Marathon Petroleum (MPC) 10-Q 30 Apr 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 26, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
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		461,878,776

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Revenues and other income:
Sales and other operating revenues	[1]	$ 18,694	$ 16,134
Sales to related parties		172	154
Income from equity method investments		86	57
Net gain on disposal of assets		2	5
Other income		30	43
Total revenues and other income		18,984	16,393
Costs and expenses:
Cost of revenues (excludes items below)	[1]	17,370	14,946
Purchases from related parties		141	122
Depreciation and amortization		528	536
Selling, general and administrative expenses		402	390
Other taxes		103	108
Total costs and expenses		18,544	16,102
Income from operations		440	291
Net interest and other financial costs		183	149
Income before income taxes		257	142
Provision for income taxes		22	41
Net income		235	101
Less net income attributable to:
Redeemable noncontrolling interest		16	16
Noncontrolling interests		182	55
Net income attributable to MPC		$ 37	$ 30
Basic:
Net income attributable to MPC per share		$ 0.08	$ 0.06
Weighted average shares outstanding (in shares)		476	525
Diluted:
Net income attributable to MPC per share		$ 0.08	$ 0.06
Weighted average shares outstanding (in shares)		480	530
Dividends paid (in USD per share)		$ 0.46	$ 0.36
[1]	The 2018 period reflects an election to present certain taxes on a net basis. See Notes 2 and 3 for further information.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 235	$ 101
Defined benefit postretirement and post-employment plans:
Actuarial changes, net of tax of $3 and $3	7	4
Prior service costs, net of tax of ($2) and ($4)	(7)	(7)
Other, net of tax of ($1) and $0	(2)	0
Other comprehensive loss	(2)	(3)
Comprehensive income	233	98
Less comprehensive income attributable to:
Redeemable noncontrolling interest	16	16
Noncontrolling interests	182	55
Comprehensive income attributable to MPC	$ 35	$ 27

Consolidated Statements of Com4

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Actuarial changes, tax	$ 3	$ 3
Prior service costs, tax	(2)	(4)
Other, tax	$ (1)	$ 0

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents (MPLX: $2 and $5, respectively)	$ 4,653	$ 3,011
Receivables, less allowance for doubtful accounts of $10 and $11 (MPLX: $322 and $299, respectively)	4,613	4,695
Inventories (MPLX: $64 and $65, respectively)	5,111	5,550
Other current assets (MPLX: $26 and $29, respectively)	148	145
Total current assets	14,525	13,401
Equity method investments (MPLX: $4,033 and $4,010, respectively)	4,817	4,787
Property, plant and equipment, net (MPLX: $13,291 and $12,187, respectively)	26,618	26,443
Goodwill (MPLX: $2,460 and $2,245, respectively)	3,586	3,586
Other noncurrent assets (MPLX: $472 and $479, respectively)	818	830
Total assets	50,364	49,047
Current liabilities:
Accounts payable (MPLX: $543 and $621, respectively)	7,066	8,297
Payroll and benefits payable (MPLX: $2 and $1, respectively)	337	591
Accrued taxes (MPLX: $34 and $38, respectively)	639	670
Debt due within one year (MPLX: $1 and $1, respectively)	26	624
Other current liabilities (MPLX: $138 and $130, respectively)	304	296
Total current liabilities	8,372	10,478
Long-term debt (MPLX: $11,861 and $6,945, respectively)	17,232	12,322
Deferred income taxes (MPLX: $10 and $5, respectively)	3,120	2,654
Defined benefit postretirement plan obligations	1,126	1,099
Deferred credits and other liabilities (MPLX: $232 and $230, respectively)	651	666
Total liabilities	30,501	27,219
Commitments and contingencies (see Note 22)
Redeemable noncontrolling interest	1,000	1,000
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 – 734 million and 734 million shares (par value 0.01 per share, 1 billion shares authorized)	7	7
Held in treasury, at cost – 267 million and 248 million shares	(11,200)	(9,869)
Additional paid-in capital	13,669	11,262
Retained earnings	12,745	12,864
Accumulated other comprehensive loss	(233)	(231)
Total MPC stockholders’ equity	14,988	14,033
Noncontrolling interests	3,875	6,795
Total equity	18,863	20,828
Total liabilities, redeemable noncontrolling interest and equity	$ 50,364	$ 49,047

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 10	$ 11
Preferred stock:
Shares issued	0	0
Shares outstanding	0	0
Par value	$ 0.01
Shares authorized	30,000,000
Common stock:
Shares issued	734,000,000	734,000,000
Par value	$ 0.01
Shares authorized	1,000,000,000
Treasury stock	(267,000,000)	(248,000,000)

Consolidated Balance Sheets (MP

Consolidated Balance Sheets (MPLX Parenthetical) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Assets
Cash and cash equivalents	$ 4,653	$ 3,011
Receivables, less allowance for doubtful accounts	4,613	4,695
Inventories	5,111	5,550
Other current assets	148	145
Equity method investments	4,817	4,787
Property, plant and equipment, net	26,618	26,443
Goodwill	3,586	3,586
Other noncurrent assets	818	830
Liabilities
Accounts payable	7,066	8,297
Payroll and benefits payable	337	591
Accrued taxes	639	670
Debt due within one year	26	624
Other current liabilities	304	296
Total long-term debt due after one year	17,232	12,322
Deferred income taxes (MPLX: $10 and $5, respectively)	3,120	2,654
Defined benefit postretirement plan obligations	1,126	1,099
Deferred credits and other liabilities	651	666
MPLX LP
Assets
Cash and cash equivalents	2	5
Receivables, less allowance for doubtful accounts	322	299
Inventories	64	65
Other current assets	26	29
Equity method investments	4,033	4,010
Property, plant and equipment, net	13,291	12,187
Goodwill	2,460	2,245
Other noncurrent assets	472	479
Liabilities
Accounts payable	543	621
Payroll and benefits payable	2	1
Accrued taxes	34	38
Debt due within one year	1	1
Other current liabilities	138	130
Total long-term debt due after one year	11,861	6,945
Deferred income taxes (MPLX: $10 and $5, respectively)	10	5
Defined benefit postretirement plan obligations	0	0
Deferred credits and other liabilities	$ 232	$ 230

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018		Mar. 31, 2017
Operating activities:
Net income	$ 235		$ 101
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred financing costs and debt discount	18		15
Depreciation and amortization	528		536
Pension and other postretirement benefits, net	32		27
Deferred income taxes	(19)		(5)
Net gain on disposal of assets	(2)		(5)
Income from equity method investments	(86)		(57)
Distributions from equity method investments	89		56
Changes in the fair value of derivative instruments	(14)		28
Changes in:
Current receivables	96		333
Inventories	440		264
Current accounts payable and accrued liabilities	(1,455)		(215)
All other, net	1		30
Net cash provided by (used in) operating activities	(137)		1,108
Investing activities:
Additions to property, plant and equipment	(755)		(610)
Acquisitions, net of cash acquired	0		(220)
Disposal of assets	7		2
Investments – acquisitions, loans and contributions	(41)		(566)
Investments - redemptions, repayments and return of capital	0		20
All other, net	11		21
Net cash used in investing activities	(778)		(1,353)
Financing activities:
Commercial paper – issued	0		300
Commercial paper - repayments	0		(300)
Long-term debt – borrowings	9,610		2,241
Long-term debt – repayments	(5,264)		(207)
Debt issuance costs	(53)		(21)
Issuance of common stock	12		10
Common stock repurchased	(1,327)		(420)
Dividends paid	(219)		(190)
Issuance of MPLX LP common units	0		148
Distributions to noncontrolling interests	(195)		(158)
Contributions from noncontrolling interests	1		126
All other, net	(8)		(6)
Net cash provided by financing activities	2,557		1,523
Net increase in cash, cash equivalents and restricted cash	1,642		1,278
Cash, cash equivalents and restricted cash at beginning of period	3,015	[1]	892
Cash, cash equivalents and restricted cash at end of period	$ 4,657	[1]	$ 2,170
[1]	As a result of the adoption of ASU 2016-18, the consolidated statements of cash flows now explain the change during the period of both “Cash and cash equivalents” and “Restricted cash.”

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 Loss	Non-controlling Interests
Beginning balance at Dec. 31, 2016	$ 20,203	$ 7	$ (7,482)	$ 11,060	$ 10,206	$ (234)	$ 6,646
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	85				30		55
Dividends declared	(190)				(190)
Distributions to noncontrolling interests	(142)						(142)
Contributions from noncontrolling interests	126						126
Other comprehensive loss	(3)					(3)
Shares repurchased	(420)		(420)
Shares returned - stock based compensation			(3)
Shares issued - stock based compensation				27
Net shares issued - stock based compensation	24
Impact from equity transactions of MPLX LP	114			72			42
Ending balance at Mar. 31, 2017	19,797	7	(7,905)	11,159	10,046	(237)	6,727
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of new accounting principle in period of adoption	64				63		1
Beginning balance at Dec. 31, 2017	20,828	7	(9,869)	11,262	12,864	(231)	6,795
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	219				37		182
Dividends declared	(219)				(219)
Distributions to noncontrolling interests	(179)						(179)
Contributions from noncontrolling interests	1						1
Other comprehensive loss	(2)					(2)
Shares repurchased	(1,327)		(1,327)
Shares returned - stock based compensation			(4)
Shares issued - stock based compensation				27
Net shares issued - stock based compensation	24						1
Impact from equity transactions of MPLX LP	(546)			2,380			(2,926)
Ending balance at Mar. 31, 2018	$ 18,863	$ 7	$ (11,200)	$ 13,669	$ 12,745	$ (233)	$ 3,875

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, 2016		731
Number of common shares issued (ending balance) at Mar. 31, 2017		731
Number of shares held in treasury (beginning balance) at Dec. 31, 2016			(203)
Number of shares repurchased	(9)		(9)
Number of shares held in treasury (ending balance) at Mar. 31, 2017			(212)
Number of common shares issued (beginning balance) at Dec. 31, 2017	734	734
Number of common shares issued (ending balance) at Mar. 31, 2018	734	734
Number of shares held in treasury (beginning balance) at Dec. 31, 2017	(248)		(248)
Number of shares repurchased	(19)		(19)
Number of shares held in treasury (ending balance) at Mar. 31, 2018	(267)		(267)

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interest - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Temporary Equity [Abstract]
Beginning balance	$ 1,000	$ 1,000
Net income attributable to redeemable noncontrolling interest	16	16
Distributions to noncontrolling interests	(16)	(16)
Ending balance	$ 1,000	$ 1,000

Description of the Business and

Description of the Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2018
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 (“MPC LP”), Speedway LLC and its subsidiaries (“Speedway”) and MPLX LP and its subsidiaries (“MPLX”). See Note 10 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 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, 2017 . The results of operations for the three months ended March 31, 2018 are not necessarily indicative of the results to be expected for the full year. Certain prior period financial statement amounts have been reclassified to conform to current period presentation.

Summary of Principal Accounting

Summary of Principal Accounting Policies	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Summary of Principal Accounting Policies	Summary of Principal Accounting Policies Revenue Recognition - As described in Note 3 , we adopted ASU 2014-09, Revenue from Contracts with Customers (ASC 606) effective January 1, 2018. We recognize revenue based on consideration specified in contracts or agreements with customers when we satisfy our performance obligations by transferring control over products or services to a customer. Concurrent with our adoption of ASC 606, we made an accounting policy election that all taxes assessed by a governmental authority that are both imposed on and concurrent with a revenue-producing transaction and collected from our customers will be recognized on a net basis within “Sales and other operating revenues”. The adoption of ASC 606 did not materially change our revenue recognition patterns, which are described below by reportable segment: • Refining & Marketing - The vast majority of our Refining & Marketing contracts contain pricing that is based on the market price for the product at the time of delivery. Our obligations to deliver product volumes are typically satisfied and revenue is recognized when control of the product transfers to our customers. Concurrent with the transfer of control, we typically receive the right to payment for the delivered product, the customer accepts the product and the customer has significant risks and rewards of ownership of the product. Payment terms require customers to pay shortly after delivery and do not contain significant financing components. • Speedway - Revenue is recognized when our customers receive control of the transportation fuels or merchandise. Payments from customers are received at the time sales occur in cash or by credit or debit card. Speedway offers a loyalty rewards program to its customers. We defer a minor portion of revenue on sales to the loyalty program participants until the participants redeem their rewards. The related contract liability, as defined in the standard, is not material to our financial statements. • Midstream - Midstream revenue transactions typically are defined by contracts under which we sell a product or provide a service. Revenues from sales of product are recognized when control of the product transfers to the customer. Revenues from sales of services are recognized over time when the performance obligation is satisfied as services are provided in a series. We have elected to use the output measure of progress to recognize revenue based on the units delivered, processed or transported. The transaction price in our Midstream contracts often has both fixed components, related to minimum volume commitments, and variable components which are primarily dependent on volumes. Variable consideration will generally not be estimated at contract inception as the transaction price is specifically allocable to the services provided each period end. Refer to Note 10 for disclosure of our revenue disaggregated by segment and product line, as well as a description of our reportable segment operations.

Accounting Standards

Accounting Standards	3 Months Ended
	Mar. 31, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recently Adopted	Accounting Standards Recently Adopted ASU 2014-09, Revenue - Revenue from Contracts with Customers (ASC 606). On January 1, 2018, we adopted the new revenue standard, applying the modified retrospective method, whereby a cumulative effect is recorded to opening retained earnings and ASC 606 is applied prospectively. We recorded a net increase of $1 million to our retained earnings balance as of January 1, 2018 due to the cumulative effect of applying the new revenue standard. Impact of Adoption The adoption of ASC 606 did not materially change our revenue recognition patterns. The most significant impacts of adopting ASC 606 for the period ended March 31, 2018 are as follows: • a reduction of “Sales and other operating revenues” of $1.25 billion for the three months ended March 31, 2018 due to our accounting policy election to present taxes incurred concurrently with revenue producing transactions and collected on behalf of our customers on a net basis. For the three months ended March 31, 2017 , taxes are reflected on a gross basis in “Sales and other operating revenues” and “Cost of revenues”, and include $1.20 billion of taxes that are now subject to our net basis accounting policy election. • an increase to both “Sales and other operating revenues” and “Cost of revenues” of $117 million for the three months ended March 31, 2018 related to certain Midstream contract provisions for third party reimbursements, noncash consideration and imbalances that require gross presentation under ASC 606. Comparative information continues to be reported under the accounting standards in effect for those periods. Practical Expedients We elected the completed contract practical expedient and only applied ASC 606 to contracts that were not completed as of January 1, 2018. We do not disclose information on the future performance obligations for any contract with expected duration of one year or less at inception. As of March 31, 2018 , we do not have future performance obligations that are material to future periods. Receivables On the accompanying consolidated balance sheets, “Receivables, less allowance for doubtful accounts” primarily consists of customer receivables. Significant, non-customer balances included in our receivables at March 31, 2018 include matching buy/sell receivables of $1.33 billion and income taxes receivables of $323 million . ASU 2016-16, Income Taxes - Intra-Entity Transfers of Assets Other Than Inventory. We adopted this accounting standards update in the first quarter of 2018 and recorded a $61 million cumulative-effect adjustment as an increase to retained earnings as of January 1, 2018 with the offset recorded as a reduction to “Deferred Income Taxes”. We also adopted the following standards during the first quarter of 2018, none of which had a material impact to our financial statements or financial statement disclosures: ASU Effective Date 2017-09 Stock Compensation - Scope of Modification Accounting January 1, 2018 2017-07 Retirement Benefits - Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Cost January 1, 2018 2017-05 Gains and Losses from the Derecognition of Nonfinancial Assets - Clarifying the Scope of Asset Derecognition Guidance January 1, 2018 2017-01 Business Combinations - Clarifying the Definition of a Business January 1, 2018 2016-18 Statement of Cash Flows - Restricted Cash January 1, 2018 2016-15 Statement of Cash Flows - Classification of Certain Cash Receipts and Cash Payments January 1, 2018 2016-01 Financial Instruments - Recognition and Measurement of Financial Assets and Liabilities January 1, 2018
Not Yet Adopted	Not Yet Adopted ASU 2018-02, Reporting Comprehensive Income - Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. In February 2018, the FASB issued an accounting standards update allowing an entity the choice to reclassify to retained earnings the tax effects related to the Tax Cuts and Jobs Act that are stranded in accumulated other comprehensive income. We do not expect adoption of this standard to have a material impact on our financial statements. The amendment is effective beginning in 2019 with early adoption permitted. ASU 2017-12, Derivatives and Hedging - Targeted Improvements to Accounting for Hedging Activities. In August 2017, the FASB issued an accounting standards update to amend the hedge accounting rules to simplify the application of hedge accounting guidance and better portray the economic results of risk management activities in the financial statements. The guidance expands the ability to hedge nonfinancial and financial risk components, reduces complexity in fair value hedges of interest rate risk, eliminates the requirement to separately measure and report hedge ineffectiveness, as well as eases certain hedge effectiveness assessment requirements. The guidance is effective beginning in 2019 with early adoption permitted. We are currently evaluating the impact of this guidance, including transition elections and required disclosures, on our financial statements and the timing of adoption. However, since we have not historically designated our commodity derivatives as hedges, we do not expect the adoption of this accounting standards update to have a material impact on our consolidated financial statements. ASU 2017-04, Intangibles - Goodwill and Other - Simplifying the Test for Goodwill Impairment. In January 2017, the FASB issued an accounting standards update which simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test. Under the new guidance, the recognition of an impairment charge is calculated based on the amount by which the carrying amount exceeds the reporting unit’s fair value, which could be different from the amount calculated under the current method using the implied fair value of the goodwill; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. The guidance should be applied on a prospective basis, and is effective for annual or any interim goodwill impairment tests in fiscal years beginning after December 15, 2019. ASU 2016-13, Credit Losses - Measurement of Credit Losses on Financial Instruments. In June 2016, the FASB issued an accounting standards update related to the accounting for credit losses on certain financial instruments. The guidance requires that for most financial assets, losses be based on an expected loss approach which includes estimates of losses over the life of exposure that considers historical, current and forecasted information. Expanded disclosures related to the methods used to estimate the losses as well as a specific disaggregation of balances for financial assets are also required. The change is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years, with early adoption permitted for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. We do not expect application of this accounting standards update to have a material impact on our consolidated financial statements. ASU 2016-02, Leases. In February 2016, the FASB issued an accounting standards update requiring lessees to record virtually all leases on their balance sheets. The accounting standards update also requires expanded disclosures to help financial statement users better understand the amount, timing and uncertainty of cash flows arising from leases. For lessors, this amended guidance modifies the classification criteria and the accounting for sales-type and direct financing leases. The change will be effective on a modified retrospective basis for fiscal years beginning after December 15, 2018, and interim periods within those years, with early adoption permitted. We continue to evaluate the impact of this standard on our financial statements and disclosures, internal controls and accounting policies. This evaluation process includes reviewing all forms of leases, performing a completeness assessment over the lease population and analyzing the practical expedients in order to determine the best path of implementing changes to existing processes and controls. We are implementing a third-party supported lease accounting information system to account for our lease population in accordance with this new standard and establishing internal controls over the new system. We believe the adoption of the standard will have a material impact on our consolidated financial statements as virtually all leases will be recognized as a right of use asset and lease obligation.

