Marathon Petroleum (MPC) 10-Q 30 Oct 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Oct. 27, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus (Q1,Q2,Q3,FY)	Q3
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		488,412,170

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenues and other income:
Sales and other operating revenues (including consumer excise taxes)	$ 19,053	$ 16,616	$ 53,220	$ 46,179
Sales to related parties	157	2	458	5
Income (loss) from equity method investments	84	(208)	224	(236)
Net gain on disposal of assets	0	1	12	26
Other income	92	49	219	106
Total revenues and other income	19,386	16,460	54,133	46,080
Costs and expenses:
Cost of revenues (excludes items below)	14,605	12,944	41,913	35,475
Purchases from related parties	148	128	420	359
Inventory market valuation adjustment	0	0	0	(370)
Consumer excise taxes	2,012	1,914	5,751	5,633
Impairment expense	0	0	0	130
Depreciation and amortization	517	507	1,574	1,497
Selling, general and administrative expenses	412	420	1,286	1,199
Other taxes	116	112	339	332
Total costs and expenses	17,810	16,025	51,283	44,255
Income from operations	1,576	435	2,850	1,825
Net interest and other financial income (costs)	(157)	(141)	(465)	(420)
Income before income taxes	1,419	294	2,385	1,405
Provision for income taxes	415	75	706	481
Net income	1,004	219	1,679	924
Less net income (loss) attributable to:
Redeemable noncontrolling interest	16	16	49	25
Noncontrolling interests	85	58	214	(48)
Net income attributable to MPC	$ 903	$ 145	$ 1,416	$ 947
Basic:
Net income attributable to MPC per share	$ 1.79	$ 0.28	$ 2.75	$ 1.79
Weighted average shares outstanding (in shares)	504	527	514	528
Diluted:
Net income attributable to MPC per share	$ 1.77	$ 0.27	$ 2.73	$ 1.78
Weighted average shares outstanding (in shares)	508	530	518	531
Dividends paid (in USD per share)	$ 0.40	$ 0.36	$ 1.12	$ 1

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 1,004	$ 219	$ 1,679	$ 924
Defined benefit postretirement and post-employment plans:
Actuarial changes, net of tax of $2, $0, $9 and $8	4	2	15	14
Prior service costs, net of tax of ($4), ($5), ($12) and ($14)	(7)	(8)	(20)	(23)
Other comprehensive loss	(3)	(6)	(5)	(9)
Comprehensive income	1,001	213	1,674	915
Less comprehensive income (loss) attributable to:
Redeemable noncontrolling interest	16	16	49	25
Noncontrolling interests	85	58	214	(48)
Comprehensive income attributable to MPC	$ 900	$ 139	$ 1,411	$ 938

Consolidated Statements of Com4

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Actuarial changes, tax	$ 2	$ 0	$ 9	$ 8
Prior service costs, tax	$ (4)	$ (5)	$ (12)	$ (14)

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents (MPLX: $3 and $234, respectively)	$ 2,088	$ 887
Receivables, less allowance for doubtful accounts of $10 and $12 (MPLX: $328 and $304, respectively)	3,900	3,617
Inventories (MPLX: $64 and $55, respectively)	5,493	5,656
Other current assets (MPLX: $30 and $33, respectively)	150	241
Total current assets	11,631	10,401
Equity method investments (MPLX: $3,997 and $2,471, respectively)	4,769	3,827
Property, plant and equipment, net (MPLX: $11,922 and $11,408, respectively)	26,036	25,765
Goodwill (MPLX: $2,245 and $2,245, respectively)	3,586	3,587
Other noncurrent assets (MPLX: $485 and $506, respectively)	784	833
Total assets	46,806	44,413
Current liabilities:
Accounts payable (MPLX: $576 and $541, respectively)	6,159	5,593
Payroll and benefits payable (MPLX: $1 and $1, respectively)	459	530
Consumer excise taxes payable (MPLX: $2 and $3, respectively)	371	464
Accrued taxes (MPLX: $42 and $35, respectively)	361	153
Debt due within one year (MPLX: $1 and $1, respectively)	29	28
Other current liabilities (MPLX: $107 and $81, respectively)	268	378
Total current liabilities	7,647	7,146
Long-term debt (MPLX: $6,848 and $4,422, respectively)	12,753	10,544
Deferred income taxes (MPLX: $7 and $6, respectively)	3,935	3,861
Defined benefit postretirement plan obligations	1,029	1,055
Deferred credits and other liabilities (MPLX: $209 and $189, respectively)	640	604
Total liabilities	26,004	23,210
Commitments and contingencies (see Note 21)
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 – 733 million and 731 million shares (par value 0.01 per share, 1 billion shares authorized)	7	7
Held in treasury, at cost – 235 million and 203 million shares	(9,118)	(7,482)
Additional paid-in capital	11,236	11,060
Retained earnings	11,044	10,206
Accumulated other comprehensive loss	(239)	(234)
Total MPC stockholders’ equity	12,930	13,557
Noncontrolling interests	6,872	6,646
Total equity	19,802	20,203
Total liabilities, redeemable noncontrolling interest and equity	$ 46,806	$ 44,413

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 10	$ 12
Preferred stock:
Shares issued	0	0
Shares outstanding	0	0
Par value	$ 0.01
Shares authorized	30,000,000
Common stock:
Shares issued	733,000,000	731,000,000
Par value	$ 0.01
Shares authorized	1,000,000,000
Treasury stock	(235,000,000)	(203,000,000)

Consolidated Balance Sheets (MP

Consolidated Balance Sheets (MPLX Parenthetical) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents	$ 2,088	$ 887
Receivables, less allowance for doubtful accounts	3,900	3,617
Inventories	5,493	5,656
Other current assets	150	241
Equity method investments	4,769	3,827
Property, plant and equipment, net	26,036	25,765
Goodwill	3,586	3,587
Other noncurrent assets	784	833
Liabilities
Accounts payable	6,159	5,593
Payroll and benefits payable	459	530
Consumer excise taxes payable	371	464
Accrued taxes	361	153
Debt due within one year	29	28
Other current liabilities	268	378
Total long-term debt due after one year	12,753	10,544
Deferred income taxes (MPLX: $7 and $6, respectively)	3,935	3,861
Defined benefit postretirement plan obligations	1,029	1,055
Deferred credits and other liabilities	640	604
MPLX LP
Assets
Cash and cash equivalents	3	234
Receivables, less allowance for doubtful accounts	328	304
Inventories	64	55
Other current assets	30	33
Equity method investments	3,997	2,471
Property, plant and equipment, net	11,922	11,408
Goodwill	2,245	2,245
Other noncurrent assets	485	506
Liabilities
Accounts payable	576	541
Payroll and benefits payable	1	1
Consumer excise taxes payable	2	3
Accrued taxes	42	35
Debt due within one year	1	1
Other current liabilities	107	81
Total long-term debt due after one year	6,848	4,422
Deferred income taxes (MPLX: $7 and $6, respectively)	7	6
Defined benefit postretirement plan obligations	0	0
Deferred credits and other liabilities	$ 209	$ 189

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating activities:
Net income	$ 1,679	$ 924
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred financing costs and debt discount	46	47
Impairment expense	0	130
Depreciation and amortization	1,574	1,497
Inventory market valuation adjustment	0	(370)
Pension and other postretirement benefits, net	(32)	(21)
Deferred income taxes	57	335
Net gain on disposal of assets	(12)	(26)
(Income) loss from equity method investments	(224)	236
Distributions from equity method investments	252	199
Changes in the fair value of derivative instruments	101	6
Changes in:
Current receivables	(296)	(209)
Inventories	163	71
Current accounts payable and accrued liabilities	654	237
All other, net	(99)	(54)
Net cash provided by operating activities	3,863	3,002
Investing activities:
Additions to property, plant and equipment	(1,928)	(2,147)
Acquisitions, net of cash acquired	(249)	0
Disposal of assets	64	88
Investments – acquisitions, loans and contributions	(730)	(240)
Investments - redemptions, repayments and return of capital	64	20
All other, net	164	62
Net cash used in investing activities	(2,615)	(2,217)
Financing activities:
Commercial paper – issued	300	1,063
Commercial paper - repayments	(300)	(1,063)
Long-term debt – borrowings	2,661	714
Long-term debt – repayments	(470)	(2,112)
Debt issuance costs	(28)	(11)
Issuance of common stock	27	8
Common stock repurchased	(1,622)	(177)
Dividends paid	(578)	(529)
Issuance of MPLX LP common units	473	499
Issuance of MPLX LP redeemable preferred units	0	984
Distributions to noncontrolling interests	(505)	(389)
Contributions from noncontrolling interests	128	4
Contingent consideration payment	(89)	(164)
All other, net	(44)	(30)
Net cash used in financing activities	(47)	(1,203)
Net increase (decrease) in cash and cash equivalents	1,201	(418)
Cash and cash equivalents at beginning of period	887	1,127
Cash and cash equivalents at end of period	$ 2,088	$ 709

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, 2015	$ 19,675	$ 7	$ (7,275)	$ 11,071	$ 9,752	$ (318)	$ 6,438
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	899				947		(48)
Dividends declared	(530)				(530)
Distributions to noncontrolling interests	(380)						(380)
Contributions from noncontrolling interests	4						4
Other comprehensive loss	(9)					(9)
Shares repurchased	(177)		(177)
Shares returned - stock based compensation			(7)
Shares issued - stock based compensation				8
Net shares issued - stock based compensation	1
Stock-based compensation	45			39			6
Impact from equity transactions of MPLX LP	429			(113)			542
Ending balance at Sep. 30, 2016	19,957	7	(7,459)	11,005	10,169	(327)	6,562
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 (loss)	1,630				1,416		214
Dividends declared	(578)				(578)
Distributions to noncontrolling interests	(456)						(456)
Contributions from noncontrolling interests	128						128
Other comprehensive loss	(5)					(5)
Shares repurchased	(1,622)		(1,622)
Shares returned - stock based compensation			(14)
Shares issued - stock based compensation				27
Net shares issued - stock based compensation	13
Stock-based compensation	42			37			5
Impact from equity transactions of MPLX LP	447			112			335
Ending balance at Sep. 30, 2017	$ 19,802	$ 7	$ (9,118)	$ 11,236	$ 11,044	$ (239)	$ 6,872

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, 2015		729
Number of shares issued - stock-based compensation		2
Number of common shares issued (ending balance) at Sep. 30, 2016		731
Number of shares held in treasury (beginning balance) at Dec. 31, 2015			(198)
Number of shares repurchased	(4)		(4)
Number of shares returned - stock-based compensation			(1)
Number of shares held in treasury (ending balance) at Sep. 30, 2016			(203)
Number of common shares issued (beginning balance) at Dec. 31, 2016	731	731
Number of shares issued - stock-based compensation		2
Number of common shares issued (ending balance) at Sep. 30, 2017	733	733
Number of shares held in treasury (beginning balance) at Dec. 31, 2016	(203)		(203)
Number of shares repurchased	(31)		(31)
Number of shares returned - stock-based compensation			(1)
Number of shares held in treasury (ending balance) at Sep. 30, 2017	(235)		(235)

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interest - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Temporary Equity [Abstract]
Beginning balance	$ 1,000	$ 0
Net income (loss) attributable to redeemable noncontrolling interest	49	25
Distributions to noncontrolling interests	(49)	(9)
Issuance of MPLX LP redeemable preferred units		984
Ending balance	$ 1,000	$ 1,000

Description of the Business and

Description of the Business and Basis of Presentation	9 Months Ended
	Sep. 30, 2017
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 9 for additional information about our operations. Basis of Presentation— All significant intercompany transactions and accounts have been eliminated. These interim consolidated financial statements are unaudited; however, in the opinion of our management, these statements reflect all adjustments necessary for a fair statement of the results for the periods reported. All such adjustments are of a normal, recurring nature unless otherwise disclosed. These interim consolidated financial statements, including the notes, have been prepared in accordance with the rules of the SEC applicable to interim period financial statements and do not include all of the information and disclosures required by 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, 2016 . The results of operations for the three and nine months ended September 30, 2017 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. In the first quarter of 2017, we revised our segment reporting in connection with the contribution of certain terminal, pipeline and storage assets to MPLX. See Note 3 for additional information. The operating results for these assets are now reported in our Midstream segment. Previously, they were reported as part of our Refining & Marketing segment. Comparable prior period information has been recast to reflect our revised presentation. The results for the pipeline and storage assets were recast effective January 1, 2015, and the results for the terminal assets were recast effective April 1, 2016. Prior to these dates, these assets were not considered businesses for accounting purposes and, therefore, there are no financial results from which to recast segment results. Additionally, the MPLX asset and liability balances as of December 31, 2016, reported in parentheses on our consolidated balance sheets, have also been recast to reflect this transaction. See Note 9 and Note 13 for additional information.

Accounting Standards

Accounting Standards	9 Months Ended
	Sep. 30, 2017
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recently Adopted	Accounting Standards Recently Adopted In October 2016, the FASB issued an accounting standards update to amend the consolidation guidance issued in February 2015 to require that a decision maker consider, in the determination of the primary beneficiary, its indirect interest in a VIE held by a related party that is under common control on a proportionate basis only. The change was effective for our financial statements for fiscal years beginning after December 15, 2016, and interim periods within those fiscal years. We were required to apply the standard retrospective to January 1, 2016, the date on which we adopted the consolidation guidance issued in February 2015. Adoption of this accounting standards update in the first quarter of 2017 did not have an impact on our consolidated financial statements. In March 2016, the FASB issued an accounting standards update to simplify some provisions in stock compensation accounting. The areas for simplification involve the accounting for share-based payment transactions, including income tax consequences, classifications of awards as either equity or liabilities and classification within the statement of cash flows. The changes were effective for fiscal years beginning after December 15, 2016, and interim periods within those fiscal years. Adoption of this accounting standards update in the first quarter of 2017 did not have a material impact on our consolidated financial statements. In March 2016, the FASB issued an accounting standards update eliminating the requirement that an investor retrospectively apply equity method accounting when an investment that it had accounted for by another method initially qualifies for the equity method. This change was effective for fiscal years beginning after December 15, 2016, and interim periods within those fiscal years. Adoption of this accounting standards update in the first quarter of 2017 did not have an impact on our consolidated financial statements.
Not Yet Adopted	Not Yet Adopted In August 2017, the FASB issued 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. In May 2017, the FASB issued an accounting standards update to provide guidance about when changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. An entity should account for the effects of a modification unless the fair value, vesting conditions and balance sheet classification of the modified award is the same as the original award immediately before the original award is modified. We will adopt this accounting standards update January 1, 2018. This update should be applied prospectively to an award modified on or after the adoption date. We do not expect the application of this accounting standards update to have a material impact on our consolidated financial statements. In March 2017, the FASB issued an accounting standards update requiring that the service cost component of pension and postretirement benefit costs be presented in the same line item as other current employee compensation costs and other components of those benefit costs be presented separately from the service cost component and outside a subtotal of income from operations, if presented. The update also requires that only the service cost component of pension and postretirement benefit cost is eligible for capitalization. We will adopt this accounting standards update January 1, 2018. Application is retrospective for the presentation of the components of these benefit costs and prospective for the capitalization of only service costs. We do not expect the application of this accounting standards update to have a material impact on our consolidated financial statements. In February 2017, the FASB issued an accounting standards update addressing the derecognition of nonfinancial assets. The guidance defines in substance nonfinancial assets, and states that the derecognition of business activities should be evaluated under the consolidation guidance, with limited exceptions related to conveyances of oil and gas mineral rights or contracts with customers. The standard eliminates the previous exclusion for businesses that are in-substance real estate, and eliminates some differences based on whether a transferred set is that of assets or a business and whether the transfer is to a joint venture. The standard must be implemented in conjunction with the implementation date of the revenue recognition accounting standards update, which we will implement January 1, 2018. We plan to adopt the new standard using the modified retrospective method and do not expect the application of this accounting standards update to have a material impact on our consolidated financial statements. 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. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. In January 2017, the FASB issued an accounting standards update to clarify the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The standard is intended to narrow the definition of a business by specifying the minimum inputs and processes and by narrowing the definition of outputs. The change is effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. The guidance will be applied prospectively and early adoption is permitted for certain transactions. In November 2016, the FASB issued an accounting standards update requiring that the statement of cash flows explain the change during the period in the total of cash, cash equivalents and amounts generally described as restricted cash or restricted cash equivalents. The change is effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years, with early adoption permitted. Retrospective application is required. Application of this accounting standards update will not have a material impact on our statements of cash flows. In October 2016, the FASB issued an accounting standards update that requires recognition of the income tax consequences of intra-entity transfers of assets other than inventory when the transfer occurs. The change is effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years, with early adoption permitted. The amendments in this accounting standards update should be applied on a modified retrospective basis through a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. We do not expect application of this accounting standards update to have a material impact on our consolidated financial statements. In August 2016, the FASB issued an accounting standards update related to the classification of certain cash flows. The accounting standards update provides specific guidance on eight cash flow classification issues, including debt prepayment or debt extinguishment costs, contingent consideration payments made after a business combination and distributions received from equity method investees, to reduce diversity in practice. The change is effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years, with early adoption permitted. Retrospective application is required. We do not expect application of this accounting standards update to have a material impact on our statements of cash flows. 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. 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 are currently evaluating 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 along with necessary system implementations. We do not plan to early adopt the standard. We believe the impact will be material on the consolidated financial statements as all leases will be recognized as a right of use asset and lease obligation. Based on results of our evaluation process to date, we also believe the impact on our existing processes, controls and information systems may be material. In January 2016, the FASB issued an accounting standards update requiring unconsolidated equity investments, not accounted for under the equity method, to be measured at fair value with changes in fair value recognized in net income. The accounting standards update also requires the use of the exit price notion when measuring the fair value of financial instruments for disclosure purposes and the separate presentation of financial assets and liabilities by measurement category and form on the balance sheet and accompanying notes. The accounting standards update eliminates the requirement to disclose the methods and assumptions used in estimating the fair value of financial instruments measured at amortized cost. Lastly, the accounting standards update requires separate presentation in other comprehensive income of the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when electing to measure the liability at fair value in accordance with the fair value option for financial instruments. The changes are effective for fiscal years and interim periods within those fiscal years beginning after December 15, 2017. Early adoption is permitted only for the guidance regarding presentation of a liability’s credit risk. We do not expect application of this accounting standards update to have a material impact on our consolidated financial statements. In May 2014, the FASB issued an accounting standards update for revenue recognition for contracts with customers. The guidance in the accounting standards update states that revenue is recognized when a customer obtains control of a good or service. Recognition of the revenue will involve a multiple step approach including identifying the contract, identifying the separate performance obligations, determining the transaction price, allocating the price to the performance obligations and recognizing the revenue as the obligations are satisfied. Additional disclosures will be required to provide adequate information to understand the nature, amount, timing and uncertainty of reported revenues and revenues expected to be recognized. We will adopt the standard January 1, 2018, using the modified retrospective method, which will result in a cumulative effect adjustment as of the date of adoption. We are currently evaluating the impact of this standard on our financial statements and disclosures, internal controls and accounting policies. Based on the results to date, we have reached tentative conclusions for most contract types and do not believe revenue recognition patterns will change materially. We do expect certain contracts in our Midstream segment to be presented on a gross revenue recognition basis as a result of implementation. In addition, we expect to elect to change our presentation of consumer excise taxes incurred concurrently with revenue producing transactions from gross to net upon the adoption of this accounting standards update. Based on the results of our evaluation process to date, we do not expect our existing revenue recognition processes, controls and information systems to materially change.

