Marathon Petroleum (MPC) 10-K 28 Feb 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2018	Feb. 15, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
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 Emerging Growth Company	false
Entity Shell Company	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		673,619,190
Entity Public Float			$ 31.9

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues and other income:
Sales and other operating revenues, excluding consumer excise taxes	[1],[2]	$ 95,750
Sales and other operating revenue, including excise taxes	[2]		$ 74,104	$ 63,277
Sales to related parties	[3]	754	629	62
Income (loss) from equity method investments		373	306	(185)
Net gain on disposal of assets		23	10	32
Other income		202	320	178
Total revenues and other income		97,102	75,369	63,364
Costs and expenses:
Cost of revenues (excludes items below)	[2]	85,456	66,519	56,676
Purchases from related parties	[4]	610	570	509
Inventory market valuation adjustment		0	0	(370)
Impairment expense		0	0	130
Depreciation and amortization		2,490	2,114	2,001
Selling, general and administrative expenses		2,418	1,694	1,597
Other taxes		557	454	435
Total costs and expenses		91,531	71,351	60,978
Income from operations		5,571	4,018	2,386
Net interest and other financial costs		1,003	674	564
Income before income taxes		4,568	3,344	1,822
(Benefit) provision for income taxes		962	(460)	609
Net income		3,606	3,804	1,213
Less net income (loss) attributable to:
Redeemable noncontrolling interest		75	65	41
Noncontrolling interests		751	307	(2)
Net income attributable to MPC		$ 2,780	$ 3,432	$ 1,174
Basic:
Net income attributable to MPC per share		$ 5.36	$ 6.76	$ 2.22
Weighted average shares outstanding (in shares)		518	507	528
Diluted:
Net income attributable to MPC per share		$ 5.28	$ 6.70	$ 2.21
Weighted average shares outstanding (in shares)		526	512	530
[1]	The 2018 period reflects an election to present certain taxes on a net basis concurrent with our adoption of ASC 606.
[2]	The 2018 period reflects an election to present certain taxes on a net basis concurrent with our adoption of ASU 2014-09, Revenue - Revenue from Contracts with Customers (“ASC 606”). See Notes 2 and 3 for further information.
[3]	Sales to related parties consists primarily of sales of refined products to PFJ Southeast, an equity affiliate which owns and operates travel plazas primarily in the Southeast region of the United States.
[4]	We obtain transportation services and purchase ethanol from certain of our equity affiliates, none of which is individually material.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 3,606	$ 3,804	$ 1,213
Defined benefit postretirement and post-employment plans:
Actuarial changes, net of tax of $14, $17 and $69, respectively	75	29	115
Prior service costs, net of tax of $12, ($16) and ($18), respectively	8	(26)	(31)
Other, net of tax of $1, $0 and $0, respectively	4	0	0
Other comprehensive income	87	3	84
Comprehensive income	3,693	3,807	1,297
Less comprehensive income (loss) attributable to:
Redeemable noncontrolling interest	75	65	41
Noncontrolling interests	751	307	(2)
Comprehensive income attributable to MPC	$ 2,867	$ 3,435	$ 1,258

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Actuarial changes, tax	$ 14	$ 17	$ 69
Prior service costs, tax	12	(16)	(18)
Other, tax	$ 1	$ 0	$ 0

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 1,687	$ 3,011
Receivables, less allowance for doubtful accounts of $9 and $11, respectively	5,853	4,695
Inventories	9,837	5,550
Other current assets	646	145
Total current assets	18,023	13,401
Equity method investments	5,898	4,787
Property, plant and equipment, net	45,058	26,443
Goodwill	20,184	3,586
Other noncurrent assets	3,777	830
Total assets	92,940	49,047
Current liabilities:
Accounts payable	9,366	8,297
Payroll and benefits payable	1,152	591
Accrued taxes	1,446	670
Debt due within one year	544	624
Other current liabilities	708	296
Total current liabilities	13,216	10,478
Long-term debt	26,980	12,322
Deferred income taxes	4,864	2,654
Defined benefit postretirement plan obligations	1,509	1,099
Deferred credits and other liabilities	1,318	666
Total liabilities	47,887	27,219
Commitments and contingencies (see Note 25)
Redeemable noncontrolling interest	1,004	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 – 975 million and 734 million shares (par value $0.01 per share, 2 billion shares authorized)	10	7
Held in treasury, at cost – 295 million and 248 million shares	(13,175)	(9,869)
Additional paid-in capital	33,729	11,262
Retained earnings	14,755	12,864
Accumulated other comprehensive loss	(144)	(231)
Total MPC stockholders’ equity	35,175	14,033
Noncontrolling interests	8,874	6,795
Total equity	44,049	20,828
Total liabilities, redeemable noncontrolling interest and equity	$ 92,940	$ 49,047

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 9	$ 11
Preferred stock:
Shares issued	0	0
Shares outstanding	0	0
Par value	$ 0.01
Shares authorized	30,000,000
Common stock:
Shares issued	975,000,000	734,000,000
Par value	$ 0.01
Shares authorized	2,000,000,000
Treasury stock	(295,000,000)	(248,000,000)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Operating activities:
Net income	$ 3,606		$ 3,804		$ 1,213
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred financing costs and debt discount	70		64		61
Impairment expense	0		0		130
Depreciation and amortization	2,490		2,114		2,001
Inventory market valuation adjustment	0		0		(370)
Pension and other postretirement benefits, net	90		47		9
Deferred income taxes	47		(1,233)		394
Net gain on disposal of assets	(23)		(10)		(32)
(Income) loss from equity method investments	(373)		(306)		185
Distributions from equity method investments	519		391		317
Changes in the fair value of derivative instruments	(62)		116		(41)
Changes in operating assets and liabilities, net of effects of businesses acquired:
Current receivables	1,589		(1,093)		(674)
Inventories	931		106		(70)
Current accounts payable and accrued liabilities	(2,798)		2,814		985
All other, net	72		(202)		(91)
Net cash provided by operating activities	6,158		6,612		4,017
Investing activities:
Additions to property, plant and equipment	(3,578)		(2,732)		(2,892)
Acquisitions, net of cash acquired	(3,822)		(249)		0
Disposal of assets	54		79		101
Investments – acquisitions, loans and contributions	(409)		(805)		(288)
Investments—redemptions, repayments and return of capital	16		62		0
All other, net	69		247		112
Net cash used in investing activities	(7,670)		(3,398)		(2,967)
Financing activities:
Commercial paper – issued	0		300		1,263
Commercial paper - repayments	0		(300)		(1,263)
Long-term debt – borrowings	13,476		2,911		864
Long-term debt – repayments	(8,032)		(642)		(2,269)
Debt issuance costs	(86)		(33)		(11)
Issuance of common stock	24		46		11
Common stock repurchased	(3,287)		(2,372)		(197)
Dividends paid	(954)		(773)		(719)
Issuance of MPLX LP common units	0		473		776
Issuance of MPLX LP redeemable preferred units	0		0		984
Distributions to noncontrolling interests	(903)		(694)		(542)
Contributions from noncontrolling interests	12		129		6
Contingent consideration payment	0		(89)		(164)
All other, net	(28)		(47)		(33)
Net cash provided by (used in) financing activities	222		(1,091)		(1,294)
Net increase (decrease) in cash, cash equivalents and restricted cash	(1,290)		2,123		(244)
Cash, cash equivalents and restricted cash at beginning of period	3,015	[1]	892		1,136
Cash, cash equivalents and restricted cash at end of period	$ 1,725	[1]	$ 3,015	[1]	$ 892
[1]	As a result of the adoption of ASU 2016-18, the consolidated statements of cash flows now explain the change during the period of both cash and cash equivalents and restricted cash.