MPLX LP

MPLX LP	3 Months Ended
	Mar. 31, 2018
Noncontrolling Interest [Abstract]
MPLX LP	MPLX LP MPLX is a diversified, growth-oriented publicly traded master limited partnership formed by us to own, operate, develop and acquire midstream energy infrastructure assets. MPLX is engaged in the gathering, processing and transportation of natural gas; the gathering, transportation, fractionation, storage and marketing of NGLs; and the transportation, storage, distribution and marketing of crude oil and refined petroleum products. As of March 31, 2018 , we owned 63.6 percent of the outstanding MPLX common units and control MPLX through our ownership of the general partner interest in MPLX. 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 our significant economic interest, we also have the power, through our 100 percent ownership of the general partner, to control the decisions that most significantly impact MPLX. We therefore consolidate MPLX and record a noncontrolling interest for the 36.4 percent interest owned by the public. We also record a redeemable noncontrolling interest related to MPLX’s preferred units. The creditors of MPLX do not have recourse to MPC’s general credit through guarantees or other financial arrangements. The assets of MPLX are the property of MPLX and cannot be used to satisfy the obligations of MPC. MPC has effectively guaranteed certain indebtedness of LOOP LLC (“LOOP”) and LOCAP LLC (“LOCAP”), in which MPLX holds an interest. See Note 22 for more information. Dropdowns to MPLX and GP/IDR Exchange On February 1, 2018, we contributed our refining logistics assets and fuels distribution services to MPLX in exchange for $4.1 billion in cash and approximately 112 million common units and 2 million general partner units from MPLX. MPLX financed the cash portion of the transaction with its $4.1 billion 364 -day term loan facility, which was entered into on January 2, 2018. We agreed to waive approximately one-third of the first quarter 2018 distributions on the common units issued in connection with this transaction. The contributions of these assets were accounted for as transactions between entities under common control and we did not record a gain or loss. Immediately following the February 1, 2018 dropdown to MPLX, our IDRs were cancelled and our economic general partner interest was converted into a non-economic general partner interest, all in exchange for 275 million newly issued MPLX common units (“GP/IDR Exchange”). As a result of this transaction, the general partner units and IDRs were eliminated, are no longer outstanding and no longer participate in distributions of cash from MPLX. On September 1, 2017, we contributed our joint-interest ownership in certain pipelines and storage facilities to MPLX in exchange for $420 million in cash and approximately 19 million common units and 378 thousand general partner units from MPLX. We also agreed to waive approximately two-thirds of the third quarter 2017 common unit distributions, IDRs and general partner distributions with respect to the common units issued in this transaction. The contributions of these assets were accounted for as transactions between entities under common control and we did not record a gain or loss. On March 1, 2017, we contributed certain terminal, pipeline and storage assets to MPLX in exchange for $1.5 billion in cash and approximately 13 million common units and 264 thousand general partner units from MPLX. We also agreed to waive two-thirds of the first quarter 2017 common unit distributions, IDRs and general partner distributions with respect to the common units issued in this transaction. The contributions of these assets were accounted for as transactions between entities under common control and we did not record a gain or loss. Noncontrolling Interest in MPLX As a result of equity transactions of MPLX, we are required to adjust non-controlling interest and additional paid-in capital. Changes in MPC’s additional paid-in capital resulting from changes in its ownership interests in MPLX were as follows: Three Months Ended (In millions) 2018 2017 Increase due to the issuance of MPLX LP common units to the public $ 4 $ 10 Increase due to the issuance of MPLX LP common units and general partner units to MPC 1,114 96 Increase due to GP/IDR Exchange 1,808 — Increase in MPC's additional paid-in capital 2,926 106 Tax impact (546 ) (34 ) Increase in MPC's additional paid-in capital, net of tax $ 2,380 $ 72 Agreements We have various long-term, fee-based commercial agreements with MPLX. Under these agreements, MPLX provides transportation, storage, distribution and marketing services to us. Under certain agreements, we commit to provide MPLX with minimum quarterly throughput and distribution volumes of crude oil and refined products and minimum storage volumes of crude oil, refined products and butane. Under certain other agreements, we commit to pay for 100 percent of available capacity for certain marine transportation and refining logistics assets. 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, but are reflected as intersegment transactions between our Refining & Marketing and Midstream segments.

Acquisitions and Investments

Acquisitions and Investments	3 Months Ended
	Mar. 31, 2018
Business Combinations [Abstract]
Acquisitions and Investments	Acquisitions and Investments Acquisition of Ozark Pipeline On March 1, 2017, MPLX acquired the Ozark pipeline from Enbridge Pipelines (Ozark) LLC for approximately $219 million , including purchase price adjustments made in the second quarter of 2017. Based on the fair value of assets acquired and liabilities assumed at the acquisition date, the final purchase price was primarily allocated to property, plant and equipment. The Ozark pipeline is a 433 -mile, 22 -inch crude oil pipeline originating in Cushing, Oklahoma, and terminating in Wood River, Illinois, capable of transporting approximately 230 mbpd. We account for the Ozark pipeline within the Midstream segment. Assuming the acquisition of the Ozark pipeline had occurred on January 1, 2016, the consolidated pro forma results would not have been materially different from reported results. Investment in Pipeline Company On February 15, 2017, MPLX acquired a partial, indirect equity interest in the Dakota Access Pipeline (“DAPL”) and Energy Transfer Crude Oil Company Pipeline (“ETCOP”) projects, collectively referred to as the Bakken Pipeline system, through a joint venture with Enbridge Energy Partners L.P. (“Enbridge Energy Partners”). The Bakken Pipeline system is capable of transporting more than 520 mbpd of crude oil from the Bakken/Three Forks production area in North Dakota to the Midwest through Patoka, Illinois and ultimately to the Gulf Coast. MPLX contributed $500 million of the $2 billion purchase price paid by the joint venture, MarEn Bakken Company LLC (“MarEn Bakken”), to acquire a 36.75 percent indirect equity interest in the Bakken Pipeline system from Energy Transfer Partners, L.P. (“ETP”) and Sunoco Logistics Partners, L.P. (“SXL”). MPLX holds, through a subsidiary, a 25 percent interest in MarEn Bakken, which equates to an approximate 9.2 percent indirect equity interest in the Bakken Pipeline system. We account for the investment in MarEn Bakken as part of our Midstream segment using the equity method of accounting. Formation of Gathering and Processing Joint Venture Effective January 1, 2017, MPLX and Antero Midstream formed a joint venture, Sherwood Midstream LLC (“Sherwood Midstream”), to support the development of Antero Resources Corporation’s Marcellus Shale acreage in West Virginia. MPLX has a 50 percent ownership interest in Sherwood Midstream. In connection with this transaction, MPLX contributed certain gas processing plants currently under construction at the Sherwood Complex with a fair value of approximately $134 million and cash of approximately $20 million . Antero Midstream made an initial capital contribution of approximately $154 million . Also effective January 1, 2017, MPLX converted all of its ownership interests in MarkWest Ohio Fractionation Company, L.L.C. (“Ohio Fractionation”), a previously wholly-owned subsidiary, to Class A Interests and amended its LLC Agreement to create Class B-3 Interests, which were sold to Sherwood Midstream for $126 million in cash. The Class B-3 Interests provide Sherwood Midstream with the right to fractionation revenue and the obligation to pay expenses related to 20 mbpd of capacity in the Hopedale 3 fractionator. Effective January 1, 2017, MPLX and Sherwood Midstream formed a joint venture, Sherwood Midstream Holdings LLC (“Sherwood Midstream Holdings”), for the purpose of owning, operating and maintaining all of the shared assets for the benefit of and use in the operation of the gas plants and other assets owned by Sherwood Midstream and the gas plants and deethanization facilities owned by MPLX. MPLX contributed certain real property, equipment and facilities with a fair value of approximately $209 million to Sherwood Midstream Holdings in exchange for a 79 percent initial ownership interest. Sherwood Midstream contributed cash of approximately $44 million to Sherwood Midstream Holdings in exchange for a 21 percent ownership interest. MPLX has a 10.5 percent indirect interest in Sherwood Midstream Holdings through its ownership in Sherwood Midstream. The net book value of the contributed assets was approximately $203 million . The contribution was determined to be an in-substance sale of real estate. As such, MPLX only recognized a gain for the portion attributable to Antero Midstream’s indirect interest of approximately $2 million . During the three months ended March 31, 2018, MarkWest Liberty Midstream sold to Sherwood Midstream 6 percent of their equity ownership in Sherwood Midstream Holdings for $15 million . We account for our direct interests in Sherwood Midstream and Sherwood Midstream Holdings as part of our Midstream segment using the equity method of accounting. We continue to consolidate Ohio Fractionation and have recognized a noncontrolling interest for Sherwood Midstream’s interest in that entity. See Note 6 for additional information related to the investments in Sherwood Midstream, Ohio Fractionation and Sherwood Midstream Holdings.

Variable Interest Entities

Variable Interest Entities	3 Months Ended
	Mar. 31, 2018
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Variable Interest Entities	Variable Interest Entities In addition to MPLX, as described in Note 4 , the following entities are also VIEs. Crowley Coastal Partners In May 2016, Crowley Coastal Partners was formed to own an interest in both Crowley Ocean Partners and Crowley Blue Water Partners. We have determined that Crowley Coastal Partners is a VIE based on the terms of the existing financing arrangements for Crowley Blue Water Partners and Crowley Ocean Partners and the associated debt guarantees by MPC and Crowley. Our maximum exposure to loss at March 31, 2018 was $487 million , which includes our equity method investment in Crowley Coastal Partners and the debt guarantees provided to each of the lenders to Crowley Blue Water Partners and Crowley Ocean Partners. We are not the primary beneficiary of this VIE because we do not have the power to control the activities that significantly influence the economic outcomes of the entity and, therefore, do not consolidate the entity. 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. As of March 31, 2018 , MarkWest had a 56 percent 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, 2018 was $2.1 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, 2018 , we had a 34 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. Sherwood Midstream As described in Note 5 , MPLX and Antero Midstream formed a joint venture, Sherwood Midstream, to support the development of Antero Resources Corporation’s Marcellus Shale acreage in West Virginia. As of March 31, 2018 , MPLX had a 50 percent ownership interest in Sherwood Midstream. Sherwood Midstream’s inability to fund its planned activities without additional subordinated financial support qualify it as a VIE. MPLX is not deemed to be the primary beneficiary, due to Antero Midstream’s voting rights on significant matters. We account for our ownership interest in Sherwood Midstream using the equity method of accounting. Our maximum exposure to loss as a result of our involvement with Sherwood Midstream 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 Sherwood Midstream at March 31, 2018 was $260 million . Ohio Fractionation As described in Note 5 , MPLX converted all of its ownership interests in Ohio Fractionation to Class A Interests and amended its LLC Agreement to create Class B-3 Interests, which were sold to Sherwood Midstream, providing it with the right to fractionation revenue and the obligation to pay expenses related to 20 mbpd of capacity in the Hopedale 3 fractionator. Ohio Fractionation’s inability to fund its operations without additional subordinated financial support qualify it as a VIE. MPLX has been deemed to be the primary beneficiary of Ohio Fractionation because it has control over decisions that could significantly impact its financial performance, and as a result, consolidates Ohio Fractionation. Sherwood Midstream Holdings As described in Note 5 , MPLX and Sherwood Midstream entered into a joint venture, Sherwood Midstream Holdings, for the purpose of owning, operating and maintaining all of the shared assets for the benefit of and use in the operation of the gas plants and other assets owned by Sherwood Midstream and the gas plants and deethanization facilities owned by MPLX. MPLX had an initial 79 percent direct ownership in Sherwood Midstream Holdings, in addition to a 10.5 percent indirect interest through its ownership in Sherwood Midstream. Sherwood Midstream Holdings’ inability to fund its operations without additional subordinated financial support qualify it as a VIE. We account for our ownership interest in Sherwood Midstream Holdings using the equity method of accounting as Sherwood Midstream is considered to be the general partner and controls all decisions related to Sherwood Midstream Holdings. Our maximum exposure to loss as a result of our involvement with Sherwood Midstream Holdings 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 Sherwood Midstream Holdings at March 31, 2018 was $151 million .

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Our related parties include: • Crowley Blue Water Partners, in which we have a 50 percent indirect noncontrolling interest. Crowley Blue Water Partners owns and operates three Jones Act ATB vessels. • Crowley Ocean Partners, in which we have a 50 percent indirect noncontrolling interest. Crowley Ocean Partners owns and operates Jones Act product tankers. • Illinois Extension Pipeline Company, L.L.C. (“Illinois Extension Pipeline”), in which we have a 35 percent noncontrolling interest. Illinois Extension Pipeline owns and operates the Southern Access Extension (“SAX”) crude oil pipeline. • LOCAP, in which we have a 59 percent noncontrolling interest. LOCAP owns and operates a crude oil pipeline. • LOOP, in which we have a 51 percent noncontrolling interest. LOOP owns and operates the only U.S. deepwater crude oil port. • MarkWest Utica EMG, in which we have a 56 percent noncontrolling interest. MarkWest Utica EMG is engaged in natural gas processing and NGL fractionation, transportation and marketing in Ohio. • Ohio Gathering, in which we have a 34 percent indirect noncontrolling interest. Ohio Gathering is a subsidiary of MarkWest Utica EMG providing natural gas gathering service in the Utica Shale region of eastern Ohio. • PFJ Southeast, in which we have a 29 percent noncontrolling interest. PFJ Southeast owns and operates travel plazas primarily in the Southeast region of the United States. • Sherwood Midstream, in which we have a 50 percent noncontrolling interest. Sherwood Midstream supports the development of Antero Resources Corporation’s Marcellus Shale acreage in West Virginia. • Sherwood Midstream Holdings, in which we have an 81 percent direct and indirect noncontrolling interest. Sherwood Midstream Holdings owns certain infrastructure at the Sherwood Complex that is shared by and supports the operation of both the Sherwood Midstream and MarkWest gas processing plants and deethanization facilities. • 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 61 percent noncontrolling interest and The Andersons Marathon Ethanol LLC (“TAME”), in which we have a 67 percent 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 were as follows: Three Months Ended (In millions) 2018 2017 PFJ Southeast $ 169 $ 151 Other equity method investees 3 3 Total $ 172 $ 154 Sales to related parties consists primarily of sales of refined products. Other income from related parties, which is included in “Other income” on the accompanying consolidated statements of income, were as follows: Three Months Ended (In millions) 2018 2017 MarkWest Utica EMG $ 4 $ 4 Ohio Gathering 4 4 Sherwood Midstream 3 1 Other equity method investees 2 2 Total $ 13 $ 11 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) 2018 2017 Crowley Blue Water Partners $ 16 $ 14 Crowley Ocean Partners 20 19 Illinois Extension Pipeline 24 25 LOCAP 4 5 LOOP 17 13 TAAE 19 8 TACE 8 16 TAME 20 17 Other equity method investees 13 5 Total $ 141 $ 122 Related party purchases from Crowley Blue Water Partners and Crowley Ocean Partners consist of leasing marine equipment primarily used to transport refined products. 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 TAAE, TACE and TAME consist of ethanol purchases. Receivables from related parties, which are included in “Receivables, less allowance for doubtful accounts” on the accompanying consolidated balance sheets, were as follows: (In millions) March 31, December 31, PFJ Southeast $ 30 $ 28 Sherwood Midstream Holdings 15 — Other equity method investees 7 8 Total $ 52 $ 36 The long-term receivable, which is included in “Other noncurrent assets” on the accompanying consolidated balance sheet, was $1 million at March 31, 2018 and $1 million at December 31, 2017 . Payables to related parties, which are included in “Accounts payable” on the accompanying consolidated balance sheets, were as follows: (In millions) March 31, December 31, Illinois Extension Pipeline $ 7 $ 8 LOOP 2 3 MarkWest Utica EMG 20 29 Ohio Gathering 1 9 Sherwood Midstream 11 8 Other equity method investees 10 12 Total $ 51 $ 69 Summarized financial information, in the aggregate, for our significant equity method investments on a 100 percent basis were as follows: Three Months Ended (In millions) 2018 2017 Revenues and other income $ 1,132 $ 1,027 Income from operations 73 82 Net income 71 81

Income per Common Share

Income per Common Share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Income per Common Share	Income per Common Share We compute basic earnings per share by dividing net income attributable to MPC by the weighted average number of shares of common stock outstanding. Diluted income per share assumes exercise of certain stock-based compensation awards, provided the effect is not anti-dilutive. MPC grants certain incentive compensation awards to employees and non-employee directors that are considered to be participating securities. Due to the presence of participating securities, we have calculated our earnings per share using the two-class method. Three Months Ended (In millions, except per share data) 2018 2017 Basic earnings per share: Allocation of earnings: Net income attributable to MPC $ 37 $ 30 Income allocated to participating securities — — Income available to common stockholders – basic $ 37 $ 30 Weighted average common shares outstanding 476 525 Basic earnings per share $ 0.08 $ 0.06 Diluted earnings per share: Allocation of earnings: Net income attributable to MPC $ 37 $ 30 Income allocated to participating securities — — Income available to common stockholders – diluted $ 37 $ 30 Weighted average common shares outstanding 476 525 Effect of dilutive securities 4 5 Weighted average common shares, including dilutive effect 480 530 Diluted earnings per share $ 0.08 $ 0.06 The following table summarizes the shares that were anti-dilutive and, therefore, were excluded from the diluted share calculation. Three Months Ended (In millions) 2018 2017 Shares issued under stock-based compensation plans — 2

