounts payable 322 6 328 Payroll and benefits payable 13 — 13 Accrued taxes 21 — 21 Other current liabilities 44 — 44 Long-term debt 4,567 — 4,567 Deferred income taxes 374 3 377 Deferred credit and other liabilities 151 — 151 Noncontrolling interests 13 — 13 Total liabilities and noncontrolling interest assumed 5,505 9 5,514 Net assets acquired excluding goodwill 6,152 241 6,393 Goodwill 2,454 (241 ) 2,213 Net assets acquired $ 8,606 $ — $ 8,606 (a) The adjustment relates to the intangible asset acquired. Adjustments to the preliminary purchase price stem mainly from additional information obtained by management in the first quarter about facts and circumstances that existed at the acquisition date including updates to forecasted employee benefit costs and capital expenditures, and completion of certain valuations to determine the underlying fair value of certain acquired assets. The adjustment to intangibles mainly relates to a misstatement in the original preliminary purchase price allocation. The correction of the error resulted in a $68 million reduction to the carrying value of goodwill and an offsetting increase of $64 million in intangibles and $2 million in each of equity method investments and property, plant and equipment. Management concluded that the correction of the error is immaterial to the consolidated financial statements of all periods presented. We are still completing our analysis of the final purchase price allocation . The increase to fair value of equity method investments, property plant and equipment, and other noncurrent assets noted above would not have resulted in a material effect to depreciation and amortization or income from equity method investments in the Consolidated Statements of Income for the year ended December 31, 2015, had the fair value adjustments been recorded as of December 4, 2015. The net fair value of the assets acquired and liabilities assumed in connection with the MarkWest Merger was less than the fair value of the total consideration resulting in the recognition of $2.21 billion of goodwill in three reporting units within our Midstream segment, substantially all of which is not deductible for tax purposes. Goodwill represents the complementary aspects of the highly diverse asset base of MarkWest and MPLX that will provide significant additional opportunities across the hydrocarbon value chain. As further discussed in Note 14 , we recorded a goodwill impairment charge based on the implied fair value of goodwill as of the interim impairment analysis date. Therefore, any future adjustments to the purchase price allocation will be offset by adjustments to the impairment expense line item in the Consolidated Statements of Income. Unaudited Pro Forma Financial Information The following unaudited pro forma financial information presents consolidated results assuming the MarkWest Merger occurred on January 1, 2014. The unaudited pro forma financial information does not give effect to potential synergies that could result from the transaction and is not necessarily indicative of the results of future operations. Three Months Ended (In millions, except per share data) 2015 Sales and other operating revenues (including consumer excise taxes) $ 17,652 Net income attributable to MPC 871 Net income attributable to MPC per share – basic $ 1.60 Net income attributable to MPC per share – diluted 1.59 The unaudited 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, adjustments to amortize the fair value adjustment for the debt assumed by MPLX, adjustments to reflect the change in our limited partner interest in MPLX resulting from the MarkWest Merger, as well as the related income tax effects. Investment in Ocean Vessel Joint Venture In September 2015, we acquired a 50 percent ownership interest in a new joint venture with Crowley Maritime Corporation through our investment in Crowley Ocean Partners. The joint venture will operate and charter four new Jones Act product tankers, most of which will be leased to MPC. The new vessels are in various stages of construction with two of them completed and operational prior to the end of the first quarter. Contributions to the joint venture with respect to each vessel will occur at the vessel’s delivery. During 2015, we contributed $72 million in connection with delivery of the first two vessels. The third vessel was delivered April 15, 2016 and the remaining vessel is expected to be delivered by the third quarter of 2016. We account for our ownership interest in Crowley Ocean Partners as an equity method investment. In the first quarter of 2016, we revised our internal reporting of operating results for our investment in Crowley Ocean Partners. These operating results are now reported in our Midstream segment. Previously they were reported as part of our Refining & Marketing segment. Prior periods have been recast to reflect our revised segment presentation. See Note 22 for information on our conditional guarantee of the indebtedness of the joint venture and future contributions to Crowley Ocean Partners. Investment in Pipeline Company 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. We also have the option to increase our ownership interest to approximately 30 percent through additional investments in future system improvements. The anticipated in-service date for the pipeline is likely to be delayed from 2017 to early 2019, which is also likely to increase cost estimates for the project. The project schedule and cost estimates remain under review. We made contributions of $5 million to North Dakota Pipeline Company LLC (“North Dakota Pipeline”) during the three months ended March 31, 2016 and have contributed $292 million since project inception. We account for our interest in North Dakota Pipeline as part of our Midstream segment using the equity method of accounting. See Note 22 for information on future contributions to North Dakota Pipeline.

Variable Interest Entity

Variable Interest Entity	3 Months Ended
	Mar. 31, 2016
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Variable Interest Entity	Variable Interest Entities In addition to MPLX, as described in Note 3 , the following entities are also VIEs. MarkWest Utica EMG On January 1, 2012, MarkWest Utica Operating Company, LLC (“Utica Operating”), a wholly-owned and consolidated subsidiary of MarkWest, and EMG Utica, LLC ("EMG Utica") (together the "Members"), executed agreements to form a joint venture, MarkWest Utica EMG LLC (“MarkWest Utica EMG”), to develop significant natural gas gathering, processing and NGL fractionation, transportation and marketing infrastructure in eastern Ohio. MarkWest has a 60 percent legal ownership interest in MarkWest Utica EMG. MarkWest Utica EMG's inability to fund its planned activities without subordinated financial support qualify it as a VIE. Utica Operating is not deemed to be the primary beneficiary due to EMG Utica’s voting rights on significant matters. We account for our ownership interest in MarkWest Utica EMG as an equity method investment. MPLX receives engineering and construction and administrative management fee revenue and reimbursement for other direct personnel costs for operating MarkWest Utica EMG. Our maximum exposure to loss as a result of our involvement with MarkWest Utica EMG includes our equity investment, any additional capital contribution commitments and any operating expenses incurred by the subsidiary operator in excess of compensation received for the performance of the operating services. Our equity investment in MarkWest Utica EMG at March 31, 2016 was $2.29 billion . Ohio Gathering Ohio Gathering Company, L.L.C. (“Ohio Gathering”) is a subsidiary of MarkWest Utica EMG and is engaged in providing natural gas gathering services in the Utica Shale in eastern Ohio. Ohio Gathering is a joint venture between MarkWest Utica EMG and Summit Midstream Partners, LLC. As of March 31, 2016 , we had a 36 percent indirect ownership interest in Ohio Gathering. As this entity is a subsidiary of MarkWest Utica EMG, which is accounted for as an equity method investment, MPLX reports its portion of Ohio Gathering’s net assets as a component of its investment in MarkWest Utica EMG. MPLX receives engineering and construction and administrative management fee revenue and reimbursement for other direct personnel costs for operating Ohio Gathering.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2016
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Our related parties include: • Centennial Pipeline LLC (“Centennial”), in which we have a 50 percent noncontrolling interest. Centennial owns a refined products pipeline and storage facility. • Crowley Ocean Partners, in which we have a 50 percent noncontrolling interest. Crowley Ocean Partners operates and charters Jones Act product tankers. • Explorer Pipeline Company (“Explorer”), in which we have a 25 percent interest. Explorer owns and operates a refined products pipeline. • Illinois Extension Pipeline Company, LLC (“Illinois Extension Pipeline”), in which we have a 35 percent noncontrolling interest. Illinois Extension Pipeline owns and operates a crude oil 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. • MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C. (“Jefferson Dry Gas”), in which we have a 67 percent noncontrolling interest. Jefferson Dry Gas is engaged in dry natural gas gathering in the county of Jefferson, Ohio. • MarkWest Utica EMG, in which we have a 60 percent noncontrolling interest. MarkWest Utica EMG owns and operates a NGL pipeline and natural gas gathering system. • Ohio Condensate Company, L.L.C. (“Ohio Condensate”), in which we have a 60 percent noncontrolling interest. Ohio Condensate owns and operates wellhead condensate stabilization and gathering services for certain locations within Ohio. • Ohio Gathering, in which we have a 36 percent indirect noncontrolling interest. Ohio Gathering owns, operates and develops midstream gathering infrastructure in southeastern Ohio. • The Andersons Albion Ethanol LLC (“TAAE”), in which we have a 45 percent noncontrolling interest, The Andersons Clymers Ethanol LLC (“TACE”), in which we have a 60 percent noncontrolling interest and The Andersons Marathon Ethanol LLC (“TAME”), in which we have a 67 percent direct and indirect noncontrolling interest. These companies each own and operate 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 $1 million for both the three months ended March 31, 2016 and 2015 . Other income from related parties, which is included in other income on the consolidated statements of income, were $8 million and less than $1 million for the three months ended March 31, 2016 and 2015 , respectively. Other income from related parties consists primarily of fees received for operating transportation assets for our related parties. Purchases from related parties were as follows: Three Months Ended (In millions) 2016 2015 Centennial $ 2 $ — Crowley Ocean Partners 6 — Explorer 2 7 Illinois Extension Pipeline 27 — LOCAP 6 5 LOOP 13 13 Ohio Condensate 3 — TAAE 9 13 TACE 17 16 TAME 20 20 Other equity method investees 2 2 Total $ 107 $ 76 Related party purchases from Centennial consist primarily of refinery feedstocks and refined product transportation costs. Related party purchases from Crowley Ocean Partners consist of leasing equipment primarily used to transport refined products. Related party purchases from Explorer consist primarily of refined product transportation costs. Related party purchases from Illinois Extension Pipeline, LOCAP, LOOP and other equity method investees consist primarily of crude oil transportation costs. Related party purchases from Ohio Condensate consist of processing fees for crude oil and refinery feedstocks. Related party purchases from TAAE, TACE and TAME consist of ethanol purchases. Receivables from related parties, which are included in receivables, less allowance for doubtful accounts on the consolidated balance sheets, were as follows: (In millions) March 31, December 31, Centennial $ 1 $ 1 Jefferson Dry Gas — 2 MarkWest Utica EMG 1 1 Ohio Condensate — 3 Ohio Gathering 3 5 Other equity method investees 2 1 Total $ 7 $ 13 Long-term receivable from Ohio Condensate, which is included in other noncurrent assets on the consolidated balance sheet, was zero at March 31, 2016 and $1 million at December 31, 2015 . Payables to related parties, which are included in accounts payable on the consolidated balance sheets, were as follows: (In millions) March 31, December 31, Centennial $ 1 $ — Explorer 1 1 Illinois Extension Pipeline 10 4 LOCAP 2 2 LOOP 4 5 MarkWest Utica EMG 21 19 Ohio Condensate 3 4 TAAE 1 1 TACE 1 2 TAME 2 3 Other equity method investees 1 1 Total $ 47 $ 42

Income per Common Share

Income per Common Share	3 Months Ended
	Mar. 31, 2016
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. The average number of shares of common stock and per share amounts have been retroactively restated to reflect the two-for-one stock split completed in June 2015. Diluted income per share assumes exercise of certain stock-based compensation awards, provided the effect is not anti-dilutive. MPC grants certain incentive compensation awards to employees and non-employee directors that are considered to be participating securities. Due to the presence of participating securities, we have calculated our earnings per share using the two-class method. Three Months Ended (In millions, except per share data) 2016 2015 Basic earnings per share: Allocation of earnings: Net income attributable to MPC $ 1 $ 891 Income allocated to participating securities — 1 Income available to common stockholders – basic $ 1 $ 890 Weighted average common shares outstanding 529 545 Basic earnings per share $ 0.003 $ 1.63 Diluted earnings per share: Allocation of earnings: Net income attributable to MPC $ 1 $ 891 Income allocated to participating securities — 1 Income available to common stockholders – diluted $ 1 $ 890 Weighted average common shares outstanding 529 545 Effect of dilutive securities 2 4 Weighted average common shares, including dilutive effect 531 549 Diluted earnings per share $ 0.003 $ 1.62 The following table summarizes the shares that were anti-dilutive and, therefore, were excluded from the diluted share calculation. Three Months Ended (In millions) 2016 2015 Shares issued under stock-based compensation plans 3 1

Equity

Equity	3 Months Ended
	Mar. 31, 2016
Equity [Abstract]
Equity	Equity Since January 1, 2012, our board of directors has approved $10.0 billion in total share repurchase authorizations and we have repurchased a total of $7.31 billion of our common stock under these authorizations, leaving $2.69 billion available for repurchases as of March 31, 2016 . Under these authorizations, we have acquired 200 million shares at an average cost per share of $36.71 . We may utilize various methods to effect the repurchases, which could include open market repurchases, negotiated block transactions, accelerated share repurchases or open market solicitations for shares, some of which may be effected through Rule 10b5-1 plans. The timing and amount of future repurchases, if any, will depend upon several factors, including market and business conditions, and such repurchases may be discontinued at any time. Total share repurchases were as follows for the three months ended March 31, 2016 and 2015 : Three Months Ended (In millions, except per share data) 2016 2015 Number of shares repurchased 2 4 Cash paid for shares repurchased $ 75 $ 209 Effective average cost per delivered share $ 43.96 $ 47.51

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2016
Segment Reporting [Abstract]
Segment Information	Segment Information In the first quarter of 2016, we revised our segment reporting of the operating results for our inland marine business and our investment in Crowley Ocean Partners in connection with the contribution of our inland marine business to MPLX. These operating results are now reported in our Midstream segment. Previously they were reported as part of our Refining & Marketing segment. Comparable prior period information has been recast to reflect our revised segment presentation. We have three reportable segments: Refining & Marketing; Speedway; and Midstream. 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 terminals and trucks that we own or operate. We sell refined products to wholesale marketing customers domestically and internationally, to buyers on the spot market, to our Speedway segment and to independent entrepreneurs who operate Marathon ® retail outlets. • Speedway – sells transportation fuels and convenience merchandise in retail markets in the Midwest, East Coast and Southeast regions of the United States. • Midstream – includes the operations of MPLX and certain other related operations. The Midstream segment gathers, processes and transports natural gas; gathers, transports, fractionates, stores and markets NGLs and transports and stores crude oil and refined products. On December 4, 2015, MPLX completed a merger with MarkWest and its results are included in the Midstream segment. Segment information for periods prior to the MarkWest Merger does not include amounts for these operations. See Note 4 . Segment income represents income from operations attributable to the reportable segments. Corporate administrative expenses and costs related to certain non-operating assets are not allocated to the reportable segments. In addition, certain items that affect comparability (as determined by the chief operating decision maker) are not allocated to the reportable segments. (In millions) Refining & Marketing Speedway Midstream Total Three Months Ended March 31, 2016 Revenues: Customer $ 8,406 $ 3,950 $ 399 $ 12,755 Intersegment (a) 2,165 1 193 2,359 Segment revenues $ 10,571 $ 3,951 $ 592 $ 15,114 Segment income (loss) from operations (b) $ (62 ) $ 167 $ 167 $ 272 Income (loss) from equity method investments (1 ) — 23 22 Depreciation and amortization (c) 273 63 140 476 Capital expenditures and investments (d) 243 50 350 643 (In millions) Refining & Marketing Speedway Midstream Total Three Months Ended March 31, 2015 Revenues: Customer $ 12,644 $ 4,531 $ 16 $ 17,191 Intersegment (a) 2,734 — 187 2,921 Segment revenues $ 15,378 $ 4,531 $ 203 $ 20,112 Segment income from operations (b) $ 1,292 $ 168 $ 90 $ 1,550 Income from equity method investments 6 — 9 15 Depreciation and amortization (c) 261 63 26 350 Capital expenditures and investments (d) 223 45 87 355 (a) Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties. (b) Corporate overhead expenses attributable to MPLX are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments. (c) Differences between segment totals and MPC totals represent amounts related to unallocated items and are included in “Items not allocated to segments” in the reconciliation below. (d) Capital expenditures include changes in capital accruals, acquisitions (including any goodwill) and investments in affiliates. The following reconciles segment income from operations to income before income taxes as reported in the consolidated statements of income: Three Months Ended (In millions) 2016 2015 Segment income from operations $ 272 $ 1,550 Items not allocated to segments: Corporate and other unallocated items (a)(b) (67 ) (79 ) Pension settlement expenses (c) (1 ) (1 ) Impairments (d) (129 ) — Net interest and other financial income (costs) (142 ) (81 ) Income before income taxes $ (67 ) $ 1,389 (a) Corporate and other unallocated items consists primarily of MPC’s corporate administrative expenses and costs related to certain non-operating assets. (b) Corporate overhead expenses attributable to MPLX are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments. (c) See Note 20 . (d) See Note 14 . The following reconciles segment capital expenditures and investments to total capital expenditures: Three Months Ended (In millions) 2016 2015 Segment capital expenditures and investments $ 643 $ 355 Less: Investments in equity method investees (a) 209 42 Plus: Items not allocated to segments: Capital expenditures not allocated to segments 24 21 Capitalized interest 17 8 Total capital expenditures (b) $ 475 $ 342 (a) The three months ended March 31, 2016 includes an adjustment of $143 million to the fair value of equity investments acquired in connection with the MarkWest Merger. See Note 4 . (b) Capital expenditures include changes in capital accruals. See Note 18 for a reconciliation of total capital expenditures to additions to property, plant and equipment as reported in the consolidated statements of cash flows.