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Millions	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Non-controlling Interests
Beginning balance at Dec. 31, 2015	$ 19,675	$ 7	$ (7,275)	$ 11,071	$ 9,752	$ (318)	$ 6,438
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	1,172				1,174		(2)
Dividends declared on common stock	(720)				(720)
Distributions to noncontrolling interests	(517)						(517)
Contributions from noncontrolling interests	6						6
Other comprehensive income	84					84
Shares repurchased	(197)		(197)
Shares issued - stock based compensation				46
Shares returned - stock based compensation			(10)
Stock based compensation	42						6
Impact from equity transactions of MPLX & ANDX	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 on common stock	(774)				(774)
Distributions to noncontrolling interests	(629)						(629)
Contributions from noncontrolling interests	129						129
Other comprehensive income	3					3
Shares repurchased	(2,372)		(2,372)
Shares issued - stock based compensation				92
Shares returned - stock based compensation			(15)
Stock based compensation	85						8
Impact from equity transactions of MPLX & ANDX	444			110			334
Ending balance at Dec. 31, 2017	20,828	7	(9,869)	11,262	12,864	(231)	6,795
Cumulative effect of adopting new accounting standards	68				66		2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	3,531				2,780		751
Dividends declared on common stock	(955)				(955)
Distributions to noncontrolling interests	(832)						(832)
Contributions from noncontrolling interests	12						12
Other comprehensive income	87					87
Shares repurchased	(3,287)		(3,287)
Shares issued - stock based compensation		1		345
Shares returned - stock based compensation			(18)
Stock based compensation	342						14
Impact from equity transactions of MPLX & ANDX	(570)			2,357			(2,927)
Issuance of shares for Andeavor acquisition	19,766	2	(1)	19,765
Noncontrolling interest acquired from Andeavor	5,059						5,059
Ending balance at Dec. 31, 2018	$ 44,049	$ 10	$ (13,175)	$ 33,729	$ 14,755	$ (144)	$ 8,874

Consolidated Statements of Eq_2

Consolidated Statements of Equity - Shares of Common Stock - shares shares in Millions	Total	Common Stock
Beginning balance at Dec. 31, 2015		729
Shares issued - stock-based compensation		2
Ending balance at Dec. 31, 2016		731
Shares issued - stock-based compensation		3
Ending balance at Dec. 31, 2017	734	734
Shares issued - stock-based compensation		1
Shares issued - acquisitions		240
Ending balance at Dec. 31, 2018	975	975

Consolidated Statements of Eq_3

Consolidated Statements of Equity - Shares of Treasury Stock - shares shares in Millions	Total	Treasury Stock
Beginning balance at Dec. 31, 2015		(198)
Number of shares repurchased	(4)	(4)
Shares returned - stock-based compensation		(1)
Ending balance at Dec. 31, 2016		(203)
Number of shares repurchased	(44)	(44)
Shares returned - stock-based compensation		(1)
Ending balance at Dec. 31, 2017	(248)	(248)
Number of shares repurchased	(47)	(47)
Shares returned - stock-based compensation		0
Ending balance at Dec. 31, 2018	(295)	(295)

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interest - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Temporary Equity [Abstract]
Beginning balance	$ 1,000	$ 1,000	$ 0
Net income (loss) attributable to redeemable noncontrolling interest	75	65	41
Distributions to noncontrolling interests	(71)	(65)	(25)
Issuance of MPLX LP redeemable preferred units			984
Ending balance	$ 1,004	$ 1,000	$ 1,000

Consolidated Statements of Eq_4

Consolidated Statements of Equity and Redeemable Noncontrolling Interest (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Stockholders' Equity [Abstract]
Dividends declared per share of common stock (in dollars per share)	$ 1.84	$ 1.52	$ 1.36

Description Of The Business And

Description Of The Business And Basis Of Presentation	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of the Business and Basis of Presentation	DESCRIPTION OF THE BUSINESS AND BASIS OF PRESENTATION Description of the Business We are a leading, integrated, downstream energy company headquartered in Findlay, Ohio. We operate the nation's largest refining system with more than 3 million barrels per day of crude oil capacity across 16 refineries. MPC's marketing system includes branded locations across the United States, which primarily include Marathon branded outlets. We own and operate retail convenience stores across the United States. We also own the general partner and majority limited partner interests in two midstream companies, MPLX LP (“MPLX”) and Andeavor Logistics LP (“ANDX”), which own and operate crude oil and light product transportation and logistics infrastructure as well as gathering, processing, and fractionation assets. Refer to Note 5 for further information on the Andeavor acquisition, which closed on October 1, 2018, and to Note 10 for additional information about our operations. 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.

Summary Of Principal Accounting

Summary Of Principal Accounting Policies	12 Months Ended
	Dec. 31, 2018
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, MPLX and ANDX. 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, 2018 , we owned 63.6 percent of the outstanding MPLX common units and 63.6 percent of the outstanding ANDX common units and 100 percent of the general partner interest for each entity. Due to our ownership of the general partner interest, we have determined that we control MPLX and ANDX and therefore we consolidate MPLX and ANDX and record a noncontrolling interest for the 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 We recognize revenue based on consideration specified in contracts or agreements with customers when we satisfy our performance obligations by transferring control over products or services to a customer. Concurrent with our adoption of ASU 2014-09, Revenue from Contracts with Customers (“ASC 606”), we made an accounting policy election that all taxes assessed by a governmental authority that are both imposed on and concurrent with a revenue-producing transaction and collected from our customers will be recognized on a net basis within sales and other operating revenues. The adoption of ASC 606 did not materially change our revenue recognition patterns, which are described below by reportable segment: • Refining & Marketing - The vast majority of our Refining & Marketing contracts contain pricing that is based on the market price for the product at the time of delivery. Our obligations to deliver product volumes are typically satisfied and revenue is recognized when control of the product transfers to our customers. Concurrent with the transfer of control, we typically receive the right to payment for the delivered product, the customer accepts the product and the customer has significant risks and rewards of ownership of the product. Payment terms require customers to pay shortly after delivery and do not contain significant financing components. • Retail - Revenue is recognized when our customers receive control of the transportation fuels or merchandise. Payments from customers are received at the time sales occur in cash or by credit or debit card at our company-owned and operated retail locations and shortly after delivery for our direct dealers. Our retail operations offer a loyalty rewards program to its customers. We defer a minor portion of revenue on sales to the loyalty program participants until the participants redeem their rewards. The related contract liability, as defined in ASC 606, is not material to our financial statements. • Midstream - Midstream revenue transactions typically are defined by contracts under which we sell a product or provide a service. Revenues from sales of product are recognized when control of the product transfers to the customer. Revenues from sales of services are recognized over time when the performance obligation is satisfied as services are provided in a series. We have elected to use the output measure of progress to recognize revenue based on the units delivered, processed or transported. The transaction prices in our Midstream contracts often have both fixed components, related to minimum volume commitments, and variable components, which are primarily dependent on volumes. Variable consideration will generally not be estimated at contract inception as the transaction price is specifically allocable to the services provided at each period end. Refer to Note 10 for disclosure of our revenue disaggregated by segment and product line, as well as a description of our reportable segment operations. 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. No revenues are recorded for exchange and matching buy/sell transactions as they are accounted for as exchanges of inventory. The exchange transactions are recognized at the carrying amount of the inventory transferred. 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. 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. We mitigate credit risk with master netting agreements with 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 51 years. Such assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset group may not be recoverable. If the sum of the expected undiscounted future cash flows from the use of the asset group and its eventual disposition is less than the carrying amount of the asset group, an impairment assessment is performed and the excess of the book value over the fair value of the asset group 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. The fair value is calculated using the expected present value of future cash flows method. Significant assumptions used in the cash flow forecasts include future net operating margins, future volumes, discount rates, and future capital requirements. If the carrying amount of the reporting unit exceeds its fair value, an impairment loss shall be recognized in an amount equal to that excess, limited to the total amount of goodwill allocated to that reporting unit. 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 and other major maintenance 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 for additional equipment that mitigates or prevents future contamination or improves environmental safety or efficiency of the existing assets are capitalized. 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. Our short-term asset retirement obligations were $30 million and $6 million at December 31, 2018 and 2017 , respectively, which are included in other current liabilities in our consolidated balance sheets. Our long-term asset retirement obligations were $222 million and $121 million at December 31, 2018 and 2017 , respectively, which are included in deferred credits and other liabilities in our consolidated balance sheets. The increase in our asset retirement obligation was mainly due to obligations recognized in connection with the purchase accounting for the Andeavor acquisition. 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. Any excess or surplus of the purchase consideration when compared to the fair value of the net tangible assets acquired, if any, is 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. 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. 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 date, 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 that would have existed as of the date of the acquisition. Any adjustment that arises from information obtained that did not exist as of the date of the acquisition will be recorded in the period of the adjustment. Acquisition-related costs are expensed as incurred in connection with each business combination. Environmental Credits and Obligations In order to comply with certain regulations, specifically the RFS2 requirements implemented by the EPA and the cap-and-trade emission reduction program and low carbon fuel standard implemented by the state of California, we are required to reduce our emissions, blend certain levels of biofuels or obtain allowances or credits to offset the obligations created by our operations. In regard to each program, we record an asset, included in other current or other noncurrent assets on the balance sheet, for allowances or credits owned in excess of our anticipated current period compliance requirements. The asset value is based on the product of the excess allowances or credits as of the balance sheet date, if any, and the weighted average cost of those allowances or credits. We record a liability, included in other current or other noncurrent liabilities on the balance sheet, when we are deficient allowances or credits based on the product of the deficient amount as of the balance sheet date, if any, and the market price of the allowances or credits at the balance sheet date. The cost of allowances or credits used for compliance is reflected in cost of revenues on the income statement. Any gains or losses on the sale or expiration of allowances or credits are classified as other income on the income statement. Proceeds from offset or credits sales are included in investing activities - all other, net on the cash flow statement.