Equity

Equity	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Equity	Equity As of March 31, 2018 , we had $1.86 billion of share repurchase authorization remaining under authorizations from our board of directors. 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: Three Months Ended (In millions, except per share data) 2018 2017 Number of shares repurchased 19 9 Cash paid for shares repurchased $ 1,327 $ 420 Average cost per share $ 68.74 $ 50.15 As of March 31, 2018 , we had agreements to acquire 619,415 common shares for $45 million , which were settled in early April 2018.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Segment Information	Segment Information 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 six refineries in the Gulf Coast and Midwest regions of the United States, purchases refined products and ethanol for resale and distributes refined products through transportation, storage, distribution and marketing services provided by our Midstream segment. We sell refined products to wholesale marketing customers domestically and internationally, to buyers on the spot market, to our Speedway business 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 – gathers, processes and transports natural gas; gathers, transports, fractionates, stores and markets NGLs; and transports, stores, distributes and markets crude oil and refined products principally for the Refining & Marketing segment via refining logistics assets, pipelines, terminals, towboats and barges. The Midstream segment primarily reflects the results of MPLX, our sponsored master limited partnership. As discussed in Note 4 , on February 1, 2018, we contributed certain refining logistics assets and fuels distribution services to MPLX. The results of these new businesses are reported in the Midstream segment prospectively from February 1, resulting in a net reduction of $181 million to Refining & Marketing segment results and a net increase to Midstream segment results of the same amount. No effect was given to prior periods as these entities were not considered businesses prior to February 1, 2018. Segment income represents income from operations attributable to the reportable segments. Corporate administrative expenses, except for those attributable to MPLX, 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, 2018 Revenues: Third party $ 13,412 $ 4,569 $ 713 $ 18,694 Intersegment 2,379 1 631 3,011 Related party 170 2 — 172 Segment revenues $ 15,961 $ 4,572 $ 1,344 $ 21,877 Segment income (loss) from operations $ (133 ) $ 95 $ 567 $ 529 Income from equity method investments 3 14 69 86 Depreciation and amortization (b) 252 79 181 512 Capital expenditures and investments (c) 191 39 482 712 (In millions) Refining & Marketing Speedway Midstream Total Three Months Ended March 31, 2017 Revenues: Third party $ 11,221 $ 4,381 $ 532 $ 16,134 Intersegment (a) 2,590 1 344 2,935 Related party 152 2 — 154 Segment revenues $ 13,963 $ 4,384 $ 876 $ 19,223 Segment income (loss) from operations $ (70 ) $ 135 $ 309 $ 374 Income from equity method investments 2 13 42 57 Depreciation and amortization (b) 267 64 191 522 Capital expenditures and investments (c)(d) 192 35 1,070 1,297 (a) Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties. (b) 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. (c) Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates. (d) The Midstream segment includes $220 million for the acquisition of the Ozark pipeline and an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system for the three months ended March 31, 2017 . 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) 2018 2017 Segment income from operations $ 529 $ 374 Items not allocated to segments: Corporate and other unallocated items (a) (88 ) (83 ) Pension settlement expenses (1 ) — Income from operations 440 291 Net interest and other financial costs 183 149 Income before income taxes $ 257 $ 142 (a) Corporate and other unallocated items consists primarily of MPC’s corporate administrative expenses and costs related to certain non-operating assets, except for corporate overhead expenses attributable to MPLX, which are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments. The following reconciles segment capital expenditures and investments to total capital expenditures: Three Months Ended (In millions) 2018 2017 Segment capital expenditures and investments $ 712 $ 1,297 Less investments in equity method investees (a) 41 566 Plus items not allocated to segments: Corporate 18 16 Capitalized interest 18 12 Total capital expenditures (b) $ 707 $ 759 (a) The three months ended March 31, 2017 includes an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system. (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. Revenues by product line were as follows: Three Months Ended (In millions) 2018 2017 Refined products $ 16,158 $ 13,876 Merchandise 1,130 1,192 Crude oil and refinery feedstocks 883 687 Service, transportation and other 523 379 Sales and other operating revenues $ 18,694 $ 16,134

Other Items

Other Items	3 Months Ended
	Mar. 31, 2018
Other Income and Expenses [Abstract]
Other Items	Other Items Net interest and other financial costs were as follows: Three Months Ended (In millions) 2018 2017 Interest income $ (20 ) $ (5 ) Interest expense 213 163 Interest capitalized (18 ) (15 ) Loss on extinguishment of debt 4 — Other financial costs 4 6 Net interest and other financial costs $ 183 $ 149

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The combined federal, state and foreign income tax rate was 9 percent and 29 percent for the three months ended March 31, 2018 and 2017 , respectively. The effective tax rate for the three months ended March 31, 2018 was less than the U.S. statutory rate of 21 percent primarily due to certain permanent tax differences related to net income attributable to noncontrolling interest, state and local deferred tax benefits primarily resulting from the February 1 dropdown and GP/IDR Exchange and equity compensation. The effective tax rate for the three months ended March 31, 2017 was less than the U.S. statutory rate of 35 percent primarily due to certain permanent tax differences related to equity compensation, net income attributable to noncontrolling interest and the domestic manufacturing deduction offset by state and local tax expense. We are continuously undergoing examination of our income tax returns, which have been completed through the 2007 tax year for state returns and the 2009 tax year for our U.S. federal return. As of March 31, 2018 , we had $19 million of unrecognized tax benefits. Prior to its spin-off on June 30, 2011, Marathon Petroleum Corporation was included in the Marathon Oil Corporation (“Marathon Oil”) federal income tax returns for all applicable years. During the third quarter 2017, Marathon Oil received a notice of Final Partnership Administrative Adjustment (“FPAA”) from the IRS for taxable year 2010, relating to certain pre-spinoff transactions. Marathon Oil filed a U.S. Tax Court petition disputing these adjustments during the fourth quarter of 2017. We received an FPAA for taxable years 2011-2014 for items resulting from this matter and filed a U.S. Tax Court petition for tax years 2011-2014 to dispute these corollary adjustments in the fourth quarter of 2017. We continue to believe that the issue in dispute is more likely than not to be fully sustained and therefore, no liability has been accrued for this matter. Pursuant to our tax sharing agreement with Marathon Oil, the unrecognized tax benefits related to pre-spinoff operations for which Marathon Oil was the taxpayer remain the responsibility of Marathon Oil and we have indemnified Marathon Oil accordingly. See Note 22 for indemnification information.

Inventories

Inventories	3 Months Ended
	Mar. 31, 2018
Inventory Disclosure [Abstract]
Inventories	Inventories (In millions) March 31, December 31, Crude oil and refinery feedstocks $ 1,777 $ 2,056 Refined products 2,746 2,839 Materials and supplies 435 494 Merchandise 153 161 Total $ 5,111 $ 5,550 Inventories are carried at the lower of cost or market value. The cost of inventories of crude oil and refinery feedstocks, refined products and merchandise is determined primarily under the LIFO method. There were no material liquidations of LIFO inventories for the three months ended March 31, 2018 .

Property, Plant and Equipment

Property, Plant and Equipment	3 Months Ended
	Mar. 31, 2018
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment (In millions) March 31, December 31, Refining & Marketing (a) $ 18,117 $ 19,490 Speedway 5,359 5,358 Midstream (a) 16,889 14,898 Corporate and Other 811 792 Total 41,176 40,538 Less accumulated depreciation 14,558 14,095 Property, plant and equipment, net $ 26,618 $ 26,443 (a) On February 1, 2018, we contributed certain refining logistics assets and fuels distribution services to MPLX. In connection with this transaction, approximately $830 million of net property, plant and equipment was recorded to the Midstream segment with an offsetting reduction to the Refining & Marketing segment .

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2018
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, 2018 and December 31, 2017 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, 2018 Fair Value Hierarchy (In millions) Level 1 Level 2 Level 3 Netting and Collateral (a) Net Carrying Value on Balance Sheet (b) Collateral Pledged Not Offset Commodity derivative instruments, assets $ 21 $ — $ — $ (21 ) $ — $ 22 Other assets 3 — — N/A 3 — Total assets at fair value $ 24 $ — $ — $ (21 ) $ 3 $ 22 Commodity derivative instruments, liabilities (c) $ 60 $ — $ 1 $ (60 ) $ 1 $ — Embedded derivatives in commodity contracts (c) — — 59 — 59 — Total liabilities at fair value $ 60 $ — $ 60 $ (60 ) $ 60 $ — December 31, 2017 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 $ 127 $ — $ — $ (118 ) $ 9 $ 8 Other assets 3 — — N/A 3 — Total assets at fair value $ 130 $ — $ — $ (118 ) $ 12 $ 8 Commodity derivative instruments, liabilities $ 126 $ — $ 2 $ (126 ) $ 2 $ — Embedded derivatives in commodity contracts (c) — — 64 — 64 — Total liabilities at fair value $ 126 $ — $ 66 $ (126 ) $ 66 $ — (a) Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of March 31, 2018 , cash collateral of $39 million was netted with the mark-to-market derivative liabilities. As of December 31, 2017 , $8 million was netted with mark-to-market derivative liabilities. (b) We have no derivative contracts that are subject to master netting arrangements reflected gross on the balance sheet. (c) Level 3 includes $11 million and $12 million classified as current at March 31, 2018 and December 31, 2017 , 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. Level 3 instruments are OTC NGL contracts and embedded derivatives in commodity contracts. The embedded derivative liability relates to a natural gas purchase agreement embedded in a keep‑whole processing agreement. 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 $0.26 to $1.47 per gallon and (2) the probability of renewal of 62.5 percent for the first five -year term and 82 percent for the second five -year term of the natural 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. 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 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) 2018 2017 Beginning balance $ 66 $ 190 Unrealized and realized losses included in net income (3 ) (12 ) Settlements of derivative instruments (3 ) (3 ) Ending balance $ 60 $ 175 The amount of total losses for the period included in earnings attributable to the change in unrealized losses relating to assets still held at the end of period: Derivative instruments $ (3 ) $ (13 ) Contingent consideration agreement — 1 Total $ (3 ) $ (12 ) Fair Values – Reported The following table summarizes financial instruments on the basis of their nature, characteristics and risk at March 31, 2018 and December 31, 2017 , excluding the derivative financial instruments and contingent consideration reported above. March 31, 2018 December 31, 2017 (In millions) Fair Value Carrying Value Fair Value Carrying Value Financial assets: Environmental receivables and misc. deposits 18 18 17 17 Total financial assets $ 18 $ 18 $ 17 $ 17 Financial liabilities: Long-term debt (a) $ 17,893 $ 17,010 $ 13,893 $ 12,642 Deferred credits and other liabilities 118 108 122 109 Total financial liabilities $ 18,011 $ 17,118 $ 14,015 $ 12,751 (a) Excludes capital leases and debt issuance costs; 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. Fair values of our 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. Deferred credits and other liabilities primarily consist of a liability resulting from a financing arrangement for the construction of MPLX’s steam methane reformer at the Javelina gas processing and fractionation complex in Corpus Christi, Texas, insurance liabilities and environmental remediation liabilities. Fair value of fixed-rate long-term debt is measured using Level 3 inputs. Fair value of variable-rate long-term debt approximates the carrying value.

Derivatives

Derivatives	3 Months Ended
	Mar. 31, 2018
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 and (6) the purchase of natural gas. 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, 2018 and December 31, 2017 : (In millions) March 31, 2018 Balance Sheet Location Asset Liability Commodity derivatives Other current assets $ 21 $ 60 Other current liabilities (a) — 12 Deferred credits and other liabilities (a) — 48 (In millions) December 31, 2017 Balance Sheet Location Asset Liability Commodity derivatives Other current assets $ 127 $ 126 Other current liabilities (a) — 14 Deferred credits and other liabilities (a) — 52 (a) Includes embedded derivatives. The tables below summarize open commodity derivative contracts for crude oil and refined products as of March 31, 2018 . Position Total Barrels (In thousands) Crude Oil (a) Exchange-traded Long 16,664 Exchange-traded Short (22,145 ) (a ) 94.7 percent of the exchange-traded contracts expire in the second quarter of 2018 . Position Total Gallons (In thousands) Refined Products (a) Exchange-traded Long 159,390 Exchange-traded Short (147,252 ) (a ) 100 percent of the exchange-traded contracts expire in the second quarter of 2018 . 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 2018 2017 Sales and other operating revenues $ (1 ) $ 16 Cost of revenues (27 ) (24 ) Total $ (28 ) $ (8 )

Debt

Debt	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Debt	Debt Our outstanding borrowings at March 31, 2018 and December 31, 2017 consisted of the following: (In millions) March 31, December 31, Marathon Petroleum Corporation: Commercial paper $ — $ — 364-day bank revolving credit facility due July 2018 — — Trade receivables securitization facility due July 2019 — — Bank revolving credit facility due 2022 — — Senior notes, 2.700% due December 2018 — 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 Capital lease obligations due 2018-2033 350 356 MPLX LP: MPLX 364-day term loan facility due 2018 — — MPLX term loan facility due 2019 — — MPLX bank revolving credit facility due 2022 — 505 MPLX senior notes, 5.500%, due February 2023 710 710 MPLX senior notes, 3.375%, due March 2023 500 — 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 MPLX senior notes, 4.125%, due March 2027 1,250 1,250 MPLX senior notes, 4.000%, due March 2028 1,250 — MPLX senior notes, 4.500%, due April 2038 1,750 — MPLX senior notes, 5.200%, due March 2047 1,000 1,000 MPLX senior notes, 4.700%, due April 2048 1,500 — MPLX senior notes, 4.900%, due April 2058 500 — MPLX capital lease obligations due 2020 7 7 Total 17,807 13,418 Unamortized debt issuance costs (109 ) (59 ) Unamortized discount (a) (440 ) (413 ) Amounts due within one year (26 ) (624 ) Total long-term debt due after one year $ 17,232 $ 12,322 (a) Includes $362 million and $374 million of unamortized discount as of March 31, 2018 and December 31, 2017 , respectively, related to the difference between the fair value and the principal amount of assumed MarkWest debt. Commercial Paper During the three months ended March 31, 2018 , we had no borrowings or repayments under the commercial paper program. At March 31, 2018 , we had no amounts outstanding under the commercial paper program. Trade Receivables Securitization Facility At March 31, 2018 , we had no amounts outstanding under our trade receivables securitization facility. MPC Bank Revolving Credit Facilities There were no borrowings or letters of credit outstanding under the MPC bank revolving credit facility at March 31, 2018 . MPC Senior Notes On March 15, 2018, we redeemed all of the $600 million outstanding aggregate principal amount of our 2.700 percent senior notes due December 2018. The 2018 senior notes were redeemed at a price equal to par plus a make whole premium, plus accrued and unpaid interest. The make whole premium of $2.5 million was calculated based on the market yield of the applicable treasury issue as of the redemption date as determined in accordance with the indenture governing the 2018 senior notes. MPLX Credit Agreement During the three months ended March 31, 2018 , MPLX borrowed $50 million under the MPLX bank revolving credit facility, at an average interest rate of 3.0 percent , and repaid $555 million . At March 31, 2018 , MPLX had no outstanding borrowings and $3 million letters of credit outstanding under the MPLX bank revolving credit facility, resulting in total availability of $2.25 billion . MPLX 364-Day Term Loan On January 2, 2018, MPLX entered into a term loan agreement with a syndicate of lenders providing for a $4.1 billion , 364 -day term loan facility. MPLX drew the entire amount of the term loan facility in a single borrowing to fund the cash portion of the consideration for the February 1, 2018 dropdown. On February 8, 2018, MPLX used $4.1 billion of the net proceeds from the issuance of MPLX senior notes to repay the 364 -day term-loan facility. MPLX Senior Notes On February 8, 2018, MPLX issued $5.5 billion in aggregate principal amount of senior notes in a public offering, consisting of $500 million aggregate principal amount of 3.375 percent unsecured senior notes due March 2023, $1.25 billion aggregate principal amount of 4.000 percent unsecured senior notes due March 2028, $1.75 billion aggregate principal amount of 4.500 percent unsecured senior notes due April 2038, $1.5 billion aggregate principal amount of 4.700 percent unsecured senior notes due April 2048, and $500 million aggregate principal amount of 4.900 percent unsecured senior notes due April 2058. MPLX used $4.1 billion of the net proceeds of the offering to repay the 364-day term-loan facility. The remaining proceeds were used to repay outstanding borrowings under MPLX’s revolving credit facility and intercompany loan agreement with us and for general partnership purposes.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	3 Months Ended
	Mar. 31, 2018
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information Three Months Ended (In millions) 2018 2017 Net cash provided by operating activities included: Interest paid (net of amounts capitalized) $ 212 $ 157 Net income taxes paid to taxing authorities 6 4 Non-cash investing and financing activities: Contribution of assets to joint venture (a) — 328 (a) MarkWest’s contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. See Note 5 . (In millions) March 31, December 31, Cash and cash equivalents $ 4,653 $ 3,011 Restricted cash (a) 4 4 Cash, cash equivalents and restricted cash (b) $ 4,657 $ 3,015 (a) The restricted cash balance is included within “Other current assets” on the consolidated balance sheets. (b) As a result of the adoption of ASU 2016-18, the consolidated statements of cash flows now explain the change during the period of both “Cash and cash equivalents” and “Restricted cash.” 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) 2018 2017 Additions to property, plant and equipment per consolidated statements of cash flows $ 755 $ 610 Asset retirement expenditures 1 1 Decrease in capital accruals (49 ) (72 ) Total capital expenditures before acquisitions 707 539 Acquisitions (a) — 220 Total capital expenditures $ 707 $ 759 (a) The three months ended March 31, 2017 reflects the acquisition of the Ozark pipeline.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	3 Months Ended
	Mar. 31, 2018
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, 2016 $ (233 ) $ (7 ) $ 4 $ 2 $ (234 ) Other comprehensive loss before reclassifications (1 ) — — — (1 ) Amounts reclassified from accumulated other comprehensive loss: Amortization – prior service credit (a) (10 ) (1 ) — — (11 ) – actuarial loss (a) 9 — — — 9 – settlement loss (a) — — — — — Tax effect — — — — — Other comprehensive loss (2 ) (1 ) — — (3 ) Balance as of March 31, 2017 $ (235 ) $ (8 ) $ 4 $ 2 $ (237 ) (In millions) Pension Benefits Other Benefits Gain on Cash Flow Hedge Workers Compensation Total Balance as of December 31, 2017 $ (190 ) $ (48 ) $ 4 $ 3 $ (231 ) Other comprehensive loss before reclassifications — — (2 ) — (2 ) Amounts reclassified from accumulated other comprehensive loss: Amortization – prior service credit (a) (8 ) (1 ) — — (9 ) – actuarial loss (a) 9 — — — 9 – settlement loss (a) 1 — — — 1 Tax effect (1 ) — — — (1 ) Other comprehensive income (loss) 1 (1 ) (2 ) — (2 ) Balance as of March 31, 2018 $ (189 ) $ (49 ) $ 2 $ 3 $ (233 ) (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, 2018
Retirement Benefits [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) 2018 2017 2018 2017 Components of net periodic benefit cost: Service cost $ 36 $ 31 $ 7 $ 7 Interest cost 18 19 7 8 Expected return on plan assets (26 ) (26 ) — — Amortization – prior service credit (8 ) (10 ) (1 ) (1 ) – actuarial loss 9 9 — — – settlement loss 1 — — — Net periodic benefit cost $ 30 $ 23 $ 13 $ 14 The components of net periodic benefit cost other than the service cost component are included in the line item “Net interest and other financial costs” in the income statement. During the three months ended March 31, 2018 , we made no contributions to our funded pension plans. Benefit payments related to unfunded pension and other postretirement benefit plans were $6 million and $8 million , respectively, during the three months ended March 31, 2018 .