Other Items

Other Items	3 Months Ended
	Mar. 31, 2016
Other Income and Expenses [Abstract]
Other Items	Other Items Net interest and other financial income (costs) was: Three Months Ended (In millions) 2016 2015 Interest income $ 1 $ 1 Interest expense (a) (153 ) (80 ) Interest capitalized 16 8 Other financial costs (6 ) (10 ) Net interest and other financial income (costs) $ (142 ) $ (81 ) (a) The three months ended March 31, 2016 includes $11 million for the amortization of the discount related to the difference between the fair value and the principal amount of the assumed MarkWest debt.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The combined federal, state and foreign income tax rate was (17) percent and 35 percent for the three months ended March 31, 2016 and 2015 , respectively. The effective tax rate for the three months ended March 31, 2016 was significantly affected by permanent tax differences related to the net loss attributable to noncontrolling interest, including their proportional share of the goodwill impairment charge recorded by MPLX. The net loss attributable to noncontrolling interest reduced the effective rate by 51 percent from the U.S. statutory rate of 35 percent . For the three months ended March 31, 2015 , the effective tax rate is equivalent to the U.S. statutory rate of 35 percent primarily due to certain permanent benefit differences, including the domestic manufacturing deduction, partially offset by state and local tax expense. On March 31, 2016, we contributed our inland marine business to MPLX in exchange for MPLX common units representing limited partner interests and general partner units resulting in an increase in MPC’s controlling interest in MPLX. A decrease in MPC’s deferred tax liabilities of $42 million directly related to this change in ownership of the underlying assets of MPLX was recorded with an offsetting increase to additional paid-in capital. During the first quarter of 2016, MPC’s deferred tax liabilities increased $115 million for an out of period adjustment to update the preliminary tax effects recorded in 2015 related to the MarkWest Merger, which was recorded with an offsetting decrease to additional paid-in capital. The impact of the adjustment was not material to the Consolidated Balance Sheet as of December 31, 2015. We are continuously undergoing examination of our income tax returns, which have been completed for our U.S. federal and state income tax returns through the 2009 and 2003 tax years, respectively. We had $11 million of unrecognized tax benefits as of March 31, 2016 . Pursuant to our tax sharing agreement with Marathon Oil Corporation (“Marathon Oil”), the unrecognized tax benefits related to pre-spinoff operations for which Marathon Oil was the taxpayer remain the responsibility of Marathon Oil and we have indemnified Marathon Oil accordingly. See Note 22 for indemnification information.

Inventories

Inventories	3 Months Ended
	Mar. 31, 2016
Inventory Disclosure [Abstract]
Inventories	Inventories (In millions) March 31, December 31, Crude oil and refinery feedstocks $ 2,044 $ 2,180 Refined products 2,761 2,804 Materials and supplies 399 438 Merchandise 164 173 Lower of cost or market reserve (385 ) (370 ) Total $ 4,983 $ 5,225 Inventories are carried at the lower of cost or market value. Costs of crude oil, refinery feedstocks and refined products 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 values. The December 31, 2015 lower of cost or market reserve was reversed due to the sale of inventory quantities that gave rise to the 2015 reserve. A new lower of cost or market reserve of $385 million was established as of March 31, 2016 based on prices at that time. The effect of the change in lower of cost or market reserve was a $15 million charge to cost of revenues for the three months ended March 31, 2016 . Based on movements of refined product prices, future inventory valuation adjustments could have a negative or positive effect to earnings. Such losses are subject to reversal in subsequent periods if prices recover. The cost of inventories of crude oil and refinery feedstocks, refined products and merchandise is determined primarily under the LIFO method. There were no material liquidations of LIFO inventories for the three months ended March 31, 2016 and 2015 .

Property, Plant and Equipment

Property, Plant and Equipment	3 Months Ended
	Mar. 31, 2016
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment (In millions) March 31, December 31, Refining & Marketing $ 18,631 $ 18,396 Speedway 5,108 5,067 Midstream 11,707 11,379 Corporate and Other 769 762 Total 36,215 35,604 Less accumulated depreciation 10,896 10,440 Property, plant and equipment, net $ 25,319 $ 25,164

Goodwill

Goodwill	3 Months Ended
	Mar. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
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 of the net assets of the reporting unit. During the first quarter of 2016, MPLX, our consolidated subsidiary, determined that an interim impairment analysis of the goodwill recorded in connection with the MarkWest Merger was necessary based on consideration of a number of first quarter events and circumstances, including i) continued deterioration of near term commodity prices as well as longer term pricing trends, ii) recent guidance on reductions to forecasted capital spending, the slowing of drilling activity and the resulting reduced production growth forecasts released or communicated by MPLX’s producer customers and iii) increases in the cost of capital. The combination of these factors was considered to be a triggering event requiring an interim impairment test. Based on the first step of the interim goodwill impairment analysis, the fair value for the three reporting units to which goodwill was assigned in connection with the MarkWest Merger was less than their respective carrying value. In step two of the impairment analysis, the implied fair values of the goodwill were compared to the carrying values within those reporting units. Based on this assessment, it was determined that goodwill was impaired in two of the reporting units. Accordingly, MPLX recorded an impairment charge of approximately $129 million in the first quarter of 2016. The fair value of the reporting units for the interim goodwill impairment analysis was determined based on applying the discounted cash flow method, which is an income approach, and the guideline public company method, which is a market approach. The discounted cash flow fair value estimate is based on known or knowable information at the interim measurement date. The significant assumptions that were used to develop the estimates of the fair values under the discounted cash flow method include management’s best estimates of the expected future results and discount rates, which ranged from 10.5 percent to 11.5 percent . Fair value determinations require considerable judgment and are sensitive to changes in underlying assumptions and factors. As a result, there can be no assurance that the estimates and assumptions made for purposes of the interim goodwill impairment test will prove to be an accurate prediction of the future. The changes in the carrying amount of goodwill for the three months ended March 31, 2016 were as follows: (In millions) Refining & Marketing Speedway Midstream Total Balance at December 31, 2015 $ 539 $ 853 $ 2,627 $ 4,019 Purchase price allocation adjustments (a) — — (241 ) (241 ) Impairment — — (129 ) (129 ) Balance at March 31, 2016 $ 539 $ 853 $ 2,257 $ 3,649 (a) See Note 4 for further discussion on purchase price allocation adjustments.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2016
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 March 31, 2016 and December 31, 2015 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. March 31, 2016 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 $ 67 $ 1 $ 1 $ (67 ) $ 2 $ 72 Other assets 2 — — N/A 2 — Total assets at fair value $ 69 $ 1 $ 1 $ (67 ) $ 4 $ 72 Commodity derivative instruments, liabilities $ 107 $ — $ 1 $ (107 ) $ 1 $ — Embedded derivatives in commodity contracts (c) — — 34 — 34 — Contingent consideration, liability (d) — — 324 N/A 324 — Total liabilities at fair value $ 107 $ — $ 359 $ (107 ) $ 359 $ — December 31, 2015 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 $ 104 $ 2 $ 7 $ (62 ) $ 51 $ — Other assets 2 — — N/A 2 — Total assets at fair value $ 106 $ 2 $ 7 $ (62 ) $ 53 $ — Commodity derivative instruments, liabilities $ 39 $ — $ — $ (39 ) $ — $ — Embedded derivatives in commodity contracts (c) — — 32 — 32 — Contingent consideration, liability (d) — — 317 N/A 317 — Total liabilities at fair value $ 39 $ — $ 349 $ (39 ) $ 349 $ — (a) Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of March 31, 2016 , cash collateral of $40 million was netted with the mark-to-market derivative liabilities. As of December 31, 2015 , $23 million was netted with mark-to-market derivative assets. (b) We have no derivative contracts that are subject to master netting arrangements that are reflected gross on the balance sheet. (c) Includes $6 million and $5 million classified as current at March 31, 2016 and December 31, 2015 , respectively. (d) Includes $200 million and $196 million classified as current at March 31, 2016 and December 31, 2015 , respectively. Commodity derivatives in Level 1 are exchange-traded contracts for crude oil and refined products measured at fair value with a market approach using the close-of-day settlement prices for the market. Commodity derivatives are covered under master netting agreements with an unconditional right to offset. Collateral deposits in futures commission merchant accounts covered by master netting agreements related to Level 1 commodity derivatives are classified as Level 1 in the fair value hierarchy. Commodity derivatives in Level 2 include crude oil and natural gas swap contracts and are measured at fair value with a market approach. The valuations are based on the appropriate commodity prices and contain no significant unobservable inputs. LIBO Rates are an observable input for the measurement of these derivative contracts. The measurements for commodity contracts contain observable inputs in the form of forward prices based on WTI crude oil prices; and Columbia Appalachia, Henry Hub, PEPL and Houston Ship Channel natural gas prices. Level 3 instruments include OTC NGL contracts and embedded derivatives in commodity contracts. The fair value calculation for these Level 3 instruments used significant unobservable inputs including: (1) NGL prices interpolated and extrapolated due to inactive markets ranging from $0.17 to $3.37 per gallon, (2) electricity prices ranging from $21.34 to $44.27 per megawatt hour and (3) the probability of renewal of 50 percent for the first five -year term and 75 percent for the second five -year term of the gas purchase agreement and the related keep-whole processing agreement. For these contracts, increases in forward NGL prices result in a decrease in the fair value of the derivative assets and an increase in the fair value of the derivative liabilities. The forward prices for the individual NGL products generally increase or decrease in a positive correlation with one another. The embedded derivative liability relates to a natural gas purchase agreement embedded in a keep‑whole processing agreement. Increases or decreases in forward NGL prices result in an increase or decrease in the fair value of the embedded derivative. An increase in the probability of renewal would result in an increase in the fair value of the related embedded derivative liability. The contingent consideration represents the fair value as of March 31, 2016 and December 31, 2015 of the remaining amount we expect to pay to BP related to the earnout provision associated with our 2013 acquisition of BP’s refinery in Texas City, Texas and related logistics and marketing assets. We refer to these assets as the “Galveston Bay Refinery and Related Assets.” The fair value of the remaining 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 earnout 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 commencing in 2014. 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 monthly refinery throughput volumes; (2) a range of internal and external monthly crack spread forecasts from approximately $9 to $16 per barrel; and (3) a range of risk-adjusted discount rates from four percent to 9 percent . An increase or decrease in crack spread forecasts or refinery throughput volume expectations may result in a corresponding increase or decrease in the fair value. Increases to the fair value as a result of increasing forecasts for both of these unobservable inputs, however, are limited as the earnout payment is subject to annual caps. An increase or decrease in the discount rate may result in a decrease or increase to the fair value, respectively. The fair value of the contingent consideration is reassessed each quarter, with changes in fair value recorded in cost of revenues. During the second quarter of 2016, we paid BP $200 million for the third year’s contingent earnout. Including this second quarter payment, we have paid BP approximately $569 million in total leaving $131 million remaining under the total cap of $700 million . The following is a reconciliation of the beginning and ending balances recorded for liabilities classified as Level 3 in the fair value hierarchy. Three Months Ended (In millions) 2016 2015 Beginning balance $ 342 $ 478 Unrealized and realized losses included in net income 12 12 Settlements of derivative instruments 4 — Ending balance $ 358 $ 490 We held Level 3 derivative instruments during the three months ended March 31, 2016 which were acquired with the MarkWest Merger, but we did not hold any Level 3 derivative instruments during the three months ended March 31, 2015 . See Note 16 for the income statement impacts of our derivative instruments. There was an unrealized loss of $5 million in the three months ended March 31, 2016 related to derivatives. There was an unrealized loss of $7 million and $12 million in the three months ended March 31, 2016 and 2015 , respectively, related to the contingent consideration. 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. Three Months Ended March 31, 2016 2015 (In millions) Fair Value Impairment Fair Value Impairment Goodwill $ — $ 129 $ — $ — See Note 14 for additional information on the goodwill impairment. Fair Values – Reported The following table summarizes financial instruments on the basis of their nature, characteristics and risk at March 31, 2016 and December 31, 2015 , excluding the derivative financial instruments and contingent consideration reported above. March 31, 2016 December 31, 2015 (In millions) Fair Value Carrying Value Fair Value Carrying Value Financial assets: Investments $ 30 $ 2 $ 33 $ 2 Other 35 35 35 33 Total financial assets $ 65 $ 37 $ 68 $ 35 Financial liabilities: Long-term debt (a) $ 11,086 $ 11,276 $ 11,366 $ 11,628 Deferred credits and other liabilities 140 138 136 135 Total financial liabilities $ 11,226 $ 11,414 $ 11,502 $ 11,763 (a) Excludes capital leases and debt issuance costs, however, includes amount classified as debt due within one year. 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 a liability related to SMR, a payable for merger cash consideration due to MPLX’s Class B unitholders to be paid upon conversion, insurance liabilities and environmental remediation liabilities. Fair value of fixed-rate long-term debt is measured using a market approach, based upon the average of quotes from major financial institutions and a third-party service for our debt. Because these quotes cannot be independently verified to the market, they are considered Level 3 inputs. Fair value of variable-rate long-term debt approximates the carrying value.

Derivatives

Derivatives	3 Months Ended
	Mar. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives	Derivatives For further information regarding the fair value measurement of derivative instruments, including any effect of master netting agreements or collateral, see Note 15 . We do not designate any of our commodity derivative instruments as hedges for accounting purposes. Derivatives that are not designated as accounting hedges may include commodity derivatives used to hedge price risk on (1) inventories, (2) fixed price sales of refined products, (3) the acquisition of foreign-sourced crude oil, (4) the acquisition of ethanol for blending with refined products, (5) the sale of NGLs, (6) the purchase of natural gas and (7) the purchase of electricity. 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 March 31, 2016 and December 31, 2015 : (In millions) March 31, 2016 Balance Sheet Location Asset Liability Commodity derivatives Other current assets $ 69 $ 107 Other current liabilities — 7 Deferred credits and other liabilities (a) — 28 (In millions) December 31, 2015 Balance Sheet Location Asset Liability Commodity derivatives Other current assets $ 113 $ 39 Other current liabilities — 5 Deferred credits and other liabilities (a) — 27 (a) Includes embedded derivatives. The tables below summarize open commodity derivative contracts for crude oil, natural gas and refined products as of March 31, 2016 . Position Total Barrels (In thousands) Crude oil (a) Exchange-traded Long 25,142 Exchange-traded Short (30,048 ) OTC Short (83 ) (a ) 83 percent of the exchange-traded contracts expire in the second quarter of 2016 . Position MMbtu Natural Gas OTC Long 745,826 Position Total Gallons (In thousands) Refined Products (a) Exchange-traded Long 241,500 Exchange-traded Short (137,424 ) OTC Short (55,759 ) (a ) 100 percent of the exchange-traded contracts expire in the second quarter of 2016 . The following table summarizes the effect of all commodity derivative instruments in our consolidated statements of income: Gain (Loss) (In millions) Three Months Ended March 31, Income Statement Location 2016 2015 Sales and other operating revenues $ 6 $ 14 Cost of revenues (61 ) 45 Total $ (55 ) $ 59

Debt

Debt	3 Months Ended
	Mar. 31, 2016
Debt Disclosure [Abstract]
Debt	Debt Our outstanding borrowings at March 31, 2016 and December 31, 2015 consisted of the following: (In millions) March 31, December 31, Marathon Petroleum Corporation: Commercial paper $ 188 $ — Bank revolving credit facility due 2017 — — Term loan agreement due 2019 700 700 Senior notes, 2.700% due December 2018 600 600 Senior notes, 3.400% due December 2020 650 650 Senior notes, 5.125% due March 2021 1,000 1,000 Senior notes, 3.625%, due September 2024 750 750 Senior notes, 6.500%, due March 2041 1,250 1,250 Senior notes, 4.750%, due September 2044 800 800 Senior notes, 5.850% due December 2045 250 250 Senior notes, 5.000%, due September 2054 400 400 MPLX LP: MPLX term loan facility due 2019 250 250 MPLX bank revolving credit facility due 2020 326 877 MPLX senior notes, 5.500%, due February 2023 710 710 MPLX senior notes, 4.500%, due July 2023 989 989 MPLX senior notes, 4.875%, due December 2024 1,149 1,149 MPLX senior notes, 4.000%, due February 2025 500 500 MPLX senior notes, 4.875%, due June 2025 1,189 1,189 MarkWest senior notes, 4.500% - 5.500%, due 2023 - 2025 63 63 Capital lease obligations due 2016-2028 340 348 Trade receivables securitization facility due December 2016 — — Total 12,104 12,475 Unamortized debt issuance costs (50 ) (51 ) Unamortized discount (a) (488 ) (499 ) Amounts due within one year (215 ) (29 ) Total long-term debt due after one year $ 11,351 $ 11,896 (a) Includes $453 million and $464 million discount as of March 31, 2016 and December 31, 2015 , respectively, related to the difference between the fair value and the principal amount of the assumed MarkWest debt. Commercial Paper - On February 26, 2016, we established a commercial paper program that allows us to have a maximum of $2.0 billion in commercial paper outstanding, with maturities up to 397 days from the date of issuance. We do not intend to have outstanding commercial paper borrowings in excess of available capacity under our bank revolving credit facility. During the three months ended March 31, 2016 , we borrowed $264 million and repaid $76 million under the commercial paper program. At March 31, 2016 , we had $188 million of commercial paper outstanding with a weighted average interest rate of 0.89 percent . These outstanding borrowings are included in debt due within one year. There were no borrowings or letters of credit outstanding under the MPC bank revolving credit facility at March 31, 2016 . During the three months ended March 31, 2016 , we borrowed $280 million under the trade receivables securitization facility at an average interest rate of 1.3 percent and repaid $280 million of these borrowings. At March 31, 2016 , we had no amounts outstanding under our trade receivables securitization facility. During the three months ended March 31, 2016 , MPLX borrowed $306 million under the MPLX bank revolving credit facility at an average interest rate of 1.9 percent , per annum, and repaid $857 million of the outstanding borrowings. At March 31, 2016 , MPLX had $326 million borrowings and $8 million letters of credit outstanding under the MPLX bank revolving credit facility, resulting in total availability of $1.7 billion .