Accounting Standards

Accounting Standards	12 Months Ended
	Dec. 31, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recently Adopted Accounting Pronouncements	Recently Adopted ASU 2014-09, Revenue - Revenue from Contracts with Customers (ASC 606) On January 1, 2018, we adopted the new revenue standard, applying the modified retrospective method, whereby a cumulative effect is recorded to opening retained earnings and ASC 606 is applied prospectively. We recorded a net increase of $4 million to our retained earnings balance as of January 1, 2018 due to the cumulative effect of applying the new revenue standard. Impact of Adoption The adoption of ASC 606 did not materially change our revenue recognition patterns. The most significant impacts of adopting ASC 606 for the period ended December 31, 2018 are as follows: • a reduction of sales and other operating revenues of $6.66 billion for the year ended December 31, 2018 due to our accounting policy election to present taxes incurred concurrently with revenue producing transactions and collected on behalf of our customers on a net basis. For the year ended December 31, 2017 , taxes are reflected on a gross basis in sales and other operating revenues and cost of revenues, and include $5.15 billion of taxes that are now subject to our net basis accounting policy election. • an increase to both sales and other operating revenues and cost of revenues of $502 million for the year ended December 31, 2018 related to certain Midstream contract provisions for third-party reimbursements, non-cash consideration and imbalances that require gross presentation under ASC 606. Comparative information continues to be reported under the accounting standards in effect for those periods. Practical Expedients We elected the completed contract practical expedient and only applied ASC 606 to contracts that were not completed as of January 1, 2018. We do not disclose information on the future performance obligations for any contract with expected duration of one year or less at inception. As of December 31, 2018 , we do not have future performance obligations that are material to future periods. Receivables On the accompanying consolidated balance sheets, receivables, less allowance for doubtful accounts primarily consists of customer receivables. Significant, non-customer balances included in our receivables at December 31, 2018 include matching buy/sell receivables of $1.64 billion and income taxes receivables of $88 million . ASU 2016-16, Income Taxes - Intra-Entity Transfers of Assets Other Than Inventory We adopted this ASU in the first quarter of 2018 and recorded a $62 million cumulative-effect adjustment as an increase to retained earnings as of January 1, 2018 with the offset recorded as a reduction to deferred income taxes. We also adopted the following ASUs during 2018, none of which had a material impact to our financial statements or financial statement disclosures: ASU Effective Date 2017-09 Stock Compensation - Scope of Modification Accounting January 1, 2018 2017-07 Retirement Benefits - Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Cost January 1, 2018 2017-05 Gains and Losses from the Derecognition of Nonfinancial Assets - Clarifying the Scope of Asset Derecognition Guidance January 1, 2018 2017-01 Business Combinations - Clarifying the Definition of a Business January 1, 2018 2016-18 Statement of Cash Flows - Restricted Cash January 1, 2018 2016-15 Statement of Cash Flows - Classification of Certain Cash Receipts and Cash Payments January 1, 2018 2016-01 Financial Instruments - Recognition and Measurement of Financial Assets and Liabilities January 1, 2018
Not Yet Adopted Accounting Pronouncements	Not Yet Adopted ASU 2018-02, Reporting Comprehensive Income - Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income In February 2018, the FASB issued an ASU allowing an entity the choice to reclassify to retained earnings the tax effects related to the TCJA that are stranded in accumulated other comprehensive income. The amendment was effective January 1, 2019. We do not expect the application of this accounting standard update to have a material impact on our consolidated financial statements. ASU 2017-12, Derivatives and Hedging - Targeted Improvements to Accounting for Hedging Activities In August 2017, the FASB issued an ASU 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 and eases certain hedge effectiveness assessment requirements. The guidance was effective January 1, 2019. We do not expect the application of this accounting standard update to have a material impact on our consolidated financial statements. ASU 2017-04, Intangibles - Goodwill and Other - Simplifying the Test for Goodwill Impairment In January 2017, the FASB issued an ASU which simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test. Under the new guidance, the recognition of an impairment charge is calculated based on the amount by which the carrying amount exceeds the reporting unit’s fair value, which could be different from the amount calculated under the current method using the implied fair value of the goodwill; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. The guidance should be applied on a prospective basis, and is effective for annual or any interim goodwill impairment tests in fiscal years beginning after December 15, 2019. ASU 2016-13, Credit Losses - Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued an ASU 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 ASU to have a material impact on our consolidated financial statements. ASU 2016-02 Leases and related updates In February 2016, the FASB issued an ASU requiring lessees to record virtually all leases on their balance sheets. The ASU 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 guidance will be effective for fiscal years beginning after December 15, 2018, and interim periods within those years. As of January 1, 2019, we have transitioned to the new guidance. As part of implementing this standard, we evaluated the impact of this standard on our financial statements, disclosures, internal controls and accounting policies. This evaluation process included reviewing all forms of leases, performing a completeness assessment over the lease population and analyzing the practical expedients in order to determine the best path of implementing changes to existing processes and controls. We have implemented a third-party supported lease accounting information system to account for our lease population in accordance with this new standard and established internal controls over the new system. We expect that adoption of the standard will result in the recognition of right-of-use assets and lease liabilities for operating leases on January 1, 2019 in the range of $2.5 billion to $3.0 billion . The adoption of ASC 842 will not have a material impact on our consolidated statements of income or cash flows, except for the potential effects from lease modifications where MPLX is the lessor as discussed below. In addition, based on the changes presented in the standard, MPLX, as a lessor, may be required to re-classify existing operating leases to sales-type leases upon modification and related reassessment of the leases. If such modification were to occur, it may result in a de-recognition of existing assets, recognition of a receivable in the amount of the present value of fixed payments expected to be received by MPLX under the lease, and recognition of a corresponding gain or loss in the period of change.

