Marathon Petroleum (MPC) 10-K 28 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2017	Feb. 16, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus (Q1,Q2,Q3,FY)	FY
Trading Symbol	MPC
Entity Registrant Name	Marathon Petroleum Corp
Entity Central Index Key	1,510,295
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		476,059,729
Entity Public Float			$ 26.4

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues and other income:
Sales and other operating revenues (including consumer excise taxes)	$ 74,104	$ 63,277	$ 72,045
Sales to related parties	629	62	6
Income (loss) from equity method investments	306	(185)	88
Net gain on disposal of assets	10	32	7
Other income	320	178	112
Total revenues and other income	75,369	63,364	72,258
Costs and expenses:
Cost of revenues (excludes items below)	58,760	49,170	55,583
Purchases from related parties	570	509	308
Inventory market valuation adjustment	0	(370)	370
Consumer excise taxes	7,759	7,506	7,692
Impairment expense	0	130	144
Depreciation and amortization	2,114	2,001	1,502
Selling, general and administrative expenses	1,743	1,605	1,576
Other taxes	454	435	391
Total costs and expenses	71,400	60,986	67,566
Income from operations	3,969	2,378	4,692
Net interest and other financial income (costs)	(625)	(556)	(318)
Income before income taxes	3,344	1,822	4,374
(Benefit) provision for income taxes	(460)	609	1,506
Net income	3,804	1,213	2,868
Less net income (loss) attributable to:
Redeemable noncontrolling interest	65	41	0
Noncontrolling interests	307	(2)	16
Net income attributable to MPC	$ 3,432	$ 1,174	$ 2,852
Basic:
Net income attributable to MPC per share	$ 6.76	$ 2.22	$ 5.29
Weighted average shares outstanding (in shares)	507	528	538
Diluted:
Net income attributable to MPC per share	$ 6.70	$ 2.21	$ 5.26
Weighted average shares outstanding (in shares)	512	530	542
Dividends paid (in USD per share)	$ 1.52	$ 1.36	$ 1.14

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 3,804	$ 1,213	$ 2,868
Defined benefit postretirement and post-employment plans:
Actuarial changes, net of tax of $17, $69 and $21	29	115	34
Prior service costs, net of tax of ($16), ($18) and ($24)	(26)	(31)	(39)
Other comprehensive income (loss)	3	84	(5)
Comprehensive income	3,807	1,297	2,863
Less comprehensive income (loss) attributable to:
Redeemable noncontrolling interest	65	41	0
Noncontrolling interests	307	(2)	16
Comprehensive income attributable to MPC	$ 3,435	$ 1,258	$ 2,847

Consolidated Statements of Com4

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Actuarial changes, tax	$ 17	$ 69	$ 21
Prior service costs, tax	$ (16)	$ (18)	$ (24)

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents (MPLX: $5 and $234, respectively)	$ 3,011	$ 887
Receivables, less allowance for doubtful accounts of $11 and $12 (MPLX: $299 and $304, respectively)	4,695	3,617
Inventories (MPLX: $65 and $55, respectively)	5,550	5,656
Other current assets (MPLX: $29 and $33, respectively)	145	241
Total current assets	13,401	10,401
Equity method investments (MPLX: $4,010 and $2,471, respectively)	4,787	3,827
Property, plant and equipment, net (MPLX: $12,187 and $11,408, respectively)	26,443	25,765
Goodwill (MPLX: $2,245 and $2,245, respectively)	3,586	3,587
Other noncurrent assets (MPLX: $479 and $506, respectively)	830	833
Total assets	49,047	44,413
Current liabilities:
Accounts payable (MPLX: $621 and $541, respectively)	8,297	5,593
Payroll and benefits payable (MPLX: $1 and $1, respectively)	591	530
Consumer excise taxes payable (MPLX: $3 and $3, respectively)	501	464
Accrued taxes (MPLX: $35 and $35, respectively)	169	153
Debt due within one year (MPLX: $1 and $1, respectively)	624	28
Other current liabilities (MPLX: $130 and $81, respectively)	296	378
Total current liabilities	10,478	7,146
Long-term debt (MPLX: $6,945 and $4,422, respectively)	12,322	10,544
Deferred income taxes (MPLX: $5 and $6, respectively)	2,654	3,861
Defined benefit postretirement plan obligations	1,099	1,055
Deferred credits and other liabilities (MPLX: $230 and $189, respectively)	666	604
Total liabilities	27,219	23,210
Commitments and contingencies (see Note 25)
Redeemable noncontrolling interest	1,000	1,000
MPC stockholders’ equity:
Preferred stock, no shares issued and outstanding (par value 0.01 per share, 30 million shares authorized)	0	0
Common stock:
Issued – 734 million and 731 million shares (par value 0.01 per share, 1 billion shares authorized)	7	7
Held in treasury, at cost – 248 million and 203 million shares	(9,869)	(7,482)
Additional paid-in capital	11,262	11,060
Retained earnings	12,864	10,206
Accumulated other comprehensive loss	(231)	(234)
Total MPC stockholders’ equity	14,033	13,557
Noncontrolling interests	6,795	6,646
Total equity	20,828	20,203
Total liabilities, redeemable noncontrolling interest and equity	$ 49,047	$ 44,413

Consolidated MPLX Balance Sheet

Consolidated MPLX Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents	$ 3,011	$ 887
Receivables, less allowance for doubtful accounts	4,695	3,617
Inventories	5,550	5,656
Other current assets	145	241
Equity method investments	4,787	3,827
Property, plant and equipment, net	26,443	25,765
Goodwill	3,586	3,587
Other noncurrent assets	830	833
Liabilities
Accounts payable	8,297	5,593
Payroll and benefits payable	591	530
Consumer excise taxes payable	501	464
Accrued taxes	169	153
Debt due within one year	624	28
Other current liabilities	296	378
Total long-term debt due after one year	12,322	10,544
Defined benefit postretirement plan obligations	1,099	1,055
Deferred credits and other liabilities	666	604
MPLX LP
Assets
Cash and cash equivalents	5	234
Receivables, less allowance for doubtful accounts	299	304
Inventories	65	55
Other current assets	29	33
Equity method investments	4,010	2,471
Property, plant and equipment, net	12,187	11,408
Goodwill	2,245	2,245
Other noncurrent assets	479	506
Liabilities
Accounts payable	621	541
Payroll and benefits payable	1	1
Consumer excise taxes payable	3	3
Accrued taxes	35	35
Debt due within one year	1	1
Other current liabilities	130	81
Total long-term debt due after one year	6,945	4,422
Deferred income taxes	5	6
Defined benefit postretirement plan obligations	0	0
Deferred credits and other liabilities	$ 230	$ 189

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 11	$ 12
Preferred stock:
Shares issued	0	0
Shares outstanding	0	0
Par value	$ 0.01
Shares authorized	30,000,000
Common stock:
Shares issued	734,000,000	731,000,000
Par value	$ 0.01
Shares authorized	1,000,000,000
Treasury stock	(248,000,000)	(203,000,000)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net income	$ 3,804	$ 1,213	$ 2,868
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred financing costs and debt discount	64	61	16
Impairment expense	0	130	144
Depreciation and amortization	2,114	2,001	1,502
Inventory market valuation adjustment	0	(370)	370
Pension and other postretirement benefits, net	47	9	80
Deferred income taxes	(1,233)	394	134
Net gain on disposal of assets	(10)	(32)	(7)
(Income) loss from equity method investments	(306)	185	(88)
Distributions from equity method investments	388	291	113
Changes in the fair value of derivative instruments	116	(41)	4
Changes in:
Current receivables	(1,093)	(674)	1,292
Inventories	106	(70)	80
Current accounts payable and accrued liabilities	2,814	985	(2,400)
All other, net	(202)	(87)	(35)
Net cash provided by operating activities	6,609	3,995	4,073
Investing activities:
Additions to property, plant and equipment	(2,732)	(2,892)	(1,998)
Acquisitions, net of cash acquired	(249)	0	(1,218)
Disposal of assets	79	101	21
Investments – acquisitions, loans and contributions	(805)	(288)	(331)
Investments—redemptions, repayments and return of capital	65	26	4
All other, net	248	112	81
Net cash used in investing activities	(3,394)	(2,941)	(3,441)
Financing activities:
Commercial paper – issued	300	1,263	0
Commercial paper - repayments	(300)	(1,263)	0
Long-term debt – borrowings	2,911	864	2,993
Long-term debt – repayments	(642)	(2,269)	(2,226)
Debt issuance costs	(33)	(11)	(21)
Issuance of common stock	46	11	33
Common stock repurchased	(2,372)	(197)	(965)
Dividends paid	(773)	(719)	(613)
Issuance of MPLX LP common units	473	776	0
Issuance of MPLX LP redeemable preferred units	0	984	0
Distributions to noncontrolling interests	(694)	(542)	(40)
Contributions from noncontrolling interests	129	6	0
Contingent consideration payment	(89)	(164)	(175)
All other, net	(47)	(33)	15
Net cash used in financing activities	(1,091)	(1,294)	(999)
Net increase (decrease) in cash and cash equivalents	2,124	(240)	(367)
Cash and cash equivalents at beginning of period	887	1,127	1,494
Cash and cash equivalents at end of period	$ 3,011	$ 887	$ 1,127

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Millions	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Non-controlling Interests
Beginning balance at Dec. 31, 2014	$ 11,390	$ 7	$ (6,299)	$ 9,841	$ 7,515	$ (313)	$ 639
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	2,868				2,852		16
Dividends declared	(615)				(615)
Distributions to noncontrolling interests	(40)						(40)
Other comprehensive income (loss)	(5)					(5)
Shares repurchased	(965)		(965)
Shares returned - stock based compensation			(11)
Shares issued - stock based compensation				33
Shares issued (returned) – stock-based compensation	22
Stock-based compensation	85			69			16
Impact from equity transactions of MPLX LP	6,923			1,128			5,795
Noncontrolling interest - MarkWest Merger	13						13
Other	(1)				0		(1)
Ending 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)	1,172				1,174		(2)
Dividends declared	(720)				(720)
Distributions to noncontrolling interests	(517)						(517)
Contributions from noncontrolling interests	6						6
Other comprehensive income (loss)	84					84
Shares repurchased	(197)		(197)
Shares returned - stock based compensation			(10)
Shares issued - stock based compensation				11
Shares issued (returned) – stock-based compensation	1
Stock-based compensation	41			35			6
Impact from equity transactions of MPLX LP	658			(57)			715
Ending 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)	3,739				3,432		307
Dividends declared	(774)				(774)
Distributions to noncontrolling interests	(629)						(629)
Contributions from noncontrolling interests	129						129
Other comprehensive income (loss)	3					3
Shares repurchased	(2,372)		(2,372)
Shares returned - stock based compensation			(15)
Shares issued - stock based compensation				46
Shares issued (returned) – stock-based compensation	31
Stock-based compensation	54			46			8
Impact from equity transactions of MPLX LP	444			110			334
Ending balance at Dec. 31, 2017	$ 20,828	$ 7	$ (9,869)	$ 11,262	$ 12,864	$ (231)	$ 6,795

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interest - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Temporary Equity [Abstract]
Redeemable noncontrolling interest, beginning balance	$ 1,000	$ 0
Net income (loss) attributable to redeemable noncontrolling interest	65	41
Distributions to noncontrolling interests	(65)	(25)
Issuance of MPLX LP redeemable preferred units		984
Redeemable noncontrolling interest, ending balance	$ 1,000	$ 1,000

Consolidated Statements of Eq11

Consolidated Statements of Equity - Shares - shares shares in Millions	Total	Common Stock	Treasury Stock
Number of shares issued (beginning balance) at Dec. 31, 2014		726
Number of shares issued - stock-based compensation		3
Number of shares issued (ending balance) at Dec. 31, 2015		729
Number of shares held in treasury (beginning balance) at Dec. 31, 2014			(179)
Number of shares repurchased	(19)		(19)
Number of shares held in treasury (ending balance) at Dec. 31, 2015			(198)
Number of shares issued - stock-based compensation		2
Number of shares issued (ending balance) at Dec. 31, 2016	731	731
Number of shares repurchased	(4)		(4)
Number of shares returned - stock-based compensation			(1)
Number of shares held in treasury (ending balance) at Dec. 31, 2016	(203)		(203)
Number of shares issued - stock-based compensation		3
Number of shares issued (ending balance) at Dec. 31, 2017	734	734
Number of shares repurchased	(44)		(44)
Number of shares returned - stock-based compensation			(1)
Number of shares held in treasury (ending balance) at Dec. 31, 2017	(248)		(248)

Description Of The Business And

Description Of The Business And Basis Of Presentation	12 Months Ended
	Dec. 31, 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 10 for additional information about our operations. Spinoff – On May 25, 2011, the Marathon Oil board of directors approved the spinoff of its Refining, Marketing & Transportation Business (“RM&T Business”) into an independent, publicly traded company, MPC, through the distribution of MPC common stock to the stockholders of Marathon Oil common stock (the “Spinoff”). MPC became an independent, publicly traded company on July 1, 2011. Basis of Presentation – Our results of operations and cash flows consist of consolidated MPC activities. All significant intercompany transactions and accounts have been eliminated. 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 4 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 from pipeline and storage assets were recast effective January 1, 2015, and the results from 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 10 and Note 15 for additional information.

Summary Of Principal Accounting

Summary Of Principal Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary Of Principal Accounting Policies	Summary of Principal Accounting Policies Principles applied in consolidation – These consolidated financial statements include the accounts of our majority-owned, controlled subsidiaries and MPLX. Changes in ownership interest in consolidated subsidiaries that do not result in a change in control are recorded as an equity transaction. As of December 31, 2017 , we owned a 30.4 percent interest in MPLX, including a two percent general partner interest. Due to our 100 percent ownership of the general partner interest, we have determined that we control MPLX and therefore we consolidate MPLX and record a noncontrolling interest for the 69.6 percent interest owned by the public. Investments in entities over which we have significant influence, but not control, are accounted for using the equity method of accounting. This includes entities in which we hold majority ownership but the minority shareholders have substantive participating rights. Income from equity method investments represents our proportionate share of net income generated by the equity method investees. Differences in the basis of the investments and the separate net asset values of the investees, if any, are amortized into net income over the remaining useful lives of the underlying assets and liabilities, except for the excess related to goodwill. Equity method investments are evaluated for impairment whenever changes in the facts and circumstances indicate an other than temporary loss in value has occurred. When the loss is deemed to be other than temporary, the carrying value of the equity method investment is written down to fair value. Use of estimates – The preparation of financial statements in accordance with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities as of the date of the consolidated financial statements and the reported amounts of revenues and expenses during the respective reporting periods. Revenue recognition – Revenues are recognized when products are shipped or services are provided to customers, title is transferred, the sales price is fixed or determinable and collectability is reasonably assured. Costs associated with revenues are recorded in cost of revenues. Shipping and other transportation costs billed to our customers are presented on a gross basis in revenues and cost of revenues. Rebates from vendors are recognized as a reduction of cost of revenues when the initiating transaction occurs. Incentives that are derived from contractual provisions are accrued based on past experience and recognized in cost of revenues. Rebates to customers are reflected as a reduction of revenue and are accrued for in “Accounts payable” on the consolidated balance sheets. Crude oil and refined product exchanges and matching buy/sell transactions – We enter into exchange contracts and matching buy/sell arrangements whereby we agree to deliver a particular quantity and quality of crude oil or refined products at a specified location and date to a particular counterparty and to receive from the same counterparty the same commodity at a specified location on the same or another specified date. The exchange receipts and deliveries are nonmonetary transactions, with the exception of associated grade or location differentials that are settled in cash. The matching buy/sell purchase and sale transactions are settled in cash. Both exchange and matching buy/sell transactions are accounted for as exchanges of inventory and no revenues are recorded. The exchange transactions are recognized at the carrying amount of the inventory transferred. Consumer excise taxes – We are required by various governmental authorities, including countries, states and municipalities, to collect and remit taxes on certain consumer products. Such taxes are presented on a gross basis in revenues and costs and expenses in the consolidated statements of income. Cash and cash equivalents – Cash and cash equivalents include cash on hand and on deposit and investments in highly liquid debt instruments with maturities of three months or less. Restricted cash – Restricted cash consists of cash and investments that must be maintained as collateral for letters of credit issued to certain third party producer customers. The balances will be outstanding until certain capital projects are completed and the third party releases the restriction. Restricted cash also consists of cash advances to be used for the operation and maintenance of an operated pipeline system. At December 31, 2017 and 2016 , the amount of restricted cash included in “Other current assets” on the consolidated balance sheets were $4 million and $5 million , respectively, which is currently reflected in our Midstream segment. Accounts receivable and allowance for doubtful accounts – Our receivables primarily consist of customer accounts receivable. Customer receivables are recorded at the invoiced amounts and generally do not bear interest. Allowances for doubtful accounts are generally recorded when it becomes probable the receivable will not be collected and are booked to bad debt expense. The allowance for doubtful accounts is the best estimate of the amount of probable credit losses in customer accounts receivable. We review the allowance quarterly and past-due balances over 180 days are reviewed individually for collectability. Approximately 23 percent of our accounts receivable balances at both December 31, 2017 and 2016 are related to sales of crude oil or refinery feedstocks to customers with whom we have master netting agreements. We have master netting agreements with more than 100 companies engaged in the crude oil or refinery feedstock trading and supply business or the petroleum refining industry. A master netting agreement generally provides for a once per month net cash settlement of the accounts receivable from and the accounts payable to a particular counterparty. Inventories – Inventories are carried at the lower of cost or market value. Cost of inventories is determined primarily under the LIFO method. Costs for crude oil, refinery feedstocks and refined product inventories are aggregated on a consolidated basis for purposes of assessing if the LIFO cost basis of these inventories may have to be written down to market value. Derivative instruments – We use derivatives to economically hedge a portion of our exposure to commodity price risk and, historically, to interest rate risk. We also have limited authority to use selective derivative instruments that assume market risk. All derivative instruments (including derivative instruments embedded in other contracts) are recorded at fair value. Certain commodity derivatives are reflected on the consolidated balance sheets on a net basis by counterparty as they are governed by master netting agreements. Cash flows related to derivatives used to hedge commodity price risk and interest rate risk are classified in operating activities with the underlying transactions. Derivatives not designated as accounting hedges – Derivatives that are not designated as accounting hedges may include commodity derivatives used to hedge price risk on (1) inventories, (2) fixed price sales of refined products, (3) the acquisition of foreign-sourced crude oil, (4) the acquisition of ethanol for blending with refined products, (5) the sale of NGLs and (6) the purchase of natural gas. Changes in the fair value of derivatives not designated as accounting hedges are recognized immediately in net income. Concentrations of credit risk – All of our financial instruments, including derivatives, involve elements of credit and market risk. The most significant portion of our credit risk relates to nonperformance by counterparties. The counterparties to our financial instruments consist primarily of major financial institutions and companies within the energy industry. To manage counterparty risk associated with financial instruments, we select and monitor counterparties based on an assessment of their financial strength and on credit ratings, if available. Additionally, we limit the level of exposure with any single counterparty. Property, plant and equipment – Property, plant and equipment are recorded at cost and depreciated on a straight-line basis over the estimated useful lives of the assets, which range from three to 49 years. Such assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. If the sum of the expected undiscounted future cash flows from the use of the asset and its eventual disposition is less than the carrying amount of the asset, an impairment assessment is performed and the excess of the book value over the fair value of the asset is recorded as an impairment loss. When items of property, plant and equipment are sold or otherwise disposed of, any gains or losses are reported in net income. Gains on the disposal of property, plant and equipment are recognized when earned, which is generally at the time of closing. If a loss on disposal is expected, such losses are recognized when the assets are classified as held for sale. Interest expense is capitalized for qualifying assets under construction. Capitalized interest costs are included in property, plant and equipment and are depreciated over the useful life of the related asset. Goodwill and intangible assets – Goodwill represents the excess of the purchase price over the estimated fair value of the net assets acquired in the acquisition of a business. Goodwill is not amortized, but rather is tested for impairment annually and when events or changes in circumstances indicate that the fair value of a reporting unit with goodwill has been reduced below carrying value. The impairment test requires allocating goodwill and other assets and liabilities to reporting units. The fair value of each reporting unit is determined and compared to the carrying value of the reporting unit. If the fair value of the reporting unit is less than the carrying value, including goodwill, the implied fair value of goodwill is calculated. The excess, if any, of the book value over the implied fair value of goodwill is charged to net income as an impairment expense. Amortization of intangibles with definite lives is calculated using the straight-line method which is reflective of the benefit pattern in which the estimated economic benefit is expected to be received over the estimated useful life of the intangible asset. Intangibles subject to amortization are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the intangible may not be recoverable. If the sum of the expected undiscounted future cash flows related to the asset is less than the carrying amount of the asset, an impairment loss is recognized based on the fair value of the asset. Intangibles not subject to amortization are tested for impairment annually and when circumstances indicate that the fair value is less than the carrying amount of the intangible. If the fair value is less than the carrying value, an impairment is recorded for the difference. Major maintenance activities – Costs for planned turnaround, major maintenance and engineered project activities are expensed in the period incurred. These types of costs include contractor repair services, materials and supplies, equipment rentals and our labor costs. Environmental costs – Environmental expenditures are capitalized for additional equipment that mitigates or prevents future contamination or improves environmental safety or efficiency of the existing assets. We recognize remediation costs and penalties when the responsibility to remediate is probable and the amount of associated costs can be reasonably estimated. The timing of remediation accruals coincides with completion of a feasibility study or the commitment to a formal plan of action. Remediation liabilities are accrued based on estimates of known environmental exposure and are discounted when the estimated amounts are reasonably fixed and determinable. If recoveries of remediation costs from third parties are probable, a receivable is recorded and is discounted when the estimated amount is reasonably fixed and determinable. Asset retirement obligations – The fair value of asset retirement obligations is recognized in the period in which the obligations are incurred if a reasonable estimate of fair value can be made. The majority of our recognized asset retirement liability relates to conditional asset retirement obligations for removal and disposal of fire-retardant material from certain refining facilities. The remaining recognized asset retirement liability relates to other refining assets, the removal of underground storage tanks at our leased convenience stores, certain pipelines and processing facilities and other related pipeline assets. The fair values recorded for such obligations are based on the most probable current cost projections. The recorded asset retirement obligations are not material to the consolidated financial statements. Asset retirement obligations have not been recognized for some assets because the fair value cannot be reasonably estimated since the settlement dates of the obligations are indeterminate. Such obligations will be recognized in the period when sufficient information becomes available to estimate a range of potential settlement dates. The asset retirement obligations principally include the hazardous material disposal and removal or dismantlement requirements associated with the closure of certain refining, terminal, retail, pipeline and processing assets. Our practice is to keep our assets in good operating condition through routine repair and maintenance of component parts in the ordinary course of business and by continuing to make improvements based on technological advances. As a result, we believe that generally these assets have no expected settlement date for purposes of estimating asset retirement obligations since the dates or ranges of dates upon which we would retire these assets cannot be reasonably estimated at this time. Income taxes – Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between the financial statement carrying amounts of assets and liabilities and their tax bases. Deferred tax assets are recorded when it is more likely than not that they will be realized. The realization of deferred tax assets is assessed periodically based on several factors, primarily our expectation to generate sufficient future taxable income. Stock-based compensation arrangements – The fair value of stock options granted to our employees is estimated on the date of grant using the Black-Scholes option pricing model. The model employs various assumptions, based on management’s estimates at the time of grant, which impact the calculation of fair value and ultimately, the amount of expense that is recognized over the vesting period of the stock option award. Of the required assumptions, the expected life of the stock option award and the expected volatility of our stock price have the most significant impact on the fair value calculation. The average expected life is based on our historical employee exercise behavior. The assumption for expected volatility of our stock price reflects a weighting of 50 percent of our common stock implied volatility and 50 percent of our common stock historical volatility. The fair value of restricted stock awards granted to our employees is determined based on the fair market value of our common stock on the date of grant. The fair value of performance unit awards granted to our employees is estimated on the date of grant using a Monte Carlo valuation model. Our stock-based compensation expense is recognized based on management’s estimate of the awards that are expected to vest, using the straight-line attribution method for all service-based awards with a graded vesting feature. If actual forfeiture results are different than expected, adjustments to recognized compensation expense may be required in future periods. Unearned stock-based compensation is charged to equity when restricted stock awards are granted. Compensation expense is recognized over the vesting period and is adjusted if conditions of the restricted stock award are not met. Business combinations - We recognize and measure the assets acquired and liabilities assumed in a business combination based on their estimated fair values at the acquisition date, with any remaining difference versus the purchase consideration recorded as goodwill or gain from a bargain purchase. For all material acquisitions, management engages an independent valuation specialist to assist with the determination of fair value of the assets acquired, liabilities assumed, noncontrolling interest, if any, and goodwill, based on recognized business valuation methodologies. If the initial accounting for the business combination is incomplete by the end of the reporting period in which the acquisition occurs, an estimate will be recorded. Subsequent to the acquisition, and not later than one year from the acquisition date, we will record any material adjustments to the initial estimate based on new information obtained about facts and circumstances that existed as of the acquisition date. An income, market or cost valuation method may be utilized to estimate the fair value of the assets acquired, liabilities assumed, and noncontrolling interest, if any, in a business combination. The income valuation method represents the present value of future cash flows over the life of the asset using: (i) discrete financial forecasts, which rely on management’s estimates of revenue and operating expenses; (ii) long-term growth rates; and (iii) appropriate discount rates. The market valuation method uses prices paid for a reasonably similar asset by other purchasers in the market, with adjustments relating to any differences between the assets. The cost valuation method is based on the replacement cost of a comparable asset at prices at the time of the acquisition reduced for depreciation of the asset. Acquisition-related costs are expensed as incurred in connection with each business combination. Renewable fuel identification numbers – We purchase RINs to satisfy a portion of our RFS2 compliance. We record a short-term intangible asset, included in “Other current assets” on the balance sheet, for RINs owned in excess of our anticipated current period compliance requirements. The asset value is based on the product of the excess RINs as of the balance sheet date, if any, and the weighted average cost of our RINs. We record a current liability, included in “Other current liabilities” on the balance sheet, when we are deficient RINs based on the product of the deficient RINs as of the balance sheet date, if any, and the market price of the RINs at the balance sheet date. The cost of RINs used for compliance is reflected in “Cost of revenues” on the income statement. Any gains or losses on the sale or expiration of RINs are classified as “Other income” on the income statement. Proceeds from RIN sales are included in investing activities - “All other, net” on the cash flow statement.

Accounting Standards

Accounting Standards	12 Months Ended
	Dec. 31, 2017
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recently Adopted Accounting Pronouncements	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 Accounting Pronouncements	Not Yet Adopted In August 2017, the FASB issued an accounting standards update to amend the hedge accounting rules to simplify the application of hedge accounting guidance and better portray the economic results of risk management activities in the financial statements. The guidance expands the ability to hedge nonfinancial and financial risk components, reduces complexity in fair value hedges of interest rate risk, eliminates the requirement to separately measure and report hedge ineffectiveness, as well as eases certain hedge effectiveness assessment requirements. The guidance is effective beginning in 2019 with early adoption permitted. We are currently evaluating the impact of this guidance, including transition elections and required disclosures, on our financial statements and the timing of adoption. However, since we have not historically designated our commodity derivatives as hedges, we do not expect the adoption of this accounting standards update to have a material impact on our consolidated financial statements. 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 on a prospective basis beginning on January 1, 2018. 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 states 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 adopted in conjunction with the adoption date of the revenue recognition accounting standards update, which we will adopt on 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. 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. 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 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. 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. 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 completed our system implementation evaluation during the fourth quarter of 2017, and concluded we will implement a third-party supported lease accounting information system solution to account for our leases. We have begun a project to implement this system and are currently collecting the necessary information on our lease population, establishing a new lease accounting process and designing new internal controls for the new process. 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 amends the presentation and disclosure of financial instruments. The changes are effective for fiscal years and interim periods within those fiscal years beginning after December 15, 2017. 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 completed the evaluation of the impact of this standard on our financial statements and disclosures, internal controls and accounting policies in the fourth quarter of 2017. We will adopt the standard effective January 1, 2018, using the modified retrospective method, resulting in an immaterial cumulative effect adjustment as of the date of adoption. For most contract types, we do not believe revenue recognition patterns will change materially. We do expect certain provisions of the 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 and collected on behalf of our customers from gross to net upon the adoption of this accounting standards update. Based on the results of our evaluation process, we do not expect our existing revenue recognition processes, controls and information systems to materially change.

MPLX LP

MPLX LP	12 Months Ended
	Dec. 31, 2017
Noncontrolling Interest [Abstract]
MPLX LP	MPLX LP MPLX is a diversified, growth-oriented publicly traded master limited partnership formed by us in 2012 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 5 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 December 31, 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 our significant economic interest, we also have the power, through our 100 percent ownership of the general partner, to control the decisions that most significantly impact MPLX. We therefore consolidate MPLX and record a noncontrolling interest for the 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 25 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”) at 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 unitholders. 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 approximately two-thirds of the third quarter 2017 common unit distributions, IDRs and general partner distributions with respect to the common units issued in this transaction. The contributions of these assets were accounted for as transactions between entities under common control and we did not record a gain or loss. On March 1, 2017, we contributed certain terminal, pipeline and storage assets to MPLX in exchange total consideration of $2.0 billion . This consideration consisted of MPLX equity and $1.5 billion in cash. We received approximately 13 million 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 the 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 MPLX 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 therefore, we did not record a gain or loss. On December 4, 2015, we sold our remaining 0.5 percent interest in Pipe Line Holdings to MPLX for $12 million . As a result, MPLX now owns 100 percent of Pipe Line Holdings. The sales and contribution of our interests in Pipe Line Holdings to MPLX resulted in a change of our ownership in Pipe Line Holdings, but not a change in control. We accounted for these sales as transactions between entities under common control and did not record a gain or loss. Public Offerings On February 10, 2017, MPLX completed a public offering of $1.25 billion aggregate principal amount of 4.125 percent unsecured senior notes due March 2027 and $1.0 billion aggregate principal amount of 5.200 percent 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 19 for more information. ATM Program On August 4, 2016, MPLX entered into a Second Amended and Restated Distribution Agreement (the “Distribution Agreement”) providing for at-the-market issuances of common units, in amounts, at prices and on terms determined by market conditions and other factors at the time of the offerings (such at-the-market program, referred to as the “ATM Program”). During 2017 , MPLX issued an aggregate of 14 million MPLX common units under the ATM Program, generating net proceeds of approximately $473 million . MPLX used 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 Noncontrolling Interest As a result of equity transactions of MPLX, we are required to adjust non-controlling interest and additional paid-in capital. Changes in MPC’s equity resulting from changes in its ownership interest in MPLX were as follows: (In millions) 2017 2016 2015 Transfers (to) from noncontrolling interest Changes due to the issuance of MPLX LP common units to the public $ 25 $ (60 ) $ 1,532 Changes due to the issuance of MPLX LP common units and general partner units to MPC 114 121 — Net transfers (to) from noncontrolling interests 139 61 1,532 Tax impact (29 ) (118 ) (404 ) Increase (decrease) in MPC's additional paid-in capital, net of tax $ 110 $ (57 ) 1,128 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 which establish fees for operational and management services provided between us and MPLX and for executive management services and certain general and administrative services provided by us to MPLX. These transactions are eliminated in consolidation.

Acquisitions and Investments

Acquisitions and Investments	12 Months Ended
	Dec. 31, 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: (In millions) 2017 Sales and other operating revenues (including consumer excise taxes) $ 38 Income from operations 20 Assuming the acquisition of the Ozark pipeline had occurred on January 1, 2016, the consolidated pro forma results would not have been materially different from reported results. Investment in Pipeline Company On February 15, 2017, MPLX 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 capable of transporting more 520 mbpd of crude oil from the Bakken/Three Forks production area in North Dakota to the Midwest through Patoka, Illinois and ultimately to the Gulf Coast. MPLX contributed $500 million of the $2 billion purchase price paid by the joint venture, MarEn Bakken Company LLC (“MarEn Bakken”), to acquire a 36.75 percent indirect equity interest in the Bakken Pipeline system from Energy Transfer Partners, L.P. (“ETP”) and Sunoco Logistics Partners, L.P. (“SXL”). MPLX holds, through a subsidiary, a 25 percent interest in MarEn Bakken, which equates to an approximate 9.2 percent indirect equity interest in the Bakken Pipeline system. 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. This waiver is no longer applicable as a result of the IDR exchange on February 1, 2018. 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. See Note 17 for information regarding the impairment of our investment in the Sandpiper pipeline project. Formation of Gathering and Processing Joint Venture Effective January 1, 2017, MPLX and Antero Midstream formed a joint venture, Sherwood Midstream LLC (“Sherwood Midstream”), to support the development of Antero Resources Corporation’s Marcellus Shale acreage in West Virginia. MPLX has a 50 percent ownership interest in Sherwood Midstream. In connection with this transaction, MPLX contributed certain gas processing plants currently under construction at the Sherwood Complex with a fair value of approximately $134 million and cash of approximately $20 million . Antero Midstream made an initial capital contribution of approximately $154 million . Also effective January 1, 2017, MPLX converted all of its ownership interests in MarkWest Ohio Fractionation Company, L.L.C. (“Ohio Fractionation”), a previously wholly-owned subsidiary, to Class A Interests and amended its LLC Agreement to create Class B-3 Interests, which were sold to Sherwood Midstream for $126 million in cash. The Class B-3 Interests provide Sherwood Midstream with the right to fractionation revenue and the obligation to pay expenses related to 20 mbpd of capacity in the Hopedale 3 fractionator. Effective January 1, 2017, MPLX and Sherwood Midstream formed a joint venture, Sherwood Midstream Holdings LLC (“Sherwood Midstream Holdings”), for the purpose of owning, operating and maintaining all of the shared assets for the benefit of and use in the operation of the gas plants and other assets owned by Sherwood Midstream and the gas plants and deethanization facilities owned by MPLX. MPLX contributed certain real property, equipment and facilities with a fair value of approximately $209 million to Sherwood Midstream Holdings in exchange for a 79 percent initial ownership interest. Sherwood Midstream contributed cash of approximately $44 million to Sherwood Midstream Holdings in exchange for a 21 percent ownership interest. MPLX has a 10.5 percent indirect interest in Sherwood Midstream Holdings through its ownership in Sherwood Midstream. The net book value of the contributed assets was approximately $203 million . The contribution was determined to be an in-substance sale of real estate. As such, MPLX only recognized a gain for the portion attributable to Antero Midstream’s indirect interest of approximately $2 million . We account for our direct interests in Sherwood Midstream and Sherwood Midstream Holdings as part of our Midstream segment using the equity method of accounting. We continue to consolidate Ohio Fractionation and have recognized a noncontrolling interest for Sherwood Midstream’s interest in that entity. See Note 6 for additional information related to the investments in Sherwood Midstream, Ohio Fractionation and Sherwood Midstream Holdings. 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 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 6 for information on Crowley Coastal Partners as a VIE and Note 25 for information on our conditional guarantee of the indebtedness of Crowley Ocean Partners and Crowley Blue Water Partners. Merger with MarkWest Energy Partners, L.P. On December 4, 2015, MPLX completed the MarkWest Merger. Each common unit of MarkWest issued and outstanding immediately prior to the effective time of the MarkWest Merger was converted into a right to receive 1.09 common units of MPLX representing limited partner interests in MPLX, plus a one-time cash payment of $6.20 per unit. We contributed approximately $1.28 billion of cash to MPLX to pay the aggregate cash consideration to MarkWest unitholders, without receiving any new equity from MPLX in exchange. At closing, we made a payment of $1.23 billion to MarkWest common unitholders and the remaining $50 million was paid in equal amounts, the first $25 million was paid in July 2016 and the second $25 million was paid in July 2017, in connection with the conversion of the MPLX Class B Units to MPLX common units. Our financial results and operating statistics reflect the results of MarkWest from the date of the MarkWest Merger. The components of the fair value of consideration transferred are as follows: (In millions) Fair value of MPLX units issued $ 7,326 Cash payment to MarkWest unitholders 1,230 Payable to MarkWest Class B unitholders 50 Total fair value of consideration transferred $ 8,606 The net fair value of the assets acquired and liabilities assumed in connection with the MarkWest Merger was less than the fair value of the total consideration resulting in the recognition of $2.21 billion of goodwill in three reporting units within our Midstream segment, substantially all of which is not deductible for tax purposes. Goodwill represents the complimentary aspects of the highly diverse asset base of MarkWest and MPLX that will provide significant additional opportunities across the hydrocarbon value chain. As further discussed in Note 16 , we recorded a goodwill impairment charge of $129 million based on the implied fair value of goodwill as of the interim impairment analysis in the first quarter of 2016. During the second quarter of 2016, we finalized the analysis of the purchase price allocation. The completion of the purchase price allocation resulted in an additional $1 million of impairment expense, as more fully discussed in Note 16 . We recognized $36 million of transaction costs related to the MarkWest Merger. These costs were expensed and $30 million is included in selling, general and administrative expenses and $6 million is in net interest and other financial income (costs). The amounts of revenue and income from operations associated with the MarkWest Merger included in our consolidated statements of income for 2015 are as follows: (In millions) 2015 Sales and other operating revenues (including consumer excise taxes) $ 120 Income from operations 32 Unaudited Pro Forma Financial Information The following unaudited pro forma financial information presents consolidated results assuming the MarkWest Merger occurred on January 1, 2014. (In millions, except per share data) 2015 Sales and other operating revenues (including consumer excise taxes) $ 73,760 Net income attributable to MPC 2,825 Net income attributable to MPC per share – basic $ 5.25 Net income attributable to MPC per share – diluted 5.21 The unaudited pro forma financial information includes adjustments to align accounting policies, increased depreciation expense to reflect the fair value of property, plant and equipment, increased amortization expense related to identifiable intangible assets, adjustments to amortize the difference between the fair value and the principal amount of the MarkWest debt assumed by MPLX, adjustments to reflect the change in our limited partner interest in MPLX resulting from the MarkWest Merger, as well as the related income tax effects. The unaudited pro forma financial information does not give effect to potential synergies that could result from the transactions and is not necessarily indicative of the results of future operations.