Stock-Based Compensation Plans

Stock-Based Compensation Plans	3 Months Ended
	Mar. 31, 2018
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, 2018 : Number of Shares Weighted Average Exercise Price Outstanding at December 31, 2017 8,465,398 $ 33.74 Granted 529,197 64.79 Exercised (477,086 ) 24.68 Forfeited or expired (4,512 ) 49.94 Outstanding at March 31, 2018 8,512,997 36.17 The grant date fair value of stock option awards granted during the three months ended March 31, 2018 was $17.37 per share. The fair value of stock options granted to our employees is estimated on the date of the grant using the Black Scholes option-pricing model, which employs various assumptions. Restricted Stock Awards The following table presents a summary of restricted stock award activity for the three months ended March 31, 2018 : 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, 2017 1,188,662 $ 45.07 285,164 $ 29.95 Granted 94,592 64.79 6,924 67.75 RS’s Vested/RSU’s Issued (123,918 ) 45.06 — — Forfeited (24,639 ) 44.62 — — Outstanding at March 31, 2018 1,134,697 46.72 292,088 30.85 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, 2018 : Number of Units Weighted Average Grant Date Fair Value Outstanding at December 31, 2017 6,851,542 $ 0.81 Granted 3,830,000 0.83 Vested (2,052,959 ) 0.95 Forfeited (10,000 ) 0.92 Outstanding at March 31, 2018 8,618,583 0.79 The performance unit awards granted during the three months ended March 31, 2018 have a grant date fair value of $0.83 per unit, as calculated using a Monte Carlo valuation model. MPLX Awards During the three months ended March 31, 2018 , 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, 2018
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 a liability, we are unable to estimate a range of possible loss because the issues involved have not been fully developed through pleadings, discovery or court proceedings. 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, 2018 and December 31, 2017 , accrued liabilities for remediation totaled $112 million and $114 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 $45 million at both March 31, 2018 and December 31, 2017 . 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. MarkWest Environmental Proceeding - MarkWest Liberty Midstream & Resources, L.L.C., a wholly owned subsidiary of MPLX (“MarkWest Liberty Midstream”) and its affiliates agreed in principle to pay a cash penalty of approximately $0.6 million and to undertake certain supplemental environmental projects with an estimated cost of approximately $2.4 million , related to civil enforcement allegations associated with permitting and other regulatory obligations for launcher/receiver and compressor station facilities in southeastern Ohio and western Pennsylvania. On April 24, 2018, MarkWest Liberty Midstream and its affiliates entered into a Consent Decree with the EPA and the Pennsylvania Department of Environmental Protection (“PADEP”) resolving these issues, subject to a 30-day public comment period, pursuant to which MarkWest Liberty Midstream will pay a penalty of $0.6 million and undertake certain supplemental environmental projects with an estimated cost of approximately $2.4 million , in addition to other related projects that are substantially complete. Other Lawsuits - MPLX, MarkWest, MarkWest Liberty Midstream, MarkWest Liberty Bluestone, L.L.C., Ohio Fractionation and MarkWest Utica EMG (collectively, the “MPLX Parties”) are parties to various lawsuits with Bilfinger Westcon, Inc. (“Westcon”) that were instituted in 2016 and 2017 in the Court of Common Pleas in Butler County, Pennsylvania, the Circuit Court in Wetzel County, West Virginia, and the Court of Common Pleas in Harrison County, Ohio. The lawsuits relate to disputes regarding construction work performed by Westcon at the Bluestone, Mobley and Cadiz processing complexes in Pennsylvania, West Virginia and Ohio, respectively, and the Hopedale fractionation complex in Ohio. With respect to work performed by Westcon at the Mobley and Bluestone processing complexes, one or more of the MPLX Parties have asserted breach of contract, fraud, and with respect to work performed at the Mobley processing complex, MarkWest Liberty Midstream has also asserted negligent misrepresentation claims against Westcon. Westcon has also asserted claims against one or more of the MPLX Parties regarding these construction projects for breach of contract, unjust enrichment, promissory estoppel, fraud and constructive fraud, tortious interference with contractual relations, and civil conspiracy. Collectively, in the several cases, the MPLX Parties seek in excess of $10 million , plus an unspecified amount of punitive damages. Collectively, in the several cases, Westcon seeks in excess of $40 million , plus an unspecified amount of punitive damages. While the ultimate outcome and impact cannot be predicted with certainty, and management is not able to estimate a reasonably possible loss (or range of loss), if any, for these matters, we believe the resolution of these claims will not have a material adverse effect on our consolidated financial position, results of operations, or cash flows. In May 2015, the Kentucky attorney general filed a lawsuit against our wholly-owned subsidiary, 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 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 on our consolidated financial position, results of operations, or cash flows. 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 —MPC and MPLX hold interests in an offshore oil port, LOOP, and MPLX holds an interest in a crude oil pipeline system, LOCAP. Both LOOP and LOCAP have secured various project financings with throughput and deficiency agreements. Under the agreements, MPC, as a shipper, is 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 $160 million as of March 31, 2018 . 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 $24 million as of March 31, 2018 . In connection with our 50 percent indirect interest 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, 2018 , our maximum potential undiscounted payments under this agreement for debt principal totaled $163 million . In connection with our 50 percent indirect interest in Crowley Blue Water Partners, we have agreed to provide a conditional guarantee of up to 50 percent of its outstanding debt balance in the event there is no charter agreement in place with an investment grade customer for the entity’s three vessels as well as other financial support in certain circumstances. The maximum exposure under these arrangements is 50 percent of the amount of the debt, which was $132 million as of March 31, 2018 . Marathon Oil indemnifications— In conjunction with our spinoff from Marathon Oil, we have entered into arrangements with Marathon Oil providing indemnities and guarantees with recorded values of $2 million as of March 31, 2018 , 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 12 , 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 $93 million as of March 31, 2018 , 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, a commitment to fund a share of the bonds issued by a government entity for construction of public utilities in the event that other industrial users of the facility default on their utility payments 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, 2018 , our contractual commitments to acquire property, plant and equipment and advance funds to equity method investees totaled $879 million . Certain natural gas processing and gathering arrangements require us to construct 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 producer customers may have the right to cancel the processing arrangements with us if there are significant delays that are not due to force majeure.

Supplementary Statistics

Supplementary Statistics	3 Months Ended
	Mar. 31, 2018
Text Block [Abstract]
Supplementary Statistics	Supplementary Statistics (Unaudited) Three Months Ended (In millions) 2018 2017 Income (Loss) from Operations by Segment Refining & Marketing (a) $ (133 ) $ (70 ) Speedway 95 135 Midstream (a) 567 309 Items not allocated to segments: Corporate and other unallocated items (88 ) (83 ) Pension settlement expenses (1 ) — Income from operations $ 440 $ 291 Capital Expenditures and Investments (b) Refining & Marketing $ 191 $ 192 Speedway 39 35 Midstream (c) 482 1,070 Corporate and Other (d) 36 28 Total $ 748 $ 1,325 (a) On February 1, 2018, we contributed certain refining logistics assets and fuels distributions services to MPLX. The results of these new businesses are reported in the Midstream segment prospectively from February 1, resulting in a net reduction of $181 million to Refining & Marketing segment results and a net increase to Midstream segment results of the same amount. No effect was given to prior periods as these entities were not considered businesses prior to February 1, 2018. (b) Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates. (c) The three months ended March 31, 2017 includes $220 million for the acquisition of the Ozark pipeline and an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system. (d) Includes capitalized interest of $18 million and $12 million for the three months ended March 31, 2018 and 2017 , respectively. Supplementary Statistics (Unaudited) Three Months Ended 2018 2017 MPC Consolidated Refined Product Sales Volumes (mbpd) (a) 2,275 2,085 Refining & Marketing Operating Statistics Refining & Marketing refined product sales volume (mbpd) (b) 2,261 2,070 Refining & Marketing margin (dollars per barrel) (c) $ 10.58 $ 11.65 Crude oil capacity utilization percent (d) 93 83 Refinery throughputs (mbpd): (e) Crude oil refined 1,745 1,511 Other charge and blendstocks 160 197 Total 1,905 1,708 Sour crude oil throughput percent 52 67 WTI-priced crude oil throughput percent 26 15 Refined product yields (mbpd): (e) Gasoline 917 867 Distillates 609 544 Propane 31 28 Feedstocks and special products 287 224 Heavy fuel oil 34 29 Asphalt 58 56 Total 1,936 1,748 Refinery direct operating costs (dollars per barrel): (f) Planned turnaround and major maintenance $ 2.22 $ 3.10 Depreciation and amortization 1.37 1.63 Other manufacturing (g) 4.09 4.72 Total $ 7.68 $ 9.45 Refining & Marketing Operating Statistics By Region - Gulf Coast Refinery throughputs (mbpd): (h) Crude oil refined 1,056 850 Other charge and blendstocks 167 222 Total 1,223 1,072 Sour crude oil throughput percent 60 84 WTI-priced crude oil throughput percent 13 4 Refined product yields (mbpd): (h) Gasoline 534 499 Distillates 360 309 Propane 19 21 Feedstocks and special products 298 243 Heavy fuel oil 23 18 Asphalt 17 14 Total 1,251 1,104 Refinery direct operating costs (dollars per barrel): (f) Planned turnaround and major maintenance $ 2.87 $ 4.31 Depreciation and amortization 1.09 1.35 Other manufacturing (g) 3.91 4.62 Total $ 7.87 $ 10.28 Supplementary Statistics (Unaudited) Three Months Ended 2018 2017 Refining & Marketing Operating Statistics By Region – Midwest Refinery throughputs (mbpd): (h) Crude oil refined 689 661 Other charge and blendstocks 35 30 Total 724 691 Sour crude oil throughput percent 38 45 WTI-priced crude oil throughput percent 47 29 Refined product yields (mbpd): (h) Gasoline 383 368 Distillates 249 235 Propane 12 8 Feedstocks and special products 31 35 Heavy fuel oil 11 11 Asphalt 41 42 Total 727 699 Refinery direct operating costs (dollars per barrel): (f) Planned turnaround and major maintenance $ 0.99 $ 0.98 Depreciation and amortization 1.77 1.93 Other manufacturing (g) 4.16 4.50 Total $ 6.92 $ 7.41 Speedway Operating Statistics Convenience stores at period-end 2,742 2,731 Gasoline and distillate sales (millions of gallons) 1,393 1,393 Gasoline and distillate margin (dollars per gallon) (i) $ 0.1561 $ 0.1566 Merchandise sales (in millions) $ 1,129 $ 1,127 Merchandise margin (in millions) $ 319 $ 320 Merchandise margin percent 28.3 % 28.4 % Same store gasoline sales volume (period over period) (1.5 %) (1.0 %) Same store merchandise sales (period over period) (j) 2.3 % 2.1 % Midstream Operating Statistics Crude oil and refined product pipeline throughputs (mbpd) (k) 3,459 2,888 Terminal throughput (mbpd) 1,445 1,424 Gathering system throughput (MMcf/d) (l) 4,171 3,184 Natural gas processed (MMcf/d) (l) 6,629 6,132 C2 (ethane) + NGLs (natural gas liquids) fractionated (mbpd) (l) 423 367 (a) Total average daily volumes of refined product sales to wholesale, branded and retail customers. (b) Includes intersegment sales. (c) Sales revenue less cost of refinery inputs and purchased products, divided by total refinery throughputs. (d) Based on calendar-day capacity, which is an annual average that includes down time for planned maintenance and other normal operating activities. (e) Excludes inter-refinery volumes of 42 mbpd and 55 mbpd for the three months ended March 31, 2018 and 2017 , respectively. (f) Per barrel of total refinery throughputs. Effective with the February 1, 2018 dropdown, direct operating costs related to certain refining logistics assets are now reported in the Midstream segment. No effect was given to prior periods as this entity was not considered a business prior to February 1, 2018. (g) Includes utilities, labor, routine maintenance and other operating costs. (h) Includes inter-refinery transfer volumes. (i) The price paid by consumers less the cost of refined products, including transportation, consumer excise taxes and bank card processing fees, divided by gasoline and distillate sales volume. (j) Excludes cigarettes. (k) Includes common-carrier pipelines and private pipelines owned or operated by MPLX, excluding equity method investments. (l) Includes amounts related to unconsolidated equity method investments on a 100 percent basis.

Subsequent Event

Subsequent Event	3 Months Ended
	Mar. 31, 2018
Subsequent Events [Abstract]
Subsequent Events [Text Block]	Subsequent Event On April 29, 2018, MPC and Andeavor (“ANDV”) entered into a definitive merger agreement under which MPC will acquire all of ANDV’s outstanding shares, representing a total equity value of $23.3 billion and a total enterprise value of $35.6 billion based on MPC’s April 27, 2018, closing price of $81.43 . Under the terms of the agreement, ANDV shareholders will have the option to choose 1.87 shares of MPC stock or $152.27 in cash subject to a proration mechanism that achieves an aggregate consideration mix of 85 percent equity and 15 percent cash. MPC and ANDV shareholders will own approximately 66 percent and 34 percent of the combined company, respectively. The transaction was unanimously approved by the boards of directors of both companies and is expected to close in the second half of 2018, subject to regulatory and other customary closing conditions, including approvals from both MPC and ANDV shareholders.

Summary of Principal Accountin

Summary of Principal Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
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 GAAP for complete financial statements.
Revenue recognition	Revenue Recognition - As described in Note 3 , we adopted ASU 2014-09, Revenue from Contracts with Customers (ASC 606) effective January 1, 2018. We recognize revenue based on consideration specified in contracts or agreements with customers when we satisfy our performance obligations by transferring control over products or services to a customer. Concurrent with our adoption of ASC 606, we made an accounting policy election that all taxes assessed by a governmental authority that are both imposed on and concurrent with a revenue-producing transaction and collected from our customers will be recognized on a net basis within “Sales and other operating revenues”. The adoption of ASC 606 did not materially change our revenue recognition patterns, which are described below by reportable segment: • Refining & Marketing - The vast majority of our Refining & Marketing contracts contain pricing that is based on the market price for the product at the time of delivery. Our obligations to deliver product volumes are typically satisfied and revenue is recognized when control of the product transfers to our customers. Concurrent with the transfer of control, we typically receive the right to payment for the delivered product, the customer accepts the product and the customer has significant risks and rewards of ownership of the product. Payment terms require customers to pay shortly after delivery and do not contain significant financing components. • Speedway - Revenue is recognized when our customers receive control of the transportation fuels or merchandise. Payments from customers are received at the time sales occur in cash or by credit or debit card. Speedway offers a loyalty rewards program to its customers. We defer a minor portion of revenue on sales to the loyalty program participants until the participants redeem their rewards. The related contract liability, as defined in the standard, is not material to our financial statements. • Midstream - Midstream revenue transactions typically are defined by contracts under which we sell a product or provide a service. Revenues from sales of product are recognized when control of the product transfers to the customer. Revenues from sales of services are recognized over time when the performance obligation is satisfied as services are provided in a series. We have elected to use the output measure of progress to recognize revenue based on the units delivered, processed or transported. The transaction price in our Midstream contracts often has both fixed components, related to minimum volume commitments, and variable components which are primarily dependent on volumes. Variable consideration will generally not be estimated at contract inception as the transaction price is specifically allocable to the services provided each period end. Refer to Note 10 for disclosure of our revenue disaggregated by segment and product line, as well as a description of our reportable segment operations.
Inventories	Inventories are carried at the lower of cost or market value. The cost of inventories of crude oil and refinery feedstocks, refined products and merchandise is determined primarily under the 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 and (6) the purchase of natural gas.
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.

MPLX LP (Tables)

MPLX LP (Tables)	3 Months Ended
	Mar. 31, 2018
Noncontrolling Interest [Abstract]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net	As a result of equity transactions of MPLX, we are required to adjust non-controlling interest and additional paid-in capital. Changes in MPC’s additional paid-in capital resulting from changes in its ownership interests in MPLX were as follows: Three Months Ended (In millions) 2018 2017 Increase due to the issuance of MPLX LP common units to the public $ 4 $ 10 Increase due to the issuance of MPLX LP common units and general partner units to MPC 1,114 96 Increase due to GP/IDR Exchange 1,808 — Increase in MPC's additional paid-in capital 2,926 106 Tax impact (546 ) (34 ) Increase in MPC's additional paid-in capital, net of tax $ 2,380 $ 72

Related Party Transactions (Tab

Related Party Transactions (Tables)	3 Months Ended
	Mar. 31, 2018
Related Party Transactions [Abstract]
Sales to Related Parties	Sales to related parties were as follows: Three Months Ended (In millions) 2018 2017 PFJ Southeast $ 169 $ 151 Other equity method investees 3 3 Total $ 172 $ 154
Other Income From Related Parties	Other income from related parties, which is included in “Other income” on the accompanying consolidated statements of income, were as follows: Three Months Ended (In millions) 2018 2017 MarkWest Utica EMG $ 4 $ 4 Ohio Gathering 4 4 Sherwood Midstream 3 1 Other equity method investees 2 2 Total $ 13 $ 11
Purchases From Related Parties	Purchases from related parties were as follows: Three Months Ended (In millions) 2018 2017 Crowley Blue Water Partners $ 16 $ 14 Crowley Ocean Partners 20 19 Illinois Extension Pipeline 24 25 LOCAP 4 5 LOOP 17 13 TAAE 19 8 TACE 8 16 TAME 20 17 Other equity method investees 13 5 Total $ 141 $ 122
Receivables From Related Parties	Receivables from related parties, which are included in “Receivables, less allowance for doubtful accounts” on the accompanying consolidated balance sheets, were as follows: (In millions) March 31, December 31, PFJ Southeast $ 30 $ 28 Sherwood Midstream Holdings 15 — Other equity method investees 7 8 Total $ 52 $ 36
Payables To Related Parties	Payables to related parties, which are included in “Accounts payable” on the accompanying consolidated balance sheets, were as follows: (In millions) March 31, December 31, Illinois Extension Pipeline $ 7 $ 8 LOOP 2 3 MarkWest Utica EMG 20 29 Ohio Gathering 1 9 Sherwood Midstream 11 8 Other equity method investees 10 12 Total $ 51 $ 69
Summarized Financial Information For Equity Method Investees Table	Summarized financial information, in the aggregate, for our significant equity method investments on a 100 percent basis were as follows: Three Months Ended (In millions) 2018 2017 Revenues and other income $ 1,132 $ 1,027 Income from operations 73 82 Net income 71 81

Income per Common Share (Tables

Income per Common Share (Tables)	3 Months Ended
	Mar. 31, 2018
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) 2018 2017 Basic earnings per share: Allocation of earnings: Net income attributable to MPC $ 37 $ 30 Income allocated to participating securities — — Income available to common stockholders – basic $ 37 $ 30 Weighted average common shares outstanding 476 525 Basic earnings per share $ 0.08 $ 0.06 Diluted earnings per share: Allocation of earnings: Net income attributable to MPC $ 37 $ 30 Income allocated to participating securities — — Income available to common stockholders – diluted $ 37 $ 30 Weighted average common shares outstanding 476 525 Effect of dilutive securities 4 5 Weighted average common shares, including dilutive effect 480 530 Diluted earnings per share $ 0.08 $ 0.06
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following table summarizes the shares that were anti-dilutive and, therefore, were excluded from the diluted share calculation. Three Months Ended (In millions) 2018 2017 Shares issued under stock-based compensation plans — 2

Equity (Tables)

Equity (Tables)	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Share Repurchases	Total share repurchases were as follows: Three Months Ended (In millions, except per share data) 2018 2017 Number of shares repurchased 19 9 Cash paid for shares repurchased $ 1,327 $ 420 Average cost per share $ 68.74 $ 50.15