Master Limited Partnerships

Master Limited Partnerships	12 Months Ended
	Dec. 31, 2018
Noncontrolling Interest [Abstract]
Master Limited Partnerships	MASTER LIMITED PARTNERSHIPS MPLX MPLX is a diversified, large-cap publicly traded master limited partnership formed by us to own, operate, develop and acquire midstream energy infrastructure assets. MPLX is engaged in the transportation, storage and distribution of crude oil and refined petroleum products; gathering, processing and transportation of natural gas; and the gathering, transportation, fractionation, storage and marketing of NGLs.As of December 31, 2018 , we owned 63.6 percent of the outstanding MPLX common units and we control MPLX through our ownership of the general partner of MPLX. 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 were 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 received cumulative quarterly distributions equal to $0.528125 per unit for the quarters prior to the second quarter of 2018. Beginning with the second quarter of 2018, the holders of the MPLX Preferred Units are entitled to receive a quarterly distribution equal to the greater of $0.528125 per unit or the amount of distributions they would have received on an as converted basis. For the income earned in the second through fourth quarters of 2018, the distribution rate declared to MPLX common unitholders was greater than $0.528125 per unit; accordingly, the holders of the MPLX Preferred Units received the common unit rates in lieu of the lower $0.528125 base amount. 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 and GP/IDR Exchange On February 1, 2018, we contributed our refining logistics assets and fuels distribution services to MPLX in exchange for $4.1 billion in cash and approximately 112 million common units and 2 million general partner units from MPLX. MPLX financed the cash portion of the transaction with its $4.1 billion 364 -day term loan facility, which was entered into on January 2, 2018. We agreed to waive approximately one-third of the first quarter 2018 distributions on the common units issued in connection with this transaction. The contributions of these assets were accounted for as transactions between entities under common control and we did not record a gain or loss. Immediately following the February 1, 2018 dropdown to MPLX, our IDRs were cancelled and our economic general partner interest was converted into a non-economic general partner interest, all in exchange for 275 million newly issued MPLX common units (“GP/IDR Exchange”). As a result of this transaction, the general partner units and IDRs were eliminated, are no longer outstanding and longer participate in distributions of cash from MPLX. On September 1, 2017, we contributed our joint-interest ownership in certain pipelines and storage facilities to MPLX in exchange for $420 million in cash and approximately 19 million MPLX common units and 378 thousand general partner units from MPLX. We also agreed to waive approximately two-thirds of the third quarter 2017 common unit distributions, IDRs and general partner distributions with respect to the common units issued in this transaction. The contributions of these assets were accounted for as transactions between entities under common control and we did not record a gain or loss. On March 1, 2017, we contributed certain terminal, pipeline and storage assets to MPLX in exchange total consideration of $1.5 billion in cash and approximately 13 million common units and 264 thousand general partner units from MPLX. We also agreed to waive two-thirds of the first quarter 2017 common unit distributions, IDRs and general partner distributions with respect to the common units issued in 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. 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. Agreements We have various long-term, fee-based commercial agreements with MPLX. Under these agreements, MPLX provides transportation, storage, distribution and marketing services to us. Under certain agreements, we commit to provide MPLX with minimum quarterly throughput and distribution volumes of crude oil and refined products and minimum storage volumes of crude oil, refined products and butane. Under certain other agreements, we commit to pay for 100 percent of available capacity for certain marine transportation and refining logistics assets. We also have agreements with MPLX that establish fees for operational and management services provided between us and MPLX and for executive management services and certain general and administrative services provided by us to MPLX. These transactions are eliminated in consolidation, but are reflected as intersegment transactions between our Refining & Marketing and Midstream segments. ANDX Through the Andeavor acquisition, we acquired control of ANDX, which is a publicly traded limited partnership that was formed to own, operate, develop and acquire logistics assets. Its assets are integral to the success of our refining and marketing operations and are used to gather crude oil, natural gas, and water, process natural gas and distribute, transport and store crude oil and refined products. ANDX provides us with various pipeline transportation, trucking, terminal distribution, storage and petroleum-coke handling services under long-term, fee-based commercial agreements. Each of these agreements, with the exception of the storage and transportation services agreement, contain minimum volume commitments. As of December 31, 2018 , we owned 63.6 percent of the outstanding ANDX common units. We also hold 80,000 ANDX TexNew Mex Units and all the outstanding non-economic general partner interests as of December 31, 2018 . Noncontrolling Interest As a result of equity transactions of MPLX and ANDX, we are required to adjust non-controlling interest and additional paid-in capital. Changes in MPC’s additional paid-in capital resulting from changes in its ownership interest in MPLX and ANDX were as follows: (In millions) 2018 2017 2016 Increase (decrease) due to the issuance of MPLX & ANDX common units to the public $ 6 $ 25 $ (60 ) Increase due to the issuance of MPLX & ANDX common units and general partner units to MPC 1,114 114 121 Increase due to GP/IDR Exchange 1,808 — — Increase in MPC's additional paid-in capital 2,928 139 61 Tax impact (571 ) (29 ) (118 ) Increase (decrease) in MPC's additional paid-in capital, net of tax $ 2,357 $ 110 $ (57 )