MPLX LP

MPLX LP	9 Months Ended
	Sep. 30, 2017
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. On December 4, 2015, MPLX and MarkWest Energy Partners, L.P. (“MarkWest”) completed a merger, whereby MarkWest became a wholly-owned subsidiary of MPLX (the “MarkWest Merger”). MarkWest’s operations include: natural gas gathering, processing and transportation; and NGL gathering, transportation, fractionation, storage and marketing. MPLX owns or has an interest in a network of private and common carrier crude oil and product pipeline systems and associated storage assets in the Midwest and Gulf Coast regions of the United States, a butane cavern in Neal, West Virginia, and NGL storage caverns in Woodhaven, Michigan. MPLX owns an inland marine business, comprised of tow boats and barges, which transport crude oil and refined products principally for MPC in the Midwest and Gulf Coast regions of the United States. MPLX also owns a light-product terminal business, which provides terminalling services principally for MPC in the Midwest and Southeast regions of the United States. See Note 4 for information on MPLX’s acquisition of the Ozark pipeline, its investment in the Bakken Pipeline system and the formation of a joint venture with Antero Midstream Partners LP (“Antero Midstream”) during the first quarter of 2017. As of September 30, 2017 , we owned a 30.4 percent interest in MPLX, including a two percent general partner interest. MPLX is a VIE because the limited partners of MPLX do not have substantive kick-out or substantive participating rights over the general partner. We are the primary beneficiary of MPLX because in addition to significant economic interest, we also have the power, through our 100 percent ownership of the general partner, to control the decisions that most significantly impact MPLX. We therefore consolidate MPLX and record a noncontrolling interest for the 69.6 percent interest owned by the public. The components of our noncontrolling interest consist of equity-based noncontrolling interest and redeemable noncontrolling interest. The redeemable noncontrolling interest relates to MPLX’s preferred units, discussed below. 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 21 for more information. Reorganization Transactions On September 1, 2016, MPC, MPLX and various affiliates initiated a series of reorganization transactions in order to simplify MPLX’s ownership structure and its financial and tax reporting. In connection with these transactions, MPC contributed $225 million to MPLX and all of the issued and outstanding MPLX Class A Units, all of which were held by MarkWest Hydrocarbon L.L.C. (“MarkWest Hydrocarbon”), a subsidiary of MPLX, were exchanged for newly issued common units representing limited partner interests in MPLX. The simple average of the NYSE closing price of MPLX common units for the 10 trading days preceding September 1, 2016 was used for purposes of these transactions. As a result of these transactions, MPC increased its ownership interest in MPLX by 7 million MPLX common units, or approximately 1 percent . Private Placement of Preferred Units On May 13, 2016, MPLX completed the private placement of approximately 30.8 million 6.5 percent Series A Convertible Preferred Units (the “MPLX Preferred Units”) for a cash price of $32.50 per unit. The aggregate net proceeds of approximately $984 million from the sale of the MPLX Preferred Units was used by MPLX for capital expenditures, repayment of debt and general partnership purposes. The MPLX Preferred Units rank senior to all MPLX common units with respect to distributions and rights upon liquidation. The holders of the MPLX Preferred Units are entitled to receive quarterly distributions equal to $0.528125 per unit commencing for the quarter ended June 30, 2016, with a prorated amount from the date of issuance. Following the second anniversary of the issuance of the MPLX Preferred Units, the holders of the MPLX Preferred Units will receive as a distribution the greater of $0.528125 per unit or the amount of per unit distributions paid to holders of MPLX common units. The MPLX Preferred Units are convertible into MPLX common units on a one for one basis after three years, at the purchasers’ option, and after four years at MPLX’s option, subject to certain conditions. The MPLX Preferred Units are considered redeemable securities due to the existence of redemption provisions upon a deemed liquidation event which is considered outside MPLX’s control. Therefore, they are presented as temporary equity in the mezzanine section of the consolidated balance sheets. We have recorded the MPLX Preferred Units at their issuance date fair value, net of issuance costs. Since the MPLX Preferred Units are not currently redeemable and not probable of becoming redeemable in the future, adjustment to the initial carrying amount is not necessary and would only be required if it becomes probable that the security would become redeemable. Dropdowns to MPLX On September 1, 2017, we contributed our joint-interest ownership in certain pipelines and storage facilities to MPLX in exchange for total consideration of $1.05 billion . This consideration consisted of MPLX equity and $420 million in cash. We received approximately 19 million MPLX common units and 378 thousand general partner units from MPLX, which was determined by dividing $630 million by the simple average of the 10 day trading volume weighted average NYSE price of an MPLX common unit for the 10 trading days ending at market close on August 31, 2017, pursuant to a Membership Interests and Shares Contributions Agreement. We also agreed to waive 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 total consideration of $2.0 billion . This consideration consisted of MPLX equity and $1.5 billion in cash. We received approximately 13 million MPLX common units and 264 thousand general partner units from MPLX, which was determined by dividing $504 million by the simple average of the volume weighted average NYSE price of an MPLX common unit for the 10 trading days preceding February 28, 2017, pursuant to a Membership Interests Contributions Agreement. 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. On March 31, 2016, we contributed our inland marine business to MPLX in exchange for 23 million MPLX common units and 460 thousand general partner units. The number of units we received from MPLX was determined by dividing $600 million by the simple average of the volume weighted average NYSE price of an MPLX common unit for the 10 trading days preceding March 14, 2016, pursuant to a Membership Interests Contribution Agreement. We also agreed to waive first-quarter 2016 common unit distributions, IDRs and general partner distributions with respect to the common units issued in this transaction. The contribution of our inland marine business was accounted for as a transaction between entities under common control and we did not record a gain or loss. Public Offerings On February 10, 2017, MPLX completed a public offering of $1.25 billion aggregate principal amount of 4.125% unsecured senior notes due March 2027 and $1.0 billion aggregate principal amount of 5.200% unsecured senior notes due March 2047. MPLX used the net proceeds from this offering to fund the $1.5 billion cash portion of the consideration MPLX paid MPC for the dropdown of assets on March 1, 2017, as well as for general partnership purposes. See Note 16 for more information. ATM Program On August 4, 2016, MPLX entered into a Second Amended and Restated Distribution Agreement (the “Distribution Agreement”) providing for the continuous issuance of common units, in amounts, at prices and on terms to be determined by market conditions and other factors at the time of any offerings (such continuous offering program, or at-the-market program, referred to as the “ATM Program”). MPLX expects to use the net proceeds from sales under the ATM Program for general partnership purposes including repayment of debt and funding for acquisitions, working capital requirements and capital expenditures. During the nine months ended September 30, 2017 , MPLX issued an aggregate of 14 million MPLX common units under the ATM Program, generating net proceeds of approximately $473 million . As of September 30, 2017 , $1.74 billion of MPLX common units remain available for issuance through the ATM Program under the Distribution Agreement. Noncontrolling Interest Changes in MPC’s equity and the offsetting changes to noncontrolling interest resulting from changes in MPC’s and the noncontrolling interest’s ownership interests in MPLX were as follows: Nine Months Ended (In millions) 2017 2016 Transfers (to) from noncontrolling interest Increase (decrease) in MPC's additional paid in capital for the issuance of MPLX LP common units to the public $ 25 $ (43 ) Increase in MPC's additional paid in capital for the issuance of MPLX LP common units and general partner units to MPC 113 — Net transfers (to) from noncontrolling interests 138 (43 ) Tax impact (26 ) (70 ) Change in MPC's additional paid-in capital, net of tax $ 112 $ (113 ) Agreements We have various long-term, fee-based transportation, terminal and storage services agreements with MPLX. Under these agreements, MPLX provides transportation, terminal and storage services to us, and we commit to provide MPLX with minimum quarterly throughput volumes on crude oil and refined products systems and minimum storage volumes of crude oil, refined products and butane. We also have agreements with MPLX that establish fees for operational and management services provided between us and MPLX and for executive management services and certain general and administrative services provided by us to MPLX. These transactions are eliminated in consolidation.

Acquisitions and Investments

Acquisitions and Investments	9 Months Ended
	Sep. 30, 2017
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. The amounts of revenue and income from operations associated with the acquisition included in our consolidated statements of income, since the March 1, 2017 acquisition date, are as follows: Three Months Ended September 30, Seven Months Ended September 30, (In millions) 2017 2017 Sales and other operating revenues (including consumer excise taxes) $ 19 $ 45 Income from operations 6 17 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. Formation of Travel Plaza Joint Venture In the fourth quarter of 2016, Speedway and Pilot Flying J finalized the formation of a joint venture consisting of travel plazas, primarily in the Southeast United States. The new entity, PFJ Southeast LLC (“PFJ Southeast”), originally consisted of 41 existing locations contributed by Speedway and 82 locations contributed by Pilot Flying J, all of which carry either the Pilot or Flying J brand and are operated by Pilot Flying J. We did not recognize a gain on the $273 million non-cash contribution of our travel plazas to the joint venture since the contribution was that of in-substance real estate. Our non-cash contribution consisted of $203 million of property, plant and equipment, $62 million of goodwill and $8 million of inventory. Marine Investments We currently have indirect ownership interests in two ocean vessel joint ventures with Crowley Maritime Corporation (“Crowley”), which were established to own and operate Jones Act vessels in petroleum product service. We have invested a total of $189 million in these two ventures as described further below. In September 2015, we acquired a 50 percent ownership interest in a joint venture, Crowley Ocean Partners LLC (“Crowley Ocean Partners”), with Crowley. The joint venture owns and operates four new Jones Act product tankers, three of which are leased to MPC. Two of the vessels were delivered in 2015 and the remaining two were delivered in 2016. We have contributed a total of $141 million for the four vessels. In May 2016, MPC and Crowley formed a new ocean vessel joint venture, Crowley Coastal Partners LLC (“Crowley Coastal Partners”), in which MPC has a 50 percent ownership interest. MPC and Crowley each contributed their 50 percent ownership in Crowley Ocean Partners, discussed above, into Crowley Coastal Partners. In addition, we contributed $48 million in cash and Crowley contributed its 100 percent ownership interest in Crowley Blue Water Partners LLC (“Crowley Blue Water Partners”) to Crowley Coastal Partners. Crowley Blue Water Partners is an entity that owns and operates three 750 Series ATB vessels that are leased to MPC. We account for our 50 percent interest in Crowley Coastal Partners as part of our Midstream segment using the equity method of accounting. See Note 5 for information on Crowley Coastal Partners as a VIE and Note 21 for information on our conditional guarantee of the indebtedness of Crowley Ocean Partners and Crowley Blue Water Partners. Investment in Pipeline Company On February 15, 2017, MPLX closed on the previously announced transaction to acquire 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 currently expected to deliver in excess of 470 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. In connection with this investment by MPLX, we have agreed to waive our right to receive IDRs of approximately $1.6 million per quarter for twelve consecutive quarters beginning with distributions declared by MPLX in the first quarter of 2017 and paid to us in the second quarter, which has been prorated to $0.8 million from the acquisition date. We account for the investment in MarEn Bakken as part of our Midstream segment using the equity method of accounting. In connection with closing the transaction with ETP and SXL and the previous decision to indefinitely suspend the Sandpiper project, Enbridge Energy Partners canceled MPC’s transportation services agreement with respect to the Sandpiper pipeline and released MPC from paying any termination fee per that agreement. Formation of Gathering and Processing Joint Venture Effective January 1, 2017, MarkWest 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. MarkWest has a 50 percent ownership interest in Sherwood Midstream. In connection with this transaction, MarkWest 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, MarkWest 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, MarkWest 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 MarkWest. MarkWest 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. MarkWest 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, MarkWest only recognized a gain for the portion attributable to Antero Midstream’s indirect interest of approximately $2 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 5 for additional information related to the investments in Sherwood Midstream, Ohio Fractionation and Sherwood Midstream Holdings.

Variable Interest Entities

Variable Interest Entities	9 Months Ended
	Sep. 30, 2017
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Variable Interest Entities	Variable Interest Entities In addition to MPLX, as described in Note 3 , 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 September 30, 2017 was $493 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 September 30, 2017 , 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 September 30, 2017 was $2.2 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 September 30, 2017 , 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 4 , MarkWest 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 September 30, 2017 , MarkWest 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. MarkWest 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 September 30, 2017 was $220 million . Ohio Fractionation As described in Note 4 , MarkWest 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. MarkWest 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 4 , MarkWest 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 MarkWest. MarkWest 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 September 30, 2017 was $163 million .

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2017
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. • Explorer Pipeline Company (“Explorer”), in which we have a 25 percent interest. Explorer owns and operates a refined products pipeline. • 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 86 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 Nine Months Ended (In millions) 2017 2016 2017 2016 PFJ Southeast $ 155 $ — $ 451 $ — Other equity method investees 2 2 7 5 Total $ 157 $ 2 $ 458 $ 5 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 Nine Months Ended (In millions) 2017 2016 2017 2016 MarkWest Utica EMG $ 5 $ 5 $ 13 $ 12 Ohio Gathering 4 5 12 12 Other equity method investees 4 2 14 7 Total $ 13 $ 12 $ 39 $ 31 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 Nine Months Ended (In millions) 2017 2016 2017 2016 Crowley Blue Water Partners $ 16 $ 16 $ 44 $ 22 Crowley Ocean Partners 20 15 59 32 Explorer 7 4 7 12 Illinois Extension Pipeline 26 27 75 82 LOCAP 6 6 17 18 LOOP 14 14 53 42 TAAE 22 9 53 29 TACE 9 10 34 39 TAME 20 23 58 67 Other equity method investees 8 4 20 16 Total $ 148 $ 128 $ 420 $ 359 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 Explorer consist primarily of refined product transportation costs. Related party purchases from Illinois Extension Pipeline, LOCAP, LOOP and other equity method investees consist primarily of crude oil transportation costs. Related party purchases from 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) September 30, December 31, MarkWest Utica EMG $ 2 $ 2 Ohio Gathering 2 2 PFJ Southeast 32 40 Other equity method investees 4 1 Total $ 40 $ 45 The long-term receivable, which is included in “Other noncurrent assets” on the accompanying consolidated balance sheet, was $1 million at September 30, 2017 and $1 million at December 31, 2016 . Payables to related parties, which are included in “Accounts payable” on the accompanying consolidated balance sheets, were as follows: (In millions) September 30, December 31, Illinois Extension Pipeline $ 9 $ 9 LOCAP 2 2 LOOP 5 6 MarkWest Utica EMG 30 24 TAAE 2 2 TACE 1 4 TAME 2 4 Other equity method investees 13 2 Total $ 64 $ 53

Income per Common Share

Income per Common Share	9 Months Ended
	Sep. 30, 2017
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 Nine Months Ended (In millions, except per share data) 2017 2016 2017 2016 Basic earnings per share: Allocation of earnings: Net income attributable to MPC $ 903 $ 145 $ 1,416 $ 947 Income allocated to participating securities — — 1 1 Income available to common stockholders – basic $ 903 $ 145 $ 1,415 $ 946 Weighted average common shares outstanding 504 527 514 528 Basic earnings per share $ 1.79 $ 0.28 $ 2.75 $ 1.79 Diluted earnings per share: Allocation of earnings: Net income attributable to MPC $ 903 $ 145 $ 1,416 $ 947 Income allocated to participating securities — — 1 1 Income available to common stockholders – diluted $ 903 $ 145 $ 1,415 $ 946 Weighted average common shares outstanding 504 527 514 528 Effect of dilutive securities 4 3 4 3 Weighted average common shares, including dilutive effect 508 530 518 531 Diluted earnings per share $ 1.77 $ 0.27 $ 2.73 $ 1.78 The following table summarizes the shares that were anti-dilutive and, therefore, were excluded from the diluted share calculation. Three Months Ended Nine Months Ended (In millions) 2017 2016 2017 2016 Shares issued under stock-based compensation plans 1 3 1 3

Equity

Equity	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Equity	Equity On May 31, 2017, our board of directors approved an additional $3.0 billion share repurchase authorization. This authorization is in addition to its previous authorization, both of which have no expiration date. As of September 30, 2017 , we had $3.94 billion of remaining share repurchase authorization 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 affected through Rule 10b5-1 plans. The timing and amount of future repurchases, if any, will depend upon several factors, including market and business conditions, and such repurchases may be discontinued at any time. Total share repurchases were as follows for the three and nine months ended September 30, 2017 and 2016 : Three Months Ended Nine Months Ended (In millions, except per share data) 2017 2016 2017 2016 Number of shares repurchased 8 1 31 4 Cash paid for shares repurchased $ 452 $ 51 $ 1,622 $ 177 Effective average cost per delivered share $ 53.85 $ 42.76 $ 52.16 $ 41.14 As of September 30, 2017 , we had agreements to acquire 985,400 common shares for $55 million , which were settled in early October 2017.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2017
Segment Reporting [Abstract]
Segment Information	Segment Information In the first quarter of 2017, we revised our segment reporting in connection with the contribution of certain terminal, pipeline and storage assets to MPLX. The operating results for these assets are now reported in our Midstream segment. Previously, they were reported as part of our Refining & Marketing segment. Comparable prior period information has been recast to reflect our revised presentation. The results for the pipeline and storage assets were recast effective January 1, 2015, and the results for the terminal assets were recast effective April 1, 2016. Prior to these dates, these assets were not considered businesses and, therefore, there are no financial results from which to recast segment results. 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 seven refineries in the Gulf Coast and Midwest regions of the United States, purchases refined products and ethanol for resale and distributes refined products through various means, including pipeline and marine transportation, terminal and storage 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 segment and to independent entrepreneurs who operate Marathon ® retail outlets. • Speedway – sells transportation fuels and convenience merchandise in retail markets in the Midwest, East Coast and Southeast regions of the United States. • Midstream – includes the operations of MPLX and certain other related operations. The Midstream segment gathers, processes and transports natural gas; gathers, transports, fractionates, stores and markets NGLs; and transports and stores crude oil and refined products principally for the Refining & Marketing segment. 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 September 30, 2017 Revenues: Third party $ 13,573 $ 4,895 $ 585 $ 19,053 Intersegment (a) 2,904 1 369 3,274 Related party 155 2 — 157 Segment revenues $ 16,632 $ 4,898 $ 954 $ 22,484 Segment income from operations (b) $ 1,097 $ 209 $ 355 $ 1,661 Income from equity method investments 6 20 57 83 Depreciation and amortization (c) 266 68 169 503 Capital expenditures and investments (d) 198 108 453 759 (In millions) Refining & Marketing Speedway Midstream Total Three Months Ended September 30, 2016 Revenues: Third party $ 11,284 $ 4,848 $ 484 $ 16,616 Intersegment (a) 2,798 1 346 3,145 Related party 2 — — 2 Segment revenues $ 14,084 $ 4,849 $ 830 $ 19,763 Segment income from operations (b) $ 252 $ 209 $ 310 $ 771 Income from equity method investments (c) 8 — 51 59 Depreciation and amortization (c) 267 71 155 493 Capital expenditures and investments (d) 251 71 410 732 (In millions) Refining & Marketing Speedway Midstream Total Nine Months Ended September 30, 2017 Revenues: Third party $ 37,485 $ 14,070 $ 1,665 $ 53,220 Intersegment (a) 8,302 3 1,076 9,381 Related party 452 6 — 458 Segment revenues $ 46,239 $ 14,079 $ 2,741 $ 63,059 Segment income from operations (b) $ 1,589 $ 583 $ 996 $ 3,168 Income from equity method investments 10 54 139 203 Depreciation and amortization (c) 805 197 528 1,530 Capital expenditures and investments (d)(e) 570 221 2,017 2,808 (In millions) Refining & Marketing Speedway Midstream Total Nine Months Ended September 30, 2016 Revenues: Third party $ 31,192 $ 13,663 $ 1,324 $ 46,179 Intersegment (a) 7,872 2 911 8,785 Related party 5 — — 5 Segment revenues $ 39,069 $ 13,665 $ 2,235 $ 54,969 Segment income from operations (b)(f) $ 1,191 $ 569 $ 752 $ 2,512 Income from equity method investments (c) 10 — 110 120 Depreciation and amortization (c) 801 203 448 1,452 Capital expenditures and investments (d) 756 191 1,179 2,126 (a) Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties. (b) Corporate overhead expenses attributable to MPLX are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments. (c) Differences between segment totals and MPC totals represent amounts related to unallocated items and are included in “Items not allocated to segments” in the reconciliation below. (d) Capital expenditures include changes in capital accruals, acquisitions (including any goodwill) and investments in affiliates. (e) 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 nine months ended September 30, 2017 . (f) The Refining & Marketing and Speedway segments include inventory LCM benefits of $345 million and $25 million , respectively, for the nine months ended September 30, 2016 . The following reconciles segment income from operations to income before income taxes as reported in the consolidated statements of income: Three Months Ended Nine Months Ended (In millions) 2017 2016 2017 2016 Segment income from operations $ 1,661 $ 771 $ 3,168 $ 2,512 Items not allocated to segments: Corporate and other unallocated items (a) (86 ) (65 ) (251 ) (194 ) Pension settlement expenses (1 ) (4 ) (2 ) (7 ) Litigation (b) — — (86 ) — Impairments (c) 2 (267 ) 21 (486 ) Net interest and other financial income (costs) (157 ) (141 ) (465 ) (420 ) Income before income taxes $ 1,419 $ 294 $ 2,385 $ 1,405 (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. (b) See Note 21 for further information on litigation matters. (c) 2017 includes MPC’s share of gains related to the sale of assets remaining from the Sandpiper pipeline project. 2016 relates to impairments of goodwill and equity method investments. The following reconciles segment capital expenditures and investments to total capital expenditures: Three Months Ended Nine Months Ended (In millions) 2017 2016 2017 2016 Segment capital expenditures and investments $ 759 $ 732 $ 2,808 $ 2,126 Less investments in equity method investees (a) 53 69 730 383 Plus items not allocated to segments: Corporate and Other 19 14 53 59 Capitalized interest 13 15 39 47 Total capital expenditures (b) $ 738 $ 692 $ 2,170 $ 1,849 (a) The nine months ended September 30, 2017 includes an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system. The nine months ended September 30, 2016 includes an adjustment of $143 million to the fair value of equity method investments acquired in connection with the MarkWest Merger. (b) Capital expenditures include changes in capital accruals. See Note 17 for a reconciliation of total capital expenditures to additions to property, plant and equipment as reported in the consolidated statements of cash flows.