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Income From Operations Attributable To Operating Segments	Segment income represents income from operations attributable to the reportable segments. Corporate administrative expenses, except for those attributable to MPLX, 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, 2018 Revenues: Third party $ 13,412 $ 4,569 $ 713 $ 18,694 Intersegment 2,379 1 631 3,011 Related party 170 2 — 172 Segment revenues $ 15,961 $ 4,572 $ 1,344 $ 21,877 Segment income (loss) from operations $ (133 ) $ 95 $ 567 $ 529 Income from equity method investments 3 14 69 86 Depreciation and amortization (b) 252 79 181 512 Capital expenditures and investments (c) 191 39 482 712 (In millions) Refining & Marketing Speedway Midstream Total Three Months Ended March 31, 2017 Revenues: Third party $ 11,221 $ 4,381 $ 532 $ 16,134 Intersegment (a) 2,590 1 344 2,935 Related party 152 2 — 154 Segment revenues $ 13,963 $ 4,384 $ 876 $ 19,223 Segment income (loss) from operations $ (70 ) $ 135 $ 309 $ 374 Income from equity method investments 2 13 42 57 Depreciation and amortization (b) 267 64 191 522 Capital expenditures and investments (c)(d) 192 35 1,070 1,297 (a) Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties. (b) 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. (c) Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates. (d) The Midstream segment includes $220 million for the acquisition of the Ozark pipeline and an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system for the three months ended March 31, 2017 .
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) 2018 2017 Segment income from operations $ 529 $ 374 Items not allocated to segments: Corporate and other unallocated items (a) (88 ) (83 ) Pension settlement expenses (1 ) — Income from operations 440 291 Net interest and other financial costs 183 149 Income before income taxes $ 257 $ 142 (a) Corporate and other unallocated items consists primarily of MPC’s corporate administrative expenses and costs related to certain non-operating assets, except for corporate overhead expenses attributable to MPLX, which are included in the Midstream segment.
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) 2018 2017 Segment capital expenditures and investments $ 712 $ 1,297 Less investments in equity method investees (a) 41 566 Plus items not allocated to segments: Corporate 18 16 Capitalized interest 18 12 Total capital expenditures (b) $ 707 $ 759 (a) The three months ended March 31, 2017 includes an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system. (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.
Revenue from External Customers by Products and Services	Revenues by product line were as follows: Three Months Ended (In millions) 2018 2017 Refined products $ 16,158 $ 13,876 Merchandise 1,130 1,192 Crude oil and refinery feedstocks 883 687 Service, transportation and other 523 379 Sales and other operating revenues $ 18,694 $ 16,134

Other Items (Tables)

Other Items (Tables)	3 Months Ended
	Mar. 31, 2018
Other Income and Expenses [Abstract]
Net Interest And Other Financial Income (Costs)	Net interest and other financial costs were as follows: Three Months Ended (In millions) 2018 2017 Interest income $ (20 ) $ (5 ) Interest expense 213 163 Interest capitalized (18 ) (15 ) Loss on extinguishment of debt 4 — Other financial costs 4 6 Net interest and other financial costs $ 183 $ 149

Inventories (Tables)

Inventories (Tables)	3 Months Ended
	Mar. 31, 2018
Inventory Disclosure [Abstract]
Summary Of Inventories	(In millions) March 31, December 31, Crude oil and refinery feedstocks $ 1,777 $ 2,056 Refined products 2,746 2,839 Materials and supplies 435 494 Merchandise 153 161 Total $ 5,111 $ 5,550

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	3 Months Ended
	Mar. 31, 2018
Property, Plant and Equipment [Abstract]
Summary Of Property, Plant And Equipment	(In millions) March 31, December 31, Refining & Marketing (a) $ 18,117 $ 19,490 Speedway 5,359 5,358 Midstream (a) 16,889 14,898 Corporate and Other 811 792 Total 41,176 40,538 Less accumulated depreciation 14,558 14,095 Property, plant and equipment, net $ 26,618 $ 26,443 (a) On February 1, 2018, we contributed certain refining logistics assets and fuels distribution services to MPLX. In connection with this transaction, approximately $830 million of net property, plant and equipment was recorded to the Midstream segment with an offsetting reduction to the Refining & Marketing segment .

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2018
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, 2018 and December 31, 2017 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, 2018 Fair Value Hierarchy (In millions) Level 1 Level 2 Level 3 Netting and Collateral (a) Net Carrying Value on Balance Sheet (b) Collateral Pledged Not Offset Commodity derivative instruments, assets $ 21 $ — $ — $ (21 ) $ — $ 22 Other assets 3 — — N/A 3 — Total assets at fair value $ 24 $ — $ — $ (21 ) $ 3 $ 22 Commodity derivative instruments, liabilities (c) $ 60 $ — $ 1 $ (60 ) $ 1 $ — Embedded derivatives in commodity contracts (c) — — 59 — 59 — Total liabilities at fair value $ 60 $ — $ 60 $ (60 ) $ 60 $ — December 31, 2017 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 $ 127 $ — $ — $ (118 ) $ 9 $ 8 Other assets 3 — — N/A 3 — Total assets at fair value $ 130 $ — $ — $ (118 ) $ 12 $ 8 Commodity derivative instruments, liabilities $ 126 $ — $ 2 $ (126 ) $ 2 $ — Embedded derivatives in commodity contracts (c) — — 64 — 64 — Total liabilities at fair value $ 126 $ — $ 66 $ (126 ) $ 66 $ — (a) Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of March 31, 2018 , cash collateral of $39 million was netted with the mark-to-market derivative liabilities. As of December 31, 2017 , $8 million was netted with mark-to-market derivative liabilities. (b) We have no derivative contracts that are subject to master netting arrangements reflected gross on the balance sheet. (c) Level 3 includes $11 million and $12 million classified as current at March 31, 2018 and December 31, 2017 , 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) 2018 2017 Beginning balance $ 66 $ 190 Unrealized and realized losses included in net income (3 ) (12 ) Settlements of derivative instruments (3 ) (3 ) Ending balance $ 60 $ 175 The amount of total losses for the period included in earnings attributable to the change in unrealized losses relating to assets still held at the end of period: Derivative instruments $ (3 ) $ (13 ) Contingent consideration agreement — 1 Total $ (3 ) $ (12 )
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, 2018 and December 31, 2017 , excluding the derivative financial instruments and contingent consideration reported above. March 31, 2018 December 31, 2017 (In millions) Fair Value Carrying Value Fair Value Carrying Value Financial assets: Environmental receivables and misc. deposits 18 18 17 17 Total financial assets $ 18 $ 18 $ 17 $ 17 Financial liabilities: Long-term debt (a) $ 17,893 $ 17,010 $ 13,893 $ 12,642 Deferred credits and other liabilities 118 108 122 109 Total financial liabilities $ 18,011 $ 17,118 $ 14,015 $ 12,751 (a) Excludes capital leases and debt issuance costs; includes amount classified as debt due within one year.

Derivatives (Tables)

Derivatives (Tables)	3 Months Ended
	Mar. 31, 2018
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, 2018 and December 31, 2017 : (In millions) March 31, 2018 Balance Sheet Location Asset Liability Commodity derivatives Other current assets $ 21 $ 60 Other current liabilities (a) — 12 Deferred credits and other liabilities (a) — 48 (In millions) December 31, 2017 Balance Sheet Location Asset Liability Commodity derivatives Other current assets $ 127 $ 126 Other current liabilities (a) — 14 Deferred credits and other liabilities (a) — 52 (a) Includes embedded derivatives.
Open Commodity Derivative Contracts	The tables below summarize open commodity derivative contracts for crude oil and refined products as of March 31, 2018 . Position Total Barrels (In thousands) Crude Oil (a) Exchange-traded Long 16,664 Exchange-traded Short (22,145 ) (a ) 94.7 percent of the exchange-traded contracts expire in the second quarter of 2018 . Position Total Gallons (In thousands) Refined Products (a) Exchange-traded Long 159,390 Exchange-traded Short (147,252 ) (a ) 100 percent of the exchange-traded contracts expire in the second quarter of 2018 .
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 2018 2017 Sales and other operating revenues $ (1 ) $ 16 Cost of revenues (27 ) (24 ) Total $ (28 ) $ (8 )

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Outstanding Borrowings	Our outstanding borrowings at March 31, 2018 and December 31, 2017 consisted of the following: (In millions) March 31, December 31, Marathon Petroleum Corporation: Commercial paper $ — $ — 364-day bank revolving credit facility due July 2018 — — Trade receivables securitization facility due July 2019 — — Bank revolving credit facility due 2022 — — Senior notes, 2.700% due December 2018 — 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 Capital lease obligations due 2018-2033 350 356 MPLX LP: MPLX 364-day term loan facility due 2018 — — MPLX term loan facility due 2019 — — MPLX bank revolving credit facility due 2022 — 505 MPLX senior notes, 5.500%, due February 2023 710 710 MPLX senior notes, 3.375%, due March 2023 500 — 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 MPLX senior notes, 4.125%, due March 2027 1,250 1,250 MPLX senior notes, 4.000%, due March 2028 1,250 — MPLX senior notes, 4.500%, due April 2038 1,750 — MPLX senior notes, 5.200%, due March 2047 1,000 1,000 MPLX senior notes, 4.700%, due April 2048 1,500 — MPLX senior notes, 4.900%, due April 2058 500 — MPLX capital lease obligations due 2020 7 7 Total 17,807 13,418 Unamortized debt issuance costs (109 ) (59 ) Unamortized discount (a) (440 ) (413 ) Amounts due within one year (26 ) (624 ) Total long-term debt due after one year $ 17,232 $ 12,322 (a) Includes $362 million and $374 million of unamortized discount as of March 31, 2018 and December 31, 2017 , respectively, related to the difference between the fair value and the principal amount of assumed MarkWest debt.

Supplemental Cash Flow Inform48

Supplemental Cash Flow Information (Tables)	3 Months Ended
	Mar. 31, 2018
Supplemental Cash Flow Elements [Abstract]
Summary of Supplemental Cash Flow Information	Three Months Ended (In millions) 2018 2017 Net cash provided by operating activities included: Interest paid (net of amounts capitalized) $ 212 $ 157 Net income taxes paid to taxing authorities 6 4 Non-cash investing and financing activities: Contribution of assets to joint venture (a) — 328 (a) MarkWest’s contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. See Note 5 .
Schedule of Cash and Cash Equivalents	(In millions) March 31, December 31, Cash and cash equivalents $ 4,653 $ 3,011 Restricted cash (a) 4 4 Cash, cash equivalents and restricted cash (b) $ 4,657 $ 3,015 (a) The restricted cash balance is included within “Other current assets” on the consolidated balance sheets. (b) As a result of the adoption of ASU 2016-18, the consolidated statements of cash flows now explain the change during the period of both “Cash and cash equivalents” and “Restricted cash.”
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) 2018 2017 Additions to property, plant and equipment per consolidated statements of cash flows $ 755 $ 610 Asset retirement expenditures 1 1 Decrease in capital accruals (49 ) (72 ) Total capital expenditures before acquisitions 707 539 Acquisitions (a) — 220 Total capital expenditures $ 707 $ 759 (a) The three months ended March 31, 2017 reflects the acquisition of the Ozark pipeline.

Accumulated Other Comprehensi49

Accumulated Other Comprehensive Loss (Tables)	3 Months Ended
	Mar. 31, 2018
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, 2016 $ (233 ) $ (7 ) $ 4 $ 2 $ (234 ) Other comprehensive loss before reclassifications (1 ) — — — (1 ) Amounts reclassified from accumulated other comprehensive loss: Amortization – prior service credit (a) (10 ) (1 ) — — (11 ) – actuarial loss (a) 9 — — — 9 – settlement loss (a) — — — — — Tax effect — — — — — Other comprehensive loss (2 ) (1 ) — — (3 ) Balance as of March 31, 2017 $ (235 ) $ (8 ) $ 4 $ 2 $ (237 ) (In millions) Pension Benefits Other Benefits Gain on Cash Flow Hedge Workers Compensation Total Balance as of December 31, 2017 $ (190 ) $ (48 ) $ 4 $ 3 $ (231 ) Other comprehensive loss before reclassifications — — (2 ) — (2 ) Amounts reclassified from accumulated other comprehensive loss: Amortization – prior service credit (a) (8 ) (1 ) — — (9 ) – actuarial loss (a) 9 — — — 9 – settlement loss (a) 1 — — — 1 Tax effect (1 ) — — — (1 ) Other comprehensive income (loss) 1 (1 ) (2 ) — (2 ) Balance as of March 31, 2018 $ (189 ) $ (49 ) $ 2 $ 3 $ (233 ) (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, 2018
Retirement Benefits [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) 2018 2017 2018 2017 Components of net periodic benefit cost: Service cost $ 36 $ 31 $ 7 $ 7 Interest cost 18 19 7 8 Expected return on plan assets (26 ) (26 ) — — Amortization – prior service credit (8 ) (10 ) (1 ) (1 ) – actuarial loss 9 9 — — – settlement loss 1 — — — Net periodic benefit cost $ 30 $ 23 $ 13 $ 14

Stock-Based Compensation Plans

Stock-Based Compensation Plans (Tables)	3 Months Ended
	Mar. 31, 2018
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, 2018 : Number of Shares Weighted Average Exercise Price Outstanding at December 31, 2017 8,465,398 $ 33.74 Granted 529,197 64.79 Exercised (477,086 ) 24.68 Forfeited or expired (4,512 ) 49.94 Outstanding at March 31, 2018 8,512,997 36.17
Summary of Restricted Stock Award Activity	The following table presents a summary of restricted stock award activity for the three months ended March 31, 2018 : 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, 2017 1,188,662 $ 45.07 285,164 $ 29.95 Granted 94,592 64.79 6,924 67.75 RS’s Vested/RSU’s Issued (123,918 ) 45.06 — — Forfeited (24,639 ) 44.62 — — Outstanding at March 31, 2018 1,134,697 46.72 292,088 30.85
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, 2018 : Number of Units Weighted Average Grant Date Fair Value Outstanding at December 31, 2017 6,851,542 $ 0.81 Granted 3,830,000 0.83 Vested (2,052,959 ) 0.95 Forfeited (10,000 ) 0.92 Outstanding at March 31, 2018 8,618,583 0.79

Supplementary Statistics (Table

Supplementary Statistics (Tables)	3 Months Ended
	Mar. 31, 2018
Text Block [Abstract]
Supplementary Statistics	Supplementary Statistics (Unaudited) Three Months Ended (In millions) 2018 2017 Income (Loss) from Operations by Segment Refining & Marketing (a) $ (133 ) $ (70 ) Speedway 95 135 Midstream (a) 567 309 Items not allocated to segments: Corporate and other unallocated items (88 ) (83 ) Pension settlement expenses (1 ) — Income from operations $ 440 $ 291 Capital Expenditures and Investments (b) Refining & Marketing $ 191 $ 192 Speedway 39 35 Midstream (c) 482 1,070 Corporate and Other (d) 36 28 Total $ 748 $ 1,325 (a) On February 1, 2018, we contributed certain refining logistics assets and fuels distributions services to MPLX. The results of these new businesses are reported in the Midstream segment prospectively from February 1, resulting in a net reduction of $181 million to Refining & Marketing segment results and a net increase to Midstream segment results of the same amount. No effect was given to prior periods as these entities were not considered businesses prior to February 1, 2018. (b) Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates. (c) The three months ended March 31, 2017 includes $220 million for the acquisition of the Ozark pipeline and an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system. (d) Includes capitalized interest of $18 million and $12 million for the three months ended March 31, 2018 and 2017 , respectively
Operating Statistics	Supplementary Statistics (Unaudited) Three Months Ended 2018 2017 MPC Consolidated Refined Product Sales Volumes (mbpd) (a) 2,275 2,085 Refining & Marketing Operating Statistics Refining & Marketing refined product sales volume (mbpd) (b) 2,261 2,070 Refining & Marketing margin (dollars per barrel) (c) $ 10.58 $ 11.65 Crude oil capacity utilization percent (d) 93 83 Refinery throughputs (mbpd): (e) Crude oil refined 1,745 1,511 Other charge and blendstocks 160 197 Total 1,905 1,708 Sour crude oil throughput percent 52 67 WTI-priced crude oil throughput percent 26 15 Refined product yields (mbpd): (e) Gasoline 917 867 Distillates 609 544 Propane 31 28 Feedstocks and special products 287 224 Heavy fuel oil 34 29 Asphalt 58 56 Total 1,936 1,748 Refinery direct operating costs (dollars per barrel): (f) Planned turnaround and major maintenance $ 2.22 $ 3.10 Depreciation and amortization 1.37 1.63 Other manufacturing (g) 4.09 4.72 Total $ 7.68 $ 9.45 Refining & Marketing Operating Statistics By Region - Gulf Coast Refinery throughputs (mbpd): (h) Crude oil refined 1,056 850 Other charge and blendstocks 167 222 Total 1,223 1,072 Sour crude oil throughput percent 60 84 WTI-priced crude oil throughput percent 13 4 Refined product yields (mbpd): (h) Gasoline 534 499 Distillates 360 309 Propane 19 21 Feedstocks and special products 298 243 Heavy fuel oil 23 18 Asphalt 17 14 Total 1,251 1,104 Refinery direct operating costs (dollars per barrel): (f) Planned turnaround and major maintenance $ 2.87 $ 4.31 Depreciation and amortization 1.09 1.35 Other manufacturing (g) 3.91 4.62 Total $ 7.87 $ 10.28 Supplementary Statistics (Unaudited) Three Months Ended 2018 2017 Refining & Marketing Operating Statistics By Region – Midwest Refinery throughputs (mbpd): (h) Crude oil refined 689 661 Other charge and blendstocks 35 30 Total 724 691 Sour crude oil throughput percent 38 45 WTI-priced crude oil throughput percent 47 29 Refined product yields (mbpd): (h) Gasoline 383 368 Distillates 249 235 Propane 12 8 Feedstocks and special products 31 35 Heavy fuel oil 11 11 Asphalt 41 42 Total 727 699 Refinery direct operating costs (dollars per barrel): (f) Planned turnaround and major maintenance $ 0.99 $ 0.98 Depreciation and amortization 1.77 1.93 Other manufacturing (g) 4.16 4.50 Total $ 6.92 $ 7.41 Speedway Operating Statistics Convenience stores at period-end 2,742 2,731 Gasoline and distillate sales (millions of gallons) 1,393 1,393 Gasoline and distillate margin (dollars per gallon) (i) $ 0.1561 $ 0.1566 Merchandise sales (in millions) $ 1,129 $ 1,127 Merchandise margin (in millions) $ 319 $ 320 Merchandise margin percent 28.3 % 28.4 % Same store gasoline sales volume (period over period) (1.5 %) (1.0 %) Same store merchandise sales (period over period) (j) 2.3 % 2.1 % Midstream Operating Statistics Crude oil and refined product pipeline throughputs (mbpd) (k) 3,459 2,888 Terminal throughput (mbpd) 1,445 1,424 Gathering system throughput (MMcf/d) (l) 4,171 3,184 Natural gas processed (MMcf/d) (l) 6,629 6,132 C2 (ethane) + NGLs (natural gas liquids) fractionated (mbpd) (l) 423 367 (a) Total average daily volumes of refined product sales to wholesale, branded and retail customers. (b) Includes intersegment sales. (c) Sales revenue less cost of refinery inputs and purchased products, divided by total refinery throughputs. (d) Based on calendar-day capacity, which is an annual average that includes down time for planned maintenance and other normal operating activities. (e) Excludes inter-refinery volumes of 42 mbpd and 55 mbpd for the three months ended March 31, 2018 and 2017 , respectively. (f) Per barrel of total refinery throughputs. Effective with the February 1, 2018 dropdown, direct operating costs related to certain refining logistics assets are now reported in the Midstream segment. No effect was given to prior periods as this entity was not considered a business prior to February 1, 2018. (g) Includes utilities, labor, routine maintenance and other operating costs. (h) Includes inter-refinery transfer volumes. (i) The price paid by consumers less the cost of refined products, including transportation, consumer excise taxes and bank card processing fees, divided by gasoline and distillate sales volume. (j) Excludes cigarettes. (k) Includes common-carrier pipelines and private pipelines owned or operated by MPLX, excluding equity method investments. (l) Includes amounts related to unconsolidated equity method investments on a 100 percent basis.