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	3 Months Ended
	Mar. 31, 2016
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information Three Months Ended (In millions) 2016 2015 Net cash provided by operating activities included: Interest paid (net of amounts capitalized) $ 160 $ 128 Net income taxes paid to (refunded from) taxing authorities (128 ) 160 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: Three Months Ended (In millions) 2016 2015 Additions to property, plant and equipment per consolidated statements of cash flows $ 745 $ 389 Decrease in capital accruals (137 ) (47 ) Total capital expenditures before acquisitions 608 342 Acquisitions (a) (133 ) — Total capital expenditures $ 475 $ 342 (a) The three months ended March 31, 2016 includes adjustments to the fair values of the property, plant and equipment, intangibles and goodwill acquired in connection with the MarkWest Merger. See Note 4 .

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	3 Months Ended
	Mar. 31, 2016
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, 2014 $ (217 ) $ (104 ) $ 4 $ 4 $ (313 ) Other comprehensive income (loss) before reclassifications (1 ) (1 ) — — (2 ) Amounts reclassified from accumulated other comprehensive loss: Amortization – prior service credit (a) (12 ) (1 ) — — (13 ) – actuarial loss (a) 13 3 — — 16 – settlement loss (a) 1 — — — 1 Tax effect (1 ) (1 ) — — (2 ) Other comprehensive income (loss) — — — — — Balance as of March 31, 2015 $ (217 ) $ (104 ) $ 4 $ 4 $ (313 ) (In millions) Pension Benefits Other Benefits Gain on Cash Flow Hedge Workers Compensation Total Balance as of December 31, 2015 $ (255 ) $ (70 ) $ 4 $ 3 $ (318 ) Other comprehensive income (loss) before reclassifications — — — — — Amounts reclassified from accumulated other comprehensive loss: Amortization – prior service credit (a) (11 ) (1 ) — — (12 ) – actuarial loss (a) 10 1 — — 11 – settlement loss (a) 1 — — — 1 Tax effect — — — — — Other comprehensive income (loss) — — — — — Balance as of March 31, 2016 $ (255 ) $ (70 ) $ 4 $ 3 $ (318 ) (a) These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 20 .

Defined Benefit Pension and Oth

Defined Benefit Pension and Other Postretirement Plans	3 Months Ended
	Mar. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Defined Benefit Pension and Other Postretirement Plans	Defined Benefit Pension and Other Postretirement Plans The following summarizes the components of net periodic benefit costs: Three Months Ended March 31, Pension Benefits Other Benefits (In millions) 2016 2015 2016 2015 Components of net periodic benefit cost: Service cost $ 28 $ 23 $ 8 $ 8 Interest cost 19 18 9 8 Expected return on plan assets (25 ) (26 ) — — Amortization – prior service credit (11 ) (12 ) (1 ) (1 ) – actuarial loss 10 13 1 3 – settlement loss 1 1 — — Net periodic benefit cost $ 22 $ 17 $ 17 $ 18 During the three months ended March 31, 2016 , we made no contributions to our funded pension plans. We have no required funding for 2016, but may make voluntary contributions at our discretion. Benefit payments related to unfunded pension and other postretirement benefit plans were $2 million and $7 million , respectively, during the three months ended March 31, 2016 . During the three months ended March 31, 2016 and 2015 , we determined that certain of our pension plans’ lump sum payments to employees retiring in the respective years will exceed the plans’ total service and interest costs for the year. Settlement losses are required to be recorded when lump sum payments exceed total service and interest costs. As a result, during the three months ended March 31, 2016 and 2015 , we recorded pension settlement expenses of $1 million related to our lump sum payments made during both the first three months of 2016 and 2015 .

Stock-Based Compensation Plans

Stock-Based Compensation Plans	3 Months Ended
	Mar. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation Plans	Stock-Based Compensation Plans Stock Option Awards The following table presents a summary of our stock option award activity for the three months ended March 31, 2016 : Number of Shares Weighted Average Exercise Price Outstanding at December 31, 2015 8,724,631 $ 27.16 Granted 934,611 34.63 Exercised (44,137 ) 16.30 Forfeited, canceled or expired (6,134 ) 48.52 Outstanding at March 31, 2016 9,608,971 27.92 The grant date fair value of stock option awards granted during the three months ended March 31, 2016 was $9.97 per share. The fair value of stock options granted to our employees is estimated on the date of the grant using the Black Scholes option-pricing model, which employs various assumptions. Restricted Stock Awards The following table presents a summary of restricted stock award activity for the three months ended March 31, 2016 : 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, 2015 1,074,543 $ 47.70 513,220 $ 24.59 Granted 142,698 34.93 10,804 45.42 RS’s Vested/RSU’s Issued (106,788 ) 44.63 — — Forfeited (16,362 ) 47.92 — — Outstanding at March 31, 2016 1,094,091 46.33 524,024 25.02 Performance Unit Awards The following table presents a summary of the activity for performance unit awards to be settled in shares for the three months ended March 31, 2016 : Number of Units Weighted Average Grant Date Fair Value Outstanding at December 31, 2015 6,145,442 $ 0.92 Granted 2,329,500 0.57 Exercised (1,764,792 ) 0.95 Canceled (314,972 ) 0.93 Outstanding at March 31, 2016 6,395,178 0.78 The performance unit awards granted during the three months ended March 31, 2016 have a grant date fair value of $0.57 per unit, as calculated using a Monte Carlo valuation model. MPLX Awards During the three months ended March 31, 2016 , MPLX granted equity-based compensation awards under the MPLX LP 2012 Incentive Compensation Plan. The compensation expense for these awards is not material to our consolidated financial statements.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies We are the subject of, or a party to, a number of pending or threatened legal actions, contingencies and commitments involving a variety of matters, including laws and regulations relating to the environment. Some of these matters are discussed below. For matters for which we have not recorded an accrued liability, we are unable to estimate a range of possible loss because the issues involved have not been fully developed through pleadings and discovery. However, the ultimate resolution of some of these contingencies could, individually or in the aggregate, be material. Environmental matters —We are subject to federal, state, local and foreign laws and regulations relating to the environment. These laws generally provide for control of pollutants released into the environment and require responsible parties to undertake remediation of hazardous waste disposal sites and certain other locations including presently or formerly owned or operated retail marketing sites. Penalties may be imposed for noncompliance. At March 31, 2016 and December 31, 2015 , accrued liabilities for remediation totaled $166 million and $163 million , respectively. It is not presently possible to estimate the ultimate amount of all remediation costs that might be incurred or the penalties if any that may be imposed. Receivables for recoverable costs from certain states, under programs to assist companies in clean-up efforts related to underground storage tanks at presently or formerly owned or operated retail marketing sites, were $68 million and $70 million at March 31, 2016 and December 31, 2015 , 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. Litigation Relating to the MarkWest Merger —In July 2015, a purported class action lawsuit asserting claims challenging the MarkWest Merger was filed in the Court of Chancery of the State of Delaware by a purported unitholder of MarkWest. In August 2015, two similar putative class action lawsuits were filed in the Court of Chancery of the State of Delaware by plaintiffs who purport to be unitholders of MarkWest. On September 9, 2015, these lawsuits were consolidated into one action pending in the Court of Chancery of the State of Delaware, now captioned In re MarkWest Energy Partners, L.P. Unitholder Litigation . On October 1, 2015, the plaintiffs filed a consolidated complaint against the individual members of the board of directors of MarkWest Energy GP, L.L.C. (the “MarkWest GP Board”), MPLX, MPLX GP, MPC and Sapphire Holdco LLC, a wholly-owned subsidiary of MPLX, asserting in connection with the MarkWest Merger and related disclosures that, among other things, (i) the MarkWest GP Board breached its duties in approving the MarkWest Merger with MPLX and (ii) MPC, MPLX, MPLX GP, and Sapphire Holdco LLC aided and abetted such breaches. On February 4, 2016, the Court approved a stipulation and proposed order to dismiss all claims with prejudice as to the named plaintiffs, but the Court retained jurisdiction to adjudicate an application for a mootness fee by the plaintiffs’ counsel for an award of attorneys’ fees and reimbursement of expenses. On March 28, 2016, the plaintiffs filed an application for reimbursement of approximately $2 million of legal fees and expenses. We intend to vigorously defend against any application for a mootness fee and do not expect the resolution of such matter to have a material adverse effect. MarkWest Environmental Proceeding – On July 6, 2015, representatives from the EPA and the United States Department of Justice entered a MarkWest Liberty Midstream & Resources, L.L.C., a wholly-owned subsidiary of MPLX (“MarkWest Liberty Midstream”) pipeline launcher/receiver site utilized for pipeline maintenance operations in Washington County, Pennsylvania pursuant to a search warrant issued by a magistrate of the United States District Court for the Western District of Pennsylvania. The government has presented MarkWest Liberty Midstream with subpoenas to provide documents related to its pipeline and compressor facilities located in Pennsylvania. MarkWest Liberty Midstream is providing information in response to the subpoenas and related requests for information from EPA, state and other agencies, and is in discussions with the agencies regarding issues associated with its operations of, and any permit related obligations for, its gathering facilities in the region. Immediately following the July 6, 2015 search, MarkWest Liberty Midstream commenced its own assessment of its operations of launcher/receiver facilities. MarkWest Liberty Midstream’s review to date has determined that MarkWest Liberty Midstream’s operations have been conducted in a manner fully protective of its employees and the public, and that other than potentially having to obtain certain permits at a relatively small number of individual sites, MarkWest Liberty has operated in substantial compliance with applicable laws and regulations. It is possible that, in connection with any potential or asserted civil or criminal enforcement action associated with this matter, MarkWest Liberty Midstream will incur material assessments, penalties or fines, incur material defense costs and expenses, be required to modify operations or construction activities which could increase operating costs and capital expenditures, or be subject to other obligations or restrictions that could restrict or prohibit our activities, any or all of which could adversely affect our results of operations, financial position or cash flows. The amount of any potential assessments, penalties, fines, restrictions, requirements, modifications, costs or expenses that may be incurred in connection with any potential enforcement action cannot be reasonably estimated or determined at this time. Other Lawsuits —In May 2015, the Kentucky attorney general filed a lawsuit against our wholly-owned subsidiary, Marathon Petroleum Company LP (“MPC LP”) in the United States District Court for the Western District of Kentucky asserting claims under federal and state antitrust statutes, the Kentucky Consumer Protection Act, and state common law. The complaint, as amended in July 2015, alleges that MPC LP used deed restrictions, supply agreements with customers and exchange agreements with competitors to unreasonably restrain trade in areas within Kentucky and seeks declaratory relief, unspecified damages, civil penalties, restitution and disgorgement of profits. At this early stage, the ultimate outcome of this litigation remains uncertain, and neither the likelihood of an unfavorable outcome nor the ultimate liability, if any, can be determined, and we are unable to estimate a reasonably possible loss (or range of loss) for this matter. We intend to vigorously defend ourselves in this matter. 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 also a party to a number of other lawsuits and other proceedings arising in the ordinary course of business. While the ultimate outcome and impact to us cannot be predicted with certainty, we believe that the resolution of these other lawsuits and proceedings will not have a material adverse effect on our consolidated financial position, results of operations or cash flows. Guarantees— We have provided certain guarantees, direct and indirect, of the indebtedness of other companies. Under the terms of most of these guarantee arrangements, we would be required to perform should the guaranteed party fail to fulfill its obligations under the specified arrangements. In addition to these financial guarantees, we also have various performance guarantees related to specific agreements. Guarantees related to indebtedness of equity method investees —We hold interests in an offshore oil port, LOOP, and a crude oil pipeline system, LOCAP. Both LOOP and LOCAP have secured various project financings with throughput and deficiency agreements. Under the agreements, we are required to advance funds if the investees are unable to service their debt. Any such advances are considered prepayments of future transportation charges. The duration of the agreements vary but tend to follow the terms of the underlying debt, which extend through 2037 . Our maximum potential undiscounted payments under these agreements for the debt principal totaled $172 million as of March 31, 2016 . We hold an interest in a refined products pipeline through our investment in Centennial, and have guaranteed our portion of 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 $33 million as of March 31, 2016 . In connection with our 50 percent ownership in Crowley Ocean Partners, we have agreed to conditionally guarantee our portion of the obligations of the joint venture and its subsidiaries under a senior secured term loan agreement. The term loan agreement provides for loans of up to $325 million to finance the acquisition of four product tankers. MPC’s liability under the guarantee for each vessel is conditioned upon the occurrence of certain events, including if we cease to maintain an investment grade credit rating or the charter for the relevant product tanker ceases to be in effect and is not replaced by a charter with an investment grade company on certain defined commercial terms. As of March 31, 2016 , our maximum potential undiscounted payments under this agreement for debt principal associated with the delivery of the first two vessels totaled $81 million . Marathon Oil indemnifications— In conjunction with our spinoff from Marathon Oil, we have entered into arrangements with Marathon Oil providing indemnities and guarantees with recorded values of $3 million as of March 31, 2016 , which consist of unrecognized tax benefits related to MPC, its consolidated subsidiaries and the refining, marketing and transportation business operations prior to our spinoff which are not already reflected in the unrecognized tax benefits described in Note 11 , and other contingent liabilities Marathon Oil may incur related to taxes. Furthermore, the separation and distribution agreement and other agreements with Marathon Oil to effect our spinoff provide for cross-indemnities between Marathon Oil and us. In general, Marathon Oil is required to indemnify us for any liabilities relating to Marathon Oil’s historical oil and gas exploration and production operations, oil sands mining operations and integrated gas operations, and we are required to indemnify Marathon Oil for any liabilities relating to Marathon Oil’s historical refining, marketing and transportation operations. The terms of these indemnifications are indefinite and the amounts are not capped. Other guarantees —We have entered into other guarantees with maximum potential undiscounted payments totaling $89 million as of March 31, 2016 , 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 and contingencies— At March 31, 2016 , our contractual commitments to acquire property, plant and equipment and advance funds to equity method investees totaled $1.7 billion , which includes $331 million of contingent consideration associated with the acquisition of the Galveston Bay Refinery and Related Assets, $625 million for contributions to North Dakota Pipeline and $69 million for contributions to Crowley Ocean Partners. See Note 4 for additional information on our investments in North Dakota Pipeline and Crowley Ocean Partners. See Note 15 for additional information on the contingent consideration. Certain natural gas processing and gathering arrangements require us to construct new natural gas processing plants, natural gas gathering pipelines and NGL pipelines and contain certain fees and charges if specified construction milestones are not achieved for reasons other than force majeure. In certain cases, certain producers may have the right to cancel the processing arrangements if there are significant delays that are not due to force majeure. As of March 31, 2016 , management does not believe there are any indications that we will not be able to meet the construction milestones, that force majeure does not apply, or that such fees and charges will otherwise be triggered.

Subsequent Event

Subsequent Event	3 Months Ended
	Mar. 31, 2016
Subsequent Events [Abstract]
Subsequent Event	Subsequent Event On April 27, 2016, MPLX entered into an agreement for the private placement of $1 billion of newly authorized 6.5 percent Series A Convertible Preferred Units (the “Preferred Units”) at a price of $32.50 per unit or approximately 30.8 million units. The Preferred Units will be entitled to receive an annual distribution from MPLX, which will initially equal $2.1125 per unit. The Preferred Units are convertible into MPLX common units on a one for one basis after three years, at the purchasers’ option, and after four years at MPLX’s option, subject to certain conditions. Closing of the transaction is scheduled to occur in May 2016. The net proceeds after deducting offering and transaction expenses are expected to be approximately $984 million .