Other Items

Other Items	9 Months Ended
	Sep. 30, 2017
Other Income and Expenses [Abstract]
Other Items	Other Items Net interest and other financial income (costs) was: Three Months Ended Nine Months Ended (In millions) 2017 2016 2017 2016 Interest income $ 7 $ 3 $ 16 $ 5 Interest expense (172 ) (153 ) (508 ) (455 ) Interest capitalized 14 15 47 47 Other financial costs (6 ) (6 ) (20 ) (17 ) Net interest and other financial income (costs) $ (157 ) $ (141 ) $ (465 ) $ (420 )

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The combined federal, state and foreign income tax rate was 29 percent and 26 percent for the three months ended September 30, 2017 and 2016 , respectively, and 30 percent and 34 percent for the nine months ended September 30, 2017 and 2016 , respectively. The effective tax rate for the three and nine months ended September 30, 2017 was less than the U.S. statutory rate of 35 percent primarily due to certain permanent tax differences related to net income attributable to noncontrolling interests, the domestic manufacturing deduction and equity compensation offset by state and local tax expense. The effective tax rate for the three months ended September 30, 2016 varies from the U.S. statutory rate of 35 percent primarily due to the effects of a lower forecasted annual effective tax rate as compared to the forecasted rate used for the first six months of 2016. The effective tax rate for the nine months ended September 30, 2016 is slightly less than the U.S. statutory rate of 35 percent primarily due to certain permanent tax differences related to the net income attributable to noncontrolling interests (including their proportional share of the goodwill impairment charge recorded by MPLX), the domestic manufacturing deduction and 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 September 30, 2017 , 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 partnership transactions. Marathon Oil intends to file 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 the Marathon Oil IRS dispute discussed above. We intend to file a U.S. Tax Court petition in the fourth quarter of 2017 for tax years 2011-2014 to dispute these corollary adjustments. 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 21 for indemnification information.

Inventories

Inventories	9 Months Ended
	Sep. 30, 2017
Inventory Disclosure [Abstract]
Inventories	Inventories (In millions) September 30, December 31, Crude oil and refinery feedstocks $ 2,147 $ 2,208 Refined products 2,706 2,810 Materials and supplies 486 485 Merchandise 154 153 Total $ 5,493 $ 5,656 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 liquidations of LIFO inventories for the nine months ended September 30, 2017 .

Property, Plant and Equipment

Property, Plant and Equipment	9 Months Ended
	Sep. 30, 2017
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment (In millions) September 30, December 31, 2016 (a) Refining & Marketing $ 19,174 $ 18,590 Speedway 5,233 5,078 Midstream 14,489 13,521 Corporate and Other 822 817 Total 39,718 38,006 Less accumulated depreciation 13,682 12,241 Property, plant and equipment, net $ 26,036 $ 25,765 (a) Prior period balances have been recast in connection with the March 1, 2017 contribution of assets to MPLX. See Note 1 for additional information.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2017
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 September 30, 2017 and December 31, 2016 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. September 30, 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 $ 257 $ — $ — $ (257 ) $ — $ 22 Other assets 3 — — N/A 3 — Total assets at fair value $ 260 $ — $ — $ (257 ) $ 3 $ 22 Commodity derivative instruments, liabilities (c) $ 296 $ — $ 5 $ (296 ) $ 5 $ — Embedded derivatives in commodity contracts (c) — — 52 — 52 — Total liabilities at fair value $ 296 $ — $ 57 $ (296 ) $ 57 $ — December 31, 2016 Fair Value Hierarchy (In millions) Level 1 Level 2 Level 3 Netting and Collateral (a) Net Carrying Value on Balance Sheet (b) Collateral Pledged Not Offset Commodity derivative instruments, assets $ 688 $ — $ — $ (688 ) $ — $ 126 Other assets 2 — — N/A 2 — Total assets at fair value $ 690 $ — $ — $ (688 ) $ 2 $ 126 Commodity derivative instruments, liabilities $ 712 $ — $ 6 $ (712 ) $ 6 $ — Embedded derivatives in commodity contracts (c) — — 54 — 54 — Contingent consideration, liability (d) — — 130 N/A 130 — Total liabilities at fair value $ 712 $ — $ 190 $ (712 ) $ 190 $ — (a) Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of September 30, 2017 , cash collateral of $39 million was netted with the mark-to-market derivative liabilities. As of December 31, 2016 , $24 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 $15 million and $13 million classified as current at September 30, 2017 and December 31, 2016 , respectively. (d) Includes $130 million classified as current at December 31, 2016 . 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 include 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 $0.27 to $1.22 per gallon and (2) the probability of renewal of 50 percent for the first five -year term and 75 percent for the second five -year term of the gas purchase agreement and the related keep-whole processing agreement. For these contracts, increases in forward NGL prices result in a decrease in the fair value of the derivative assets and an increase in the fair value of the derivative liabilities. The forward prices for the individual NGL products generally increase or decrease in a positive correlation with one another. Increases or decreases in forward NGL prices result in an increase or decrease in the fair value of the embedded derivative. An increase in the probability of renewal would result in an increase in the fair value of the related embedded derivative liability. The contingent consideration represents the fair value of the remaining amount we expected to pay to BP related to the earnout provision associated with our 2013 acquisition of BP’s refinery in Texas City, Texas and related logistics and marketing assets. The fair value of the remaining contingent consideration as of December 31, 2016 was estimated using an income approach and was therefore a Level 3 liability. The fair value calculation used significant unobservable inputs including: (1) an estimate of forecasted monthly refinery throughput volumes; (2) an internal and external monthly crack spread forecast; and (3) a range of risk-adjusted discount rates. The fair value of the contingent consideration liability was reassessed each quarter, with changes in fair value recorded in cost of revenues. The balance of $131 million was paid on April 12, 2017. On the consolidated statements of cash flows for the nine months ended September 30, 2017 , $89 million of the contingent earnout payment is included as a financing activity with the remainder included as an operating activity. 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 Nine Months Ended (In millions) 2017 2016 2017 2016 Beginning balance $ 41 $ 171 $ 190 $ 342 Contingent consideration payment — — (131 ) (200 ) Unrealized and realized losses included in net income 22 6 8 33 Settlements of derivative instruments (6 ) (1 ) (10 ) 1 Ending balance $ 57 $ 176 $ 57 $ 176 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 $ 17 $ 4 $ 8 $ 19 Contingent consideration agreement — 2 1 11 Total $ 17 $ 6 $ 9 $ 30 Fair Values – Reported The following table summarizes financial instruments on the basis of their nature, characteristics and risk at September 30, 2017 and December 31, 2016 , excluding the derivative financial instruments and contingent consideration reported above. September 30, 2017 December 31, 2016 (In millions) Fair Value Carrying Value Fair Value Carrying Value Financial assets: Investments $ 25 $ 2 $ 25 $ 2 Other 25 25 21 21 Total financial assets $ 50 $ 27 $ 46 $ 23 Financial liabilities: Long-term debt (a) $ 13,690 $ 12,544 $ 10,892 $ 10,297 Deferred credits and other liabilities 121 107 121 109 Total financial liabilities $ 13,811 $ 12,651 $ 11,013 $ 10,406 (a) Excludes capital leases and debt issuance costs; however, includes amount classified as debt due within one year. Our current assets and liabilities include financial instruments, the most significant of which are trade accounts receivable and payables. We believe the carrying values of our current assets and liabilities approximate fair value. Our fair value assessment incorporates a variety of considerations, including (1) the short-term duration of the instruments, (2) our investment-grade credit rating and (3) our historical incurrence of and expected future insignificance of bad debt expense, which includes an evaluation of counterparty credit risk. Fair values of our financial assets included in investments and other financial assets and of our financial liabilities included in deferred credits and other liabilities are measured primarily using an income approach and most inputs are internally generated, which results in a Level 3 classification. Estimated future cash flows are discounted using a rate deemed appropriate to obtain the fair value. Other financial assets primarily consist of environmental remediation receivables. Deferred credits and other liabilities primarily consist of a liability resulting from a financing arrangement for the construction of MPLX’s steam methane reformer (“SMR”) 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 a market approach, based upon the average of quotes for our debt from major financial institutions and a third-party valuation service. Because these quotes cannot be independently verified to the market, they are considered Level 3 inputs. Fair value of variable-rate long-term debt approximates the carrying value.

Derivatives

Derivatives	9 Months Ended
	Sep. 30, 2017
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 14 . 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 September 30, 2017 and December 31, 2016 : (In millions) September 30, 2017 Balance Sheet Location Asset Liability Commodity derivatives Other current assets $ 257 $ 296 Other current liabilities (a) — 15 Deferred credits and other liabilities (a) — 42 (In millions) December 31, 2016 Balance Sheet Location Asset Liability Commodity derivatives Other current assets $ 688 $ 712 Other current liabilities (a) — 13 Deferred credits and other liabilities (a) — 47 (a) Includes embedded derivatives. The tables below summarize open commodity derivative contracts for crude oil and refined products as of September 30, 2017 . Position Total Barrels (In thousands) Crude Oil (a) Exchange-traded Long 33,043 Exchange-traded Short (34,428 ) (a ) 94 percent of the exchange-traded contracts expire in the fourth quarter of 2017 . Position Total Gallons (In thousands) Refined Products (a) Exchange-traded Long 316,764 Exchange-traded Short (227,388 ) OTC Short (33,388 ) (a ) 100 percent of the exchange-traded contracts expire in the fourth quarter of 2017 . The following table summarizes the effect of all commodity derivative instruments in our consolidated statements of income: Gain (Loss) Gain (Loss) (In millions) Three Months Ended September 30, Nine Months Ended September 30, Income Statement Location 2017 2016 2017 2016 Sales and other operating revenues $ (10 ) $ (3 ) $ 8 $ (4 ) Cost of revenues 1 (20 ) (30 ) (91 ) Total $ (9 ) $ (23 ) $ (22 ) $ (95 )

Debt

Debt	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Debt	Debt Our outstanding borrowings at September 30, 2017 and December 31, 2016 consisted of the following: (In millions) September 30, 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 — — Term loan agreement due 2019 — 200 Senior notes, 2.700% due December 2018 600 600 Senior notes, 3.400% due December 2020 650 650 Senior notes, 5.125% due March 2021 1,000 1,000 Senior notes, 3.625%, due September 2024 750 750 Senior notes, 6.500%, due March 2041 1,250 1,250 Senior notes, 4.750%, due September 2044 800 800 Senior notes, 5.850% due December 2045 250 250 Senior notes, 5.000%, due September 2054 400 400 MPLX LP: MPLX term loan facility due 2019 — 250 MPLX bank revolving credit facility due 2022 420 — MPLX senior notes, 5.500%, due February 2023 710 710 MPLX senior notes, 4.500%, due July 2023 989 989 MPLX senior notes, 4.875%, due December 2024 1,149 1,149 MPLX senior notes, 4.000%, due February 2025 500 500 MPLX senior notes, 4.875%, due June 2025 1,189 1,189 MarkWest senior notes, 4.500% - 5.500%, due 2023 - 2025 63 63 MPLX senior notes, 4.125%, due March 2027 1,250 — MPLX senior notes, 5.200%, due March 2047 1,000 — Capital lease obligations due 2017-2028 299 319 Total 13,269 11,069 Unamortized debt issuance costs (61 ) (44 ) Unamortized discount (a) (426 ) (453 ) Amounts due within one year (29 ) (28 ) Total long-term debt due after one year $ 12,753 $ 10,544 (a) Includes $386 million and $420 million of unamortized discount as of September 30, 2017 and December 31, 2016 , respectively, related to the difference between the fair value and the principal amount of assumed MarkWest debt. During the nine months ended September 30, 2017 , we borrowed and repaid $300 million under the commercial paper program. At September 30, 2017 , we had no amounts outstanding under the commercial paper program. At September 30, 2017 , we had no amounts outstanding under our trade receivables securitization facility. MPC Bank Revolving Credit Facilities On July 21, 2017, we entered into credit agreements with a syndicate of lenders to replace MPC’s previous $2.5 billion four -year bank revolving credit facility and $1 billion 364 -day revolving credit facility. The new credit agreements provide for a $2.5 billion five -year bank revolving credit facility that expires in July 2022 and a $1 billion 364 -day bank revolving credit facility that expires in July 2018. The financial covenants and the interest rate terms contained in the new credit agreements are substantially the same as those contained in the previous bank revolving credit facilities. There were no borrowings or letters of credit outstanding under the MPC bank revolving credit facility at September 30, 2017 . MPC Term Loan Agreement On March 31, 2017, we repaid the remaining $200 million outstanding under the MPC term loan agreement with available cash on hand. Under the provisions of the MPC term loan agreement, the loan may be prepaid in whole or in part without premium or penalty. The maturity date of the MPC term loan agreement was September 24, 2019. MPLX Credit Agreement On July 21, 2017, MPLX entered into a credit agreement to replace its previous $2 billion five -year bank revolving credit facility with a $2.25 billion five -year bank revolving credit facility that expires in July 2022. The financial covenants and the interest rate terms contained in the new credit agreement are substantially the same as those contained in the previous bank revolving credit facility. Additionally, on July 19, 2017, MPLX prepaid the entire outstanding principal amount of its $250 million term loan with cash on hand. During the nine months ended September 30, 2017 , MPLX borrowed $420 million under the MPLX bank revolving credit facility, at an average interest rate of 2.7 percent , and made no repayments. At September 30, 2017 , MPLX had $420 million outstanding borrowings and $3 million letters of credit outstanding under the MPLX bank revolving credit facility, resulting in total availability of $1.83 billion . MPLX Senior Notes On February 10, 2017, MPLX completed a public offering of $1.25 billion aggregate principal amount of 4.125% unsecured senior notes due March 2027 and $1.0 billion aggregate principal amount of 5.200% unsecured senior notes due March 2047. The net proceeds, which were approximately $2.22 billion after deducting underwriting discounts, were used by MPLX to fund the $1.5 billion cash portion of the consideration paid to MPC for the dropdown of assets on March 1, 2017, as well as for general partnership purposes. Interest is payable semi-annually in arrears on March 1 and September 1 of each year, commencing on September 1, 2017.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	9 Months Ended
	Sep. 30, 2017
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information Nine Months Ended (In millions) 2017 2016 Net cash provided by operating activities included: Interest paid (net of amounts capitalized) $ 446 $ 400 Net income taxes paid to (refunded from) taxing authorities 383 28 Non-cash investing and financing activities: Contribution of assets to joint venture (a) 337 — (a) MarkWest’s contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. See Note 4 . 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: Nine Months Ended (In millions) 2017 2016 Additions to property, plant and equipment per consolidated statements of cash flows $ 1,928 $ 2,147 Asset retirement expenditures 1 4 Decrease in capital accruals (9 ) (169 ) Total capital expenditures before acquisitions 1,920 1,982 Acquisitions (a) 250 (133 ) Total capital expenditures $ 2,170 $ 1,849 (a) The nine months ended September 30, 2017 reflects primarily the acquisition of the Ozark pipeline. The nine months ended September 30, 2016 reflects adjustments to the fair values of the property, plant and equipment, intangibles and goodwill acquired in connection with the MarkWest Merger.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	9 Months Ended
	Sep. 30, 2017
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, 2015 $ (255 ) $ (70 ) $ 4 $ 3 $ (318 ) Other comprehensive income (loss) before reclassifications (8 ) 1 — — (7 ) Amounts reclassified from accumulated other comprehensive loss: Amortization – prior service credit (a) (35 ) (2 ) — — (37 ) – actuarial loss (a) 28 1 — — 29 – settlement loss (a) 7 — — — 7 Other (b) — — — (1 ) (1 ) Tax effect — — — — — Other comprehensive income (loss) (8 ) — — (1 ) (9 ) Balance as of September 30, 2016 $ (263 ) $ (70 ) $ 4 $ 2 $ (327 ) (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 income (loss) before reclassifications (2 ) — — — (2 ) Amounts reclassified from accumulated other comprehensive loss: Amortization – prior service credit (a) (29 ) (2 ) — — (31 ) – actuarial loss/(gain) (a) 27 (1 ) — — 26 – settlement loss (a) 2 — — — 2 Other (b) — — — (2 ) (2 ) Tax effect — 1 — 1 2 Other comprehensive income (loss) (2 ) (2 ) — (1 ) (5 ) Balance as of September 30, 2017 $ (235 ) $ (9 ) $ 4 $ 1 $ (239 ) (a) These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 19 . (b) This amount was reclassified out of accumulated other comprehensive loss and is included in selling, general and administrative on the consolidated statements of income.

Defined Benefit Pension and Oth

Defined Benefit Pension and Other Postretirement Plans	9 Months Ended
	Sep. 30, 2017
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 September 30, Pension Benefits Other Benefits (In millions) 2017 2016 2017 2016 Components of net periodic benefit cost: Service cost $ 33 $ 29 $ 6 $ 8 Interest cost 19 18 8 9 Expected return on plan assets (25 ) (24 ) — — Amortization – prior service credit (10 ) (12 ) — (1 ) – actuarial loss 9 10 — — – settlement loss 1 4 — — Net periodic benefit cost $ 27 $ 25 $ 14 $ 16 Nine Months Ended September 30, Pension Benefits Other Benefits (In millions) 2017 2016 2017 2016 Components of net periodic benefit cost: Service cost $ 99 $ 86 $ 19 $ 24 Interest cost 56 55 23 26 Expected return on plan assets (75 ) (73 ) — — Amortization – prior service credit (29 ) (35 ) (2 ) (2 ) – actuarial loss/(gain) 27 28 (1 ) 1 – settlement loss 2 7 — — Net periodic benefit cost $ 80 $ 68 $ 39 $ 49 During the nine months ended September 30, 2017 , we chose to make a $120 million voluntary contribution to our funded pension plans. Benefit payments related to unfunded pension and other postretirement benefit plans were $7 million and $23 million , respectively, during the nine months ended September 30, 2017 .