Variable Interest Entities

Variable Interest Entities	12 Months Ended
	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Variable Interest Entities	Variable Interest Entities In addition to MPLX, as described in Note 4 , the following entities are also VIEs. Crowley Coastal Partners In May 2016, Crowley Coastal Partners was formed to own an interest in both Crowley Ocean Partners and Crowley Blue Water Partners. We have determined that Crowley Coastal Partners is a VIE based on the terms of the existing financing arrangements for Crowley Blue Water Partners and Crowley Ocean Partners and the associated debt guarantees by MPC and Crowley. Our maximum exposure to loss at December 31, 2017 was $486 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 December 31, 2017 , MarkWest had a 56 percent legal ownership interest in MarkWest Utica EMG. MarkWest Utica EMG's inability to fund its planned activities without subordinated financial support qualify it as a VIE. Utica Operating is not deemed to be the primary beneficiary due to EMG Utica’s voting rights on significant matters. We account for our ownership interest in MarkWest Utica EMG as an equity method investment. MPLX receives engineering and construction and administrative management fee revenue and reimbursement for other direct personnel costs for operating MarkWest Utica EMG. Our maximum exposure to loss as a result of our involvement with MarkWest Utica EMG includes our equity investment, any additional capital contribution commitments and any operating expenses incurred by the subsidiary operator in excess of compensation received for the performance of the operating services. Our equity investment in MarkWest Utica EMG at December 31, 2017 was $2.1 billion . Ohio Gathering Ohio Gathering Company, L.L.C. (“Ohio Gathering”) is a subsidiary of MarkWest Utica EMG and is engaged in providing natural gas gathering services in the Utica Shale in eastern Ohio. Ohio Gathering is a joint venture between MarkWest Utica EMG and Summit Midstream Partners, LLC. As of December 31, 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 5 , MPLX and Antero Midstream formed a joint venture, Sherwood Midstream, to support the development of Antero Resources Corporation’s Marcellus Shale acreage in West Virginia. As of December 31, 2017 , MPLX had a 50 percent ownership interest in Sherwood Midstream. Sherwood Midstream’s inability to fund its planned activities without additional subordinated financial support qualify it as a VIE. MPLX is not deemed to be the primary beneficiary, due to Antero Midstream’s voting rights on significant matters. We account for our ownership interest in Sherwood Midstream using the equity method of accounting. Our maximum exposure to loss as a result of our involvement with Sherwood Midstream includes our equity investment, any additional capital contribution commitments and any operating expenses incurred by the subsidiary operator in excess of compensation received for the performance of the operating services. Our equity investment in Sherwood Midstream at December 31, 2017 was $236 million . Ohio Fractionation As described in Note 5 , MPLX converted all of its ownership interests in Ohio Fractionation to Class A Interests and amended its LLC Agreement to create Class B-3 Interests, which were sold to Sherwood Midstream, providing it with the right to fractionation revenue and the obligation to pay expenses related to 20 mbpd of capacity in the Hopedale 3 fractionator. Ohio Fractionation’s inability to fund its operations without additional subordinated financial support qualify it as a VIE. MPLX has been deemed to be the primary beneficiary of Ohio Fractionation because it has control over decisions that could significantly impact its financial performance, and as a result, consolidates Ohio Fractionation. Sherwood Midstream Holdings As described in Note 5 , MPLX and Sherwood Midstream entered into a joint venture, Sherwood Midstream Holdings, for the purpose of owning, operating and maintaining all of the shared assets for the benefit of and use in the operation of the gas plants and other assets owned by Sherwood Midstream and the gas plants and deethanization facilities owned by MPLX. MPLX had an initial 79 percent direct ownership in Sherwood Midstream Holdings, in addition to a 10.5 percent indirect interest through its ownership in Sherwood Midstream. Sherwood Midstream Holdings’ inability to fund its operations without additional subordinated financial support qualify it as a VIE. We account for our ownership interest in Sherwood Midstream Holdings using the equity method of accounting as Sherwood Midstream is considered to be the general partner and controls all decisions related to Sherwood Midstream Holdings. Our maximum exposure to loss as a result of our involvement with Sherwood Midstream Holdings includes our equity investment, any additional capital contribution commitments and any operating expenses incurred by the subsidiary operator in excess of compensation received for the performance of the operating services. Our equity investment in Sherwood Midstream Holdings at December 31, 2017 was $165 million .

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Our related parties included: • Crowley Blue Water Partners, in which we have a 50 percent indirect noncontrolling interest. Crowley Blue Water Partners owns and operates three Jones Act ATB vessels. • Crowley Ocean Partners, in which we have a 50 percent indirect noncontrolling interest. Crowley Ocean Partners owns and operates Jones Act product tankers. • Illinois Extension Pipeline Company, LLC (“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. • 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: (In millions) 2017 2016 2015 PFJ Southeast $ 619 $ 56 $ — Other equity method investees 10 6 6 Total $ 629 $ 62 $ 6 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: (In millions) 2017 2016 2015 MarkWest Utica EMG $ 17 $ 16 $ — Ohio Gathering 16 15 2 Sherwood Midstream 8 — — Other equity method investees 11 10 2 Total $ 52 $ 41 $ 4 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: (In millions) 2017 2016 2015 Crowley Blue Water Partners $ 60 $ 37 $ — Crowley Ocean Partners 79 52 6 Illinois Extension Pipeline 100 110 4 LOCAP 22 23 23 LOOP 71 59 52 TAAE 72 41 52 TACE 44 59 54 TAME 76 93 87 Other equity method investees 46 35 30 Total $ 570 $ 509 $ 308 Related party purchases from Crowley Blue Water Partners and Crowley Ocean Partners consist of leasing marine equipment primarily used to transport refined products. Related party purchases from Illinois Extension Pipeline, LOCAP, LOOP and other equity method investees consist primarily of crude oil transportation costs. Related party purchases from TAAE, TACE and TAME consist of ethanol purchases. Receivables from related parties, which are included in “Receivables, less allowance for doubtful accounts” on the accompanying consolidated balance sheets, were as follows: December 31, (In millions) 2017 2016 PFJ Southeast $ 28 $ 40 Other equity method investees 8 5 Total $ 36 $ 45 The long-term receivable from related parties, which is included in “Other noncurrent assets” on the accompanying consolidated balance sheet, was $1 million at December 31, 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: December 31, (In millions) 2017 2016 Illinois Extension Pipeline $ 8 $ 9 LOOP 3 6 MarkWest Utica EMG 29 24 Ohio Gathering 9 — Sherwood Midstream 8 — Other equity method investees 12 14 Total $ 69 $ 53

Income per Common Share

Income per Common Share	12 Months Ended
	Dec. 31, 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. The average number of shares of common stock and per share amounts have been retroactively restated to reflect the two-for-one stock split completed in June 2015. Diluted income per share assumes exercise of certain stock based compensation awards, provided the effect is not anti-dilutive. MPC grants certain incentive compensation awards to employees and non-employee directors that are considered to be participating securities. Due to the presence of participating securities, we have calculated our earnings per share using the two-class method. (In millions, except per share data) 2017 2016 2015 Basic earnings per share: Allocation of earnings: Net income attributable to MPC $ 3,432 $ 1,174 $ 2,852 Income allocated to participating securities 2 1 4 Income available to common stockholders – basic $ 3,430 $ 1,173 $ 2,848 Weighted average common shares outstanding 507 528 538 Basic earnings per share $ 6.76 $ 2.22 $ 5.29 Diluted earnings per share: Allocation of earnings: Net income attributable to MPC $ 3,432 $ 1,174 $ 2,852 Income allocated to participating securities 2 1 4 Income available to common stockholders – diluted $ 3,430 $ 1,173 $ 2,848 Weighted average common shares outstanding 507 528 538 Effect of dilutive securities 5 2 4 Weighted average common shares, including dilutive effect 512 530 542 Diluted earnings per share $ 6.70 $ 2.21 $ 5.26 The following table summarizes the shares that were anti-dilutive, and therefore, were excluded from the diluted share calculation. (In millions) 2017 2016 2015 Shares issued under stock-based compensation plans 1 3 1

Equity

Equity	12 Months Ended
	Dec. 31, 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 December 31, 2017 , we had $3.19 billion of remaining share repurchase authorizations from our board of directors. We may utilize various methods to effect the repurchases, which could include open market repurchases, negotiated block transactions, accelerated share repurchases or open market solicitations for shares, some of which may be 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 respective periods: (In millions, except per share data) 2017 2016 2015 Number of shares repurchased 44 4 19 Cash paid for shares repurchased $ 2,372 $ 197 $ 965 Average cost per share $ 53.85 $ 41.84 $ 50.31

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 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 six refineries in the Gulf Coast and Midwest regions of the United States, purchases refined products and ethanol for resale and distributes refined products through 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 – 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 via pipelines, terminals, towboats and barges. The Midstream segment primarily reflects the results of MPLX, our sponsored master limited partnership. On December 4, 2015, MPLX completed a merger with MarkWest and its results are included in the Midstream segment. Segment information for periods prior to the merger does not include amounts for these operations. See Note 5 . 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 Year Ended December 31, 2017 Revenues: Third party $ 52,761 $ 19,021 $ 2,322 $ 74,104 Intersegment (a) 11,309 4 1,443 12,756 Related party 621 8 — 629 Segment revenues $ 64,691 $ 19,033 $ 3,765 $ 87,489 Segment income from operations $ 2,321 $ 732 $ 1,339 $ 4,392 Income from equity method investments (b) 17 69 197 283 Depreciation and amortization (b) 1,082 275 699 2,056 Capital expenditures and investments (c)(d) 832 381 2,505 3,718 (In millions) Refining & Marketing Speedway Midstream Total Year Ended December 31, 2016 Revenues: Third party $ 43,167 $ 18,282 $ 1,828 $ 63,277 Intersegment (a) 10,589 3 1,262 11,854 Related party 61 1 — 62 Segment revenues $ 53,817 $ 18,286 $ 3,090 $ 75,193 Segment income from operations (e) $ 1,357 $ 734 $ 1,048 $ 3,139 Income from equity method investments (b) 24 5 142 171 Depreciation and amortization (b) 1,063 273 605 1,941 Capital expenditures and investments (c) 1,054 303 1,568 2,925 (In millions) Refining & Marketing Speedway Midstream Total Year Ended December 31, 2015 Revenues: Third party $ 52,168 $ 19,690 $ 187 $ 72,045 Intersegment (a) 12,024 3 930 12,957 Related party 6 — — 6 Segment revenues $ 64,198 $ 19,693 $ 1,117 $ 85,008 Segment income from operations (e)(f) $ 3,997 $ 673 $ 463 $ 5,133 Income from equity method investments 26 — 62 88 Depreciation and amortization (b) 1,052 254 144 1,450 Capital expenditures and investments (c)(g) 1,045 501 14,545 16,091 (a) Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties. (b) Differences between segment totals and MPC totals represent amounts related to unallocated items and are included in “Items not allocated to segments” in the reconciliation below. (c) Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates. (d) In 2017, 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. See Note 5 . (e) In 2016, the Refining & Marketing and Speedway segments include an inventory LCM benefit of $345 million and $25 million , respectively. In 2015, the Refining & Marketing and Speedway segments include an inventory LCM charge of $345 million and $25 million , respectively. (f) Included in the Midstream segment for 2015 are $36 million of transaction costs related to the MarkWest Merger. (g) The Midstream segment includes $13.85 billion for the MarkWest Merger. The following reconciles segment income from operations to income before income taxes as reported in the consolidated statements of income: (In millions) 2017 2016 2015 Segment income from operations $ 4,392 $ 3,139 $ 5,133 Items not allocated to segments: Corporate and other unallocated items (a) (365 ) (268 ) (293 ) Pension settlement expenses (b) (52 ) (7 ) (4 ) Litigation (29 ) — — Impairments (c) 23 (486 ) (144 ) Net interest and other financial income (costs) (625 ) (556 ) (318 ) Income before income taxes $ 3,344 $ 1,822 $ 4,374 (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 22 for further information. (c) 2017 includes MPC’s share of gains related to the sale of assets remaining from the Sandpiper pipeline project. 2016 includes impairments of goodwill and equity method investments. 2015 relates to the cancellation of the ROUX project at our Garyville refinery. See Notes 16 and 17 . The following reconciles segment capital expenditures and investments to total capital expenditures: (In millions) 2017 2016 2015 Segment capital expenditures and investments $ 3,718 $ 2,925 $ 16,091 Less investments in equity method investees (a) 805 431 2,788 Plus items not allocated to segments: Corporate and Other 83 81 155 Capitalized interest 55 63 37 Total capital expenditures (b) $ 3,051 $ 2,638 $ 13,495 (a) 2017 includes an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system. 2016 includes an adjustment of $143 million to the fair value of equity method investments acquired in connection with the MarkWest Merger. 2015 includes $2.46 billion related to the MarkWest Merger. See Note 5 . (b) Capital expenditures include changes in capital accruals. See Note 20 for a reconciliation of total capital expenditures to additions to property, plant and equipment as reported in the consolidated statements of cash flows. Revenues by product line were: (In millions) 2017 2016 2015 Refined products $ 63,846 $ 54,450 $ 63,738 Merchandise 5,174 5,297 5,188 Crude oil and refinery feedstocks 3,403 2,038 2,718 Service, transportation and other 1,681 1,492 401 Sales and other operating revenues (including consumer excise taxes) $ 74,104 $ 63,277 $ 72,045 No single customer accounted for more than 10 percent of annual revenues for the years ended December 31, 2017 , 2016 and 2015 . We do not have significant operations in foreign countries. Therefore, revenues in foreign countries and long-lived assets located in foreign countries, including property, plant and equipment and investments, are not material to our operations. Total assets by reportable segment were: December 31, (In millions) 2017 2016 Refining & Marketing $ 17,537 $ 17,601 Speedway 5,563 5,426 Midstream 19,937 18,516 Corporate and Other 6,010 2,870 Total consolidated assets $ 49,047 $ 44,413

Other Items

Other Items	12 Months Ended
	Dec. 31, 2017
Other Income and Expenses [Abstract]
Other Items	Other Items Net interest and other financial income (costs) was: (In millions) 2017 2016 2015 Interest income $ 27 $ 6 $ 6 Interest expense (a) (688 ) (602 ) (325 ) Interest capitalized 63 64 37 Loss on extinguishment of debt — — (5 ) Other financial costs (b) (27 ) (24 ) (31 ) Net interest and other financial income (costs) $ (625 ) $ (556 ) $ (318 ) (a) Includes $46 million , $44 million and $1 million for 2017 , 2016 and 2015 , respectively, for the amortization of the discount related to the difference between the fair value and the principal amount of assumed MarkWest debt. (b) 2015 includes $6 million of transaction costs related to the MarkWest Merger.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The TCJA was signed into law on December 22, 2017. The TCJA provided several key changes to U.S. tax law, including a federal corporate tax rate of 21 percent replacing the current rate applicable to MPC of 35 percent . MPC was required to calculate the effect of the TCJA on its deferred tax balances as of the enactment date. The effect of the federal corporate income tax rate change reduced net deferred tax liabilities by $1.5 billion in 2017. Any subsequent effect of a change in estimate affecting deferred taxes as of December 31, 2017 is expected to be immaterial, but could have an impact on the effective tax rate due to the permanent nature of applying differing tax rates to such a change in estimate. Income tax provisions (benefits) were: 2017 2016 2015 (In millions) Current Deferred Total Current Deferred Total Current Deferred Total Federal $ 681 $ (1,270 ) $ (589 ) $ 189 $ 336 $ 525 $ 1,210 $ 134 $ 1,344 State and local 98 33 131 27 57 84 152 9 161 Foreign (6 ) 4 (2 ) (1 ) 1 — 10 (9 ) 1 Total $ 773 $ (1,233 ) $ (460 ) $ 215 $ 394 $ 609 $ 1,372 $ 134 $ 1,506 A reconciliation of the federal statutory income tax rate ( 35 percent ) applied to income before income taxes to the provision for income taxes follows: 2017 2016 2015 Statutory rate applied to income before income taxes 35 % 35 % 35 % State and local income taxes, net of federal income tax effects 2 3 2 Domestic manufacturing deduction (1 ) (1 ) (2 ) Noncontrolling interests (4 ) (1 ) — Biodiesel excise tax credit — (1 ) (1 ) TCJA legislation (45 ) — — Other (1 ) (2 ) — Provision for income taxes (14 )% 33 % 34 % Deferred tax assets and liabilities resulted from the following: December 31, (In millions) 2017 2016 Deferred tax assets: Employee benefits $ 348 $ 578 Environmental 16 34 Deferred revenue 21 31 Net operating loss carryforwards 12 23 Other 23 27 Total deferred tax assets 420 693 Deferred tax liabilities: Property, plant and equipment 1,603 2,591 Inventories 473 707 Investments in subsidiaries and affiliates 912 1,145 Other 73 94 Total deferred tax liabilities 3,061 4,537 Net deferred tax liabilities $ 2,641 $ 3,844 Net deferred tax liabilities were classified in the consolidated balance sheets as follows: December 31, (In millions) 2017 2016 Assets: Other noncurrent assets $ 13 $ 17 Liabilities: Deferred income taxes 2,654 3,861 Net deferred tax liabilities $ 2,641 $ 3,844 Tax carryforwards – At December 31, 2017 and 2016 , federal operating loss carryforwards were $5 million and $18 million , respectively, which expire in 2022 through 2036 . As of December 31, 2017 and 2016 , state and local operating loss carryforwards were $8 million , which expire in 2017 through 2036 . The decrease in both the federal and state loss carryforwards was due to the utilization of loss carryforwards made available to MPC as a result of the reorganization transactions which simplified the MPLX ownership structure as discussed in Note 4 . Valuation allowances – As of December 31, 2017 and 2016 , $11 million and $10 million of valuation allowances have been recorded against foreign tax credits and state net operating losses due to the expectation that these deferred tax assets are not likely to be realized. MPC is continuously undergoing examination of its U.S. federal income tax returns by the Internal Revenue Service (“IRS”). Since 2012, we have continued to participate in the Compliance Assurance Process (“CAP”). CAP is a real-time audit of the U.S. Federal income tax return that allows the IRS, working in conjunction with MPC, to determine tax return compliance with the U.S. Federal tax law prior to filing the return. This program provides us with greater certainty about our tax liability for years under examination by the IRS. IRS audits have been completed through the 2009 tax year. We believe adequate provision has been established for potential tax in periods not closed to examination. Further, we are routinely involved in U.S. state income tax audits. We believe all other audits will be resolved with the amounts provided for these liabilities. As of December 31, 2017 , our income tax returns remain subject to examination in the following major tax jurisdictions for the tax years indicated: United States Federal 2010 - 2016 States 2008 - 2016 The following table summarizes the activity in unrecognized tax benefits: (In millions) 2017 2016 2015 January 1 balance $ 7 $ 12 $ 12 Additions for tax positions of prior years 13 6 — Reductions for tax positions of prior years — (10 ) — Settlements (1 ) (1 ) — December 31 balance $ 19 $ 7 $ 12 If the unrecognized tax benefits as of December 31, 2017 were recognized, $10 million would affect our effective income tax rate. There were $10 million of uncertain tax positions as of December 31, 2017 for which it is reasonably possible that the amount of unrecognized tax benefits would significantly decrease during the next twelve months. 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 filed a U.S. Tax Court petition disputing these adjustments during the fourth quarter of 2017. We received an FPAA for taxable years 2011-2014 for items resulting from the Marathon Oil IRS dispute discussed above. We filed 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 25 for indemnification information. Interest and penalties related to income taxes are recorded as part of the provision for income taxes. Such interest and penalties were net expenses (benefits) of $3 million , $(5) million and $3 million in 2017 , 2016 and 2015 , respectively. As of December 31, 2017 and 2016 , $17 million and $13 million of interest and penalties were accrued related to income taxes.

Inventories

Inventories	12 Months Ended
	Dec. 31, 2017
Inventory Disclosure [Abstract]
Inventories	Inventories December 31, (In millions) 2017 2016 Crude oil and refinery feedstocks $ 2,056 $ 2,208 Refined products 2,839 2,810 Materials and supplies 494 485 Merchandise 161 153 Total $ 5,550 $ 5,656 The LIFO method accounted for 90 percent and 91 percent of total inventory value at December 31, 2017 and 2016 , respectively. Current acquisition costs of inventories were estimated to exceed the LIFO inventory value at December 31, 2017 and 2016 by $1.21 billion and $308 million , respectively. During 2017 , we recorded LIFO liquidations caused primarily by permanently decreased levels in our crude oil inventory. Cost of revenues increased and income from operations decreased by $7 million for the year ended December 31, 2017 due to LIFO liquidations. There were no material liquidations of LIFO inventories in 2016 . During 2015 , we recorded LIFO liquidations caused by permanently decreased levels in crude oil and refined products inventory levels. Cost of revenues increased and income from operations decreased by $78 million for the year ended December 31, 2015 due to these LIFO liquidations.

Equity Method Investments

Equity Method Investments	12 Months Ended
	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments	Equity Method Investments Ownership as of Carrying value at December 31, December 31, (In millions) 2017 2017 2016 Centennial 50% $ 35 $ 35 Centrahoma Processing LLC (a) 40% 121 104 Crowley Coastal Partners 50% 188 184 Explorer (a) 25% 89 94 Illinois Extension Pipeline (a) 35% 284 293 LOOP (b) 51% 282 277 MarEn Bakken Company LLC (a) 25% 520 — MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C. (a) 67% 164 67 MarkWest Utica EMG (a) 56% 2,139 2,224 PFJ Southeast 29% 328 283 Sherwood Midstream (a) 50% 236 — Sherwood Midstream Holdings LLC (a)(c) 69% 165 — TAAE 45% 39 33 TACE 61% 32 33 TAEI (d) —% — 15 TAME (d) 67% 33 18 Other MPLX investments (a) 67 76 Other 65 91 Total $ 4,787 $ 3,827 (a) Ownership interest held by MPLX as of December 31, 2017 . (b) MPLX held a 41 percent ownership interest as of December 31, 2017 . (c) Excludes Sherwood Midstream LLC’s investment in Sherwood Midstream Holdings LLC. (d) On January 1, 2017, we contributed our 34 percent interest in TAEI to TAME in exchange for a 17 percent in TAME. Summarized financial information for equity method investees is as follows: (In millions) 2017 2016 2015 Income statement data: Revenues and other income $ 6,235 $ 2,421 $ 1,390 Income (loss) from operations 1,075 (116 ) 332 Net income (loss) 922 (250 ) 239 Balance sheet data – December 31: Current assets $ 860 $ 711 Noncurrent assets 10,854 8,170 Current liabilities 547 884 Noncurrent liabilities 1,714 1,462 As of December 31, 2017 , the carrying value of our equity method investments was $1.17 billion higher than the underlying net assets of investees. This basis difference is being amortized or accreted into net income over the remaining estimated useful lives of the underlying net assets, except for $509 million of excess related to goodwill and other assets. Centennial experienced a significant reduction in shipment volumes in the second half of 2011 that has continued through 2017. At December 31, 2017, Centennial was not shipping product. As a result, we continued to evaluate the carrying value of our equity investment in Centennial. We concluded that no impairment was required given our assessment of its fair value based on market participant assumptions for various potential uses and future cash flows of Centennial’s assets. If market conditions were to change and the owners of Centennial are unable to find an alternative use for the assets, there could be a future impairment of our Centennial interest. As of December 31, 2017 , our equity investment in Centennial was $35 million and we had a $25 million guarantee associated with 50 percent of Centennial’s outstanding debt. See Note 25 for additional information on the debt guarantee. Dividends and partnership distributions received from equity method investees (excluding distributions that represented a return of capital previously contributed) were $388 million , $291 million and $113 million in 2017 , 2016 and 2015 .

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment (In millions) Estimated Useful Lives December 31, 2017 2016 (a) Refining & Marketing 4 - 30 years $ 19,490 $ 18,590 Speedway 4 - 25 years 5,358 5,078 Midstream 3 - 49 years 14,898 13,521 Corporate and Other 4 - 40 years 792 817 Total 40,538 38,006 Less accumulated depreciation 14,095 12,241 Property, plant and equipment, net $ 26,443 $ 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. Property, plant and equipment includes gross assets acquired under capital leases of $576 million and $505 million at December 31, 2017 and 2016 , respectively, with related amounts in accumulated depreciation of $237 million and $202 million at December 31, 2017 and 2016 . Property, plant and equipment includes construction in progress of $2.20 billion and $2.02 billion at December 31, 2017 and 2016 , respectively, which primarily relates to capital projects at our refineries and midstream facilities.

Goodwill and Intangibles

Goodwill and Intangibles	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangibles	Goodwill and Intangibles Goodwill Goodwill is tested for impairment on an annual basis and when events or changes in circumstances indicate the fair value of a reporting unit with goodwill has been reduced below the carrying value of the net assets of the reporting unit. In 2017 , no impairment was required based on our annual test. In 2016 , we recorded an impairment of goodwill as outlined below based on an interim impairment analysis. During the first quarter of 2016, MPLX, our consolidated subsidiary, determined that an interim impairment analysis of the goodwill recorded in connection with the MarkWest Merger was necessary based on consideration of a number of first quarter events and circumstances, including i) continued deterioration of near-term commodity prices as well as longer term pricing trends, ii) recent guidance on reductions to forecasted capital spending, the slowing of drilling activity and the resulting reduced production growth forecasts released or communicated by MPLX’s producer customers and iii) increases in the cost of capital. The combination of these factors was considered to be a triggering event requiring an interim impairment test. Based on the first step of the interim goodwill impairment analysis, the fair value for three of the reporting units to which goodwill was assigned in connection with the MarkWest Merger was less than their respective carrying value. In step two of the impairment analysis, the implied fair values of the goodwill were compared to the carrying values within those reporting units. Based on this assessment, it was determined that goodwill was impaired in two of the reporting units. Accordingly, MPLX recorded an impairment charge of approximately $129 million in the first quarter of 2016. In the second quarter of 2016, MPLX completed its purchase price allocation, which resulted in an additional $1 million of impairment expense that would have been recorded in the first quarter of 2016 had the purchase price allocation been completed as of that date. This adjustment to the impairment expense was the result of completing an evaluation of the deferred tax liabilities associated with the MarkWest Merger and their impact on the resulting goodwill that was recognized. The fair value of the reporting units for the 2016 interim goodwill impairment analysis was determined based on applying the discounted cash flow method, which is an income approach, and the guideline public company method, which is a market approach. The discounted cash flow fair value estimate was based on known or knowable information at the interim measurement date. The significant assumptions that were used to develop the estimates of the fair values under the discounted cash flow method include management’s best estimates of the expected future results and discount rates, which ranged from 10.5 percent to 11.5 percent . Fair value determinations require considerable judgment and are sensitive to changes in underlying assumptions and factors. As a result, there can be no assurance that the estimates and assumptions made for purposes of the 2016 interim goodwill impairment test will prove to be an accurate prediction of the future. The changes in the carrying amount of goodwill for 2016 and 2017 were as follows: (In millions) Refining & Marketing Speedway Midstream Total Balance at January 1, 2016 $ 539 $ 853 $ 2,627 $ 4,019 Purchase price allocation adjustments — — (241 ) (241 ) Disposition (a) — (61 ) — (61 ) Impairment — — (130 ) (130 ) Transfer of assets related to dropdowns (b) (20 ) — 20 — Balance at December 31, 2016 $ 519 $ 792 $ 2,276 $ 3,587 Disposition (a) — (1 ) — (1 ) Balance at December 31, 2017 $ 519 $ 791 $ 2,276 $ 3,586 (a) Goodwill associated with our former Speedway travel plaza locations that are now part of the PFJ Southeast joint venture. The amount was included in the initial basis for our equity method investment in the joint venture. (b) Prior period balances have been recast in connection with the March 1, 2017 contribution of assets to MPLX. See Note 1 for additional information. Intangible Assets Our intangible assets as of December 31, 2017 and 2016 are as follows: (In millions) Refining & Marketing Speedway Midstream Total Balance at December 31, 2017 Customer contracts and relationships $ 120 $ 1 $ 533 $ 654 Royalty agreements 129 — — 129 Favorable lease contract terms — 56 — 56 Other (a) 73 75 — 148 Gross $ 322 $ 132 $ 533 $ 987 Accumulated amortization (143 ) (39 ) (79 ) (261 ) Net $ 179 $ 93 $ 454 $ 726 Balance at December 31, 2016 Customer contracts and relationships $ 102 $ 1 $ 533 $ 636 Royalty agreements 128 — — 128 Favorable lease contract terms 1 57 — 58 Other (a) 27 75 — 102 Gross $ 258 $ 133 $ 533 $ 924 Accumulated amortization (123 ) (35 ) (41 ) (199 ) Net $ 135 $ 98 $ 492 $ 725 (a) The Refining & Marketing and Speedway segments include unamortized intangible assets of $48 million and $46 million , respectively, which are primarily emission allowance credits and trademarks. In December 2017, we accepted non-cash consideration as part of a litigation settlement agreement. The non-cash consideration consisted of emission allowance credits with an estimated fair value of $45 million . The emission allowance credits received in the settlement are classified as indefinite lived intangible assets, but can become finite lived intangible assets once retired and assigned to a permit for a capital project. The fair value was determined using an income approach and is classified as Level 3. Amortization expense for 2017 and 2016 was $52 million and $55 million , respectively. Estimated future amortization expense related to the intangible assets at December 31, 2017 is as follows: (In millions) 2018 $ 52 2019 52 2020 50 2021 49 2022 48

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 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 December 31, 2017 and 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. December 31, 2017 Fair Value Hierarchy (In millions) Level 1 Level 2 Level 3 Netting and Collateral (a) Net Carrying Value on Balance Sheet (b) Collateral Pledged Not Offset Commodity derivative instruments, assets $ 127 $ — $ — $ (118 ) $ 9 $ 8 Other assets 3 — — N/A 3 — Total assets at fair value $ 130 $ — $ — $ (118 ) $ 12 $ 8 Commodity derivative instruments, liabilities $ 126 $ — $ 2 $ (126 ) $ 2 $ — Embedded derivatives in commodity contracts (c) — — 64 — 64 — Total liabilities at fair value $ 126 $ — $ 66 $ (126 ) $ 66 $ — 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 December 31, 2017 , cash collateral of $8 million was netted with mark-to-market derivative liabilities. As of December 31, 2016 , cash collateral of $24 million was netted with mark-to-market derivative liabilities. (b) We have no derivative contracts which are subject to master netting arrangements reflected gross on the balance sheet. (c) Includes $12 million and $13 million classified as current as of December 31, 2017 and 2016 , respectively. (d) Includes $130 million classified as current as of 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 at December 31, 2017 used significant unobservable inputs including: (1) NGL prices interpolated and extrapolated due to inactive markets ranging from $0.24 to $1.45 per gallon and (2) the probability of renewal of 60 percent for the first five -year term and 80 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 as of December 31, 2016 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 is 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 final contingent consideration payment was calculated using actual crack spread and refinery throughput data resulting in a value of $131 million when capped by the maximum total payout of $700 million . The balance of $131 million was paid on April 12, 2017. The following is a reconciliation of the net beginning and ending balances recorded for net assets and liabilities classified as Level 3 in the fair value hierarchy. (In millions) 2017 2016 2015 Beginning balance $ 190 $ 342 $ 478 Contingent consideration payment (a) (131 ) (200 ) (189 ) Net derivative positions assumed - MarkWest Merger — — 31 Unrealized and realized losses included in net income 25 55 20 Settlements of derivative instruments (18 ) (7 ) 2 Ending balance $ 66 $ 190 $ 342 The amount of total (gains) losses for the period included in earnings attributable to the change in unrealized (gains) losses relating to assets still held at the end of period: Derivative instruments $ 8 $ 32 $ (7 ) Contingent consideration agreement 1 13 28 Total $ 9 $ 45 $ 21 (a) On the consolidated statements of cash flows for 2017, 2016, and 2015, $89 million , $164 million and $175 million , respectively, of the contingent earnout payment to BP was included as a financing activity with the remainder included as an operating activity. See Note 18 for the income statement impacts of our derivative instruments. Fair Values – Nonrecurring The following table shows the values of assets, by major category, measured at fair value on a nonrecurring basis in periods subsequent to their initial recognition. Year Ended December 31, 2017 2016 2015 (In millions) Fair Value Impairment Fair Value Impairment Fair Value Impairment Equity method investments $ — $ — $ 42 $ 356 $ — $ — Goodwill — — — 130 — — Property, plant and equipment, net — — — — — 144 During the third quarter of 2016, Enbridge Energy Partners announced that its affiliate, North Dakota Pipeline, would withdraw certain pending regulatory applications for the Sandpiper pipeline project and that the project would be deferred indefinitely. These decisions were considered to indicate an impairment of the costs capitalized to date on the project. As the operator of North Dakota Pipeline and the entity responsible for maintaining its financial records, Enbridge completed a fixed asset impairment analysis as of August 31, 2016, in accordance with ASC Topic 360. Based on the estimated liquidation value of the fixed assets, an impairment charge was recorded by North Dakota Pipeline. Based on our 37.5 percent ownership of North Dakota Pipeline, we recognized approximately $267 million of this charge in the third quarter of 2016 through “Income (loss) from equity method investments” on the accompanying consolidated statements of income, which impaired virtually all of our $301 million investment in the project. Also, in accordance with ASC Topic 323, we completed an assessment to determine any additional equity method impairment charge to be recorded on our consolidated financial statements resulting from an other-than-temporary impairment. The result of this analysis indicated no additional charge was required to be recorded. The fixed assets of North Dakota Pipeline related to the Sandpiper pipeline project consist primarily of project management and engineering costs, pipe, valves, motors and other equipment, land and easements. The fair value of fixed assets was estimated based on a market approach using the estimated price that would be received to sell pipe, land and other related equipment in its current condition, considering the current market conditions for sale of these assets and length of disposal period. The valuation considered a range of potential selling prices from various alternatives that could be used to dispose of these assets. As such, the fair value of the North Dakota Pipeline equity method investment and its underlying assets represents a Level 3 measurement. As a result, actual results may differ from the estimates and assumptions made for purposes of this impairment analysis. North Dakota Pipeline is in the process of disposing of these assets. During the second quarter of 2016, forecasts for Ohio Condensate, an equity method investment, were reduced in line with updated forecasts for customer requirements. As the operator of that entity responsible for maintaining its financial records, we completed a fixed asset impairment analysis as of June 30, 2016, in accordance with ASC Topic 360, to determine the potential fixed asset impairment charge. The resulting fixed asset impairment charge recorded within Ohio Condensate’s financial statements was $96 million . Based on our 60 percent ownership of Ohio Condensate, approximately $58 million was recorded in the second quarter of 2016 in “Income (loss) from equity method investments” on the accompanying consolidated statements of income. Our investment in Ohio Condensate, which was established at fair value in connection with the MarkWest Merger, exceeded its proportionate share of the underlying net assets. Therefore, in conjunction with the ASC Topic 360 impairment analysis, we completed an equity method impairment analysis in accordance with ASC Topic 323 to determine the potential additional equity method impairment charge to be recorded on our consolidated financial statements resulting from an other-than-temporary impairment. As a result, an additional impairment charge of approximately $31 million was recorded in the second quarter of 2016 in “Income (loss) from equity method investments” on the accompanying consolidated statements of income, which eliminated the basis differential established in connection with the MarkWest Merger. The fair value of Ohio Condensate and its underlying assets was determined based upon applying the discounted cash flow method, which is an income approach, and the guideline public company method, which is a market approach. The discounted cash flow fair value estimate is based on known or knowable information at the interim measurement date. The significant assumptions that were used to develop the estimate of the fair value under the discounted cash flow method include management’s best estimates of the expected future results using a probability weighted average set of cash flow forecasts and a discount rate of 11.2 percent . Fair value determinations require considerable judgment and are sensitive to changes in underlying assumptions and factors. As such, the fair value of the Ohio Condensate equity method investment and its underlying assets represents a Level 3 measurement. As a result, actual results may differ from the estimates and assumptions made for purposes of this impairment analysis. See Note 16 for additional information on the goodwill impairment. In the third quarter of 2015, we decided to cancel the ROUX project at our Garyville refinery. The work completed on the project through September 30, 2015 had no alternate use or net salvage value; therefore, we fully impaired the $144 million of cost capitalized for the project through that date. The fair value of our investment in the project was determined using an income approach and is classified as Level 3. Fair Values – Reported The following table summarizes financial instruments on the basis of their nature, characteristics and risk at December 31, 2017 and 2016 , excluding the derivative financial instruments and contingent consideration reported above. December 31, 2017 2016 (In millions) Fair Value Carrying Value Fair Value Carrying Value Financial assets: Investments $ 29 $ 2 $ 25 $ 2 Other 17 17 21 21 Total financial assets $ 46 $ 19 $ 46 $ 23 Financial liabilities: Long-term debt (a) $ 13,893 $ 12,642 $ 10,892 $ 10,297 Deferred credits and other liabilities 122 109 121 109 Total financial liabilities $ 14,015 $ 12,751 $ 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	12 Months Ended
	Dec. 31, 2017
Summary of Derivative Instruments [Abstract]
Derivatives	Derivatives For further information regarding the fair value measurement of derivative instruments, including any effect of master netting agreements or collateral, see Note 17 . See Note 2 for a discussion of the types of derivatives we use and the reasons for them. We do not designate any of our commodity derivative instruments as hedges for accounting purposes. The following table presents the gross fair values of derivative instruments, excluding cash collateral, and where they appear on the consolidated balance sheets as of December 31, 2017 and 2016 : (In millions) December 31, 2017 Balance Sheet Location Asset Liability Commodity derivatives Other current assets $ 127 $ 126 Other current liabilities (a) — 14 Deferred credits and other liabilities (a) — 52 (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. Derivatives not Designated as Accounting Hedges Derivatives that are not designated as accounting hedges may include commodity derivatives used to hedge price risk on (1) inventories, (2) fixed price sales of refined products, (3) the acquisition of foreign-sourced crude oil, (4) the acquisition of ethanol for blending with refined products, (5) sale of NGLs and (6) the purchase of natural gas. The table below summarizes open commodity derivative contracts for crude oil and refined products as of December 31, 2017 . Position Total Barrels (In thousands) Crude Oil (a) Exchange-traded Long 23,299 Exchange-traded Short (25,199 ) (a ) 99.8 percent of the exchange-traded contracts expire in the first quarter of 2018 . Position Total Gallons (In thousands) Refined Products (a) Exchange-traded Long 257,460 Exchange-traded Short (236,460 ) OTC Short (9,587 ) (a ) 100 percent of the exchange-traded contracts expire in the first quarter of 2018 . The following table summarizes the effect of all commodity derivative instruments in our consolidated statements of income: (In millions) Gain (Loss) Income Statement Location 2017 2016 2015 Sales and other operating revenues $ 5 $ (13 ) $ 19 Cost of revenues (26 ) (167 ) 294 Total $ (21 ) $ (180 ) $ 313