ASU 2014-09, Revenue - Revenue

ASU 2014-09, Revenue - Revenue from Contracts with Customers (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption				$ 64
Sales and other operating revenues	[1]	$ 18,694	$ 16,134
Cost of revenues	[1]	17,370	14,946
Matching buy/sell receivables		1,330
Income taxes receivables		323
Consumer Excise Tax
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Sales and other operating revenues			1,200
Cost of revenues			$ 1,200
Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption				$ 1
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Consumer Excise Tax
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Sales and other operating revenues		1,250
Cost of revenues		1,250
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Third Party Reimbursements, Noncash Consideration and Imbalances
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Sales and other operating revenues		117
Cost of revenues		$ 117
[1]	The 2018 period reflects an election to present certain taxes on a net basis. See Notes 2 and 3 for further information.

ASU 2016-16, Income Taxes - Int

ASU 2016-16, Income Taxes - Intra-Entity Transfers of Assets Other Than Inventory (Details) $ in Millions	Dec. 31, 2017USD ($)
Cumulative effect of new accounting principle in period of adoption	$ 64
Accounting Standards Update 2016-16
Cumulative effect of new accounting principle in period of adoption	$ 61

MPLX LP (Detail)

MPLX LP (Detail) - MPLX LP	Mar. 31, 2018
Noncontrolling Interest [Line Items]
Ownership percentage of general partner interest	100.00%
Public's ownership interest in MPLX (in percentage)	36.40%
General Partner and Limited Partner
Noncontrolling Interest [Line Items]
MPC's partnership interest in MPLX (in percentage)	63.60%

MPLX LP - Dropdowns to MPLX and

MPLX LP - Dropdowns to MPLX and GP/IDR Exchange(Details) - MPLX LP - USD ($) shares in Thousands, $ in Millions	Feb. 01, 2018	Jan. 02, 2018	Sep. 01, 2017	Mar. 01, 2017
MPLX 364-day term loan
Noncontrolling Interest [Line Items]
Maximum borrowing capacity	$ 4,100	$ 4,100
Debt instrument, term	364 days	364 days
Cash and Cash Equivalents
Noncontrolling Interest [Line Items]
Payments to acquire business, gross	$ 4,100		$ 420	$ 1,500
Limited Partner
Noncontrolling Interest [Line Items]
Units issued, number of units	112,000		19,000	13,000
Conversion of stock, shares issued	275,000
General Partner
Noncontrolling Interest [Line Items]
Units issued, number of units	2,000		378	264

MPLX LP - Noncontrolling Intere

MPLX LP - Noncontrolling Interest in MPLX (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Increase in MPC's additional paid-in capital, net of tax	$ (546)	$ 114
Additional Paid-in Capital
Increase due to the issuance of MPLX LP common units to the public	4	10
Increase due to the issuance of MPLX LP common units and general partner units to MPC	1,114	96
Increase due to GP/IDR Exchange	1,808	0
Increase in MPC's additional paid-in capital	2,926	106
Tax impact	(546)	(34)
Increase in MPC's additional paid-in capital, net of tax	$ 2,380	$ 72

Acquisitions and Investments -

Acquisitions and Investments - Acquisition of Ozark Pipeline (Details) - Ozark Pipeline bbl / d in Thousands, $ in Millions	Mar. 01, 2017USD ($)bbl / dinmi
Business Acquisition [Line Items]
Pipeline length | mi	433
Pipeline diameter | in	22
Crude oil throughput | bbl / d	230
MPLX LP
Business Acquisition [Line Items]
Payments to acquire business, gross | $	$ 219

Acquisitions and Investments 59

Acquisitions and Investments - Investment in Pipeline Company (Details) bbl / d in Thousands, $ in Millions	Feb. 15, 2017USD ($)bbl / d	Mar. 31, 2017USD ($)
Bakken Pipeline System
Schedule of Equity Method Investments [Line Items]
Crude oil throughput | bbl / d	520
MarEn Bakken
Schedule of Equity Method Investments [Line Items]
Cash paid to acquire equity method investments		$ 500
MPLX LP | Bakken Pipeline System
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	9.20%
MPLX LP | MarEn Bakken
Schedule of Equity Method Investments [Line Items]
Cash paid to acquire equity method investments	$ 500
Equity method investments, ownership percentage	25.00%
MPC & Enbridge Energy Partners | Bakken Pipeline System
Schedule of Equity Method Investments [Line Items]
Percentage of ownership interest in joint venture acquired	36.75%
MPC & Enbridge Energy Partners | MarEn Bakken
Schedule of Equity Method Investments [Line Items]
Cash paid to acquire equity method investments	$ 2,000

Acquisitions and Investments 60

Acquisitions and Investments - Formation of Gathering and Processing Joint Venture (Details) bbl / d in Thousands, $ in Millions	Jan. 01, 2017USD ($)bbl / d	Mar. 31, 2018USD ($)	Mar. 31, 2017USD ($)	[1]
Schedule of Equity Method Investments [Line Items]
Contribution of assets to joint venture		$ 0	$ 328
Sherwood Midstream
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		50.00%
Sherwood Midstream | MPLX LP
Schedule of Equity Method Investments [Line Items]
Contribution of assets to joint venture	$ 134
Payments to acquire interest in joint venture	20
Sherwood Midstream | Antero Midstream Partners L.P.
Schedule of Equity Method Investments [Line Items]
Payments to acquire interest in joint venture	$ 154
Ohio Fractionation
Schedule of Equity Method Investments [Line Items]
Capacity | bbl / d	20
Ohio Fractionation | Sherwood Midstream
Schedule of Equity Method Investments [Line Items]
Payments to acquire interest in joint venture	$ 126
Sherwood Midstream Holdings
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		81.00%
Ownership interest In assets sold by company in affiliate		6.00%
Proceeds from sale of ownership interest in assets sold by company in affiliate		$ 15
Sherwood Midstream Holdings | Direct Ownership Interest
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	79.00%
Sherwood Midstream Holdings | Indirect Ownership Interest
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	10.50%
Sherwood Midstream Holdings | MPLX LP
Schedule of Equity Method Investments [Line Items]
Contribution of assets to joint venture	$ 203
Fair value of assets contributed	209
Gain on disposal of assets	$ 2
Sherwood Midstream Holdings | Sherwood Midstream
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	21.00%
Payments to acquire interest in joint venture	$ 44
[1]	MarkWest’s contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. See Note 5.

Variable Interest Entities (Det

Variable Interest Entities (Details) bbl / d in Thousands, $ in Millions	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Jan. 01, 2017bbl / d
Variable Interest Entity [Line Items]
Equity method investments	$ 4,817	$ 4,787
Crowley Coastal Partners
Variable Interest Entity [Line Items]
VIE, maximum loss exposure, amount	$ 487
MarkWest Utica EMG
Variable Interest Entity [Line Items]
Equity method investments, ownership percentage	56.00%
Equity method investments	$ 2,100
Ohio Gathering
Variable Interest Entity [Line Items]
Equity method investments, ownership percentage	34.00%
Sherwood Midstream
Variable Interest Entity [Line Items]
Equity method investments, ownership percentage	50.00%
Equity method investments	$ 260
Ohio Fractionation
Variable Interest Entity [Line Items]
Capacity | bbl / d			20
Sherwood Midstream Holdings
Variable Interest Entity [Line Items]
Equity method investments, ownership percentage	81.00%
Equity method investments	$ 151
Sherwood Midstream Holdings | Direct Ownership Interest
Variable Interest Entity [Line Items]
Equity method investments, ownership percentage			79.00%
Sherwood Midstream Holdings | Indirect Ownership Interest
Variable Interest Entity [Line Items]
Equity method investments, ownership percentage			10.50%

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Due from related parties, noncurrent	$ 1	$ 1
Crowley Blue Water Partners
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%
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%
MarkWest Utica EMG
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	56.00%
Ohio Gathering
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	34.00%
PFJ Southeast
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	29.00%
Sherwood Midstream
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	50.00%
Sherwood Midstream Holdings
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	81.00%
TAAE
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	45.00%
TACE
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	61.00%
TAME
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	67.00%

Related Party Transactions - Sa

Related Party Transactions - Sales to Related Parties (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Related Party Transaction [Line Items]
Sales to related parties	$ 172	$ 154
PFJ Southeast
Related Party Transaction [Line Items]
Sales to related parties	169	151
Other equity method investees
Related Party Transaction [Line Items]
Sales to related parties	$ 3	$ 3

Related Party Transactions - Ot

Related Party Transactions - Other Income From Related Parties (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Related Party Transaction [Line Items]
Other income from related parties	$ 13	$ 11
MarkWest Utica EMG
Related Party Transaction [Line Items]
Other income from related parties	4	4
Ohio Gathering
Related Party Transaction [Line Items]
Other income from related parties	4	4
Sherwood Midstream
Related Party Transaction [Line Items]
Other income from related parties	3	1
Other equity method investees
Related Party Transaction [Line Items]
Other income from related parties	$ 2	$ 2

Related Party Transactions - Pu

Related Party Transactions - Purchases from Related Parties (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Related Party Transaction [Line Items]
Purchases from related parties	$ 141	$ 122
Crowley Blue Water Partners
Related Party Transaction [Line Items]
Purchases from related parties	16	14
Crowley Ocean Partners
Related Party Transaction [Line Items]
Purchases from related parties	20	19
Illinois Extension Pipeline
Related Party Transaction [Line Items]
Purchases from related parties	24	25
LOCAP
Related Party Transaction [Line Items]
Purchases from related parties	4	5
LOOP
Related Party Transaction [Line Items]
Purchases from related parties	17	13
TAAE
Related Party Transaction [Line Items]
Purchases from related parties	19	8
TACE
Related Party Transaction [Line Items]
Purchases from related parties	8	16
TAME
Related Party Transaction [Line Items]
Purchases from related parties	20	17
Other equity method investees
Related Party Transaction [Line Items]
Purchases from related parties	$ 13	$ 5

Related Party Transactions - Re

Related Party Transactions - Receivables From Related Parties (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Current receivables from related parties	$ 52	$ 36
PFJ Southeast
Related Party Transaction [Line Items]
Current receivables from related parties	30	28
Sherwood Midstream Holdings
Related Party Transaction [Line Items]
Current receivables from related parties	15	0
Other equity method investees
Related Party Transaction [Line Items]
Current receivables from related parties	$ 7	$ 8

Related Party Transactions - Pa

Related Party Transactions - Payables To Related Parties (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Payables to related parties	$ 51	$ 69
Illinois Extension Pipeline
Related Party Transaction [Line Items]
Payables to related parties	7	8
LOOP
Related Party Transaction [Line Items]
Payables to related parties	2	3
MarkWest Utica EMG
Related Party Transaction [Line Items]
Payables to related parties	20	29
Ohio Gathering
Related Party Transaction [Line Items]
Payables to related parties	1	9
Sherwood Midstream
Related Party Transaction [Line Items]
Payables to related parties	11	8
Other equity method investees
Related Party Transaction [Line Items]
Payables to related parties	$ 10	$ 12

Related Party Transactions - Su

Related Party Transactions - Summarized Financial Information for Equity Method Investments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Related Party Transactions [Abstract]
Revenues and other income	$ 1,132	$ 1,027
Income from operations	73	82
Net income	$ 71	$ 81

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, 2018	Mar. 31, 2017
Basic earnings per share:
Net income attributable to MPC	$ 37	$ 30
Income allocated to participating securities	0	0
Income available to common stockholders – basic	$ 37	$ 30
Weighted average common shares outstanding (in shares)	476	525
Basic (in USD per share)	$ 0.08	$ 0.06
Diluted earnings per share:
Net income attributable to MPC	$ 37	$ 30
Income allocated to participating securities	0	0
Income available to common stockholders – diluted	$ 37	$ 30
Weighted average common shares outstanding (in shares)	476	525
Effect of dilutive securities (in shares)	4	5
Weighted average common shares, including dilutive effect (in shares)	480	530
Diluted (in USD per share)	$ 0.08	$ 0.06

Income Per Common Share - Anti-

Income Per Common Share - Anti-dilutive Shares (Details) - shares shares in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Stock Based Compensation Expense [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares issued under stock-based compensation plans	0	2

Equity - Additional Information

Equity - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Apr. 30, 2018	Mar. 31, 2018	Mar. 31, 2017
Stock repurchase program, remaining authorized repurchase amount		$ 1,860
Number of shares repurchased		19,000,000	9,000,000
Cash paid for shares repurchased		$ 1,327	$ 420
Scenario, Forecast
Number of shares repurchased	619,415
Cash paid for shares repurchased	$ 45

Equity - Share Repurchases (Det

Equity - Share Repurchases (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Equity [Abstract]
Number of shares repurchased	19	9
Cash paid for shares repurchased	$ 1,327	$ 420
Average cost per share	$ 68.74	$ 50.15

Segment Information - Additiona

Segment Information - Additional Information (Detail) $ in Millions	Feb. 01, 2018USD ($)	Mar. 31, 2018USD ($)Segmentrefinery	Mar. 31, 2017USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | Segment		3
Number of refineries | refinery		6
Income from operations		$ 440	$ 291
Refining & Marketing
Segment Reporting Information [Line Items]
Income from operations	$ (181)
Midstream
Segment Reporting Information [Line Items]
Income from operations	$ 181

Segment Information - Income Fr

Segment Information - Income From Operations Attributable To Operating Segments (Detail) - USD ($) $ in Millions		Feb. 01, 2018	Mar. 31, 2018		Mar. 31, 2017
Segment Reporting Information [Line Items]
Sales and other operating revenues	[1]		$ 18,694		$ 16,134
Sales to related parties			172		154
Income from operations			440		291
Income from equity method investments			86		57
Depreciation and amortization			528		536
Capital expenditures and investments	[2]		748		1,325
MarEn Bakken
Segment Reporting Information [Line Items]
Cash paid to acquire equity method investments					500
Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues			3,011		2,935	[3]
Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues			21,877		19,223
Income from operations			529		374
Income from equity method investments			86		57
Depreciation and amortization	[4]		512		522
Capital expenditures and investments	[5]		712		1,297
Cash paid to acquire equity method investments			41		566	[6]
Refining & Marketing
Segment Reporting Information [Line Items]
Sales and other operating revenues			13,412		11,221
Sales to related parties			170		152
Income from operations		$ (181)
Refining & Marketing | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues			2,379		2,590
Refining & Marketing | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues			15,961		13,963
Income from operations			(133)		(70)
Income from equity method investments			3		2
Depreciation and amortization			252		267
Capital expenditures and investments			191		192
Speedway
Segment Reporting Information [Line Items]
Sales and other operating revenues			4,569		4,381
Sales to related parties			2		2
Speedway | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues			1		1
Speedway | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues			4,572		4,384
Income from operations			95		135
Income from equity method investments			14		13
Depreciation and amortization			79		64
Capital expenditures and investments			39		35
Midstream
Segment Reporting Information [Line Items]
Sales and other operating revenues			713		532
Sales to related parties			0		0
Income from operations		$ 181
Midstream | Ozark Pipeline
Segment Reporting Information [Line Items]
Capital expenditures and investments					220
Midstream | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues			631		344
Midstream | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues			1,344		876
Income from operations			567	[7]	309
Income from equity method investments			69		42
Depreciation and amortization			181		191
Capital expenditures and investments			482		1,070	[8]
Reportable Segment
Segment Reporting Information [Line Items]
Sales and other operating revenues			$ 18,694		$ 16,134
[1]	The 2018 period reflects an election to present certain taxes on a net basis. See Notes 2 and 3 for further information.
[2]	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
[3]	Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties
[4]	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.
[5]	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
[6]	The three months ended March 31, 2017 includes an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system.
[7]	On February 1, 2018, we contributed certain refining logistics assets and fuels distributions services to MPLX. The results of these new businesses are reported in the Midstream segment prospectively from February 1, resulting in a net reduction of $181 million to Refining & Marketing segment results and a net increase to Midstream segment results of the same amount. No effect was given to prior periods as these entities were not considered businesses prior to February 1, 2018.
[8]	The Midstream segment includes $220 million for the acquisition of the Ozark pipeline and an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system for the three months ended March 31, 2017.

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, 2018	Mar. 31, 2017
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations		$ 440	$ 291
Net interest and other financial income (costs)		183	149
Income before income taxes		257	142
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations		529	374
Corporate and Other
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations	[1]	(88)	(83)
Segment Reconciling Items
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pension settlement expenses		$ (1)	$ 0
[1]	Corporate and other unallocated items consists primarily of MPC’s corporate administrative expenses and costs related to certain non-operating assets, except for corporate overhead expenses attributable to MPLX, which are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments.

Segment Information - Reconci76

Segment Information - Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures [Line Items]
Capital expenditures and investments	[1]	$ 748	$ 1,325
Plus items not allocated to segments:
Capital expenditures	[2]	707	759
MarEn Bakken
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures [Line Items]
Less: Investments in equity method investees			500
Operating Segments
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures [Line Items]
Capital expenditures and investments	[3]	712	1,297
Less: Investments in equity method investees		41	566	[4]
Corporate and Other
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures [Line Items]
Capital expenditures and investments	[5]	36	28
Plus items not allocated to segments:
Corporate		18	16
Capitalized interest		$ 18	$ 12
[1]	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
[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.Revenues by product line were as follows: Three Months Ended March 31,(In millions)2018 2017Refined products$16,158 $13,876Merchandise1,130 1,192Crude oil and refinery feedstocks883 687Service, transportation and other523 379Sales and other operating revenues $18,694 $16,134
[3]	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
[4]	The three months ended March 31, 2017 includes an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system.
[5]	Includes capitalized interest of $18 million and $12 million for the three months ended March 31, 2018 and 2017, respectively

Segment Information - Revenues

Segment Information - Revenues by Product Line (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Revenue from External Customer [Line Items]
Sales and other operating revenues	[1]	$ 18,694	$ 16,134
Refined products
Revenue from External Customer [Line Items]
Sales and other operating revenues		16,158	13,876
Merchandise
Revenue from External Customer [Line Items]
Sales and other operating revenues		1,130	1,192
Crude oil and refinery feedstocks
Revenue from External Customer [Line Items]
Sales and other operating revenues		883	687
Service, transportation and other
Revenue from External Customer [Line Items]
Sales and other operating revenues		$ 523	$ 379
[1]	The 2018 period reflects an election to present certain taxes on a net basis. See Notes 2 and 3 for further information.