Stock-Based Compensation Plans

Stock-Based Compensation Plans	9 Months Ended
	Sep. 30, 2017
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 nine months ended September 30, 2017 : Number of Shares Weighted Average Exercise Price Outstanding at December 31, 2016 9,531,440 $ 28.93 Granted 1,214,112 50.57 Exercised (1,356,217 ) 21.89 Forfeited, canceled or expired (78,386 ) 41.97 Outstanding at September 30, 2017 9,310,949 32.66 The grant date fair value of stock option awards granted during the nine months ended September 30, 2017 was $13.42 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 nine months ended September 30, 2017 : 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, 2016 1,250,343 $ 41.51 361,117 $ 28.26 Granted 574,602 50.20 28,573 51.94 RS’s Vested/RSU’s Issued (522,454 ) 42.48 (79,635 ) 24.54 Forfeited (83,806 ) 44.29 (13,750 ) 50.20 Outstanding at September 30, 2017 1,218,685 45.00 296,305 30.52 Performance Unit Awards The following table presents a summary of the activity for performance unit awards to be settled in shares for the nine months ended September 30, 2017 : Number of Units Weighted Average Grant Date Fair Value Outstanding at December 31, 2016 6,255,178 $ 0.78 Granted 2,584,750 0.92 Exercised (1,854,728 ) 0.85 Canceled (99,658 ) 0.78 Outstanding at September 30, 2017 6,885,542 0.81 The performance unit awards granted during the nine months ended September 30, 2017 have a grant date fair value of $0.92 per unit, as calculated using a Monte Carlo valuation model. MPLX Awards During the nine months ended September 30, 2017 , 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	9 Months Ended
	Sep. 30, 2017
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 September 30, 2017 and December 31, 2016 , accrued liabilities for remediation totaled $117 million and $132 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 and $58 million at September 30, 2017 and December 31, 2016 , respectively. We are involved in a number of environmental enforcement matters arising in the ordinary course of business. While the outcome and impact on us cannot be predicted with certainty, management believes the resolution of these environmental matters will not, individually or collectively, have a material adverse effect on our consolidated results of operations, financial position or cash flows. MarkWest Environmental Proceeding – In July 2015, representatives from the EPA and the United States Department of Justice conducted a raid on a pipeline launcher/receiver site of MarkWest Liberty Midstream & Resources, L.L.C., a wholly-owned subsidiary of MPLX (“MarkWest Liberty Midstream”), utilized for pipeline maintenance operations in Washington County, Pennsylvania pursuant to a search warrant issued by a magistrate of the United States District Court for the Western District of Pennsylvania. As part of this initiative, the U.S. Attorney’s Office for the Western District of Pennsylvania, with the assistance of EPA’s Criminal Investigation Division proceeded with an investigation of MarkWest’s launcher/receiver, pipeline and compressor station operations. In response to the investigation, MarkWest initiated independent studies which demonstrated that there was no risk to worker safety and no threat of public harm associated with MarkWest Liberty Midstream’s launcher/receiver operations. These findings were supported by a subsequent inspection and review by the Occupational Safety and Health Administration. After providing these studies, and other substantial documentation related to MarkWest Liberty Midstream's pipeline and compressor stations, and arranging site visits and conducting several meetings with the government’s representatives, on September 13, 2016, the U.S. Attorney’s Office for the Western District of Pennsylvania rendered a declination decision, dropping its criminal investigation and declining to pursue charges in this matter. MarkWest Liberty Midstream continues to discuss with the EPA and the State of Pennsylvania civil enforcement allegations associated with permitting or other related regulatory obligations for its launcher/receiver and compressor station facilities in the region. In connection with these discussions, MarkWest Liberty Midstream received an initial proposal from the EPA to settle all civil claims associated with this matter for the combination of a proposed cash penalty of approximately $2.4 million and proposed supplemental environmental projects with an estimated cost of approximately $3.6 million . MarkWest Liberty Midstream has submitted a response asserting that this action involves novel issues surrounding primarily minor source emissions from facilities that the agencies themselves considered de minimis and were not the subject of regulation and consequently that the settlement proposal is excessive. In connection with these negotiations, MarkWest Liberty Midstream has received a revised settlement proposal from the EPA which proposes to lower the proposed cash penalty to approximately $1.2 million and the estimated cost of proposed supplemental environmental projects to an estimated cost of approximately $1.6 million . MarkWest Liberty Midstream will continue to negotiate with the EPA regarding the amount and scope of the proposed settlement. Other Lawsuits —On August 1, 2017, we entered into binding settlement agreements with the plaintiffs and co-defendants to settle four lawsuits brought forth by the plaintiffs alleging personal injuries from a fire that occurred at our Galveston Bay refinery on January 11, 2016. The other co-defendants in this litigation were contractors that were engaged by us to provide services at our Galveston Bay refinery. We recorded a liability for our losses under the settlement agreements which resulted in a charge of $86 million in the second quarter of 2017. We are vigorously pursuing recovery of such losses, as well as defense costs, through indemnification from a significant contractor who is not party to the settlement agreements. 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 early stage, the ultimate outcome of this litigation remains uncertain, and neither the likelihood of an unfavorable outcome nor the ultimate liability, if any, can be determined, and we are unable to estimate a reasonably possible loss (or range of loss) for this matter. We intend to vigorously defend ourselves in this matter. In May 2007, the Kentucky attorney general filed a lawsuit against us and Marathon Oil in state court in Franklin County, Kentucky for alleged violations of Kentucky’s emergency pricing and consumer protection laws following Hurricanes Katrina and Rita in 2005. The lawsuit alleges that we overcharged customers by $89 million during September and October 2005 . The complaint seeks disgorgement of these sums, as well as penalties, under Kentucky’s emergency pricing and consumer protection laws. We are vigorously defending this litigation. We believe that this is the first lawsuit for damages and injunctive relief under the Kentucky emergency pricing laws to progress this far and it contains many novel issues. In May 2011, the Kentucky attorney general amended his complaint to include a request for immediate injunctive relief as well as unspecified damages and penalties related to our wholesale gasoline pricing in April and May 2011 under statewide price controls that were activated by the Kentucky governor on April 26, 2011 and which have since expired. The court denied the attorney general’s request for immediate injunctive relief, and the remainder of the 2011 claims likely will be resolved along with those dating from 2005. If the lawsuit is resolved unfavorably in its entirety, it could materially impact our consolidated results of operations, financial position or cash flows. However, management does not believe the ultimate resolution of this litigation will have a material adverse effect. We are also a party to a number of other lawsuits and other proceedings arising in the ordinary course of business. While the ultimate outcome and impact to us cannot be predicted with certainty, we believe that the resolution of these other lawsuits and proceedings will not have a material adverse effect on our consolidated financial position, results of operations or cash flows. Guarantees— We have provided certain guarantees, direct and indirect, of the indebtedness of other companies. Under the terms of most of these guarantee arrangements, we would be required to perform should the guaranteed party fail to fulfill its obligations under the specified arrangements. In addition to these financial guarantees, we also have various performance guarantees related to specific agreements. Guarantees related to indebtedness of equity method investees —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 September 30, 2017 . 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 $22 million as of September 30, 2017 . 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 September 30, 2017 , 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 $139 million as of September 30, 2017 . 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 September 30, 2017 , which consist of unrecognized tax benefits related to MPC, its consolidated subsidiaries and the refining, marketing and transportation business operations prior to our spinoff which are not already reflected in the unrecognized tax benefits described in Note 11 , and other contingent liabilities Marathon Oil may incur related to taxes. Furthermore, the separation and distribution agreement and other agreements with Marathon Oil to effect our spinoff provide for cross-indemnities between Marathon Oil and us. In general, Marathon Oil is required to indemnify us for any liabilities relating to Marathon Oil’s historical oil and gas exploration and production operations, oil sands mining operations and integrated gas operations, and we are required to indemnify Marathon Oil for any liabilities relating to Marathon Oil’s historical refining, marketing and transportation operations. The terms of these indemnifications are indefinite and the amounts are not capped. Other guarantees —We have entered into other guarantees with maximum potential undiscounted payments totaling $93 million as of September 30, 2017 , 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 September 30, 2017 , our contractual commitments to acquire property, plant and equipment and advance funds to equity method investees totaled $694 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. As of September 30, 2017 , management does not believe there are any indications that we will not be able to meet the construction milestones, that force majeure does not apply, or that such fees and charges will otherwise be triggered.

Supplementary Statistics

Supplementary Statistics	9 Months Ended
	Sep. 30, 2017
Text Block [Abstract]
Supplementary Statistics	Supplementary Statistics (Unaudited) Three Months Ended Nine Months Ended (In millions) 2017 2016 2017 2016 Income from Operations by segment Refining & Marketing (a)(b) $ 1,097 $ 252 $ 1,589 $ 1,191 Speedway (b) 209 209 583 569 Midstream (a)(c) 355 310 996 752 Items not allocated to segments: Corporate and other unallocated items (a)(c) (86 ) (65 ) (251 ) (194 ) Pension settlement expenses (1 ) (4 ) (2 ) (7 ) Litigation — — (86 ) — Impairments (d) 2 (267 ) 21 (486 ) Income from operations $ 1,576 $ 435 $ 2,850 $ 1,825 Capital Expenditures and Investments (e) Refining & Marketing $ 198 $ 251 $ 570 $ 756 Speedway 108 71 221 191 Midstream (f) 453 410 2,017 1,179 Corporate and Other (g) 32 29 92 106 Total $ 791 $ 761 $ 2,900 $ 2,232 (a) We revised our operating segment presentation in the first quarter of 2017 in connection with the contribution of certain terminal, pipeline and storage assets to MPLX. The operating results for these assets, which were previously included in the Refining & Marketing segment, are now included in the Midstream segment. Comparable prior period information has been recast to reflect our revised presentation. The results for the pipeline and storage assets were recast effective January 1, 2015, and the results for the terminal assets were recast effective April 1, 2016. Prior to these dates, these assets were not considered businesses and, therefore, there are no financial results from which to recast segment results. (b) The Refining & Marketing and Speedway segments include inventory LCM benefits of $345 million and $25 million , respectively, for the nine months ended September 30, 2016 . (c) Corporate overhead expenses attributable to MPLX are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments. (d) 2017 includes MPC’s share of gains related to the sale of assets remaining from the Sandpiper pipeline project. 2016 relates to impairments of goodwill and equity method investments. (e) Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates. (f) The nine months ended September 30, 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. (g) Includes capitalized interest of $13 million and $15 million for the three months ended September 30, 2017 and 2016 , respectively, and $39 million and $47 million for the nine months ended September 30, 2017 and 2016 , respectively. Supplementary Statistics (Unaudited) Three Months Ended Nine Months Ended 2017 2016 2017 2016 MPC Consolidated Refined Product Sales Volumes (mbpd) (a) 2,357 2,316 2,272 2,274 Refining & Marketing Operating Statistics Refining & Marketing refined product sales volume (mbpd) (b) 2,357 2,307 2,263 2,265 Refining & Marketing gross margin (dollars per barrel) (c)(d) $ 14.14 $ 10.67 $ 12.42 $ 11.11 Crude oil capacity utilization percent (e) 102 100 96 95 Refinery throughputs (mbpd): (f) Crude oil refined 1,845 1,791 1,741 1,708 Other charge and blendstocks 172 135 176 156 Total 2,017 1,926 1,917 1,864 Sour crude oil throughput percent 57 59 61 60 WTI-priced crude oil throughput percent 23 20 20 20 Refined product yields (mbpd): (f) Gasoline 939 907 910 908 Distillates 673 647 627 616 Propane 38 38 35 35 Feedstocks and special products 298 253 285 245 Heavy fuel oil 45 43 36 36 Asphalt 67 70 64 58 Total 2,060 1,958 1,957 1,898 Refinery direct operating costs (dollars per barrel): (g) Planned turnaround and major maintenance $ 1.20 $ 1.62 $ 1.69 $ 1.72 Depreciation and amortization 1.34 1.42 1.44 1.46 Other manufacturing (h) 3.83 4.01 4.10 4.03 Total $ 6.37 $ 7.05 $ 7.23 $ 7.21 Refining & Marketing Operating Statistics By Region - Gulf Coast Refinery throughputs (mbpd): (i) Crude oil refined 1,123 1,073 1,041 1,057 Other charge and blendstocks 217 185 219 199 Total 1,340 1,258 1,260 1,256 Sour crude oil throughput percent 69 72 75 73 WTI-priced crude oil throughput percent 14 8 10 7 Refined product yields (mbpd): (i) Gasoline 538 511 525 530 Distillates 438 411 393 407 Propane 25 27 25 26 Feedstocks and special products 326 289 310 283 Heavy fuel oil 31 30 24 24 Asphalt 19 17 17 15 Total 1,377 1,285 1,294 1,285 Refinery direct operating costs (dollars per barrel): (g) Planned turnaround and major maintenance $ 0.90 $ 2.05 $ 1.86 $ 1.87 Depreciation and amortization 1.05 1.14 1.15 1.13 Other manufacturing (h) 3.52 3.70 3.81 3.62 Total $ 5.47 $ 6.89 $ 6.82 $ 6.62 Supplementary Statistics (Unaudited) Three Months Ended Nine Months Ended 2017 2016 2017 2016 Refining & Marketing Operating Statistics By Region – Midwest Refinery throughputs (mbpd): (i) Crude oil refined 722 718 700 651 Other charge and blendstocks 35 39 31 37 Total 757 757 731 688 Sour crude oil throughput percent 38 39 41 39 WTI-priced crude oil throughput percent 38 39 34 41 Refined product yields (mbpd): (i) Gasoline 401 396 385 378 Distillates 235 236 234 209 Propane 14 13 11 11 Feedstocks and special products 50 51 47 40 Heavy fuel oil 15 13 13 12 Asphalt 48 53 47 43 Total 763 762 737 693 Refinery direct operating costs (dollars per barrel): (g) Planned turnaround and major maintenance $ 1.60 $ 0.72 $ 1.22 $ 1.26 Depreciation and amortization 1.72 1.72 1.80 1.90 Other manufacturing (h) 3.96 4.04 4.19 4.29 Total $ 7.28 $ 6.48 $ 7.21 $ 7.45 Speedway Operating Statistics (j) Convenience stores at period-end 2,734 2,773 Gasoline and distillate sales (millions of gallons) 1,464 1,575 4,332 4,605 Gasoline and distillate gross margin (dollars per gallon) (k) $ 0.1772 $ 0.1773 $ 0.1727 $ 0.1668 Merchandise sales (in millions) $ 1,295 $ 1,338 $ 3,693 $ 3,777 Merchandise gross margin (in millions) $ 374 $ 386 $ 1,065 $ 1,085 Merchandise gross margin percent 28.9 % 28.9 % 28.8 % 28.7 % Same store gasoline sales volume (period over period) (3.1 %) (0.6 %) (1.6 %) 0.2 % Same store merchandise sales (period over period) (l) 0.3 % 4.0 % 1.5 % 3.0 % Midstream Operating Statistics Crude oil and refined product pipeline throughputs (mbpd) (m) 3,562 3,113 3,299 2,953 Terminal throughput (mbpd) (n) 1,496 1,517 1,470 1,510 Gathering system throughput (MMcf/d) (o) 3,729 3,306 3,415 3,313 Natural gas processed (MMcf/d) (o) 6,581 5,906 6,336 5,691 C2 (ethane) + NGLs (natural gas liquids) fractionated (mbpd) (o) 397 348 384 330 (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) Excludes LCM inventory valuation adjustments. Comparable prior period information for gross margin has been recast in connection with the contribution of certain pipeline assets to MPLX on March 1, 2017. (e) Based on calendar day capacity, which is an annual average that includes downtime for planned maintenance and other normal operating activities. (f) Excludes inter-refinery volumes of 80 mbpd and 89 mbpd for the three months ended September 30, 2017 and 2016 , respectively, and 74 mbpd and 80 mbpd for the nine months ended September 30, 2017 and 2016 , respectively. (g) Per barrel of total refinery throughputs. (h) Includes utilities, labor, routine maintenance and other operating costs. (i) Includes inter-refinery transfer volumes. (j) Third quarter and year-to-date 2017 operating statistics do not reflect any information for the 41 travel centers contributed to PFJ Southeast, whereas they are reflected in the third quarter and year-to-date 2016 operating statistics. (k) Excludes LCM inventory valuation adjustments. The price paid by consumers less the cost of refined products, including transportation, consumer excise taxes and bankcard processing fees, divided by gasoline and distillate sales volume. (l) Excludes cigarettes. (m) Includes common-carrier pipelines and private pipelines contributed to MPLX, excluding equity method investments. (n) Includes the results of the terminal assets contributed to MPLX from the date the assets became a business, April 1, 2016. (o) Includes amounts related to unconsolidated equity method investments on a 100 percent basis.

Description of the Business a34

Description of the Business and Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2017
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.
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)	9 Months Ended
	Sep. 30, 2017
Noncontrolling Interest [Abstract]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Table Text Block]	Changes in MPC’s equity and the offsetting changes to noncontrolling interest resulting from changes in MPC’s and the noncontrolling interest’s ownership interests in MPLX were as follows: Nine Months Ended (In millions) 2017 2016 Transfers (to) from noncontrolling interest Increase (decrease) in MPC's additional paid in capital for the issuance of MPLX LP common units to the public $ 25 $ (43 ) Increase in MPC's additional paid in capital for the issuance of MPLX LP common units and general partner units to MPC 113 — Net transfers (to) from noncontrolling interests 138 (43 ) Tax impact (26 ) (70 ) Change in MPC's additional paid-in capital, net of tax $ 112 $ (113 )

Acquisitions and Investments (T

Acquisitions and Investments (Tables)	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Business Acquisition, Pro Forma Information [Table Text Block]	The amounts of revenue and income from operations associated with the acquisition included in our consolidated statements of income, since the March 1, 2017 acquisition date, are as follows: Three Months Ended September 30, Seven Months Ended September 30, (In millions) 2017 2017 Sales and other operating revenues (including consumer excise taxes) $ 19 $ 45 Income from operations 6 17

Related Party Transactions (Tab

Related Party Transactions (Tables)	9 Months Ended
	Sep. 30, 2017
Related Party Transactions [Abstract]
Sales to Related Parties	Sales to related parties were as follows: Three Months Ended Nine Months Ended (In millions) 2017 2016 2017 2016 PFJ Southeast $ 155 $ — $ 451 $ — Other equity method investees 2 2 7 5 Total $ 157 $ 2 $ 458 $ 5
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 Nine Months Ended (In millions) 2017 2016 2017 2016 MarkWest Utica EMG $ 5 $ 5 $ 13 $ 12 Ohio Gathering 4 5 12 12 Other equity method investees 4 2 14 7 Total $ 13 $ 12 $ 39 $ 31
Purchases From Related Parties	Purchases from related parties were as follows: Three Months Ended Nine Months Ended (In millions) 2017 2016 2017 2016 Crowley Blue Water Partners $ 16 $ 16 $ 44 $ 22 Crowley Ocean Partners 20 15 59 32 Explorer 7 4 7 12 Illinois Extension Pipeline 26 27 75 82 LOCAP 6 6 17 18 LOOP 14 14 53 42 TAAE 22 9 53 29 TACE 9 10 34 39 TAME 20 23 58 67 Other equity method investees 8 4 20 16 Total $ 148 $ 128 $ 420 $ 359
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) September 30, December 31, MarkWest Utica EMG $ 2 $ 2 Ohio Gathering 2 2 PFJ Southeast 32 40 Other equity method investees 4 1 Total $ 40 $ 45
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) September 30, December 31, Illinois Extension Pipeline $ 9 $ 9 LOCAP 2 2 LOOP 5 6 MarkWest Utica EMG 30 24 TAAE 2 2 TACE 1 4 TAME 2 4 Other equity method investees 13 2 Total $ 64 $ 53

Income per Common Share (Tables

Income per Common Share (Tables)	9 Months Ended
	Sep. 30, 2017
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 Nine Months Ended (In millions, except per share data) 2017 2016 2017 2016 Basic earnings per share: Allocation of earnings: Net income attributable to MPC $ 903 $ 145 $ 1,416 $ 947 Income allocated to participating securities — — 1 1 Income available to common stockholders – basic $ 903 $ 145 $ 1,415 $ 946 Weighted average common shares outstanding 504 527 514 528 Basic earnings per share $ 1.79 $ 0.28 $ 2.75 $ 1.79 Diluted earnings per share: Allocation of earnings: Net income attributable to MPC $ 903 $ 145 $ 1,416 $ 947 Income allocated to participating securities — — 1 1 Income available to common stockholders – diluted $ 903 $ 145 $ 1,415 $ 946 Weighted average common shares outstanding 504 527 514 528 Effect of dilutive securities 4 3 4 3 Weighted average common shares, including dilutive effect 508 530 518 531 Diluted earnings per share $ 1.77 $ 0.27 $ 2.73 $ 1.78
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 Nine Months Ended (In millions) 2017 2016 2017 2016 Shares issued under stock-based compensation plans 1 3 1 3

Equity (Tables)

Equity (Tables)	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Share Repurchases	Total share repurchases were as follows for the three and nine months ended September 30, 2017 and 2016 : Three Months Ended Nine Months Ended (In millions, except per share data) 2017 2016 2017 2016 Number of shares repurchased 8 1 31 4 Cash paid for shares repurchased $ 452 $ 51 $ 1,622 $ 177 Effective average cost per delivered share $ 53.85 $ 42.76 $ 52.16 $ 41.14

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2017
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 September 30, 2017 Revenues: Third party $ 13,573 $ 4,895 $ 585 $ 19,053 Intersegment (a) 2,904 1 369 3,274 Related party 155 2 — 157 Segment revenues $ 16,632 $ 4,898 $ 954 $ 22,484 Segment income from operations (b) $ 1,097 $ 209 $ 355 $ 1,661 Income from equity method investments 6 20 57 83 Depreciation and amortization (c) 266 68 169 503 Capital expenditures and investments (d) 198 108 453 759 (In millions) Refining & Marketing Speedway Midstream Total Three Months Ended September 30, 2016 Revenues: Third party $ 11,284 $ 4,848 $ 484 $ 16,616 Intersegment (a) 2,798 1 346 3,145 Related party 2 — — 2 Segment revenues $ 14,084 $ 4,849 $ 830 $ 19,763 Segment income from operations (b) $ 252 $ 209 $ 310 $ 771 Income from equity method investments (c) 8 — 51 59 Depreciation and amortization (c) 267 71 155 493 Capital expenditures and investments (d) 251 71 410 732 (In millions) Refining & Marketing Speedway Midstream Total Nine Months Ended September 30, 2017 Revenues: Third party $ 37,485 $ 14,070 $ 1,665 $ 53,220 Intersegment (a) 8,302 3 1,076 9,381 Related party 452 6 — 458 Segment revenues $ 46,239 $ 14,079 $ 2,741 $ 63,059 Segment income from operations (b) $ 1,589 $ 583 $ 996 $ 3,168 Income from equity method investments 10 54 139 203 Depreciation and amortization (c) 805 197 528 1,530 Capital expenditures and investments (d)(e) 570 221 2,017 2,808 (In millions) Refining & Marketing Speedway Midstream Total Nine Months Ended September 30, 2016 Revenues: Third party $ 31,192 $ 13,663 $ 1,324 $ 46,179 Intersegment (a) 7,872 2 911 8,785 Related party 5 — — 5 Segment revenues $ 39,069 $ 13,665 $ 2,235 $ 54,969 Segment income from operations (b)(f) $ 1,191 $ 569 $ 752 $ 2,512 Income from equity method investments (c) 10 — 110 120 Depreciation and amortization (c) 801 203 448 1,452 Capital expenditures and investments (d) 756 191 1,179 2,126 (a) Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties. (b) Corporate overhead expenses attributable to MPLX are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments. (c) Differences between segment totals and MPC totals represent amounts related to unallocated items and are included in “Items not allocated to segments” in the reconciliation below. (d) Capital expenditures include changes in capital accruals, acquisitions (including any goodwill) and investments in affiliates. (e) 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 nine months ended September 30, 2017 . (f) The Refining & Marketing and Speedway segments include inventory LCM benefits of $345 million and $25 million , respectively, for the nine months ended September 30, 2016 .
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 Nine Months Ended (In millions) 2017 2016 2017 2016 Segment income from operations $ 1,661 $ 771 $ 3,168 $ 2,512 Items not allocated to segments: Corporate and other unallocated items (a) (86 ) (65 ) (251 ) (194 ) Pension settlement expenses (1 ) (4 ) (2 ) (7 ) Litigation (b) — — (86 ) — Impairments (c) 2 (267 ) 21 (486 ) Net interest and other financial income (costs) (157 ) (141 ) (465 ) (420 ) Income before income taxes $ 1,419 $ 294 $ 2,385 $ 1,405 (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. (b) See Note 21 for further information on litigation matters. (c) 2017 includes MPC’s share of gains related to the sale of assets remaining from the Sandpiper pipeline project. 2016 relates to impairments of goodwill and equity method investments.
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 Nine Months Ended (In millions) 2017 2016 2017 2016 Segment capital expenditures and investments $ 759 $ 732 $ 2,808 $ 2,126 Less investments in equity method investees (a) 53 69 730 383 Plus items not allocated to segments: Corporate and Other 19 14 53 59 Capitalized interest 13 15 39 47 Total capital expenditures (b) $ 738 $ 692 $ 2,170 $ 1,849 (a) The nine months ended September 30, 2017 includes an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system. The nine months ended September 30, 2016 includes an adjustment of $143 million to the fair value of equity method investments acquired in connection with the MarkWest Merger. (b) Capital expenditures include changes in capital accruals. See Note 17 for a reconciliation of total capital expenditures to additions to property, plant and equipment as reported in the consolidated statements of cash flows.