Debt

Debt	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt	Debt Our outstanding borrowings at December 31, 2017 and 2016 consisted of the following: December 31, (In millions) 2017 2016 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 Capital lease obligations due 2018-2033 356 311 MPLX LP: MPLX term loan facility due 2019 — 250 MPLX bank revolving credit facility due 2022 505 — 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 — MPLX capital lease obligations due 2020 7 8 Total 13,418 11,069 Unamortized debt issuance costs (59 ) (44 ) Unamortized discount (a) (413 ) (453 ) Amounts due within one year (624 ) (28 ) Total long-term debt due after one year $ 12,322 $ 10,544 (a) Includes $374 million and $420 million unamortized discount as of December 31, 2017 and December 31, 2016 , respectively, related to the difference at the time of the acquisition between the fair value and the principal amount of assumed MarkWest debt. The following table shows five years of scheduled debt payments. (In millions) 2018 $ 626 2019 27 2020 683 2021 1,031 2022 537 Commercial Paper On February 26, 2016, we established a commercial paper program that allows us to have a maximum of $2 billion in commercial paper outstanding, with maturities up to 397 days from the date of issuance. We do not intend to have outstanding commercial paper borrowings in excess of available capacity under our bank revolving credit facilities. During 2017 , we borrowed and repaid $300 million under the commercial paper program. At December 31, 2017 , we had no amounts outstanding under the commercial paper program. MPC Revolving Credit Agreements On July 21, 2017, we entered into credit agreements with a syndicate of lenders to replace our previous $2.5 billion four -year revolving credit facility due in 2020 and our previous $1 billion 364 -day credit agreement, dated as of July 20, 2016, which expired on July 19, 2017. The new agreements provide for a five -year $2.5 billion bank revolving credit agreement (“MPC five-year credit agreement”) that expires in July 2022 and a 364 -day $1 billion bank revolving credit agreement (“MPC 364-day credit agreement” and together with the MPC five-year credit agreement, the “MPC credit agreements”) that expires in July 2018 . Under the MPC five-year credit agreement, we have an option to increase the aggregate commitments by up to an additional $500 million , subject to, among other conditions, the consent of the lenders whose commitments would be increased. In addition, we may request up to two one -year extensions of the maturity date of the MPC five-year revolving credit agreement subject to, among other conditions, the consent of lenders holding a majority of the commitments, provided that the commitments of any non-consenting lenders will terminate on the then-effective maturity date. The MPC five-year revolving credit agreement includes sub-facilities for swingline loans of up to $100 million and letters of credit of up to $1.8 billion , subject to the agreement of one of more of the lenders to increase their issuing commitments thereunder. Borrowings under the MPC credit agreements bear interest, at our election, at either the Adjusted LIBO Rate or the Alternate Base Rate (both as defined in the MPC credit agreements), plus an applicable margin . We are charged various fees and expenses under the MPC credit agreements, including administrative agent fees, commitment fees on the unused portion of the commitments and fees related to issued and outstanding letters of credit. The applicable margin to the benchmark interest rates and the commitment fees payable under the MPC credit agreements fluctuate from time-to-time based on our credit ratings. The MPC credit agreements contain certain representations and warranties, affirmative and restrictive covenants and events of default that we consider to be usual and customary for arrangements of this type, including a financial covenant that requires us to maintain a ratio of Consolidated Net Debt to Total Capitalization (each as defined in the MPC credit agreements) of no greater than 0.65 to 1.00 as of the last day of each fiscal quarter. Other covenants, among other things, restrict our ability and/or the ability of certain of our subsidiaries to incur debt, create liens on assets or enter into transactions with affiliates. As of December 31, 2017 , we were in compliance with the covenants contained in the MPC credit agreements. There were no borrowings or letters of credit outstanding at December 31, 2017 . Trade Receivables Securitization Facility On December 18, 2013, we entered into a trade receivables securitization facility (“trade receivables facility”) with a group of committed purchasers and letter of credit issuers evidenced by a receivables purchase agreement and receivables sales agreement. On July 20, 2016, we amended our trade receivables securitization facility to, among other things, reduce the capacity from $1 billion to $750 million and to extend the maturity date to July 19, 2019 . The reduction in capacity reflected the lower refined product price environment. The trade receivables facility consists of one of our wholly-owned subsidiaries, Marathon Petroleum Company LP (“MPC LP”), selling or contributing on an on-going basis all of its trade receivables (including trade receivables acquired from Marathon Petroleum Trading Canada LLC, a wholly-owned subsidiary of MPC LP), together with all related security and interests in the proceeds thereof, without recourse, to another wholly-owned, bankruptcy-remote special purpose subsidiary, MPC Trade Receivables Company LLC (“TRC”), in exchange for a combination of cash, equity and/or a subordinated note issued by TRC to MPC LP. TRC, in turn, has the ability to sell undivided ownership interests in qualifying trade receivables, together with all related security and interests in the proceeds thereof, without recourse, to the purchasing group in exchange for cash proceeds. The trade receivables facility also provides for the issuance of letters of credit up to $750 million , provided that the aggregate credit exposure of the purchasing group, including outstanding letters of credit, may not exceed the lesser of $750 million or the balance of our eligible trade receivables at any one time. To the extent that TRC retains an ownership interest in the receivables it has purchased or received from MPC LP, such interest will be included in our consolidated financial statements solely as a result of the consolidation of the financial statements of TRC with those of MPC. The receivables sold or contributed to TRC are available first and foremost to satisfy claims of the creditors of TRC and are not available to satisfy the claims of creditors of MPC. TRC has granted a security interest in all of its assets to the purchasing group to secure its obligations under the Receivables Purchase Agreement. Proceeds from the sale of undivided percentage ownership interests in qualifying receivables under the trade receivables facility are reflected as debt on our consolidated balance sheet. We remain responsible for servicing the receivables sold to the purchasing group. TRC pays floating-rate interest charges and usage fees on amounts outstanding under the trade receivables facility, if any, unused fees on the portion of unused commitments and certain other fees related to the administration of the facility and letters of credit that are issued and outstanding under the trade receivables facility. The receivables purchase agreement and receivables sale agreement contain representations and covenants that we consider usual and customary for arrangements of this type. Trade receivables are subject to customary criteria, limits and reserves before being deemed to qualify for sale by TRC pursuant to the trade receivables facility. In addition, further purchases of qualified trade receivables under the trade receivables facility are subject to termination, and TRC may be subject to default fees, upon the occurrence of certain amortization events that are included in the receivables purchase agreement, all of which we consider to be usual and customary for arrangements of this type. At December 31, 2017 , we were in compliance with the covenants contained in the receivables purchase agreement and receivables sale agreement. There were no borrowings or letters of credit outstanding under the trade receivables facility at December 31, 2017 . As of December 31, 2017 , eligible trade receivables supported borrowings and letter of credit issuances of $750 million . MPC Term Loan Agreement On August 26, 2014 , we entered into a $700 million five -year senior unsecured term loan credit agreement (“term loan agreement”) with a syndicate of lenders to fund a portion of the purchase price for the acquisition of Hess’ Retail Operations and Related Assets. The term loan was drawn in full on September 24, 2014. The term loan agreement matures on September 24, 2019 and may be prepaid at any time without premium or penalty. We pay certain customary fees under the term loan agreement, including an annual administrative fee to the administrative agent. On September 30, 2016, we prepaid $500 million under the MPC term loan agreement with available cash on hand. On March 31, 2017, we repaid the remaining $200 million outstanding under the MPC term loan agreement with available cash on hand. MPLX Credit Agreement On July 21, 2017, MPLX entered into a credit agreement with a syndicate of lenders to replace MPLX’s 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 (“MPLX credit agreement”). The MPLX credit agreement includes letter of credit issuing capacity of up to approximately $222 million and swingline loan capacity of up to $100 million . The revolving borrowing capacity may be increased by up to an additional $500 million , subject to certain conditions, including the consent of the lenders whose commitments would increase. In addition, the maturity date of the bank revolving credit facility may be extended for up to two additional one -year periods subject to the consent of the lenders holding a majority of the revolving credit facility commitments, provided that the commitments held by any non-consenting lenders will terminate on the original maturity date. Borrowings under the MPLX credit agreement bear interest, at our election, at the Adjusted LIBO Rate or the Alternate Base Rate (both as defined in the MPLX credit agreement) plus an applicable margin. MPLX is charged various fees and expenses in connection with the agreement, including administrative agent fees, commitment fees on the unused portion of the commitments and fees with respect to issued and outstanding letters of credit. The applicable margins to the benchmark interest rates and the commitment fees payable under the MPLX credit agreement fluctuate from time-to-time based on MPLX’s credit ratings. The MPLX credit agreement contains certain representations and warranties, affirmative and restrictive covenants and events of default that we consider to be usual and customary for an agreement of this type, including a financial covenant that requires MPLX to maintain a ratio of Consolidated Total Debt as of the end of each fiscal quarter to Consolidated EBITDA (both as defined in the MPLX credit agreement) for the prior four fiscal quarters of no greater than 5.0 to 1.0 (or 5.5 to 1.0 for up to two fiscal quarters following certain acquisitions). Consolidated EBITDA is subject to adjustments for certain acquisitions completed and capital projects undertaken during the relevant period. Other covenants, among other things, restrict MPLX’s ability and/or the ability of certain of its subsidiaries to incur debt, create liens on assets and enter into transactions with affiliates. As of December 31, 2017 , MPLX was in compliance with the covenants contained in the MPLX credit agreement. During 2017 , MPLX borrowed $670 million under the bank revolving credit facility, at an average interest rate of 2.7 percent , per annum, and repaid $165 million of these borrowings. At December 31, 2017 , MPLX had $505 million outstanding borrowings and $3 million of letters of credit outstanding under the bank revolving credit facility, resulting in total unused loan availability of $1.74 billion . MPLX Term Loan On July 19, 2017, MPLX prepaid the entire outstanding principal amount of its $250 million term loan with cash on hand. MPLX Senior Notes On February 10, 2017, MPLX completed a public offering of $1.25 billion aggregate principal amount of 4.125 percent unsecured senior notes due March 2027 and $1.0 billion aggregate principal amount of 5.200 percent 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	12 Months Ended
	Dec. 31, 2017
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information (In millions) 2017 2016 2015 Net cash provided by operating activities included: Interest paid (net of amounts capitalized) $ 525 $ 478 $ 272 Net income taxes paid to taxing authorities 904 140 1,605 Non-cash investing and financing activities: Capital lease obligations increase $ 71 $ — $ 1 Contribution of assets to joint venture (a) 337 273 — Intangible asset acquired (b) 45 — — Property, plant and equipment sold — — 5 Property, plant and equipment acquired — — 5 Acquisition: Fair value of MPLX units issued (c) — — 7,326 Payable to MPLX Class B unitholders — — 50 (a) 2017 includes MPLX’s contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. 2016 includes Speedway’s contribution of travel plaza locations to new joint venture with Pilot Flying J. See Note 5 . (b) See Note 16 for further information. (c) See Note 5 for further information. The consolidated statements of cash flows exclude changes to the consolidated balance sheets that did not affect cash. The following is a reconciliation of additions to property, plant and equipment to total capital expenditures: (In millions) 2017 2016 2015 Additions to property, plant and equipment per consolidated statements of cash flows $ 2,732 $ 2,892 $ 1,998 Non-cash additions to property, plant and equipment — — 5 Asset retirement expenditures (a) 2 6 1 Increase (decrease) in capital accruals 67 (127 ) 94 Total capital expenditures before acquisitions 2,801 2,771 2,098 Acquisitions (b) 250 (133 ) 11,397 Total capital expenditures $ 3,051 $ 2,638 $ 13,495 (a) Included in All other, net – Operating activities on the consolidated statements of cash flows. (b) 2017 reflects primarily the acquisition of the Ozark pipeline. 2016 includes adjustments to the fair values of property, plant and equipment, intangibles and goodwill acquired in connection with the MarkWest Merger. The 2015 acquisitions include the MarkWest Merger. The acquisition numbers above include property, plant and equipment, intangibles and goodwill.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	12 Months Ended
	Dec. 31, 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 22 64 — — 86 Amounts reclassified from accumulated other comprehensive loss: Amortization – prior service credit (a) (46 ) (3 ) — — (49 ) – actuarial loss (a) 38 2 — — 40 – settlement loss (a) 7 — — — 7 Other (b) — — — (1 ) (1 ) Tax effect 1 — — — 1 Other comprehensive income (loss) 22 63 — (1 ) 84 Balance as of December 31, 2016 $ (233 ) $ (7 ) $ 4 $ 2 $ (234 ) (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 before reclassifications 12 (38 ) 3 (23 ) Amounts reclassified from accumulated other comprehensive loss: Amortization – prior service credit (a) (39 ) (3 ) — — (42 ) – actuarial loss (a) 36 (2 ) — — 34 – settlement loss (a) 52 — — — 52 Other (b) — — — (2 ) (2 ) Tax effect (18 ) 2 — — (16 ) Other comprehensive income (loss) 43 (41 ) — 1 3 Balance as of December 31, 2017 $ (190 ) $ (48 ) $ 4 $ 3 $ (231 ) (a) These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 22 . (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	12 Months Ended
	Dec. 31, 2017
Defined Benefit Plan [Abstract]
Defined Benefit Pension and Other Postretirement Plans	Defined Benefit Pension and Other Postretirement Plans We have noncontributory defined benefit pension plans covering substantially all employees. Benefits under these plans have been based primarily on age, years of service and final average pensionable earnings. The years of service component of this formula was frozen as of December 31, 2009. Benefits for service beginning January 1, 2010 are based on a cash balance formula with an annual percentage of eligible pay credited based upon age and years of service. Eligible Speedway employees accrue benefits under a defined contribution plan for service years beginning January 1, 2010. We also have other postretirement benefits covering most employees. Health care benefits are provided through comprehensive hospital, surgical and major medical benefit provisions subject to various cost-sharing features. Retiree life insurance benefits are provided to a closed group of retirees. Other postretirement benefits are not funded in advance. Obligations and funded status – The accumulated benefit obligation for all defined benefit pension plans was $2,008 million and $1,914 million as of December 31, 2017 and 2016 . The following summarizes our defined benefit pension plans that have accumulated benefit obligations in excess of plan assets. December 31, (In millions) 2017 2016 Projected benefit obligations $ 2,164 $ 2,024 Accumulated benefit obligations 2,008 1,914 Fair value of plan assets 1,840 1,659 The following summarizes the projected benefit obligations and funded status for our defined benefit pension and other postretirement plans: Pension Benefits Other Benefits (In millions) 2017 2016 2017 2016 Change in benefit obligations: Benefit obligations at January 1 $ 2,024 $ 1,997 $ 740 $ 800 Service cost 132 114 25 32 Interest cost 75 73 30 35 Actuarial (gain) loss 150 15 61 (101 ) Benefits paid (217 ) (175 ) (30 ) (26 ) Other — — — — Benefit obligations at December 31 2,164 2,024 826 740 Change in plan assets: Fair value of plan assets at January 1 1,659 1,570 — — Actual return on plan assets 270 145 — — Employer contributions 128 119 30 26 Benefits paid from plan assets (217 ) (175 ) (30 ) (26 ) Fair value of plan assets at December 31 1,840 1,659 — — Funded status of plans at December 31 $ (324 ) $ (365 ) $ (826 ) $ (740 ) Amounts recognized in the consolidated balance sheets: Current liabilities $ (18 ) $ (18 ) $ (33 ) $ (32 ) Noncurrent liabilities (306 ) (347 ) (793 ) (708 ) Accrued benefit cost $ (324 ) $ (365 ) $ (826 ) $ (740 ) Pretax amounts recognized in accumulated other comprehensive loss: (a) Net actuarial loss $ 537 $ 645 $ 80 $ 17 Prior service credit (238 ) (276 ) (3 ) (6 ) (a) Amounts exclude those related to LOOP and Explorer, equity method investees with defined benefit pension and postretirement plans for which net losses of $17 million and less than $1 million were recorded in accumulated other comprehensive loss in 2017 , reflecting our ownership share. Components of net periodic benefit cost and other comprehensive loss – The following summarizes the net periodic benefit costs and the amounts recognized as other comprehensive loss for our defined benefit pension and other postretirement plans. Pension Benefits Other Benefits (In millions) 2017 2016 2015 2017 2016 2015 Components of net periodic benefit cost: Service cost $ 132 $ 114 $ 101 $ 25 $ 32 $ 31 Interest cost 75 73 71 30 35 32 Expected return on plan assets (100 ) (98 ) (98 ) — — — Amortization – prior service credit (39 ) (46 ) (46 ) (3 ) (3 ) (4 ) – actuarial loss 36 38 51 (2 ) 2 8 – settlement loss 52 7 4 — — — Net periodic benefit cost (a) $ 156 $ 88 $ 83 $ 50 $ 66 $ 67 Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax): Actuarial (gain) loss $ (20 ) $ (33 ) $ 69 $ 61 $ (101 ) $ (63 ) Prior service cost (b) — — — — — 13 Amortization of actuarial loss (88 ) (45 ) (55 ) 2 (2 ) (8 ) Amortization of prior service cost 39 46 46 3 3 4 Other — — — — — — Total recognized in other comprehensive loss $ (69 ) $ (32 ) $ 60 $ 66 $ (100 ) $ (54 ) Total recognized in net periodic benefit cost and other comprehensive loss $ 87 $ 56 $ 143 $ 116 $ (34 ) $ 13 (a) Net periodic benefit cost reflects a calculated market-related value of plan assets which recognizes changes in fair value over three years. (b) Includes adjustments related to the MarkWest Merger in 2015. Lump sum payments to employees retiring in 2017 , 2016 and 2015 exceeded the plan’s total service and interest costs expected for those years. Settlement losses are required to be recorded when lump sum payments exceed total service and interest costs. As a result, pension settlement expenses were recorded in 2017 , 2016 and 2015 related to our cumulative lump sum payments made during those years. The estimated net actuarial loss and prior service credit for our defined benefit pension plans that will be amortized from accumulated other comprehensive loss into net periodic benefit cost in 2018 are $36 million and $33 million , respectively. The estimated net actuarial loss and prior service credit for our other defined benefit postretirement plans that will be amortized from accumulated other comprehensive loss into net periodic benefit cost in 2018 is less than $1 million and $3 million , respectively. Plan assumptions – The following summarizes the assumptions used to determine the benefit obligations at December 31, and net periodic benefit cost for the defined benefit pension and other postretirement plans for 2017 , 2016 and 2015 . Pension Benefits Other Benefits 2017 2016 2015 2017 2016 2015 Weighted-average assumptions used to determine benefit obligation: Discount rate 3.55 % 3.90 % 4.00 % 3.70 % 4.25 % 4.50 % Rate of compensation increase 5.00 % 5.00 % 3.70 % 5.00 % 5.00 % 3.70 % Weighted-average assumptions used to determine net periodic benefit cost: Discount rate 3.85 % 3.80 % 3.70 % 4.25 % 4.50 % 4.30 % Expected long-term return on plan assets 6.50 % 6.50 % 6.75 % — % — % — % Rate of compensation increase 5.00 % 5.00 % 3.70 % 5.00 % 5.00 % 3.70 % Expected long-term return on plan assets The overall expected long-term return on plan assets assumption is determined based on an asset rate-of-return modeling tool developed by a third-party investment group. The tool utilizes underlying assumptions based on actual returns by asset category and inflation and takes into account our asset allocation to derive an expected long-term rate of return on those assets. Capital market assumptions reflect the long-term capital market outlook. The assumptions for equity and fixed income investments are developed using a building-block approach, reflecting observable inflation information and interest rate information available in the fixed income markets. Long-term assumptions for other asset categories are based on historical results, current market characteristics and the professional judgment of our internal and external investment teams. Assumed health care cost trend The following summarizes the assumed health care cost trend rates. December 31, 2017 2016 2015 Health care cost trend rate assumed for the following year: Medical: Pre-65 6.75 % 7.00 % 7.50 % Prescription drugs 8.75 % 9.00 % 7.00 % Rate to which the cost trend rate is assumed to decline (the ultimate trend rate): Medical: Pre-65 4.50 % 4.50 % 5.00 % Prescription drugs 4.50 % 4.50 % 5.00 % Year that the rate reaches the ultimate trend rate: Medical: Pre-65 2026 2026 2021 Prescription drugs 2026 2026 2021 Increases in the post-65 medical plan premium for the Marathon Petroleum Health Plan and the Marathon Petroleum Retiree Health Plan are the lower of the trend rate or four percent . Assumed health care cost trend rates have a significant effect on the amounts reported for defined benefit retiree health care plans. A one percentage point change in assumed health care cost trend rates would have the following effects: 1-Percentage- 1-Percentage- (In millions) Point Increase Point Decrease Effect on total of service and interest cost components $ 5 $ (4 ) Effect on other postretirement benefit obligations 38 (33 ) Plan investment policies and strategies The investment policies for our pension plan assets reflect the funded status of the plans and expectations regarding our future ability to make further contributions. Long-term investment goals are to: (1) manage the assets in accordance with the legal requirements of all applicable laws; (2) diversify plan investments across asset classes to achieve an optimal balance between risk and return and between income and growth of assets through capital appreciation; and (3) source benefit payments primarily through existing plan assets and anticipated future returns. The investment goals are implemented to manage the plans’ funded status volatility and minimize future cash contributions. The asset allocation strategy will change over time in response to changes primarily in funded status, which is dictated by current and anticipated market conditions, the independent actions of our investment committee, required cash flows to and from the plans and other factors deemed appropriate. Such changes in asset allocation are intended to allocate additional assets to the fixed income asset class should the funded status improve. The fixed income asset class shall be invested in such a manner that its interest rate sensitivity correlates highly with that of the plans’ liabilities. Other asset classes are intended to provide additional return with associated higher levels of risk. Investment performance and risk is measured and monitored on an ongoing basis through quarterly investment meetings and periodic asset and liability studies. At December 31, 2017 , the primary plan’s targeted asset allocation was 51 percent equity, private equity, real estate, and timber securities and 49 percent fixed income securities. Fair value measurements Plan assets are measured at fair value. The following provides a description of the valuation techniques employed for each major plan asset category at December 31, 2017 and 2016 . Cash and cash equivalents – Cash and cash equivalents include a collective fund serving as the investment vehicle for the cash reserves and cash held by third-party investment managers. The collective fund is valued at net asset value (“NAV”) on a scheduled basis using a cost approach, and is considered a Level 2 asset. Cash and cash equivalents held by third-party investment managers are valued using a cost approach and are considered Level 2. Equity – Equity investments includes common stock, mutual and pooled funds. Common stock investments are valued using a market approach, which are priced daily in active markets and are considered Level 1. Mutual and pooled equity funds are well diversified portfolios, representing a mix of strategies in domestic, international and emerging market strategies. Mutual funds are publicly registered, valued at NAV on a daily basis using a market approach and are considered Level 1 assets. Pooled funds are valued at NAV using a market approach and are considered Level 2. Fixed Income – Fixed income investments include corporate bonds, U.S. dollar treasury bonds and municipal bonds. These securities are priced on observable inputs using a combination of market, income and cost approaches. These securities are considered Level 2 assets. Fixed income also includes a well diversified bond portfolio structured as a pooled fund. This fund is valued at NAV on a daily basis using a market approach and is considered Level 2. Private Equity – Private equity investments include interests in limited partnerships which are valued using information provided by external managers for each individual investment held in the fund. These holdings are considered Level 3. Real Estate – Real estate investments consist of interests in limited partnerships. These holdings are either appraised or valued using investment manager’s assessment of assets held. These holdings are considered Level 3. Other – Other investments include two limited liability companies (“LLCs”) with no public market. The LLCs were formed to acquire timberland in the northwest U.S. These holdings are either appraised or valued using investment manager’s assessment of assets held. These holdings are considered Level 3. Other investments classified as Level 1 include publicly traded depository receipts. The following tables present the fair values of our defined benefit pension plans’ assets, by level within the fair value hierarchy, as of December 31, 2017 and 2016 . December 31, 2017 (In millions) Level 1 Level 2 Level 3 Total Cash and cash equivalents $ — $ 14 $ — $ 14 Equity: Common stocks 36 — — 36 Mutual funds 227 — — 227 Pooled funds — 507 — 507 Fixed income: Corporate — 673 1 674 Government — 98 — 98 Pooled funds — 176 — 176 Private equity — — 51 51 Real estate — — 34 34 Other 2 2 19 23 Total investments, at fair value $ 265 $ 1,470 $ 105 $ 1,840 December 31, 2016 (In millions) Level 1 Level 2 Level 3 Total Cash and cash equivalents $ — $ 24 $ — $ 24 Equity: Common stocks 71 — — 71 Mutual funds 160 — — 160 Pooled funds — 451 — 451 Fixed income: Corporate — 570 — 570 Government — 90 — 90 Pooled funds — 173 — 173 Private equity — — 60 60 Real estate — — 39 39 Other 2 — 19 21 Total investments, at fair value $ 233 $ 1,308 $ 118 $ 1,659 The following is a reconciliation of the beginning and ending balances recorded for plan assets classified as Level 3 in the fair value hierarchy: 2017 (In millions) Private Equity Real Estate Other Total Beginning balance $ 60 $ 39 $ 19 $ 118 Actual return on plan assets: Realized 11 3 — 14 Unrealized (1 ) — 1 — Purchases 2 1 1 4 Sales (21 ) (9 ) (1 ) (31 ) Ending balance $ 51 $ 34 $ 20 $ 105 2016 (In millions) Private Equity Real Estate Other Total Beginning balance $ 62 $ 50 $ 19 $ 131 Actual return on plan assets: Realized 8 5 — 13 Unrealized 2 (3 ) — (1 ) Purchases 2 1 — 3 Sales (14 ) (14 ) — (28 ) Ending balance $ 60 $ 39 $ 19 $ 118 Cash Flows Contributions to defined benefit plans – Our funding policy with respect to the funded pension plans is to contribute amounts necessary to satisfy minimum pension funding requirements, including requirements of the Pension Protection Act of 2006, plus such additional, discretionary, amounts from time to time as determined appropriate by management. In 2017 , we made pension contributions totaling $128 million . We have no required funding for 2018 , but may make voluntary contributions at our discretion. Cash contributions to be paid from our general assets for the unfunded pension and postretirement plans are estimated to be approximately $18 million and $33 million , respectively, in 2018 . Estimated future benefit payments – The following gross benefit payments, which reflect expected future service, as appropriate, are expected to be paid in the years indicated. (In millions) Pension Benefits Other Benefits 2018 $ 176 $ 33 2019 183 36 2020 161 38 2021 161 41 2022 158 42 2023 through 2027 790 229 Contributions to defined contribution plans – We also contribute to several defined contribution plans for eligible employees. Contributions to these plans totaled $116 million , $113 million and $94 million in 2017 , 2016 and 2015 , respectively. Multiemployer Pension Plan We contribute to one multiemployer defined benefit pension plan under the terms of a collective-bargaining agreement that covers some of our union-represented employees. The risks of participating in this multiemployer plan are different from single-employer plans in the following aspects: • Assets contributed to the multiemployer plan by one employer may be used to provide benefits to employees of other participating employers. • If a participating employer stops contributing to the plan, the unfunded obligations of the plan may be borne by the remaining participating employers. • If we choose to stop participating in the multiemployer plan, we may be required to pay that plan an amount based on the underfunded status of the plan, referred to as a withdrawal liability. Our participation in this plan for 2017 , 2016 and 2015 is outlined in the table below. The “EIN” column provides the Employee Identification Number for the plan. The most recent Pension Protection Act zone status available in 2017 and 2016 is for the plan’s year ended December 31, 2016 and December 31, 2015 , respectively. The zone status is based on information that we received from the plan and is certified by the plan’s actuary. Among other factors, plans in the red zone are generally less than 65 percent funded. The “FIP/RP Status Pending/Implemented” column indicates a financial improvement plan or a rehabilitation plan has been implemented. The last column lists the expiration date of the collective-bargaining agreement to which the plan is subject. There have been no significant changes that affect the comparability of 2017 , 2016 and 2015 contributions. Our portion of the contributions does not make up more than five percent of total contributions to the plan. Pension Protection Act Zone Status FIP/RP Status Pending/Implemented MPC Contributions In millions ) Surcharge Expiration Date of Collective – Bargaining Pension Fund EIN 2017 2016 2017 2016 2015 Central States, Southeast and Southwest Areas Pension Plan (a) 366044243 Red Red Implemented $ 4 $ 4 $ 4 No January 31, 2019 (a) This agreement has a minimum contribution requirement of $315 per week per employee for 2018 . A total of 282 employees participated in the plan as of December 31, 2017 . Multiemployer Health and Welfare Plan We contribute to one multiemployer health and welfare plan that covers both active employees and retirees. Through the health and welfare plan employees receive medical, dental, vision, prescription and disability coverage. Our contributions to this plan totaled $7 million , $6 million and $7 million for 2017 , 2016 and 2015 , respectively.

Stock-Based Compensation Plans

Stock-Based Compensation Plans	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation Plans	Stock-Based Compensation Plans Description of the Plans Effective April 26, 2012, our employees and non-employee directors became eligible to receive equity awards under the Amended and Restated Marathon Petroleum Corporation 2012 Incentive Compensation Plan (“MPC 2012 Plan”). The MPC 2012 Plan authorizes the Compensation Committee of our board of directors (“Committee”) to grant non-qualified or incentive stock options, stock appreciation rights, stock awards (including restricted stock and restricted stock unit awards), cash awards and performance awards to our employees and non-employee directors. Under the MPC 2012 Plan, no more than 50 million shares of our common stock may be delivered and no more than 20 million shares of our common stock may be the subject of awards that are not stock options or stock appreciation rights. In the sole discretion of the Committee, 20 million shares of our common stock may be granted as incentive stock options. Shares issued as a result of awards granted under these plans are funded through the issuance of new MPC common shares. Prior to April 26, 2012, our employees and non-employee directors were eligible to receive equity awards under the Marathon Petroleum Corporation 2011 Second Amended and Restated Incentive Compensation Plan (“MPC 2011 Plan”). Stock-based awards under the Plans We expense all share-based payments to employees and non-employee directors based on the grant date fair value of the awards over the requisite service period, adjusted for estimated forfeitures. Stock Options – We grant stock options to certain officer and non-officer employees. All of the stock options granted in 2017 fell under the MPC 2012 Plan. Stock options awarded under the MPC 2011 Plan and the MPC 2012 Plan represent the right to purchase shares of our common stock at its fair market value, which is the closing price of MPC’s common stock on the date of grant. Stock options have a maximum term of ten years from the date they are granted, and vest over a requisite service period of three years . We use the Black Scholes option-pricing model to estimate the fair value of stock options granted, which requires the input of subjective assumptions. Restricted Stock and Restricted Stock Units – We grant restricted stock and restricted stock units to employees and non-employee directors. In general, restricted stock and restricted stock units granted to employees vest over a requisite service period of three years . Restricted stock and restricted stock unit awards granted after 2011 to officers are subject to an additional one year holding period after the three-year vesting period. Restricted stock recipients who received grants in 2012 and after have the right to vote such stock; however, dividends are accrued and will be paid upon vesting. Restricted stock units granted to non-employee directors are considered to vest immediately at the time of the grant for accounting purposes, as they are non-forfeitable, but are not issued until the director’s departure from the board of directors. Restricted stock unit recipients do not have the right to vote such shares and receive dividend equivalents payable upon vesting. The non-vested shares are not transferable and are held by our transfer agent. The fair values of restricted stock are equal to the market price of our common stock on the grant date. Performance Units – We grant performance unit awards to certain officer employees. Performance units are dollar denominated. The target value of all performance units is $1.00 , with actual payout up to $2.00 per unit (up to 200 percent of target). Performance units issued under the MPC 2012 Plan have a 36 -month requisite service period. The payout value of these awards will be determined by the relative ranking of the total shareholder return (“TSR” ) of MPC common stock compared to the TSR of a select group of peer companies, as well as the Standard & Poor’s 500 Energy Index fund over an average of four measurement periods. These awards will be settled 25 percent in MPC common stock and 75 percent in cash. The number of shares actually distributed will be determined by dividing 25 percent of the final payout by the closing price of MPC common stock on the day the Committee certifies the final TSR rankings, or the next trading day if the certification is made outside of normal trading hours. The performance units paying out in cash are accounted for as liability awards and recorded at fair value with a mark-to-market adjustment made each quarter. The performance units that settle in shares are accounted for as equity awards. Total Stock-Based Compensation Expense The following table reflects activity related to our stock-based compensation arrangements: (In millions) 2017 2016 2015 Stock-based compensation expense $ 51 $ 45 $ 42 Tax benefit recognized on stock-based compensation expense 19 17 16 Cash received by MPC upon exercise of stock option awards 46 10 33 Tax benefit received for tax deductions for stock awards exercised 25 4 26 Stock Option Awards The Black Scholes option-pricing model values used to value stock option awards granted were determined based on the following weighted average assumptions: 2017 2016 2015 Weighted average exercise price per share $ 50.57 $ 35.27 $ 50.85 Expected life in years 6.3 6.2 6.0 Expected volatility 35 % 38 % 33 % Expected dividend yield 3.0 % 3.0 % 2.0 % Risk-free interest rate 2.1 % 1.4 % 1.7 % Weighted average grant date fair value of stock option awards granted $ 13.42 $ 9.84 $ 13.44 The expected life of stock options granted is based on historical data and represents the period of time that options granted are expected to be held prior to exercise. The 2017 assumption for expected volatility of our stock price reflects a weighting of 50 percent of our common stock implied volatility and 50 percent of our common stock historical volatility. The risk-free interest rate for periods within the expected life of the option is based on the U.S. Treasury yield curve in effect at the time of the grant. The following is a summary of our common stock option activity in 2017 : Number of of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Terms (in years) Aggregate Intrinsic Value (in millions) Outstanding at December 31, 2016 9,531,440 $ 28.93 Granted 1,214,112 50.57 Exercised (2,201,768 ) 21.88 Forfeited, canceled or expired (78,386 ) 41.97 Outstanding at December 31, 2017 8,465,398 33.74 Vested and expected to vest at December 31, 2017 8,445,963 33.71 5.5 $ 273 Exercisable at December 31, 2017 5,992,586 29.16 4.4 221 The intrinsic value of options exercised by MPC employees during 2017 , 2016 and 2015 was $75 million , $14 million and $60 million , respectively. As of December 31, 2017 , unrecognized compensation cost related to stock option awards was $9 million , which is expected to be recognized over a weighted average period of 1.3 years. Restricted Stock Awards The following is a summary of restricted stock award activity of our common stock in 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 579,122 50.25 36,345 53.19 RS’s Vested/RSU’s Issued (547,927 ) 42.54 (98,548 ) 29.49 Forfeited (92,876 ) 44.32 (13,750 ) 50.20 Outstanding at December 31, 2017 1,188,662 45.07 285,164 29.95 Of the 285,164 restricted stock units outstanding, 280,850 are vested and have a weighted average grant date fair value of $29.72 . These vested but unissued units are held by our non-employee directors and certain officers, are non-forfeitable and are issuable upon the director’s departure from our board of directors or officers end of employment with the company. The following is a summary of the values related to restricted stock and restricted stock unit awards held by MPC employees and non-employee directors: Restricted Stock Restricted Stock Units Intrinsic Value of Awards Vested During the Period (in millions) Weighted Average Grant Date Fair Value of Awards Granted During the Period Intrinsic Value of Awards Vested During the Period (in millions) Weighted Average Grant Date Fair Value of Awards Granted During the Period 2017 $ 28 $ 50.25 $ 5 $ 53.19 2016 17 36.17 8 40.85 2015 27 50.64 21 49.87 As of December 31, 2017 , unrecognized compensation cost related to restricted stock awards was $34 million , which is expected to be recognized over a weighted average period of 1.3 years. There was no material unrecognized compensation cost related to restricted stock unit awards. Performance Unit Awards The following table presents a summary of the 2017 activity for performance unit awards to be settled in shares: 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 (133,658 ) 0.82 Outstanding at December 31, 2017 6,851,542 0.81 The number of shares that would be issued upon target vesting, using the closing price of our common stock on December 29, 2017 would be 103,843 shares. As of December 31, 2017 , unrecognized compensation cost related to equity-classified performance unit awards was $2 million , which is expected to be recognized over a weighted average period of 1.1 years. Performance units to be settled in MPC shares have a grant date fair value calculated using a Monte Carlo valuation model, which requires the input of subjective assumptions. The following table provides a summary of these assumptions: 2017 2016 2015 Risk-free interest rate 1.5 % 1.0 % 1.0 % Look-back period (in years) 2.8 2.8 2.8 Expected volatility 36.1 % 34.2 % 30.4 % Grant date fair value of performance units granted $ 0.92 $ 0.57 $ 0.95 The risk-free interest rate for the remaining performance period as of the grant date is based on the U.S. Treasury yield curve in effect at the time of the grant. The look-back period reflects the remaining performance period at the grant date. The assumption for the expected volatility of our stock price reflects the average MPC common stock historical volatility. MPLX Awards Our wholly-owned subsidiary and the general partner of MPLX, MPLX GP LLC (“MPLX GP”), maintains a unit-based compensation plan for officers, directors and employees (including any other individual who may be considered an “employee” under a Registration Statement on Form S-8 or any successor form) of MPLX GP. The MPLX 2012 Incentive Compensation Plan (“MPLX Plan”) permits various types of equity awards including but not limited to grants of phantom units and performance units. Awards granted under the MPLX Plan will be settled with MPLX units. Total unit-based compensation expense for awards settling in MPLX LP common units was $18 million in 2017 , $10 million in 2016 and $4 million in 2015 . Additionally, approximately $15 million was included in the total MarkWest purchase price in 2015, representing MPLX LP unit-based compensation awards granted in connection with the MarkWest Merger.