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Acquisitions	ACQUISITIONS Acquisition of Andeavor On October 1, 2018, we acquired all the outstanding shares of Andeavor. Under the terms of the merger agreement, Andeavor stockholders had the option to choose 1.87 shares of MPC common stock or $152.27 in cash per share of Andeavor common stock. The merger agreement included election proration provisions that resulted in approximately 22.9 million shares of Andeavor common stock being converted into cash consideration and the remaining 128.2 million shares of Andeavor common stock being converted into stock consideration. Andeavor stockholders received in the aggregate approximately 239.8 million shares of MPC common stock valued at $19.8 billion and approximately $3.5 billion in cash in connection with the Andeavor acquisition. The fair value of the MPC shares issued was determined on the basis of the closing market price of MPC’s common shares on the acquisition date. The cash portion of the purchase price was funded using cash on hand. At the time of the acquisition, all Andeavor equity awards, with the exception of non-employee director units, were converted to MPC equity awards. The converted equity awards will continue to be governed by the same terms and conditions as were applicable to such Andeavor equity awards immediately prior to the acquisition. We recognized $203 million of purchase consideration to reflect the portion of the fair value of the time-based converted equity awards attributable to pre-combination service completed by the award holders. The non-employee director units were accelerated in full and cancelled and the holders of such units received an amount of cash equal to the number of shares of Andeavor common stock subject to such non-employee director units multiplied by the cash consideration per share. Our financial reflect the results of Andeavor from October 1, 2018, the date of the acquisition. The components of the fair value of consideration transferred are as follows: (In millions) Fair value of MPC shares issued $ 19,766 Cash payment to Andeavor stockholders 3,486 Cash settlement of non-employee director units 7 Fair value of converted equity awards 203 Total fair value of consideration transferred $ 23,462 We accounted for the Andeavor acquisition using the acquisition method of accounting, which requires Andeavor assets and liabilities to be recorded to our balance sheet at fair value as of the acquisition date. We will complete a final determination of the fair value of certain assets and liabilities within the one year measurement period from the date of the acquisition as required by FASB ASC Topic 805, “Business Combinations”. Due to the level of effort required to develop fair value measurements and the proximity of the acquisition date to December 31, 2018, the valuation studies necessary to determine the fair value of assets acquired and liabilities assumed are preliminary, including the underlying cash flows used to determine the fair value of identified intangible assets and economic obsolescence adjustments to property, plant and equipment. The size and the breath of the Andeavor acquisition necessitates the use of the one year measurement period to fully analyze all the factors used in establishing the asset and liability fair values as of the acquisition date, including, but not limited to, property, plant and equipment, intangible assets, real property, leases, environmental and asset retirement obligations and the related tax impacts of any changes made. Any potential adjustments made could be material in relation to the preliminary values presented below. (In millions) Cash and cash equivalents $ 382 Receivables 2,744 Inventories 5,204 Other current assets 378 Equity method investments 865 Property, plant and equipment, net 16,545 Other noncurrent assets (a) 3,086 Total assets acquired 29,204 Accounts payable 4,003 Payroll and benefits payable 348 Accrued taxes 590 Debt due within one year 34 Other current liabilities 392 Long-term debt 8,875 Deferred income taxes 1,609 Defined benefit postretirement plan obligations 432 Deferred credit and other liabilities 714 Noncontrolling interests 5,059 Total liabilities and noncontrolling interest assumed 22,056 Net assets acquired excluding goodwill 7,148 Goodwill 16,314 Net assets acquired $ 23,462 (a) Includes intangible assets. Details of our valuation methodology and significant inputs for fair value measurements are included by asset class below. The fair value measurements for equity method investments, property, plant and equipment, intangible assets and long-term debt are based on significant inputs that are not observable in the market and, therefore, represent Level 3 measurements. Goodwill The preliminary purchase consideration allocation resulted in the recognition of $16.3 billion in goodwill, of which $893 million is tax deductible due to a carryover basis from Andeavor. Our Refining & Marketing, Midstream and Retail segments recognized $4.7 billion , $7.7 billion and $3.9 billion of preliminary goodwill. The recognized goodwill represents the value expected to be created by further optimization of crude supply, a nationwide retail and marketing platform, diversification of our refining and midstream footprints and optimization of information systems and business processes. Inventory The fair value of inventory was determined by recognizing crude oil and feedstocks at market prices as of October 1, 2018 and recognizing refined product inventory at market prices less selling costs and profit margin associated with the remaining distribution process. Equity Method Investments The fair value of the equity method investments was determined based on applying income and market approaches. The income approach relied on the discounted cash flow method and the market approach relied on a market multiple approach considering historical and projected financial results. Discount rates for the discounted cash flow models were based on capital structures for similar market participants and included various risk premiums that account for risks associated with the specific investments. For more information about our equity method investments, see Note 14 . Property, Plant and Equipment The preliminary fair value of property, plant and equipment is $16.5 billion , which is based primarily on the cost approach. Key assumptions in the cost approach include determining the replacement cost by evaluating recent purchases of similar assets or published data, and adjusting replacement cost for economic and functional obsolescence, location, normal useful lives, and capacity (if applicable). Acquired Intangible Assets The preliminary fair value of the acquired identifiable intangible assets is $2.8 billion , which represents the value of various customer contracts and relationships, brand rights and tradenames and other intangible assets. The preliminary fair value of customer contracts and relationships is $2.5 billion , which was valued by applying the multi-period excess earnings method, which is an income approach. Key assumptions in the income approach include the underlying contract cash flow estimates, remaining contract term, probability of renewal, growth rates and discount rates. Brand rights and tradenames were valued by applying the relief of royalty method, which is an income approach. The intangible assets are all finite lived and will be amortized over 2 to 10 years. Debt The fair value of the Andeavor and ANDX unsecured notes was measured using a market approach, based upon the average of quotes for the acquired debt from major financial institutions and a third-party valuation service. Additionally, $1.5 billion of borrowings under revolving credit agreements and other debt of approximately $200 million approximated fair value. Noncontrolling Interest Through the Andeavor acquisition, we acquired the general partnership interest of ANDX, which is a VIE because the limited partners of ANDX do not have substantive kick-out or substantive participating rights over the general partner. We are the primary beneficiary of ANDX because in addition to our significant economic interest, we also have the ability, through our 100 percent ownership of the general partner, to control the decisions that most significantly impact ANDX. The fair value of the noncontrolling interest in ANDX was based on the share price, shares outstanding and the percent of public unitholders of ANDX on October 1, 2018. The share price of ANDX is a Level 1 measurement. Acquisition Costs We recognized $47 million in acquisition costs. Additionally, we recognized various other transaction-related costs, including employee-related costs associated with the Andeavor acquisition. All of these costs are reflected in selling, general and administrative expenses for the year ended December 31, 2018. The employee-related costs are primarily due to pre-existing Andeavor change in control and equity award agreements that create obligations and accelerated equity vesting upon MPC notifying employees of significant changes to or elimination of their responsibilities as part of our ongoing integration efforts. Andeavor Revenues and Income from Operations Andeavor’s results have been included in MPC’s financial statements for the period subsequent to the date of the acquisition on October 1, 2018. Andeavor contributed revenues of approximately $11.3 billion for the period from October 1 through December 31, 2018. We do not believe it is practical to disclose Andeavor’s contribution to earnings for the period from October 1, 2018 through December 31, 2018 as our integration efforts have resulted in the elimination of Andeavor stand-alone discrete financial information due mainly to our inclusion of Andeavor inventory in our consolidated LIFO inventory pools, which does not allow us to objectively distinguish the cost of sales between the two historical reporting entities. Pro Forma Financial Information The following unaudited pro forma financial information presents consolidated results assuming the Andeavor acquisition occurred on January 1, 2017. (In millions, except per share data) 2018 2017 Sales and other operating revenues (a) $ 131,695 $ 117,549 Net income attributable to MPC 4,371 4,832 Net income attributable to MPC per share – basic $ 8.44 $ 6.47 Net income attributable to MPC per share – diluted 8.31 6.41 (a) The 2018 period reflects an election to present certain taxes on a net basis concurrent with our adoption of ASC 606. The pro forma information includes adjustments to align accounting policies, an adjustment to depreciation expense to reflect the increased fair value of property, plant and equipment, increased amortization expense related to identifiable intangible assets and the related income tax effects. The pro forma information does not reflect the $727 million effect on net income attributable to MPC related to purchase accounting related inventory effects and transaction-related costs as these charges do not have a continuing impact on the consolidated results. Acquisition of Express Mart During the fourth quarter of 2018, Speedway acquired 78 store locations from Petr-All Petroleum Consulting Corporation for total consideration of $266 million . These stores are located primarily in the Syracuse, Rochester and Buffalo markets in New York and operate under the Express Mart brand. Based on the final fair value estimates of assets acquired and liabilities assumed at the acquisition date, $97 million of the purchase price was allocated to property, plant and equipment, $9 million to inventory, $2 million to intangibles and $158 million to goodwill. Goodwill is tax deductible and represents the value expected to be created by geographically expanding our retail platform and the assembled workforce. The amount of revenue and income from operations associated with the acquisition from the acquisition date to December 31, 2018 did not have a material impact on the consolidated financial statements. In addition, assuming the acquisition had occurred on January 1, 2017, the consolidated pro forma results would not have been materially different from the reported results. Acquisition of Mt. Airy Terminal On September 26, 2018, MPLX acquired an eastern U.S. Gulf Coast export terminal (“Mt. Airy Terminal”) from Pin Oak Holdings, LLC for total consideration of $451 million . The terminal includes 4 million barrels of third-party leased storage capacity and a 120 mbpd dock. The Mt. Airy Terminal is located on the Mississippi River between New Orleans and Baton Rouge, near several Gulf Coast refineries, including our Garyville Refinery, and numerous rail lines and pipelines. The Mt. Airy Terminal is accounted for within the Midstream segment. Based on the final fair value estimates of assets acquired and liabilities assumed at the acquisition date, $336 million of the purchase price was allocated to property, plant and equipment and $126 million to goodwill with the remaining difference being primarily allocated to net assumed liabilities. Goodwill is tax deductible and represents the significant growth potential of the terminal due to the multiple pipelines and rail lines which cross the property, the terminal’s position as an aggregation point for liquids growth in the region for both ocean-going vessels and inland barges, the proximity of the terminal to our Garyville refinery and other refineries in the region as well as the capability to construct an additional dock at the site. The amount of revenue and income from operations associated with the acquisition from the terminal acquisition date to December 31, 2018 did not have a material impact on the consolidated financial statements. In addition, assuming the terminal acquisition had occurred on January 1, 2017, the consolidated pro forma results would not have been materially different from the reported results. 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 present the Ozark pipeline within the Midstream segment. The amount of revenue and income from operations associated with the acquisition from the acquisition date to December 31, 2017 did not have a material impact on the consolidated financial statements. In addition, assuming the acquisition of the Ozark pipeline had occurred on January 1, 2016, the consolidated pro forma results would not have been materially different from reported results. Investment in Pipeline Company On February 15, 2017, MPLX acquired a partial, indirect equity interest in the Dakota Access Pipeline (“DAPL”) and Energy Transfer Crude Oil Company Pipeline (“ETCOP”) projects, collectively referred to as the Bakken Pipeline system, through a joint venture with Enbridge Energy Partners L.P. (“Enbridge Energy Partners”). MPLX contributed $500 million of the $2 billion purchase price paid by the joint venture, MarEn Bakken Company LLC (“MarEn Bakken”), to acquire a 36.75 percent indirect equity interest in the Bakken Pipeline system from Energy Transfer Partners, L.P. (“ETP”) and Sunoco Logistics Partners, L.P. (“SXL”). MPLX holds, through a subsidiary, a 25 percent interest in MarEn Bakken, which equates to an approximate 9.2 percent indirect equity interest in the Bakken Pipeline system. We account for the investment in MarEn Bakken as part of our Midstream segment using the equity method of accounting. Formation of Gathering and Processing Joint Venture Effective January 1, 2017, MPLX and Antero Midstream formed a joint venture, Sherwood Midstream LLC (“Sherwood Midstream”), to support the development of Antero Resources Corporation’s Marcellus Shale acreage in West Virginia. MPLX has a 50 percent ownership interest in Sherwood Midstream. In connection with this transaction, MPLX contributed assets then 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 initial ownership interest. 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.