Other Items (Tables)

Other Items (Tables)	9 Months Ended
	Sep. 30, 2017
Other Income and Expenses [Abstract]
Net Interest And Other Financial Income (Costs)	Net interest and other financial income (costs) was: Three Months Ended Nine Months Ended (In millions) 2017 2016 2017 2016 Interest income $ 7 $ 3 $ 16 $ 5 Interest expense (172 ) (153 ) (508 ) (455 ) Interest capitalized 14 15 47 47 Other financial costs (6 ) (6 ) (20 ) (17 ) Net interest and other financial income (costs) $ (157 ) $ (141 ) $ (465 ) $ (420 )

Inventories (Tables)

Inventories (Tables)	9 Months Ended
	Sep. 30, 2017
Inventory Disclosure [Abstract]
Summary Of Inventories	(In millions) September 30, December 31, Crude oil and refinery feedstocks $ 2,147 $ 2,208 Refined products 2,706 2,810 Materials and supplies 486 485 Merchandise 154 153 Total $ 5,493 $ 5,656

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	9 Months Ended
	Sep. 30, 2017
Property, Plant and Equipment [Abstract]
Summary Of Property, Plant And Equipment	(In millions) September 30, December 31, 2016 (a) Refining & Marketing $ 19,174 $ 18,590 Speedway 5,233 5,078 Midstream 14,489 13,521 Corporate and Other 822 817 Total 39,718 38,006 Less accumulated depreciation 13,682 12,241 Property, plant and equipment, net $ 26,036 $ 25,765 (a) Prior period balances have been recast in connection with the March 1, 2017 contribution of assets to MPLX. See Note 1 for additional information.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2017
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 September 30, 2017 and December 31, 2016 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. September 30, 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 $ 257 $ — $ — $ (257 ) $ — $ 22 Other assets 3 — — N/A 3 — Total assets at fair value $ 260 $ — $ — $ (257 ) $ 3 $ 22 Commodity derivative instruments, liabilities (c) $ 296 $ — $ 5 $ (296 ) $ 5 $ — Embedded derivatives in commodity contracts (c) — — 52 — 52 — Total liabilities at fair value $ 296 $ — $ 57 $ (296 ) $ 57 $ — December 31, 2016 Fair Value Hierarchy (In millions) Level 1 Level 2 Level 3 Netting and Collateral (a) Net Carrying Value on Balance Sheet (b) Collateral Pledged Not Offset Commodity derivative instruments, assets $ 688 $ — $ — $ (688 ) $ — $ 126 Other assets 2 — — N/A 2 — Total assets at fair value $ 690 $ — $ — $ (688 ) $ 2 $ 126 Commodity derivative instruments, liabilities $ 712 $ — $ 6 $ (712 ) $ 6 $ — Embedded derivatives in commodity contracts (c) — — 54 — 54 — Contingent consideration, liability (d) — — 130 N/A 130 — Total liabilities at fair value $ 712 $ — $ 190 $ (712 ) $ 190 $ — (a) Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of September 30, 2017 , cash collateral of $39 million was netted with the mark-to-market derivative liabilities. As of December 31, 2016 , $24 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 $15 million and $13 million classified as current at September 30, 2017 and December 31, 2016 , respectively. (d) Includes $130 million classified as current at December 31, 2016 .
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 Nine Months Ended (In millions) 2017 2016 2017 2016 Beginning balance $ 41 $ 171 $ 190 $ 342 Contingent consideration payment — — (131 ) (200 ) Unrealized and realized losses included in net income 22 6 8 33 Settlements of derivative instruments (6 ) (1 ) (10 ) 1 Ending balance $ 57 $ 176 $ 57 $ 176 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 $ 17 $ 4 $ 8 $ 19 Contingent consideration agreement — 2 1 11 Total $ 17 $ 6 $ 9 $ 30
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 September 30, 2017 and December 31, 2016 , excluding the derivative financial instruments and contingent consideration reported above. September 30, 2017 December 31, 2016 (In millions) Fair Value Carrying Value Fair Value Carrying Value Financial assets: Investments $ 25 $ 2 $ 25 $ 2 Other 25 25 21 21 Total financial assets $ 50 $ 27 $ 46 $ 23 Financial liabilities: Long-term debt (a) $ 13,690 $ 12,544 $ 10,892 $ 10,297 Deferred credits and other liabilities 121 107 121 109 Total financial liabilities $ 13,811 $ 12,651 $ 11,013 $ 10,406 (a) Excludes capital leases and debt issuance costs; however, includes amount classified as debt due within one year.

Derivatives (Tables)

Derivatives (Tables)	9 Months Ended
	Sep. 30, 2017
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 September 30, 2017 and December 31, 2016 : (In millions) September 30, 2017 Balance Sheet Location Asset Liability Commodity derivatives Other current assets $ 257 $ 296 Other current liabilities (a) — 15 Deferred credits and other liabilities (a) — 42 (In millions) December 31, 2016 Balance Sheet Location Asset Liability Commodity derivatives Other current assets $ 688 $ 712 Other current liabilities (a) — 13 Deferred credits and other liabilities (a) — 47 (a) Includes embedded derivatives.
Open Commodity Derivative Contracts	The tables below summarize open commodity derivative contracts for crude oil and refined products as of September 30, 2017 . Position Total Barrels (In thousands) Crude Oil (a) Exchange-traded Long 33,043 Exchange-traded Short (34,428 ) (a ) 94 percent of the exchange-traded contracts expire in the fourth quarter of 2017 . Position Total Gallons (In thousands) Refined Products (a) Exchange-traded Long 316,764 Exchange-traded Short (227,388 ) OTC Short (33,388 ) (a ) 100 percent of the exchange-traded contracts expire in the fourth quarter of 2017 .
Effect of Commodity Derivative Instruments in Statements of Income	The following table summarizes the effect of all commodity derivative instruments in our consolidated statements of income: Gain (Loss) Gain (Loss) (In millions) Three Months Ended September 30, Nine Months Ended September 30, Income Statement Location 2017 2016 2017 2016 Sales and other operating revenues $ (10 ) $ (3 ) $ 8 $ (4 ) Cost of revenues 1 (20 ) (30 ) (91 ) Total $ (9 ) $ (23 ) $ (22 ) $ (95 )

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Outstanding Borrowings	Our outstanding borrowings at September 30, 2017 and December 31, 2016 consisted of the following: (In millions) September 30, 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 — — Term loan agreement due 2019 — 200 Senior notes, 2.700% due December 2018 600 600 Senior notes, 3.400% due December 2020 650 650 Senior notes, 5.125% due March 2021 1,000 1,000 Senior notes, 3.625%, due September 2024 750 750 Senior notes, 6.500%, due March 2041 1,250 1,250 Senior notes, 4.750%, due September 2044 800 800 Senior notes, 5.850% due December 2045 250 250 Senior notes, 5.000%, due September 2054 400 400 MPLX LP: MPLX term loan facility due 2019 — 250 MPLX bank revolving credit facility due 2022 420 — MPLX senior notes, 5.500%, due February 2023 710 710 MPLX senior notes, 4.500%, due July 2023 989 989 MPLX senior notes, 4.875%, due December 2024 1,149 1,149 MPLX senior notes, 4.000%, due February 2025 500 500 MPLX senior notes, 4.875%, due June 2025 1,189 1,189 MarkWest senior notes, 4.500% - 5.500%, due 2023 - 2025 63 63 MPLX senior notes, 4.125%, due March 2027 1,250 — MPLX senior notes, 5.200%, due March 2047 1,000 — Capital lease obligations due 2017-2028 299 319 Total 13,269 11,069 Unamortized debt issuance costs (61 ) (44 ) Unamortized discount (a) (426 ) (453 ) Amounts due within one year (29 ) (28 ) Total long-term debt due after one year $ 12,753 $ 10,544 (a) Includes $386 million and $420 million of unamortized discount as of September 30, 2017 and December 31, 2016 , respectively, related to the difference between the fair value and the principal amount of assumed MarkWest debt.

Supplemental Cash Flow Inform47

Supplemental Cash Flow Information (Tables)	9 Months Ended
	Sep. 30, 2017
Supplemental Cash Flow Elements [Abstract]
Summary of Supplemental Cash Flow Information	Nine Months Ended (In millions) 2017 2016 Net cash provided by operating activities included: Interest paid (net of amounts capitalized) $ 446 $ 400 Net income taxes paid to (refunded from) taxing authorities 383 28 Non-cash investing and financing activities: Contribution of assets to joint venture (a) 337 — (a) MarkWest’s contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. See Note 4 .
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: Nine Months Ended (In millions) 2017 2016 Additions to property, plant and equipment per consolidated statements of cash flows $ 1,928 $ 2,147 Asset retirement expenditures 1 4 Decrease in capital accruals (9 ) (169 ) Total capital expenditures before acquisitions 1,920 1,982 Acquisitions (a) 250 (133 ) Total capital expenditures $ 2,170 $ 1,849 (a) The nine months ended September 30, 2017 reflects primarily the acquisition of the Ozark pipeline. The nine months ended September 30, 2016 reflects adjustments to the fair values of the property, plant and equipment, intangibles and goodwill acquired in connection with the MarkWest Merger.

Accumulated Other Comprehensi48

Accumulated Other Comprehensive Loss (Tables)	9 Months Ended
	Sep. 30, 2017
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, 2015 $ (255 ) $ (70 ) $ 4 $ 3 $ (318 ) Other comprehensive income (loss) before reclassifications (8 ) 1 — — (7 ) Amounts reclassified from accumulated other comprehensive loss: Amortization – prior service credit (a) (35 ) (2 ) — — (37 ) – actuarial loss (a) 28 1 — — 29 – settlement loss (a) 7 — — — 7 Other (b) — — — (1 ) (1 ) Tax effect — — — — — Other comprehensive income (loss) (8 ) — — (1 ) (9 ) Balance as of September 30, 2016 $ (263 ) $ (70 ) $ 4 $ 2 $ (327 ) (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 income (loss) before reclassifications (2 ) — — — (2 ) Amounts reclassified from accumulated other comprehensive loss: Amortization – prior service credit (a) (29 ) (2 ) — — (31 ) – actuarial loss/(gain) (a) 27 (1 ) — — 26 – settlement loss (a) 2 — — — 2 Other (b) — — — (2 ) (2 ) Tax effect — 1 — 1 2 Other comprehensive income (loss) (2 ) (2 ) — (1 ) (5 ) Balance as of September 30, 2017 $ (235 ) $ (9 ) $ 4 $ 1 $ (239 ) (a) These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 19 . (b) This amount was reclassified out of accumulated other comprehensive loss and is included in selling, general and administrative on the consolidated statements of income.

Defined Benefit Pension and O49

Defined Benefit Pension and Other Postretirement Plans (Tables)	9 Months Ended
	Sep. 30, 2017
Retirement Benefits [Abstract]
Components of Net Periodic Benefit Costs	The following summarizes the components of net periodic benefit costs: Three Months Ended September 30, Pension Benefits Other Benefits (In millions) 2017 2016 2017 2016 Components of net periodic benefit cost: Service cost $ 33 $ 29 $ 6 $ 8 Interest cost 19 18 8 9 Expected return on plan assets (25 ) (24 ) — — Amortization – prior service credit (10 ) (12 ) — (1 ) – actuarial loss 9 10 — — – settlement loss 1 4 — — Net periodic benefit cost $ 27 $ 25 $ 14 $ 16 Nine Months Ended September 30, Pension Benefits Other Benefits (In millions) 2017 2016 2017 2016 Components of net periodic benefit cost: Service cost $ 99 $ 86 $ 19 $ 24 Interest cost 56 55 23 26 Expected return on plan assets (75 ) (73 ) — — Amortization – prior service credit (29 ) (35 ) (2 ) (2 ) – actuarial loss/(gain) 27 28 (1 ) 1 – settlement loss 2 7 — — Net periodic benefit cost $ 80 $ 68 $ 39 $ 49

Stock-Based Compensation Plans

Stock-Based Compensation Plans (Tables)	9 Months Ended
	Sep. 30, 2017
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 nine months ended September 30, 2017 : Number of Shares Weighted Average Exercise Price Outstanding at December 31, 2016 9,531,440 $ 28.93 Granted 1,214,112 50.57 Exercised (1,356,217 ) 21.89 Forfeited, canceled or expired (78,386 ) 41.97 Outstanding at September 30, 2017 9,310,949 32.66
Summary of Restricted Stock Award Activity	The following table presents a summary of restricted stock award activity for the nine months ended September 30, 2017 : 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, 2016 1,250,343 $ 41.51 361,117 $ 28.26 Granted 574,602 50.20 28,573 51.94 RS’s Vested/RSU’s Issued (522,454 ) 42.48 (79,635 ) 24.54 Forfeited (83,806 ) 44.29 (13,750 ) 50.20 Outstanding at September 30, 2017 1,218,685 45.00 296,305 30.52
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 nine months ended September 30, 2017 : Number of Units Weighted Average Grant Date Fair Value Outstanding at December 31, 2016 6,255,178 $ 0.78 Granted 2,584,750 0.92 Exercised (1,854,728 ) 0.85 Canceled (99,658 ) 0.78 Outstanding at September 30, 2017 6,885,542 0.81

Supplementary Statistics (Table

Supplementary Statistics (Tables)	9 Months Ended
	Sep. 30, 2017
Text Block [Abstract]
Supplementary Statistics	Supplementary Statistics (Unaudited) Three Months Ended Nine Months Ended (In millions) 2017 2016 2017 2016 Income from Operations by segment Refining & Marketing (a)(b) $ 1,097 $ 252 $ 1,589 $ 1,191 Speedway (b) 209 209 583 569 Midstream (a)(c) 355 310 996 752 Items not allocated to segments: Corporate and other unallocated items (a)(c) (86 ) (65 ) (251 ) (194 ) Pension settlement expenses (1 ) (4 ) (2 ) (7 ) Litigation — — (86 ) — Impairments (d) 2 (267 ) 21 (486 ) Income from operations $ 1,576 $ 435 $ 2,850 $ 1,825 Capital Expenditures and Investments (e) Refining & Marketing $ 198 $ 251 $ 570 $ 756 Speedway 108 71 221 191 Midstream (f) 453 410 2,017 1,179 Corporate and Other (g) 32 29 92 106 Total $ 791 $ 761 $ 2,900 $ 2,232 (a) We revised our operating segment presentation in the first quarter of 2017 in connection with the contribution of certain terminal, pipeline and storage assets to MPLX. The operating results for these assets, which were previously included in the Refining & Marketing segment, are now included in the Midstream segment. Comparable prior period information has been recast to reflect our revised presentation. The results for the pipeline and storage assets were recast effective January 1, 2015, and the results for the terminal assets were recast effective April 1, 2016. Prior to these dates, these assets were not considered businesses and, therefore, there are no financial results from which to recast segment results. (b) The Refining & Marketing and Speedway segments include inventory LCM benefits of $345 million and $25 million , respectively, for the nine months ended September 30, 2016 . (c) Corporate overhead expenses attributable to MPLX are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments. (d) 2017 includes MPC’s share of gains related to the sale of assets remaining from the Sandpiper pipeline project. 2016 relates to impairments of goodwill and equity method investments. (e) Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates. (f) The nine months ended September 30, 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. (g) Includes capitalized interest of $13 million and $15 million for the three months ended September 30, 2017 and 2016 , respectively, and $39 million and $47 million for the nine months ended September 30, 2017 and 2016 , respectively.
Operating Statistics	Supplementary Statistics (Unaudited) Three Months Ended Nine Months Ended 2017 2016 2017 2016 MPC Consolidated Refined Product Sales Volumes (mbpd) (a) 2,357 2,316 2,272 2,274 Refining & Marketing Operating Statistics Refining & Marketing refined product sales volume (mbpd) (b) 2,357 2,307 2,263 2,265 Refining & Marketing gross margin (dollars per barrel) (c)(d) $ 14.14 $ 10.67 $ 12.42 $ 11.11 Crude oil capacity utilization percent (e) 102 100 96 95 Refinery throughputs (mbpd): (f) Crude oil refined 1,845 1,791 1,741 1,708 Other charge and blendstocks 172 135 176 156 Total 2,017 1,926 1,917 1,864 Sour crude oil throughput percent 57 59 61 60 WTI-priced crude oil throughput percent 23 20 20 20 Refined product yields (mbpd): (f) Gasoline 939 907 910 908 Distillates 673 647 627 616 Propane 38 38 35 35 Feedstocks and special products 298 253 285 245 Heavy fuel oil 45 43 36 36 Asphalt 67 70 64 58 Total 2,060 1,958 1,957 1,898 Refinery direct operating costs (dollars per barrel): (g) Planned turnaround and major maintenance $ 1.20 $ 1.62 $ 1.69 $ 1.72 Depreciation and amortization 1.34 1.42 1.44 1.46 Other manufacturing (h) 3.83 4.01 4.10 4.03 Total $ 6.37 $ 7.05 $ 7.23 $ 7.21 Refining & Marketing Operating Statistics By Region - Gulf Coast Refinery throughputs (mbpd): (i) Crude oil refined 1,123 1,073 1,041 1,057 Other charge and blendstocks 217 185 219 199 Total 1,340 1,258 1,260 1,256 Sour crude oil throughput percent 69 72 75 73 WTI-priced crude oil throughput percent 14 8 10 7 Refined product yields (mbpd): (i) Gasoline 538 511 525 530 Distillates 438 411 393 407 Propane 25 27 25 26 Feedstocks and special products 326 289 310 283 Heavy fuel oil 31 30 24 24 Asphalt 19 17 17 15 Total 1,377 1,285 1,294 1,285 Refinery direct operating costs (dollars per barrel): (g) Planned turnaround and major maintenance $ 0.90 $ 2.05 $ 1.86 $ 1.87 Depreciation and amortization 1.05 1.14 1.15 1.13 Other manufacturing (h) 3.52 3.70 3.81 3.62 Total $ 5.47 $ 6.89 $ 6.82 $ 6.62 Supplementary Statistics (Unaudited) Three Months Ended Nine Months Ended 2017 2016 2017 2016 Refining & Marketing Operating Statistics By Region – Midwest Refinery throughputs (mbpd): (i) Crude oil refined 722 718 700 651 Other charge and blendstocks 35 39 31 37 Total 757 757 731 688 Sour crude oil throughput percent 38 39 41 39 WTI-priced crude oil throughput percent 38 39 34 41 Refined product yields (mbpd): (i) Gasoline 401 396 385 378 Distillates 235 236 234 209 Propane 14 13 11 11 Feedstocks and special products 50 51 47 40 Heavy fuel oil 15 13 13 12 Asphalt 48 53 47 43 Total 763 762 737 693 Refinery direct operating costs (dollars per barrel): (g) Planned turnaround and major maintenance $ 1.60 $ 0.72 $ 1.22 $ 1.26 Depreciation and amortization 1.72 1.72 1.80 1.90 Other manufacturing (h) 3.96 4.04 4.19 4.29 Total $ 7.28 $ 6.48 $ 7.21 $ 7.45 Speedway Operating Statistics (j) Convenience stores at period-end 2,734 2,773 Gasoline and distillate sales (millions of gallons) 1,464 1,575 4,332 4,605 Gasoline and distillate gross margin (dollars per gallon) (k) $ 0.1772 $ 0.1773 $ 0.1727 $ 0.1668 Merchandise sales (in millions) $ 1,295 $ 1,338 $ 3,693 $ 3,777 Merchandise gross margin (in millions) $ 374 $ 386 $ 1,065 $ 1,085 Merchandise gross margin percent 28.9 % 28.9 % 28.8 % 28.7 % Same store gasoline sales volume (period over period) (3.1 %) (0.6 %) (1.6 %) 0.2 % Same store merchandise sales (period over period) (l) 0.3 % 4.0 % 1.5 % 3.0 % Midstream Operating Statistics Crude oil and refined product pipeline throughputs (mbpd) (m) 3,562 3,113 3,299 2,953 Terminal throughput (mbpd) (n) 1,496 1,517 1,470 1,510 Gathering system throughput (MMcf/d) (o) 3,729 3,306 3,415 3,313 Natural gas processed (MMcf/d) (o) 6,581 5,906 6,336 5,691 C2 (ethane) + NGLs (natural gas liquids) fractionated (mbpd) (o) 397 348 384 330 (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) Excludes LCM inventory valuation adjustments. Comparable prior period information for gross margin has been recast in connection with the contribution of certain pipeline assets to MPLX on March 1, 2017. (e) Based on calendar day capacity, which is an annual average that includes downtime for planned maintenance and other normal operating activities. (f) Excludes inter-refinery volumes of 80 mbpd and 89 mbpd for the three months ended September 30, 2017 and 2016 , respectively, and 74 mbpd and 80 mbpd for the nine months ended September 30, 2017 and 2016 , respectively. (g) Per barrel of total refinery throughputs. (h) Includes utilities, labor, routine maintenance and other operating costs. (i) Includes inter-refinery transfer volumes. (j) Third quarter and year-to-date 2017 operating statistics do not reflect any information for the 41 travel centers contributed to PFJ Southeast, whereas they are reflected in the third quarter and year-to-date 2016 operating statistics. (k) Excludes LCM inventory valuation adjustments. The price paid by consumers less the cost of refined products, including transportation, consumer excise taxes and bankcard processing fees, divided by gasoline and distillate sales volume. (l) Excludes cigarettes. (m) Includes common-carrier pipelines and private pipelines contributed to MPLX, excluding equity method investments. (n) Includes the results of the terminal assets contributed to MPLX from the date the assets became a business, April 1, 2016. (o) Includes amounts related to unconsolidated equity method investments on a 100 percent basis.