Supplementary Statistics

Supplementary Statistics	3 Months Ended
	Mar. 31, 2016
Text Block [Abstract]
Supplementary Statistics	Supplementary Statistics (Unaudited) Three Months Ended (In millions) 2016 2015 Income from Operations by segment Refining & Marketing (a) $ (62 ) $ 1,292 Speedway 167 168 Midstream (a)(b) 167 90 Items not allocated to segments: Corporate and other unallocated items (a)(b) (67 ) (79 ) Pension settlement expenses (1 ) (1 ) Impairments (129 ) — Income from operations $ 75 $ 1,470 Capital Expenditures and Investments (c) Refining & Marketing (a) $ 243 $ 223 Speedway 50 45 Midstream (a) 350 87 Corporate and Other (d) 41 29 Total $ 684 $ 384 (a) We revised our operating segment presentation in the first quarter of 2016 in connection with the contribution of our inland marine business to MPLX; our inland marine business, which was previously included in Refining & Marketing, is now included in Midstream. Comparable prior period information has been recast to reflect our revised segment presentation. (b) Corporate overhead expenses attributable to MPLX are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments. (c) Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates. (d) Includes capitalized interest of $17 million and $8 million for the three months ended March 31, 2016 and 2015 , respectively. Supplementary Statistics (Unaudited) Three Months Ended 2016 2015 MPC Consolidated Refined Product Sales Volumes (mbpd) (a) 2,158 2,246 Refining & Marketing Operating Statistics Refining & Marketing refined product sales volume (mbpd) (b) 2,148 2,233 Refining & Marketing gross margin (dollars per barrel) (c)(d) $ 9.98 $ 16.14 Crude oil capacity utilization percent (e) 89 97 Refinery throughputs (mbpd): (f) Crude oil refined 1,603 1,672 Other charge and blendstocks 171 180 Total 1,774 1,852 Sour crude oil throughput percent 61 56 WTI-priced crude oil throughput percent 18 20 Refined product yields (mbpd): (f) Gasoline 899 911 Distillates 571 553 Propane 32 36 Feedstocks and special products 234 298 Heavy fuel oil 30 30 Asphalt 44 50 Total 1,810 1,878 Refinery direct operating costs (dollars per barrel): (g) Planned turnaround and major maintenance $ 2.43 $ 0.79 Depreciation and amortization 1.54 1.42 Other manufacturing (h) 4.14 4.26 Total $ 8.11 $ 6.47 Refining & Marketing Operating Statistics By Region - Gulf Coast Refinery throughputs (mbpd): (i) Crude oil refined 991 1,031 Other charge and blendstocks 217 179 Total 1,208 1,210 Sour crude oil throughput percent 75 70 WTI-priced crude oil throughput percent 3 5 Refined product yields (mbpd): (i) Gasoline 533 523 Distillates 375 342 Propane 25 25 Feedstocks and special products 280 307 Heavy fuel oil 18 15 Asphalt 8 14 Total 1,239 1,226 Refinery direct operating costs (dollars per barrel): (g) Planned turnaround and major maintenance $ 2.62 $ 0.80 Depreciation and amortization 1.17 1.14 Other manufacturing (h) 3.74 3.99 Total $ 7.53 $ 5.93 Supplementary Statistics (Unaudited) Three Months Ended 2016 2015 Refining & Marketing Operating Statistics By Region – Midwest Refinery throughputs (mbpd): (i) Crude oil refined 612 641 Other charge and blendstocks 36 36 Total 648 677 Sour crude oil throughput percent 39 34 WTI-priced crude oil throughput percent 42 43 Refined product yields (mbpd): (i) Gasoline 366 388 Distillates 196 211 Propane 9 13 Feedstocks and special products 34 23 Heavy fuel oil 12 16 Asphalt 36 36 Total 653 687 Refinery direct operating costs (dollars per barrel): (g) Planned turnaround and major maintenance $ 1.76 $ 0.73 Depreciation and amortization 2.03 1.85 Other manufacturing (h) 4.36 4.51 Total $ 8.15 $ 7.09 Speedway Operating Statistics Convenience stores at period-end 2,771 2,753 Gasoline and distillate sales (millions of gallons) 1,483 1,432 Gasoline and distillate gross margin (dollars per gallon) (j) $ 0.1682 $ 0.1970 Merchandise sales (in millions) $ 1,152 $ 1,111 Merchandise gross margin (in millions) $ 330 $ 311 Merchandise gross margin percent 29.0 % 28.0 % Same store gasoline sales volume (period over period) 1.0 % (1.2 %) Same store merchandise sales (period over period) (k) 3.1 % 6.2 % Midstream Operating Statistics Crude oil and refined product pipeline throughputs (mbpd) (l) 2,181 2,107 Gathering system throughput (MMcf/d) (m) 3,345 Natural gas processed (MMcf/d) (m) 5,636 C2 (ethane) + NGLs (natural gas liquids) fractionated (mbpd) (m) 312 (a) Total average daily volumes of refined product sales to wholesale, branded and retail (Speedway segment) customers. (b) Includes intersegment sales. (c) Sales revenue less cost of refinery inputs and purchased products, divided by total refinery throughputs. (d) Excludes the lower of cost or market inventory valuation charge of $15 million for the first quarter of 2016. (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 82 mbpd and 35 mbpd for the three months ended March 31, 2016 and 2015 , respectively. (g) Per barrel of total refinery throughputs. (h) Includes utilities, labor, routine maintenance and other operating costs. (i) Includes inter-refinery transfer volumes. (j) The price paid by consumers less the cost of refined products, including transportation, consumer excise taxes and bankcard processing fees, divided by gasoline and distillate sales volume. (k) Excludes cigarettes. Same store sales comparison includes only locations owned at least 13 months. (l) On owned common-carrier pipelines, excluding equity method investments. (m) Includes amounts related to unconsolidated equity method investments. Includes the results of the MarkWest assets beginning on the Dec. 4, 2015 acquisition date.

Description of the Business a35

Description of the Business and Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2016
Accounting Policies [Abstract]
Use of estimates	These interim consolidated financial statements are unaudited; however, in the opinion of our management, these statements reflect all adjustments necessary for a fair statement of the results for the periods reported. All such adjustments are of a normal, recurring nature unless otherwise disclosed. These interim consolidated financial statements, including the notes, have been prepared in accordance with the rules of the SEC applicable to interim period financial statements and do not include all of the information and disclosures required by U.S. GAAP for complete financial statements.
Inventories	Inventories are carried at the lower of cost or market value. Costs of crude oil, refinery feedstocks and refined products 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 values. The December 31, 2015 lower of cost or market reserve was reversed due to the sale of inventory quantities that gave rise to the 2015 reserve. A new lower of cost or market reserve of $385 million was established as of March 31, 2016 based on prices at that time. The effect of the change in lower of cost or market reserve was a $15 million charge to cost of revenues for the three months ended March 31, 2016 . Based on movements of refined product prices, future inventory valuation adjustments could have a negative or positive effect to earnings. Such losses are subject to reversal in subsequent periods if prices recover. The cost of inventories of crude oil and refinery feedstocks, refined products and merchandise is determined primarily under the LIFO method.
Derivative instruments	Derivatives that are not designated as accounting hedges may include commodity derivatives used to hedge price risk on (1) inventories, (2) fixed price sales of refined products, (3) the acquisition of foreign-sourced crude oil, (4) the acquisition of ethanol for blending with refined products, (5) the sale of NGLs, (6) the purchase of natural gas and (7) the purchase of electricity.
Stock-based compensation arrangements	The fair value of stock options granted to our employees is estimated on the date of the grant using the Black Scholes option-pricing model, which employs various assumptions.

Acquisitions and Investments (

Acquisitions and Investments (Tables)	3 Months Ended
	Mar. 31, 2016
Business Combinations [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	(In millions) As originally reported Adjustments As adjusted Cash and cash equivalents $ 12 $ — $ 12 Receivables 164 — 164 Inventories 33 (1 ) 32 Other current assets 44 — 44 Equity method investments 2,457 143 2,600 Property, plant and equipment, net 8,474 43 8,517 Other noncurrent assets (a) 473 65 538 Total assets acquired 11,657 250 11,907 Accounts payable 322 6 328 Payroll and benefits payable 13 — 13 Accrued taxes 21 — 21 Other current liabilities 44 — 44 Long-term debt 4,567 — 4,567 Deferred income taxes 374 3 377 Deferred credit and other liabilities 151 — 151 Noncontrolling interests 13 — 13 Total liabilities and noncontrolling interest assumed 5,505 9 5,514 Net assets acquired excluding goodwill 6,152 241 6,393 Goodwill 2,454 (241 ) 2,213 Net assets acquired $ 8,606 $ — $ 8,606 (a) The adjustment relates to the intangible asset acquired.
Business Acquisition, Pro Forma Information [Table Text Block]	Unaudited Pro Forma Financial Information The following unaudited pro forma financial information presents consolidated results assuming the MarkWest Merger occurred on January 1, 2014. The unaudited pro forma financial information does not give effect to potential synergies that could result from the transaction and is not necessarily indicative of the results of future operations. Three Months Ended (In millions, except per share data) 2015 Sales and other operating revenues (including consumer excise taxes) $ 17,652 Net income attributable to MPC 871 Net income attributable to MPC per share – basic $ 1.60 Net income attributable to MPC per share – diluted 1.59

Related Party Transactions (Tab

Related Party Transactions (Tables)	3 Months Ended
	Mar. 31, 2016
Related Party Transactions [Abstract]
Purchases From Related Parties	Purchases from related parties were as follows: Three Months Ended (In millions) 2016 2015 Centennial $ 2 $ — Crowley Ocean Partners 6 — Explorer 2 7 Illinois Extension Pipeline 27 — LOCAP 6 5 LOOP 13 13 Ohio Condensate 3 — TAAE 9 13 TACE 17 16 TAME 20 20 Other equity method investees 2 2 Total $ 107 $ 76
Receivables From Related Parties	Receivables from related parties, which are included in receivables, less allowance for doubtful accounts on the consolidated balance sheets, were as follows: (In millions) March 31, December 31, Centennial $ 1 $ 1 Jefferson Dry Gas — 2 MarkWest Utica EMG 1 1 Ohio Condensate — 3 Ohio Gathering 3 5 Other equity method investees 2 1 Total $ 7 $ 13
Payables To Related Parties	Payables to related parties, which are included in accounts payable on the consolidated balance sheets, were as follows: (In millions) March 31, December 31, Centennial $ 1 $ — Explorer 1 1 Illinois Extension Pipeline 10 4 LOCAP 2 2 LOOP 4 5 MarkWest Utica EMG 21 19 Ohio Condensate 3 4 TAAE 1 1 TACE 1 2 TAME 2 3 Other equity method investees 1 1 Total $ 47 $ 42

Income per Common Share (Tables

Income per Common Share (Tables)	3 Months Ended
	Mar. 31, 2016
Earnings Per Share [Abstract]
Summary of Earnings Per Common Share	MPC grants certain incentive compensation awards to employees and non-employee directors that are considered to be participating securities. Due to the presence of participating securities, we have calculated our earnings per share using the two-class method. Three Months Ended (In millions, except per share data) 2016 2015 Basic earnings per share: Allocation of earnings: Net income attributable to MPC $ 1 $ 891 Income allocated to participating securities — 1 Income available to common stockholders – basic $ 1 $ 890 Weighted average common shares outstanding 529 545 Basic earnings per share $ 0.003 $ 1.63 Diluted earnings per share: Allocation of earnings: Net income attributable to MPC $ 1 $ 891 Income allocated to participating securities — 1 Income available to common stockholders – diluted $ 1 $ 890 Weighted average common shares outstanding 529 545 Effect of dilutive securities 2 4 Weighted average common shares, including dilutive effect 531 549 Diluted earnings per share $ 0.003 $ 1.62
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]	The following table summarizes the shares that were anti-dilutive and, therefore, were excluded from the diluted share calculation. Three Months Ended (In millions) 2016 2015 Shares issued under stock-based compensation plans 3 1

Equity (Tables)

Equity (Tables)	3 Months Ended
	Mar. 31, 2016
Equity [Abstract]
Share Repurchases	Total share repurchases were as follows for the three months ended March 31, 2016 and 2015 : Three Months Ended (In millions, except per share data) 2016 2015 Number of shares repurchased 2 4 Cash paid for shares repurchased $ 75 $ 209 Effective average cost per delivered share $ 43.96 $ 47.51

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2016
Segment Reporting [Abstract]
Income From Operations Attributable To Operating Segments	(In millions) Refining & Marketing Speedway Midstream Total Three Months Ended March 31, 2016 Revenues: Customer $ 8,406 $ 3,950 $ 399 $ 12,755 Intersegment (a) 2,165 1 193 2,359 Segment revenues $ 10,571 $ 3,951 $ 592 $ 15,114 Segment income (loss) from operations (b) $ (62 ) $ 167 $ 167 $ 272 Income (loss) from equity method investments (1 ) — 23 22 Depreciation and amortization (c) 273 63 140 476 Capital expenditures and investments (d) 243 50 350 643 (In millions) Refining & Marketing Speedway Midstream Total Three Months Ended March 31, 2015 Revenues: Customer $ 12,644 $ 4,531 $ 16 $ 17,191 Intersegment (a) 2,734 — 187 2,921 Segment revenues $ 15,378 $ 4,531 $ 203 $ 20,112 Segment income from operations (b) $ 1,292 $ 168 $ 90 $ 1,550 Income from equity method investments 6 — 9 15 Depreciation and amortization (c) 261 63 26 350 Capital expenditures and investments (d) 223 45 87 355 (a) Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties. (b) Corporate overhead expenses attributable to MPLX are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments. (c) Differences between segment totals and MPC totals represent amounts related to unallocated items and are included in “Items not allocated to segments” in the reconciliation below. (d) Capital expenditures include changes in capital accruals, acquisitions (including any goodwill) and investments in affiliates.
Reconciliation Of Segment Income From Operations To Income Before Income Taxes	The following reconciles segment income from operations to income before income taxes as reported in the consolidated statements of income: Three Months Ended (In millions) 2016 2015 Segment income from operations $ 272 $ 1,550 Items not allocated to segments: Corporate and other unallocated items (a)(b) (67 ) (79 ) Pension settlement expenses (c) (1 ) (1 ) Impairments (d) (129 ) — Net interest and other financial income (costs) (142 ) (81 ) Income before income taxes $ (67 ) $ 1,389 (a) Corporate and other unallocated items consists primarily of MPC’s corporate administrative expenses and costs related to certain non-operating assets. (b) Corporate overhead expenses attributable to MPLX are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments. (c) See Note 20 . (d) See Note 14 .
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures	The following reconciles segment capital expenditures and investments to total capital expenditures: Three Months Ended (In millions) 2016 2015 Segment capital expenditures and investments $ 643 $ 355 Less: Investments in equity method investees (a) 209 42 Plus: Items not allocated to segments: Capital expenditures not allocated to segments 24 21 Capitalized interest 17 8 Total capital expenditures (b) $ 475 $ 342 (a) The three months ended March 31, 2016 includes an adjustment of $143 million to the fair value of equity investments acquired in connection with the MarkWest Merger. See Note 4 . (b) Capital expenditures include changes in capital accruals. See Note 18 for a reconciliation of total capital expenditures to additions to property, plant and equipment as reported in the consolidated statements of cash flows.

Other Items (Tables)

Other Items (Tables)	3 Months Ended
	Mar. 31, 2016
Other Income and Expenses [Abstract]
Net Interest And Other Financial Income (Costs)	Net interest and other financial income (costs) was: Three Months Ended (In millions) 2016 2015 Interest income $ 1 $ 1 Interest expense (a) (153 ) (80 ) Interest capitalized 16 8 Other financial costs (6 ) (10 ) Net interest and other financial income (costs) $ (142 ) $ (81 ) (a) The three months ended March 31, 2016 includes $11 million for the amortization of the discount related to the difference between the fair value and the principal amount of the assumed MarkWest debt.

Inventories (Tables)

Inventories (Tables)	3 Months Ended
	Mar. 31, 2016
Inventory Disclosure [Abstract]
Summary Of Inventories	(In millions) March 31, December 31, Crude oil and refinery feedstocks $ 2,044 $ 2,180 Refined products 2,761 2,804 Materials and supplies 399 438 Merchandise 164 173 Lower of cost or market reserve (385 ) (370 ) Total $ 4,983 $ 5,225

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	3 Months Ended
	Mar. 31, 2016
Property, Plant and Equipment [Abstract]
Summary Of Property, Plant And Equipment	(In millions) March 31, December 31, Refining & Marketing $ 18,631 $ 18,396 Speedway 5,108 5,067 Midstream 11,707 11,379 Corporate and Other 769 762 Total 36,215 35,604 Less accumulated depreciation 10,896 10,440 Property, plant and equipment, net $ 25,319 $ 25,164

Goodwill (Tables)

Goodwill (Tables)	3 Months Ended
	Mar. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The changes in the carrying amount of goodwill for the three months ended March 31, 2016 were as follows: (In millions) Refining & Marketing Speedway Midstream Total Balance at December 31, 2015 $ 539 $ 853 $ 2,627 $ 4,019 Purchase price allocation adjustments (a) — — (241 ) (241 ) Impairment — — (129 ) (129 ) Balance at March 31, 2016 $ 539 $ 853 $ 2,257 $ 3,649 (a) See Note 4 for further discussion on purchase price allocation adjustments.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2016
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 March 31, 2016 and December 31, 2015 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. March 31, 2016 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 $ 67 $ 1 $ 1 $ (67 ) $ 2 $ 72 Other assets 2 — — N/A 2 — Total assets at fair value $ 69 $ 1 $ 1 $ (67 ) $ 4 $ 72 Commodity derivative instruments, liabilities $ 107 $ — $ 1 $ (107 ) $ 1 $ — Embedded derivatives in commodity contracts (c) — — 34 — 34 — Contingent consideration, liability (d) — — 324 N/A 324 — Total liabilities at fair value $ 107 $ — $ 359 $ (107 ) $ 359 $ — December 31, 2015 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 $ 104 $ 2 $ 7 $ (62 ) $ 51 $ — Other assets 2 — — N/A 2 — Total assets at fair value $ 106 $ 2 $ 7 $ (62 ) $ 53 $ — Commodity derivative instruments, liabilities $ 39 $ — $ — $ (39 ) $ — $ — Embedded derivatives in commodity contracts (c) — — 32 — 32 — Contingent consideration, liability (d) — — 317 N/A 317 — Total liabilities at fair value $ 39 $ — $ 349 $ (39 ) $ 349 $ — (a) Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of March 31, 2016 , cash collateral of $40 million was netted with the mark-to-market derivative liabilities. As of December 31, 2015 , $23 million was netted with mark-to-market derivative assets. (b) We have no derivative contracts that are subject to master netting arrangements that are reflected gross on the balance sheet. (c) Includes $6 million and $5 million classified as current at March 31, 2016 and December 31, 2015 , respectively. (d) Includes $200 million and $196 million classified as current at March 31, 2016 and December 31, 2015 , respectively.
Reconciliation of Net Beginning and Ending Balances Recorded for Net Assets and Liabilities Classified as Level 3	The following is a reconciliation of the beginning and ending balances recorded for liabilities classified as Level 3 in the fair value hierarchy. Three Months Ended (In millions) 2016 2015 Beginning balance $ 342 $ 478 Unrealized and realized losses included in net income 12 12 Settlements of derivative instruments 4 — Ending balance $ 358 $ 490
Fair Value Measurements, 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. Three Months Ended March 31, 2016 2015 (In millions) Fair Value Impairment Fair Value Impairment Goodwill $ — $ 129 $ — $ —
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 March 31, 2016 and December 31, 2015 , excluding the derivative financial instruments and contingent consideration reported above. March 31, 2016 December 31, 2015 (In millions) Fair Value Carrying Value Fair Value Carrying Value Financial assets: Investments $ 30 $ 2 $ 33 $ 2 Other 35 35 35 33 Total financial assets $ 65 $ 37 $ 68 $ 35 Financial liabilities: Long-term debt (a) $ 11,086 $ 11,276 $ 11,366 $ 11,628 Deferred credits and other liabilities 140 138 136 135 Total financial liabilities $ 11,226 $ 11,414 $ 11,502 $ 11,763 (a) Excludes capital leases and debt issuance costs, however, includes amount classified as debt due within one year.