Leases

Leases	12 Months Ended
	Dec. 31, 2017
Leases [Abstract]
Leases of Lessee Disclosure	Lessee We lease a wide variety of facilities and equipment under operating leases, including land and building space, office equipment, storage facilities and transportation equipment. Most long-term leases include renewal options and, in certain leases, purchase options. Future minimum commitments as of December 31, 2017 , for capital lease obligations and for operating lease obligations having initial or remaining non-cancellable lease terms in excess of one year are as follows: (In millions) Capital Lease Obligations Operating Lease Obligations 2018 $ 50 $ 255 2019 49 224 2020 54 205 2021 49 177 2022 49 152 Later years 265 463 Total minimum lease payments 516 $ 1,476 Less imputed interest costs 152 Present value of net minimum lease payments $ 364 Operating lease rental expense was: (In millions) 2017 2016 2015 Rental expense $ 301 $ 327 $ 331
Leases of Lessor Disclosure	Lessor MPLX has certain natural gas gathering, transportation and processing agreements in which it is considered to be the lessor under several implicit operating lease arrangements in accordance with U.S. GAAP. MPLX’s primary implicit lease operations relate to a natural gas gathering agreement in the Marcellus region for which it earns a fixed-fee for providing gathering services to a single producer using a dedicated gathering system. As the gathering system is expanded, the fixed-fee charged to the producer is adjusted to include the additional gathering assets in the lease. The primary term of the natural gas gathering arrangement expires in 2023 and will continue thereafter on a year to year basis until terminated by either party. Other significant implicit leases relate to a natural gas processing agreement in the Marcellus region and a natural gas processing agreement in the Southern Appalachia region for which MPLX earns minimum monthly fees for providing processing services to a single producer using a dedicated processing plant. The primary term of these natural gas processing agreements expire during 2023 and 2032. Our revenue from implicit lease arrangements, excluding executory costs, totaled approximately $218 million , $246 million and $16 million in 2017 , 2016 and 2015 , respectively. The implicit lease arrangements related to the processing facilities contain contingent rental provisions whereby we receive additional fees if the producer customer exceeds the monthly minimum processed volumes. During the year ended December 31, 2017 , we received $9 million in contingent lease payments and $7 million for the year ended December 31, 2016 . The following is a schedule of minimum future rentals on the non‑cancellable operating leases as of December 31, 2017 : (In millions) 2018 $ 194 2019 194 2020 193 2021 181 2022 172 Later years 320 Total minimum lease payments $ 1,254 The following schedule summarizes our investment in assets held for operating lease by major classes as of December 31, 2017 : (In millions) Natural gas gathering and NGL transportation pipelines and facilities $ 735 Natural gas processing facilities 644 Construction in progress 50 Property, plant and equipment 1,429 Less accumulated depreciation 153 Total property, plant and equipment $ 1,276

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 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 an accrued liability, we are unable to estimate a range of possible loss because the issues involved have not been fully developed through pleadings and discovery. However, the ultimate resolution of some of these contingencies could, individually or in the aggregate, be material. Environmental matters – We are subject to federal, state, local and foreign laws and regulations relating to the environment. These laws generally provide for control of pollutants released into the environment and require responsible parties to undertake remediation of hazardous waste disposal sites and certain other locations including presently or formerly owned or operated retail marketing sites. Penalties may be imposed for noncompliance. At December 31, 2017 and 2016 , accrued liabilities for remediation totaled $114 million and $132 million . It is not presently possible to estimate the ultimate amount of all remediation costs that might be incurred or the penalties if any that may be imposed. Receivables for recoverable costs from certain states, under programs to assist companies in clean-up efforts related to underground storage tanks at presently or formerly owned or operated retail marketing sites, were $45 million and $58 million at December 31, 2017 and 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 search at 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. The criminal investigation ended without any charges against MarkWest Liberty Midstream. With respect to the civil enforcement allegations associated with permitting or other related regulatory obligations for its launcher/receiver and compressor station facilities in the region, MarkWest Liberty Midstream and its affiliates have agreed in principle to pay a cash penalty of approximately $0.6 million and to undertake certain supplemental environmental projects with an estimated cost of approximately $2.4 million . Other Lawsuits - MPLX, MarkWest, MarkWest Liberty Midstream, MarkWest Liberty Bluestone, L.L.C., Ohio Fractionation and MarkWest Utica EMG (collectively, the “MPLX Parties”) are parties to various lawsuits with Bilfinger Westcon, Inc. (“Westcon”) that were instituted in 2016 and 2017 in the Court of Common Pleas in Butler County, Pennsylvania, the Circuit Court in Wetzel County, West Virginia, and the Court of Common Pleas in Harrison County, Ohio. The lawsuits relate to disputes regarding construction work performed by Westcon at the Bluestone, Mobley and Cadiz processing complexes in Pennsylvania, West Virginia and Ohio, respectively, and the Hopedale fractionation complex in Ohio. With respect to work performed by Westcon at the Mobley and Bluestone processing complexes, one or more of the MPLX Parties have asserted breach of contract, fraud, and with respect to work performed at the Mobley processing complex, MarkWest Liberty Midstream has also asserted negligent misrepresentation claims against Westcon. Weston has also asserted claims against one or more of the MPLX Parties regarding these construction projects for breach of contract, unjust enrichment, promissory estoppel, fraud and constructive fraud, tortious interference with contractual relations, and civil conspiracy. The MPLX Parties seek in excess of $10 million , plus an unspecified amount of punitive damages. Westcon seeks in excess of $40 million , plus an unspecified amount of punitive damages. While the ultimate outcome and impact cannot be predicted with certainty, and management is not able to provide a reasonable estimate of the potential loss or range of loss, if any, for these claims, we believe the resolution of these claims will not have a material adverse effect on its consolidated financial position, results of operations, or cash flows. In May 2015, the Kentucky attorney general filed a lawsuit against our wholly-owned subsidiary, MPC LP, in the United States District Court for the Western District of Kentucky asserting claims under federal and state antitrust statutes, the Kentucky Consumer Protection Act, and state common law. The complaint, as amended in July 2015, alleges that MPC LP used deed restrictions, supply agreements with customers and exchange agreements with competitors to unreasonably restrain trade in areas within Kentucky and seeks declaratory relief, unspecified damages, civil penalties, restitution and disgorgement of profits. At this 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 December 31, 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 $25 million as of December 31, 2017 . In connection with our 50 percent ownership in Crowley Ocean Partners, we have agreed to conditionally guarantee our portion of the obligations of the joint venture and its subsidiaries under a senior secured term loan agreement. The term loan agreement provides for loans of up to $325 million to finance the acquisition of four product tankers. MPC’s liability under the guarantee for each vessel is conditioned upon the occurrence of certain events, including if we cease to maintain an investment-grade credit rating or the charter for the relevant product tanker ceases to be in effect and is not replaced by a charter with an investment-grade company on certain defined commercial terms. As of December 31, 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 $135 million as of December 31, 2017 . Marathon Oil indemnifications – In conjunction with the Spinoff, we have entered into arrangements with Marathon Oil providing indemnities and guarantees with recorded values of $2 million as of December 31, 2017 , which consist of unrecognized tax benefits related to MPC, its consolidated subsidiaries and the RM&T Business operations prior to the Spinoff which are not already reflected in the unrecognized tax benefits described in Note 12 , and other contingent liabilities Marathon Oil may incur related to taxes. Furthermore, the separation and distribution agreement and other agreements with Marathon Oil to effect the Spinoff provide for cross-indemnities between Marathon Oil and us. In general, Marathon Oil is required to indemnify us for any liabilities relating to Marathon Oil’s historical oil and gas exploration and production operations, oil sands mining operations and integrated gas operations, and we are required to indemnify Marathon Oil for any liabilities relating to Marathon Oil’s historical refining, marketing and transportation operations. The terms of these indemnifications are indefinite and the amounts are not capped. Other guarantees – We have entered into other guarantees with maximum potential undiscounted payments totaling $93 million as of December 31, 2017 , which consist primarily 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 December 31, 2017 and 2016 , our contractual commitments to acquire property, plant and equipment and advance funds to equity method investees totaled $484 million and $487 million . The contractual commitments at December 31, 2016 included the $131 million contingent consideration associated with the acquisition of the Galveston Bay Refinery and Related Assets. See Note 17 for additional information on the contingent consideration. 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 if there are significant delays that are not due to force majeure.

Subsequent Event

Subsequent Event	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On February 1, 2018, we contributed our refining logistics assets and fuels distribution services to MPLX in exchange for $4.1 billion in cash and approximately 114 million newly issued MPLX units. MPLX financed the cash portion of the transaction with its $4.1 billion 364 -day term loan facility, which was entered into on January 2, 2018. Immediately following the dropdown, our IDRs were cancelled and our general partner economic interest was converted into a general partner non-economic interest, all in exchange for 275 million newly issued MPLX common units. We continue to control MPLX through our ownership of the general partner non-economic interest in MPLX and own approximately 64 percent of the outstanding MPLX common units as of February 1, 2018. 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 February 5, 2018, we announced our intent to redeem all of the $600 million outstanding aggregate principal amount of our 2.700 percent senior notes due on December 14, 2018. The 2018 senior notes will be redeemed on March 15, 2018, at a price equal to par plus a make whole premium, plus accrued and unpaid interest. The make whole premium will be calculated based on the market yield of the applicable treasury issue as of the redemption date as determined in accordance with the indenture governing the 2018 senior notes. Based on current treasury yields, we expect the make whole premium on the 2018 senior notes, excluding accrued and unpaid interest, to be less than $3.0 million or 0.50 percent of the face value of the notes. On February 8, 2018, MPLX issued $5.5 billion in aggregate principal amount of senior notes in a public offering, consisting of $500 million aggregate principal amount of 3.375 percent unsecured senior notes due March 2023, $1.25 billion aggregate principal amount of 4.000 percent unsecured senior notes due March 2028, $1.75 billion aggregate principal amount of 4.500 percent unsecured senior notes due April 2038, $1.5 billion aggregate principal amount of 4.700 percent unsecured senior notes due April 2048, and $500 million aggregate principal amount of 4.900 percent unsecured senior notes due April 2058. On February 8, 2018, $4.1 billion of the net proceeds were used to repay the 364-day term-loan facility, which was drawn on February 1, 2018 to fund the cash portion of the consideration MPLX paid MPC for the dropdown of assets on February 1, 2018. The remaining proceeds will be used to repay outstanding borrowings under MPLX’s revolving credit facility and intercompany loan agreement with us and for general partnership purposes.

Selected Quarterly Financial Da

Selected Quarterly Financial Data	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Data [Abstract]
Selected Quarterly Financial Data	Selected Quarterly Financial Data (Unaudited) 2017 2016 (In millions, except per share data) 1st Qtr. 2nd Qtr. 3rd Qtr. 4th Qtr. (a) 1st Qtr. 2nd Qtr. 3rd Qtr. 4th Qtr. Revenues $ 16,288 $ 18,180 $ 19,210 $ 21,055 $ 12,755 $ 16,811 $ 16,618 $ 17,155 Income from operations 292 982 1,576 1,119 75 1,315 435 553 Net income (loss) 101 574 1,004 2,125 (78 ) 783 219 289 Net income attributable to MPC 30 483 903 2,016 1 801 145 227 Net income attributable to MPC per share: Basic $ 0.06 $ 0.94 $ 1.79 $ 4.13 $ 0.003 $ 1.51 $ 0.28 $ 0.43 Diluted 0.06 0.93 1.77 4.09 0.003 1.51 0.27 0.43 Dividends paid per share 0.36 0.36 0.40 0.40 0.32 0.32 0.36 0.36 (a) During the fourth quarter of 2017, we recorded a tax benefit of approximately $1.5 billion as a result of remeasuring certain deferred tax liabilities using the lower corporate tax rate enacted under the TCJA.

Supplementary Statistics

Supplementary Statistics	12 Months Ended
	Dec. 31, 2017
Text Block [Abstract]
Supplementary Statistics	Supplementary Statistics (Unaudited) (In millions) 2017 2016 2015 Income from Operations by segment Refining & Marketing (a)(b) $ 2,321 $ 1,357 $ 3,997 Speedway (b) 732 734 673 Midstream (a) 1,339 1,048 463 Items not allocated to segments: Corporate and other unallocated items (a) (365 ) (268 ) (293 ) Pension settlement expenses (52 ) (7 ) (4 ) Litigation (29 ) — — Impairment (c) 23 (486 ) (144 ) Income from operations $ 3,969 $ 2,378 $ 4,692 Capital Expenditures and Investments (d) Refining & Marketing (a) $ 832 $ 1,054 $ 1,045 Speedway 381 303 501 Midstream (a)(e) 2,505 1,568 14,545 Corporate and Other (f) 138 144 192 Total $ 3,856 $ 3,069 $ 16,283 (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) In 2016, the Refining & Marketing and Speedway segments include an inventory LCM benefit of $345 million and $25 million , respectively. In 2015, the Refining & Marketing and Speedway segments include an inventory LCM charge of $345 million and $25 million , respectively. (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. 2015 relates to the cancellation of the Residual Oil Upgrader Expansion project. See Notes 16 and 17 to the audited consolidated financial statements. (d) Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates. (e) 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. 2015 includes $13.85 billion for the MarkWest Merger. (f) Includes capitalized interest of $55 million , $63 million and $37 million for 2017 , 2016 and 2015 , respectively. Supplementary Statistics (Unaudited) 2017 2016 2015 MPC Consolidated Refined Product Sales Volumes (mbpd) (a) 2,311 2,269 2,301 Refining & Marketing Operating Statistics Refining & Marketing refined product sales volume (mbpd) (b) 2,301 2,259 2,289 Refining & Marketing margin (dollars per barrel) (c) $ 12.60 $ 11.16 $ 15.16 Crude oil capacity utilization percent (d) 97 95 99 Refinery throughputs (mbpd): (e) Crude oil refined 1,765 1,699 1,711 Other charge and blendstocks 179 151 177 Total 1,944 1,850 1,888 Sour crude oil throughput percent 59 60 55 WTI-priced crude oil throughput percent 21 19 20 Refined product yields (mbpd): (e) Gasoline 932 900 913 Distillates 641 617 603 Propane 36 35 36 Feedstocks and special products 277 241 281 Heavy fuel oil 37 32 31 Asphalt 63 58 55 Total 1,986 1,883 1,919 Refinery direct operating costs (dollars per barrel): (f) Planned turnaround and major maintenance $ 1.72 $ 1.83 $ 1.13 Depreciation and amortization 1.43 1.47 1.39 Other manufacturing (g) 4.07 4.09 4.15 Total $ 7.22 $ 7.39 $ 6.67 Refining & Marketing Operating Statistics By Region – Gulf Coast Refinery throughputs (mbpd): (h) Crude oil refined 1,070 1,039 1,060 Other charge and blendstocks 224 195 184 Total 1,294 1,234 1,244 Sour crude oil throughput percent 71 73 68 WTI-priced crude oil throughput percent 11 8 6 Refined product yields (mbpd): (h) Gasoline 546 514 534 Distillates 405 399 392 Propane 26 26 26 Feedstocks and special products 311 286 286 Heavy fuel oil 25 21 15 Asphalt 17 15 16 Total 1,330 1,261 1,269 Refinery direct operating costs (dollars per barrel): (f) Planned turnaround and major maintenance $ 1.75 $ 2.09 $ 0.81 Depreciation and amortization 1.12 1.14 1.09 Other manufacturing (g) 3.74 3.70 3.88 Total $ 6.61 $ 6.93 $ 5.78 Supplementary Statistics (Unaudited) 2017 2016 2015 Refining & Marketing Operating Statistics By Region – Midwest Refinery throughputs (mbpd): (h) Crude oil refined 695 660 651 Other charge and blendstocks 33 39 39 Total 728 699 690 Sour crude oil throughput percent 40 40 34 WTI-priced crude oil throughput percent 37 38 43 Refined product yields (mbpd): (h) Gasoline 386 386 379 Distillates 236 218 211 Propane 11 11 12 Feedstocks and special products 42 35 38 Heavy fuel oil 13 12 17 Asphalt 46 43 39 Total 734 705 696 Refinery direct operating costs (dollars per barrel): (f) Planned turnaround and major maintenance $ 1.48 $ 1.15 $ 1.64 Depreciation and amortization 1.81 1.88 1.83 Other manufacturing (g) 4.26 4.29 4.36 Total $ 7.55 $ 7.32 $ 7.83 Speedway Operating Statistics (i) Convenience stores at period-end 2,744 2,733 2,766 Gasoline and distillate sales (millions of gallons) 5,799 6,094 6,038 Gasoline & distillate margin (dollars per gallon) (j) $ 0.1738 $ 0.1656 $ 0.1823 Merchandise sales (in millions) $ 4,893 $ 5,007 $ 4,879 Merchandise margin (in millions) $ 1,402 $ 1,435 $ 1,368 Merchandise margin percent 28.7 % 28.7 % 28.0 % Same store gasoline sales volume (period over period) (1.3 )% (0.4 )% (0.3 )% Same store merchandise sales (period over period) (k) 1.2 % 3.2 % 4.1 % Midstream Operating Statistics Crude oil and refined product pipeline throughputs (mbpd) (l) 3,377 2,948 2,829 Terminal throughput (mbpd) (m) 1,477 1,505 — Gathering system throughput (MMcf/d) (n) 3,608 3,275 3,075 Natural gas processed (MMcf/d) (n) 6,460 5,761 5,468 C2 (ethane) + NGLs (natural gas liquids) fractionated (mbpd) (n) 394 335 307 (a) Total average daily volumes of refined product sales to wholesale, branded and retail customers. (b) Includes intersegment sales. (c) Excludes LCM inventory valuation adjustments. Sales revenue less cost of refinery inputs and purchased products, divided by total refinery throughputs. Comparable prior period information for R&M margin has been recast in connection with the contribution of certain pipeline assets to MPLX on March 1, 2017. (d) Based on calendar day capacity, which is an annual average that includes downtime for planned maintenance and other normal operating activities. (e) Excludes inter-refinery volumes of 78 mbpd, 83 mbpd and 46 mbpd for 2017 , 2016 and 2015 , respectively. (f) Per barrel of total refinery throughputs. (g) Includes utilities, labor, routine maintenance and other operating costs. (h) Includes inter-refinery transfer volumes. (i) 2017 operating statistics do not reflect any information for the 41 travel centers contributed to PFJ Southeast, whereas they are reflected in prior years. (j) 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. (k) Excludes cigarettes. (l) Includes common-carrier pipelines and private pipelines contributed to MPLX, excluding equity method investments. (m) Includes the results of the terminal assets contributed to MPLX from the date the assets became a business, April 1, 2016. (n) Includes the results of the MarkWest assets beginning on the Dec. 4, 2015 acquisition date. Includes amounts related to unconsolidated equity method investments on a 100 percent basis.

Summary Of Principal Accounti40

Summary Of Principal Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Principles applied in consolidation	Principles applied in consolidation – These consolidated financial statements include the accounts of our majority-owned, controlled subsidiaries and MPLX. Changes in ownership interest in consolidated subsidiaries that do not result in a change in control are recorded as an equity transaction. As of December 31, 2017 , we owned a 30.4 percent interest in MPLX, including a two percent general partner interest. Due to our 100 percent ownership of the general partner interest, we have determined that we control MPLX and therefore we consolidate MPLX and record a noncontrolling interest for the 69.6 percent interest owned by the public. Investments in entities over which we have significant influence, but not control, are accounted for using the equity method of accounting. This includes entities in which we hold majority ownership but the minority shareholders have substantive participating rights. Income from equity method investments represents our proportionate share of net income generated by the equity method investees. Differences in the basis of the investments and the separate net asset values of the investees, if any, are amortized into net income over the remaining useful lives of the underlying assets and liabilities, except for the excess related to goodwill. Equity method investments are evaluated for impairment whenever changes in the facts and circumstances indicate an other than temporary loss in value has occurred. When the loss is deemed to be other than temporary, the carrying value of the equity method investment is written down to fair value.
Use of estimates	Use of estimates – The preparation of financial statements in accordance with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities as of the date of the consolidated financial statements and the reported amounts of revenues and expenses during the respective reporting periods.
Revenue recognition	Revenue recognition – Revenues are recognized when products are shipped or services are provided to customers, title is transferred, the sales price is fixed or determinable and collectability is reasonably assured. Costs associated with revenues are recorded in cost of revenues. Shipping and other transportation costs billed to our customers are presented on a gross basis in revenues and cost of revenues. Rebates from vendors are recognized as a reduction of cost of revenues when the initiating transaction occurs. Incentives that are derived from contractual provisions are accrued based on past experience and recognized in cost of revenues. Rebates to customers are reflected as a reduction of revenue and are accrued for in “Accounts payable” on the consolidated balance sheets.
Crude oil and refined product exchanges and matching buy/sell transactions	Crude oil and refined product exchanges and matching buy/sell transactions – We enter into exchange contracts and matching buy/sell arrangements whereby we agree to deliver a particular quantity and quality of crude oil or refined products at a specified location and date to a particular counterparty and to receive from the same counterparty the same commodity at a specified location on the same or another specified date. The exchange receipts and deliveries are nonmonetary transactions, with the exception of associated grade or location differentials that are settled in cash. The matching buy/sell purchase and sale transactions are settled in cash. Both exchange and matching buy/sell transactions are accounted for as exchanges of inventory and no revenues are recorded. The exchange transactions are recognized at the carrying amount of the inventory transferred.
Consumer excise taxes	Consumer excise taxes – We are required by various governmental authorities, including countries, states and municipalities, to collect and remit taxes on certain consumer products. Such taxes are presented on a gross basis in revenues and costs and expenses in the consolidated statements of income.
Cash and cash equivalents	Cash and cash equivalents – Cash and cash equivalents include cash on hand and on deposit and investments in highly liquid debt instruments with maturities of three months or less.
Restricted cash	Restricted cash – Restricted cash consists of cash and investments that must be maintained as collateral for letters of credit issued to certain third party producer customers. The balances will be outstanding until certain capital projects are completed and the third party releases the restriction. Restricted cash also consists of cash advances to be used for the operation and maintenance of an operated pipeline system. At December 31, 2017 and 2016 , the amount of restricted cash included in “Other current assets” on the consolidated balance sheets were $4 million and $5 million , respectively, which is currently reflected in our Midstream segment
Accounts receivable and allowance for doubtful accounts	Accounts receivable and allowance for doubtful accounts – Our receivables primarily consist of customer accounts receivable. Customer receivables are recorded at the invoiced amounts and generally do not bear interest. Allowances for doubtful accounts are generally recorded when it becomes probable the receivable will not be collected and are booked to bad debt expense. The allowance for doubtful accounts is the best estimate of the amount of probable credit losses in customer accounts receivable. We review the allowance quarterly and past-due balances over 180 days are reviewed individually for collectability. Approximately 23 percent of our accounts receivable balances at both December 31, 2017 and 2016 are related to sales of crude oil or refinery feedstocks to customers with whom we have master netting agreements. We have master netting agreements with more than 100 companies engaged in the crude oil or refinery feedstock trading and supply business or the petroleum refining industry. A master netting agreement generally provides for a once per month net cash settlement of the accounts receivable from and the accounts payable to a particular counterparty.
Inventories	Inventories – Inventories are carried at the lower of cost or market value. Cost of inventories is determined primarily under the LIFO method. Costs for crude oil, refinery feedstocks and refined product inventories are aggregated on a consolidated basis for purposes of assessing if the LIFO cost basis of these inventories may have to be written down to market value.
Derivative instruments	Derivative instruments – We use derivatives to economically hedge a portion of our exposure to commodity price risk and, historically, to interest rate risk. We also have limited authority to use selective derivative instruments that assume market risk. All derivative instruments (including derivative instruments embedded in other contracts) are recorded at fair value. Certain commodity derivatives are reflected on the consolidated balance sheets on a net basis by counterparty as they are governed by master netting agreements. Cash flows related to derivatives used to hedge commodity price risk and interest rate risk are classified in operating activities with the underlying transactions. Derivatives not designated as accounting hedges – Derivatives that are not designated as accounting hedges may include commodity derivatives used to hedge price risk on (1) inventories, (2) fixed price sales of refined products, (3) the acquisition of foreign-sourced crude oil, (4) the acquisition of ethanol for blending with refined products, (5) the sale of NGLs and (6) the purchase of natural gas. Changes in the fair value of derivatives not designated as accounting hedges are recognized immediately in net income. Concentrations of credit risk – All of our financial instruments, including derivatives, involve elements of credit and market risk. The most significant portion of our credit risk relates to nonperformance by counterparties. The counterparties to our financial instruments consist primarily of major financial institutions and companies within the energy industry. To manage counterparty risk associated with financial instruments, we select and monitor counterparties based on an assessment of their financial strength and on credit ratings, if available. Additionally, we limit the level of exposure with any single counterparty.
Property, plant and equipment	Property, plant and equipment – Property, plant and equipment are recorded at cost and depreciated on a straight-line basis over the estimated useful lives of the assets, which range from three to 49 years. Such assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. If the sum of the expected undiscounted future cash flows from the use of the asset and its eventual disposition is less than the carrying amount of the asset, an impairment assessment is performed and the excess of the book value over the fair value of the asset is recorded as an impairment loss. When items of property, plant and equipment are sold or otherwise disposed of, any gains or losses are reported in net income. Gains on the disposal of property, plant and equipment are recognized when earned, which is generally at the time of closing. If a loss on disposal is expected, such losses are recognized when the assets are classified as held for sale. Interest expense is capitalized for qualifying assets under construction. Capitalized interest costs are included in property, plant and equipment and are depreciated over the useful life of the related asset.
Goodwill and intangible assets	Goodwill and intangible assets – Goodwill represents the excess of the purchase price over the estimated fair value of the net assets acquired in the acquisition of a business. Goodwill is not amortized, but rather is tested for impairment annually and when events or changes in circumstances indicate that the fair value of a reporting unit with goodwill has been reduced below carrying value. The impairment test requires allocating goodwill and other assets and liabilities to reporting units. The fair value of each reporting unit is determined and compared to the carrying value of the reporting unit. If the fair value of the reporting unit is less than the carrying value, including goodwill, the implied fair value of goodwill is calculated. The excess, if any, of the book value over the implied fair value of goodwill is charged to net income as an impairment expense. Amortization of intangibles with definite lives is calculated using the straight-line method which is reflective of the benefit pattern in which the estimated economic benefit is expected to be received over the estimated useful life of the intangible asset. Intangibles subject to amortization are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the intangible may not be recoverable. If the sum of the expected undiscounted future cash flows related to the asset is less than the carrying amount of the asset, an impairment loss is recognized based on the fair value of the asset. Intangibles not subject to amortization are tested for impairment annually and when circumstances indicate that the fair value is less than the carrying amount of the intangible. If the fair value is less than the carrying value, an impairment is recorded for the difference.
Major maintenance activities	Major maintenance activities – Costs for planned turnaround, major maintenance and engineered project activities are expensed in the period incurred. These types of costs include contractor repair services, materials and supplies, equipment rentals and our labor costs.
Environmental costs	Environmental costs – Environmental expenditures are capitalized for additional equipment that mitigates or prevents future contamination or improves environmental safety or efficiency of the existing assets. We recognize remediation costs and penalties when the responsibility to remediate is probable and the amount of associated costs can be reasonably estimated. The timing of remediation accruals coincides with completion of a feasibility study or the commitment to a formal plan of action. Remediation liabilities are accrued based on estimates of known environmental exposure and are discounted when the estimated amounts are reasonably fixed and determinable. If recoveries of remediation costs from third parties are probable, a receivable is recorded and is discounted when the estimated amount is reasonably fixed and determinable.
Asset retirement obligations	Asset retirement obligations – The fair value of asset retirement obligations is recognized in the period in which the obligations are incurred if a reasonable estimate of fair value can be made. The majority of our recognized asset retirement liability relates to conditional asset retirement obligations for removal and disposal of fire-retardant material from certain refining facilities. The remaining recognized asset retirement liability relates to other refining assets, the removal of underground storage tanks at our leased convenience stores, certain pipelines and processing facilities and other related pipeline assets. The fair values recorded for such obligations are based on the most probable current cost projections. The recorded asset retirement obligations are not material to the consolidated financial statements. Asset retirement obligations have not been recognized for some assets because the fair value cannot be reasonably estimated since the settlement dates of the obligations are indeterminate. Such obligations will be recognized in the period when sufficient information becomes available to estimate a range of potential settlement dates. The asset retirement obligations principally include the hazardous material disposal and removal or dismantlement requirements associated with the closure of certain refining, terminal, retail, pipeline and processing assets. Our practice is to keep our assets in good operating condition through routine repair and maintenance of component parts in the ordinary course of business and by continuing to make improvements based on technological advances. As a result, we believe that generally these assets have no expected settlement date for purposes of estimating asset retirement obligations since the dates or ranges of dates upon which we would retire these assets cannot be reasonably estimated at this time.
Income taxes	Income taxes – Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between the financial statement carrying amounts of assets and liabilities and their tax bases. Deferred tax assets are recorded when it is more likely than not that they will be realized. The realization of deferred tax assets is assessed periodically based on several factors, primarily our expectation to generate sufficient future taxable income.
Stock-based compensation arrangements	Stock-based compensation arrangements – The fair value of stock options granted to our employees is estimated on the date of grant using the Black-Scholes option pricing model. The model employs various assumptions, based on management’s estimates at the time of grant, which impact the calculation of fair value and ultimately, the amount of expense that is recognized over the vesting period of the stock option award. Of the required assumptions, the expected life of the stock option award and the expected volatility of our stock price have the most significant impact on the fair value calculation. The average expected life is based on our historical employee exercise behavior. The assumption for expected volatility of our stock price reflects a weighting of 50 percent of our common stock implied volatility and 50 percent of our common stock historical volatility. The fair value of restricted stock awards granted to our employees is determined based on the fair market value of our common stock on the date of grant. The fair value of performance unit awards granted to our employees is estimated on the date of grant using a Monte Carlo valuation model. Our stock-based compensation expense is recognized based on management’s estimate of the awards that are expected to vest, using the straight-line attribution method for all service-based awards with a graded vesting feature. If actual forfeiture results are different than expected, adjustments to recognized compensation expense may be required in future periods. Unearned stock-based compensation is charged to equity when restricted stock awards are granted. Compensation expense is recognized over the vesting period and is adjusted if conditions of the restricted stock award are not met.
Business combinations	Business combinations - We recognize and measure the assets acquired and liabilities assumed in a business combination based on their estimated fair values at the acquisition date, with any remaining difference versus the purchase consideration recorded as goodwill or gain from a bargain purchase. For all material acquisitions, management engages an independent valuation specialist to assist with the determination of fair value of the assets acquired, liabilities assumed, noncontrolling interest, if any, and goodwill, based on recognized business valuation methodologies. If the initial accounting for the business combination is incomplete by the end of the reporting period in which the acquisition occurs, an estimate will be recorded. Subsequent to the acquisition, and not later than one year from the acquisition date, we will record any material adjustments to the initial estimate based on new information obtained about facts and circumstances that existed as of the acquisition date. An income, market or cost valuation method may be utilized to estimate the fair value of the assets acquired, liabilities assumed, and noncontrolling interest, if any, in a business combination. The income valuation method represents the present value of future cash flows over the life of the asset using: (i) discrete financial forecasts, which rely on management’s estimates of revenue and operating expenses; (ii) long-term growth rates; and (iii) appropriate discount rates. The market valuation method uses prices paid for a reasonably similar asset by other purchasers in the market, with adjustments relating to any differences between the assets. The cost valuation method is based on the replacement cost of a comparable asset at prices at the time of the acquisition reduced for depreciation of the asset. Acquisition-related costs are expensed as incurred in connection with each business combination.
Renewable fuel identification numbers (RINs)	Renewable fuel identification numbers – We purchase RINs to satisfy a portion of our RFS2 compliance. We record a short-term intangible asset, included in “Other current assets” on the balance sheet, for RINs owned in excess of our anticipated current period compliance requirements. The asset value is based on the product of the excess RINs as of the balance sheet date, if any, and the weighted average cost of our RINs. We record a current liability, included in “Other current liabilities” on the balance sheet, when we are deficient RINs based on the product of the deficient RINs as of the balance sheet date, if any, and the market price of the RINs at the balance sheet date. The cost of RINs used for compliance is reflected in “Cost of revenues” on the income statement. Any gains or losses on the sale or expiration of RINs are classified as “Other income” on the income statement. Proceeds from RIN sales are included in investing activities - “All other, net” on the cash flow statement.

MPLX LP (Tables)

MPLX LP (Tables)	12 Months Ended
	Dec. 31, 2017
Noncontrolling Interest [Abstract]
Noncontrolling Interest	As a result of equity transactions of MPLX, we are required to adjust non-controlling interest and additional paid-in capital. Changes in MPC’s equity resulting from changes in its ownership interest in MPLX were as follows: (In millions) 2017 2016 2015 Transfers (to) from noncontrolling interest Changes due to the issuance of MPLX LP common units to the public $ 25 $ (60 ) $ 1,532 Changes due to the issuance of MPLX LP common units and general partner units to MPC 114 121 — Net transfers (to) from noncontrolling interests 139 61 1,532 Tax impact (29 ) (118 ) (404 ) Increase (decrease) in MPC's additional paid-in capital, net of tax $ 110 $ (57 ) 1,128

Acquisitions and Investments (T

Acquisitions and Investments (Tables)	12 Months Ended
	Dec. 31, 2017
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Information	The following unaudited pro forma financial information presents consolidated results assuming the MarkWest Merger occurred on January 1, 2014. (In millions, except per share data) 2015 Sales and other operating revenues (including consumer excise taxes) $ 73,760 Net income attributable to MPC 2,825 Net income attributable to MPC per share – basic $ 5.25 Net income attributable to MPC per share – diluted 5.21
Ozark Pipeline
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Information	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: (In millions) 2017 Sales and other operating revenues (including consumer excise taxes) $ 38 Income from operations 20
MarkWest
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Information	The amounts of revenue and income from operations associated with the MarkWest Merger included in our consolidated statements of income for 2015 are as follows: (In millions) 2015 Sales and other operating revenues (including consumer excise taxes) $ 120 Income from operations 32
Components Of The Fair Value Of Consideration Transferred	The components of the fair value of consideration transferred are as follows: (In millions) Fair value of MPLX units issued $ 7,326 Cash payment to MarkWest unitholders 1,230 Payable to MarkWest Class B unitholders 50 Total fair value of consideration transferred $ 8,606

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Sales to Related Parties	Sales to related parties were as follows: (In millions) 2017 2016 2015 PFJ Southeast $ 619 $ 56 $ — Other equity method investees 10 6 6 Total $ 629 $ 62 $ 6
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: (In millions) 2017 2016 2015 MarkWest Utica EMG $ 17 $ 16 $ — Ohio Gathering 16 15 2 Sherwood Midstream 8 — — Other equity method investees 11 10 2 Total $ 52 $ 41 $ 4
Purchases From Related Parties	Purchases from related parties were as follows: (In millions) 2017 2016 2015 Crowley Blue Water Partners $ 60 $ 37 $ — Crowley Ocean Partners 79 52 6 Illinois Extension Pipeline 100 110 4 LOCAP 22 23 23 LOOP 71 59 52 TAAE 72 41 52 TACE 44 59 54 TAME 76 93 87 Other equity method investees 46 35 30 Total $ 570 $ 509 $ 308
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: December 31, (In millions) 2017 2016 PFJ Southeast $ 28 $ 40 Other equity method investees 8 5 Total $ 36 $ 45
Payables To Related Parties	Payables to related parties, which are included in “Accounts payable” on the accompanying consolidated balance sheets, were as follows: December 31, (In millions) 2017 2016 Illinois Extension Pipeline $ 8 $ 9 LOOP 3 6 MarkWest Utica EMG 29 24 Ohio Gathering 9 — Sherwood Midstream 8 — Other equity method investees 12 14 Total $ 69 $ 53

Income per Common Share (Tables

Income per Common Share (Tables)	12 Months Ended
	Dec. 31, 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. (In millions, except per share data) 2017 2016 2015 Basic earnings per share: Allocation of earnings: Net income attributable to MPC $ 3,432 $ 1,174 $ 2,852 Income allocated to participating securities 2 1 4 Income available to common stockholders – basic $ 3,430 $ 1,173 $ 2,848 Weighted average common shares outstanding 507 528 538 Basic earnings per share $ 6.76 $ 2.22 $ 5.29 Diluted earnings per share: Allocation of earnings: Net income attributable to MPC $ 3,432 $ 1,174 $ 2,852 Income allocated to participating securities 2 1 4 Income available to common stockholders – diluted $ 3,430 $ 1,173 $ 2,848 Weighted average common shares outstanding 507 528 538 Effect of dilutive securities 5 2 4 Weighted average common shares, including dilutive effect 512 530 542 Diluted earnings per share $ 6.70 $ 2.21 $ 5.26
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following table summarizes the shares that were anti-dilutive, and therefore, were excluded from the diluted share calculation. (In millions) 2017 2016 2015 Shares issued under stock-based compensation plans 1 3 1

Equity (Tables)

Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Share Repurchases	Total share repurchases were as follows for the respective periods: (In millions, except per share data) 2017 2016 2015 Number of shares repurchased 44 4 19 Cash paid for shares repurchased $ 2,372 $ 197 $ 965 Average cost per share $ 53.85 $ 41.84 $ 50.31