MPLX LP (Detail)

MPLX LP (Detail) - MPLX LP	Sep. 30, 2017
Noncontrolling Interest [Line Items]
Ownership percentage of general partner interest	100.00%
Public's ownership interest in MPLX (in percentage)	69.60%
General Partner and Limited Partner
Noncontrolling Interest [Line Items]
MPC's partnership interest in MPLX (in percentage)	30.40%
General Partner
Noncontrolling Interest [Line Items]
MPC's partnership interest in MPLX (in percentage)	2.00%

MPLX LP - Reorganization Transa

MPLX LP - Reorganization Transactions (Details) - MPLX LP - USD ($) shares in Millions, $ in Millions	Sep. 01, 2017	Mar. 01, 2017	Sep. 01, 2016	Mar. 31, 2016
General partners' contributed capital			$ 225
Limited Partner
Units issued, number of units	19	13	7	23
General Partner and Limited Partner
Increase in ownership percentage by MPC			1.00%

MPLX LP - Private Placement of

MPLX LP - Private Placement of Preferred Units (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	May 13, 2016	Sep. 30, 2017	Sep. 30, 2016
Noncontrolling Interest [Line Items]
Issuance of MPLX LP redeemable preferred units		$ 0	$ 984
MPLX LP | Series A Convertible Preferred Units
Noncontrolling Interest [Line Items]
Sale of units (in number of preferred units)	30.8
Preferred units, dividend rate, percentage	6.50%
Issuance of MPLX LP redeemable preferred units	$ 984
Preferred units, distribution rate, per-dollar-amount	$ 0.528125
Preferred units, description	The MPLX Preferred Units are convertible into MPLX common units on a one for one basis after three years, at the purchasers’ option, and after four years at MPLX’s option, subject to certain conditions.
MPLX LP | Series A Convertible Preferred Units | Preferred Units
Noncontrolling Interest [Line Items]
Units issued, price per unit	$ 32.50

MPLX LP - Dropdowns to MPLX (De

MPLX LP - Dropdowns to MPLX (Details) - MPLX LP - USD ($) shares in Thousands, $ in Millions	Sep. 01, 2017	Mar. 01, 2017	Sep. 01, 2016	Mar. 31, 2016
Noncontrolling Interest [Line Items]
Total fair value of consideration transferred	$ 1,050	$ 2,000
Limited Partner
Noncontrolling Interest [Line Items]
Units issued, number of units	19,000	13,000	7,000	23,000
Equity interest issued, value assigned	$ 630	$ 504		$ 600
General Partner
Noncontrolling Interest [Line Items]
Units issued, number of units	378	264		460
Cash and Cash Equivalents
Noncontrolling Interest [Line Items]
Payments to acquire business, gross	$ 420	$ 1,500

MPLX LP - Public Offerings (Det

MPLX LP - Public Offerings (Details) - MPLX LP - USD ($) $ in Millions	Sep. 01, 2017	Mar. 01, 2017	Sep. 30, 2017	Feb. 10, 2017	Dec. 31, 2016
Cash and Cash Equivalents
Noncontrolling Interest [Line Items]
Payments to acquire business, gross	$ 420	$ 1,500
Senior Notes | MPLX senior notes, 4.125%, due March 2027
Noncontrolling Interest [Line Items]
Long-term debt, gross			$ 1,250	$ 1,250	$ 0
Debt instrument, interest rate			4.125%	4.125%
Senior Notes | MPLX senior notes, 5.200%, due March 2047
Noncontrolling Interest [Line Items]
Long-term debt, gross			$ 1,000	$ 1,000	$ 0
Debt instrument, interest rate			5.20%	5.20%

MPLX LP - ATM Program (Details)

MPLX LP - ATM Program (Details) - USD ($) shares in Millions, $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Noncontrolling Interest [Line Items]
Net proceeds from issuance of MPLX LP common limited partners units	$ 473	$ 499
MPLX LP | ATM Program
Noncontrolling Interest [Line Items]
Net proceeds from issuance of MPLX LP common limited partners units	473
Remaining authorized issuance amount	$ 1,740
MPLX LP | ATM Program | Limited Partners Common Units
Noncontrolling Interest [Line Items]
Sale of units (in number of common units)	14

MPLX LP - Noncontrolling Intere

MPLX LP - Noncontrolling Interest (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Impact from equity transactions of MPLX, net of tax	$ 447	$ 429
Additional Paid-in Capital
Increase (decrease) in MPC's additional paid in capital for the issuance of MPLX LP common units to the public	25	(43)
Increase in MPC's additional paid in capital for the issuance of MPLX LP common units and general partner units to MPC	113	0
Net transfers (to) from noncontrolling interests	138	(43)
Tax impact	(26)	(70)
Impact from equity transactions of MPLX, net of tax	$ 112	$ (113)

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 60

Acquisitions and Investments - Revenue and Income from Operations (Details) - Ozark Pipeline - USD ($) $ in Millions	3 Months Ended	7 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Sales and other operating revenues (including consumer excise taxes)	$ 19	$ 45
Income from operations	$ 6	$ 17

Acquisitions and Investments 61

Acquisitions and Investments - Formation of Travel Plaza Joint Venture (Details) $ in Millions	3 Months Ended	9 Months Ended
	Dec. 31, 2016USD ($)Store	Sep. 30, 2017USD ($)	[1]	Sep. 30, 2016USD ($)
Schedule of Equity Method Investments [Line Items]
Contribution of assets to joint venture		$ 337		$ 0
PFJ Southeast
Schedule of Equity Method Investments [Line Items]
Contribution of assets to joint venture	$ 273
PFJ Southeast | Property, Plant and Equipment
Schedule of Equity Method Investments [Line Items]
Contribution of assets to joint venture	203
PFJ Southeast | Goodwill
Schedule of Equity Method Investments [Line Items]
Contribution of assets to joint venture	62
PFJ Southeast | Inventories
Schedule of Equity Method Investments [Line Items]
Contribution of assets to joint venture	$ 8
PFJ Southeast | Speedway
Schedule of Equity Method Investments [Line Items]
Number of travel plazas | Store	41
PFJ Southeast | Pilot Flying J
Schedule of Equity Method Investments [Line Items]
Number of travel plazas | Store	82
[1]	MarkWest’s contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. See Note 4.

Acquisitions and Investments 62

Acquisitions and Investments - Marine Investments (Details) $ in Millions	1 Months Ended	9 Months Ended	12 Months Ended		16 Months Ended
	May 31, 2016USD ($)	Sep. 30, 2017Joint_venturevessel	Dec. 31, 2016vessel	Dec. 31, 2015vessel	Dec. 31, 2016USD ($)vessel	May 01, 2016	Sep. 30, 2015
Crowley Coastal Partners
Schedule of Equity Method Investments [Line Items]
Cash paid to acquire equity method investments | $	$ 48				$ 189
Equity method investments, ownership percentage		50.00%
Crowley Ocean Partners
Schedule of Equity Method Investments [Line Items]
Cash paid to acquire equity method investments | $					$ 141
Equity method investments, ownership percentage		50.00%				50.00%	50.00%
Number of vessels | vessel			2	2	4
Crowley Blue Water Partners
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		50.00%
Number of vessels | vessel		3
Crowley Maritime Corporation
Schedule of Equity Method Investments [Line Items]
Number of joint ventures | Joint_venture		2
Crowley Maritime Corporation | Crowley Blue Water Partners
Schedule of Equity Method Investments [Line Items]
Percentage of partners interest contributed	100.00%

Acquisitions and Investments 63

Acquisitions and Investments - Investment in Pipeline Company (Details) bbl / d in Thousands, $ in Millions	Feb. 15, 2017USD ($)Quarterly_reporting_periodbbl / d	Sep. 30, 2017USD ($)
Schedule of Equity Method Investments [Line Items]
IDRs forfeited per quarter	$ 1.6
Number of quarters IDRs forfeited | Quarterly_reporting_period	12
Prorated IDRs forfeited	$ 0.8
MarEn Bakken
Schedule of Equity Method Investments [Line Items]
Cash paid to acquire equity method investments		$ 500
Bakken Pipeline System
Schedule of Equity Method Investments [Line Items]
Crude oil throughput | bbl / d	470
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%
MPLX LP | Bakken Pipeline System
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	9.20%
MPC & Enbridge Energy Partners | MarEn Bakken
Schedule of Equity Method Investments [Line Items]
Cash paid to acquire equity method investments	$ 2,000
MPC & Enbridge Energy Partners | Bakken Pipeline System
Schedule of Equity Method Investments [Line Items]
Percentage of ownership interest in joint venture acquired	36.75%

Acquisitions and Investments 64

Acquisitions and Investments - Formation of Gathering and Processing Joint Venture (Details) bbl / d in Thousands, $ in Millions	Jan. 01, 2017USD ($)bbl / d	Sep. 30, 2017USD ($)		Sep. 30, 2016USD ($)
Schedule of Equity Method Investments [Line Items]
Contribution of assets to joint venture		$ 337	[1]	$ 0
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		86.00%
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 4.

Variable Interest Entities (Det

Variable Interest Entities (Details) bbl / d in Thousands, $ in Millions	Sep. 30, 2017USD ($)	Jan. 01, 2017bbl / d	Dec. 31, 2016USD ($)
Variable Interest Entity [Line Items]
Equity method investments	$ 4,769		$ 3,827
Crowley Coastal Partners
Variable Interest Entity [Line Items]
VIE, maximum loss exposure, amount	$ 493
Equity method investments, ownership percentage	50.00%
MarkWest Utica EMG
Variable Interest Entity [Line Items]
Equity method investments, ownership percentage	56.00%
Equity method investments	$ 2,200
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	$ 220
Ohio Fractionation
Variable Interest Entity [Line Items]
Capacity | bbl / d		20
Sherwood Midstream Holdings
Variable Interest Entity [Line Items]
Equity method investments, ownership percentage	86.00%
Equity method investments	$ 163
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	Sep. 30, 2017	Dec. 31, 2016	May 01, 2016	Sep. 30, 2015
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%		50.00%	50.00%
Explorer
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	25.00%
Illinois Extension Pipeline
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	35.00%
LOCAP
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	59.00%
LOOP
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	51.00%
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	86.00%
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		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Related Party Transaction [Line Items]
Sales to related parties	$ 157	$ 2	$ 458	$ 5
PFJ Southeast
Related Party Transaction [Line Items]
Sales to related parties	155	0	451	0
Other equity method investees
Related Party Transaction [Line Items]
Sales to related parties	$ 2	$ 2	$ 7	$ 5

Related Party Transactions - Ot

Related Party Transactions - Other Income From Related Parties (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Related Party Transaction [Line Items]
Other income from related parties	$ 13	$ 12	$ 39	$ 31
MarkWest Utica EMG
Related Party Transaction [Line Items]
Other income from related parties	5	5	13	12
Ohio Gathering
Related Party Transaction [Line Items]
Other income from related parties	4	5	12	12
Other equity method investees
Related Party Transaction [Line Items]
Other income from related parties	$ 4	$ 2	$ 14	$ 7

Related Party Transactions - Pu

Related Party Transactions - Purchases from Related Parties (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Related Party Transaction [Line Items]
Purchases from related parties	$ 148	$ 128	$ 420	$ 359
Crowley Blue Water Partners
Related Party Transaction [Line Items]
Purchases from related parties	16	16	44	22
Crowley Ocean Partners
Related Party Transaction [Line Items]
Purchases from related parties	20	15	59	32
Explorer
Related Party Transaction [Line Items]
Purchases from related parties	7	4	7	12
Illinois Extension Pipeline
Related Party Transaction [Line Items]
Purchases from related parties	26	27	75	82
LOCAP
Related Party Transaction [Line Items]
Purchases from related parties	6	6	17	18
LOOP
Related Party Transaction [Line Items]
Purchases from related parties	14	14	53	42
TAAE
Related Party Transaction [Line Items]
Purchases from related parties	22	9	53	29
TACE
Related Party Transaction [Line Items]
Purchases from related parties	9	10	34	39
TAME
Related Party Transaction [Line Items]
Purchases from related parties	20	23	58	67
Other equity method investees
Related Party Transaction [Line Items]
Purchases from related parties	$ 8	$ 4	$ 20	$ 16

Related Party Transactions - Re

Related Party Transactions - Receivables From Related Parties (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Current receivables from related parties	$ 40	$ 45
MarkWest Utica EMG
Related Party Transaction [Line Items]
Current receivables from related parties	2	2
Ohio Gathering
Related Party Transaction [Line Items]
Current receivables from related parties	2	2
PFJ Southeast
Related Party Transaction [Line Items]
Current receivables from related parties	32	40
Other equity method investees
Related Party Transaction [Line Items]
Current receivables from related parties	$ 4	$ 1

Related Party Transactions - Pa

Related Party Transactions - Payables To Related Parties (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Payables to related parties	$ 64	$ 53
Illinois Extension Pipeline
Related Party Transaction [Line Items]
Payables to related parties	9	9
LOCAP
Related Party Transaction [Line Items]
Payables to related parties	2	2
LOOP
Related Party Transaction [Line Items]
Payables to related parties	5	6
MarkWest Utica EMG
Related Party Transaction [Line Items]
Payables to related parties	30	24
TAAE
Related Party Transaction [Line Items]
Payables to related parties	2	2
TACE
Related Party Transaction [Line Items]
Payables to related parties	1	4
TAME
Related Party Transaction [Line Items]
Payables to related parties	2	4
Other equity method investees
Related Party Transaction [Line Items]
Payables to related parties	$ 13	$ 2

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		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Basic earnings per share:
Net income attributable to MPC	$ 903	$ 145	$ 1,416	$ 947
Income allocated to participating securities	0	0	1	1
Income available to common stockholders – basic	$ 903	$ 145	$ 1,415	$ 946
Weighted average common shares outstanding (in shares)	504	527	514	528
Basic (in USD per share)	$ 1.79	$ 0.28	$ 2.75	$ 1.79
Diluted earnings per share:
Net income attributable to MPC	$ 903	$ 145	$ 1,416	$ 947
Income allocated to participating securities	0	0	1	1
Income available to common stockholders – diluted	$ 903	$ 145	$ 1,415	$ 946
Weighted average common shares outstanding (in shares)	504	527	514	528
Effect of dilutive securities (in shares)	4	3	4	3
Weighted average common shares, including dilutive effect (in shares)	508	530	518	531
Diluted (in USD per share)	$ 1.77	$ 0.27	$ 2.73	$ 1.78

Income Per Common Share - Anti-

Income Per Common Share - Anti-dilutive Shares (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Stock Based Compensation Expense [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares issued under stock-based compensation plans	1	3	1	3

Equity - Additional Information

Equity - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	May 31, 2017
Stock repurchase program, authorized amount						$ 3,000
Stock repurchase program, remaining authorized repurchase amount		$ 3,940		$ 3,940
Number of shares repurchased		8,000,000	1,000,000	31,000,000	4,000,000
Cash paid for shares repurchased		$ 452	$ 51	$ 1,622	$ 177
Scenario, Forecast
Number of shares repurchased	985,400
Cash paid for shares repurchased	$ 55

Equity - Share Repurchases (Det

Equity - Share Repurchases (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Equity [Abstract]
Number of shares repurchased	8	1	31	4
Cash paid for shares repurchased	$ 452	$ 51	$ 1,622	$ 177
Effective average cost per delivered share	$ 53.85	$ 42.76	$ 52.16	$ 41.14

Segment Information - Additiona

Segment Information - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2017Segmentrefinery
Segment Reporting [Abstract]
Number of reportable segments | Segment	3
Number of refineries | refinery	7

Segment Information - Income Fr

Segment Information - Income From Operations Attributable To Operating Segments (Detail) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016		Sep. 30, 2017		Sep. 30, 2016
Segment Reporting Information [Line Items]
Revenues		$ 19,053	$ 16,616		$ 53,220		$ 46,179
Sales to related parties		157	2		458		5
Income from operations		1,576	435		2,850		1,825
Income from equity method investments		84	(208)		224		(236)
Depreciation and amortization		517	507		1,574		1,497
Capital expenditures and investments	[1]	791	761		2,900		2,232
Inventory market valuation adjustment		0	0		0		(370)
MarEn Bakken
Segment Reporting Information [Line Items]
Cash paid to acquire equity method investments					500
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues	[2]	3,274	3,145		9,381		8,785
Operating Segments
Segment Reporting Information [Line Items]
Revenues		22,484	19,763		63,059		54,969
Income from operations		1,661	771		3,168		2,512
Income from equity method investments		83	59	[3]	203		120	[3]
Depreciation and amortization	[3]	503	493		1,530		1,452
Capital expenditures and investments	[4]	759	732		2,808	[5]	2,126
Cash paid to acquire equity method investments		53	69		730	[6]	383	[6]
Refining & Marketing
Segment Reporting Information [Line Items]
Revenues		13,573	11,284		37,485		31,192
Sales to related parties		155	2		452		5
Inventory market valuation adjustment							345
Refining & Marketing | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues		2,904	2,798		8,302		7,872
Refining & Marketing | Operating Segments
Segment Reporting Information [Line Items]
Revenues		16,632	14,084		46,239		39,069
Income from operations		1,097	252		1,589	[7]	1,191	[8]
Income from equity method investments		6	8		10		10
Depreciation and amortization		266	267		805		801
Capital expenditures and investments		198	251		570		756
Speedway
Segment Reporting Information [Line Items]
Revenues		4,895	4,848		14,070		13,663
Sales to related parties		2	0		6		0
Inventory market valuation adjustment							25
Speedway | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues		1	1		3		2
Speedway | Operating Segments
Segment Reporting Information [Line Items]
Revenues		4,898	4,849		14,079		13,665
Income from operations		209	209		583		569	[8]
Income from equity method investments		20	0		54		0
Depreciation and amortization		68	71		197		203
Capital expenditures and investments		108	71		221		191
Midstream
Segment Reporting Information [Line Items]
Revenues		585	484		1,665		1,324
Sales to related parties		0	0		0		0
Midstream | Ozark Pipeline
Segment Reporting Information [Line Items]
Capital expenditures and investments					220
Midstream | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues		369	346		1,076		911
Midstream | Operating Segments
Segment Reporting Information [Line Items]
Revenues		954	830		2,741		2,235
Income from operations	[9]	355	310		996	[7]	752
Income from equity method investments		57	51		139		110
Depreciation and amortization		169	155		528		448
Capital expenditures and investments		453	410		2,017	[5]	1,179
Reportable Segment
Segment Reporting Information [Line Items]
Revenues		$ 19,053	$ 16,616		$ 53,220		$ 46,179
[1]	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
[2]	Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties
[3]	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.
[4]	Capital expenditures include changes in capital accruals, acquisitions (including any goodwill) and investments in affiliates.
[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 nine months ended September 30, 2017.
[6]	The nine months ended September 30, 2017 includes an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system. The nine months ended September 30, 2016 includes an adjustment of $143 million to the fair value of equity method investments acquired in connection with the MarkWest Merger
[7]	We revised our operating segment presentation in the first quarter of 2017 in connection with the contribution of certain terminal, pipeline and storage assets to MPLX. The operating results for these assets, which were previously included in the Refining & Marketing segment, are now included in the Midstream segment. Comparable prior period information has been recast to reflect our revised presentation. The results for the pipeline and storage assets were recast effective January 1, 2015, and the results for the terminal assets were recast effective April 1, 2016. Prior to these dates, these assets were not considered businesses and, therefore, there are no financial results from which to recast segment results.
[8]	The Refining & Marketing and Speedway segments include inventory LCM benefits of $345 million and $25 million, respectively, for the nine months ended September 30, 2016
[9]	Corporate overhead expenses attributable to MPLX are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments.