Derivatives (Tables)

Derivatives (Tables)	3 Months Ended
	Mar. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Classification of Fair Values of Derivative Instruments, Excluding Cash Collateral	The following table presents the gross fair values of derivative instruments, excluding cash collateral, and where they appear on the consolidated balance sheets as of March 31, 2016 and December 31, 2015 : (In millions) March 31, 2016 Balance Sheet Location Asset Liability Commodity derivatives Other current assets $ 69 $ 107 Other current liabilities — 7 Deferred credits and other liabilities (a) — 28 (In millions) December 31, 2015 Balance Sheet Location Asset Liability Commodity derivatives Other current assets $ 113 $ 39 Other current liabilities — 5 Deferred credits and other liabilities (a) — 27 (a) Includes embedded derivatives.
Open Commodity Derivative Contracts	The tables below summarize open commodity derivative contracts for crude oil, natural gas and refined products as of March 31, 2016 . Position Total Barrels (In thousands) Crude oil (a) Exchange-traded Long 25,142 Exchange-traded Short (30,048 ) OTC Short (83 ) (a ) 83 percent of the exchange-traded contracts expire in the second quarter of 2016 . Position MMbtu Natural Gas OTC Long 745,826 Position Total Gallons (In thousands) Refined Products (a) Exchange-traded Long 241,500 Exchange-traded Short (137,424 ) OTC Short (55,759 ) (a ) 100 percent of the exchange-traded contracts expire in the second quarter of 2016 .
Effect of Commodity Derivative Instruments in Statements of Income	The following table summarizes the effect of all commodity derivative instruments in our consolidated statements of income: Gain (Loss) (In millions) Three Months Ended March 31, Income Statement Location 2016 2015 Sales and other operating revenues $ 6 $ 14 Cost of revenues (61 ) 45 Total $ (55 ) $ 59

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2016
Debt Disclosure [Abstract]
Outstanding Borrowings	Our outstanding borrowings at March 31, 2016 and December 31, 2015 consisted of the following: (In millions) March 31, December 31, Marathon Petroleum Corporation: Commercial paper $ 188 $ — Bank revolving credit facility due 2017 — — Term loan agreement due 2019 700 700 Senior notes, 2.700% due December 2018 600 600 Senior notes, 3.400% due December 2020 650 650 Senior notes, 5.125% due March 2021 1,000 1,000 Senior notes, 3.625%, due September 2024 750 750 Senior notes, 6.500%, due March 2041 1,250 1,250 Senior notes, 4.750%, due September 2044 800 800 Senior notes, 5.850% due December 2045 250 250 Senior notes, 5.000%, due September 2054 400 400 MPLX LP: MPLX term loan facility due 2019 250 250 MPLX bank revolving credit facility due 2020 326 877 MPLX senior notes, 5.500%, due February 2023 710 710 MPLX senior notes, 4.500%, due July 2023 989 989 MPLX senior notes, 4.875%, due December 2024 1,149 1,149 MPLX senior notes, 4.000%, due February 2025 500 500 MPLX senior notes, 4.875%, due June 2025 1,189 1,189 MarkWest senior notes, 4.500% - 5.500%, due 2023 - 2025 63 63 Capital lease obligations due 2016-2028 340 348 Trade receivables securitization facility due December 2016 — — Total 12,104 12,475 Unamortized debt issuance costs (50 ) (51 ) Unamortized discount (a) (488 ) (499 ) Amounts due within one year (215 ) (29 ) Total long-term debt due after one year $ 11,351 $ 11,896 (a) Includes $453 million and $464 million discount as of March 31, 2016 and December 31, 2015 , respectively, related to the difference between the fair value and the principal amount of the assumed MarkWest debt.

Supplemental Cash Flow Inform48

Supplemental Cash Flow Information (Tables)	3 Months Ended
	Mar. 31, 2016
Supplemental Cash Flow Elements [Abstract]
Summary of Supplemental Cash Flow Information	Three Months Ended (In millions) 2016 2015 Net cash provided by operating activities included: Interest paid (net of amounts capitalized) $ 160 $ 128 Net income taxes paid to (refunded from) taxing authorities (128 ) 160
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: Three Months Ended (In millions) 2016 2015 Additions to property, plant and equipment per consolidated statements of cash flows $ 745 $ 389 Decrease in capital accruals (137 ) (47 ) Total capital expenditures before acquisitions 608 342 Acquisitions (a) (133 ) — Total capital expenditures $ 475 $ 342 (a) The three months ended March 31, 2016 includes adjustments to the fair values of the property, plant and equipment, intangibles and goodwill acquired in connection with the MarkWest Merger. See Note 4 .

Accumulated Other Comprehensi49

Accumulated Other Comprehensive Loss (Tables)	3 Months Ended
	Mar. 31, 2016
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, 2014 $ (217 ) $ (104 ) $ 4 $ 4 $ (313 ) Other comprehensive income (loss) before reclassifications (1 ) (1 ) — — (2 ) Amounts reclassified from accumulated other comprehensive loss: Amortization – prior service credit (a) (12 ) (1 ) — — (13 ) – actuarial loss (a) 13 3 — — 16 – settlement loss (a) 1 — — — 1 Tax effect (1 ) (1 ) — — (2 ) Other comprehensive income (loss) — — — — — Balance as of March 31, 2015 $ (217 ) $ (104 ) $ 4 $ 4 $ (313 ) (In millions) Pension Benefits Other Benefits Gain on Cash Flow Hedge Workers Compensation Total Balance as of December 31, 2015 $ (255 ) $ (70 ) $ 4 $ 3 $ (318 ) Other comprehensive income (loss) before reclassifications — — — — — Amounts reclassified from accumulated other comprehensive loss: Amortization – prior service credit (a) (11 ) (1 ) — — (12 ) – actuarial loss (a) 10 1 — — 11 – settlement loss (a) 1 — — — 1 Tax effect — — — — — Other comprehensive income (loss) — — — — — Balance as of March 31, 2016 $ (255 ) $ (70 ) $ 4 $ 3 $ (318 ) (a) These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 20 .

Defined Benefit Pension and O50

Defined Benefit Pension and Other Postretirement Plans (Tables)	3 Months Ended
	Mar. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Components of Net Periodic Benefit Costs	The following summarizes the components of net periodic benefit costs: Three Months Ended March 31, Pension Benefits Other Benefits (In millions) 2016 2015 2016 2015 Components of net periodic benefit cost: Service cost $ 28 $ 23 $ 8 $ 8 Interest cost 19 18 9 8 Expected return on plan assets (25 ) (26 ) — — Amortization – prior service credit (11 ) (12 ) (1 ) (1 ) – actuarial loss 10 13 1 3 – settlement loss 1 1 — — Net periodic benefit cost $ 22 $ 17 $ 17 $ 18

Stock-Based Compensation Plans

Stock-Based Compensation Plans (Tables)	3 Months Ended
	Mar. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Stock Option Award Activity	The following table presents a summary of our stock option award activity for the three months ended March 31, 2016 : Number of Shares Weighted Average Exercise Price Outstanding at December 31, 2015 8,724,631 $ 27.16 Granted 934,611 34.63 Exercised (44,137 ) 16.30 Forfeited, canceled or expired (6,134 ) 48.52 Outstanding at March 31, 2016 9,608,971 27.92
Summary of Restricted Stock Award Activity	The following table presents a summary of restricted stock award activity for the three months ended March 31, 2016 : 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, 2015 1,074,543 $ 47.70 513,220 $ 24.59 Granted 142,698 34.93 10,804 45.42 RS’s Vested/RSU’s Issued (106,788 ) 44.63 — — Forfeited (16,362 ) 47.92 — — Outstanding at March 31, 2016 1,094,091 46.33 524,024 25.02
Schedule of Performance Unit Awards	The following table presents a summary of the activity for performance unit awards to be settled in shares for the three months ended March 31, 2016 : Number of Units Weighted Average Grant Date Fair Value Outstanding at December 31, 2015 6,145,442 $ 0.92 Granted 2,329,500 0.57 Exercised (1,764,792 ) 0.95 Canceled (314,972 ) 0.93 Outstanding at March 31, 2016 6,395,178 0.78

Supplementary Statistics (Table

Supplementary Statistics (Tables)	3 Months Ended
	Mar. 31, 2016
Text Block [Abstract]
Supplementary Statistics	Supplementary Statistics (Unaudited) Three Months Ended (In millions) 2016 2015 Income from Operations by segment Refining & Marketing (a) $ (62 ) $ 1,292 Speedway 167 168 Midstream (a)(b) 167 90 Items not allocated to segments: Corporate and other unallocated items (a)(b) (67 ) (79 ) Pension settlement expenses (1 ) (1 ) Impairments (129 ) — Income from operations $ 75 $ 1,470 Capital Expenditures and Investments (c) Refining & Marketing (a) $ 243 $ 223 Speedway 50 45 Midstream (a) 350 87 Corporate and Other (d) 41 29 Total $ 684 $ 384 (a) We revised our operating segment presentation in the first quarter of 2016 in connection with the contribution of our inland marine business to MPLX; our inland marine business, which was previously included in Refining & Marketing, is now included in Midstream. Comparable prior period information has been recast to reflect our revised segment presentation. (b) Corporate overhead expenses attributable to MPLX are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments. (c) Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates. (d) Includes capitalized interest of $17 million and $8 million for the three months ended March 31, 2016 and 2015 , respectively.
Operating Statistics	Supplementary Statistics (Unaudited) Three Months Ended 2016 2015 MPC Consolidated Refined Product Sales Volumes (mbpd) (a) 2,158 2,246 Refining & Marketing Operating Statistics Refining & Marketing refined product sales volume (mbpd) (b) 2,148 2,233 Refining & Marketing gross margin (dollars per barrel) (c)(d) $ 9.98 $ 16.14 Crude oil capacity utilization percent (e) 89 97 Refinery throughputs (mbpd): (f) Crude oil refined 1,603 1,672 Other charge and blendstocks 171 180 Total 1,774 1,852 Sour crude oil throughput percent 61 56 WTI-priced crude oil throughput percent 18 20 Refined product yields (mbpd): (f) Gasoline 899 911 Distillates 571 553 Propane 32 36 Feedstocks and special products 234 298 Heavy fuel oil 30 30 Asphalt 44 50 Total 1,810 1,878 Refinery direct operating costs (dollars per barrel): (g) Planned turnaround and major maintenance $ 2.43 $ 0.79 Depreciation and amortization 1.54 1.42 Other manufacturing (h) 4.14 4.26 Total $ 8.11 $ 6.47 Refining & Marketing Operating Statistics By Region - Gulf Coast Refinery throughputs (mbpd): (i) Crude oil refined 991 1,031 Other charge and blendstocks 217 179 Total 1,208 1,210 Sour crude oil throughput percent 75 70 WTI-priced crude oil throughput percent 3 5 Refined product yields (mbpd): (i) Gasoline 533 523 Distillates 375 342 Propane 25 25 Feedstocks and special products 280 307 Heavy fuel oil 18 15 Asphalt 8 14 Total 1,239 1,226 Refinery direct operating costs (dollars per barrel): (g) Planned turnaround and major maintenance $ 2.62 $ 0.80 Depreciation and amortization 1.17 1.14 Other manufacturing (h) 3.74 3.99 Total $ 7.53 $ 5.93 Supplementary Statistics (Unaudited) Three Months Ended 2016 2015 Refining & Marketing Operating Statistics By Region – Midwest Refinery throughputs (mbpd): (i) Crude oil refined 612 641 Other charge and blendstocks 36 36 Total 648 677 Sour crude oil throughput percent 39 34 WTI-priced crude oil throughput percent 42 43 Refined product yields (mbpd): (i) Gasoline 366 388 Distillates 196 211 Propane 9 13 Feedstocks and special products 34 23 Heavy fuel oil 12 16 Asphalt 36 36 Total 653 687 Refinery direct operating costs (dollars per barrel): (g) Planned turnaround and major maintenance $ 1.76 $ 0.73 Depreciation and amortization 2.03 1.85 Other manufacturing (h) 4.36 4.51 Total $ 8.15 $ 7.09 Speedway Operating Statistics Convenience stores at period-end 2,771 2,753 Gasoline and distillate sales (millions of gallons) 1,483 1,432 Gasoline and distillate gross margin (dollars per gallon) (j) $ 0.1682 $ 0.1970 Merchandise sales (in millions) $ 1,152 $ 1,111 Merchandise gross margin (in millions) $ 330 $ 311 Merchandise gross margin percent 29.0 % 28.0 % Same store gasoline sales volume (period over period) 1.0 % (1.2 %) Same store merchandise sales (period over period) (k) 3.1 % 6.2 % Midstream Operating Statistics Crude oil and refined product pipeline throughputs (mbpd) (l) 2,181 2,107 Gathering system throughput (MMcf/d) (m) 3,345 Natural gas processed (MMcf/d) (m) 5,636 C2 (ethane) + NGLs (natural gas liquids) fractionated (mbpd) (m) 312 (a) Total average daily volumes of refined product sales to wholesale, branded and retail (Speedway segment) customers. (b) Includes intersegment sales. (c) Sales revenue less cost of refinery inputs and purchased products, divided by total refinery throughputs. (d) Excludes the lower of cost or market inventory valuation charge of $15 million for the first quarter of 2016. (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 82 mbpd and 35 mbpd for the three months ended March 31, 2016 and 2015 , respectively. (g) Per barrel of total refinery throughputs. (h) Includes utilities, labor, routine maintenance and other operating costs. (i) Includes inter-refinery transfer volumes. (j) The price paid by consumers less the cost of refined products, including transportation, consumer excise taxes and bankcard processing fees, divided by gasoline and distillate sales volume. (k) Excludes cigarettes. Same store sales comparison includes only locations owned at least 13 months. (l) On owned common-carrier pipelines, excluding equity method investments. (m) Includes amounts related to unconsolidated equity method investments. Includes the results of the MarkWest assets beginning on the Dec. 4, 2015 acquisition date.

MPLX LP (Detail)

MPLX LP (Detail) - MPLX LP	Mar. 31, 2016BargeTow_Boat	Mar. 31, 2016
Noncontrolling Interest [Line Items]
Number of tow boats | Tow_Boat	18
Number of barges | Barge	205
Ownership percentage of general partner interest	100.00%	100.00%
Public's ownership interest in MPLX	75.00%	75.00%
General Partner and Limited Partner
Noncontrolling Interest [Line Items]
MPC's partnership interest in MPLX (in percentage)	25.00%	25.00%
General Partner
Noncontrolling Interest [Line Items]
MPC's partnership interest in MPLX (in percentage)	2.00%	2.00%
Storage Services Butane Cavern
Noncontrolling Interest [Line Items]
Ownership interest		100.00%
MPLX Pipe Line Holdings LP | General Partner
Noncontrolling Interest [Line Items]
Ownership interest		100.00%

MPLX LP (Contribution of Inland

MPLX LP (Contribution of Inland Marine Business to MPLX) (Details) - MPLX LP shares in Thousands, $ in Millions	Mar. 31, 2016USD ($)shares
Limited Partner
Noncontrolling Interest [Line Items]
Units issued, number of shares	23,000
Equity interest issued, value assigned | $	$ 600
General Partner
Noncontrolling Interest [Line Items]
Units issued, number of shares	460

MPLX LP (ATM Program) (Details)

MPLX LP (ATM Program) (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 04, 2016
Noncontrolling Interest [Line Items]
Net proceeds from issuance of MPLX LP common limited partners units	$ 315	$ 0
MPLX LP | General Partner
Noncontrolling Interest [Line Items]
MPC's partnership interest in MPLX (in percentage)	2.00%
ATM Program | MPLX LP
Noncontrolling Interest [Line Items]
Common units aggregate value			$ 500
Net proceeds from issuance of MPLX LP common limited partners units	$ 315
General partners' contributed capital	$ 6
ATM Program | MPLX LP | Limited Partners Common Units [Member]
Noncontrolling Interest [Line Items]
Sale of units (in number of common units)	12

Acquisitions and Investments (M

Acquisitions and Investments (Merger with MarkWest Energy Partners, L.P.) (Details) $ in Millions		Dec. 04, 2015USD ($)Segment	Dec. 31, 2015USD ($)	Mar. 31, 2016USD ($)
Business Acquisition [Line Items]
Purchase price adjustments	[1]			$ (241)
Number of reporting units				3
Midstream
Business Acquisition [Line Items]
Purchase price adjustments	[1]			$ (241)
Number of reporting units | Segment		3
MarkWest
Business Acquisition [Line Items]
Total fair value of consideration transferred		$ 8,610
Fair value of MPLX units issued		7,330
Cash payment to MarkWest unitholders		1,230	$ 1,280
Payable to MarkWest Class B unitholders		50
Equity method investments		2,600
Property, plant and equipment, net		8,517
MarkWest | Misstatement of Original Purchase Price Allocation
Business Acquisition [Line Items]
Purchase price adjustments		(68)
Equity method investments		2
Property, plant and equipment, net		2
MarkWest | Misstatement of Original Purchase Price Allocation | Customer Relationships
Business Acquisition [Line Items]
Other noncurrent assets		64
MarkWest | Adjustments
Business Acquisition [Line Items]
Equity method investments		143
Property, plant and equipment, net		$ 43
[1]	See Note 4 for further discussion on purchase price allocation adjustments.