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Income From Operations Attributable To Operating Segments	(In millions) Refining & Marketing Speedway Midstream Total Year Ended December 31, 2017 Revenues: Third party $ 52,761 $ 19,021 $ 2,322 $ 74,104 Intersegment (a) 11,309 4 1,443 12,756 Related party 621 8 — 629 Segment revenues $ 64,691 $ 19,033 $ 3,765 $ 87,489 Segment income from operations $ 2,321 $ 732 $ 1,339 $ 4,392 Income from equity method investments (b) 17 69 197 283 Depreciation and amortization (b) 1,082 275 699 2,056 Capital expenditures and investments (c)(d) 832 381 2,505 3,718 (In millions) Refining & Marketing Speedway Midstream Total Year Ended December 31, 2016 Revenues: Third party $ 43,167 $ 18,282 $ 1,828 $ 63,277 Intersegment (a) 10,589 3 1,262 11,854 Related party 61 1 — 62 Segment revenues $ 53,817 $ 18,286 $ 3,090 $ 75,193 Segment income from operations (e) $ 1,357 $ 734 $ 1,048 $ 3,139 Income from equity method investments (b) 24 5 142 171 Depreciation and amortization (b) 1,063 273 605 1,941 Capital expenditures and investments (c) 1,054 303 1,568 2,925 (In millions) Refining & Marketing Speedway Midstream Total Year Ended December 31, 2015 Revenues: Third party $ 52,168 $ 19,690 $ 187 $ 72,045 Intersegment (a) 12,024 3 930 12,957 Related party 6 — — 6 Segment revenues $ 64,198 $ 19,693 $ 1,117 $ 85,008 Segment income from operations (e)(f) $ 3,997 $ 673 $ 463 $ 5,133 Income from equity method investments 26 — 62 88 Depreciation and amortization (b) 1,052 254 144 1,450 Capital expenditures and investments (c)(g) 1,045 501 14,545 16,091 (a) Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties. (b) Differences between segment totals and MPC totals represent amounts related to unallocated items and are included in “Items not allocated to segments” in the reconciliation below. (c) Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates. (d) In 2017, 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. See Note 5 . (e) In 2016, the Refining & Marketing and Speedway segments include an inventory LCM benefit of $345 million and $25 million , respectively. In 2015, the Refining & Marketing and Speedway segments include an inventory LCM charge of $345 million and $25 million , respectively. (f) Included in the Midstream segment for 2015 are $36 million of transaction costs related to the MarkWest Merger. (g) The Midstream segment includes $13.85 billion for the MarkWest Merger.
Reconciliation Of Segment Income From Operations To Income Before Income Taxes	The following reconciles segment income from operations to income before income taxes as reported in the consolidated statements of income: (In millions) 2017 2016 2015 Segment income from operations $ 4,392 $ 3,139 $ 5,133 Items not allocated to segments: Corporate and other unallocated items (a) (365 ) (268 ) (293 ) Pension settlement expenses (b) (52 ) (7 ) (4 ) Litigation (29 ) — — Impairments (c) 23 (486 ) (144 ) Net interest and other financial income (costs) (625 ) (556 ) (318 ) Income before income taxes $ 3,344 $ 1,822 $ 4,374 (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 22 for further information. (c) 2017 includes MPC’s share of gains related to the sale of assets remaining from the Sandpiper pipeline project. 2016 includes impairments of goodwill and equity method investments. 2015 relates to the cancellation of the ROUX project at our Garyville refinery. See Notes 16 and 17 .
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures	The following reconciles segment capital expenditures and investments to total capital expenditures: (In millions) 2017 2016 2015 Segment capital expenditures and investments $ 3,718 $ 2,925 $ 16,091 Less investments in equity method investees (a) 805 431 2,788 Plus items not allocated to segments: Corporate and Other 83 81 155 Capitalized interest 55 63 37 Total capital expenditures (b) $ 3,051 $ 2,638 $ 13,495 (a) 2017 includes an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system. 2016 includes an adjustment of $143 million to the fair value of equity method investments acquired in connection with the MarkWest Merger. 2015 includes $2.46 billion related to the MarkWest Merger. See Note 5 . (b) Capital expenditures include changes in capital accruals. See Note 20 for a reconciliation of total capital expenditures to additions to property, plant and equipment as reported in the consolidated statements of cash flows.
Schedule Of Revenues By Product Line	Revenues by product line were: (In millions) 2017 2016 2015 Refined products $ 63,846 $ 54,450 $ 63,738 Merchandise 5,174 5,297 5,188 Crude oil and refinery feedstocks 3,403 2,038 2,718 Service, transportation and other 1,681 1,492 401 Sales and other operating revenues (including consumer excise taxes) $ 74,104 $ 63,277 $ 72,045
Total Assets by Reportable Segment	Total assets by reportable segment were: December 31, (In millions) 2017 2016 Refining & Marketing $ 17,537 $ 17,601 Speedway 5,563 5,426 Midstream 19,937 18,516 Corporate and Other 6,010 2,870 Total consolidated assets $ 49,047 $ 44,413

Other Items (Tables)

Other Items (Tables)	12 Months Ended
	Dec. 31, 2017
Other Income and Expenses [Abstract]
Net Interest And Other Financial Income (Costs)	Net interest and other financial income (costs) was: (In millions) 2017 2016 2015 Interest income $ 27 $ 6 $ 6 Interest expense (a) (688 ) (602 ) (325 ) Interest capitalized 63 64 37 Loss on extinguishment of debt — — (5 ) Other financial costs (b) (27 ) (24 ) (31 ) Net interest and other financial income (costs) $ (625 ) $ (556 ) $ (318 ) (a) Includes $46 million , $44 million and $1 million for 2017 , 2016 and 2015 , respectively, for the amortization of the discount related to the difference between the fair value and the principal amount of assumed MarkWest debt. (b) 2015 includes $6 million of transaction costs related to the MarkWest Merger.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Components Of Income Tax Provisions (Benefits)	Income tax provisions (benefits) were: 2017 2016 2015 (In millions) Current Deferred Total Current Deferred Total Current Deferred Total Federal $ 681 $ (1,270 ) $ (589 ) $ 189 $ 336 $ 525 $ 1,210 $ 134 $ 1,344 State and local 98 33 131 27 57 84 152 9 161 Foreign (6 ) 4 (2 ) (1 ) 1 — 10 (9 ) 1 Total $ 773 $ (1,233 ) $ (460 ) $ 215 $ 394 $ 609 $ 1,372 $ 134 $ 1,506
Reconciliation Of Federal Statutory Income Tax Rate	A reconciliation of the federal statutory income tax rate ( 35 percent ) applied to income before income taxes to the provision for income taxes follows: 2017 2016 2015 Statutory rate applied to income before income taxes 35 % 35 % 35 % State and local income taxes, net of federal income tax effects 2 3 2 Domestic manufacturing deduction (1 ) (1 ) (2 ) Noncontrolling interests (4 ) (1 ) — Biodiesel excise tax credit — (1 ) (1 ) TCJA legislation (45 ) — — Other (1 ) (2 ) — Provision for income taxes (14 )% 33 % 34 %
Components Of Deferred Tax Assets And Liabilities	Deferred tax assets and liabilities resulted from the following: December 31, (In millions) 2017 2016 Deferred tax assets: Employee benefits $ 348 $ 578 Environmental 16 34 Deferred revenue 21 31 Net operating loss carryforwards 12 23 Other 23 27 Total deferred tax assets 420 693 Deferred tax liabilities: Property, plant and equipment 1,603 2,591 Inventories 473 707 Investments in subsidiaries and affiliates 912 1,145 Other 73 94 Total deferred tax liabilities 3,061 4,537 Net deferred tax liabilities $ 2,641 $ 3,844
Components Of Net Deferred Tax Liabilities Classified In Consolidated Balance Sheets	Net deferred tax liabilities were classified in the consolidated balance sheets as follows: December 31, (In millions) 2017 2016 Assets: Other noncurrent assets $ 13 $ 17 Liabilities: Deferred income taxes 2,654 3,861 Net deferred tax liabilities $ 2,641 $ 3,844
Summary Of Income Tax Returns Subject To Examination	As of December 31, 2017 , our income tax returns remain subject to examination in the following major tax jurisdictions for the tax years indicated: United States Federal 2010 - 2016 States 2008 - 2016
Summary Of Activity In Unrecognized Tax Benefits	The following table summarizes the activity in unrecognized tax benefits: (In millions) 2017 2016 2015 January 1 balance $ 7 $ 12 $ 12 Additions for tax positions of prior years 13 6 — Reductions for tax positions of prior years — (10 ) — Settlements (1 ) (1 ) — December 31 balance $ 19 $ 7 $ 12

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2017
Inventory Disclosure [Abstract]
Summary Of Inventories	December 31, (In millions) 2017 2016 Crude oil and refinery feedstocks $ 2,056 $ 2,208 Refined products 2,839 2,810 Materials and supplies 494 485 Merchandise 161 153 Total $ 5,550 $ 5,656

Equity Method Investments (Tabl

Equity Method Investments (Tables)	12 Months Ended
	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Schedule Of Equity Method Investments	Ownership as of Carrying value at December 31, December 31, (In millions) 2017 2017 2016 Centennial 50% $ 35 $ 35 Centrahoma Processing LLC (a) 40% 121 104 Crowley Coastal Partners 50% 188 184 Explorer (a) 25% 89 94 Illinois Extension Pipeline (a) 35% 284 293 LOOP (b) 51% 282 277 MarEn Bakken Company LLC (a) 25% 520 — MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C. (a) 67% 164 67 MarkWest Utica EMG (a) 56% 2,139 2,224 PFJ Southeast 29% 328 283 Sherwood Midstream (a) 50% 236 — Sherwood Midstream Holdings LLC (a)(c) 69% 165 — TAAE 45% 39 33 TACE 61% 32 33 TAEI (d) —% — 15 TAME (d) 67% 33 18 Other MPLX investments (a) 67 76 Other 65 91 Total $ 4,787 $ 3,827 (a) Ownership interest held by MPLX as of December 31, 2017 . (b) MPLX held a 41 percent ownership interest as of December 31, 2017 . (c) Excludes Sherwood Midstream LLC’s investment in Sherwood Midstream Holdings LLC. (d) On January 1, 2017, we contributed our 34 percent interest in TAEI to TAME in exchange for a 17 percent in TAME.
Summarized Financial Information For Equity Method Investees	Summarized financial information for equity method investees is as follows: (In millions) 2017 2016 2015 Income statement data: Revenues and other income $ 6,235 $ 2,421 $ 1,390 Income (loss) from operations 1,075 (116 ) 332 Net income (loss) 922 (250 ) 239 Balance sheet data – December 31: Current assets $ 860 $ 711 Noncurrent assets 10,854 8,170 Current liabilities 547 884 Noncurrent liabilities 1,714 1,462

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Summary Of Property, Plant And Equipment	(In millions) Estimated Useful Lives December 31, 2017 2016 (a) Refining & Marketing 4 - 30 years $ 19,490 $ 18,590 Speedway 4 - 25 years 5,358 5,078 Midstream 3 - 49 years 14,898 13,521 Corporate and Other 4 - 40 years 792 817 Total 40,538 38,006 Less accumulated depreciation 14,095 12,241 Property, plant and equipment, net $ 26,443 $ 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.

Goodwill and Intangibles (Table

Goodwill and Intangibles (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in Carrying Amount of Goodwill	The changes in the carrying amount of goodwill for 2016 and 2017 were as follows: (In millions) Refining & Marketing Speedway Midstream Total Balance at January 1, 2016 $ 539 $ 853 $ 2,627 $ 4,019 Purchase price allocation adjustments — — (241 ) (241 ) Disposition (a) — (61 ) — (61 ) Impairment — — (130 ) (130 ) Transfer of assets related to dropdowns (b) (20 ) — 20 — Balance at December 31, 2016 $ 519 $ 792 $ 2,276 $ 3,587 Disposition (a) — (1 ) — (1 ) Balance at December 31, 2017 $ 519 $ 791 $ 2,276 $ 3,586 (a) Goodwill associated with our former Speedway travel plaza locations that are now part of the PFJ Southeast joint venture. The amount was included in the initial basis for our equity method investment in the joint venture.
Schedule of Acquired Finite-Lived Intangible Assets by Major Class	Our intangible assets as of December 31, 2017 and 2016 are as follows: (In millions) Refining & Marketing Speedway Midstream Total Balance at December 31, 2017 Customer contracts and relationships $ 120 $ 1 $ 533 $ 654 Royalty agreements 129 — — 129 Favorable lease contract terms — 56 — 56 Other (a) 73 75 — 148 Gross $ 322 $ 132 $ 533 $ 987 Accumulated amortization (143 ) (39 ) (79 ) (261 ) Net $ 179 $ 93 $ 454 $ 726 Balance at December 31, 2016 Customer contracts and relationships $ 102 $ 1 $ 533 $ 636 Royalty agreements 128 — — 128 Favorable lease contract terms 1 57 — 58 Other (a) 27 75 — 102 Gross $ 258 $ 133 $ 533 $ 924 Accumulated amortization (123 ) (35 ) (41 ) (199 ) Net $ 135 $ 98 $ 492 $ 725 (a) The Refining & Marketing and Speedway segments include unamortized intangible assets of $48 million and $46 million , respectively, which are primarily emission allowance credits and trademarks.
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	Estimated future amortization expense related to the intangible assets at December 31, 2017 is as follows: (In millions) 2018 $ 52 2019 52 2020 50 2021 49 2022 48

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 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 December 31, 2017 and 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. December 31, 2017 Fair Value Hierarchy (In millions) Level 1 Level 2 Level 3 Netting and Collateral (a) Net Carrying Value on Balance Sheet (b) Collateral Pledged Not Offset Commodity derivative instruments, assets $ 127 $ — $ — $ (118 ) $ 9 $ 8 Other assets 3 — — N/A 3 — Total assets at fair value $ 130 $ — $ — $ (118 ) $ 12 $ 8 Commodity derivative instruments, liabilities $ 126 $ — $ 2 $ (126 ) $ 2 $ — Embedded derivatives in commodity contracts (c) — — 64 — 64 — Total liabilities at fair value $ 126 $ — $ 66 $ (126 ) $ 66 $ — 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 December 31, 2017 , cash collateral of $8 million was netted with mark-to-market derivative liabilities. As of December 31, 2016 , cash collateral of $24 million was netted with mark-to-market derivative liabilities. (b) We have no derivative contracts which are subject to master netting arrangements reflected gross on the balance sheet. (c) Includes $12 million and $13 million classified as current as of December 31, 2017 and 2016 , respectively. (d) Includes $130 million classified as current as of 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 net beginning and ending balances recorded for net assets and liabilities classified as Level 3 in the fair value hierarchy. (In millions) 2017 2016 2015 Beginning balance $ 190 $ 342 $ 478 Contingent consideration payment (a) (131 ) (200 ) (189 ) Net derivative positions assumed - MarkWest Merger — — 31 Unrealized and realized losses included in net income 25 55 20 Settlements of derivative instruments (18 ) (7 ) 2 Ending balance $ 66 $ 190 $ 342 The amount of total (gains) losses for the period included in earnings attributable to the change in unrealized (gains) losses relating to assets still held at the end of period: Derivative instruments $ 8 $ 32 $ (7 ) Contingent consideration agreement 1 13 28 Total $ 9 $ 45 $ 21 (a) On the consolidated statements of cash flows for 2017, 2016, and 2015, $89 million , $164 million and $175 million , respectively, of the contingent earnout payment to BP was included as a financing activity with the remainder included as an operating activity.
Assets Measured at Fair Value on a Nonrecurring Basis	The following table shows the values of assets, by major category, measured at fair value on a nonrecurring basis in periods subsequent to their initial recognition. Year Ended December 31, 2017 2016 2015 (In millions) Fair Value Impairment Fair Value Impairment Fair Value Impairment Equity method investments $ — $ — $ 42 $ 356 $ — $ — Goodwill — — — 130 — — Property, plant and equipment, net — — — — — 144
Financial Instruments at Fair Value, Excluding Derivative Financial Instruments and Contingent Consideration	The following table summarizes financial instruments on the basis of their nature, characteristics and risk at December 31, 2017 and 2016 , excluding the derivative financial instruments and contingent consideration reported above. December 31, 2017 2016 (In millions) Fair Value Carrying Value Fair Value Carrying Value Financial assets: Investments $ 29 $ 2 $ 25 $ 2 Other 17 17 21 21 Total financial assets $ 46 $ 19 $ 46 $ 23 Financial liabilities: Long-term debt (a) $ 13,893 $ 12,642 $ 10,892 $ 10,297 Deferred credits and other liabilities 122 109 121 109 Total financial liabilities $ 14,015 $ 12,751 $ 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)	12 Months Ended
	Dec. 31, 2017
Summary of Derivative Instruments [Abstract]
Classification of Fair Values of Derivative Instruments, Excluding Cash Collateral	The following table presents the gross fair values of derivative instruments, excluding cash collateral, and where they appear on the consolidated balance sheets as of December 31, 2017 and 2016 : (In millions) December 31, 2017 Balance Sheet Location Asset Liability Commodity derivatives Other current assets $ 127 $ 126 Other current liabilities (a) — 14 Deferred credits and other liabilities (a) — 52 (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 table below summarizes open commodity derivative contracts for crude oil and refined products as of December 31, 2017 . Position Total Barrels (In thousands) Crude Oil (a) Exchange-traded Long 23,299 Exchange-traded Short (25,199 ) (a ) 99.8 percent of the exchange-traded contracts expire in the first quarter of 2018 . Position Total Gallons (In thousands) Refined Products (a) Exchange-traded Long 257,460 Exchange-traded Short (236,460 ) OTC Short (9,587 ) (a ) 100 percent of the exchange-traded contracts expire in the first quarter of 2018 .
Effect of Commodity Derivative Instruments in Statements of Income	The following table summarizes the effect of all commodity derivative instruments in our consolidated statements of income: (In millions) Gain (Loss) Income Statement Location 2017 2016 2015 Sales and other operating revenues $ 5 $ (13 ) $ 19 Cost of revenues (26 ) (167 ) 294 Total $ (21 ) $ (180 ) $ 313

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Outstanding Borrowings	Our outstanding borrowings at December 31, 2017 and 2016 consisted of the following: December 31, (In millions) 2017 2016 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 Capital lease obligations due 2018-2033 356 311 MPLX LP: MPLX term loan facility due 2019 — 250 MPLX bank revolving credit facility due 2022 505 — 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 — MPLX capital lease obligations due 2020 7 8 Total 13,418 11,069 Unamortized debt issuance costs (59 ) (44 ) Unamortized discount (a) (413 ) (453 ) Amounts due within one year (624 ) (28 ) Total long-term debt due after one year $ 12,322 $ 10,544 (a) Includes $374 million and $420 million unamortized discount as of December 31, 2017 and December 31, 2016 , respectively, related to the difference at the time of the acquisition between the fair value and the principal amount of assumed MarkWest debt.
Schedule Of Debt Payments	The following table shows five years of scheduled debt payments. (In millions) 2018 $ 626 2019 27 2020 683 2021 1,031 2022 537

Supplemental Cash Flow Inform56

Supplemental Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2017
Supplemental Cash Flow Information [Abstract]
Summary of Supplemental Cash Flow Information	(In millions) 2017 2016 2015 Net cash provided by operating activities included: Interest paid (net of amounts capitalized) $ 525 $ 478 $ 272 Net income taxes paid to taxing authorities 904 140 1,605 Non-cash investing and financing activities: Capital lease obligations increase $ 71 $ — $ 1 Contribution of assets to joint venture (a) 337 273 — Intangible asset acquired (b) 45 — — Property, plant and equipment sold — — 5 Property, plant and equipment acquired — — 5 Acquisition: Fair value of MPLX units issued (c) — — 7,326 Payable to MPLX Class B unitholders — — 50 (a) 2017 includes MPLX’s contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. 2016 includes Speedway’s contribution of travel plaza locations to new joint venture with Pilot Flying J. See Note 5 . (b) See Note 16 for further information. (c) See Note 5
Schedule Of Reconciliation Of Additions To Property Plant And Equipment To Total Capital Expenditures	The consolidated statements of cash flows exclude changes to the consolidated balance sheets that did not affect cash. The following is a reconciliation of additions to property, plant and equipment to total capital expenditures: (In millions) 2017 2016 2015 Additions to property, plant and equipment per consolidated statements of cash flows $ 2,732 $ 2,892 $ 1,998 Non-cash additions to property, plant and equipment — — 5 Asset retirement expenditures (a) 2 6 1 Increase (decrease) in capital accruals 67 (127 ) 94 Total capital expenditures before acquisitions 2,801 2,771 2,098 Acquisitions (b) 250 (133 ) 11,397 Total capital expenditures $ 3,051 $ 2,638 $ 13,495 (a) Included in All other, net – Operating activities on the consolidated statements of cash flows. (b) 2017 reflects primarily the acquisition of the Ozark pipeline. 2016 includes adjustments to the fair values of property, plant and equipment, intangibles and goodwill acquired in connection with the MarkWest Merger. The 2015 acquisitions include the MarkWest Merger. The acquisition numbers above include property, plant and equipment, intangibles and goodwill.

Accumulated Other Comprehensi57

Accumulated Other Comprehensive Loss (Tables)	12 Months Ended
	Dec. 31, 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 22 64 — — 86 Amounts reclassified from accumulated other comprehensive loss: Amortization – prior service credit (a) (46 ) (3 ) — — (49 ) – actuarial loss (a) 38 2 — — 40 – settlement loss (a) 7 — — — 7 Other (b) — — — (1 ) (1 ) Tax effect 1 — — — 1 Other comprehensive income (loss) 22 63 — (1 ) 84 Balance as of December 31, 2016 $ (233 ) $ (7 ) $ 4 $ 2 $ (234 ) (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 before reclassifications 12 (38 ) 3 (23 ) Amounts reclassified from accumulated other comprehensive loss: Amortization – prior service credit (a) (39 ) (3 ) — — (42 ) – actuarial loss (a) 36 (2 ) — — 34 – settlement loss (a) 52 — — — 52 Other (b) — — — (2 ) (2 ) Tax effect (18 ) 2 — — (16 ) Other comprehensive income (loss) 43 (41 ) — 1 3 Balance as of December 31, 2017 $ (190 ) $ (48 ) $ 4 $ 3 $ (231 ) (a) These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 22 . (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 O58

Defined Benefit Pension and Other Postretirement Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Defined Benefit Plan [Abstract]
Summary Of Defined Benefit Plans With Accumulated Benefit Obligations In Excess Of Plan Assets	The following summarizes our defined benefit pension plans that have accumulated benefit obligations in excess of plan assets. December 31, (In millions) 2017 2016 Projected benefit obligations $ 2,164 $ 2,024 Accumulated benefit obligations 2,008 1,914 Fair value of plan assets 1,840 1,659
Summary Of Projected Benefit Obligations And Funded Status For Defined Benefit Pension And Other Postretirement Plans	The following summarizes the projected benefit obligations and funded status for our defined benefit pension and other postretirement plans: Pension Benefits Other Benefits (In millions) 2017 2016 2017 2016 Change in benefit obligations: Benefit obligations at January 1 $ 2,024 $ 1,997 $ 740 $ 800 Service cost 132 114 25 32 Interest cost 75 73 30 35 Actuarial (gain) loss 150 15 61 (101 ) Benefits paid (217 ) (175 ) (30 ) (26 ) Other — — — — Benefit obligations at December 31 2,164 2,024 826 740 Change in plan assets: Fair value of plan assets at January 1 1,659 1,570 — — Actual return on plan assets 270 145 — — Employer contributions 128 119 30 26 Benefits paid from plan assets (217 ) (175 ) (30 ) (26 ) Fair value of plan assets at December 31 1,840 1,659 — — Funded status of plans at December 31 $ (324 ) $ (365 ) $ (826 ) $ (740 ) Amounts recognized in the consolidated balance sheets: Current liabilities $ (18 ) $ (18 ) $ (33 ) $ (32 ) Noncurrent liabilities (306 ) (347 ) (793 ) (708 ) Accrued benefit cost $ (324 ) $ (365 ) $ (826 ) $ (740 ) Pretax amounts recognized in accumulated other comprehensive loss: (a) Net actuarial loss $ 537 $ 645 $ 80 $ 17 Prior service credit (238 ) (276 ) (3 ) (6 ) (a) Amounts exclude those related to LOOP and Explorer, equity method investees with defined benefit pension and postretirement plans for which net losses of $17 million and less than $1 million were recorded in accumulated other comprehensive loss in 2017 , reflecting our ownership share.
Components of Net Periodic Benefit Costs	Components of net periodic benefit cost and other comprehensive loss – The following summarizes the net periodic benefit costs and the amounts recognized as other comprehensive loss for our defined benefit pension and other postretirement plans. Pension Benefits Other Benefits (In millions) 2017 2016 2015 2017 2016 2015 Components of net periodic benefit cost: Service cost $ 132 $ 114 $ 101 $ 25 $ 32 $ 31 Interest cost 75 73 71 30 35 32 Expected return on plan assets (100 ) (98 ) (98 ) — — — Amortization – prior service credit (39 ) (46 ) (46 ) (3 ) (3 ) (4 ) – actuarial loss 36 38 51 (2 ) 2 8 – settlement loss 52 7 4 — — — Net periodic benefit cost (a) $ 156 $ 88 $ 83 $ 50 $ 66 $ 67 Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax): Actuarial (gain) loss $ (20 ) $ (33 ) $ 69 $ 61 $ (101 ) $ (63 ) Prior service cost (b) — — — — — 13 Amortization of actuarial loss (88 ) (45 ) (55 ) 2 (2 ) (8 ) Amortization of prior service cost 39 46 46 3 3 4 Other — — — — — — Total recognized in other comprehensive loss $ (69 ) $ (32 ) $ 60 $ 66 $ (100 ) $ (54 ) Total recognized in net periodic benefit cost and other comprehensive loss $ 87 $ 56 $ 143 $ 116 $ (34 ) $ 13 (a) Net periodic benefit cost reflects a calculated market-related value of plan assets which recognizes changes in fair value over three years. (b) Includes adjustments related to the MarkWest Merger in 2015.
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Loss (Pretax)	Components of net periodic benefit cost and other comprehensive loss – The following summarizes the net periodic benefit costs and the amounts recognized as other comprehensive loss for our defined benefit pension and other postretirement plans. Pension Benefits Other Benefits (In millions) 2017 2016 2015 2017 2016 2015 Components of net periodic benefit cost: Service cost $ 132 $ 114 $ 101 $ 25 $ 32 $ 31 Interest cost 75 73 71 30 35 32 Expected return on plan assets (100 ) (98 ) (98 ) — — — Amortization – prior service credit (39 ) (46 ) (46 ) (3 ) (3 ) (4 ) – actuarial loss 36 38 51 (2 ) 2 8 – settlement loss 52 7 4 — — — Net periodic benefit cost (a) $ 156 $ 88 $ 83 $ 50 $ 66 $ 67 Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax): Actuarial (gain) loss $ (20 ) $ (33 ) $ 69 $ 61 $ (101 ) $ (63 ) Prior service cost (b) — — — — — 13 Amortization of actuarial loss (88 ) (45 ) (55 ) 2 (2 ) (8 ) Amortization of prior service cost 39 46 46 3 3 4 Other — — — — — — Total recognized in other comprehensive loss $ (69 ) $ (32 ) $ 60 $ 66 $ (100 ) $ (54 ) Total recognized in net periodic benefit cost and other comprehensive loss $ 87 $ 56 $ 143 $ 116 $ (34 ) $ 13 (a) Net periodic benefit cost reflects a calculated market-related value of plan assets which recognizes changes in fair value over three years. (b) Includes adjustments related to the MarkWest Merger in 2015.
Plan Assumptions	Plan assumptions – The following summarizes the assumptions used to determine the benefit obligations at December 31, and net periodic benefit cost for the defined benefit pension and other postretirement plans for 2017 , 2016 and 2015 . Pension Benefits Other Benefits 2017 2016 2015 2017 2016 2015 Weighted-average assumptions used to determine benefit obligation: Discount rate 3.55 % 3.90 % 4.00 % 3.70 % 4.25 % 4.50 % Rate of compensation increase 5.00 % 5.00 % 3.70 % 5.00 % 5.00 % 3.70 % Weighted-average assumptions used to determine net periodic benefit cost: Discount rate 3.85 % 3.80 % 3.70 % 4.25 % 4.50 % 4.30 % Expected long-term return on plan assets 6.50 % 6.50 % 6.75 % — % — % — % Rate of compensation increase 5.00 % 5.00 % 3.70 % 5.00 % 5.00 % 3.70 %
Assumed Health Care Cost Trend Rates	The following summarizes the assumed health care cost trend rates. December 31, 2017 2016 2015 Health care cost trend rate assumed for the following year: Medical: Pre-65 6.75 % 7.00 % 7.50 % Prescription drugs 8.75 % 9.00 % 7.00 % Rate to which the cost trend rate is assumed to decline (the ultimate trend rate): Medical: Pre-65 4.50 % 4.50 % 5.00 % Prescription drugs 4.50 % 4.50 % 5.00 % Year that the rate reaches the ultimate trend rate: Medical: Pre-65 2026 2026 2021 Prescription drugs 2026 2026 2021
Effects Of One Percentage Point Change In Assumed Health Care Cost Trend Rates	A one percentage point change in assumed health care cost trend rates would have the following effects: 1-Percentage- 1-Percentage- (In millions) Point Increase Point Decrease Effect on total of service and interest cost components $ 5 $ (4 ) Effect on other postretirement benefit obligations 38 (33 )
Fair Values Of Defined Benefit Pension Plan Assets	The following tables present the fair values of our defined benefit pension plans’ assets, by level within the fair value hierarchy, as of December 31, 2017 and 2016 . December 31, 2017 (In millions) Level 1 Level 2 Level 3 Total Cash and cash equivalents $ — $ 14 $ — $ 14 Equity: Common stocks 36 — — 36 Mutual funds 227 — — 227 Pooled funds — 507 — 507 Fixed income: Corporate — 673 1 674 Government — 98 — 98 Pooled funds — 176 — 176 Private equity — — 51 51 Real estate — — 34 34 Other 2 2 19 23 Total investments, at fair value $ 265 $ 1,470 $ 105 $ 1,840 December 31, 2016 (In millions) Level 1 Level 2 Level 3 Total Cash and cash equivalents $ — $ 24 $ — $ 24 Equity: Common stocks 71 — — 71 Mutual funds 160 — — 160 Pooled funds — 451 — 451 Fixed income: Corporate — 570 — 570 Government — 90 — 90 Pooled funds — 173 — 173 Private equity — — 60 60 Real estate — — 39 39 Other 2 — 19 21 Total investments, at fair value $ 233 $ 1,308 $ 118 $ 1,659
Reconciliation Of Beginning And Ending Balances Of Plan Assets Classified As Level 3	The following is a reconciliation of the beginning and ending balances recorded for plan assets classified as Level 3 in the fair value hierarchy: 2017 (In millions) Private Equity Real Estate Other Total Beginning balance $ 60 $ 39 $ 19 $ 118 Actual return on plan assets: Realized 11 3 — 14 Unrealized (1 ) — 1 — Purchases 2 1 1 4 Sales (21 ) (9 ) (1 ) (31 ) Ending balance $ 51 $ 34 $ 20 $ 105 2016 (In millions) Private Equity Real Estate Other Total Beginning balance $ 62 $ 50 $ 19 $ 131 Actual return on plan assets: Realized 8 5 — 13 Unrealized 2 (3 ) — (1 ) Purchases 2 1 — 3 Sales (14 ) (14 ) — (28 ) Ending balance $ 60 $ 39 $ 19 $ 118
Estimated Future Benefit Payment	Estimated future benefit payments – The following gross benefit payments, which reflect expected future service, as appropriate, are expected to be paid in the years indicated. (In millions) Pension Benefits Other Benefits 2018 $ 176 $ 33 2019 183 36 2020 161 38 2021 161 41 2022 158 42 2023 through 2027 790 229
Multi Employer Pension Plan	Our participation in this plan for 2017 , 2016 and 2015 is outlined in the table below. The “EIN” column provides the Employee Identification Number for the plan. The most recent Pension Protection Act zone status available in 2017 and 2016 is for the plan’s year ended December 31, 2016 and December 31, 2015 , respectively. The zone status is based on information that we received from the plan and is certified by the plan’s actuary. Among other factors, plans in the red zone are generally less than 65 percent funded. The “FIP/RP Status Pending/Implemented” column indicates a financial improvement plan or a rehabilitation plan has been implemented. The last column lists the expiration date of the collective-bargaining agreement to which the plan is subject. There have been no significant changes that affect the comparability of 2017 , 2016 and 2015 contributions. Our portion of the contributions does not make up more than five percent of total contributions to the plan. Pension Protection Act Zone Status FIP/RP Status Pending/Implemented MPC Contributions In millions ) Surcharge Expiration Date of Collective – Bargaining Pension Fund EIN 2017 2016 2017 2016 2015 Central States, Southeast and Southwest Areas Pension Plan (a) 366044243 Red Red Implemented $ 4 $ 4 $ 4 No January 31, 2019 (a) This agreement has a minimum contribution requirement of $315 per week per employee for 2018 . A total of 282 employees participated in the plan as of December 31, 2017 .

Stock-Based Compensation Plans

Stock-Based Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award	The following table reflects activity related to our stock-based compensation arrangements: (In millions) 2017 2016 2015 Stock-based compensation expense $ 51 $ 45 $ 42 Tax benefit recognized on stock-based compensation expense 19 17 16 Cash received by MPC upon exercise of stock option awards 46 10 33 Tax benefit received for tax deductions for stock awards exercised 25 4 26
Weighted Average Assumptions Used To Value Stock Options Awards	The Black Scholes option-pricing model values used to value stock option awards granted were determined based on the following weighted average assumptions: 2017 2016 2015 Weighted average exercise price per share $ 50.57 $ 35.27 $ 50.85 Expected life in years 6.3 6.2 6.0 Expected volatility 35 % 38 % 33 % Expected dividend yield 3.0 % 3.0 % 2.0 % Risk-free interest rate 2.1 % 1.4 % 1.7 % Weighted average grant date fair value of stock option awards granted $ 13.42 $ 9.84 $ 13.44
Summary of Stock Option Award Activity	The following is a summary of our common stock option activity in 2017 : Number of of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Terms (in years) Aggregate Intrinsic Value (in millions) Outstanding at December 31, 2016 9,531,440 $ 28.93 Granted 1,214,112 50.57 Exercised (2,201,768 ) 21.88 Forfeited, canceled or expired (78,386 ) 41.97 Outstanding at December 31, 2017 8,465,398 33.74 Vested and expected to vest at December 31, 2017 8,445,963 33.71 5.5 $ 273 Exercisable at December 31, 2017 5,992,586 29.16 4.4 221
Summary of Restricted Stock Award Activity	The following is a summary of restricted stock award activity of our common stock in 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 579,122 50.25 36,345 53.19 RS’s Vested/RSU’s Issued (547,927 ) 42.54 (98,548 ) 29.49 Forfeited (92,876 ) 44.32 (13,750 ) 50.20 Outstanding at December 31, 2017 1,188,662 45.07 285,164 29.95
Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity, Vested And Unvested	The following is a summary of the values related to restricted stock and restricted stock unit awards held by MPC employees and non-employee directors: Restricted Stock Restricted Stock Units Intrinsic Value of Awards Vested During the Period (in millions) Weighted Average Grant Date Fair Value of Awards Granted During the Period Intrinsic Value of Awards Vested During the Period (in millions) Weighted Average Grant Date Fair Value of Awards Granted During the Period 2017 $ 28 $ 50.25 $ 5 $ 53.19 2016 17 36.17 8 40.85 2015 27 50.64 21 49.87
Schedule of Performance Unit Awards	The following table presents a summary of the 2017 activity for performance unit awards to be settled in shares: 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 (133,658 ) 0.82 Outstanding at December 31, 2017 6,851,542 0.81
Schedule of Share-based Compensation, Performance Unit Awards, Valuation Assumptions	Performance units to be settled in MPC shares have a grant date fair value calculated using a Monte Carlo valuation model, which requires the input of subjective assumptions. The following table provides a summary of these assumptions: 2017 2016 2015 Risk-free interest rate 1.5 % 1.0 % 1.0 % Look-back period (in years) 2.8 2.8 2.8 Expected volatility 36.1 % 34.2 % 30.4 % Grant date fair value of performance units granted $ 0.92 $ 0.57 $ 0.95

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2017
Leases [Abstract]
Schedule Of Future Minimum Commitments	Future minimum commitments as of December 31, 2017 , for capital lease obligations and for operating lease obligations having initial or remaining non-cancellable lease terms in excess of one year are as follows: (In millions) Capital Lease Obligations Operating Lease Obligations 2018 $ 50 $ 255 2019 49 224 2020 54 205 2021 49 177 2022 49 152 Later years 265 463 Total minimum lease payments 516 $ 1,476 Less imputed interest costs 152 Present value of net minimum lease payments $ 364
Schedule Of Operating Lease Rental Expense	Operating lease rental expense was: (In millions) 2017 2016 2015 Rental expense $ 301 $ 327 $ 331
Schedule of Future Minimum Rental Payments for Operating Leases	The following is a schedule of minimum future rentals on the non‑cancellable operating leases as of December 31, 2017 : (In millions) 2018 $ 194 2019 194 2020 193 2021 181 2022 172 Later years 320 Total minimum lease payments $ 1,254
Schedule of Property Subject to or Available for Operating Lease	The following schedule summarizes our investment in assets held for operating lease by major classes as of December 31, 2017 : (In millions) Natural gas gathering and NGL transportation pipelines and facilities $ 735 Natural gas processing facilities 644 Construction in progress 50 Property, plant and equipment 1,429 Less accumulated depreciation 153 Total property, plant and equipment $ 1,276

Selected Quarterly Financial 61

Selected Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Data [Abstract]
Schedule Of Quarterly Financial Information	2017 2016 (In millions, except per share data) 1st Qtr. 2nd Qtr. 3rd Qtr. 4th Qtr. (a) 1st Qtr. 2nd Qtr. 3rd Qtr. 4th Qtr. Revenues $ 16,288 $ 18,180 $ 19,210 $ 21,055 $ 12,755 $ 16,811 $ 16,618 $ 17,155 Income from operations 292 982 1,576 1,119 75 1,315 435 553 Net income (loss) 101 574 1,004 2,125 (78 ) 783 219 289 Net income attributable to MPC 30 483 903 2,016 1 801 145 227 Net income attributable to MPC per share: Basic $ 0.06 $ 0.94 $ 1.79 $ 4.13 $ 0.003 $ 1.51 $ 0.28 $ 0.43 Diluted 0.06 0.93 1.77 4.09 0.003 1.51 0.27 0.43 Dividends paid per share 0.36 0.36 0.40 0.40 0.32 0.32 0.36 0.36 (a) During the fourth quarter of 2017, we recorded a tax benefit of approximately $1.5 billion as a result of remeasuring certain deferred tax liabilities using the lower corporate tax rate enacted under the TCJA.