Variable Interest Entities

Variable Interest Entities	12 Months Ended
	Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Variable Interest Entities	VARIABLE INTEREST ENTITIES Consolidated VIEs We control MPLX and ANDX through our ownership of the general partner of both entities. MPLX and ANDX are VIEs because the limited partners do not have substantive kick-out or substantive participating rights over the general partner. We are the primary beneficiary of both MPLX and ANDX because in addition to our significant economic interest, we also have the ability, through our ownership of the general partner, to control the decisions that most significantly impact MPLX and ANDX. We therefore consolidate MPLX and ANDX and record a noncontrolling interest for the interest owned by the public. We also record a redeemable noncontrolling interest related to MPLX’s preferred units. The creditors of MPLX and ANDX do not have recourse to MPC’s general credit through guarantees or other financial arrangements. 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. The assets of MPLX and ANDX can only be used to settle their own obligations and their creditors have no recourse to our assets. The following table present balance sheet information for the assets and liabilities of MPLX and ANDX, which are included in our balance sheets. December 31, December 31, (In millions) MPLX ANDX (a) MPLX Assets Cash and cash equivalents $ 68 $ 10 $ 5 Receivables, less allowance for doubtful accounts 425 199 299 Inventories 77 22 65 Other current assets 45 57 29 Equity method investments 4,174 602 4,010 Property, plant and equipment, net 14,639 6,845 12,187 Goodwill 2,586 1,051 2,245 Other noncurrent assets 458 1,242 479 Liabilities Accounts payable $ 776 $ 215 $ 621 Payroll and benefits payable 2 10 1 Accrued taxes 48 23 38 Debt due within one year 1 504 1 Other current liabilities 177 77 130 Long-term debt 13,392 4,469 6,945 Deferred income taxes 13 1 5 Defined benefit postretirement plan obligations — — — Deferred credits and other liabilities 276 68 230 (a) The balances reflected here are ANDX’s historical balances as the preliminary purchase accounting adjustments related to ANDX’s assets and liabilities in connection with the Andeavor acquisition and reflected on our consolidated balance sheet as of December 31, 2018 have not yet been pushed down to this subsidiary. Non-Consolidated VIEs Crowley Coastal Partners In May 2016, Crowley Coastal Partners LLC (“Crowley Coastal Partner”) was formed to own an interest in both Crowley Ocean Partners LLC (“Crowley Ocean Partners”) and Crowley Blue Water Partners LLC (“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, 2018 was $481 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 ability 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”), 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, 2018 , 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. 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, 2018 was $2.0 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, 2018 , we had a 34 percent indirect ownership interest in Ohio Gathering. As this entity is a subsidiary of MarkWest Utica EMG, which is accounted for as an equity method investment, MPLX reports its portion of Ohio Gathering’s net assets as a component of its investment in MarkWest Utica EMG. 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, 2018 , MPLX had a 50 percent ownership interest in Sherwood Midstream. Sherwood Midstream’s inability to fund its planned activities without additional subordinated financial support qualify it as a VIE. MPLX is not deemed to be the primary beneficiary, due to Antero Midstream’s voting rights on significant matters. We account for our ownership interest in Sherwood Midstream using the equity method of accounting. Our maximum exposure to loss as a result of our involvement with Sherwood Midstream includes our equity investment, any additional capital contribution commitments and any operating expenses incurred by the subsidiary operator in excess of compensation received for the performance of the operating services. Our equity investment in Sherwood Midstream at December 31, 2018 was $366 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 an initial 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, 2018 was $157 million . Other Non-Consolidated VIEs We have a 67 percent ownership interest in Andeavor Logistics Rio Pipeline LLC (“ALRP”), a recently constructed crude oil pipeline located in the Delaware and Midland basins in west Texas. We are not the primary beneficiary of ALRP because we jointly direct the activities of ALRP that most significantly impact its economic performance with the other minor shareholder. Our equity investment in ALRP at December 31, 2018 was $181 million . We have a 78 percent ownership interest in Rendezvous Gas Services, LLC (“RGS”), which owns and operates the infrastructure that transports gas from certain fields to several re-delivery points in southwestern Wyoming, including natural gas processing facilities that are owned by us or a third party. We are not the primary beneficiary of RGS. Our equity investment in RGS at December 31, 2018 was $248 million . ALRP and RGS are unconsolidated variable interest entities and we use the equity method of accounting with respect to our investments in each entity.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions	RELATED PARTY TRANSACTIONS We believe that transactions with related parties were conducted on terms comparable to those with unaffiliated parties. Transactions with related parties were as follows: (In millions) 2018 2017 2016 Sales to related parties (a) $ 754 $ 629 $ 62 Purchases from related parties (b) 610 570 509 (a) Sales to related parties consists primarily of sales of refined products to PFJ Southeast, an equity affiliate which owns and operates travel plazas primarily in the Southeast region of the United States. (b) We obtain transportation services and purchase ethanol from certain of our equity affiliates, none of which is individually material.