Acquisitions and Investments 57

Acquisitions and Investments (MarkWest - Assets Acquired and Liabilities Assumed) (Details) - USD ($) $ in Millions		Mar. 31, 2016	Dec. 31, 2015	Dec. 04, 2015
Business Acquisition [Line Items]
Goodwill		$ 3,649	$ 4,019
MarkWest
Business Acquisition [Line Items]
Cash and cash equivalents				$ 12
Receivables				164
Inventories				32
Other current assets				44
Equity method investments				2,600
Property, plant and equipment, net				8,517
Other noncurrent assets(a)				538
Total assets acquired				11,907
Accounts payable				328
Payroll and benefits payable				13
Accrued taxes				21
Other current liabilities				44
Long-term debt				4,567
Deferred income taxes				377
Deferred credit and other liabilities				151
Noncontrolling interests				13
Total liabilities and noncontrolling interest assumed				5,514
Net assets acquired excluding goodwill				6,393
Goodwill				2,213
Net assets acquired				8,606
MarkWest | As originally reported
Business Acquisition [Line Items]
Cash and cash equivalents				12
Receivables				164
Inventories				33
Other current assets				44
Equity method investments				2,457
Property, plant and equipment, net				8,474
Other noncurrent assets(a)				473
Total assets acquired				11,657
Accounts payable				322
Payroll and benefits payable				13
Accrued taxes				21
Other current liabilities				44
Long-term debt				4,567
Deferred income taxes				374
Deferred credit and other liabilities				151
Noncontrolling interests				13
Total liabilities and noncontrolling interest assumed				5,505
Net assets acquired excluding goodwill				6,152
Goodwill				2,454
Net assets acquired				8,606
MarkWest | Adjustments
Business Acquisition [Line Items]
Cash and cash equivalents				0
Receivables				0
Inventories				(1)
Other current assets				0
Equity method investments				143
Property, plant and equipment, net				43
Other noncurrent assets(a)	[1]			65
Total assets acquired				250
Accounts payable				6
Payroll and benefits payable				0
Accrued taxes				0
Other current liabilities				0
Long-term debt				0
Deferred income taxes				3
Deferred credit and other liabilities				0
Noncontrolling interests				0
Total liabilities and noncontrolling interest assumed				9
Net assets acquired excluding goodwill				241
Goodwill				(241)
Net assets acquired				$ 0
[1]	The adjustment relates to the intangible asset acquired.

Acquisitions and Investments (U

Acquisitions and Investments (Unaudited Pro Forma Financial Information) (Details) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2015USD ($)$ / shares
Business Combinations [Abstract]
Sales and other operating revenues (including consumer excise taxes) | $	$ 17,652
Net income attributable to MPC | $	$ 871
Net income attributable to MPC per share – basic | $ / shares	$ 1.60
Net income attributable to MPC per share – diluted | $ / shares	$ 1.59

Acquisitions and Investments (I

Acquisitions and Investments (Investment in Ocean Vessel Joint Venture) (Details) - Crowley Ocean Partners $ in Millions	12 Months Ended	13 Months Ended
	Dec. 31, 2015USD ($)vessel	Sep. 30, 2016vessel	Mar. 31, 2016	Sep. 30, 2015
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage			50.00%	50.00%
Number of vessels	2
Cash paid to acquire equity method investments | $	$ 72
Scenario, Forecast
Schedule of Equity Method Investments [Line Items]
Number of vessels		4

Acquisitions and Investments 60

Acquisitions and Investments (Investments in Pipeline Company) (Details) - USD ($) $ in Millions	3 Months Ended	29 Months Ended
	Mar. 31, 2016	Mar. 31, 2016	Jan. 01, 2019
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	$ 5	$ 292
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%

Variable Interest Entities (Det

Variable Interest Entities (Details) $ in Millions	Mar. 31, 2016USD ($)
MarkWest Utica EMG
Variable Interest Entity [Line Items]
Equity method investments, ownership percentage	60.00%
VIE, maximum loss exposure, amount	$ 2,290
Ohio Gathering
Variable Interest Entity [Line Items]
Equity method investments, ownership percentage	36.00%

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Sep. 30, 2015
Related Party Transaction [Line Items]
Other income from related parties	$ 8	$ 1
Centennial
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	50.00%
Crowley Ocean Partners
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	50.00%			50.00%
Explorer
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	25.00%
Illinois Extension Pipeline
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	35.00%
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%
Jefferson Dry Gas
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	67.00%
MarkWest Utica EMG
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	60.00%
Ohio Condensate
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	60.00%
Due from related parties, noncurrent	$ 0		$ 1
Ohio Gathering
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	36.00%
TAAE
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	45.00%
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%
Other equity method investees
Related Party Transaction [Line Items]
Sales to related parties	$ 1	$ 1

Related Party Transactions - Pu

Related Party Transactions - Purchases from Related Parties (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Related Party Transaction [Line Items]
Purchases from related parties	$ 107	$ 76
Centennial
Related Party Transaction [Line Items]
Purchases from related parties	2	0
Crowley Ocean Partners
Related Party Transaction [Line Items]
Purchases from related parties	6	0
Explorer
Related Party Transaction [Line Items]
Purchases from related parties	2	7
Illinois Extension Pipeline
Related Party Transaction [Line Items]
Purchases from related parties	27	0
LOCAP
Related Party Transaction [Line Items]
Purchases from related parties	6	5
LOOP
Related Party Transaction [Line Items]
Purchases from related parties	13	13
Ohio Condensate
Related Party Transaction [Line Items]
Purchases from related parties	3	0
TAAE
Related Party Transaction [Line Items]
Purchases from related parties	9	13
TACE
Related Party Transaction [Line Items]
Purchases from related parties	17	16
TAME
Related Party Transaction [Line Items]
Purchases from related parties	20	20
Other equity method investees
Related Party Transaction [Line Items]
Purchases from related parties	$ 2	$ 2

Related Party Transactions - Re

Related Party Transactions - Receivables From Related Parties (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Current receivables from related parties	$ 7	$ 13
Centennial
Related Party Transaction [Line Items]
Current receivables from related parties	1	1
Jefferson Dry Gas
Related Party Transaction [Line Items]
Current receivables from related parties	0	2
MarkWest Utica EMG
Related Party Transaction [Line Items]
Current receivables from related parties	1	1
Ohio Condensate
Related Party Transaction [Line Items]
Current receivables from related parties	0	3
Ohio Gathering
Related Party Transaction [Line Items]
Current receivables from related parties	3	5
Other equity method investees
Related Party Transaction [Line Items]
Current receivables from related parties	$ 2	$ 1

Related Party Transactions - Pa

Related Party Transactions - Payables To Related Parties (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Payables to related parties	$ 47	$ 42
Centennial
Related Party Transaction [Line Items]
Payables to related parties	1	0
Explorer
Related Party Transaction [Line Items]
Payables to related parties	1	1
Illinois Extension Pipeline
Related Party Transaction [Line Items]
Payables to related parties	10	4
LOCAP
Related Party Transaction [Line Items]
Payables to related parties	2	2
LOOP
Related Party Transaction [Line Items]
Payables to related parties	4	5
MarkWest Utica EMG
Related Party Transaction [Line Items]
Payables to related parties	21	19
Ohio Condensate
Related Party Transaction [Line Items]
Payables to related parties	3	4
TAAE
Related Party Transaction [Line Items]
Payables to related parties	1	1
TACE
Related Party Transaction [Line Items]
Payables to related parties	1	2
TAME
Related Party Transaction [Line Items]
Payables to related parties	2	3
Other equity method investees
Related Party Transaction [Line Items]
Payables to related parties	$ 1	$ 1

Income Per Common Share - Summa

Income Per Common Share - Summary of Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Basic earnings per share:
Net income attributable to MPC	$ 1	$ 891
Income allocated to participating securities	0	1
Income available to common stockholders – basic	$ 1	$ 890
Weighted average common shares outstanding (in shares)	529	545
Basic (in USD per share)	$ 0.003	$ 1.63
Diluted earnings per share:
Net income attributable to MPC	$ 1	$ 891
Income allocated to participating securities	0	1
Income available to common stockholders – diluted	$ 1	$ 890
Weighted average common shares outstanding (in shares)	529	545
Effect of dilutive securities (in shares)	2	4
Weighted average common shares, including dilutive effect (in shares)	531	549
Diluted (in USD per share)	$ 0.003	$ 1.62

Income Per Common Share - Anti-

Income Per Common Share - Anti-dilutive Shares (Details) - shares shares in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Stock Based Compensation Expense [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares issued under stock-based compensation plans	3	1

Equity - Additional Information

Equity - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		51 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016
Equity [Abstract]
Stock repurchase plan authorized amount	$ 10,000		$ 10,000
Cash paid for shares repurchased	75	$ 209	7,310
Stock repurchase plan remaining authorized amount	$ 2,690		$ 2,690
Number of shares repurchased	2	4	200
Effective average cost per delivered share	$ 43.96	$ 47.51	$ 36.71

Equity - Share Repurchases (Det

Equity - Share Repurchases (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		51 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016
Equity [Abstract]
Number of shares repurchased	2	4	200
Cash paid for shares repurchased	$ 75	$ 209	$ 7,310
Effective average cost per delivered share	$ 43.96	$ 47.51	$ 36.71

Segment Information - Additiona

Segment Information - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2016Segment
Segment Reporting [Abstract]
Number of reportable segments	3

Segment Information - Income Fr

Segment Information - Income From Operations Attributable To Operating Segments (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Segment Reporting Information [Line Items]
Revenues		$ 12,755	$ 17,191
Income from operations		75	1,470
Income from equity method investments		22	15
Depreciation and amortization		490	363
Capital expenditures and investments	[1],[2]	684	384
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues	[3]	2,359	2,921
Operating Segments
Segment Reporting Information [Line Items]
Revenues		15,114	20,112
Income from operations	[4]	272	1,550
Income from equity method investments		22	15
Depreciation and amortization	[5]	476	350
Capital expenditures and investments	[6]	643	355
Refining & Marketing
Segment Reporting Information [Line Items]
Revenues		8,406	12,644
Refining & Marketing | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues		2,165	2,734
Refining & Marketing | Operating Segments
Segment Reporting Information [Line Items]
Revenues		10,571	15,378
Income from operations	[7]	(62)	1,292
Income from equity method investments		(1)	6
Depreciation and amortization		273	261
Capital expenditures and investments	[7]	243	223
Speedway
Segment Reporting Information [Line Items]
Revenues		3,950	4,531
Speedway | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues		1	0
Speedway | Operating Segments
Segment Reporting Information [Line Items]
Revenues		3,951	4,531
Income from operations		167	168
Income from equity method investments		0	0
Depreciation and amortization		63	63
Capital expenditures and investments		50	45
Midstream
Segment Reporting Information [Line Items]
Revenues		399	16
Midstream | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues		193	187
Midstream | Operating Segments
Segment Reporting Information [Line Items]
Revenues		592	203
Income from operations	[4],[7]	167	90
Income from equity method investments		23	9
Depreciation and amortization		140	26
Capital expenditures and investments	[7]	350	87
Reportable Segment
Segment Reporting Information [Line Items]
Revenues		$ 12,755	$ 17,191
[1]	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
[2]	Includes capitalized interest of $17 million and $8 million for the three months ended March 31, 2016 and 2015, respectively.
[3]	Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties
[4]	Corporate overhead expenses attributable to MPLX are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway 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 (including any goodwill) and investments in affiliates.
[7]	We revised our operating segment presentation in the first quarter of 2016 in connection with the contribution of our inland marine business to MPLX; our inland marine business, which was previously included in Refining & Marketing, is now included in Midstream. Comparable prior period information has been recast to reflect our revised segment presentation.

Segment Information - Reconcili

Segment Information - Reconciliation Of Segment Income From Operations To Income Before Income Taxes (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016		Mar. 31, 2015
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations		$ 75		$ 1,470
Impairment expense		129		0
Net interest and other financial income (costs)		142		81
Income before income taxes		(67)		1,389
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations	[1]	272		1,550
Corporate and Other
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations	[2],[3],[4]	(67)		(79)
Segment Reconciling Items
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pension settlement expenses	[5]	(1)		(1)
Impairment expense		$ (129)	[6]	$ 0
[1]	Corporate overhead expenses attributable to MPLX are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments.
[2]	Corporate and other unallocated items consists primarily of MPC’s corporate administrative expenses and costs related to certain non-operating assets.
[3]	Corporate overhead expenses attributable to MPLX are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments.
[4]	We revised our operating segment presentation in the first quarter of 2016 in connection with the contribution of our inland marine business to MPLX; our inland marine business, which was previously included in Refining & Marketing, is now included in Midstream. Comparable prior period information has been recast to reflect our revised segment presentation.
[5]	See Note 20.
[6]	See Note 14.

Segment Information - Reconci73

Segment Information - Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016		Mar. 31, 2015
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures [Line Items]
Capital expenditures and investments	[1],[2]	$ 684		$ 384
Plus: Items not allocated to segments:
Capital expenditures	[3]	475		342
MarkWest | Adjustments
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures [Line Items]
Less: Investments in equity method investees		(143)
Operating Segments
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures [Line Items]
Capital expenditures and investments	[4]	643		355
Less: Investments in equity method investees		(209)	[5]	(42)
Corporate and Other
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures [Line Items]
Capital expenditures and investments	[2]	41		29
Plus: Items not allocated to segments:
Capital expenditures not allocated to segments		24		21
Capitalized interest		$ 17		$ 8
[1]	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
[2]	Includes capitalized interest of $17 million and $8 million for the three months ended March 31, 2016 and 2015, respectively.
[3]	Capital expenditures include changes in capital accruals. See Note 18 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 (including any goodwill) and investments in affiliates.
[5]	The three months ended March 31, 2016 includes an adjustment of $143 million to the fair value of equity investments acquired in connection with the MarkWest Merger. See Note 4.

Other Items - Net Interest And

Other Items - Net Interest And Other Financial Income (Costs) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016		Mar. 31, 2015
Interest income	$ 1		$ 1
Interest expense	(153)	[1]	(80)
Interest capitalized	16		8
Other financial costs	(6)		(10)
Net interest and other financial income (costs)	142		$ 81
MPLX LP | Senior Notes | MarkWest
Amortization of debt discount	$ 11
[1]	The three months ended March 31, 2016 includes $11 million for the amortization of the discount related to the difference between the fair value and the principal amount of the assumed MarkWest debt.

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating Loss Carryforwards [Line Items]
Combined federal, state and foreign income tax rate	(17.00%)	35.00%
Effective income tax rate reconciliation, noncontrolling interest income (loss), percent	(51.00%)
Statutory rate applied to income before income taxes	35.00%	35.00%
Deferred income tax effect from changes in noncontrolling interest - contribution of inland marine	$ 42
Deferred income tax effect from changes in noncontrolling interest - MarkWest Merger	115
Unrecognized benefits	11
Additional Paid-in Capital
Operating Loss Carryforwards [Line Items]
Deferred income tax effect from changes in noncontrolling interest - contribution of inland marine	42
Deferred income tax effect from changes in noncontrolling interest - MarkWest Merger	$ 115

Inventories - Summary Of Invent

Inventories - Summary Of Inventories (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Inventory Disclosure [Abstract]
Crude oil and refinery feedstocks	$ 2,044	$ 2,180
Refined products	2,761	2,804
Materials and supplies	399	438
Merchandise	164	173
Lower of cost or market reserve	(385)	(370)
Total	$ 4,983	$ 5,225

Inventories - Additional Inform

Inventories - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Inventory Disclosure [Abstract]
Lower of cost or market reserve	$ (385)		$ (370)
Inventory market valuation charge	15	$ 0
Impact on revenues and costs as a result of LIFO liquidations	$ 0	$ 0

Property, Plant And Equipment -

Property, Plant And Equipment - Summary Of Property, Plant And Equipment (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 36,215	$ 35,604
Less accumulated depreciation	10,896	10,440
Net property, plant and equipment	25,319	25,164
Operating Segments | Refining & Marketing
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	18,631	18,396
Operating Segments | Speedway
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	5,108	5,067
Operating Segments | Midstream
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	11,707	11,379
Corporate and Other
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 769	$ 762

Goodwill (Details)

Goodwill (Details) $ in Millions	Dec. 04, 2015Segment	Mar. 31, 2016USD ($)	Mar. 31, 2015USD ($)
Goodwill [Line Items]
Number of reporting units		3
Number of reporting units impaired		2
Impairment loss		$ (129)	$ 0
Fair Value, Measurements, Nonrecurring
Goodwill [Line Items]
Impairment loss		(129)	$ 0
Midstream
Goodwill [Line Items]
Number of reporting units | Segment	3
Impairment loss		$ (129)
Midstream | Fair Value, Measurements, Nonrecurring | Goodwill | Minimum
Goodwill [Line Items]
Discount rate		10.50%
Midstream | Fair Value, Measurements, Nonrecurring | Goodwill | Maximum
Goodwill [Line Items]
Discount rate		11.50%

Goodwill - Changes in Carrying

Goodwill - Changes in Carrying Amount of Goodwill (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Goodwill [Line Items]
Goodwill, beginning balance		$ 4,019
Purchase price adjustments	[1]	(241)
Impairment loss		(129)	$ 0
Goodwill, ending balance		3,649
Refining & Marketing
Goodwill [Line Items]
Goodwill, beginning balance		539
Purchase price adjustments		0
Impairment loss		0
Goodwill, ending balance		539
Speedway
Goodwill [Line Items]
Goodwill, beginning balance		853
Purchase price adjustments		0
Impairment loss		0
Goodwill, ending balance		853
Midstream
Goodwill [Line Items]
Goodwill, beginning balance		2,627
Purchase price adjustments	[1]	(241)
Impairment loss		(129)
Goodwill, ending balance		$ 2,257
[1]	See Note 4 for further discussion on purchase price allocation adjustments.