Supplementary Statistics (Table

Supplementary Statistics (Tables)	12 Months Ended
	Dec. 31, 2017
Text Block [Abstract]
Supplementary Statistics	(In millions) 2017 2016 2015 Income from Operations by segment Refining & Marketing (a)(b) $ 2,321 $ 1,357 $ 3,997 Speedway (b) 732 734 673 Midstream (a) 1,339 1,048 463 Items not allocated to segments: Corporate and other unallocated items (a) (365 ) (268 ) (293 ) Pension settlement expenses (52 ) (7 ) (4 ) Litigation (29 ) — — Impairment (c) 23 (486 ) (144 ) Income from operations $ 3,969 $ 2,378 $ 4,692 Capital Expenditures and Investments (d) Refining & Marketing (a) $ 832 $ 1,054 $ 1,045 Speedway 381 303 501 Midstream (a)(e) 2,505 1,568 14,545 Corporate and Other (f) 138 144 192 Total $ 3,856 $ 3,069 $ 16,283 (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) In 2016, the Refining & Marketing and Speedway segments include an inventory LCM benefit of $345 million and $25 million , respectively. In 2015, the Refining & Marketing and Speedway segments include an inventory LCM charge of $345 million and $25 million , respectively. (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. 2015 relates to the cancellation of the Residual Oil Upgrader Expansion project. See Notes 16 and 17 to the audited consolidated financial statements. (d) Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates. (e) 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. 2015 includes $13.85 billion for the MarkWest Merger. (f) Includes capitalized interest of $55 million , $63 million and $37 million for 2017 , 2016 and 2015 , respectively.
Operating Statistics	Supplementary Statistics (Unaudited) 2017 2016 2015 MPC Consolidated Refined Product Sales Volumes (mbpd) (a) 2,311 2,269 2,301 Refining & Marketing Operating Statistics Refining & Marketing refined product sales volume (mbpd) (b) 2,301 2,259 2,289 Refining & Marketing margin (dollars per barrel) (c) $ 12.60 $ 11.16 $ 15.16 Crude oil capacity utilization percent (d) 97 95 99 Refinery throughputs (mbpd): (e) Crude oil refined 1,765 1,699 1,711 Other charge and blendstocks 179 151 177 Total 1,944 1,850 1,888 Sour crude oil throughput percent 59 60 55 WTI-priced crude oil throughput percent 21 19 20 Refined product yields (mbpd): (e) Gasoline 932 900 913 Distillates 641 617 603 Propane 36 35 36 Feedstocks and special products 277 241 281 Heavy fuel oil 37 32 31 Asphalt 63 58 55 Total 1,986 1,883 1,919 Refinery direct operating costs (dollars per barrel): (f) Planned turnaround and major maintenance $ 1.72 $ 1.83 $ 1.13 Depreciation and amortization 1.43 1.47 1.39 Other manufacturing (g) 4.07 4.09 4.15 Total $ 7.22 $ 7.39 $ 6.67 Refining & Marketing Operating Statistics By Region – Gulf Coast Refinery throughputs (mbpd): (h) Crude oil refined 1,070 1,039 1,060 Other charge and blendstocks 224 195 184 Total 1,294 1,234 1,244 Sour crude oil throughput percent 71 73 68 WTI-priced crude oil throughput percent 11 8 6 Refined product yields (mbpd): (h) Gasoline 546 514 534 Distillates 405 399 392 Propane 26 26 26 Feedstocks and special products 311 286 286 Heavy fuel oil 25 21 15 Asphalt 17 15 16 Total 1,330 1,261 1,269 Refinery direct operating costs (dollars per barrel): (f) Planned turnaround and major maintenance $ 1.75 $ 2.09 $ 0.81 Depreciation and amortization 1.12 1.14 1.09 Other manufacturing (g) 3.74 3.70 3.88 Total $ 6.61 $ 6.93 $ 5.78 Supplementary Statistics (Unaudited) 2017 2016 2015 Refining & Marketing Operating Statistics By Region – Midwest Refinery throughputs (mbpd): (h) Crude oil refined 695 660 651 Other charge and blendstocks 33 39 39 Total 728 699 690 Sour crude oil throughput percent 40 40 34 WTI-priced crude oil throughput percent 37 38 43 Refined product yields (mbpd): (h) Gasoline 386 386 379 Distillates 236 218 211 Propane 11 11 12 Feedstocks and special products 42 35 38 Heavy fuel oil 13 12 17 Asphalt 46 43 39 Total 734 705 696 Refinery direct operating costs (dollars per barrel): (f) Planned turnaround and major maintenance $ 1.48 $ 1.15 $ 1.64 Depreciation and amortization 1.81 1.88 1.83 Other manufacturing (g) 4.26 4.29 4.36 Total $ 7.55 $ 7.32 $ 7.83 Speedway Operating Statistics (i) Convenience stores at period-end 2,744 2,733 2,766 Gasoline and distillate sales (millions of gallons) 5,799 6,094 6,038 Gasoline & distillate margin (dollars per gallon) (j) $ 0.1738 $ 0.1656 $ 0.1823 Merchandise sales (in millions) $ 4,893 $ 5,007 $ 4,879 Merchandise margin (in millions) $ 1,402 $ 1,435 $ 1,368 Merchandise margin percent 28.7 % 28.7 % 28.0 % Same store gasoline sales volume (period over period) (1.3 )% (0.4 )% (0.3 )% Same store merchandise sales (period over period) (k) 1.2 % 3.2 % 4.1 % Midstream Operating Statistics Crude oil and refined product pipeline throughputs (mbpd) (l) 3,377 2,948 2,829 Terminal throughput (mbpd) (m) 1,477 1,505 — Gathering system throughput (MMcf/d) (n) 3,608 3,275 3,075 Natural gas processed (MMcf/d) (n) 6,460 5,761 5,468 C2 (ethane) + NGLs (natural gas liquids) fractionated (mbpd) (n) 394 335 307 (a) Total average daily volumes of refined product sales to wholesale, branded and retail customers. (b) Includes intersegment sales. (c) Excludes LCM inventory valuation adjustments. Sales revenue less cost of refinery inputs and purchased products, divided by total refinery throughputs. Comparable prior period information for R&M margin has been recast in connection with the contribution of certain pipeline assets to MPLX on March 1, 2017. (d) Based on calendar day capacity, which is an annual average that includes downtime for planned maintenance and other normal operating activities. (e) Excludes inter-refinery volumes of 78 mbpd, 83 mbpd and 46 mbpd for 2017 , 2016 and 2015 , respectively. (f) Per barrel of total refinery throughputs. (g) Includes utilities, labor, routine maintenance and other operating costs. (h) Includes inter-refinery transfer volumes. (i) 2017 operating statistics do not reflect any information for the 41 travel centers contributed to PFJ Southeast, whereas they are reflected in prior years. (j) 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. (k) Excludes cigarettes. (l) Includes common-carrier pipelines and private pipelines contributed to MPLX, excluding equity method investments. (m) Includes the results of the terminal assets contributed to MPLX from the date the assets became a business, April 1, 2016. (n) Includes the results of the MarkWest assets beginning on the Dec. 4, 2015 acquisition date. Includes amounts related to unconsolidated equity method investments on a 100 percent basis.

Summary Of Principal Accounti63

Summary Of Principal Accounting Policies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)Company	Dec. 31, 2016USD ($)
Summary Of Principal Accounting Policies [Line Items]
Restricted cash | $	$ 4	$ 5
Accounts receivable number of days past-due evaluated for doubtful accounts	180 days
Stock Options
Summary Of Principal Accounting Policies [Line Items]
Implied volatility rate weighting (in percentage)	50.00%
Historical volatility rate weighting (in percentage)	50.00%
Minimum
Summary Of Principal Accounting Policies [Line Items]
Number of companies engaged in crude oil or refinery feedstock trading agreement | Company	100
Estimated useful lives (in years)	3 years
Maximum
Summary Of Principal Accounting Policies [Line Items]
Estimated useful lives (in years)	49 years
Accounts Receivable with Master Netting Arrangements | Customer Concentration Risk
Summary Of Principal Accounting Policies [Line Items]
Percentage of accounts receivable related to sales of crude oil refinery feed stocks to customers with master netting agreements	23.00%	23.00%
MPLX LP
Summary Of Principal Accounting Policies [Line Items]
MPC's ownership percentage of the general partner interest	100.00%
Noncontrolling interest (in percentage)	69.60%
MPLX LP | General Partner and Limited Partner
Summary Of Principal Accounting Policies [Line Items]
MPC's partnership interest in MPLX (in percentage)	30.40%
MPLX LP | General Partner
Summary Of Principal Accounting Policies [Line Items]
MPC's partnership interest in MPLX (in percentage)	2.00%

MPLX LP (Narrative) (Detail)

MPLX LP (Narrative) (Detail) - MPLX LP	Dec. 31, 2017
Noncontrolling Interest [Line Items]
MPC's ownership percentage of the general partner interest	100.00%
Noncontrolling interest (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 Transac

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
Noncontrolling Interest [Line Items]
General partners' contributed capital			$ 225
Limited Partner
Noncontrolling Interest [Line Items]
Units issued, number of units	19	13	7	23
General Partner and Limited Partner
Noncontrolling Interest [Line Items]
Increase in ownership percentage by MPC			1.00%

MPLX LP (Private Placement of P

MPLX LP (Private Placement of Preferred Units) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	May 13, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Noncontrolling Interest [Line Items]
Issuance of MPLX LP redeemable preferred units		$ 0	$ 984	$ 0
Series A Convertible Preferred Units | MPLX LP
Noncontrolling Interest [Line Items]
Preferred units, dividend rate, percentage	6.50%
Issuance of MPLX LP redeemable preferred units	$ 984
Preferred units, dividend 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.
Series A Convertible Preferred Units | MPLX LP | Preferred Units
Noncontrolling Interest [Line Items]
Sale of units (number of units)	30.8
Units issued, price per unit	$ 32.50

MPLX LP (Dropdowns to MPLX) (De

MPLX LP (Dropdowns to MPLX) (Details) - USD ($) shares in Thousands, $ in Millions	Sep. 01, 2017	Mar. 01, 2017	Sep. 01, 2016	Mar. 31, 2016	Dec. 04, 2015
MPLX Pipe Line Holdings LP
Noncontrolling Interest [Line Items]
Additional interest sold					0.50%
Proceeds from sale of ownership interest in assets sold by company in affiliate					$ 12
MPLX LP
Noncontrolling Interest [Line Items]
Total fair value of consideration transferred	$ 1,050	$ 2,000
MPLX LP | MPLX Pipe Line Holdings LP
Noncontrolling Interest [Line Items]
Ownership interest (in percentage)					100.00%
MPLX LP | 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
MPLX LP | General Partner
Noncontrolling Interest [Line Items]
Units issued, number of units	378	264		460
MPLX LP | Cash and cash equivalents
Noncontrolling Interest [Line Items]
Cash payment for acquisition	$ 420	$ 1,500

MPLX LP (Public Offerings) (Det

MPLX LP (Public Offerings) (Details) - MPLX LP - USD ($) $ in Millions	Sep. 01, 2017	Mar. 01, 2017	Feb. 10, 2017
Cash and cash equivalents
Noncontrolling Interest [Line Items]
Cash payment for acquisition	$ 420	$ 1,500
Senior Notes | MPLX senior notes, 4.125%, due March 2027
Noncontrolling Interest [Line Items]
Long-term debt, gross			$ 1,250
Debt instrument, interest rate			4.125%
Senior Notes | MPLX senior notes, 5.200%, due March 2047
Noncontrolling Interest [Line Items]
Long-term debt, gross			$ 1,000
Debt instrument, interest rate			5.20%

MPLX LP (ATM Program) (Details)

MPLX LP (ATM Program) (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Noncontrolling Interest [Line Items]
Issuance of MPLX LP common units	$ 473	$ 776	$ 0
MPLX LP | ATM Program
Noncontrolling Interest [Line Items]
Issuance of MPLX LP common units	$ 473
MPLX LP | ATM Program | Limited Partners Common Units
Noncontrolling Interest [Line Items]
Sale of units (number of units)	14

MPLX LP (Noncontrolling Interes

MPLX LP (Noncontrolling Interest) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Increase (decrease) in MPC's additional paid-in capital, net of tax	$ 444	$ 658	$ 6,923
Additional Paid-in Capital
Changes due to the issuance of MPLX LP common units to the public	25	(60)	1,532
Changes due to the issuance of MPLX LP common units and general partner units to MPC	114	121	0
Net transfers (to) from noncontrolling interests	139	61	1,532
Tax impact	(29)	(118)	(404)
Increase (decrease) in MPC's additional paid-in capital, net of tax	$ 110	$ (57)	$ 1,128

Acquisitions and Investments (A

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]
Cash payment for acquisition | $	$ 219

Acquisitions and Investments (R

Acquisitions and Investments (Revenues and Earnings of Ozark Pipeline Included in Consolidated Statements of Income) (Details) - Ozark Pipeline $ in Millions	10 Months Ended
	Dec. 31, 2017USD ($)
Business Acquisition [Line Items]
Sales and other operating revenues (including consumer excise taxes)	$ 38
Income from operations	$ 20

Acquisitions and Investments (I

Acquisitions and Investments (Investment in Pipeline Company) (Details) bbl / d in Thousands, $ in Millions	Feb. 15, 2017USD ($)bbl / dPeriod	Dec. 31, 2017USD ($)
Schedule of Equity Method Investments [Line Items]
IDRs forfeited per quarter	$ 1.6
Number of quarters IDRs forfeited | Period	12
Prorated IDRs forfeited	$ 0.8
MarEn Bakken Company LLC
Schedule of Equity Method Investments [Line Items]
Cash paid to acquire equity method investments	$ 500	$ 500
Equity method investments, ownership percentage		25.00%
Bakken Pipeline System
Schedule of Equity Method Investments [Line Items]
Crude oil throughput | bbl / d	520
MPLX LP | MarEn Bakken Company LLC
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%
MPLX & Enbridge Energy Partners | MarEn Bakken Company LLC
Schedule of Equity Method Investments [Line Items]
Cash paid to acquire equity method investments	$ 2,000
MPLX & 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 (F

Acquisitions and Investments (Formation of Gathering and Processing Joint Venture) (Details) bbl / d in Thousands, $ in Millions	Jan. 01, 2017USD ($)bbl / d	Dec. 31, 2017USD ($)		Dec. 31, 2016USD ($)	[1]	Dec. 31, 2015USD ($)
Schedule of Equity Method Investments [Line Items]
Contribution of fixed assets to joint venture		$ 337	[1]	$ 273		$ 0
MPLX LP
Schedule of Equity Method Investments [Line Items]
Gain (loss) on disposition of assets	$ 2
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 fixed 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 | Direct Ownership Interest
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	79.00%	69.00%
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 fixed assets to joint venture	$ 203
Fair value of assets contributed	$ 209
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]	2017 includes MPLX’s contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. 2016 includes Speedway’s contribution of travel plaza locations to new joint venture with Pilot Flying J. See Note 5.

Acquisitions and Investments 75

Acquisitions and Investments (Formation of Travel Plaza Joint Venture) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)	[1]	Dec. 31, 2016USD ($)Store		Dec. 31, 2015USD ($)
Schedule of Equity Method Investments [Line Items]
Contribution of fixed assets to joint venture	$ 337		$ 273	[1]	$ 0
PFJ Southeast
Schedule of Equity Method Investments [Line Items]
Contribution of fixed assets to joint venture			273
PFJ Southeast | Property, Plant and Equipment
Schedule of Equity Method Investments [Line Items]
Contribution of fixed assets to joint venture			203
PFJ Southeast | Goodwill
Schedule of Equity Method Investments [Line Items]
Contribution of fixed assets to joint venture			62
PFJ Southeast | Inventories
Schedule of Equity Method Investments [Line Items]
Contribution of fixed assets to joint venture			$ 8
PFJ Southeast | Speedway
Schedule of Equity Method Investments [Line Items]
Convenience stores | Store			41
PFJ Southeast | Pilot Flying J
Schedule of Equity Method Investments [Line Items]
Convenience stores | Store			82
[1]	2017 includes MPLX’s contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. 2016 includes Speedway’s contribution of travel plaza locations to new joint venture with Pilot Flying J. See Note 5.

Acquisitions and Investments (M

Acquisitions and Investments (Marine Investments) (Details) $ in Millions	1 Months Ended	12 Months Ended			16 Months Ended
	May 31, 2016USD ($)	Dec. 31, 2017vessel	Dec. 31, 2016Joint_venturevessel	Dec. 31, 2015vessel	Dec. 31, 2016USD ($)Joint_venturevessel	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%	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		4	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		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 77

Acquisitions and Investments (Merger with MarkWest Energy Partners, L.P.) (Details) $ / shares in Units, $ in Millions	Dec. 04, 2015USD ($)reporting_unit$ / shares	Jul. 31, 2017USD ($)	Jul. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)reporting_unit	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Business Acquisition [Line Items]
Payable to MPLX Class B unitholders									$ 50
Goodwill				$ 4,019			$ 3,586	$ 3,587	4,019
Number of reporting units | reporting_unit						3
Impairment expense							0	130
Midstream
Business Acquisition [Line Items]
Goodwill				2,627			2,276	2,276	$ 2,627
Impairment expense					$ 1	$ 129		130
MPLX LP
Business Acquisition [Line Items]
Goodwill							$ 2,245	$ 2,245
MarkWest
Business Acquisition [Line Items]
Cash consideration to unitholders (per unit) | $ / shares	$ 6.20
Cash payment to MarkWest unitholders	$ 1,230			$ 1,280
Payable to MPLX Class B unitholders	50	$ 25	$ 25
Goodwill	$ 2,210
Number of reporting units | reporting_unit	3
Transaction costs	$ 6
MarkWest | Selling, General and Administrative Expenses
Business Acquisition [Line Items]
Transaction costs	30
MarkWest | Net Interest and Other Financial Income
Business Acquisition [Line Items]
Transaction costs	6
MarkWest | Midstream
Business Acquisition [Line Items]
Impairment expense					$ 1	$ 129
Transaction costs	$ 36
MarkWest | MPLX LP
Business Acquisition [Line Items]
Common units conversion ratio	1.09

Acquisitions and Investments 78

Acquisitions and Investments (Fair Value of Consideration Transferred - MarkWest) (Details) - USD ($) $ in Millions	Dec. 04, 2015	Jul. 31, 2017	Jul. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Fair value of MPLX units issued					$ 0	$ 0	$ 7,326	[1]
Payable to MPLX Class B unitholders							$ 50
MarkWest
Business Acquisition [Line Items]
Fair value of MPLX units issued	$ 7,326
Cash payment to MarkWest unitholders	1,230			$ 1,280
Payable to MPLX Class B unitholders	50	$ 25	$ 25
Total fair value of consideration transferred	$ 8,606
[1]	See Note 5 for further information.

Acquisitions and Investments 79

Acquisitions and Investments (Revenues and Earnings of MarkWest Included in Consolidated Statements of Income) (Details) - MarkWest $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Business Acquisition [Line Items]
Sales and other operating revenues (including consumer excise taxes)	$ 120
Income from operations	$ 32

Acquisitions and Investments (S

Acquisitions and Investments (Schedule of Acquisition Related Pro Forma Financial Information (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)$ / shares
Business Combinations [Abstract]
Sales and other operating revenues (including consumer excise taxes) | $	$ 73,760
Net income attributable to MPC | $	$ 2,825
Net income attributable to MPC per share – basic | $ / shares	$ 5.25
Net income attributable to MPC per share – diluted | $ / shares	$ 5.21

Variable Interest Entities (Det

Variable Interest Entities (Details) bbl / d in Thousands, $ in Millions	Dec. 31, 2017USD ($)		Jan. 01, 2017bbl / d	Dec. 31, 2016USD ($)	May 31, 2016
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 4,787			$ 3,827
Crowley Coastal Partners
Schedule of Equity Method Investments [Line Items]
Maximum loss exposure, amount	$ 486
Equity method investments, ownership percentage	50.00%				50.00%
Equity method investments	$ 188			184
MarkWest Utica EMG
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	56.00%
Equity method investments	$ 2,139	[1]		2,224
Ohio Gathering
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	34.00%
Sherwood Midstream
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	50.00%
Equity method investments	$ 236	[1]		0
Ohio Fractionation
Schedule of Equity Method Investments [Line Items]
Capacity | bbl / d			20
Sherwood Midstream Holdings
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 165	[1],[2]		$ 0
Sherwood Midstream Holdings | Direct Ownership Interest
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	69.00%		79.00%
Sherwood Midstream Holdings | Indirect Ownership Interest
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage			10.50%
[1]	Ownership interest held by MPLX as of December 31, 2017
[2]	Excludes Sherwood Midstream LLC’s investment in Sherwood Midstream Holdings LLC.

Related Party Transactions (Nar

Related Party Transactions (Narrative) (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	May 31, 2016	Sep. 30, 2015
Related Party Transaction [Line Items]
Long-term receivable from related party	$ 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%
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%
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 (Sal

Related Party Transactions (Sales to Related Parties) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Sales to related parties	$ 629	$ 62	$ 6
PFJ Southeast
Related Party Transaction [Line Items]
Sales to related parties	619	56	0
Other equity method investees
Related Party Transaction [Line Items]
Sales to related parties	$ 10	$ 6	$ 6

Related Party Transactions (Oth

Related Party Transactions (Other Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Other income from related parties	$ 52	$ 41	$ 4
MarkWest Utica EMG
Related Party Transaction [Line Items]
Other income from related parties	17	16	0
Ohio Gathering
Related Party Transaction [Line Items]
Other income from related parties	16	15	2
Sherwood Midstream
Related Party Transaction [Line Items]
Other income from related parties	8	0	0
Other equity method investees
Related Party Transaction [Line Items]
Other income from related parties	$ 11	$ 10	$ 2

Related Party Transactions (Pur

Related Party Transactions (Purchases From Related Parties) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Purchases from related parties	$ 570	$ 509	$ 308
Crowley Blue Water Partners
Related Party Transaction [Line Items]
Purchases from related parties	60	37	0
Crowley Ocean Partners
Related Party Transaction [Line Items]
Purchases from related parties	79	52	6
Illinois Extension Pipeline
Related Party Transaction [Line Items]
Purchases from related parties	100	110	4
LOCAP
Related Party Transaction [Line Items]
Purchases from related parties	22	23	23
LOOP
Related Party Transaction [Line Items]
Purchases from related parties	71	59	52
TAAE
Related Party Transaction [Line Items]
Purchases from related parties	72	41	52
TACE
Related Party Transaction [Line Items]
Purchases from related parties	44	59	54
TAME
Related Party Transaction [Line Items]
Purchases from related parties	76	93	87
Other equity method investees
Related Party Transaction [Line Items]
Purchases from related parties	$ 46	$ 35	$ 30

Related Party Transactions (Rec

Related Party Transactions (Receivables From Related Parties) (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Current receivables from related parties	$ 36	$ 45
PFJ Southeast
Related Party Transaction [Line Items]
Current receivables from related parties	28	40
Other equity method investees
Related Party Transaction [Line Items]
Current receivables from related parties	$ 8	$ 5

Related Party Transactions (Pay

Related Party Transactions (Payables To Related Parties) (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Payables to related parties	$ 69	$ 53
Illinois Extension Pipeline
Related Party Transaction [Line Items]
Payables to related parties	8	9
LOOP
Related Party Transaction [Line Items]
Payables to related parties	3	6
MarkWest Utica EMG
Related Party Transaction [Line Items]
Payables to related parties	29	24
Ohio Gathering
Related Party Transaction [Line Items]
Payables to related parties	9	0
Sherwood Midstream
Related Party Transaction [Line Items]
Payables to related parties	8	0
Other equity method investees
Related Party Transaction [Line Items]
Payables to related parties	$ 12	$ 14

Income per Common Share (Summar

Income per Common Share (Summary Of Earnings Per Common Share) (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Basic earnings per share:
Net income attributable to MPC	$ 2,016	[1]	$ 903	$ 483	$ 30	$ 227	$ 145	$ 801	$ 1	$ 3,432	$ 1,174	$ 2,852
Income allocated to participating securities, basic										2	1	4
Income available to common stockholders – basic										$ 3,430	$ 1,173	$ 2,848
Weighted average common shares outstanding (in shares)										507	528	538
Basic (in USD per share)	$ 4.13		$ 1.79	$ 0.94	$ 0.06	$ 0.43	$ 0.28	$ 1.51	$ 0.003	$ 6.76	$ 2.22	$ 5.29
Diluted earnings per share:
Net income attributable to MPC	$ 2,016	[1]	$ 903	$ 483	$ 30	$ 227	$ 145	$ 801	$ 1	$ 3,432	$ 1,174	$ 2,852
Income allocated to participating securities, diluted										2	1	4
Income available to common stockholders – diluted										$ 3,430	$ 1,173	$ 2,848
Weighted average common shares outstanding (in shares)										507	528	538
Effect of dilutive securities (in shares)										5	2	4
Weighted average common shares, including dilutive effect (in shares)										512	530	542
Diluted (in USD per share)	$ 4.09		$ 1.77	$ 0.93	$ 0.06	$ 0.43	$ 0.27	$ 1.51	$ 0.003	$ 6.70	$ 2.21	$ 5.26
[1]	During the fourth quarter of 2017, we recorded a tax benefit of approximately $1.5 billion as a result of remeasuring certain deferred tax liabilities using the lower corporate tax rate enacted under the TCJA.

Income Per Common Share (Anti-d

Income Per Common Share (Anti-dilutive Shares) (Detail) - shares shares in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Shares issued under stock-based compensation plans
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	1	3	1

Equity (Narrative) (Detail)

Equity (Narrative) (Detail) - USD ($) $ in Millions	Dec. 31, 2017	May 31, 2017
Equity [Abstract]
Stock repurchase program, authorized amount		$ 3,000
Stock repurchase plan remaining authorized amount	$ 3,190

Equity (Share Repurchases) (Det

Equity (Share Repurchases) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity [Abstract]
Number of shares repurchased	44	4	19
Cash paid for shares repurchased	$ 2,372	$ 197	$ 965
Average cost per share	$ 53.85	$ 41.84	$ 50.31

Segment Information (Narrative)

Segment Information (Narrative) (Detail)	12 Months Ended
	Dec. 31, 2017Segmentrefinery	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Number of reportable segments | Segment	3
Number of refineries | refinery	6
None | Maximum
Segment Reporting Information [Line Items]
Percent of annual revenues	10.00%	10.00%	10.00%

Segment Information (Income Fro

Segment Information (Income From Operations Attributable To Operating Segments) (Detail) - USD ($) $ in Millions		Mar. 01, 2017	Feb. 15, 2017	Dec. 04, 2015	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)													$ 74,104		$ 63,277		$ 72,045
Sales to related parties													629		62		6
Income from operations					$ 1,119	$ 1,576	$ 982	$ 292	$ 553	$ 435	$ 1,315	$ 75	3,969		2,378		4,692
Income from equity method investments													306		(185)		88
Depreciation and amortization													2,114		2,001		1,502
Segment capital expenditures and investments													3,856		3,069		16,283
Inventory market valuation adjustment													0		(370)		370
MarkWest
Segment Reporting Information [Line Items]
Segment capital expenditures and investments				$ 13,850
Transaction costs				6
MarEn Bakken Company LLC
Segment Reporting Information [Line Items]
Cash paid to acquire equity method investments			$ 500										500
Refining & Marketing
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)													52,761		43,167		52,168
Sales to related parties													621		61		6
Inventory market valuation adjustment	[1]														(345)		345
Speedway
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)													19,021		18,282		19,690
Sales to related parties													8		1		0
Inventory market valuation adjustment	[1]														(25)		25
Midstream
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)													2,322		1,828		187
Sales to related parties													0		0		0
Midstream | Ozark Pipeline
Segment Reporting Information [Line Items]
Segment capital expenditures and investments		$ 220											220
Midstream | MarkWest
Segment Reporting Information [Line Items]
Transaction costs				$ 36
Reportable Segment
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)													74,104		63,277		72,045
Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)													12,756		11,854		12,957
Intersegment Eliminations | Refining & Marketing
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)	[2]												11,309		10,589		12,024
Intersegment Eliminations | Speedway
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)	[2]												4		3		3
Intersegment Eliminations | Midstream
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)	[2]												1,443		1,262		930
Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)													87,489		75,193		85,008
Income from operations													4,392		3,139		5,133
Income from equity method investments													283	[3]	171	[3]	88
Depreciation and amortization	[3]												2,056		1,941		1,450
Segment capital expenditures and investments													3,718		2,925		16,091
Cash paid to acquire equity method investments	[4]												805		431		2,788
Operating Segments | Refining & Marketing
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)													64,691		53,817		64,198
Income from operations	[5]												2,321		1,357	[6]	3,997	[6]
Income from equity method investments													17		24		26
Depreciation and amortization													1,082		1,063		1,052
Segment capital expenditures and investments	[5],[7]												832		1,054		1,045
Operating Segments | Speedway
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)													19,033		18,286		19,693
Income from operations													732		734	[6]	673	[6]
Income from equity method investments													69		5		0
Depreciation and amortization													275		273		254
Segment capital expenditures and investments	[7]												381		303		501
Operating Segments | Midstream
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)													3,765		3,090		1,117
Income from operations	[5]												1,339		1,048		463	[8]
Income from equity method investments													197		142		62
Depreciation and amortization													699		605		144
Segment capital expenditures and investments	[5],[7]												$ 2,505	[9]	$ 1,568		$ 14,545	[10]
[1]	2017 includes MPC’s share of gains related to the sale of assets remaining from the Sandpiper pipeline project. 2016 includes impairments of goodwill and equity method investments. 2015 relates to the cancellation of the ROUX project at our Garyville refinery. See Notes 16 and 17.
[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]	2017 includes an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system. 2016 includes an adjustment of $143 million to the fair value of equity method investments acquired in connection with the MarkWest Merger. 2015 includes $2.46 billion related to the MarkWest Merger. See Note 5
[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]	In 2016, the Refining & Marketing and Speedway segments include an inventory LCM benefit of $345 million and $25 million, respectively. In 2015, the Refining & Marketing and Speedway segments include an inventory LCM charge of $345 million and $25 million, respectively.
[7]	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates
[8]	Included in the Midstream segment for 2015 are $36 million of transaction costs related to the MarkWest Merger.
[9]	In 2017, 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. See Note 5.
[10]	The Midstream segment includes $13.85 billion for the MarkWest Merger.

Segment Information (Reconcilia

Segment Information (Reconciliation Of Segment Income From Operations To Income Before Income Taxes) (Detail) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations		$ 1,119	$ 1,576	$ 982	$ 292	$ 553	$ 435	$ 1,315	$ 75	$ 3,969	$ 2,378	$ 4,692
Net interest and other financial income (costs)										625	556	318
Income before income taxes										3,344	1,822	4,374
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations										4,392	3,139	5,133
Corporate and Other
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations	[1],[2]									(365)	(268)	(293)
Segment Reconciling Items
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pension settlement expenses	[3]									(52)	(7)	(4)
Litigation										(29)	0	0
Impairment	[4]									$ 23	$ (486)	$ (144)
[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 22 for further information.
[4]	2017 includes MPC’s share of gains related to the sale of assets remaining from the Sandpiper pipeline project. 2016 includes impairments of goodwill and equity method investments. 2015 relates to the cancellation of the ROUX project at our Garyville refinery. See Notes 16 and 17.

Segment Information (Reconcil95

Segment Information (Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures) (Detail) - USD ($) $ in Millions		Feb. 15, 2017	Dec. 04, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting, Other Significant Reconciling Item [Line Items]
Segment capital expenditures and investments				$ 3,856	$ 3,069	$ 16,283
Plus items not allocated to segments:
Total capital expenditures	[1]			3,051	2,638	13,495
MarkWest
Segment Reporting, Other Significant Reconciling Item [Line Items]
Segment capital expenditures and investments			$ 13,850
Scenario, Adjustment | MarkWest
Segment Reporting, Other Significant Reconciling Item [Line Items]
Investments in equity method investments					143
Scenario, Previously Reported | MarkWest
Segment Reporting, Other Significant Reconciling Item [Line Items]
Investments in equity method investments			$ 2,460
MarEn Bakken Company LLC
Segment Reporting, Other Significant Reconciling Item [Line Items]
Investments in equity method investments		$ 500		500
Operating Segments
Segment Reporting, Other Significant Reconciling Item [Line Items]
Segment capital expenditures and investments				3,718	2,925	16,091
Investments in equity method investments	[2]			805	431	2,788
Corporate and Other
Segment Reporting, Other Significant Reconciling Item [Line Items]
Segment capital expenditures and investments	[3],[4]			138	144	192
Plus items not allocated to segments:
Corporate and Other				83	81	155
Capitalized interest				$ 55	$ 63	$ 37
[1]	Capital expenditures include changes in capital accruals. See Note 20 for a reconciliation of total capital expenditures to additions to property, plant and equipment as reported in the consolidated statements of cash flows.
[2]	2017 includes an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system. 2016 includes an adjustment of $143 million to the fair value of equity method investments acquired in connection with the MarkWest Merger. 2015 includes $2.46 billion related to the MarkWest Merger. See Note 5
[3]	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates
[4]	Includes capitalized interest of $55 million, $63 million and $37 million for 2017, 2016 and 2015, respectively.

Segment Information (Schedule O

Segment Information (Schedule Of Revenues By Product Line) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)	$ 74,104	$ 63,277	$ 72,045
Refined products
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)	63,846	54,450	63,738
Merchandise
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)	5,174	5,297	5,188
Crude oil and refinery feedstocks
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)	3,403	2,038	2,718
Service, transportation and other
Segment Reporting Information [Line Items]
Sales and other operating revenues (including consumer excise taxes)	$ 1,681	$ 1,492	$ 401

Segment Information (Total Asse

Segment Information (Total Assets By Reportable Segment) (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting, Asset Reconciling Item [Line Items]
Total consolidated assets	$ 49,047	$ 44,413
Operating Segments | Refining & Marketing
Segment Reporting, Asset Reconciling Item [Line Items]
Total consolidated assets	17,537	17,601
Operating Segments | Speedway
Segment Reporting, Asset Reconciling Item [Line Items]
Total consolidated assets	5,563	5,426
Operating Segments | Midstream
Segment Reporting, Asset Reconciling Item [Line Items]
Total consolidated assets	19,937	18,516
Corporate and Other
Segment Reporting, Asset Reconciling Item [Line Items]
Total consolidated assets	$ 6,010	$ 2,870

Other Items (Net Interest And O

Other Items (Net Interest And Other Financial Income (Costs)) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015		Dec. 04, 2015
Interest income		$ 27	$ 6	$ 6
Interest expense	[1]	(688)	(602)	(325)
Interest capitalized		63	64	37
Loss on extinguishment of debt		0	0	(5)
Other financial costs		(27)	(24)	(31)	[2]
Net interest and other financial income (costs)		(625)	(556)	(318)
MarkWest
Transaction costs						$ 6
MarkWest | MPLX LP | Senior Notes
Amortization of debt discount		$ 46	$ 44	$ 1
[1]	ncludes $46 million, $44 million and $1 million for 2017, 2016 and 2015, respectively, for the amortization of the discount related to the difference between the fair value and the principal amount of assumed MarkWest debt
[2]	2015 includes $6 million of transaction costs related to the MarkWest Merger.

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Detail) - USD ($) $ in Millions	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statutory rate applied to income before income taxes		35.00%	35.00%	35.00%
Change in enacted tax rate, amount		$ 1,500
Unrecognized tax benefits that would impact effective income tax rate		10
Uncertain tax positions, reasonably possible increase or decrease during the next twelve months		10
Unrecognized tax benefits income tax net penalties and interest expense (benefits)		3	$ (5)	$ 3
Interest and penalties accrued		$ 17	$ 13
Scenario, Forecast
Statutory rate applied to income before income taxes	21.00%

Income Taxes (Components Of Inc

Income Taxes (Components Of Income Tax Provisions (Benefits)) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current
Federal	$ 681	$ 189	$ 1,210
State and local	98	27	152
Foreign	(6)	(1)	10
Total	773	215	1,372
Deferred
Federal	(1,270)	336	134
State and local	33	57	9
Foreign	4	1	(9)
Total	(1,233)	394	134
Total
Federal	(589)	525	1,344
State and local	131	84	161
Foreign	(2)	0	1
Total	$ (460)	$ 609	$ 1,506

Income Taxes (Reconciliation Of

Income Taxes (Reconciliation Of Federal Statutory Income Tax Rate) (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Statutory rate applied to income before income taxes	35.00%	35.00%	35.00%
State and local income taxes, net of federal income tax effects	2.00%	3.00%	2.00%
Domestic manufacturing deduction	(1.00%)	(1.00%)	(2.00%)
Noncontrolling interests	(4.00%)	(1.00%)	(0.00%)
Biodiesel excise tax credit	(0.00%)	(1.00%)	(1.00%)
TCJA legislation	(45.00%)	(0.00%)	(0.00%)
Other	(1.00%)	(2.00%)	0.00%
Provision for income taxes	(14.00%)	33.00%	34.00%

Income Taxes (Components Of Def

Income Taxes (Components Of Deferred Tax Assets And Liabilities) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Employee benefits	$ 348	$ 578
Environmental	16	34
Deferred revenue	21	31
Net operating loss carryforwards	12	23
Other	23	27
Total deferred tax assets	420	693
Deferred tax liabilities:
Property, plant and equipment	1,603	2,591
Inventories	473	707
Investments in subsidiaries and affiliates	912	1,145
Other	73	94
Total deferred tax liabilities	3,061	4,537
Net deferred tax liabilities	2,641	$ 3,844
Change in enacted tax rate, amount	$ 1,500

Income Taxes (Components Of Net

Income Taxes (Components Of Net Deferred Tax Liabilities Classified In Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Assets
Other noncurrent assets	$ 13	$ 17
Liabilities
Deferred income taxes	2,654	3,861
Net deferred tax liabilities	$ 2,641	$ 3,844

Income Taxes (Tax Carryforwards

Income Taxes (Tax Carryforwards) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
United States Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 5	$ 18
United States Federal | Minimum
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, expiration date	Jan. 1, 2022
United States Federal | Maximum
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, expiration date	Dec. 31, 2036
States
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 8	$ 8
States | Minimum
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, expiration date	Jan. 1, 2017
States | Maximum
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, expiration date	Dec. 31, 2036

Income Taxes (Valuation Allowan

Income Taxes (Valuation Allowances) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Valuation allowance	$ 11	$ 10

Income Taxes (Summary Of Income

Income Taxes (Summary Of Income Tax Returns Subject To Examination) (Detail)	12 Months Ended
	Dec. 31, 2017
United States Federal | Minimum
Income Tax Examination [Line Items]
Tax years	2,010
United States Federal | Maximum
Income Tax Examination [Line Items]
Tax years	2,016
States | Minimum
Income Tax Examination [Line Items]
Tax years	2,008
States | Maximum
Income Tax Examination [Line Items]
Tax years	2,016

Income Taxes (Summary Of Activi

Income Taxes (Summary Of Activity In Unrecognized Tax Benefits) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
January 1 balance	$ 7	$ 12	$ 12
Additions for tax positions of prior years	13	6	0
Reductions for tax positions of prior years	0	(10)	0
Settlements, decrease	(1)	(1)	0
December 31 balance	$ 19	$ 7	$ 12

Inventories (Summary Of Invento

Inventories (Summary Of Inventories) (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Crude oil and refinery feedstocks	$ 2,056	$ 2,208
Refined products	2,839	2,810
Materials and supplies	494	485
Merchandise	161	153
Total	$ 5,550	$ 5,656

Inventories (Narrative) (Detail

Inventories (Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Inventory Disclosure [Abstract]
Total inventory LIFO percentage	90.00%	91.00%
Excess of current acquisition costs over stated LIFO value	$ 1,210	$ 308
Effect of LIFO inventory liquidation on income	$ (7)	$ 0	$ (78)

Equity Method Investments (Sche

Equity Method Investments (Schedule Of Equity Method Investments) (Detail) - USD ($) $ in Millions		Jan. 01, 2017	Dec. 31, 2017		Feb. 15, 2017	Dec. 31, 2016	May 31, 2016
Schedule of Equity Method Investments [Line Items]
Equity method investments			$ 4,787			$ 3,827
MPLX LP
Schedule of Equity Method Investments [Line Items]
Equity method investments			$ 4,010			2,471
Centennial
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage			50.00%
Equity method investments			$ 35			35
Centrahoma Processing LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage			40.00%
Equity method investments			$ 121	[1]		104
Crowley Coastal Partners
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage			50.00%				50.00%
Equity method investments			$ 188			184
Explorer
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage			25.00%
Equity method investments			$ 89	[1]		94
Illinois Extension Pipeline
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage			35.00%
Equity method investments			$ 284	[1]		293
LOOP
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage			51.00%
Equity method investments			$ 282			277
LOOP | MPLX LP
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage			41.00%
MarEn Bakken Company LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage			25.00%
Equity method investments			$ 520	[1]		0
MarEn Bakken Company LLC | MPLX LP
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage					25.00%
MarkWest EMG Jefferson Dry Gas
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage			67.00%
Equity method investments			$ 164	[1]		67
MarkWest Utica EMG
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage			56.00%
Equity method investments			$ 2,139	[1]		2,224
PFJ Southeast
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage			29.00%
Equity method investments			$ 328			283
Sherwood Midstream
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage			50.00%
Equity method investments			$ 236	[1]		0
Sherwood Midstream Holdings
Schedule of Equity Method Investments [Line Items]
Equity method investments			$ 165	[1],[2]		0
Sherwood Midstream Holdings | Direct Ownership Interest
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		79.00%	69.00%
TAAE
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage			45.00%
Equity method investments			$ 39			33
TACE
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage			61.00%
Equity method investments			$ 32			$ 33
TAEI
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage			0.00%			34.00%
Equity method investments			$ 0	[3]		$ 15
TAME
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage			67.00%
Equity method investments	[3]		$ 33			18
Percentage of partners interest acquired		17.00%
Other equity method investees
Schedule of Equity Method Investments [Line Items]
Equity method investments			65			91
Other equity method investees | MPLX LP
Schedule of Equity Method Investments [Line Items]
Equity method investments			$ 67			$ 76
[1]	Ownership interest held by MPLX as of December 31, 2017
[2]	Excludes Sherwood Midstream LLC’s investment in Sherwood Midstream Holdings LLC.
[3]	On January 1, 2017, we contributed our 34 percent interest in TAEI to TAME in exchange for a 17 percent in TAME.