Other Items - Net Interest And

Other Items - Net Interest And Other Financial Costs (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Other Income and Expenses [Abstract]
Interest income	$ (20)	$ (5)
Interest expense	213	163
Interest capitalized	(18)	(15)
Loss on extinguishment of debt	4	0
Other financial costs	4	6
Net interest and other financial costs	$ 183	$ 149

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Combined federal, state and foreign income tax rate	9.00%	29.00%
Statutory rate applied to income before income taxes	21.00%	35.00%
Unrecognized benefits	$ 19

Inventories - Summary Of Invent

Inventories - Summary Of Inventories (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Crude oil and refinery feedstocks	$ 1,777	$ 2,056
Refined products	2,746	2,839
Materials and supplies	435	494
Merchandise	153	161
Total	$ 5,111	$ 5,550

Inventories - Additional Inform

Inventories - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Inventory Disclosure [Abstract]
Impact on income as a result of LIFO liquidations	$ 0

Property, Plant And Equipment -

Property, Plant And Equipment - Summary Of Property, Plant And Equipment (Detail) - USD ($) $ in Millions	Feb. 01, 2018	Mar. 31, 2018		Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		$ 41,176		$ 40,538
Less accumulated depreciation		14,558		14,095
Property, plant and equipment, net		26,618		26,443
Refining & Marketing
Property, Plant and Equipment [Line Items]
Property, plant and equipment, transfers	$ (830)
Midstream
Property, Plant and Equipment [Line Items]
Property, plant and equipment, transfers	$ 830
Operating Segments | Refining & Marketing
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		18,117	[1]	19,490
Operating Segments | Speedway
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		5,359		5,358
Operating Segments | Midstream
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		16,889	[1]	14,898
Corporate and Other
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross		$ 811		$ 792
[1]	On February 1, 2018, we contributed certain refining logistics assets and fuels distribution services to MPLX. In connection with this transaction, approximately $830 million of net property, plant and equipment was recorded to the Midstream segment with an offsetting reduction to the Refining & Marketing segment.

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Accounted for at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions		Mar. 31, 2018		Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash collateral netted with derivative liabilities		$ 39		$ 8
Embedded derivatives in commodity contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Embedded derivatives, current		11		12
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - netting and collateral		(21)		(118)
Commodity derivative instruments, assets - collateral pledged not offset		22		8
Other assets		3		3
Total assets at fair value		3		12
Commodity derivative instruments, liabilities - netting and collateral		(60)		(126)
Commodity derivative instruments, liabilities - collateral pledged not offset		0		0
Total liabilities at fair value		60		66
Fair Value, Measurements, Recurring | Commodity derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - netting and collateral	[1]	(21)		(118)
Commodity derivative instruments, assets - net carrying value on balance sheet	[2]	0		9
Commodity derivative instruments, assets - collateral pledged not offset		22		8
Commodity derivative instruments, liabilities - netting and collateral	[1]	(60)		(126)
Commodity derivative instruments, liabilities - net carrying value on balance sheet	[2]	1		2
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]	59		64
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		3		3
Total assets at fair value		24		130
Total liabilities at fair value		60		126
Fair Value, Measurements, Recurring | Level 1 | Commodity derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - gross		21		127
Commodity derivative instruments, liabilities - gross		60		126
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		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		0		0
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		0		0
Total liabilities at fair value		60		66
Fair Value, Measurements, Recurring | Level 3 | Commodity derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - gross		0		0
Commodity derivative instruments, liabilities - gross		1	[3]	2
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	[3]	$ 59		$ 64
[1]	Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of March 31, 2018, cash collateral of $39 million was netted with the mark-to-market derivative liabilities. As of December 31, 2017, $8 million was netted with mark-to-market derivative liabilities.
[2]	We have no derivative contracts that are subject to master netting arrangements reflected gross on the balance sheet.
[3]	Level 3 includes $11 million and $12 million classified as current at March 31, 2018 and December 31, 2017, respectively.

Fair Value Measurements - Recur

Fair Value Measurements - Recurring Narrative (Detail)	3 Months Ended
	Mar. 31, 2018USD ($)
Commodity derivatives | Level 3 | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward commodity price	$ 0.26
Commodity derivatives | Level 3 | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward commodity price	$ 1.47
Embedded derivatives in commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Embedded derivative renewal term	5 years
Embedded derivatives in commodity contracts | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Probability of renewal first term	62.50%
Probability of renewal second term	82.00%

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, 2018	Mar. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 66	$ 190
Unrealized and realized losses included in net income	(3)	(12)
Settlements of derivative instruments	(3)	(3)
Ending balance	$ 60	$ 175

Fair Value Measurements - Losse

Fair Value Measurements - Losses Included in Earnings Relating to Assets Still Held at End of Period (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
The amount of total losses for the period included in earnings attributable to the change in unrealized losses relating to assets still held at the end of period:	$ (3)	$ (12)
Derivative
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
The amount of total losses for the period included in earnings attributable to the change in unrealized losses relating to assets still held at the end of period:	(3)	(13)
Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
The amount of total losses for the period included in earnings attributable to the change in unrealized losses relating to assets still held at the end of period:	$ 0	$ 1

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, 2018	Dec. 31, 2017
Fair Value
Financial assets:
Environmental receivables and misc. deposits		$ 18	$ 17
Total financial assets		18	17
Financial liabilities:
Long-term debt	[1]	17,893	13,893
Deferred credits and other liabilities		118	122
Total financial liabilities		18,011	14,015
Carrying Value
Financial assets:
Environmental receivables and misc. deposits		18	17
Total financial assets		18	17
Financial liabilities:
Long-term debt	[1]	17,010	12,642
Deferred credits and other liabilities		108	109
Total financial liabilities		$ 17,118	$ 12,751
[1]	Excludes capital leases and debt issuance costs; 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, 2018	Dec. 31, 2017
Other current assets
Derivatives, Fair Value [Line Items]
Asset		$ 21	$ 127
Liability		60	126
Other current liabilities(a)
Derivatives, Fair Value [Line Items]
Asset		0	0
Liability	[1]	12	14
Deferred credits and other liabilities
Derivatives, Fair Value [Line Items]
Asset		0	0
Liability	[1]	$ 48	$ 52
[1]	Includes embedded derivatives.

Derivatives - Open Commodity De

Derivatives - Open Commodity Derivative Contracts - Crude Oil (Details) - Crude Oil - Exchange Traded bbl in Thousands	3 Months Ended
	Mar. 31, 2018bbl
Derivative [Line Items]
Percentage of derivative contracts expiring in the period	94.70%
Derivative contract expiration date	Jun. 30, 2017
Long
Derivative [Line Items]
Notional contracts (in thousands of Total Barrels)	16,664	[1]
Short
Derivative [Line Items]
Notional contracts (in thousands of Total Barrels)	22,145	[1]
[1]	of the exchange-traded contracts expire in the second quarter of 2018.

Derivatives - Open Commodity 90

Derivatives - Open Commodity Derivative Contracts - Refined Products (Detail) - Refined products - Exchange Traded gal in Thousands	3 Months Ended
	Mar. 31, 2018gal
Derivative [Line Items]
Percentage of derivative contracts expiring in the period	100.00%
Derivative contract expiration date	Jun. 30, 2017
Long
Derivative [Line Items]
Notional contracts (in thousands of Total Gallons)	159,390	[1]
Short
Derivative [Line Items]
Notional contracts (in thousands of Total Gallons)	147,252	[1]
[1]	of the exchange-traded contracts expire in the second quarter of 2018.

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, 2018	Mar. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	$ (28)	$ (8)
Sales and other operating revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	(1)	16
Cost of revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	$ (27)	$ (24)

Debt - Outstanding Borrowings (

Debt - Outstanding Borrowings (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Feb. 08, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Commercial paper		$ 0
Total		17,807		$ 13,418
Unamortized debt issuance costs		(109)		(59)
Unamortized discount	[1]	(440)		(413)
Amounts due within one year		(26)		(624)
Total long-term debt due after one year		17,232		12,322
MPLX LP
Debt Instrument [Line Items]
Amounts due within one year		(1)		(1)
Total long-term debt due after one year		11,861		6,945
Senior Notes | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross			$ 5,500
Senior Notes | MarkWest | MPLX LP
Debt Instrument [Line Items]
Unamortized discount		(362)		(374)
Trade receivables securitization facility due July 2019
Debt Instrument [Line Items]
Long-term debt, gross		0
MPLX bank revolving credit facility due 2022 | Line of Credit | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross		0
MPLX senior notes, 3.375%, due March 2023 | Senior Notes | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross			$ 500
Debt instrument, interest rate			3.375%
MPLX senior notes, 4.000%, due March 2028 | Senior Notes | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross			$ 1,250
Debt instrument, interest rate			4.00%
MPLX senior notes, 4.500%, due April 2038 | Senior Notes | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross			$ 1,750
Debt instrument, interest rate			4.50%
MPLX senior notes, 4.700%, due April 2048 | Senior Notes | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross			$ 1,500
Debt instrument, interest rate			4.70%
MPLX senior notes, 4.900%, due April 2058 | Senior Notes | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross			$ 500
Debt instrument, interest rate			4.90%
Marathon Petroleum Corporation
Debt Instrument [Line Items]
Commercial paper		0		0
Marathon Petroleum Corporation | Capital Lease Obligations
Debt Instrument [Line Items]
Capital lease obligations		$ 350		356
Debt instrument maturity year, start		Jan. 1, 2018
Debt instrument maturity year, end		Mar. 31, 2033
Marathon Petroleum Corporation | 364-day bank revolving credit facility due July 2018 | Line of Credit
Debt Instrument [Line Items]
Long-term debt, gross		$ 0		0
Line of credit facility, expiration date		Jul. 20, 2018
Marathon Petroleum Corporation | Trade receivables securitization facility due July 2019 | Secured Debt
Debt Instrument [Line Items]
Long-term debt, gross		$ 0		0
Line of credit facility, expiration date		Jul. 19, 2019
Marathon Petroleum Corporation | Bank revolving credit facility due 2022 | Line of Credit
Debt Instrument [Line Items]
Long-term debt, gross		$ 0		0
Line of credit facility, expiration date		Jul. 21, 2022
Marathon Petroleum Corporation | Senior notes, 2.700% due December 2018 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 0		600
Debt instrument, maturity date		Dec. 14, 2018
Debt instrument, interest rate		2.70%
Marathon Petroleum Corporation | 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%
Marathon Petroleum Corporation | 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%
Marathon Petroleum Corporation | 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%
Marathon Petroleum Corporation | 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%
Marathon Petroleum Corporation | 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%
Marathon Petroleum Corporation | 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%
Marathon Petroleum Corporation | 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 LP | Senior Notes | MarkWest
Debt Instrument [Line Items]
Long-term debt, gross		$ 63		63
MPLX LP | Capital Lease Obligations
Debt Instrument [Line Items]
Capital lease obligations		$ 7		7
Debt instrument maturity year, start		Jan. 1, 2018
Debt instrument maturity year, end		Mar. 31, 2020
MPLX LP | MPLX 364-day term loan | Unsecured Debt
Debt Instrument [Line Items]
Long-term debt, gross		$ 0		0
Line of credit facility, expiration date		Dec. 31, 2018
MPLX LP | MPLX term loan facility due 2019 | Unsecured Debt
Debt Instrument [Line Items]
Long-term debt, gross		$ 0		0
Line of credit facility, expiration date		Nov. 20, 2019
MPLX LP | MPLX bank revolving credit facility due 2022 | Line of Credit
Debt Instrument [Line Items]
Long-term debt, gross		$ 0		505
Line of credit facility, expiration date		Jul. 21, 2022
MPLX LP | MPLX senior notes, 5.500%, due February 2023 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 710		710
Debt instrument, maturity date		Feb. 15, 2023
Debt instrument, interest rate		5.50%
MPLX LP | MPLX senior notes, 5.500%, due February 2023 | Senior Notes | MarkWest
Debt Instrument [Line Items]
Debt instrument, maturity date		Feb. 15, 2023
Debt instrument, interest rate		5.50%
MPLX LP | MPLX senior notes, 3.375%, due March 2023 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 500		0
Debt instrument, maturity date		Mar. 15, 2023
Debt instrument, interest rate		3.375%
MPLX LP | MPLX senior notes, 4.500%, due July 2023 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 989		989
Debt instrument, maturity date		Jul. 15, 2023
Debt instrument, interest rate		4.50%
MPLX LP | MPLX senior notes, 4.500%, due July 2023 | Senior Notes | MarkWest
Debt Instrument [Line Items]
Debt instrument, maturity date		Jul. 15, 2023
Debt instrument, interest rate		4.50%
MPLX LP | MPLX senior notes, 4.875%, due December 2024 | Senior Notes
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 LP | MPLX senior notes, 4.875%, due December 2024 | Senior Notes | MarkWest
Debt Instrument [Line Items]
Debt instrument, maturity date		Dec. 1, 2024
Debt instrument, interest rate		4.875%
MPLX LP | MPLX senior notes, 4.000%, due February 2025 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 500		500
Debt instrument, maturity date		Feb. 15, 2025
Debt instrument, interest rate		4.00%
MPLX LP | MPLX senior notes, 4.875%, due June 2025 | Senior Notes
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 LP | MPLX senior notes, 4.875%, due June 2025 | Senior Notes | MarkWest
Debt Instrument [Line Items]
Debt instrument, maturity date		Jun. 1, 2025
Debt instrument, interest rate		4.875%
MPLX LP | MPLX senior notes, 4.125%, due March 2027 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,250		1,250
Debt instrument, maturity date		Mar. 1, 2027
Debt instrument, interest rate		4.125%
MPLX LP | MPLX senior notes, 4.000%, due March 2028 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,250		0
Debt instrument, maturity date		Mar. 15, 2028
Debt instrument, interest rate		4.00%
MPLX LP | MPLX senior notes, 4.500%, due April 2038 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,750		0
Debt instrument, maturity date		Apr. 15, 2038
Debt instrument, interest rate		4.50%
MPLX LP | MPLX senior notes, 5.200%, due March 2047 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,000		1,000
Debt instrument, maturity date		Mar. 1, 2047
Debt instrument, interest rate		5.20%
MPLX LP | MPLX senior notes, 4.700%, due April 2048 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,500		0
Debt instrument, maturity date		Apr. 15, 2048
Debt instrument, interest rate		4.70%
MPLX LP | MPLX senior notes, 4.900%, due April 2058 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 500		$ 0
Debt instrument, maturity date		Apr. 15, 2058
Debt instrument, interest rate		4.90%
[1]	Includes $362 million and $374 million of unamortized discount as of March 31, 2018 and December 31, 2017, respectively, related to the difference between the fair value and the principal amount of assumed MarkWest debt.

Debt - Commercial Paper (Detail

Debt - Commercial Paper (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Debt Disclosure [Abstract]
Commercial paper – issued	$ 0	$ 300
Commercial paper - repayments	0	$ 300
Commercial paper, outstanding balance	$ 0

Debt - Trade Receivables Securi

Debt - Trade Receivables Securitization Facility (Details) - Trade receivables securitization facility due July 2019 $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Debt Instrument [Line Items]
Borrowings	$ 0
Repayments	0
Long-term debt, gross	$ 0

Debt - MPC Bank Revolving Credi

Debt - MPC Bank Revolving Credit Facilities (Details) - Marathon Petroleum Corporation - Bank revolving credit facility due 2022 - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Letter of Credit
Debt Instrument [Line Items]
Long-term line of credit	$ 0
Line of Credit
Debt Instrument [Line Items]
Long-term debt, gross	$ 0	$ 0

Debt - MPC Senior Notes (Detail

Debt - MPC Senior Notes (Details) - Senior notes, 2.700% due December 2018 $ in Millions	Mar. 15, 2018USD ($)
Debt Instrument [Line Items]
Repayments of long-term debt	$ 600
Make whole premium	$ 2.5

Debt - MPLX Credit Agreement (D

Debt - MPLX Credit Agreement (Details) - MPLX LP - MPLX bank revolving credit facility due 2022 $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Debt Instrument [Line Items]
Borrowings	$ 50
Interest rate during period	3.00%
Repayments	$ 555
Remaining borrowing capacity	2,250
Letter of Credit
Debt Instrument [Line Items]
Long-term line of credit	3
Line of Credit
Debt Instrument [Line Items]
Long-term debt, gross	$ 0

Debt - MPLX 364-Day Term Loan (

Debt - MPLX 364-Day Term Loan (Details) - MPLX LP - MPLX 364-day term loan - USD ($) $ in Billions	Feb. 08, 2018	Feb. 01, 2018	Jan. 02, 2018
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 4.1	$ 4.1
Debt instrument, term		364 days	364 days
Borrowings		$ 4.1
Repayments of short-term debt	$ 4.1

Debt - MPLX Senior Notes (Detai

Debt - MPLX Senior Notes (Details) - MPLX LP $ in Millions	Feb. 08, 2018USD ($)
MPLX 364-day term loan
Debt Instrument [Line Items]
Repayments of short-term debt	$ 4,100
Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross	5,500
Senior Notes | MPLX senior notes, 3.375%, due March 2023
Debt Instrument [Line Items]
Long-term debt, gross	$ 500
Debt instrument, interest rate	3.375%
Senior Notes | MPLX senior notes, 4.000%, due March 2028
Debt Instrument [Line Items]
Long-term debt, gross	$ 1,250
Debt instrument, interest rate	4.00%
Senior Notes | MPLX senior notes, 4.500%, due April 2038
Debt Instrument [Line Items]
Long-term debt, gross	$ 1,750
Debt instrument, interest rate	4.50%
Senior Notes | MPLX senior notes, 4.700%, due April 2048
Debt Instrument [Line Items]
Long-term debt, gross	$ 1,500
Debt instrument, interest rate	4.70%
Senior Notes | MPLX senior notes, 4.900%, due April 2058
Debt Instrument [Line Items]
Long-term debt, gross	$ 500
Debt instrument, interest rate	4.90%

Supplemental Cash Flow Infor100

Supplemental Cash Flow Information - Summary of Supplemental Cash Flow Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net cash provided by operating activities included:
Interest paid (net of amounts capitalized)	$ 212	$ 157
Net income taxes paid to taxing authorities	6	4
Non-cash investing and financing activities:
Contribution of assets to joint venture	$ 0	$ 328	[1]
[1]	MarkWest’s contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. See Note 5.

Supplemental Cash Flow Infor101

Supplemental Cash Flow Information - Cash, Cash Equalivalents and Restricted Cash (Details) - USD ($) $ in Millions		Mar. 31, 2018		Dec. 31, 2017		Mar. 31, 2017	Dec. 31, 2016
Supplemental Cash Flow Elements [Abstract]
Cash and cash equivalents		$ 4,653		$ 3,011
Restricted cash	[1]	4		4
Cash, cash equivalents and restricted cash		$ 4,657	[2]	$ 3,015	[2]	$ 2,170	$ 892
[1]	The restricted cash balance is included within “Other current assets” on the consolidated balance sheets
[2]	As a result of the adoption of ASU 2016-18, the consolidated statements of cash flows now explain the change during the period of both “Cash and cash equivalents” and “Restricted cash.”