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Accounted for at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions		Mar. 31, 2016		Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash collateral netted with derivative liabilities		$ 40
Cash collateral netted with derivative assets				$ (23)
Contingent consideration, current		200		196
Embedded derivatives in commodity contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Embedded derivatives, current		6		5
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - netting and collateral	[1]	(67)		(62)
Commodity derivative instruments, assets - collateral pledged not offset		72		0
Other assets	[2]	2		2
Total assets at fair value	[2]	4		53
Commodity derivative instruments, liabilities - netting and collateral		(107)	[1]	(39)
Commodity derivative instruments, liabilities - collateral pledged not offset		0		0	[3]
Contingent consideration, liability	[2],[3]	324		317
Total liabilities at fair value	[2]	359		349
Fair Value, Measurements, Recurring | Commodity derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - netting and collateral	[1]	(67)		(62)
Commodity derivative instruments, assets - net carrying value on balance sheet	[2]	2		51
Commodity derivative instruments, assets - collateral pledged not offset		72		0
Commodity derivative instruments, liabilities - netting and collateral	[1]	(107)		(39)
Commodity derivative instruments, liabilities - net carrying value on balance sheet	[2]	1		0
Commodity derivative instruments, liabilities - collateral pledged not offset		0		0
Fair Value, Measurements, Recurring | Embedded derivatives in commodity contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, liabilities - netting and collateral		0		0
Commodity derivative instruments, liabilities - net carrying value on balance sheet	[2],[4]	34		32
Commodity derivative instruments, liabilities - collateral pledged not offset		0		0
Fair Value, Measurements, Recurring | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets		2		2
Total assets at fair value		69		106
Contingent consideration, liability		0		0
Total liabilities at fair value		107		39
Fair Value, Measurements, Recurring | Level 1 | Commodity derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - gross		67		104
Commodity derivative instruments, liabilities - gross		107		39
Fair Value, Measurements, Recurring | Level 1 | Embedded derivatives in commodity contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, liabilities - gross		0		0
Fair Value, Measurements, Recurring | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets		0		0
Total assets at fair value		1		2
Contingent consideration, liability		0		0
Total liabilities at fair value		0		0
Fair Value, Measurements, Recurring | Level 2 | Commodity derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - gross		1		2
Commodity derivative instruments, liabilities - gross		0		0
Fair Value, Measurements, Recurring | Level 2 | Embedded derivatives in commodity contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, liabilities - gross		0		0
Fair Value, Measurements, Recurring | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets		0		0
Total assets at fair value		1		7
Contingent consideration, liability	[3]	324		317
Total liabilities at fair value		359		349
Fair Value, Measurements, Recurring | Level 3 | Commodity derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - gross		1		7
Commodity derivative instruments, liabilities - gross		1		0
Fair Value, Measurements, Recurring | Level 3 | Embedded derivatives in commodity contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, liabilities - gross	[4]	$ 34		$ 32
[1]	Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of March 31, 2016, cash collateral of $40 million was netted with the mark-to-market derivative liabilities. As of December 31, 2015, $23 million was netted with mark-to-market derivative assets.
[2]	We have no derivative contracts that are subject to master netting arrangements that are reflected gross on the balance sheet.
[3]	Includes $200 million and $196 million classified as current at March 31, 2016 and December 31, 2015, respectively.
[4]	Includes $6 million and $5 million classified as current at March 31, 2016 and December 31, 2015, respectively.

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Detail)	3 Months Ended			24 Months Ended
	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)$ / bbl	Mar. 31, 2015USD ($)	Jun. 30, 2016USD ($)	Feb. 01, 2013USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Remaining commitment for contingent consideration		$ 1,700,000,000
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
Total cumulative payment capped over six-year period					$ 700,000,000
Remaining commitment for contingent consideration		$ 331,000,000
Galveston Bay Refinery and Related Assets | Scenario, Forecast
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration payment	$ 200,000,000			$ 569,000,000
Remaining commitment for contingent consideration	$ 131,000,000
Embedded derivatives in commodity contracts | First Five Year Term
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Embedded Derivative Renewal Term		5 years
Embedded derivatives in commodity contracts | Second Five Year Term
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Embedded Derivative Renewal Term		5 years
Level 3 | Minimum | Galveston Bay Refinery and Related Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range of internal and external crack spread forecast per barrel | $ / bbl		9
Discount rate		4.00%
Level 3 | Maximum | Galveston Bay Refinery and Related Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range of internal and external crack spread forecast per barrel | $ / bbl		16
Discount rate		9.00%
Level 3 | Commodity derivatives | Minimum | Ethanol prices
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward commodity price		$ 0.17
Level 3 | Commodity derivatives | Maximum | Ethanol prices
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward commodity price		$ 3.37
Level 3 | Embedded derivatives in commodity contracts | First Five Year Term
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Probability of renewal		50.00%
Level 3 | Embedded derivatives in commodity contracts | Second Five Year Term
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Probability of renewal		75.00%
Level 3 | Embedded derivatives in commodity contracts | Minimum | ERCOT Pricing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity price		$ 21.34
Level 3 | Embedded derivatives in commodity contracts | Maximum | ERCOT Pricing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity price		44.27
Fair Value, Measurements, Recurring | Derivative
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gains losses included in net income		5,000,000	$ 0
Fair Value, Measurements, Recurring | Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gains losses included in net income		$ 7,000,000	$ 12,000,000

Fair Value Measurements - Recon

Fair Value Measurements - Reconciliation of Net Beginning and Ending Balances Recorded for Net Assets and Liabilities Classified as Level 3 (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 342	$ 478
Unrealized and realized losses included in net income	12	12
Settlements of derivative instruments	4	0
Ending balance	$ 358	$ 490

Fair Value Measurements - Nonre

Fair Value Measurements - Nonrecurring (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment expense	$ 129	$ 0
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill, fair value disclosure	0	0
Impairment expense	$ 129	$ 0

Fair Value Measurements - Finan

Fair Value Measurements - Financial Instruments at Fair Value, Excluding Derivative Financial Instruments and Contingent Consideration (Detail) - USD ($) $ in Millions		Mar. 31, 2016	Dec. 31, 2015
Fair Value
Financial assets:
Investments		$ 30	$ 33
Other		35	35
Total financial assets		65	68
Financial liabilities:
Long-term debt	[1]	11,086	11,366
Deferred credits and other liabilities		140	136
Total financial liabilities		11,226	11,502
Carrying Value
Financial assets:
Investments		2	2
Other		35	33
Total financial assets		37	35
Financial liabilities:
Long-term debt	[1]	11,276	11,628
Deferred credits and other liabilities		138	135
Total financial liabilities		$ 11,414	$ 11,763
[1]	Excludes capital leases and debt issuance costs, however, includes amount classified as debt due within one year.

Derivatives - Classification of

Derivatives - Classification of Gross Fair Values of Derivative Instruments, Excluding Cash Collateral (Detail) - Commodity derivatives - USD ($) $ in Millions		Mar. 31, 2016	Dec. 31, 2015
Other current assets
Derivatives, Fair Value [Line Items]
Asset		$ 69	$ 113
Liability		107	39
Other current liabilities
Derivatives, Fair Value [Line Items]
Asset		0	0
Liability		7	5
Deferred credits and other liabilities
Derivatives, Fair Value [Line Items]
Asset		0	0
Liability	[1]	$ 28	$ 27
[1]	Includes embedded derivatives.

Derivatives - Open Commodity De

Derivatives - Open Commodity Derivative Contracts - Crude Oil (Details) bbl in Thousands	3 Months Ended
	Mar. 31, 2016bbl
Crude Oil Exchange-Traded
Derivative [Line Items]
Percentage of derivative contracts expiring in the period	83.00%
Derivative contract expiration date	Jun. 30, 2016
Crude Oil Exchange-Traded | Long
Derivative [Line Items]
Notional contracts (in thousands of Total Barrels)	25,142	[1]
Crude Oil Exchange-Traded | Short
Derivative [Line Items]
Notional contracts (in thousands of Total Barrels)	30,048	[1]
Crude Oil OTC | Short
Derivative [Line Items]
Notional contracts (in thousands of Total Barrels)	83
[1]	of the exchange-traded contracts expire in the second quarter of 2016.

Derivatives - Open Commodity 88

Derivatives - Open Commodity Derivative Contracts - Natural Gas (Details)	Mar. 31, 2016MMBTU
Natural Gas OTC | Long
Derivative [Line Items]
Notional contracts (in MMbtu)	745,826

Derivatives - Open Commodity 89

Derivatives - Open Commodity Derivative Contracts - Refined Products (Detail) gal in Thousands	3 Months Ended
	Mar. 31, 2016gal
Refined Products Exchange-Traded
Derivative [Line Items]
Percentage of derivative contracts expiring in the period	100.00%
Refined Products Exchange-Traded | Long
Derivative [Line Items]
Notional contracts (in thousands of Total Gallons)	241,500	[1]
Refined Products Exchange-Traded | Short
Derivative [Line Items]
Notional contracts (in thousands of Total Gallons)	137,424	[1]
Refined Products OTC | Short
Derivative [Line Items]
Notional contracts (in thousands of Total Gallons)	55,759
[1]	of the exchange-traded contracts expire in the second quarter of 2016.

Derivatives - Effect of Commodi

Derivatives - Effect of Commodity Derivative Instruments in Statements of Income (Detail) - Commodity derivatives - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	$ (55)	$ 59
Sales and other operating revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	6	14
Cost of revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	$ (61)	$ 45

Debt - Outstanding Borrowings (

Debt - Outstanding Borrowings (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Commercial paper		$ 188	$ 0
Total		12,104	12,475
Unamortized debt issuance costs		(50)	(51)
Unamortized discount	[1]	(488)	(499)
Amounts due within one year		(215)	(29)
Total long-term debt due after one year		11,351	11,896
MPLX LP
Debt Instrument [Line Items]
Amounts due within one year		(1)	(1)
Total long-term debt due after one year		4,715	5,255
Senior Notes | MPLX LP | MarkWest
Debt Instrument [Line Items]
Long-term debt, gross		63	63
Unamortized discount		(453)	(464)
Capital Lease Obligations | Subsidiaries
Debt Instrument [Line Items]
Capital lease obligations		$ 340	348
Debt instrument maturity year, start		Jan. 1, 2016
Debt instrument maturity year, end		Dec. 31, 2028
Bank revolving credit facility due 2017 | Line of Credit
Debt Instrument [Line Items]
Long-term debt, gross		$ 0	0
Line of credit facility, expiration date		Sep. 14, 2017
Term loan agreement due 2019 | Unsecured Debt
Debt Instrument [Line Items]
Long-term debt, gross		$ 700	700
Line of credit facility, expiration date		Sep. 30, 2019
Senior notes, 2.700% due December 2018 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 600	600
Debt instrument, maturity date		Dec. 14, 2018
Debt instrument, interest rate		2.70%
Senior notes, 3.400% due December 2020 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 650	650
Debt instrument, maturity date		Dec. 15, 2020
Debt instrument, interest rate		3.40%
Senior notes, 5.125% due March 2021 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,000	1,000
Debt instrument, maturity date		Mar. 1, 2021
Debt instrument, interest rate		5.125%
Senior notes, 3.625%, due September 2024 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 750	750
Debt instrument, maturity date		Sep. 15, 2024
Debt instrument, interest rate		3.625%
Senior notes, 6.500%, due March 2041 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,250	1,250
Debt instrument, maturity date		Mar. 1, 2041
Debt instrument, interest rate		6.50%
Senior notes, 4.750%, due September 2044 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 800	800
Debt instrument, maturity date		Sep. 15, 2044
Debt instrument, interest rate		4.75%
Senior notes, 5.850% due December 2045 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 250	250
Debt instrument, maturity date		Dec. 15, 2045
Debt instrument, interest rate		5.85%
Senior notes, 5.000%, due September 2054 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 400	400
Debt instrument, maturity date		Sep. 15, 2054
Debt instrument, interest rate		5.00%
MPLX bank revolving credit facility due 2020 | Unsecured Debt | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross		$ 250	250
Line of credit facility, expiration date		Nov. 20, 2019
MPLX bank revolving credit facility due 2020 | Line of Credit | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross		$ 326	877
Line of credit facility, expiration date		Dec. 4, 2020
MPLX senior notes, 5.500%, due February 2023 | Senior Notes | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross		$ 710	710
Debt instrument, maturity date		Feb. 15, 2023
Debt instrument, interest rate		5.50%
MPLX senior notes, 5.500%, due February 2023 | Senior Notes | MPLX LP | MarkWest
Debt Instrument [Line Items]
Debt instrument, maturity date		Feb. 15, 2023
Debt instrument, interest rate		5.50%
MPLX senior notes, 4.500%, due July 2023 | Senior Notes | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross		$ 989	989
Debt instrument, maturity date		Jul. 15, 2023
Debt instrument, interest rate		4.50%
MPLX senior notes, 4.500%, due July 2023 | Senior Notes | MPLX LP | MarkWest
Debt Instrument [Line Items]
Debt instrument, maturity date		Jul. 15, 2023
Debt instrument, interest rate		4.50%
MPLX senior notes, 4.875%, due December 2024 | Senior Notes | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,149	1,149
Debt instrument, maturity date		Dec. 1, 2024
Debt instrument, interest rate		4.875%
MPLX senior notes, 4.875%, due December 2024 | Senior Notes | MPLX LP | MarkWest
Debt Instrument [Line Items]
Debt instrument, maturity date		Dec. 1, 2024
Debt instrument, interest rate		4.875%
MPLX senior notes, 4.000%, due February 2025 | Senior Notes | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross		$ 500	500
Debt instrument, maturity date		Feb. 15, 2025
Debt instrument, interest rate		4.00%
MPLX senior notes, 4.875%, due June 2025 | Senior Notes | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,189	1,189
Debt instrument, maturity date		Jun. 1, 2025
Debt instrument, interest rate		4.875%
MPLX senior notes, 4.875%, due June 2025 | Senior Notes | MPLX LP | MarkWest
Debt Instrument [Line Items]
Debt instrument, maturity date		Jun. 1, 2025
Debt instrument, interest rate		4.875%
Trade receivables securitization facility due December 2016
Debt Instrument [Line Items]
Long-term debt, gross		$ 0
Trade receivables securitization facility due December 2016 | Secured Debt | Subsidiaries
Debt Instrument [Line Items]
Long-term debt, gross		$ 0	$ 0
Line of credit facility, expiration date		Dec. 31, 2016
[1]	Includes $453 million and $464 million discount as of March 31, 2016 and December 31, 2015, respectively, related to the difference between the fair value and the principal amount of the assumed MarkWest debt.

Debt - Commercial Paper (Detail

Debt - Commercial Paper (Details) - USD ($) $ in Millions	Feb. 26, 2016	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Debt Instrument [Line Items]
Debt instrument, term	397 days
Commercial paper – issued		$ 264	$ 0
Commercial paper - repayments		76	$ 0
Commercial paper		$ 188		$ 0
Commercial Paper
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 2,000
Weighted average interest rate		0.89%

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Bank revolving credit facility due 2017 | Line of Credit
Line of Credit Facility [Line Items]
Long-term debt, gross	$ 0	$ 0
Trade receivables securitization facility due December 2016
Line of Credit Facility [Line Items]
Long-term debt, gross	0
Borrowings during period	$ 280
Interest rate during period	1.30%
Repayments during period	$ 280
MPLX bank revolving credit facility due 2020 | MPLX LP
Line of Credit Facility [Line Items]
Borrowings during period	$ 306
Interest rate during period	1.90%
Repayments during period	$ 857
Remaining borrowing capacity	1,700
MPLX bank revolving credit facility due 2020 | MPLX LP | Letter of Credit
Line of Credit Facility [Line Items]
Borrowings outstanding	8
MPLX bank revolving credit facility due 2020 | Line of Credit | MPLX LP
Line of Credit Facility [Line Items]
Long-term debt, gross	$ 326	$ 877

Supplemental Cash Flow Inform94

Supplemental Cash Flow Information - Summary of Supplemental Cash Flow Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Net cash provided by operating activities included:
Interest paid (net of amounts capitalized)	$ 160	$ 128
Net income taxes paid to (refunded from) taxing authorities	$ (128)	$ 160

Supplemental Cash Flow Inform95

Supplemental Cash Flow Information - Reconciliation of Additions to Property, Plant and Equipment to Total Capital Expenditures (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016		Mar. 31, 2015
Supplemental Cash Flow Elements [Abstract]
Additions to property, plant and equipment per consolidated statements of cash flows		$ 745		$ 389
Decrease in capital accruals		(137)		(47)
Total capital expenditures before acquisitions		608		342
Acquisitions		(133)	[1]	0
Capital expenditures	[2]	$ 475		$ 342
[1]	The three months ended March 31, 2016 includes adjustments to the fair values of the property, plant and equipment, intangibles and goodwill acquired in connection with the MarkWest Merger. See Note 4.
[2]	Capital expenditures include changes in capital accruals. See Note 18 for a reconciliation of total capital expenditures to additions to property, plant and equipment as reported in the consolidated statements of cash flows.