Equity Method Investments (Summ

Equity Method Investments (Summarized Financial Information For Equity Method Investees) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income statement data:
Revenues and other income	$ 6,235	$ 2,421	$ 1,390
Income (loss) from operations	1,075	(116)	332
Net income (loss)	922	(250)	$ 239
Balance sheet data – December 31:
Current assets	860	711
Noncurrent assets	10,854	8,170
Current liabilities	547	884
Noncurrent liabilities	$ 1,714	$ 1,462

Equity Method Investments (Narr

Equity Method Investments (Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Equity method investment difference between carrying amount and underlying equity	$ 1,170
Equity method investment difference between carrying amount and underlying equity, portion related to goodwill which is not being amortized	509
Equity method investments	4,787	$ 3,827
Dividends and partnership distributions received from equity method investees	388	291	$ 113
Centennial
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 35	$ 35
Percent of debt outstanding	50.00%
Centennial | Financial Guarantee
Schedule of Equity Method Investments [Line Items]
Maximum potential undiscounted payments	$ 25

Property, Plant And Equipmen113

Property, Plant And Equipment (Summary Of Property, Plant And Equipment) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 40,538	$ 38,006
Less accumulated depreciation	14,095	12,241
Net property, plant and equipment	26,443	25,765
Operating Segments | Refining & Marketing
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	19,490	18,590	[1]
Operating Segments | Speedway
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	5,358	5,078
Operating Segments | Midstream
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	14,898	13,521	[1]
Corporate and Other
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 792	$ 817
Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	3 years
Minimum | Operating Segments | Refining & Marketing
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	4 years
Minimum | Operating Segments | Speedway
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	4 years
Minimum | Operating Segments | Midstream
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	3 years
Minimum | Corporate and Other
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	4 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	49 years
Maximum | Operating Segments | Refining & Marketing
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	30 years
Maximum | Operating Segments | Speedway
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	25 years
Maximum | Operating Segments | Midstream
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	49 years
Maximum | Corporate and Other
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	40 years
[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.

Property, Plant And Equipmen114

Property, Plant And Equipment (Narrative) (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 40,538	$ 38,006
Property, plant and equipment, accumulated depreciation	14,095	12,241
Assets held under capital leases
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	576	505
Property, plant and equipment, accumulated depreciation	237	202
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 2,200	$ 2,020

Goodwill (Narrative) (Detail)

Goodwill (Narrative) (Detail) $ in Millions	3 Months Ended		12 Months Ended
	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)reporting_unit	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Goodwill [Line Items]
Number of reporting units | reporting_unit		3
Number of reporting units impaired | reporting_unit		2
Impairment expense			$ 0	$ 130
Fair Value, Measurements, Nonrecurring
Goodwill [Line Items]
Impairment expense			$ 0	130	$ 0
Midstream
Goodwill [Line Items]
Impairment expense	$ 1	$ 129		$ 130
Midstream | Fair Value, Measurements, Nonrecurring | Goodwill | Minimum
Goodwill [Line Items]
Discount rate		10.50%
Midstream | Fair Value, Measurements, Nonrecurring | Goodwill | Maximum
Goodwill [Line Items]
Discount rate		11.50%

Goodwill (Changes In Carrying A

Goodwill (Changes In Carrying Amount Of Goodwill) (Detail) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
		Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Beginning balance			$ 4,019	$ 3,587	$ 4,019
Goodwill, purchase price accounting adjustments					(241)
Goodwill, disposition				(1)	(61)
Goodwill, impairment				0	(130)
Transfer of assets related to dropdowns(b)					0
Ending balance				3,586	3,587
Refining & Marketing
Goodwill [Line Items]
Beginning balance			539	519	539
Goodwill, purchase price accounting adjustments					0
Goodwill, disposition				0	0
Goodwill, impairment					0
Transfer of assets related to dropdowns(b)	[1]				(20)
Ending balance				519	519
Speedway
Goodwill [Line Items]
Beginning balance			853	792	853
Goodwill, purchase price accounting adjustments					0
Goodwill, disposition	[2]			(1)	(61)
Goodwill, impairment					0
Transfer of assets related to dropdowns(b)					0
Ending balance				791	792
Midstream
Goodwill [Line Items]
Beginning balance			2,627	2,276	2,627
Goodwill, purchase price accounting adjustments					(241)
Goodwill, disposition				0	0
Goodwill, impairment		$ (1)	$ (129)		(130)
Transfer of assets related to dropdowns(b)	[1]				20
Ending balance				$ 2,276	$ 2,276
[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.
[2]	Goodwill associated with our former Speedway travel plaza locations that are now part of the PFJ Southeast joint venture. The amount was included in the initial basis for our equity method investment in the joint venture.

Intangibles (Intangible Assets

Intangibles (Intangible Assets by Major Class) (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Gross		$ 987	$ 924
Accumulated amortization		(261)	(199)
Net		726	725
Customer contracts and relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross		654	636
Royalty agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Gross		129	128
Favorable lease contract terms
Acquired Finite-Lived Intangible Assets [Line Items]
Gross		56	58
Other intangible assets
Acquired Finite-Lived Intangible Assets [Line Items]
Gross		148	102
Refining & Marketing
Acquired Finite-Lived Intangible Assets [Line Items]
Gross		322	258
Accumulated amortization		(143)	(123)
Net		179	135
Indefinite-lived intangible assets		48
Refining & Marketing | Customer contracts and relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross		120	102
Refining & Marketing | Royalty agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Gross		129	128
Refining & Marketing | Favorable lease contract terms
Acquired Finite-Lived Intangible Assets [Line Items]
Gross		0	1
Refining & Marketing | Other intangible assets
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	[1]	73	27
Speedway
Acquired Finite-Lived Intangible Assets [Line Items]
Gross		132	133
Accumulated amortization		(39)	(35)
Net		93	98
Indefinite-lived intangible assets		46
Speedway | Customer contracts and relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross		1	1
Speedway | Royalty agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Gross		0	0
Speedway | Favorable lease contract terms
Acquired Finite-Lived Intangible Assets [Line Items]
Gross		56	57
Speedway | Other intangible assets
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	[1]	75	75
Midstream
Acquired Finite-Lived Intangible Assets [Line Items]
Gross		533	533
Accumulated amortization		(79)	(41)
Net		454	492
Midstream | Customer contracts and relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross		533	533
Midstream | Royalty agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Gross		0	0
Midstream | Favorable lease contract terms
Acquired Finite-Lived Intangible Assets [Line Items]
Gross		0	0
Midstream | Other intangible assets
Acquired Finite-Lived Intangible Assets [Line Items]
Gross		$ 0	$ 0
[1]	The Refining & Marketing and Speedway segments include unamortized intangible assets of $48 million and $46 million, respectively, which are primarily emission allowance credits and trademarks.

Intangibles (Narrative) (Detail

Intangibles (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible asset acquired	$ 45	[1]	$ 0	$ 0
Amortization expense	$ 52		$ 55
[1]	See Note 16 for further information.

Intangibles (Estimated Future A

Intangibles (Estimated Future Amortization Expense) (Details) $ in Millions	Dec. 31, 2017USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2,018	$ 52
2,019	52
2,020	50
2,021	49
2,022	$ 48

Fair Value Measurements (Assets

Fair Value Measurements (Assets And Liabilities Accounted For At Fair Value On Recurring Basis) (Detail) - USD ($) $ in Millions		Dec. 31, 2017		Mar. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash collateral netted with derivative liabilities		$ 8			$ 24
Contingent consideration, current					130
Embedded derivative in commodity contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Embedded derivative instruments, current		12			13
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - collateral and netting		(118)			(688)
Commodity derivative instruments, assets - collateral pledged not offset		8			126
Other assets		3			2
Total assets at fair value		12			2
Commodity derivative instruments, liabilities - netting and collateral		(126)			(712)
Commodity derivative instruments, liabilities - collateral pledged not offset		0			0
Contingent consideration, liability				$ 131	130	[1]
Total liabilities at fair value		66			190
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		130			690
Contingent consideration, liability					0
Total liabilities at fair value		126			712
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 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	[1]				130
Total liabilities at fair value		66			190
Fair Value, Measurements, Recurring | Commodity derivative instruments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - collateral and netting	[2]	(118)			(688)
Commodity derivative instruments, assets - net	[3]	9			0
Commodity derivative instruments, assets - collateral pledged not offset		8			126
Commodity derivative instruments, liabilities - netting and collateral	[2]	(126)			(712)
Commodity derivative instruments, liabilities, net	[3]	2			6
Commodity derivative instruments, liabilities - collateral pledged not offset		0			0
Fair Value, Measurements, Recurring | Commodity derivative instruments | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - gross		127			688
Commodity derivative instruments, liabilities - gross		126			712
Fair Value, Measurements, Recurring | Commodity derivative instruments | Level 2
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 | Commodity derivative instruments | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - gross		0			0
Commodity derivative instruments, liabilities - gross		2			6
Fair Value, Measurements, Recurring | Embedded derivative in commodity contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, liabilities - netting and collateral		0	[2]		0
Commodity derivative instruments, liabilities, net	[3]	64	[4]		54
Commodity derivative instruments, liabilities - collateral pledged not offset		0			0
Fair Value, Measurements, Recurring | Embedded derivative in commodity contracts | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, liabilities - gross		0			0
Fair Value, Measurements, Recurring | Embedded derivative in commodity contracts | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, liabilities - gross		0			0
Fair Value, Measurements, Recurring | Embedded derivative in commodity contracts | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, liabilities - gross		$ 64			$ 54
[1]	Includes $130 million classified as current as of December 31, 2016.
[2]	Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of December 31, 2017, cash collateral of $8 million was netted with mark-to-market derivative liabilities. As of December 31, 2016, cash collateral of $24 million was netted with mark-to-market derivative liabilities.
[3]	We have no derivative contracts which are subject to master netting arrangements reflected gross on the balance sheet.
[4]	Includes $12 million and $13 million classified as current as of December 31, 2017 and 2016, respectively.

Fair Value Measurements (Recurr

Fair Value Measurements (Recurring Narrative) (Detail) - USD ($)		Apr. 12, 2017	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016		Feb. 01, 2013
Galveston Bay Refinery and Related Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maximum earnout provision payable to the company							$ 700,000,000
Contingent consideration payment		$ 131,000,000
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration, liability				$ 131,000,000	$ 130,000,000	[1]
Embedded derivative in commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Embedded derivative renewal term			5 years
Level 3 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration, liability	[1]				$ 130,000,000
Level 3 | Commodity derivative instruments | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward commodity price			$ 0.24
Level 3 | Commodity derivative instruments | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward commodity price			$ 1.45
Level 3 | Embedded derivative in commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Probability of renewal			60.00%
Probability of renewal second term			80.00%
[1]	Includes $130 million classified as current as of December 31, 2016.

Fair Value Measurements (Reconc

Fair Value Measurements (Reconciliation Of Net Beginning And Ending Balances Recorded For Net Assets And Liabilities Classified As Level 3) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		$ 190	$ 342	$ 478
Contingent consideration payment	[1]	(131)	(200)	(189)
Net derivative positions assumed - MarkWest Merger		0	0	31
Unrealized and realized losses included in net income		25	55	20
Settlements of derivative instruments		(18)	(7)	2
Ending balance		66	190	342
Contingent consideration payment		$ (89)	$ (164)	$ (175)
[1]	On the consolidated statements of cash flows for 2017, 2016, and 2015, $89 million, $164 million and $175 million, respectively, of the contingent earnout payment to BP was included as a financing activity with the remainder included as an operating activity.

Fair Value Measurements (Gains_

Fair Value Measurements (Gains/Losses Included In Earnings Relating to Assets Still Held at the End of Period) (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in unrealized gain (loss)	$ 9	$ 45	$ 21
Derivative
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in unrealized gain (loss)	8	32	(7)
Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in unrealized gain (loss)	$ 1	$ 13	$ 28

Fair Value Measurements (Ass124

Fair Value Measurements (Assets Measured At Fair Value On Nonrecurring Basis) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill, impairment	$ 0	$ 130
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investments, fair value	0	42	$ 0
Equity method investment, impairment	0	356	0
Goodwill, fair value	0	0	0
Goodwill, impairment	0	130	0
Property, plant and equipment, net, fair value	0	0	0
Property, plant and equipment, net, impairment	$ 0	$ 0	$ 144

Fair Value Measurements (Nonrec

Fair Value Measurements (Nonrecurring Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended			38 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016
North Dakota Pipeline
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investments, ownership percentage	37.50%
Cash paid to acquire equity method investments						$ 301
Ohio Condensate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investments, ownership percentage		60.00%
Ohio Condensate | Equity Method Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate		11.20%
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investment, impairment			$ 0	$ 356	$ 0
Impairment charge			$ 0	$ 0	$ 144
Fair Value, Measurements, Nonrecurring | North Dakota Pipeline
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Income (loss) from equity method investments	$ (267)
Fair Value, Measurements, Nonrecurring | Ohio Condensate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Income (loss) from equity method investments		$ (58)
Equity method investment, impairment		96
Income (loss) from equity method investments from elimination of basis differential		$ (31)

Fair Value Measurements (Financ

Fair Value Measurements (Financial Instruments At Fair Value, Excluding Derivative Financial Instruments) (Detail) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Fair Value
Financial assets:
Investments		$ 29	$ 25
Other		17	21
Total financial assets		46	46
Financial liabilities:
Long-term debt	[1]	13,893	10,892
Deferred credits and other liabilities		122	121
Total financial liabilities		14,015	11,013
Carrying Value
Financial assets:
Investments		2	2
Other		17	21
Total financial assets		19	23
Financial liabilities:
Long-term debt	[1]	12,642	10,297
Deferred credits and other liabilities		109	109
Total financial liabilities		$ 12,751	$ 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 derivative instruments - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Other current assets
Derivatives, Fair Value [Line Items]
Asset		$ 127	$ 688
Liability		126	712
Other current liabilities(a)
Derivatives, Fair Value [Line Items]
Asset		0	0
Liability	[1]	14	13
Deferred credits and other liabilities
Derivatives, Fair Value [Line Items]
Asset		0	0
Liability	[1]	$ 52	$ 47
[1]	Includes embedded derivatives.

Derivatives (Open Commodity Der

Derivatives (Open Commodity Derivative Contracts - Crude Oil) (Detail) - Crude Oil - Exchange Traded bbl in Thousands	12 Months Ended
	Dec. 31, 2017bbl
Derivative [Line Items]
Percentage of derivative contracts expiring in the period	99.80%
Derivative contract expiration date	Mar. 31, 2018
Long
Derivative [Line Items]
Notional contracts (in thousands of total barrels)	23,299	[1]
Short
Derivative [Line Items]
Notional contracts (in thousands of total barrels)	25,199	[1]
[1]	of the exchange-traded contracts expire in the first quarter of 2018.

Derivatives (Open Commodity 129

Derivatives (Open Commodity Derivative Contracts - Refined Product) (Details) - Refined products gal in Thousands	12 Months Ended
	Dec. 31, 2017gal
Exchange Traded
Derivative [Line Items]
Percentage of derivative contracts expiring in the period	100.00%
Derivative contract expiration date	Mar. 31, 2018
Exchange Traded | Long
Derivative [Line Items]
Notional contracts (in thousands of total gallons)	257,460	[1]
Exchange Traded | Short
Derivative [Line Items]
Notional contracts (in thousands of total gallons)	236,460	[1]
Over the Counter | Short
Derivative [Line Items]
Notional contracts (in thousands of total gallons)	9,587
[1]	of the exchange-traded contracts expire in the first quarter of 2018.

Derivatives (Effect Of Commodit

Derivatives (Effect Of Commodity Derivative Instruments In Statements Of Income) (Detail) - Commodity derivative instruments - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	$ (21)	$ (180)	$ 313
Sales and other operating revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	5	(13)	19
Cost of revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	$ (26)	$ (167)	$ 294

Debt (Outstanding Borrowings) (

Debt (Outstanding Borrowings) (Detail) - USD ($) $ in Millions		Jul. 21, 2017	Jul. 20, 2016	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Commercial paper				$ 0
Total				13,418	$ 11,069
Unamortized debt issuance costs				(59)	(44)
Unamortized discount	[1]			(413)	(453)
Amounts due within one year				(624)	(28)
Total long-term debt due after one year				12,322	10,544
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Capital lease obligations					8
364-day bank revolving credit facility due July 2018
Debt Instrument [Line Items]
Line of credit facility, expiration date		Jul. 20, 2018
364-day bank revolving credit facility due July 2018 | Line of Credit
Debt Instrument [Line Items]
Long-term debt, gross				0
Trade receivables securitization facility due July 2019
Debt Instrument [Line Items]
Line of credit facility, expiration date			Jul. 19, 2019
Bank revolving credit facility due 2022
Debt Instrument [Line Items]
Line of credit facility, expiration date		Jul. 21, 2022
Bank revolving credit facility due 2022 | Line of Credit
Debt Instrument [Line Items]
Long-term debt, gross				0
Marathon Petroleum Corporation
Debt Instrument [Line Items]
Commercial paper				0	0
Marathon Petroleum Corporation | Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Capital lease obligations				$ 356	311
Debt instrument maturity year, start				Jan. 1, 2018
Debt instrument maturity year, end				Mar. 31, 2033
Marathon Petroleum Corporation | 364-day bank revolving credit facility due July 2018 | Line of Credit
Debt Instrument [Line Items]
Long-term debt, gross				$ 0	0
Line of credit facility, expiration date				Jul. 20, 2018
Marathon Petroleum Corporation | Trade receivables securitization facility due July 2019 | Secured Debt
Debt Instrument [Line Items]
Long-term debt, gross				$ 0	0
Line of credit facility, expiration date				Jul. 19, 2019
Marathon Petroleum Corporation | Bank revolving credit facility due 2022 | Line of Credit
Debt Instrument [Line Items]
Long-term debt, gross				$ 0	0
Line of credit facility, expiration date				Jul. 21, 2022
Marathon Petroleum Corporation | Term loan agreement due 2019 | Unsecured Debt
Debt Instrument [Line Items]
Long-term debt, gross				$ 0	200
Line of credit facility, expiration date				Sep. 30, 2019
Marathon Petroleum Corporation | 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%
Marathon Petroleum Corporation | Senior notes, 3.400% due December 2020 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross				$ 650	650
Debt instrument, maturity date				Dec. 15, 2020
Debt instrument, interest rate				3.40%
Marathon Petroleum Corporation | Senior notes, 5.125% due March 2021 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross				$ 1,000	1,000
Debt instrument, maturity date				Mar. 1, 2021
Debt instrument, interest rate				5.125%
Marathon Petroleum Corporation | Senior notes, 3.625%, due September 2024 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross				$ 750	750
Debt instrument, maturity date				Sep. 15, 2024
Debt instrument, interest rate				3.625%
Marathon Petroleum Corporation | Senior notes, 6.500%, due March 2041 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross				$ 1,250	1,250
Debt instrument, maturity date				Mar. 1, 2041
Debt instrument, interest rate				6.50%
Marathon Petroleum Corporation | Senior notes, 4.750%, due September 2044 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross				$ 800	800
Debt instrument, maturity date				Sep. 15, 2044
Debt instrument, interest rate				4.75%
Marathon Petroleum Corporation | Senior notes, 5.850% due December 2045 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross				$ 250	250
Debt instrument, maturity date				Dec. 15, 2045
Debt instrument, interest rate				5.85%
Marathon Petroleum Corporation | Senior notes, 5.000%, due September 2054 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross				$ 400	400
Debt instrument, maturity date				Sep. 15, 2054
Debt instrument, interest rate				5.00%
MPLX LP | Senior Notes | MarkWest
Debt Instrument [Line Items]
Long-term debt, gross				$ 63	63
Unamortized discount				(374)	(420)
MPLX LP | Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Capital lease obligations				$ 7
Debt instrument maturity year, start				Jan. 1, 2018
Debt instrument maturity year, end				Mar. 31, 2020
MPLX LP | MPLX term loan facility due 2019 | Unsecured Debt
Debt Instrument [Line Items]
Long-term debt, gross				$ 0	250
Line of credit facility, expiration date				Nov. 20, 2019
MPLX LP | MPLX bank revolving credit facility due 2022 | Line of Credit
Debt Instrument [Line Items]
Long-term debt, gross				$ 505	0
Line of credit facility, expiration date				Jul. 21, 2022
MPLX LP | MPLX senior notes, 5.500%, due February 2023 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross				$ 710	710
Debt instrument, maturity date				Feb. 15, 2023
Debt instrument, interest rate				5.50%
MPLX LP | MPLX senior notes, 5.500%, due February 2023 | Senior Notes | MarkWest
Debt Instrument [Line Items]
Debt instrument, maturity date				Feb. 15, 2023
Debt instrument, interest rate				5.50%
MPLX LP | MPLX senior notes, 4.500%, due July 2023 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross				$ 989	989
Debt instrument, maturity date				Jul. 15, 2023
Debt instrument, interest rate				4.50%
MPLX LP | MPLX senior notes, 4.500%, due July 2023 | Senior Notes | MarkWest
Debt Instrument [Line Items]
Debt instrument, maturity date				Jul. 15, 2023
Debt instrument, interest rate				4.50%
MPLX LP | MPLX senior notes, 4.875%, due December 2024 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross				$ 1,149	1,149
Debt instrument, maturity date				Dec. 1, 2024
Debt instrument, interest rate				4.875%
MPLX LP | MPLX senior notes, 4.875%, due December 2024 | Senior Notes | MarkWest
Debt Instrument [Line Items]
Debt instrument, maturity date				Dec. 1, 2024
Debt instrument, interest rate				4.875%
MPLX LP | MPLX senior notes, 4.000%, due February 2025 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross				$ 500	500
Debt instrument, maturity date				Feb. 15, 2025
Debt instrument, interest rate				4.00%
MPLX LP | MPLX senior notes, 4.875%, due June 2025 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross				$ 1,189	1,189
Debt instrument, maturity date				Jun. 1, 2025
Debt instrument, interest rate				4.875%
MPLX LP | MPLX senior notes, 4.875%, due June 2025 | Senior Notes | MarkWest
Debt Instrument [Line Items]
Debt instrument, maturity date				Jun. 1, 2025
Debt instrument, interest rate				4.875%
MPLX LP | MPLX senior notes, 4.125%, due March 2027 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross				$ 1,250	0
Debt instrument, maturity date				Mar. 1, 2027
Debt instrument, interest rate				4.125%
MPLX LP | MPLX senior notes, 5.200%, due March 2047 | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross				$ 1,000	$ 0
Debt instrument, maturity date				Mar. 1, 2047
Debt instrument, interest rate				5.20%
[1]	Includes $374 million and $420 million unamortized discount as of December 31, 2017 and December 31, 2016, respectively, related to the difference at the time of the acquisition between the fair value and the principal amount of assumed MarkWest debt.

Debt (Schedule Of Debt Payments

Debt (Schedule Of Debt Payments) (Detail) $ in Millions	Dec. 31, 2017USD ($)
Debt Disclosure [Abstract]
2,018	$ 626
2,019	27
2,020	683
2,021	1,031
2,022	$ 537

Debt (Commercial Paper) (Detail

Debt (Commercial Paper) (Details) - USD ($) $ in Millions	Feb. 26, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Commercial paper – issued		$ 300	$ 1,263	$ 0
Commercial paper - repayments		300	$ 1,263	$ 0
Commercial paper outstanding		$ 0
Commercial Paper
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 2,000
Debt instrument, term	397 days

Debt (MPC Revolving Credit Agre

Debt (MPC Revolving Credit Agreements) (Detail) $ in Millions	Jul. 21, 2017USD ($)Period	Jul. 20, 2016USD ($)	Dec. 31, 2017USD ($)
Bank revolving credit facility due 2020
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity		$ 2,500
Debt instrument, term		4 years
364-day bank revolving credit facility due July 2018
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 1,000	$ 1,000
Debt instrument, term	364 days	364 days
Line of credit facility, expiration date	Jul. 20, 2018
364-day bank revolving credit facility due July 2018 | Line of Credit
Line of Credit Facility [Line Items]
Long-term debt outstanding			$ 0
364-day bank revolving credit facility due July 2018 | Letter of Credit
Line of Credit Facility [Line Items]
Letters of credit outstanding			0
Bank revolving credit facility due 2022
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 2,500
Debt instrument, term	5 years
Line of credit facility, expiration date	Jul. 21, 2022
Number of renewal periods | Period	2
Line of credit facility duration of renewal period	1 year
Bank revolving credit facility due 2022 | Line of Credit
Line of Credit Facility [Line Items]
Long-term debt outstanding			0
Bank revolving credit facility due 2022 | Letter of Credit
Line of Credit Facility [Line Items]
Letters of credit outstanding			$ 0
Bank revolving credit facility due 2022 | Maximum
Line of Credit Facility [Line Items]
Line of credit facility additional borrowing capacity	$ 500
Bank revolving credit facility due 2022 | Maximum | Bridge Loan
Line of Credit Facility [Line Items]
Line of credit facility, current borrowing capacity	100
Bank revolving credit facility due 2022 | Maximum | Letter of Credit
Line of Credit Facility [Line Items]
Line of credit facility, current borrowing capacity	$ 1,800
MPC bank revolving credit facilities
Line of Credit Facility [Line Items]
Debt instrument, description of variable rate basis	at either the Adjusted LIBO Rate or the Alternate Base Rate (both as defined in the MPC credit agreements), plus an applicable margin
MPC bank revolving credit facilities | Maximum
Line of Credit Facility [Line Items]
Ratio of indebtedness to net capital	0.65

Debt (Trade Receivables Securit

Debt (Trade Receivables Securitization Facility) (Details) - Trade receivables securitization facility due July 2019 - USD ($) $ in Millions	Jul. 20, 2016	Dec. 31, 2017	Sep. 30, 2016
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity	$ 750	$ 750	$ 1,000
Line of credit facility, expiration date	Jul. 19, 2019
Line of credit facility, maximum borrowing capacity	$ 750
Line of credit facility, borrowings during period		0
Line of credit facility, repayments during period		$ 0
Letter of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 750

Debt (MPC Term Loan) (Details)

Debt (MPC Term Loan) (Details) - MPC Term Loan - USD ($) $ in Millions	Mar. 31, 2017	Sep. 30, 2016	Aug. 26, 2014
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			$ 700
Debt instrument, term			5 years
Repayments of long-term debt	$ 200	$ 500

Debt (MPLX Credit Agreement) (D

Debt (MPLX Credit Agreement) (Details) - MPLX LP - MPLX bank revolving credit facility due 2022 $ in Millions	Jul. 21, 2017USD ($)Period	Dec. 31, 2017USD ($)	Oct. 27, 2015USD ($)
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 2,250		$ 2,000
Debt instrument, term	5 years
Number of renewal periods | Period	2
Line of credit facility duration of renewal period	1 year
Debt instrument, description of variable rate basis	Adjusted LIBO Rate or the Alternate Base Rate (both as defined in the MPLX credit agreement)
Line of credit facility, borrowings during period		$ 670
Line of credit facility, interest rate during period		2.70%
Line of credit facility, repayments during period		$ 165
Remaining borrowing capacity		1,740
Maximum
Debt Instrument [Line Items]
Line of credit facility additional borrowing capacity	$ 500
Number of prior quarterly reporting periods covenant	4
Covenant ratio debt to EBITDA	5
Covenant ratio debt to EBITDA post acquisition	5.5
Letter of Credit
Debt Instrument [Line Items]
Letters of credit outstanding		3
Letter of Credit | Maximum
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity	$ 222
Bridge Loan | Maximum
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity	$ 100
Line of Credit
Debt Instrument [Line Items]
Line of credit facility, expiration date	Jul. 21, 2022
Long-term debt outstanding		$ 505

Debt (MPLX Term Loan) (Details)

Debt (MPLX Term Loan) (Details) $ in Millions	Jul. 19, 2017USD ($)
MPLX LP | 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	Dec. 31, 2017	Feb. 10, 2017
Cash and cash equivalents
Debt Instrument [Line Items]
Cash payment for acquisition	$ 420	$ 1,500
Senior Notes
Debt Instrument [Line Items]
Proceeds from debt			$ 2,220
Senior Notes | MPLX senior notes, 4.125%, due March 2027
Debt Instrument [Line Items]
Long-term debt outstanding				$ 1,250
Debt instrument, interest rate				4.125%
Senior Notes | MPLX senior notes, 5.200%, due March 2047
Debt Instrument [Line Items]
Long-term debt outstanding				$ 1,000
Debt instrument, interest rate				5.20%

Supplemental Cash Flow Infor140

Supplemental Cash Flow Information (Summary Of Supplemental Cash Flow Information) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Net cash provided by operating activities included:
Interest paid (net of amounts capitalized)	$ 525		$ 478		$ 272
Net income taxes paid to taxing authorities	904		140		1,605
Non-cash investing and financing activities:
Capital lease obligations increase	71		0		1
Contribution of fixed assets to joint venture	337	[1]	273	[1]	0
Intangible asset acquired	45	[2]	0		0
Property, plant and equipment sold	0		0		5
Property, plant and equipment acquired	0		0		5
Acquisition:
Fair value of MPLX units issued	$ 0		$ 0		7,326	[3]
Payable to MPLX Class B unitholders					$ 50
[1]	2017 includes MPLX’s contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. 2016 includes Speedway’s contribution of travel plaza locations to new joint venture with Pilot Flying J. See Note 5.
[2]	See Note 16 for further information.
[3]	See Note 5 for further information.

Supplemental Cash Flow Infor141

Supplemental Cash Flow Information (Reconciliation Of Additions To Property, Plant And Equipment To Total Capital Expenditures) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Supplemental Cash Flow Information [Abstract]
Additions to property, plant and equipment per consolidated statements of cash flows		$ 2,732		$ 2,892		$ 1,998
Non-cash additions to property, plant and equipment		0		0		5
Asset retirement expenditures		2	[1]	6	[1]	1
Increase (decrease) in capital accruals		67		(127)		94
Total capital expenditures before acquisitions		2,801		2,771		2,098
Acquisitions	[2]	250		(133)		11,397
Total capital expenditures	[3]	$ 3,051		$ 2,638		$ 13,495
[1]	Included in All other, net – Operating activities on the consolidated statements of cash flows.
[2]	2017 reflects primarily the acquisition of the Ozark pipeline. 2016 includes adjustments to the fair values of property, plant and equipment, intangibles and goodwill acquired in connection with the MarkWest Merger. The 2015 acquisitions include the MarkWest Merger. The acquisition numbers above include property, plant and equipment, intangibles and goodwill.
[3]	Capital expenditures include changes in capital accruals. See Note 20 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 Comprehens142

Accumulated Other Comprehensive Loss (Changes in Accumulated Other Comprehensive Loss by Component) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		$ (234)	$ (318)
Other comprehensive income before reclassifications		(23)	86
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit		(42)	(49)
Amortization– actuarial loss		34	40
Amortization– settlement loss		52	7
Other		(2)	(1)
Tax effect		(16)	1
Other comprehensive income (loss)		3	84	$ (5)
Ending balance		(231)	(234)	(318)
Pension Benefits
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit		(39)	(46)	(46)
Other Benefits
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit		(3)	(3)	(4)
Accumulated Defined Benefit Plans Adjustment | Pension Benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(233)	(255)
Other comprehensive income before reclassifications		12	22
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit	[1]	(39)	(46)
Amortization– actuarial loss	[1]	36	38
Amortization– settlement loss	[1]	52	7
Tax effect		(18)	1
Other comprehensive income (loss)		43	22
Ending balance		(190)	(233)	(255)
Accumulated Defined Benefit Plans Adjustment | Other Benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(7)	(70)
Other comprehensive income before reclassifications		(38)	64
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit	[1]	(3)	(3)
Amortization– actuarial loss	[1]	(2)	2
Amortization– settlement loss	[1]	0	0
Tax effect		2	0
Other comprehensive income (loss)		(41)	63
Ending balance		(48)	(7)	(70)
Gain on Cash Flow Hedge
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		4	4
Other comprehensive income before reclassifications			0
Amounts reclassified from accumulated other comprehensive loss:
Tax effect		0	0
Other comprehensive income (loss)		0	0
Ending balance		4	4	4
Workers Compensation
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		2	3
Other comprehensive income before reclassifications		3	0
Amounts reclassified from accumulated other comprehensive loss:
Other	[2]	(2)	(1)
Tax effect		0	0
Other comprehensive income (loss)		1	(1)
Ending balance		$ 3	$ 2	$ 3
[1]	These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 22.
[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 143

Defined Benefit Pension And Other Postretirement Plans (Summary Of Defined Benefit Plans With Accumulated Benefit Obligations In Excess Of Plan Assets) (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Projected benefit obligations	$ 2,164	$ 2,024
Accumulated benefit obligations	2,008	1,914
Fair value of plan assets	$ 1,840	$ 1,659

Defined Benefit Pension And 144

Defined Benefit Pension And Other Postretirement Plans (Summary Of Projected Benefit Obligations And Funded Status For Defined Benefit Pension And Other Postretirement Plans) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Change in plan assets:
Fair value of plan assets at January 1		$ 1,659
Fair value of plan assets at December 31		1,840		$ 1,659
Amounts recognized in the consolidated balance sheets:
Noncurrent liabilities		(1,099)		(1,055)
Pension Benefits
Change in benefit obligations:
Benefit obligations at January 1		2,024		1,997
Service cost		132		114	$ 101
Interest cost		75		73	71
Actuarial (gain) loss		150		15
Benefits paid		(217)		(175)
Other		0		0
Benefit obligations at December 31		2,164		2,024	1,997
Change in plan assets:
Fair value of plan assets at January 1		1,659		1,570
Actual return on plan assets		270		145
Employer contributions		128		119
Benefits paid from plan assets		(217)		(175)
Fair value of plan assets at December 31		1,840		1,659	1,570
Funded status of plans at December 31		(324)		(365)
Amounts recognized in the consolidated balance sheets:
Current liabilities		(18)		(18)
Noncurrent liabilities		(306)		(347)
Accrued benefit cost		(324)		(365)
Pretax amounts recognized in accumulated other comprehensive loss:
Net actuarial loss		537	[1]	645
Prior service credit		(238)	[1]	(276)
Pension Benefits | LOOP LLC and Explorer Pipeline
Pretax amounts recognized in accumulated other comprehensive loss:
Net actuarial loss	[1]	17
Other Benefits
Change in benefit obligations:
Benefit obligations at January 1		740		800
Service cost		25		32	31
Interest cost		30		35	32
Actuarial (gain) loss		61		(101)
Benefits paid		(30)		(26)
Other		0		0
Benefit obligations at December 31		826		740	800
Change in plan assets:
Fair value of plan assets at January 1		0		0
Actual return on plan assets		0		0
Employer contributions		30		26
Benefits paid from plan assets		(30)		(26)
Fair value of plan assets at December 31		0		0	$ 0
Funded status of plans at December 31		(826)		(740)
Amounts recognized in the consolidated balance sheets:
Current liabilities		(33)		(32)
Noncurrent liabilities		(793)		(708)
Accrued benefit cost		(826)		(740)
Pretax amounts recognized in accumulated other comprehensive loss:
Net actuarial loss		80	[1]	17
Prior service credit		(3)	[1]	$ (6)
Other Benefits | LOOP LLC and Explorer Pipeline
Pretax amounts recognized in accumulated other comprehensive loss:
Net actuarial loss	[1]	$ 1
[1]	Amounts exclude those related to LOOP and Explorer, equity method investees with defined benefit pension and postretirement plans for which net losses of $17 million and less than $1 million were recorded in accumulated other comprehensive loss in 2017, reflecting our ownership share.