Segment Information - Reconcili

Segment Information - Reconciliation Of Segment Income From Operations To Income Before Income Taxes (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017		Sep. 30, 2016
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations		$ 1,576	$ 435	$ 2,850		$ 1,825
Impairment expense		0	0	0		130
Net interest and other financial income (costs)		157	141	465		420
Income before income taxes		1,419	294	2,385		1,405
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations		1,661	771	3,168		2,512
Corporate and Other
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations	[1]	(86)	(65)	(251)	[2]	(194)
Segment Reconciling Items
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pension settlement expenses		(1)	(4)	(2)		(7)
Litigation		0	0	(86)	[3]	0
Impairment expense	[4]	$ 2	$ (267)	$ 21		$ (486)
[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.
[2]	We revised our operating segment presentation in the first quarter of 2017 in connection with the contribution of certain terminal, pipeline and storage assets to MPLX. The operating results for these assets, which were previously included in the Refining & Marketing segment, are now included in the Midstream segment. Comparable prior period information has been recast to reflect our revised presentation. The results for the pipeline and storage assets were recast effective January 1, 2015, and the results for the terminal assets were recast effective April 1, 2016. Prior to these dates, these assets were not considered businesses and, therefore, there are no financial results from which to recast segment results.
[3]	See Note 21 for further information on litigation matters.
[4]	2017 includes MPC’s share of gains related to the sale of assets remaining from the Sandpiper pipeline project. 2016 relates to impairments of goodwill and equity method investments.

Segment Information - Reconci79

Segment Information - Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017		Sep. 30, 2016
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures [Line Items]
Capital expenditures and investments	[1]	$ 791	$ 761	$ 2,900		$ 2,232
Plus items not allocated to segments:
Capital expenditures	[2]	738	692	2,170		1,849
MarkWest | Adjustments
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures [Line Items]
Less: Investments in equity method investees						143
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]	759	732	2,808	[4]	2,126
Less: Investments in equity method investees		53	69	730	[5]	383	[5]
Corporate and Other
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures [Line Items]
Capital expenditures and investments	[6]	32	29	92		106
Plus items not allocated to segments:
Corporate and Other		19	14	53		59
Capitalized interest		$ 13	$ 15	$ 39		$ 47
[1]	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
[2]	Capital expenditures include changes in capital accruals. See Note 17 for a reconciliation of total capital expenditures to additions to property, plant and equipment as reported in the consolidated statements of cash flows.
[3]	Capital expenditures include changes in capital accruals, acquisitions (including any goodwill) and investments in affiliates.
[4]	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 nine months ended September 30, 2017.
[5]	The nine months ended September 30, 2017 includes an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system. The nine months ended September 30, 2016 includes an adjustment of $143 million to the fair value of equity method investments acquired in connection with the MarkWest Merger
[6]	Includes capitalized interest of $13 million and $15 million for the three months ended September 30, 2017 and 2016, respectively, and $39 million and $47 million for the nine months ended September 30, 2017 and 2016, respectively.

Other Items - Net Interest And

Other Items - Net Interest And Other Financial Income (Costs) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other Income and Expenses [Abstract]
Interest income	$ 7	$ 3	$ 16	$ 5
Interest expense	(172)	(153)	(508)	(455)
Interest capitalized	14	15	47	47
Other financial costs	(6)	(6)	(20)	(17)
Net interest and other financial income (costs)	$ (157)	$ (141)	$ (465)	$ (420)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Combined federal, state and foreign income tax rate	29.00%	26.00%	30.00%	34.00%
Statutory rate applied to income before income taxes		35.00%	35.00%	35.00%
Unrecognized benefits	$ 19		$ 19

Inventories - Summary Of Invent

Inventories - Summary Of Inventories (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Crude oil and refinery feedstocks	$ 2,147	$ 2,208
Refined products	2,706	2,810
Materials and supplies	486	485
Merchandise	154	153
Total	$ 5,493	$ 5,656

Inventories - Additional Inform

Inventories - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2017USD ($)
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	Sep. 30, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 39,718	$ 38,006
Less accumulated depreciation	13,682	12,241
Net property, plant and equipment	26,036	25,765
Operating Segments | Refining & Marketing
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	19,174	18,590	[1]
Operating Segments | Speedway
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	5,233	5,078
Operating Segments | Midstream
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	14,489	13,521	[1]
Corporate and Other
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 822	$ 817
[1]	Prior period balances have been recast in connection with the March 1, 2017 contribution of assets to MPLX. See Note 1 for additional information.

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Accounted for at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions		Sep. 30, 2017		Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash collateral netted with derivative liabilities		$ 39		$ 24
Contingent consideration, current				130
Embedded derivatives in commodity contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Embedded derivatives, current		15		13
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - netting and collateral		(257)		(688)
Commodity derivative instruments, assets - collateral pledged not offset		22		126
Other assets		3		2
Total assets at fair value		3		2
Commodity derivative instruments, liabilities - netting and collateral		(296)		(712)
Commodity derivative instruments, liabilities - collateral pledged not offset		0		0
Contingent consideration, liability				130
Total liabilities at fair value		57		190
Fair Value, Measurements, Recurring | Commodity derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - netting and collateral	[1]	(257)		(688)
Commodity derivative instruments, assets - net carrying value on balance sheet	[2]	0		0
Commodity derivative instruments, assets - collateral pledged not offset		22		126
Commodity derivative instruments, liabilities - netting and collateral	[1]	(296)		(712)
Commodity derivative instruments, liabilities - net carrying value on balance sheet	[2]	5		6
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]	52		54
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		2
Total assets at fair value		260		690
Contingent consideration, liability				0
Total liabilities at fair value		296		712
Fair Value, Measurements, Recurring | Level 1 | Commodity derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - gross		257		688
Commodity derivative instruments, liabilities - gross		296		712
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
Contingent consideration, liability				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
Contingent consideration, liability	[3]			130
Total liabilities at fair value		57		190
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		5	[4]	6
Fair Value, Measurements, Recurring | Level 3 | Embedded derivatives in commodity contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, liabilities - gross	[4]	$ 52		$ 54
[1]	Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of September 30, 2017, cash collateral of $39 million was netted with the mark-to-market derivative liabilities. As of December 31, 2016, $24 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]	Includes $130 million classified as current at December 31, 2016.
[4]	Level 3 includes $15 million and $13 million classified as current at September 30, 2017 and December 31, 2016, respectively.

Fair Value Measurements - Recur

Fair Value Measurements - Recurring Narrative (Detail) - USD ($)	Apr. 12, 2017	Sep. 30, 2017	Sep. 30, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration payment, financing activities		$ 89,000,000	$ 164,000,000
Galveston Bay Refinery and Related Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration payment	$ 131,000,000
Commodity derivatives | Level 3 | Ethanol prices | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward commodity price		0.27
Commodity derivatives | Level 3 | Ethanol prices | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward commodity price		$ 1.22
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		50.00%
Probability of renewal second term		75.00%

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		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 41	$ 171	$ 190	$ 342
Contingent consideration payment	0	0	(131)	(200)
Unrealized and realized losses included in net income	22	6	8	33
Settlements of derivative instruments	(6)	(1)	(10)	1
Ending balance	$ 57	$ 176	$ 57	$ 176

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		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
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:	$ 17	$ 6	$ 9	$ 30
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:	17	4	8	19
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	$ 2	$ 1	$ 11

Fair Value Measurements - Finan

Fair Value Measurements - Financial Instruments at Fair Value, Excluding Derivative Financial Instruments and Contingent Consideration (Detail) - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016
Fair Value
Financial assets:
Investments		$ 25	$ 25
Other		25	21
Total financial assets		50	46
Financial liabilities:
Long-term debt	[1]	13,690	10,892
Deferred credits and other liabilities		121	121
Total financial liabilities		13,811	11,013
Carrying Value
Financial assets:
Investments		2	2
Other		25	21
Total financial assets		27	23
Financial liabilities:
Long-term debt	[1]	12,544	10,297
Deferred credits and other liabilities		107	109
Total financial liabilities		$ 12,651	$ 10,406
[1]	Excludes capital leases and debt issuance costs; however, includes amount classified as debt due within one year.

Derivatives - Classification of

Derivatives - Classification of Gross Fair Values of Derivative Instruments, Excluding Cash Collateral (Detail) - Commodity derivatives - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016
Other current assets
Derivatives, Fair Value [Line Items]
Asset		$ 257	$ 688
Liability		296	712
Other current liabilities(a)
Derivatives, Fair Value [Line Items]
Asset		0	0
Liability	[1]	15	13
Deferred credits and other liabilities
Derivatives, Fair Value [Line Items]
Asset		0	0
Liability	[1]	$ 42	$ 47
[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
	Sep. 30, 2017bbl
Derivative [Line Items]
Percentage of derivative contracts expiring in the period	94.00%
Derivative contract expiration date	Dec. 31, 2017
Long
Derivative [Line Items]
Notional contracts (in thousands of Total Barrels)	33,043	[1]
Short
Derivative [Line Items]
Notional contracts (in thousands of Total Barrels)	34,428	[1]
[1]	of the exchange-traded contracts expire in the fourth quarter of 2017.

Derivatives - Open Commodity 92

Derivatives - Open Commodity Derivative Contracts - Refined Products (Detail) - Refined Products gal in Thousands	3 Months Ended
	Sep. 30, 2017gal
Exchange Traded
Derivative [Line Items]
Percentage of derivative contracts expiring in the period	100.00%
Derivative contract expiration date	Dec. 31, 2017
Exchange Traded | Long
Derivative [Line Items]
Notional contracts (in thousands of Total Gallons)	316,764	[1]
Exchange Traded | Short
Derivative [Line Items]
Notional contracts (in thousands of Total Gallons)	227,388	[1]
Over the Counter | Short
Derivative [Line Items]
Notional contracts (in thousands of Total Gallons)	33,388
[1]	of the exchange-traded contracts expire in the fourth quarter of 2017.

Derivatives - Effect of Commodi

Derivatives - Effect of Commodity Derivative Instruments in Statements of Income (Detail) - Commodity derivatives - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	$ (9)	$ (23)	$ (22)	$ (95)
Sales and other operating revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	(10)	(3)	8	(4)
Cost of revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	$ 1	$ (20)	$ (30)	$ (91)

Debt - Outstanding Borrowings (

Debt - Outstanding Borrowings (Detail) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2017	Feb. 10, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Commercial paper		$ 0		$ 0
Total		13,269		11,069
Unamortized debt issuance costs		(61)		(44)
Unamortized discount	[1]	(426)		(453)
Amounts due within one year		(29)		(28)
Total long-term debt due after one year		12,753		10,544
MPLX LP
Debt Instrument [Line Items]
Amounts due within one year		(1)		(1)
Total long-term debt due after one year		6,848		4,422
Senior Notes | MPLX LP | MarkWest
Debt Instrument [Line Items]
Long-term debt, gross		63		63
Unamortized discount		(386)		(420)
Capital Lease Obligations | Subsidiaries
Debt Instrument [Line Items]
Capital lease obligations		$ 299		319
Debt instrument maturity year, start		Jan. 1, 2017
Debt instrument maturity year, end		Dec. 31, 2028
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
Trade receivables securitization facility due July 2019
Debt Instrument [Line Items]
Long-term debt, gross		$ 0
Trade receivables securitization facility due July 2019 | Secured Debt
Debt Instrument [Line Items]
Long-term debt, gross		$ 0		0
Trade receivables securitization facility due July 2019 | Secured Debt | Subsidiaries
Debt Instrument [Line Items]
Line of credit facility, expiration date		Jul. 19, 2019
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
Term loan agreement due 2019 | Unsecured Debt
Debt Instrument [Line Items]
Long-term debt, gross		$ 0		200
Line of credit facility, expiration date		Sep. 24, 2019
Senior notes, 2.700% due December 2018 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 600		600
Debt instrument, maturity date		Dec. 14, 2018
Debt instrument, interest rate		2.70%
Senior notes, 3.400% due December 2020 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 650		650
Debt instrument, maturity date		Dec. 15, 2020
Debt instrument, interest rate		3.40%
Senior notes, 5.125% due March 2021 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,000		1,000
Debt instrument, maturity date		Mar. 1, 2021
Debt instrument, interest rate		5.125%
Senior notes, 3.625%, due September 2024 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 750		750
Debt instrument, maturity date		Sep. 15, 2024
Debt instrument, interest rate		3.625%
Senior notes, 6.500%, due March 2041 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,250		1,250
Debt instrument, maturity date		Mar. 1, 2041
Debt instrument, interest rate		6.50%
Senior notes, 4.750%, due September 2044 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 800		800
Debt instrument, maturity date		Sep. 15, 2044
Debt instrument, interest rate		4.75%
Senior notes, 5.850% due December 2045 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 250		250
Debt instrument, maturity date		Dec. 15, 2045
Debt instrument, interest rate		5.85%
Senior notes, 5.000%, due September 2054 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 400		400
Debt instrument, maturity date		Sep. 15, 2054
Debt instrument, interest rate		5.00%
MPLX term loan facility due 2019 | Unsecured Debt | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross		$ 0		250
Line of credit facility, expiration date		Nov. 20, 2019
MPLX bank revolving credit facility due 2022 | Line of Credit | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross		$ 420		0
Line of credit facility, expiration date		Jul. 21, 2022
MPLX senior notes, 5.500%, due February 2023 | Senior Notes | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross		$ 710		710
Debt instrument, maturity date		Feb. 15, 2023
Debt instrument, interest rate		5.50%
MPLX senior notes, 5.500%, due February 2023 | Senior Notes | MPLX LP | MarkWest
Debt Instrument [Line Items]
Debt instrument, maturity date		Feb. 15, 2023
Debt instrument, interest rate		5.50%
MPLX senior notes, 4.500%, due July 2023 | Senior Notes | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross		$ 989		989
Debt instrument, maturity date		Jul. 15, 2023
Debt instrument, interest rate		4.50%
MPLX senior notes, 4.500%, due July 2023 | Senior Notes | MPLX LP | MarkWest
Debt Instrument [Line Items]
Debt instrument, maturity date		Jul. 15, 2023
Debt instrument, interest rate		4.50%
MPLX senior notes, 4.875%, due December 2024 | Senior Notes | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,149		1,149
Debt instrument, maturity date		Dec. 1, 2024
Debt instrument, interest rate		4.875%
MPLX senior notes, 4.875%, due December 2024 | Senior Notes | MPLX LP | MarkWest
Debt Instrument [Line Items]
Debt instrument, maturity date		Dec. 1, 2024
Debt instrument, interest rate		4.875%
MPLX senior notes, 4.000%, due February 2025 | Senior Notes | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross		$ 500		500
Debt instrument, maturity date		Feb. 15, 2025
Debt instrument, interest rate		4.00%
MPLX senior notes, 4.875%, due June 2025 | Senior Notes | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,189		1,189
Debt instrument, maturity date		Jun. 1, 2025
Debt instrument, interest rate		4.875%
MPLX senior notes, 4.875%, due June 2025 | Senior Notes | MPLX LP | MarkWest
Debt Instrument [Line Items]
Debt instrument, maturity date		Jun. 1, 2025
Debt instrument, interest rate		4.875%
MPLX senior notes, 4.125%, due March 2027 | Senior Notes | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,250	$ 1,250	0
Debt instrument, maturity date		Mar. 1, 2027
Debt instrument, interest rate		4.125%	4.125%
MPLX senior notes, 5.200%, due March 2047 | Senior Notes | MPLX LP
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,000	$ 1,000	$ 0
Debt instrument, maturity date		Mar. 1, 2047
Debt instrument, interest rate		5.20%	5.20%
[1]	Includes $386 million and $420 million of unamortized discount as of September 30, 2017 and December 31, 2016, respectively, related to the difference between the fair value and the principal amount of assumed MarkWest debt.

Debt - Narrative (Details)

Debt - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Debt Instrument [Line Items]
Commercial paper – issued	$ 300	$ 1,063
Commercial paper - repayments	300	$ 1,063
Commercial paper	0		$ 0
Trade receivables securitization facility due July 2019
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) - USD ($) $ in Millions	Jul. 21, 2017	Jul. 20, 2016	Sep. 30, 2017	Dec. 31, 2016
Bank revolving credit facility due 2020
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 2,500
Debt instrument, term		4 years
Bank revolving credit facility due 2020 | Letter of Credit
Debt Instrument [Line Items]
Long-term line of credit			$ 0
Bank revolving credit facility due 2020 | Line of Credit
Debt Instrument [Line Items]
Long-term debt, gross			0
364-day bank revolving credit facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 1,000	$ 1,000
Debt instrument, term	364 days	364 days
364-day bank revolving credit facility | Line of Credit
Debt Instrument [Line Items]
Long-term debt, gross			0	$ 0
Bank revolving credit facility due 2022
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 2,500
Debt instrument, term	5 years
Bank revolving credit facility due 2022 | Line of Credit
Debt Instrument [Line Items]
Long-term debt, gross			$ 0	$ 0

Debt - MPC Term Loan Agreement

Debt - MPC Term Loan Agreement (Details) $ in Millions	Mar. 31, 2017USD ($)
Term loan agreement due 2019
Debt Instrument [Line Items]
Repayments of long-term debt	$ 200

Debt - MPLX Credit Agreement (D

Debt - MPLX Credit Agreement (Details) - MPLX LP - USD ($) $ in Millions	Jul. 21, 2017	Jul. 19, 2017	Oct. 27, 2015	Sep. 30, 2017	Dec. 31, 2016
MPLX bank revolving credit facility due 2022
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 2,250		$ 2,000
Debt instrument, term	5 years		5 years
Borrowings				$ 420
Interest rate during period				2.70%
Repayments				$ 0
Remaining borrowing capacity				1,830
MPLX bank revolving credit facility due 2022 | Letter of Credit
Debt Instrument [Line Items]
Long-term line of credit				3
MPLX bank revolving credit facility due 2022 | Line of Credit
Debt Instrument [Line Items]
Long-term debt, gross				$ 420	$ 0
MPLX term loan facility due 2019
Debt Instrument [Line Items]
Repayments of long-term debt		$ 250

Debt - MPLX Senior Notes (Detai

Debt - MPLX Senior Notes (Details) - MPLX LP - USD ($) $ in Millions	Sep. 01, 2017	Mar. 01, 2017	Sep. 30, 2017	Feb. 10, 2017	Dec. 31, 2016
Cash and Cash Equivalents
Debt Instrument [Line Items]
Payments to acquire business, gross	$ 420	$ 1,500
Senior Notes
Debt Instrument [Line Items]
Net proceeds			$ 2,220
Senior Notes | MPLX senior notes, 4.125%, due March 2027
Debt Instrument [Line Items]
Long-term debt, gross			$ 1,250	$ 1,250	$ 0
Debt instrument, interest rate			4.125%	4.125%
Senior Notes | MPLX senior notes, 5.200%, due March 2047
Debt Instrument [Line Items]
Long-term debt, gross			$ 1,000	$ 1,000	$ 0
Debt instrument, interest rate			5.20%	5.20%

Supplemental Cash Flow Infor100

Supplemental Cash Flow Information - Summary of Supplemental Cash Flow Information (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017		Sep. 30, 2016
Net cash provided by operating activities included:
Interest paid (net of amounts capitalized)	$ 446		$ 400
Net income taxes paid to (refunded from) taxing authorities	383		28
Non-cash investing and financing activities:
Contribution of assets to joint venture	$ 337	[1]	$ 0
[1]	MarkWest’s contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. See Note 4.

Supplemental Cash Flow Infor101

Supplemental Cash Flow Information - Reconciliation of Additions to Property, Plant and Equipment to Total Capital Expenditures (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Supplemental Cash Flow Elements [Abstract]
Additions to property, plant and equipment per consolidated statements of cash flows				$ 1,928	$ 2,147
Asset retirement expenditures				1	4
Decrease in capital accruals				(9)	(169)
Total capital expenditures before acquisitions				1,920	1,982
Acquisitions	[1]			250	(133)
Capital expenditures	[2]	$ 738	$ 692	$ 2,170	$ 1,849
[1]	The nine months ended September 30, 2017 reflects primarily the acquisition of the Ozark pipeline. The nine months ended September 30, 2016 reflects adjustments to the fair values of the property, plant and equipment, intangibles and goodwill acquired in connection with the MarkWest Merger.
[2]	Capital expenditures include changes in capital accruals. See Note 17 for a reconciliation of total capital expenditures to additions to property, plant and equipment as reported in the consolidated statements of cash flows.