Supplemental Cash Flow Infor102

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, 2018	Mar. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Additions to property, plant and equipment per consolidated statements of cash flows		$ 755	$ 610
Asset retirement expenditures		1	1
Decrease in capital accruals		(49)	(72)
Total capital expenditures before acquisitions		707	539
Acquisitions		0	220	[1]
Capital expenditures	[2]	$ 707	$ 759
[1]	The three months ended March 31, 2017 reflects the acquisition of the Ozark pipeline.
[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.Revenues by product line were as follows: Three Months Ended March 31,(In millions)2018 2017Refined products$16,158 $13,876Merchandise1,130 1,192Crude oil and refinery feedstocks883 687Service, transportation and other523 379Sales and other operating revenues $18,694 $16,134

Accumulated Other Comprehens103

Accumulated Other Comprehensive Loss - Changes in Accumulated Other Comprehensive Loss by Component (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		$ (231)	$ (234)
Other comprehensive loss before reclassifications		(2)	(1)
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit		(9)	(11)
Amortization - actuarial loss		9	9
Amortization - settlement loss		1	0
Tax effect		(1)	0
Other comprehensive loss		(2)	(3)
Ending balance		(233)	(237)
Accumulated Defined Benefit Plans Adjustment | Pension Benefits
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(190)	(233)
Other comprehensive loss before reclassifications		0	(1)
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit	[1]	(8)	(10)
Amortization - actuarial loss	[1]	9	9
Amortization - settlement loss	[1]	1	0
Tax effect		(1)	0
Other comprehensive loss		1	(2)
Ending balance		(189)	(235)
Accumulated Defined Benefit Plans Adjustment | Other Benefits
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(48)	(7)
Other comprehensive loss before reclassifications		0	0
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit	[1]	(1)	(1)
Amortization - actuarial loss	[1]	0	0
Amortization - settlement loss		0	0
Tax effect		0	0
Other comprehensive loss		(1)	(1)
Ending balance		(49)	(8)
Gain on Cash Flow Hedge
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		4	4
Other comprehensive loss before reclassifications		(2)	0
Amounts reclassified from accumulated other comprehensive loss:
Tax effect		0	0
Other comprehensive loss		(2)	0
Ending balance		2	4
Workers Compensation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		3	2
Other comprehensive loss before reclassifications		0	0
Amounts reclassified from accumulated other comprehensive loss:
Tax effect		0	0
Other comprehensive loss		0	0
Ending balance		$ 3	$ 2
[1]	These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 20.

Defined Benefit Pension and 104

Defined Benefit Pension and Other Postretirement Plans - Components of Net Periodic Benefit Costs (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Pension Benefits
Components of net periodic benefit cost:
Service cost	$ 36	$ 31
Interest cost	18	19
Expected return on plan assets	(26)	(26)
Amortization – prior service credit	(8)	(10)
Amortization – actuarial loss (gain)	9	9
Amortization - settlement loss	1	0
Net periodic benefit cost	30	23
Other Benefits
Components of net periodic benefit cost:
Service cost	7	7
Interest cost	7	8
Expected return on plan assets	0	0
Amortization – prior service credit	(1)	(1)
Amortization – actuarial loss (gain)	0	0
Amortization - settlement loss	0	0
Net periodic benefit cost	$ 13	$ 14

Defined Benefit Pension and 105

Defined Benefit Pension and Other Postretirement Plans - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 0
Other Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Benefits paid	6
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Benefits paid	$ 8

Stock-Based Compensation Pla106

Stock-Based Compensation Plans - Summary of Stock Option Award Activity (Detail) - Stock Options	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Number of Shares
Outstanding, beginning balance | shares	8,465,398
Granted | shares	529,197
Exercised | shares	(477,086)
Forfeited or expired | shares	(4,512)
Outstanding, ending balance | shares	8,512,997
Weighted Average Exercise Price
Outstanding, beginning balance (in USD per share) | $ / shares	$ 33.74
Granted (in USD per share) | $ / shares	64.79
Exercised (in USD per share) | $ / shares	24.68
Forfeited or expired (in USD per share) | $ / shares	49.94
Outstanding, ending balance (in USD per share) | $ / shares	$ 36.17

Stock-Based Compensation Pla107

Stock-Based Compensation Plans - Narrative (Detail)	3 Months Ended
	Mar. 31, 2018$ / shares
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date fair value (in USD per share)	$ 17.37
Performance Unit Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in USD per share)	$ 0.83

Stock-Based Compensation Pla108

Stock-Based Compensation Plans - Summary of Restricted Stock Award Activity (Detail)	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Restricted Stock
Number of Shares
Outstanding, beginning balance | shares	1,188,662
Granted | shares	94,592
RS’s Vested/RSU’s Issued | shares	(123,918)
Forfeited | shares	(24,639)
Outstanding, ending balance | shares	1,134,697
Weighted Average Grant Date Fair Value
Outstanding, beginning balance (in USD per share) | $ / shares	$ 45.07
Granted (in USD per share) | $ / shares	64.79
RS's Vested/RSU's Issued (in USD per share) | $ / shares	45.06
Forfeited (in USD per share) | $ / shares	44.62
Outstanding, ending balance (in USD per share) | $ / shares	$ 46.72
Restricted Stock Units
Number of Shares
Outstanding, beginning balance | shares	285,164
Granted | shares	6,924
RS’s Vested/RSU’s Issued | shares	0
Forfeited | shares	0
Outstanding, ending balance | shares	292,088
Weighted Average Grant Date Fair Value
Outstanding, beginning balance (in USD per share) | $ / shares	$ 29.95
Granted (in USD per share) | $ / shares	67.75
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	$ 30.85

Stock-Based Compensation Pla109

Stock-Based Compensation Plans - Summary of Performance Unit Awards (Detail) - Performance Unit Awards	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Number of Units
Outstanding, beginning balance | shares	6,851,542
Granted | shares	3,830,000
Vested | shares	(2,052,959)
Forfeited | shares	(10,000)
Outstanding, ending balance | shares	8,618,583
Weighted Average Grant Date Fair Value
Outstanding, beginning balance (in USD per share) | $ / shares	$ 0.81
Granted (in USD per share) | $ / shares	0.83
Vested (in USD per share) | $ / shares	0.95
Forfeited (in USD per share) | $ / shares	0.92
Outstanding, ending balance (in USD per share) | $ / shares	$ 0.79

Commitments and Contingencies (

Commitments and Contingencies (Detail)	3 Months Ended
	Mar. 31, 2018
Pending Litigation
Loss Contingencies [Line Items]
Loss contingency, inestimable loss	For matters for which we have not recorded a liability, we are unable to estimate a range of possible loss because the issues involved have not been fully developed through pleadings, discovery or court proceedings.

Commitments and Contingencies -

Commitments and Contingencies - Environmental Matters (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Accrued liabilities for remediation	$ 112	$ 114
Receivables for recoverable costs	$ 45	$ 45

Commitments and Contingencie112

Commitments and Contingencies - MarkWest Environmental Proceeding (Details) - MarkWest Liberty Midstream Pipeline Launcher/Receiver Site - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Apr. 30, 2018	Mar. 31, 2018
Cash | Pending Litigation
Loss Contingencies [Line Items]
Damages sought		$ 0.6
Cash | Subsequent Event | Settled Litigation
Loss Contingencies [Line Items]
Damages sought	$ 0.6
Other Liabilities | Pending Litigation
Loss Contingencies [Line Items]
Damages sought		$ 2.4
Other Liabilities | Subsequent Event | Settled Litigation
Loss Contingencies [Line Items]
Damages sought	$ 2.4

Commitments and Contingencie113

Commitments and Contingencies - Other Lawsuits (Details) - Pending Litigation $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Construction Work at MarkWest Processing and Fractionation Complexes | Minimum
Loss Contingencies [Line Items]
Damages sought	$ 40
Construction Work at MarkWest Processing and Fractionation Complexes | Minimum | MPLX LP
Loss Contingencies [Line Items]
Damages sought	$ 10
Emergency Pricing And Consumer Protection Laws
Loss Contingencies [Line Items]
Plaintiff	Commonwealth of Kentucky
Damages sought	$ 89
Loss contingency, period of occurrence	during September and October 2005

Commitments and Contingencie114

Commitments and Contingencies - Guarantees (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Other Guarantees
Loss Contingencies [Line Items]
Maximum potential undiscounted payments	$ 93
Guarantee obligations maximum exposure per event	$ 50
LOOP and LOCAP LLC | Guarantee of Indebtedness of Others | Financial Guarantee
Loss Contingencies [Line Items]
Line of credit facility, expiration date	Dec. 31, 2037
Maximum potential undiscounted payments	$ 160
Centennial | Guarantee of Indebtedness of Others | Financial Guarantee
Loss Contingencies [Line Items]
Maximum potential undiscounted payments	$ 24
Centennial | Master Shelf Agreement [Member] | Financial Guarantee
Loss Contingencies [Line Items]
Line of credit facility, expiration date	Dec. 31, 2024
Crowley Ocean Partners
Loss Contingencies [Line Items]
Equity method investments, ownership percentage	50.00%
Crowley Ocean Partners | Guarantee of Indebtedness of Others | Financial Guarantee
Loss Contingencies [Line Items]
Maximum potential undiscounted payments	$ 163
Crowley Ocean Partners | Guarantee of Indebtedness of Others | Financial Guarantee | Crowley Term Loan
Loss Contingencies [Line Items]
Maximum borrowing capacity	$ 325
Crowley Blue Water Partners
Loss Contingencies [Line Items]
Equity method investments, ownership percentage	50.00%
Crowley Blue Water Partners | Guarantee of Indebtedness of Others | Financial Guarantee
Loss Contingencies [Line Items]
Maximum potential undiscounted payments	$ 132
Marathon Oil Companies | Indemnification Agreement
Loss Contingencies [Line Items]
Guarantee obligation current carrying value	$ 2

Commitments and Contingencie115

Commitments and Contingencies - Contractual Commitments and Contingencies (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
Contractual commitments to acquire property, plant and equipment and advance funds to equity method investees	$ 879

Supplementary Statistics - Supp

Supplementary Statistics - Supplementary Statistics (Detail) - USD ($) $ in Millions		Feb. 01, 2018	Mar. 31, 2018		Mar. 31, 2017
Supplementary Statistics [Line Items]
Income from operations			$ 440		$ 291
Capital expenditures and investments	[1]		748		1,325
MarEn Bakken
Supplementary Statistics [Line Items]
Cash paid to acquire equity method investments					500
Refining & Marketing
Supplementary Statistics [Line Items]
Income from operations		$ (181)
Midstream
Supplementary Statistics [Line Items]
Income from operations		$ 181
Midstream | Ozark Pipeline
Supplementary Statistics [Line Items]
Capital expenditures and investments					220
Operating Segments
Supplementary Statistics [Line Items]
Income from operations			529		374
Capital expenditures and investments	[2]		712		1,297
Cash paid to acquire equity method investments			41		566	[3]
Operating Segments | Refining & Marketing
Supplementary Statistics [Line Items]
Income from operations			(133)		(70)
Capital expenditures and investments			191		192
Operating Segments | Speedway
Supplementary Statistics [Line Items]
Income from operations			95		135
Capital expenditures and investments			39		35
Operating Segments | Midstream
Supplementary Statistics [Line Items]
Income from operations			567	[4]	309
Capital expenditures and investments			482		1,070	[5]
Corporate and Other
Supplementary Statistics [Line Items]
Income from operations	[6]		(88)		(83)
Capital expenditures and investments	[7]		36		28
Capitalized interest			18		12
Segment Reconciling Items
Supplementary Statistics [Line Items]
Pension settlement expenses			$ (1)		$ 0
[1]	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
[2]	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
[3]	The three months ended March 31, 2017 includes an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system.
[4]	On February 1, 2018, we contributed certain refining logistics assets and fuels distributions services to MPLX. The results of these new businesses are reported in the Midstream segment prospectively from February 1, resulting in a net reduction of $181 million to Refining & Marketing segment results and a net increase to Midstream segment results of the same amount. No effect was given to prior periods as these entities were not considered businesses prior to February 1, 2018.
[5]	The Midstream segment includes $220 million for the acquisition of the Ozark pipeline and an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system for the three months ended March 31, 2017.
[6]	Corporate and other unallocated items consists primarily of MPC’s corporate administrative expenses and costs related to certain non-operating assets, except for corporate overhead expenses attributable to MPLX, which are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments.
[7]	Includes capitalized interest of $18 million and $12 million for the three months ended March 31, 2018 and 2017, respectively

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, 2018USD ($)bbl / dStoreCFPD$ / gal$ / bblgal	Mar. 31, 2017USD ($)bbl / dStoreCFPD$ / gal$ / bblgal
Operating Statistics [Line Items ]
MPC Consolidated Refined Product Sales Volumes (thousands of barrels per day)	[1]	2,275	2,085
Refining & Marketing
Refining & Marketing Operating Statistics
Refining & Marketing refined product sales volume (thousands of barrels per day)	[2]	2,261	2,070
Refining & Marketing margin (dollars per barrel) | $ / bbl	[3]	10.58	11.65
Crude oil capacity utilization percent	[4]	93.00%	83.00%
Refinery throughputs (thousands of barrels per day)	[5]	1,905	1,708
Sour crude oil throughput percent		52.00%	67.00%
WTI-priced crude oil throughput percent		26.00%	15.00%
Refined product yields (thousands of barrels per day)	[5]	1,936	1,748
Inter-refinery transfers		42	55
Refinery direct operating costs (dollars per barrel):
Planned turnaround and major maintenance | $ / bbl	[6]	2.22	3.10
Depreciation and amortization | $ / bbl	[6]	1.37	1.63
Other manufacturing | $ / bbl	[6],[7]	4.09	4.72
Total | $ / bbl	[6]	7.68	9.45
Refining & Marketing | Crude oil refined
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[5]	1,745	1,511
Refining & Marketing | Other charge and blendstocks
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[5]	160	197
Refining & Marketing | Gasoline
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	917	867
Refining & Marketing | Distillates
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	609	544
Refining & Marketing | Propane
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	31	28
Refining & Marketing | Feedstocks and special products
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	287	224
Refining & Marketing | Heavy fuel oil
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	34	29
Refining & Marketing | Asphalt
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	58	56
Refining & Marketing | Gulf Coast:
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	1,223	1,072
Sour crude oil throughput percent		60.00%	84.00%
WTI-priced crude oil throughput percent		13.00%	4.00%
Refined product yields (thousands of barrels per day)	[8]	1,251	1,104
Refinery direct operating costs (dollars per barrel):
Planned turnaround and major maintenance | $ / bbl	[6]	2.87	4.31
Depreciation and amortization | $ / bbl	[6]	1.09	1.35
Other manufacturing | $ / bbl	[6],[7]	3.91	4.62
Total | $ / bbl	[6]	7.87	10.28
Refining & Marketing | Gulf Coast: | Crude oil refined
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	1,056	850
Refining & Marketing | Gulf Coast: | Other charge and blendstocks
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	167	222
Refining & Marketing | Gulf Coast: | Gasoline
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	534	499
Refining & Marketing | Gulf Coast: | Distillates
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	360	309
Refining & Marketing | Gulf Coast: | Propane
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	19	21
Refining & Marketing | Gulf Coast: | Feedstocks and special products
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	298	243
Refining & Marketing | Gulf Coast: | Heavy fuel oil
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	23	18
Refining & Marketing | Gulf Coast: | Asphalt
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	17	14
Refining & Marketing | Midwest:
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	724	691
Sour crude oil throughput percent		38.00%	45.00%
WTI-priced crude oil throughput percent		47.00%	29.00%
Refined product yields (thousands of barrels per day)	[8]	727	699
Refinery direct operating costs (dollars per barrel):
Planned turnaround and major maintenance | $ / bbl	[6]	0.99	0.98
Depreciation and amortization | $ / bbl	[6]	1.77	1.93
Other manufacturing | $ / bbl	[6],[7]	4.16	4.50
Total | $ / bbl	[6]	6.92	7.41
Refining & Marketing | Midwest: | Crude oil refined
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	689	661
Refining & Marketing | Midwest: | Other charge and blendstocks
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	35	30
Refining & Marketing | Midwest: | Gasoline
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	383	368
Refining & Marketing | Midwest: | Distillates
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	249	235
Refining & Marketing | Midwest: | Propane
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	12	8
Refining & Marketing | Midwest: | Feedstocks and special products
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	31	35
Refining & Marketing | Midwest: | Heavy fuel oil
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	11	11
Refining & Marketing | Midwest: | Asphalt
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	41	42
Speedway
Speedway Operating Statistics
Convenience stores at period-end | Store		2,742	2,731
Gasoline and distillate sales (millions of gallons) | gal		1,393	1,393
Gasoline and distillate margin (dollars per gallon) | $ / gal	[9]	0.1561	0.1566
Merchandise sales (in millions) | $		$ 1,129	$ 1,127
Merchandise margin (in millions) | $		$ 319	$ 320
Merchandise margin percent		28.30%	28.40%
Same store gasoline sales volume (period over period) percentage		(1.50%)	(1.00%)
Merchandise sales excluding cigarettes (period over period) percentage	[10]	2.30%	2.10%
Midstream
Midstream Operating Statistics
Crude oil and refined product pipeline throughputs (thousands of barrels per day)	[11]	3,459	2,888
Terminal throughput (thousands of barrels per day)		1,445	1,424
Gathering system throughput (MMcf/d) | CFPD	[12]	4,171	3,184
Natural gas processed (MMcf/d) | CFPD	[12]	6,629	6,132
C2 and NGLs fractionated (thousands barrels per day)	[12]	423	367
[1]	Total average daily volumes of refined product sales to wholesale, branded and retail customers.
[2]	Includes intersegment sales.
[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 down time for planned maintenance and other normal operating activities.
[5]	Excludes inter-refinery volumes of 42 mbpd and 55 mbpd for the three months ended March 31, 2018 and 2017, respectively
[6]	Per barrel of total refinery throughputs. Effective with the February 1, 2018 dropdown, direct operating costs related to certain refining logistics assets are now reported in the Midstream segment. No effect was given to prior periods as this entity was not considered a business prior to February 1, 2018.
[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 bank card processing fees, divided by gasoline and distillate sales volume.
[10]	Excludes cigarettes.
[11]	Includes common-carrier pipelines and private pipelines owned or operated by MPLX, excluding equity method investments.
[12]	Includes amounts related to unconsolidated equity method investments on a 100 percent basis.

Subsequent Event Subsequent Eve

Subsequent Event Subsequent Event (Detail) - Subsequent Event - USD ($)	Apr. 29, 2018	Apr. 27, 2018
Subsequent Event [Line Items]
Equity value		$ 23,300,000,000
Enterprise value		$ 35,600,000,000
Share price		$ 81.43
Share conversion rate	1.87
Cash consideration to unitholders	$ 152.27
Percent paid in common stock	85.00%
Percent paid in cash	15.00%
MPC
Subsequent Event [Line Items]
Ownership of combined company	66.00%
Andeavor
Subsequent Event [Line Items]
Ownership of combined company	34.00%