Accumulated Other Comprehensi96

Accumulated Other Comprehensive Loss - Changes in Accumulated Other Comprehensive Loss by Component (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		$ (318)	$ (313)
Other comprehensive loss before reclassifications		0	(2)
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit	[1]	(12)	(13)
Amortization - actuarial loss	[1]	11	16
Amortization - settlement loss	[1]	1	1
Tax effect		0	(2)
Other comprehensive income (loss)		0	0
Ending balance		(318)	(313)
Accumulated Defined Benefit Plans Adjustment | Pension Benefits
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(255)	(217)
Other comprehensive loss before reclassifications		0	(1)
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit	[1]	(11)	(12)
Amortization - actuarial loss	[1]	10	13
Amortization - settlement loss	[1]	1	1
Tax effect		0	(1)
Other comprehensive income (loss)		0	0
Ending balance		(255)	(217)
Accumulated Defined Benefit Plans Adjustment | Other Benefits
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(70)	(104)
Other comprehensive loss before reclassifications		0	(1)
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit	[1]	(1)	(1)
Amortization - actuarial loss	[1]	1	3
Amortization - settlement loss		0	0
Tax effect		0	(1)
Other comprehensive income (loss)		0	0
Ending balance		(70)	(104)
Gain on Cash Flow Hedge
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		4	4
Other comprehensive 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) [Line Items]
Beginning balance		3	4
Other comprehensive loss before reclassifications		0	0
Amounts reclassified from accumulated other comprehensive loss:
Tax effect		0	0
Other comprehensive income (loss)		0	0
Ending balance		$ 3	$ 4
[1]	These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 20.

Defined Benefit Pension and O97

Defined Benefit Pension and Other Postretirement Plans - Components of Net Periodic Benefit Costs (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Pension Benefits
Components of net periodic benefit cost:
Service cost	$ 28	$ 23
Interest cost	19	18
Expected return on plan assets	(25)	(26)
Amortization – prior service credit	(11)	(12)
Amortization – actuarial loss	10	13
Amortization - settlement loss	1	1
Net periodic benefit cost	22	17
Other Benefits
Components of net periodic benefit cost:
Service cost	8	8
Interest cost	9	8
Expected return on plan assets	0	0
Amortization – prior service credit	(1)	(1)
Amortization – actuarial loss	1	3
Amortization - settlement loss	0	0
Net periodic benefit cost	$ 17	$ 18

Defined Benefit Pension and O98

Defined Benefit Pension and Other Postretirement Plans - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 0
Pension settlement expenses	1	$ 1
Other Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Benefits paid	2
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Benefits paid	7
Pension settlement expenses	$ 0	$ 0

Stock-Based Compensation Plan99

Stock-Based Compensation Plans - Summary of Stock Option Award Activity (Detail) - Stock Options	3 Months Ended
	Mar. 31, 2016$ / sharesshares
Number of Shares
Outstanding, beginning balance | shares	8,724,631
Granted | shares	934,611
Exercised | shares	(44,137)
Forfeited, canceled or expired | shares	(6,134)
Outstanding, ending balance | shares	9,608,971
Weighted Average Exercise Price
Outstanding, beginning balance (in USD per share) | $ / shares	$ 27.16
Granted (in USD per share) | $ / shares	34.63
Exercised (in USD per share) | $ / shares	16.30
Forfeited, canceled or expired (in USD per share) | $ / shares	48.52
Outstanding, ending balance (in USD per share) | $ / shares	$ 27.92

Stock-Based Compensation Pla100

Stock-Based Compensation Plans - Narrative (Detail)	3 Months Ended
	Mar. 31, 2016$ / shares
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date fair value (in USD per share)	$ 9.97
Performance Unit Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in USD per share)	$ 0.57

Stock-Based Compensation Pla101

Stock-Based Compensation Plans - Summary of Restricted Stock Award Activity (Detail)	3 Months Ended
	Mar. 31, 2016$ / sharesshares
Restricted Stock
Number of Shares
Outstanding, beginning balance | shares	1,074,543
Granted | shares	142,698
RS’s Vested/RSU’s Issued | shares	(106,788)
Forfeited | shares	(16,362)
Outstanding, ending balance | shares	1,094,091
Weighted Average Grant Date Fair Value
Outstanding, beginning balance (in USD per share) | $ / shares	$ 47.70
Granted (in USD per share) | $ / shares	34.93
RS's Vested/RSU's Issued (in USD per share) | $ / shares	44.63
Forfeited (in USD per share) | $ / shares	47.92
Outstanding, ending balance (in USD per share) | $ / shares	$ 46.33
Restricted Stock Units
Number of Shares
Outstanding, beginning balance | shares	513,220
Granted | shares	10,804
RS’s Vested/RSU’s Issued | shares	0
Forfeited | shares	0
Outstanding, ending balance | shares	524,024
Weighted Average Grant Date Fair Value
Outstanding, beginning balance (in USD per share) | $ / shares	$ 24.59
Granted (in USD per share) | $ / shares	45.42
RS's Vested/RSU's Issued (in USD per share) | $ / shares	0
Forfeited (in USD per share) | $ / shares	0
Outstanding, ending balance (in USD per share) | $ / shares	$ 25.02

Stock-Based Compensation Pla102

Stock-Based Compensation Plans - Summary of Performance Unit Awards (Detail) - Performance Unit Awards	3 Months Ended
	Mar. 31, 2016$ / sharesshares
Number of Units
Outstanding, beginning balance | shares	6,145,442
Granted | shares	2,329,500
Exercised | shares	(1,764,792)
Canceled | shares	(314,972)
Outstanding, ending balance | shares	6,395,178
Weighted Average Grant Date Fair Value
Outstanding, beginning balance (in USD per share) | $ / shares	$ 0.92
Granted (in USD per share) | $ / shares	0.57
Exercised (in USD per share) | $ / shares	0.95
Canceled (in USD per share) | $ / shares	0.93
Outstanding, ending balance (in USD per share) | $ / shares	$ 0.78

Commitments and Contingencies (

Commitments and Contingencies (Detail)	3 Months Ended
	Mar. 31, 2016
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.

Commitments and Contingencie104

Commitments and Contingencies (Environmental Matters) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Accrued liabilities for remediation	$ 166	$ 163
Receivables for recoverable costs	$ 68	$ 70

Commitments and Contingencie105

Commitments and Contingencies (Litigation Relating to the MarkWest Merger) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016USD ($)
MarkWest Merger
Loss Contingencies [Line Items]
Legal Fees	$ 2

Commitments and Contingencie106

Commitments and Contingencies (Other Lawsuits) (Details) - Emergency Pricing And Consumer Protection Laws - Pending Litigation $ in Millions	3 Months Ended
	Mar. 31, 2016USD ($)
Loss Contingencies [Line Items]
Plaintiff	Commonwealth of Kentucky
Alleged amount overcharged from customers	$ 89
Loss contingency, period of occurrence	during September and October 2005

Commitments and Contingencie107

Commitments and Contingencies (Guarantees) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Sep. 30, 2015
Centennial
Loss Contingencies [Line Items]
Equity method investments, ownership percentage	50.00%
Crowley Ocean Partners
Loss Contingencies [Line Items]
Equity method investments, ownership percentage	50.00%	50.00%
Financial Guarantee | LOOP and LOCAP LLC | Guarantee of Indebtedness of Others
Loss Contingencies [Line Items]
Line of credit facility, expiration date	Dec. 31, 2037
Maximum potential undiscounted payments	$ 172
Financial Guarantee | Centennial | Master Shelf Agreement
Loss Contingencies [Line Items]
Line of credit facility, expiration date	Dec. 31, 2024
Maximum potential undiscounted payments	$ 33
Financial Guarantee | Crowley Ocean Partners | Guarantee of Indebtedness of Others
Loss Contingencies [Line Items]
Maximum potential undiscounted payments	81
Financial Guarantee | Crowley Ocean Partners | Guarantee of Indebtedness of Others | Crowley Term Loan
Loss Contingencies [Line Items]
Maximum borrowing capacity	325
Indemnification Agreement | Marathon Oil Companies
Loss Contingencies [Line Items]
Guarantee obligation current carrying value	3
Other Guarantees | Equity method investees
Loss Contingencies [Line Items]
Maximum potential undiscounted payments	89
Guarantee obligations maximum exposure per event	$ 50

Commitments and Contingencie108

Commitments and Contingencies (Contractual Commitments and Contingencies) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016USD ($)
Loss Contingencies [Line Items]
Contractual commitments to acquire property, plant and equipment and advance funds to equity method investees	$ 1,700
Galveston Bay Refinery and Related Assets
Loss Contingencies [Line Items]
Contractual commitments to acquire property, plant and equipment and advance funds to equity method investees	331
North Dakota Pipeline
Loss Contingencies [Line Items]
Contractual commitments to acquire property, plant and equipment and advance funds to equity method investees	625
Crowley Ocean Partners
Loss Contingencies [Line Items]
Contractual commitments to acquire property, plant and equipment and advance funds to equity method investees	$ 69

Subsequent Event (Details)

Subsequent Event (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	Apr. 27, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015
Subsequent Event [Line Items]
Preferred units, value, issued			$ 0	$ 0
Subsequent Event | Series A Convertible Preferred Units
Subsequent Event [Line Items]
Preferred units, description	The Preferred Units are convertible into MPLX common units on a one for one basis after three years, at the purchasers’ option, and after four years at MPLX’s option, subject to certain conditions.
Subsequent Event | MPLX LP | Series A Convertible Preferred Units
Subsequent Event [Line Items]
Preferred units, value, issued	$ 1,000
Preferred units, dividend rate, percentage	6.50%
Preferred units, distribution rate, per-dollar-amount	$ 2.1125
Subsequent Event | MPLX LP | Series A Convertible Preferred Units | Scenario, Forecast
Subsequent Event [Line Items]
Proceeds from issuance of preferred limited partners units		$ 984
Subsequent Event | MPLX LP | Series A Convertible Preferred Units | Preferred Units
Subsequent Event [Line Items]
Shares issued, price per unit	$ 32.50
Sale of units (in number of preferred units)	30.8

Supplementary Statistics - Supp

Supplementary Statistics - Supplementary Statistics (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016		Mar. 31, 2015
Supplementary Statistics [Line Items]
Income from operations		$ 75		$ 1,470
Impairment expense		129		0
Capital expenditures and investments	[1],[2]	684		384
Refining & Marketing
Supplementary Statistics [Line Items]
Impairment expense		0
Speedway
Supplementary Statistics [Line Items]
Impairment expense		0
Midstream
Supplementary Statistics [Line Items]
Impairment expense		129
Operating Segments
Supplementary Statistics [Line Items]
Income from operations	[3]	272		1,550
Capital expenditures and investments	[4]	643		355
Operating Segments | Refining & Marketing
Supplementary Statistics [Line Items]
Income from operations	[5]	(62)		1,292
Capital expenditures and investments	[5]	243		223
Operating Segments | Speedway
Supplementary Statistics [Line Items]
Income from operations		167		168
Capital expenditures and investments		50		45
Operating Segments | Midstream
Supplementary Statistics [Line Items]
Income from operations	[3],[5]	167		90
Capital expenditures and investments	[5]	350		87
Corporate and Other
Supplementary Statistics [Line Items]
Income from operations	[5],[6],[7]	(67)		(79)
Capital expenditures and investments	[2]	41		29
Capitalized interest		17		8
Segment Reconciling Items
Supplementary Statistics [Line Items]
Pension settlement expenses	[8]	(1)		(1)
Impairment expense		$ (129)	[9]	$ 0
[1]	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
[2]	Includes capitalized interest of $17 million and $8 million for the three months ended March 31, 2016 and 2015, respectively.
[3]	Corporate overhead expenses attributable to MPLX are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments.
[4]	Capital expenditures include changes in capital accruals, acquisitions (including any goodwill) and investments in affiliates.
[5]	We revised our operating segment presentation in the first quarter of 2016 in connection with the contribution of our inland marine business to MPLX; our inland marine business, which was previously included in Refining & Marketing, is now included in Midstream. Comparable prior period information has been recast to reflect our revised segment presentation.
[6]	Corporate and other unallocated items consists primarily of MPC’s corporate administrative expenses and costs related to certain non-operating assets.
[7]	Corporate overhead expenses attributable to MPLX are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments.
[8]	See Note 20.
[9]	See Note 14.

Supplementary Statistics - Oper

Supplementary Statistics - Operating Statistics (Detail) bbl / d in Thousands, gal in Millions, CFPD in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2016USD ($)StoreCFPDbbl / d$ / bbl$ / galgal	Mar. 31, 2015USD ($)Storebbl / d$ / bbl$ / galgal
Operating Statistics [Line Items ]
MPC Consolidated Refined Product Sales Volumes (thousands of barrels per day)	[1]	2,158	2,246
Refining & Marketing Operating Statistics
Inventory market valuation charge | $		$ 15	$ 0
Refining & Marketing
Refining & Marketing Operating Statistics
Refining & Marketing refined product sales volume (thousands of barrels per day)		2,148	2,233
Refining & Marketing gross margin (dollars per barrel) | $ / bbl	[2],[3]	9.98	16.14
Inventory market valuation charge | $		$ 15
Crude oil capacity utilization percent	[4]	89.00%	97.00%
Refinery throughputs (thousands of barrels per day)	[5]	1,774	1,852
Sour crude oil throughput percent		61.00%	56.00%
WTI-priced crude oil throughput percent		18.00%	20.00%
Refined product yields (thousands of barrels per day)	[5]	1,810	1,878
Inter-refinery transfers		82	35
Refinery direct operating costs (dollars per barrel):
Planned turnaround and major maintenance | $ / bbl	[6]	2.43	0.79
Depreciation and amortization | $ / bbl	[6]	1.54	1.42
Other manufacturing | $ / bbl	[6],[7]	4.14	4.26
Total | $ / bbl	[6]	8.11	6.47
Refining & Marketing | Crude oil refined
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[5]	1,603	1,672
Refining & Marketing | Other charge and blendstocks
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[5]	171	180
Refining & Marketing | Gasoline
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	899	911
Refining & Marketing | Distillates
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	571	553
Refining & Marketing | Propane
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	32	36
Refining & Marketing | Feedstocks and special products
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	234	298
Refining & Marketing | Heavy fuel oil
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	30	30
Refining & Marketing | Asphalt
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	44	50
Refining & Marketing | Gulf Coast:
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	1,208	1,210
Sour crude oil throughput percent		75.00%	70.00%
WTI-priced crude oil throughput percent		3.00%	5.00%
Refined product yields (thousands of barrels per day)	[8]	1,239	1,226
Refinery direct operating costs (dollars per barrel):
Planned turnaround and major maintenance | $ / bbl	[6]	2.62	0.80
Depreciation and amortization | $ / bbl	[6]	1.17	1.14
Other manufacturing | $ / bbl	[6],[7]	3.74	3.99
Total | $ / bbl	[6]	7.53	5.93
Refining & Marketing | Gulf Coast: | Crude oil refined
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	991	1,031
Refining & Marketing | Gulf Coast: | Other charge and blendstocks
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	217	179
Refining & Marketing | Gulf Coast: | Gasoline
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	533	523
Refining & Marketing | Gulf Coast: | Distillates
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	375	342
Refining & Marketing | Gulf Coast: | Propane
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	25	25
Refining & Marketing | Gulf Coast: | Feedstocks and special products
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	280	307
Refining & Marketing | Gulf Coast: | Heavy fuel oil
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	18	15
Refining & Marketing | Gulf Coast: | Asphalt
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	8	14
Refining & Marketing | Midwest:
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	648	677
Sour crude oil throughput percent		39.00%	34.00%
WTI-priced crude oil throughput percent		42.00%	43.00%
Refined product yields (thousands of barrels per day)	[8]	653	687
Refinery direct operating costs (dollars per barrel):
Planned turnaround and major maintenance | $ / bbl	[6]	1.76	0.73
Depreciation and amortization | $ / bbl	[6]	2.03	1.85
Other manufacturing | $ / bbl	[6],[7]	4.36	4.51
Total | $ / bbl	[6]	8.15	7.09
Refining & Marketing | Midwest: | Crude oil refined
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	612	641
Refining & Marketing | Midwest: | Other charge and blendstocks
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	36	36
Refining & Marketing | Midwest: | Gasoline
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	366	388
Refining & Marketing | Midwest: | Distillates
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	196	211
Refining & Marketing | Midwest: | Propane
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	9	13
Refining & Marketing | Midwest: | Feedstocks and special products
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	34	23
Refining & Marketing | Midwest: | Heavy fuel oil
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	12	16
Refining & Marketing | Midwest: | Asphalt
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	36	36
Speedway
Speedway Operating Statistics
Convenience stores at period-end | Store		2,771	2,753
Gasoline and distillate sales (millions of gallons) | gal		1,483	1,432
Gasoline and distillate gross margin (dollars per gallon) | $ / gal	[9]	0.1682	0.1970
Merchandise sales (in millions) | $		$ 1,152	$ 1,111
Merchandise gross margin (in millions) | $		$ 330	$ 311
Merchandise margin percent		29.00%	28.00%
Same store gasoline sales volume (period over period) percentage		1.00%	(1.20%)
Merchandise sales excluding cigarettes (period over period) percentage	[10]	3.10%	6.20%
Midstream
Midstream Operating Statistics
Crude oil and refined product pipeline throughputs (thousands of barrels per day)		2,181	2,107
Gathering system throughput (MMcf/d) | CFPD		3,345
Natural gas processed (MMcf/d) | CFPD		5,636
C2 and NGLs fractionated (thousands barrels per day)		312
[1]	Total average daily volumes of refined product sales to wholesale, branded and retail (Speedway segment) customers.
[2]	Excludes the lower of cost or market inventory valuation charge of $15 million for the first quarter of 2016.
[3]	Sales revenue less cost of refinery inputs and purchased products, divided by total refinery throughputs.
[4]	Based on calendar day capacity, which is an annual average that includes downtime for planned maintenance and other normal operating activities.
[5]	Excludes inter-refinery volumes of 82 mbpd and 35 mbpd for the three months ended March 31, 2016 and 2015, respectively.
[6]	Per barrel of total refinery throughputs.
[7]	Includes utilities, labor, routine maintenance and other operating costs.
[8]	Includes inter-refinery transfer volumes.
[9]	The price paid by consumers less the cost of refined products, including transportation, consumer excise taxes and bankcard processing fees, divided by gasoline and distillate sales volume.
[10]	Excludes cigarettes.