Defined Benefit Pension And 145

Defined Benefit Pension And Other Postretirement Plans (Components Of Net Periodic Benefit Cost And Other Comprehensive Loss) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax):
Amortization of prior service cost		$ 42	$ 49
Pension Benefits
Components of net periodic benefit cost:
Service cost		132	114	$ 101
Interest cost		75	73	71
Expected return on plan assets		(100)	(98)	(98)
Amortization – prior service credit		(39)	(46)	(46)
Amortization – actuarial loss		36	38	51
Amortization – settlement loss		52	7	4
Net periodic benefit cost	[1]	156	88	83
Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax):
Actuarial (gain) loss		(20)	(33)	69
Prior service cost (credit)		0	0	0
Amortization of actuarial loss		(88)	(45)	(55)
Amortization of prior service cost		39	46	46
Other		0	0	0
Total recognized in other comprehensive loss		(69)	(32)	60
Total recognized in net periodic benefit cost and other comprehensive loss		87	56	143
Estimated net gain (loss) that will be amortized from accumulated other comprehensive loss in 2017		36
Estimated prior service cost that will be amortized from accumulated other comprehensive loss in 2017		33
Other Benefits
Components of net periodic benefit cost:
Service cost		25	32	31
Interest cost		30	35	32
Expected return on plan assets		0	0	0
Amortization – prior service credit		(3)	(3)	(4)
Amortization – actuarial loss		(2)	2	8
Amortization – settlement loss		0	0	0
Net periodic benefit cost	[1]	50	66	67
Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax):
Actuarial (gain) loss		61	(101)	(63)
Prior service cost (credit)		0	0	13	[2]
Amortization of actuarial loss		2	(2)	(8)
Amortization of prior service cost		3	3	4
Other		0	0	0
Total recognized in other comprehensive loss		66	(100)	(54)
Total recognized in net periodic benefit cost and other comprehensive loss		116	$ (34)	$ 13
Estimated net gain (loss) that will be amortized from accumulated other comprehensive loss in 2017		1
Estimated prior service cost that will be amortized from accumulated other comprehensive loss in 2017		$ 3
[1]	Net periodic benefit cost reflects a calculated market-related value of plan assets which recognizes changes in fair value over three years.
[2]	Includes adjustments related to the MarkWest Merger in 2015

Defined Benefit Pension And 146

Defined Benefit Pension And Other Postretirement Plans (Summary Of Assumptions Used To Determine Benefit Obligations And Net Periodic Benefit Cost) (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Benefits
Weighted-average assumptions used to determine benefit obligation:
Discount rate	3.55%	3.90%	4.00%
Rate of compensation increase	5.00%	5.00%	3.70%
Weighted-average assumptions used to determine net periodic benefit cost:
Discount rate	3.85%	3.80%	3.70%
Expected long-term return on plan assets	6.50%	6.50%	6.75%
Rate of compensation increase	5.00%	5.00%	3.70%
Other Benefits
Weighted-average assumptions used to determine benefit obligation:
Discount rate	3.70%	4.25%	4.50%
Rate of compensation increase	5.00%	5.00%	3.70%
Weighted-average assumptions used to determine net periodic benefit cost:
Discount rate	4.25%	4.50%	4.30%
Expected long-term return on plan assets	0.00%	0.00%	0.00%
Rate of compensation increase	5.00%	5.00%	3.70%

Defined Benefit Pension and 147

Defined Benefit Pension and Other Postretirement Plans (Expected Long-Term Return on Plan Assets) (Details)	12 Months Ended
	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Defined benefit plan, investment goals	The overall expected long-term return on plan assets assumption is determined based on an asset rate-of-return modeling tool developed by a third-party investment group. The tool utilizes underlying assumptions based on actual returns by asset category and inflation and takes into account our asset allocation to derive an expected long-term rate of return on those assets. Capital market assumptions reflect the long-term capital market outlook. The assumptions for equity and fixed income investments are developed using a building-block approach, reflecting observable inflation information and interest rate information available in the fixed income markets. Long-term assumptions for other asset categories are based on historical results, current market characteristics and the professional judgment of our internal and external investment teams.

Defined Benefit Pension And 148

Defined Benefit Pension And Other Postretirement Plans (Summarizes Assumed Health Care Cost Trend Rates) (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Medical Pre-65
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for the following year:	6.75%	7.00%	7.50%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate):	4.50%	4.50%	5.00%
Year that the rate reaches the ultimate trend rate:	2,026	2,026	2,021
Prescription drugs
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for the following year:	8.75%	9.00%	7.00%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate):	4.50%	4.50%	5.00%
Year that the rate reaches the ultimate trend rate:	2,026	2,026	2,021
Medical Post-65 | Maximum
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for the following year:	4.00%

Defined Benefit Pension And 149

Defined Benefit Pension And Other Postretirement Plans (Effects Of One Percentage Point Change In Assumed Health Care Cost Trend Rates) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Effect on total of service and interest cost components, 1-Percentage-Point-Increase	$ 5
Effect on other postretirement benefit obligations, 1-Percentage-Point-Increase	38
Effect on total of service and interest cost components, 1-Percentage-Point Decrease	(4)
Effect on other postretirement benefit obligations, 1-Percentage-Point-Decrease	$ (33)

Defined Benefit Pension and 150

Defined Benefit Pension and Other Postretirement Plans (Plan Investment Policies And Strategies) (Details)	12 Months Ended
	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, diversification	The asset allocation strategy will change over time in response to changes primarily in funded status, which is dictated by current and anticipated market conditions, the independent actions of our investment committee, required cash flows to and from the plans and other factors deemed appropriate. Such changes in asset allocation are intended to allocate additional assets to the fixed income asset class should the funded status improve. The fixed income asset class shall be invested in such a manner that its interest rate sensitivity correlates highly with that of the plans’ liabilities. Other asset classes are intended to provide additional return with associated higher levels of risk.
Plan investment policies and strategies	Investment performance and risk is measured and monitored on an ongoing basis through quarterly investment meetings and periodic asset and liability studies.
Equity Securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Targeted asset allocation	51.00%
Fixed Income Securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Targeted asset allocation	49.00%

Defined Benefit Pension And 151

Defined Benefit Pension And Other Postretirement Plans (Fair Values Of Defined Benefit Pension Plan Assets) (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	$ 1,840	$ 1,659
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	14	24
Equity investments, common stocks
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	36	71
Equity funds, mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	227	160
Equity funds, pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	507	451
Fixed income, corporate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	674	570
Fixed income, government
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	98	90
Fixed income, pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	176	173
Private equity
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	51	60
Real estate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	34	39
Other
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	23	21
Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	265	233
Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 1 | Equity investments, common stocks
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	36	71
Level 1 | Equity funds, mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	227	160
Level 1 | Equity funds, pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 1 | Fixed income, corporate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 1 | Fixed income, government
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 1 | Fixed income, pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 1 | Private equity
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 1 | Real estate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 1 | Other
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	2	2
Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	1,470	1,308
Level 2 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	14	24
Level 2 | Equity investments, common stocks
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 2 | Equity funds, mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 2 | Equity funds, pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	507	451
Level 2 | Fixed income, corporate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	673	570
Level 2 | Fixed income, government
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	98	90
Level 2 | Fixed income, pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	176	173
Level 2 | Private equity
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 2 | Real estate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 2 | Other
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	2	0
Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	105	118	$ 131
Level 3 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 3 | Equity investments, common stocks
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 3 | Equity funds, mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 3 | Equity funds, pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 3 | Fixed income, corporate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	1	0
Level 3 | Fixed income, government
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 3 | Fixed income, pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 3 | Private equity
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	51	60	62
Level 3 | Real estate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	34	39	$ 50
Level 3 | Other
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	$ 19	$ 19

Defined Benefit Pension And 152

Defined Benefit Pension And Other Postretirement Plans (Reconciliation Of Beginning And Ending Balances Of Plan Assets Classified As Level 3) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	$ 1,659
Actual return on plan assets:
Fair value of plan assets at December 31	1,840	$ 1,659
Private equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	60
Actual return on plan assets:
Fair value of plan assets at December 31	51	60
Real estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	39
Actual return on plan assets:
Fair value of plan assets at December 31	34	39
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	118	131
Actual return on plan assets:
Realized	14	13
Unrealized	0	(1)
Purchases	4	3
Sales	(31)	(28)
Fair value of plan assets at December 31	105	118
Level 3 | Private equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	60	62
Actual return on plan assets:
Realized	11	8
Unrealized	(1)	2
Purchases	2	2
Sales	(21)	(14)
Fair value of plan assets at December 31	51	60
Level 3 | Real estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	39	50
Actual return on plan assets:
Realized	3	5
Unrealized	0	(3)
Purchases	1	1
Sales	(9)	(14)
Fair value of plan assets at December 31	34	39
Level 3 | Fixed income corporate and other plan assets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	19	19
Actual return on plan assets:
Realized	0	0
Unrealized	1	0
Purchases	1	0
Sales	(1)	0
Fair value of plan assets at December 31	$ 20	$ 19

Defined Benefit Pension and 153

Defined Benefit Pension and Other Postretirement Plans (Contributions To Defined Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions to defined contribution plans	$ 116	$ 113	$ 94
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension contributions	128
Unfunded Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plans, estimated future employer contributions in next fiscal year	18
Other Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plans, estimated future employer contributions in next fiscal year	$ 33

Defined Benefit Pension And 154

Defined Benefit Pension And Other Postretirement Plans (Estimated Future Benefit Payments) (Detail) $ in Millions	Dec. 31, 2017USD ($)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
2,018	$ 176
2,019	183
2,020	161
2,021	161
2,022	158
2023 through 2027	790
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
2,018	33
2,019	36
2,020	38
2,021	41
2,022	42
2023 through 2027	$ 229

Defined Benefit Pension And 155

Defined Benefit Pension And Other Postretirement Plans (Multiemployee Plans) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)Plan	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Defined Benefit Plan Disclosure [Line Items]
Marathon Petroleum's contributions as a percentage of total contributions to the multi-employer pension plan, maximum	5.00%
Multiemployer Plans, Pension
Defined Benefit Plan Disclosure [Line Items]
Number of multiemployer defined benefit pension or health and welfare plan	1
Funded percentage	65.00%
Multi employer pension plans	There have been no significant changes that affect the comparability of 2017 , 2016 and 2015 contributions.
Multiemployer Plans, Postretirement Benefit
Defined Benefit Plan Disclosure [Line Items]
Number of multiemployer defined benefit pension or health and welfare plan	1
MPC contributions | $	$ 7	$ 6	$ 7

Defined Benefit Pension And 156

Defined Benefit Pension And Other Postretirement Plans (Multi Employer Pension Plan) (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)Employee		Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Multiemployer Plans [Line Items]
EIN	366,044,243
Pension Protection Act zone status	Red		Red
Funding improvement plan and rehabilitation plan	Implemented
Surcharge - imposed	No
Expiration date of collective-bargaining arrangement	Jan. 31, 2019
Multiemployer Plans, Pension
Multiemployer Plans [Line Items]
Multiemployer pension plan, minimum contribution requirement per week per employee	$ 315
Number of employees participated in the plan | Employee	282
Multiemployer Plans, Pension | Central States, Southeast and Southwest Pension Plan [Member]
Multiemployer Plans [Line Items]
MPC contributions	$ 4,000,000	[1]	$ 4,000,000	$ 4,000,000
[1]	This agreement has a minimum contribution requirement of $315 per week per employee for 2018. A total of 282 employees participated in the plan as of December 31, 2017.

Stock-Based Compensation Pla157

Stock-Based Compensation Plans (Narrative) (Detail) shares in Millions	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, expiration period	10 years
Vesting period of awards	3 years
Restricted Stock Awards and Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards	3 years
Restricted stock and restricted stock unit awards granted in 2012, additional holding period	1 year
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target payout | $ / shares	$ 1
Maximum | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Actual payout | $ / shares	$ 2
Target payout percentage	200.00%
MPC 2012 Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock authorized to be delivered under the compensation plan	50
MPC 2012 Plan | Maximum | Awards Other Than Stock Options Or Stock Appreciation Rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock authorized to be delivered under the compensation plan	20
MPC 2012 Plan | Maximum | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock authorized to be delivered under the compensation plan	20
MPC 2012 and 2011 Plans | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards	36 months
Pay-out percentage in MPC common stock (in percentage)	25.00%
Pay-out percentage in cash (in percentage)	75.00%

Stock-Based Compensation Pla158

Stock-Based Compensation Plans (Stock-Based Compensation Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-based compensation expense	$ 51	$ 45	$ 42
Tax benefit recognized on stock-based compensation expense	19	17	16
Cash received by MPC upon exercise of stock option awards	46	10	33
Tax benefit received for tax deductions for stock awards exercised	$ 25	$ 4	$ 26

Stock-Based Compensation Pla159

Stock-Based Compensation Plans (Weighted Average Assumptions Used To Value Stock Options Awards) (Detail) - Stock Options - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average exercise price per share	$ 50.57	$ 35.27	$ 50.85
Expected life in years	6 years 3 months 20 days	6 years 2 months 14 days	6 years
Expected volatility	35.00%	38.00%	33.00%
Expected dividend yield	3.00%	3.00%	2.00%
Risk-free interest rate	2.10%	1.40%	1.70%
Weighted average grant date fair value of stock option awards granted	$ 13.42	$ 9.84	$ 13.44
Implied volatility rate weighting (in percentage)	50.00%
Historical volatility rate weighting (in percentage)	50.00%

Stock-Based Compensation Pla160

Stock-Based Compensation Plans (Summary Of Stock Option Award Activity) (Detail) - Stock Options - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of options exercised	$ 75	$ 14	$ 60
Unrecognized compensation cost	$ 9
Weighted average recognition period, in years	1 year 4 months
Number of Shares
Outstanding, beginning balance	9,531,440
Granted	1,214,112
Exercised	(2,201,768)
Forfeited, canceled or expired	(78,386)
Outstanding, ending balance	8,465,398	9,531,440
Vested and expected to vest at December 31, 2017 (in shares)	8,445,963
Exercisable at December 31, 2017 (in shares)	5,992,586
Weighted Average Exercise Price
Outstanding, beginning balance (in USD per share)	$ 28.93
Granted (in USD per share)	50.57	$ 35.27	$ 50.85
Exercised (in USD per share)	21.88
Forfeited, canceled or expired (in USD per share)	41.97
Outstanding, ending balance (in USD per share)	33.74	$ 28.93
Vested and expected to vest at December 31, 2017 (in USD per share)	33.71
Exercisable at December 31, 2017 (in USD per share)	$ 29.16
Weighted Average Remaining Contractual Terms (in years)
Vested and expected to vest at December 31, 2017 (in years)	5 years 6 months 16 days
Exercisable at December 31, 2017 (in years)	4 years 4 months 8 days
Aggregate Intrinsic Value (in millions)
Vested and expected to vest at December 31, 2017 (in USD)	$ 273
Exercisable at December 31, 2017 (in USD)	$ 221

Stock-Based Compensation Pla161

Stock-Based Compensation Plans (Summary Of Restricted Stock Award Activity) (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted units outstanding	285,164
Restricted Stock
Number of Shares
Outstanding, beginning balance	1,250,343
Granted	579,122
RS’s Vested/RSU’s Issued	(547,927)
Forfeited	(92,876)
Outstanding, ending balance	1,188,662	1,250,343
Weighted Average Grant Date Fair Value
Outstanding, beginning balance (in USD per share)	$ 41.51
Granted (in USD per share)	50.25	$ 36.17	$ 50.64
RS's Vested/RSU's Issued (in USD per share)	42.54
Forfeited (in USD per share)	44.32
Outstanding, ending balance (in USD per share)	$ 45.07	$ 41.51
Restricted Stock Units
Number of Shares
Outstanding, beginning balance	361,117
Granted	36,345
RS’s Vested/RSU’s Issued	(98,548)
Forfeited	(13,750)
Outstanding, ending balance	285,164	361,117
Weighted Average Grant Date Fair Value
Outstanding, beginning balance (in USD per share)	$ 28.26
Granted (in USD per share)	53.19	$ 40.85	$ 49.87
RS's Vested/RSU's Issued (in USD per share)	29.49
Forfeited (in USD per share)	50.20
Outstanding, ending balance (in USD per share)	$ 29.95	$ 28.26
Non-Employee Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted units vested	280,850
Weighted average fair value, vested	$ 29.72

Stock-Based Compensation Pla162

Stock-Based Compensation Plans (Summary Of Values Related To Vested And Unvested Restricted Stock Awards) (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic Value of Awards Vested During the Period (in millions)	$ 28	$ 17	$ 27
Weighted Average Grant Date Fair Value of Awards Granted During the Period	$ 50.25	$ 36.17	$ 50.64
Unrecognized compensation cost	$ 34
Weighted average recognition period, in years	1 year 3 months 20 days
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic Value of Awards Vested During the Period (in millions)	$ 5	$ 8	$ 21
Weighted Average Grant Date Fair Value of Awards Granted During the Period	$ 53.19	$ 40.85	$ 49.87
Unrecognized compensation cost	$ 0

Stock-Based Compensation Pla163

Stock-Based Compensation Plans (Summary Of Performance Unit Awards) (Detail) - Performance Shares - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued in period	103,843
Unrecognized compensation cost	$ 2
Weighted average recognition period, in years	1 year 26 days
Number of Shares
Outstanding, beginning balance	6,255,178
Granted	2,584,750
Exercised	(1,854,728)
Canceled	(133,658)
Outstanding, ending balance	6,851,542	6,255,178
Weighted Average Grant Date Fair Value
Outstanding, beginning balance (in USD per share)	$ 0.78
Granted (in USD per share)	0.92	$ 0.57	$ 0.95
Exercised (in USD per share)	0.85
Canceled (in USD per share)	0.82
Outstanding, ending balance (in USD per share)	$ 0.81	$ 0.78

Stock-Based Compensation Pla164

Stock-Based Compensation Plans (Weighted Average Assumptions Used to Value Performance Unit Awards) (Details) - Performance Shares - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.50%	1.00%	1.00%
Look-back period (in years)	2 years 9 months 30 days	2 years 9 months 30 days	2 years 10 months 3 days
Expected volatility	36.10%	34.20%	30.40%
Grant date fair value of performance units granted	$ 0.92	$ 0.57	$ 0.95

Stock-Based Compensation Pla165

Stock-Based Compensation Plans (MPLX Awards) (Details) - MPLX 2012 Incentive Compensation Plan [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	$ 18	$ 10	$ 4
MarkWest
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense			$ 15

Leases (Schedule Of Future Mini

Leases (Schedule Of Future Minimum Commitments) (Detail) $ in Millions	Dec. 31, 2017USD ($)
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2,018	$ 50
2,019	49
2,020	54
2,021	49
2,022	49
Later years	265
Total minimum lease payments	516
Less imputed interest costs	(152)
Present value of net minimum lease payments	364
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2,018	255
2,019	224
2,020	205
2,021	177
2,022	152
Later years	463
Total minimum lease payments	$ 1,476

Leases (Schedule Of Operating L

Leases (Schedule Of Operating Lease Rental Expense) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Leases [Abstract]
Rental expense	$ 301	$ 327	$ 331

Leases (Narrative) (Details)

Leases (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Leases [Abstract]
Operating lease revenue	$ 218	$ 246	$ 16
Contingent lease payments received	$ 9	$ 7

Leases (Minimum Future Rentals

Leases (Minimum Future Rentals On The Non-Cancellable Operating Leases) (Details) $ in Millions	Dec. 31, 2017USD ($)
Leases [Abstract]
2,018	$ 194
2,019	194
2,020	193
2,021	181
2,022	172
Later years	320
Total minimum lease payments	$ 1,254

Leases (Investments In Assets H

Leases (Investments In Assets Held For Operating Lease By Major Classes) (Details) $ in Millions	Dec. 31, 2017USD ($)
Operating Leased Assets [Line Items]
Property, plant and equipment, gross	$ 1,429
Less accumulated depreciation	153
Property, plant and equipment, net	1,276
Natural gas gathering and NGL transportation pipelines and facilities
Operating Leased Assets [Line Items]
Property, plant and equipment, gross	735
Natural gas processing facilities
Operating Leased Assets [Line Items]
Property, plant and equipment, gross	644
Construction in progress
Operating Leased Assets [Line Items]
Property, plant and equipment, gross	$ 50

Commitments and Contingencies (

Commitments and Contingencies (Detail)	12 Months Ended
	Dec. 31, 2017
Pending Litigation
Loss Contingencies [Line Items]
Loss contingency, inestimable loss	For matters for which we have not recorded an accrued liability, we are unable to estimate a range of possible loss because the issues involved have not been fully developed through pleadings and discovery.

Commitments and Contingencie172

Commitments and Contingencies (Environmental Matters) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Accrued liabilities for remediation	$ 114	$ 132
Receivables for recoverable costs	$ 45	$ 58

Commitments and Contingencie173

Commitments and Contingencies (MarkWest Environmental Proceedings) (Details) - MarkWest Liberty Midstream Pipeline Launcher/Receiver Site [Member] - Pending Litigation $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Cash
Loss Contingencies [Line Items]
Proposed settlement	$ 0.6
Other Liabilities
Loss Contingencies [Line Items]
Proposed settlement	$ 2.4

Commitments and Contingencie174

Commitments and Contingencies (Lawsuits) (Details) - Pending Litigation $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Construction Work at MarkWest Processing and Fractionation Complexes
Loss Contingencies [Line Items]
Plaintiff	Bilfinger Westcon, Inc
Emergency Pricing And Consumer Protection Laws
Loss Contingencies [Line Items]
Plaintiff	Commonwealth of Kentucky
Damages sought	$ 89
Loss contingency, period of occurrence	during September and October 2005
Minimum | Construction Work at MarkWest Processing and Fractionation Complexes
Loss Contingencies [Line Items]
Damages sought	$ 40
MPLX LP | Minimum | Construction Work at MarkWest Processing and Fractionation Complexes
Loss Contingencies [Line Items]
Damages sought	$ 10

Commitments and Contingencie175

Commitments and Contingencies (Guarantees) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	May 31, 2016	Sep. 30, 2015
Centennial
Loss Contingencies [Line Items]
Equity method investments, ownership percentage	50.00%
Crowley Ocean Partners
Loss Contingencies [Line Items]
Equity method investments, ownership percentage	50.00%	50.00%	50.00%
Crowley Blue Water Partners
Loss Contingencies [Line Items]
Equity method investments, ownership percentage	50.00%
Financial Guarantee | Centennial
Loss Contingencies [Line Items]
Maximum potential undiscounted payments	$ 25
Financial Guarantee | Master Shelf Agreement | Centennial
Loss Contingencies [Line Items]
Line of credit facility, expiration date	Dec. 31, 2024
Financial Guarantee | Guarantee of Indebtedness of Others | LOOP and LOCAP LLC
Loss Contingencies [Line Items]
Line of credit facility, expiration date	Dec. 31, 2037
Financial Guarantee | Guarantee of Indebtedness of Others | Crowley Ocean Partners | Crowley Term Loan [Member]
Loss Contingencies [Line Items]
Line of credit facility, maximum borrowing capacity	$ 325
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
Guarantee of Indebtedness of Others | Financial Guarantee | LOOP and LOCAP LLC
Loss Contingencies [Line Items]
Maximum potential undiscounted payments	160
Guarantee of Indebtedness of Others | Financial Guarantee | Crowley Ocean Partners
Loss Contingencies [Line Items]
Maximum potential undiscounted payments	163
Guarantee of Indebtedness of Others | Financial Guarantee | Crowley Blue Water Partners
Loss Contingencies [Line Items]
Maximum potential undiscounted payments	$ 135

Commitments and Contingences (C

Commitments and Contingences (Contractual Commitments and Contingencies) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Contractual commitments to acquire property, plant and equipment and advance funds to equity method investees	$ 484	$ 487
Galveston Bay Refinery and Related Assets
Loss Contingencies [Line Items]
Contractual commitments to acquire property, plant and equipment and advance funds to equity method investees		$ 131

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) shares in Millions, $ in Millions	Mar. 15, 2018	Feb. 08, 2018	Feb. 01, 2018	Sep. 01, 2017	Mar. 01, 2017	Sep. 01, 2016	Mar. 31, 2016
MPLX LP | Limited Partner
Subsequent Event [Line Items]
Units issued, number of units				19	13	7	23
MPLX LP | Cash and cash equivalents
Subsequent Event [Line Items]
Cash payment for acquisition				$ 420	$ 1,500
Subsequent Event | Senior notes, 2.700% due December 2018
Subsequent Event [Line Items]
Repayments of long-term debt	$ 600
Make whole premium	$ 3
Make whole premium, percentage of debt	0.50%
Subsequent Event | MPLX LP
Subsequent Event [Line Items]
MPC's partnership interest in MPLX (in percentage)			64.00%
Subsequent Event | MPLX LP | Senior Notes
Subsequent Event [Line Items]
Long-term debt, gross		$ 5,500
Subsequent Event | MPLX LP | MPLX 364-day term loan
Subsequent Event [Line Items]
Line of credit facility, maximum borrowing capacity			$ 4,100
Debt instrument, term			364 days
Repayments of short-term debt		4,100
Subsequent Event | MPLX LP | Senior notes, 3.375 % due March 2023 | Senior Notes
Subsequent Event [Line Items]
Long-term debt, gross		$ 500
Debt instrument, interest rate		3.375%
Subsequent Event | MPLX LP | Senior notes, 4.000% due March 2028 | Senior Notes
Subsequent Event [Line Items]
Long-term debt, gross		$ 1,250
Debt instrument, interest rate		4.00%
Subsequent Event | MPLX LP | Senior notes, 4.500% due April 2038 | Senior Notes
Subsequent Event [Line Items]
Long-term debt, gross		$ 1,750
Debt instrument, interest rate		4.50%
Subsequent Event | MPLX LP | Senior notes, 4.700% due April 2048 | Senior Notes
Subsequent Event [Line Items]
Long-term debt, gross		$ 1,500
Debt instrument, interest rate		4.70%
Subsequent Event | MPLX LP | Senior notes, 4.900% due April 2058 | Senior Notes
Subsequent Event [Line Items]
Long-term debt, gross		$ 500
Debt instrument, interest rate		4.90%
Subsequent Event | MPLX LP | Limited Partner
Subsequent Event [Line Items]
Units issued, number of units			114
Conversion of stock, shares issued			275
Subsequent Event | MPLX LP | Cash and cash equivalents
Subsequent Event [Line Items]
Cash payment for acquisition			$ 4,100

Selected Quarterly Financial178

Selected Quarterly Financial Data (Schedule Of Quarterly Financial Information) (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Data [Abstract]
Revenues	$ 21,055		$ 19,210	$ 18,180	$ 16,288	$ 17,155	$ 16,618	$ 16,811	$ 12,755
Income from operations	1,119		1,576	982	292	553	435	1,315	75	$ 3,969	$ 2,378	$ 4,692
Net income	2,125	[1]	1,004	574	101	289	219	783	(78)	3,804	1,213	2,868
Net income attributable to MPC	$ 2,016	[1]	$ 903	$ 483	$ 30	$ 227	$ 145	$ 801	$ 1	$ 3,432	$ 1,174	$ 2,852
Net income attributable to MPC per share:
Basic (in USD per share)	$ 4.13		$ 1.79	$ 0.94	$ 0.06	$ 0.43	$ 0.28	$ 1.51	$ 0.003	$ 6.76	$ 2.22	$ 5.29
Diluted (in USD per share)	4.09		1.77	0.93	0.06	0.43	0.27	1.51	0.003	6.70	2.21	5.26
Dividends paid per share (in USD per share)	$ 0.40		$ 0.40	$ 0.36	$ 0.36	$ 0.36	$ 0.36	$ 0.32	$ 0.32	$ 1.52	$ 1.36	$ 1.14
Change in enacted tax rate, amount										$ 1,500
[1]	During the fourth quarter of 2017, we recorded a tax benefit of approximately $1.5 billion as a result of remeasuring certain deferred tax liabilities using the lower corporate tax rate enacted under the TCJA.

Supplementary Statistics (Suppl

Supplementary Statistics (Supplementary Statistics) (Detail) - USD ($) $ in Millions		Mar. 01, 2017	Feb. 15, 2017	Dec. 04, 2015	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Supplementary Statistics [Line Items]
Income from operations					$ 1,119	$ 1,576	$ 982	$ 292	$ 553	$ 435	$ 1,315	$ 75	$ 3,969		$ 2,378		$ 4,692
Segment capital expenditures and investments													3,856		3,069		16,283
Inventory market valuation adjustment													0		(370)		370
MarkWest
Supplementary Statistics [Line Items]
Segment capital expenditures and investments				$ 13,850
MarEn Bakken Company LLC
Supplementary Statistics [Line Items]
Investments in equity method investments			$ 500										500
Refining & Marketing
Supplementary Statistics [Line Items]
Inventory market valuation adjustment	[1]														(345)		345
Speedway
Supplementary Statistics [Line Items]
Inventory market valuation adjustment	[1]														(25)		25
Midstream | Ozark Pipeline
Supplementary Statistics [Line Items]
Segment capital expenditures and investments		$ 220											220
Operating Segments
Supplementary Statistics [Line Items]
Income from operations													4,392		3,139		5,133
Segment capital expenditures and investments													3,718		2,925		16,091
Investments in equity method investments	[2]												805		431		2,788
Operating Segments | Refining & Marketing
Supplementary Statistics [Line Items]
Income from operations	[3]												2,321		1,357	[4]	3,997	[4]
Segment capital expenditures and investments	[3],[5]												832		1,054		1,045
Operating Segments | Speedway
Supplementary Statistics [Line Items]
Income from operations													732		734	[4]	673	[4]
Segment capital expenditures and investments	[5]												381		303		501
Operating Segments | Midstream
Supplementary Statistics [Line Items]
Income from operations	[3]												1,339		1,048		463	[6]
Segment capital expenditures and investments	[3],[5]												2,505	[7]	1,568		14,545	[8]
Corporate and Other
Supplementary Statistics [Line Items]
Income from operations	[3],[9]												(365)		(268)		(293)
Segment capital expenditures and investments	[5],[10]												138		144		192
Capitalized interest													55		63		37
Segment Reconciling Items
Supplementary Statistics [Line Items]
Pension settlement expenses	[11]												(52)		(7)		(4)
Litigation													(29)		0		0
Impairment	[1]												$ 23		$ (486)		$ (144)
[1]	2017 includes MPC’s share of gains related to the sale of assets remaining from the Sandpiper pipeline project. 2016 includes impairments of goodwill and equity method investments. 2015 relates to the cancellation of the ROUX project at our Garyville refinery. See Notes 16 and 17.
[2]	2017 includes an investment of $500 million in MarEn Bakken related to the Bakken Pipeline system. 2016 includes an adjustment of $143 million to the fair value of equity method investments acquired in connection with the MarkWest Merger. 2015 includes $2.46 billion related to the MarkWest Merger. See Note 5
[3]	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.
[4]	In 2016, the Refining & Marketing and Speedway segments include an inventory LCM benefit of $345 million and $25 million, respectively. In 2015, the Refining & Marketing and Speedway segments include an inventory LCM charge of $345 million and $25 million, respectively.
[5]	Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates
[6]	Included in the Midstream segment for 2015 are $36 million of transaction costs related to the MarkWest Merger.
[7]	In 2017, 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. See Note 5.
[8]	The Midstream segment includes $13.85 billion for the MarkWest Merger.
[9]	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.
[10]	Includes capitalized interest of $55 million, $63 million and $37 million for 2017, 2016 and 2015, respectively.
[11]	See Note 22 for further information.

Supplementary Statistics (Opera

Supplementary Statistics (Operating Statistics) (Detail) bbl / d in Thousands, gal in Millions, CFPD in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2017USD ($)Storebbl / dCFPD$ / bbl$ / galgal		Dec. 31, 2016USD ($)Storebbl / dCFPD$ / bbl$ / galgal		Dec. 31, 2015USD ($)Storebbl / dCFPD$ / bbl$ / galgal
Operating Statistics [Line Items ]
MPC Consolidated Refined Product Sales Volumes (thousands of barrels per day)	[1]	2,311		2,269		2,301
Refining & Marketing
Refining & Marketing Operating Statistics
Refining & Marketing refined product sales volume (thousands of barrels per day)	[2]	2,301		2,259		2,289
Refining & Marketing gross margin (dollars per barrel) | $ / bbl	[3]	12.60		11.16		15.16
Crude oil capacity utilization percent	[4]	97.00%		95.00%		99.00%
Refinery throughputs (thousands of barrels per day)	[5]	1,944		1,850		1,888
Inter-refinery transfers		78		83		46
Sour crude oil throughput percent		59.00%		60.00%		55.00%
WTI-priced crude oil throughput percent		21.00%		19.00%		20.00%
Refined product yields (thousands of barrels per day)	[5]	1,986		1,883		1,919
Refinery direct operating costs (dollars per barrel):
Planned turnaround and major maintenance | $ / bbl	[6]	1.72		1.83		1.13
Depreciation and amortization | $ / bbl	[6]	1.43		1.47		1.39
Other manufacturing | $ / bbl	[6],[7]	4.07		4.09		4.15
Total | $ / bbl	[6]	7.22		7.39		6.67
Refining & Marketing | Crude oil refined
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[5]	1,765		1,699		1,711
Refining & Marketing | Other charge and blendstocks
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[5]	179		151		177
Refining & Marketing | Gasoline
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	932		900		913
Refining & Marketing | Distillates
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	641		617		603
Refining & Marketing | Propane
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	36		35		36
Refining & Marketing | Feedstocks and special products
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	277		241		281
Refining & Marketing | Heavy fuel oil
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	37		32		31
Refining & Marketing | Asphalt
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[5]	63		58		55
Refining & Marketing | Gulf Coast:
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	1,294		1,234		1,244
Sour crude oil throughput percent		71.00%		73.00%		68.00%
WTI-priced crude oil throughput percent		11.00%		8.00%		6.00%
Refined product yields (thousands of barrels per day)	[8]	1,330		1,261		1,269
Refinery direct operating costs (dollars per barrel):
Planned turnaround and major maintenance | $ / bbl	[6]	1.75		2.09		0.81
Depreciation and amortization | $ / bbl	[6]	1.12		1.14		1.09
Other manufacturing | $ / bbl	[6],[7]	3.74		3.70		3.88
Total | $ / bbl	[6]	6.61		6.93		5.78
Refining & Marketing | Gulf Coast: | Crude oil refined
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	1,070		1,039		1,060
Refining & Marketing | Gulf Coast: | Other charge and blendstocks
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	224		195		184
Refining & Marketing | Gulf Coast: | Gasoline
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	546		514		534
Refining & Marketing | Gulf Coast: | Distillates
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	405		399		392
Refining & Marketing | Gulf Coast: | Propane
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	26		26		26
Refining & Marketing | Gulf Coast: | Feedstocks and special products
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	311		286		286
Refining & Marketing | Gulf Coast: | Heavy fuel oil
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	25		21		15
Refining & Marketing | Gulf Coast: | Asphalt
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	17		15		16
Refining & Marketing | Midwest:
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	728		699		690
Sour crude oil throughput percent		40.00%		40.00%		34.00%
WTI-priced crude oil throughput percent		37.00%		38.00%		43.00%
Refined product yields (thousands of barrels per day)	[8]	734		705		696
Refinery direct operating costs (dollars per barrel):
Planned turnaround and major maintenance | $ / bbl	[6]	1.48		1.15		1.64
Depreciation and amortization | $ / bbl	[6]	1.81		1.88		1.83
Other manufacturing | $ / bbl	[6],[7]	4.26		4.29		4.36
Total | $ / bbl	[6]	7.55		7.32		7.83
Refining & Marketing | Midwest: | Crude oil refined
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	695		660		651
Refining & Marketing | Midwest: | Other charge and blendstocks
Refining & Marketing Operating Statistics
Refinery throughputs (thousands of barrels per day)	[8]	33		39		39
Refining & Marketing | Midwest: | Gasoline
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	386		386		379
Refining & Marketing | Midwest: | Distillates
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	236		218		211
Refining & Marketing | Midwest: | Propane
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	11		11		12
Refining & Marketing | Midwest: | Feedstocks and special products
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	42		35		38
Refining & Marketing | Midwest: | Heavy fuel oil
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	13		12		17
Refining & Marketing | Midwest: | Asphalt
Refining & Marketing Operating Statistics
Refined product yields (thousands of barrels per day)	[8]	46		43		39
Speedway
Speedway Operating Statistics(i)
Convenience stores at period-end | Store	[9]	2,744		2,733		2,766
Gasoline and distillate sales (millions of gallons) | gal	[9]	5,799		6,094		6,038
Gasoline and distillate gross margin (dollars per gallon) | $ / gal	[9],[10]	0.1738		0.1656		0.1823
Merchandise sales (in millions) | $	[9]	$ 4,893		$ 5,007		$ 4,879
Merchandise margin (in millions) | $	[9]	$ 1,402		$ 1,435		$ 1,368
Merchandise margin percent	[9]	28.70%		28.70%		28.00%
Same store gasoline sales volume (period over period) percentage	[9]	(1.30%)		(0.40%)		(0.30%)
Merchandise sales excluding cigarettes (period over period) percentage	[9],[11]	1.20%		3.20%		4.10%
Midstream
Midstream Operating Statistics
Crude oil throughput	[12]	3,377		2,948		2,829
Terminal Throughput		1,477	[13]	1,505	[13]	0
Gathering system throughput (million cubic feet per day) | CFPD	[14]	3,608		3,275		3,075
Natural gas processed (million cubic feet per day) | CFPD	[14]	6,460		5,761		5,468
C2 (ethane) and NGLs (natural gas liquids) fractionated (mbpd)	[14]	394		335		307
[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. Sales revenue less cost of refinery inputs and purchased products, divided by total refinery throughputs. Comparable prior period information for R&M margin has been recast in connection with the contribution of certain pipeline assets to MPLX on March 1, 2017.
[4]	Based on calendar day capacity, which is an annual average that includes downtime for planned maintenance and other normal operating activities
[5]	Excludes inter-refinery volumes of 78 mbpd, 83 mbpd and 46 mbpd for 2017, 2016 and 2015, respectively.
[6]	Per barrel of total refinery throughputs.
[7]	Includes utilities, labor, routine maintenance and other operating costs.
[8]	Includes inter-refinery transfer volumes.
[9]	2017 operating statistics do not reflect any information for the 41 travel centers contributed to PFJ Southeast, whereas they are reflected in prior years.
[10]	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.
[11]	Excludes cigarettes
[12]	Includes common-carrier pipelines and private pipelines contributed to MPLX, excluding equity method investments.
[13]	Includes the results of the terminal assets contributed to MPLX from the date the assets became a business, April 1, 2016.
[14]	Includes the results of the MarkWest assets beginning on the Dec. 4, 2015 acquisition date. Includes amounts related to unconsolidated equity method investments on a 100 percent basis.