Income per Common Share

Income per Common Share	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Income per Common Share	INCOME PER COMMON SHARE We compute basic earnings per share by dividing net income attributable to MPC less income allocated to participating securities by the weighted average number of shares of common stock outstanding. Since MPC grants certain incentive compensation awards to employees and non-employee directors that are considered to be participating securities, we have calculated our earnings per share using the two-class method. Diluted income per share assumes exercise of certain stock-based compensation awards, provided the effect is not anti-dilutive. (In millions, except per share data) 2018 2017 2016 Basic earnings per share: Allocation of earnings: Net income attributable to MPC $ 2,780 $ 3,432 $ 1,174 Income allocated to participating securities 1 2 1 Income available to common stockholders – basic $ 2,779 $ 3,430 $ 1,173 Weighted average common shares outstanding 518 507 528 Basic earnings per share $ 5.36 $ 6.76 $ 2.22 Diluted earnings per share: Allocation of earnings: Net income attributable to MPC $ 2,780 $ 3,432 $ 1,174 Income allocated to participating securities 1 2 1 Income available to common stockholders – diluted $ 2,779 $ 3,430 $ 1,173 Weighted average common shares outstanding 518 507 528 Effect of dilutive securities 8 5 2 Weighted average common shares, including dilutive effect 526 512 530 Diluted earnings per share $ 5.28 $ 6.70 $ 2.21 The following table summarizes the shares that were anti-dilutive, and therefore, were excluded from the diluted share calculation. (In millions) 2018 2017 2016 Shares issuable under stock-based compensation plans — 1 3

Equity

Equity	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Equity	EQUITY On October 1, 2018, in connection with the Andeavor acquisition, we amended our certificate of incorporation to increase the number of authorized shares of MPC common stock from one billion to two billion , as approved by MPC stockholders at MPC’s September 24, 2018 special meeting of stockholders. As of December 31, 2018 , we had $4.90 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 effected through Rule 10b5-1 plans. The timing and amount of future repurchases, if any, will depend upon several factors, including market and business conditions, and such repurchases may be discontinued at any time. Total share repurchases were as follows for the respective periods: (In millions, except per share data) 2018 2017 2016 Number of shares repurchased 47 44 4 Cash paid for shares repurchased $ 3,287 $ 2,372 $ 197 Average cost per share $ 69.46 $ 53.85 $ 41.84

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Segment Information	SEGMENT INFORMATION We have three reportable segments: Refining & Marketing; Retail ; 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 16 refineries in the West Coast, Gulf Coast and Mid-Continent regions of the United States, purchases refined products and ethanol for resale and distributes refined products largely through transportation, storage, distribution and marketing services provided largely by our Midstream segment. We sell refined products to wholesale marketing customers domestically and internationally, to buyers on the spot market, to our Retail business segment and to independent entrepreneurs who operate primarily Marathon ® branded outlets. • Retail – sells transportation fuels and convenience products in the retail market across the United States through company-owned and operated convenience stores, primarily under the Speedway brand, and long-term fuel supply contracts with direct dealers who operate locations mainly under the ARCO brand. • Midstream – transports, stores, distributes and markets crude oil and refined products principally for the Refining & Marketing segment via refining logistics assets, pipelines, terminals, towboats and barges; gathers, processes and transports natural gas; and gathers, transports, fractionates, stores and markets NGLs. The Midstream segment primarily reflects the results of MPLX and ANDX, our sponsored master limited partnerships. On October 1, 2018, we acquired Andeavor and its results are included in each of our segments from the date of the acquisition. Also, on February 1, 2018, we contributed certain refining logistics assets and fuels distribution services to MPLX. The results of these new businesses are reported in the Midstream segment prospectively from February 1, 2018, resulting in a net reduction of $874 million to Refining & Marketing segment results and a net increase to Midstream segment results of the same amount. No effect was given to prior periods as these entities were not considered businesses prior to February 1, 2018. Segment income represents income from operations attributable to the reportable segments. Corporate administrative expenses, except for those attributable to MPLX and ANDX, 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 the third quarter of 2018, we began reporting segment capital expenditures and investments excluding acquisitions in the current and comparative periods. (In millions) Refining & Marketing Retail Midstream Total Year Ended December 31, 2018 Revenues: Third party $ 68,939 $ 23,538 $ 3,273 $ 95,750 Intersegment 12,914 6 3,387 16,307 Related party 746 8 — 754 Segment revenues $ 82,599 $ 23,552 $ 6,660 $ 112,811 Segment income from operations $ 2,481 $ 1,028 $ 2,752 $ 6,261 Income from equity method investments (b) 15 74 274 363 Depreciation and amortization (b) 1,174 353 885 2,412 Capital expenditures and investments (c) 1,057 460 2,630 4,147 (In millions) Refining & Marketing Retail 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 $ 729 $ 1,339 $ 4,389 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) 832 381 1,755 2,968 (In millions) Refining & Marketing Retail 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 (d) $ 1,357 $ 733 $ 1,048 $ 3,138 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 1,558 2,915 (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 and investments in affiliates. (e) In 2016, the Refining & Marketing and Retail segments include an inventory LCM benefit of $345 million and $25 million , respectively. The following reconciles segment income from operations to income before income taxes as reported in the consolidated statements of income: (In millions) 2018 2017 2016 Segment income from operations $ 6,261 $ 4,389 $ 3,138 Items not allocated to segments: Corporate and other unallocated items (a) (502 ) (365 ) (266 ) Transaction-related costs (197 ) — — Litigation — (29 ) — Impairments (b) 9 23 (486 ) Income from operations 5,571 4,018 2,386 Net interest and other financial costs 1,003 674 564 Income before income taxes $ 4,568 $ 3,344 $ 1,822 (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 and ANDX, which are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Retail segments. (b) 2018 and 2017 includes MPC’s share of gains from the the sale of assets remaining from the canceled Sandpiper pipeline project. 2016 includes impairments of goodwill and equity method investments. See Note 17 . The following reconciles segment capital expenditures and investments to total capital expenditures: (In millions) 2018 2017 2016 Segment capital expenditures and investments $ 4,147 $ 2,968 $ 2,915 Less investments in equity method investees 409 305 288 Plus items not allocated to segments: Corporate 77 83 81 Capitalized interest 80 55 63 Total capital expenditures (a) $ 3,895 $ 2,801 $ 2,771 (a) 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) 2018 2017 2016 Refined products $ 83,888 $ 63,846 $ 54,450 Merchandise 5,332 5,174 5,297 Crude oil and refinery feedstocks 4,143 3,403 2,038 Midstream services, transportation and other 2,387 1,681 1,492 Sales and other operating revenues (a) $ 95,750 $ 74,104 $ 63,277 (a) The 2018 period reflects an election to present certain taxes on a net basis concurrent with our adoption of ASC 606. No single customer accounted for more than 10 percent of annual revenues for the years ended December 31, 2018 , 2017 and 2016 . 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.

Net Interest and Other Financia

Net Interest and Other Financial Costs	12 Months Ended
	Dec. 31, 2018
Other Income and Expenses [Abstract]
Net Interest and Other Financial Costs	NET INTEREST AND OTHER FINANCIAL COSTS Net interest and other financial costs was: (In millions) 2018 2017 2016 Interest income $ (87 ) $ (27 ) $ (6 ) Interest expense 1,026 688 602 Interest capitalized (80 ) (63 ) (64 ) Pension and other postretirement non-service costs (a) 53 49 8 Loss on extinguishment of debt 64 — — Other financial costs 27 27 24 Net interest and other financial costs $ 1,003 $ 674 $ 564 (a) See Note 22 .