Accumulated Other Comprehens102

Accumulated Other Comprehensive Loss - Changes in Accumulated Other Comprehensive Loss by Component (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance				$ (234)	$ (318)
Other comprehensive loss before reclassifications				(2)	(7)
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit				(31)	(37)
Amortization - actuarial loss				26	29
Amortization - settlement loss				2	7
Other				(2)	(1)
Tax effect				2	0
Other comprehensive loss		$ (3)	$ (6)	(5)	(9)
Ending balance		(239)	(327)	(239)	(327)
Accumulated Defined Benefit Plans Adjustment | Pension Benefits
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance				(233)	(255)
Other comprehensive loss before reclassifications				(2)	(8)
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit	[1]			(29)	(35)
Amortization - actuarial loss	[1]			27	28
Amortization - settlement loss	[1]			2	7
Tax effect				0	0
Other comprehensive loss				(2)	(8)
Ending balance		(235)	(263)	(235)	(263)
Accumulated Defined Benefit Plans Adjustment | Other Benefits
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance				(7)	(70)
Other comprehensive loss before reclassifications				0	1
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit	[1]			(2)	(2)
Amortization - actuarial loss	[1]			(1)	1
Amortization - settlement loss				0	0
Tax effect				1	0
Other comprehensive loss				(2)	0
Ending balance		(9)	(70)	(9)	(70)
Gain on Cash Flow Hedge
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance				4	4
Other comprehensive loss before reclassifications				0	0
Amounts reclassified from accumulated other comprehensive loss:
Tax effect				0	0
Other comprehensive loss				0	0
Ending balance		4	4	4	4
Workers Compensation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance				2	3
Other comprehensive loss before reclassifications				0	0
Amounts reclassified from accumulated other comprehensive loss:
Other	[2]			(2)	(1)
Tax effect				1	0
Other comprehensive loss				(1)	(1)
Ending balance		$ 1	$ 2	$ 1	$ 2
[1]	These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 19.
[2]	This amount was reclassified out of accumulated other comprehensive loss and is included in selling, general and administrative on the consolidated statements of income.

Defined Benefit Pension and 103

Defined Benefit Pension and Other Postretirement Plans - Components of Net Periodic Benefit Costs (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Pension Benefits
Components of net periodic benefit cost:
Service cost	$ 33	$ 29	$ 99	$ 86
Interest cost	19	18	56	55
Expected return on plan assets	(25)	(24)	(75)	(73)
Amortization – prior service credit	(10)	(12)	(29)	(35)
Amortization – actuarial loss (gain)	9	10	27	28
Amortization - settlement loss	1	4	2	7
Net periodic benefit cost	27	25	80	68
Other Benefits
Components of net periodic benefit cost:
Service cost	6	8	19	24
Interest cost	8	9	23	26
Expected return on plan assets	0	0	0	0
Amortization – prior service credit	0	(1)	(2)	(2)
Amortization – actuarial loss (gain)	0	0	(1)	1
Amortization - settlement loss	0	0	0	0
Net periodic benefit cost	$ 14	$ 16	$ 39	$ 49

Defined Benefit Pension and 104

Defined Benefit Pension and Other Postretirement Plans - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2017USD ($)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 120
Other Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Benefits paid	7
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Benefits paid	$ 23

Stock-Based Compensation Pla105

Stock-Based Compensation Plans - Summary of Stock Option Award Activity (Detail) - Stock Options	9 Months Ended
	Sep. 30, 2017$ / sharesshares
Number of Shares
Outstanding, beginning balance | shares	9,531,440
Granted | shares	1,214,112
Exercised | shares	(1,356,217)
Forfeited, canceled or expired | shares	(78,386)
Outstanding, ending balance | shares	9,310,949
Weighted Average Exercise Price
Outstanding, beginning balance (in USD per share) | $ / shares	$ 28.93
Granted (in USD per share) | $ / shares	50.57
Exercised (in USD per share) | $ / shares	21.89
Forfeited, canceled or expired (in USD per share) | $ / shares	41.97
Outstanding, ending balance (in USD per share) | $ / shares	$ 32.66

Stock-Based Compensation Pla106

Stock-Based Compensation Plans - Narrative (Detail)	9 Months Ended
	Sep. 30, 2017$ / shares
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date fair value (in USD per share)	$ 13.42
Performance Unit Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in USD per share)	$ 0.92

Stock-Based Compensation Pla107

Stock-Based Compensation Plans - Summary of Restricted Stock Award Activity (Detail)	9 Months Ended
	Sep. 30, 2017$ / sharesshares
Restricted Stock
Number of Shares
Outstanding, beginning balance | shares	1,250,343
Granted | shares	574,602
RS’s Vested/RSU’s Issued | shares	(522,454)
Forfeited | shares	(83,806)
Outstanding, ending balance | shares	1,218,685
Weighted Average Grant Date Fair Value
Outstanding, beginning balance (in USD per share) | $ / shares	$ 41.51
Granted (in USD per share) | $ / shares	50.20
RS's Vested/RSU's Issued (in USD per share) | $ / shares	42.48
Forfeited (in USD per share) | $ / shares	44.29
Outstanding, ending balance (in USD per share) | $ / shares	$ 45
Restricted Stock Units
Number of Shares
Outstanding, beginning balance | shares	361,117
Granted | shares	28,573
RS’s Vested/RSU’s Issued | shares	(79,635)
Forfeited | shares	(13,750)
Outstanding, ending balance | shares	296,305
Weighted Average Grant Date Fair Value
Outstanding, beginning balance (in USD per share) | $ / shares	$ 28.26
Granted (in USD per share) | $ / shares	51.94
RS's Vested/RSU's Issued (in USD per share) | $ / shares	24.54
Forfeited (in USD per share) | $ / shares	50.20
Outstanding, ending balance (in USD per share) | $ / shares	$ 30.52

Stock-Based Compensation Pla108

Stock-Based Compensation Plans - Summary of Performance Unit Awards (Detail) - Performance Unit Awards	9 Months Ended
	Sep. 30, 2017$ / sharesshares
Number of Units
Outstanding, beginning balance | shares	6,255,178
Granted | shares	2,584,750
Exercised | shares	(1,854,728)
Canceled | shares	(99,658)
Outstanding, ending balance | shares	6,885,542
Weighted Average Grant Date Fair Value
Outstanding, beginning balance (in USD per share) | $ / shares	$ 0.78
Granted (in USD per share) | $ / shares	0.92
Exercised (in USD per share) | $ / shares	0.85
Canceled (in USD per share) | $ / shares	0.78
Outstanding, ending balance (in USD per share) | $ / shares	$ 0.81

Commitments and Contingencies (

Commitments and Contingencies (Detail)	9 Months Ended
	Sep. 30, 2017
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	Sep. 30, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Accrued liabilities for remediation	$ 117	$ 132
Receivables for recoverable costs	$ 45	$ 58

Commitments and Contingencie111

Commitments and Contingencies - MarkWest Environmental Proceeding (Details) - Pending Litigation - MarkWest Liberty Midstream Pipeline Launcher/Receiver Site [Member] $ in Millions	9 Months Ended
	Sep. 30, 2017USD ($)
Cash
Loss Contingencies [Line Items]
Damages sought	$ 1.2
Other Liabilities
Loss Contingencies [Line Items]
Damages sought	1.6
Scenario, Previously Reported [Member] | Cash
Loss Contingencies [Line Items]
Damages sought	2.4
Scenario, Previously Reported [Member] | Other Liabilities
Loss Contingencies [Line Items]
Damages sought	$ 3.6

Commitments and Contingencie112

Commitments and Contingencies - Other Lawsuits (Details) $ in Millions	9 Months Ended
	Sep. 30, 2017USD ($)lawsuit
Galveston Bay Refinery Fire
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit	4
Litigation settlement expense	$ 86
Emergency Pricing And Consumer Protection Laws | Pending Litigation
Loss Contingencies [Line Items]
Plaintiff	Commonwealth of Kentucky
Damages sought	$ 89
Loss contingency, period of occurrence	during September and October 2005

Commitments and Contingencie113

Commitments and Contingencies - Guarantees (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	May 01, 2016	Sep. 30, 2015
Indemnification Agreement | Marathon Oil Companies
Loss Contingencies [Line Items]
Guarantee obligation current carrying value	$ 2
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]
Maximum potential undiscounted payments	$ 160
Line of credit facility, expiration date	Dec. 31, 2037
Centennial | Guarantee of Indebtedness of Others | Financial Guarantee
Loss Contingencies [Line Items]
Maximum potential undiscounted payments	$ 22
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%	50.00%	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	$ 139

Commitments and Contingencie114

Commitments and Contingencies - Contractual Commitments and Contingencies (Details) $ in Millions	9 Months Ended
	Sep. 30, 2017USD ($)
Commitments and Contingencies Disclosure [Abstract]
Contractual commitments to acquire property, plant and equipment and advance funds to equity method investees	$ 694

Supplementary Statistics - Supp

Supplementary Statistics - Supplementary Statistics (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017		Sep. 30, 2016
Supplementary Statistics [Line Items]
Income from operations		$ 1,576	$ 435	$ 2,850		$ 1,825
Impairment expense		0	0	0		130
Capital expenditures and investments	[1]	791	761	2,900		2,232
Inventory market valuation adjustment		0	0	0		(370)
MarEn Bakken
Supplementary Statistics [Line Items]
Cash paid to acquire equity method investments				500
Refining & Marketing
Supplementary Statistics [Line Items]
Inventory market valuation adjustment						345
Speedway
Supplementary Statistics [Line Items]
Inventory market valuation adjustment						25
Midstream | Ozark Pipeline
Supplementary Statistics [Line Items]
Capital expenditures and investments				220
Operating Segments
Supplementary Statistics [Line Items]
Income from operations		1,661	771	3,168		2,512
Capital expenditures and investments	[2]	759	732	2,808	[3]	2,126
Cash paid to acquire equity method investments		53	69	730	[4]	383	[4]
Operating Segments | Refining & Marketing
Supplementary Statistics [Line Items]
Income from operations		1,097	252	1,589	[5]	1,191	[6]
Capital expenditures and investments		198	251	570		756
Operating Segments | Speedway
Supplementary Statistics [Line Items]
Income from operations		209	209	583		569	[6]
Capital expenditures and investments		108	71	221		191
Operating Segments | Midstream
Supplementary Statistics [Line Items]
Income from operations	[7]	355	310	996	[5]	752
Capital expenditures and investments		453	410	2,017	[3]	1,179
Corporate and Other
Supplementary Statistics [Line Items]
Income from operations	[8]	(86)	(65)	(251)	[5]	(194)
Capital expenditures and investments	[9]	32	29	92		106
Capitalized interest		13	15	39		47
Segment Reconciling Items
Supplementary Statistics [Line Items]
Pension settlement expenses		(1)	(4)	(2)		(7)
Litigation		0	0	(86)	[10]	0
Impairment expense	[11]	$ 2	$ (267)	$ 21		$ (486)
[1]	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.
[2]	Capital expenditures include changes in capital accruals, acquisitions (including any goodwill) and investments in affiliates.
[3]	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 nine months ended September 30, 2017.
[4]	The nine months ended September 30, 2017 includes an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system. The nine months ended September 30, 2016 includes an adjustment of $143 million to the fair value of equity method investments acquired in connection with the MarkWest Merger
[5]	We revised our operating segment presentation in the first quarter of 2017 in connection with the contribution of certain terminal, pipeline and storage assets to MPLX. The operating results for these assets, which were previously included in the Refining & Marketing segment, are now included in the Midstream segment. Comparable prior period information has been recast to reflect our revised presentation. The results for the pipeline and storage assets were recast effective January 1, 2015, and the results for the terminal assets were recast effective April 1, 2016. Prior to these dates, these assets were not considered businesses and, therefore, there are no financial results from which to recast segment results.
[6]	The Refining & Marketing and Speedway segments include inventory LCM benefits of $345 million and $25 million, respectively, for the nine months ended September 30, 2016
[7]	Corporate overhead expenses attributable to MPLX are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments.
[8]	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.
[9]	Includes capitalized interest of $13 million and $15 million for the three months ended September 30, 2017 and 2016, respectively, and $39 million and $47 million for the nine months ended September 30, 2017 and 2016, respectively.
[10]	See Note 21 for further information on litigation matters.
[11]	2017 includes MPC’s share of gains related to the sale of assets remaining from the Sandpiper pipeline project. 2016 relates to impairments of goodwill and equity method investments.

Supplementary Statistics - Oper

Supplementary Statistics - Operating Statistics (Detail) bbl / d in Thousands, gal in Millions, CFPD in Millions, $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2017USD ($)Storebbl / dCFPD$ / bbl$ / galgal		Sep. 30, 2016USD ($)Storebbl / dCFPD$ / bbl$ / galgal	Sep. 30, 2017USD ($)Storebbl / dCFPD$ / bbl$ / galgal		Sep. 30, 2016USD ($)Storebbl / dCFPD$ / bbl$ / galgal
Operating Statistics [Line Items ]
MPC Consolidated Refined Product Sales Volumes (thousands of barrels per day)	[1]	2,357		2,316	2,272		2,274
Refining & Marketing
Refining & Marketing Operating Statistics
Refining & Marketing refined product sales volume (thousands of barrels per day)	[2]	2,357		2,307	2,263		2,265
Refining & Marketing gross margin (dollars per barrel) | $ / bbl	[3],[4]	14.14		10.67	12.42		11.11
Crude oil capacity utilization percent	[5]	102.00%		100.00%	96.00%		95.00%
Refinery throughputs (thousands of barrels per day)	[6]	2,017		1,926	1,917		1,864
Sour crude oil throughput percent		57.00%		59.00%	61.00%		60.00%
WTI-priced crude oil throughput percent		23.00%		20.00%	20.00%		20.00%
Refined product yields (thousands of barrels per day)	[6]	2,060		1,958	1,957		1,898
Inter-refinery transfers		80		89	74		80
Refinery direct operating costs (dollars per barrel):
Planned turnaround and major maintenance | $ / bbl	[7]	1.20		1.62	1.69		1.72
Depreciation and amortization | $ / bbl	[7]	1.34		1.42	1.44		1.46
Other manufacturing | $ / bbl	[7],[8]	3.83		4.01	4.10		4.03
Total | $ / bbl	[7]	6.37		7.05	7.23		7.21
Refining & Marketing | Crude oil refined
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[6]	1,845		1,791	1,741		1,708
Refining & Marketing | Other charge and blendstocks
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[6]	172		135	176		156
Refining & Marketing | Gasoline
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[6]	939		907	910		908
Refining & Marketing | Distillates
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[6]	673		647	627		616
Refining & Marketing | Propane
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[6]	38		38	35		35
Refining & Marketing | Feedstocks and special products
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[6]	298		253	285		245
Refining & Marketing | Heavy fuel oil
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[6]	45		43	36		36
Refining & Marketing | Asphalt
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[6]	67		70	64		58
Refining & Marketing | Gulf Coast:
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[9]	1,340		1,258	1,260		1,256
Sour crude oil throughput percent		69.00%		72.00%	75.00%		73.00%
WTI-priced crude oil throughput percent		14.00%		8.00%	10.00%		7.00%
Refined product yields (thousands of barrels per day)	[9]	1,377		1,285	1,294		1,285
Refinery direct operating costs (dollars per barrel):
Planned turnaround and major maintenance | $ / bbl	[7]	0.90		2.05	1.86		1.87
Depreciation and amortization | $ / bbl	[7]	1.05		1.14	1.15		1.13
Other manufacturing | $ / bbl	[7],[8]	3.52		3.70	3.81		3.62
Total | $ / bbl	[7]	5.47		6.89	6.82		6.62
Refining & Marketing | Gulf Coast: | Crude oil refined
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[9]	1,123		1,073	1,041		1,057
Refining & Marketing | Gulf Coast: | Other charge and blendstocks
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[9]	217		185	219		199
Refining & Marketing | Gulf Coast: | Gasoline
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[9]	538		511	525		530
Refining & Marketing | Gulf Coast: | Distillates
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[9]	438		411	393		407
Refining & Marketing | Gulf Coast: | Propane
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[9]	25		27	25		26
Refining & Marketing | Gulf Coast: | Feedstocks and special products
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[9]	326		289	310		283
Refining & Marketing | Gulf Coast: | Heavy fuel oil
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[9]	31		30	24		24
Refining & Marketing | Gulf Coast: | Asphalt
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[9]	19		17	17		15
Refining & Marketing | Midwest:
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[9]	757		757	731		688
Sour crude oil throughput percent		38.00%		39.00%	41.00%		39.00%
WTI-priced crude oil throughput percent		38.00%		39.00%	34.00%		41.00%
Refined product yields (thousands of barrels per day)	[9]	763		762	737		693
Refinery direct operating costs (dollars per barrel):
Planned turnaround and major maintenance | $ / bbl	[7]	1.60		0.72	1.22		1.26
Depreciation and amortization | $ / bbl	[7]	1.72		1.72	1.80		1.90
Other manufacturing | $ / bbl	[7],[8]	3.96		4.04	4.19		4.29
Total | $ / bbl	[7]	7.28		6.48	7.21		7.45
Refining & Marketing | Midwest: | Crude oil refined
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[9]	722		718	700		651
Refining & Marketing | Midwest: | Other charge and blendstocks
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[9]	35		39	31		37
Refining & Marketing | Midwest: | Gasoline
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[9]	401		396	385		378
Refining & Marketing | Midwest: | Distillates
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[9]	235		236	234		209
Refining & Marketing | Midwest: | Propane
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[9]	14		13	11		11
Refining & Marketing | Midwest: | Feedstocks and special products
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[9]	50		51	47		40
Refining & Marketing | Midwest: | Heavy fuel oil
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[9]	15		13	13		12
Refining & Marketing | Midwest: | Asphalt
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[9]	48		53	47		43
Speedway
Speedway Operating Statistics(j)
Convenience stores at period-end | Store		2,734	[10]	2,773	2,734	[10]	2,773
Gasoline and distillate sales (millions of gallons) | gal		1,464	[10]	1,575	4,332	[10]	4,605
Gasoline and distillate gross margin (dollars per gallon) | $ / gal	[11]	0.1772	[10]	0.1773	0.1727	[10]	0.1668
Merchandise sales (in millions) | $		$ 1,295	[10]	$ 1,338	$ 3,693	[10]	$ 3,777
Merchandise gross margin (in millions) | $		$ 374	[10]	$ 386	$ 1,065	[10]	$ 1,085
Merchandise margin percent		28.90%	[10]	28.90%	28.80%	[10]	28.70%
Same store gasoline sales volume (period over period) percentage		(3.10%)	[10]	(0.60%)	(1.60%)	[10]	0.20%
Merchandise sales excluding cigarettes (period over period) percentage	[12]	0.30%	[10]	4.00%	1.50%	[10]	3.00%
Midstream
Midstream Operating Statistics
Crude oil and refined product pipeline throughputs (thousands of barrels per day)	[13]	3,562		3,113	3,299		2,953
Terminal throughput (thousands of barrels per day)	[14]	1,496		1,517	1,470		1,510
Gathering system throughput (MMcf/d) | CFPD	[15]	3,729		3,306	3,415		3,313
Natural gas processed (MMcf/d) | CFPD	[15]	6,581		5,906	6,336		5,691
C2 and NGLs fractionated (thousands barrels per day)	[15]	397		348	384		330
[1]	Total average daily volumes of refined product sales to wholesale, branded and retail customers.
[2]	Includes intersegment sales.
[3]	Excludes LCM inventory valuation adjustments. Comparable prior period information for gross margin has been recast in connection with the contribution of certain pipeline assets to MPLX on March 1, 2017.
[4]	Sales revenue less cost of refinery inputs and purchased products, divided by total refinery throughputs.
[5]	Based on calendar day capacity, which is an annual average that includes downtime for planned maintenance and other normal operating activities.
[6]	Excludes inter-refinery volumes of 80 mbpd and 89 mbpd for the three months ended September 30, 2017 and 2016, respectively, and 74 mbpd and 80 mbpd for the nine months ended September 30, 2017 and 2016, respectively.
[7]	Per barrel of total refinery throughputs.
[8]	Includes utilities, labor, routine maintenance and other operating costs.
[9]	Includes inter-refinery transfer volumes.
[10]	Third quarter and year-to-date 2017 operating statistics do not reflect any information for the 41 travel centers contributed to PFJ Southeast, whereas they are reflected in the third quarter and year-to-date 2016 operating statistics.
[11]	Excludes LCM inventory valuation adjustments. The price paid by consumers less the cost of refined products, including transportation, consumer excise taxes and bankcard processing fees, divided by gasoline and distillate sales volume.
[12]	Excludes cigarettes.
[13]	Includes common-carrier pipelines and private pipelines contributed to MPLX, excluding equity method investments.
[14]	Includes the results of the terminal assets contributed to MPLX from the date the assets became a business, April 1, 2016.
[15]	Includes amounts related to unconsolidated equity method investments on a 100 percent basis.