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES The TCJA was signed into law on December 22, 2017, providing several significant changes to U.S. tax law, including a reduction in the corporate tax rate from 35 percent to 21 percent effective for MPC in 2018. As a result of the rate change, MPC was required to calculate the effect of the TCJA on its deferred tax balances as of the enactment date, which was to reduce net deferred tax liabilities by $1.5 billion in 2017. Income tax provisions (benefits) were: 2018 2017 2016 (In millions) Current Deferred Total Current Deferred Total Current Deferred Total Federal $ 715 $ 2 $ 717 $ 681 $ (1,270 ) $ (589 ) $ 189 $ 336 $ 525 State and local 178 61 239 98 33 131 27 57 84 Foreign 22 (16 ) 6 (6 ) 4 (2 ) (1 ) 1 — Total $ 915 $ 47 $ 962 $ 773 $ (1,233 ) $ (460 ) $ 215 $ 394 $ 609 A reconciliation of the federal statutory income tax rate applied to income before income taxes to the provision for income taxes follows: 2018 2017 2016 Statutory rate applied to income before income taxes 21 % 35 % 35 % State and local income taxes, net of federal income tax effects 4 2 3 Domestic manufacturing deduction — (1 ) (1 ) Noncontrolling interests (4 ) (4 ) (1 ) Biodiesel excise tax credit — — (1 ) TCJA legislation — (45 ) — Other — (1 ) (2 ) Provision for income taxes 21 % (14 )% 33 % Deferred tax assets and liabilities resulted from the following: December 31, (In millions) 2018 2017 Deferred tax assets: Employee benefits $ 660 $ 348 Environmental remediation 111 16 Debt financing 39 — Net operating loss carryforwards 17 12 Foreign currency 28 13 Tax credit carryforwards 21 — Other 88 31 Total deferred tax assets 964 420 Deferred tax liabilities: Property, plant and equipment 2,830 1,603 Inventories 678 473 Investments in subsidiaries and affiliates 2,130 912 Intangibles 97 70 Other 64 3 Total deferred tax liabilities 5,799 3,061 Net deferred tax liabilities $ 4,835 $ 2,641 The increase in net deferred tax liabilities is primarily related to the revaluation of MPC’s legacy deferred tax liabilities and the recognition of net deferred tax liabilities both as a result of the Andeavor acquisition. Net deferred tax liabilities were classified in the consolidated balance sheets as follows: December 31, (In millions) 2018 2017 Assets: Other noncurrent assets $ 29 $ 13 Liabilities: Deferred income taxes 4,864 2,654 Net deferred tax liabilities $ 4,835 $ 2,641 Tax Carryforwards At December 31, 2018 and 2017 , federal operating loss carryforwards were $7 million and $5 million , respectively, which expire in 2022 through 2037 . As of December 31, 2018 and 2017 , state and local operating loss carryforwards were $10 million and $8 million , respectively, which expire in 2017 through 2037 . Valuation Allowances As of December 31, 2018 and 2017 , $10 million and $11 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. While Andeavor also undergoes continual IRS examination, it did not participate in the CAP for tax periods prior to the acquisition of Andeavor. MPC’s IRS audits have been completed through the 2009 tax year. Andeavor and its subsidiaries’ IRS audits have been completed through the 2008 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, 2018 , our income tax returns remain subject to examination in the following major tax jurisdictions for the tax years indicated: United States Federal 2009 - 2017 States 2006 - 2017 The following table summarizes the activity in unrecognized tax benefits: (In millions) 2018 2017 2016 January 1 balance $ 19 $ 7 $ 12 Additions for tax positions of prior years — 13 6 Reductions for tax positions of prior years (5 ) — (10 ) Settlements — (1 ) (1 ) Statute of limitations (12 ) — — Acquired from Andeavor 209 — — December 31 balance $ 211 $ 19 $ 7 If the unrecognized tax benefits as of December 31, 2018 were recognized, $201 million would affect our effective income tax rate. There were $15 million of uncertain tax positions as of December 31, 2018 for which it is reasonably possible that the amount of unrecognized tax benefits would significantly decrease during the next twelve months. The unrecognized tax benefits acquired from Andeavor arise primarily from a 2009-2010 refund claim related to the federal income tax effects of receiving an excise tax credit on ethanol blending for those years. Prior to its spinoff on June 30, 2011, Marathon Petroleum Corporation was included in the Marathon Oil Corporation (“Marathon Oil”) U.S. federal income tax returns for all applicable years. During the third quarter of 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 $1 million , $3 million and ($5) million in 2018 , 2017 and 2016 , respectively. As of December 31, 2018 and 2017 , $18 million and $17 million of interest and penalties were accrued related to income taxes.

Inventories

Inventories	12 Months Ended
	Dec. 31, 2018
Inventory Disclosure [Abstract]
Inventories	INVENTORIES December 31, (In millions) 2018 2017 Crude oil and refinery feedstocks $ 3,655 $ 2,056 Refined products 5,234 2,839 Materials and supplies 720 494 Merchandise 228 161 Total $ 9,837 $ 5,550 The LIFO method accounted for 92 percent and 90 percent of total inventory value at December 31, 2018 and 2017 , respectively. There was no excess of replacement or current cost over our stated LIFO cost as of December 31, 2018 . Current acquisition costs of inventories were estimated to exceed the LIFO inventory value at December 31, 2017 by $1.21 billion . 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 2018 and 2016.

Equity Method Investments

Equity Method Investments	12 Months Ended
	Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments	EQUITY METHOD INVESTMENTS Ownership as of Carrying value at December 31, December 31, (Dollars in millions) 2018 2018 2017 R&M Watson Cogeneration Company 51% $ 84 $ — Other 121 104 R&M Total $ 205 $ 104 Retail PFJ Southeast LLC 29% $ 341 $ 328 Retail Total $ 341 $ 328 Midstream Andeavor Logistics Rio Pipeline LLC 67% $ 181 $ — Centrahoma Processing LLC 40% 160 121 Crowley Coastal Partners, LLC 50% 190 188 Illinois Extension Pipeline Company, L.L.C 35% 275 284 LOOP LLC 51% 282 282 MarEn Bakken Company LLC 25% 498 520 MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C. 67% 236 164 MarkWest Utica EMG 56% 2,039 2,139 Minnesota Pipe Line Company, LLC 17% 197 — Rendezvous Gas Services, L.L.C. 78% 248 — Sherwood Midstream Holdings LLC (a) 60% 157 165 Sherwood Midstream LLC 50% 366 236 Other 523 256 Midstream Total $ 5,352 $ 4,355 Total $ 5,898 $ 4,787 (a) Excludes Sherwood Midstream LLC’s investment in Sherwood Midstream Holdings LLC. Summarized financial information for all equity method investments in affiliated companies, combined, was as follows: (In millions) 2018 2017 2016 Income statement data: Revenues and other income $ 7,726 $ 6,235 $ 2,421 Income (loss) from operations 1,375 1,075 (116 ) Net income (loss) 1,242 922 (250 ) Balance sheet data – December 31: Current assets $ 1,443 $ 860 Noncurrent assets 12,408 10,854 Current liabilities 1,857 547 Noncurrent liabilities 1,788 1,714 As of December 31, 2018 , the carrying value of our equity method investments was $1.59 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 $721 million of excess related to goodwill and non-depreciable assets. Dividends and partnership distributions received from equity method investees (excluding distributions that represented a return of capital previously contributed) were $519 million , $391 million and $317 million in 2018 , 2017 and 2016 .

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENT (In millions) Estimated Useful Lives December 31, 2018 2017 Refining & Marketing 4 - 30 years $ 27,590 $ 19,490 Retail 4 - 25 years 6,637 5,358 Midstream 3 - 51 years 25,692 14,898 Corporate and Other 4 - 40 years 1,294 792 Total 61,213 40,538 Less accumulated depreciation 16,155 14,095 Property, plant and equipment, net $ 45,058 $ 26,443 Property, plant and equipment includes gross assets acquired under capital leases of $786 million and $602 million at December 31, 2018 and 2017 , respectively, with related amounts in accumulated depreciation of $202 million and $248 million at December 31, 2018 and 2017 . Property, plant and equipment includes construction in progress of $3.49 billion and $2.20 billion at December 31, 2018 and 2017 , respectively, which primarily relates to capital projects at our refineries and midstream facilities.

Goodwill and Intangibles

Goodwill and Intangibles	12 Months Ended
	Dec. 31, 2018
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 2018 and 2017 , our annual testing did not indicate any impairment of goodwill. The changes in the carrying amount of goodwill for 2017 and 2018 were as follows: (In millions) Refining & Marketing Retail Midstream Total Balance at January 1, 2017 $ 519 $ 792 $ 2,276 $ 3,587 Disposition — (1 ) — (1 ) Balance at December 31, 2017 $ 519 $ 791 $ 2,276 $ 3,586 Acquisitions 4,717 4,050 7,831 16,598 Transfer of assets related to dropdowns (216 ) — 216 — Balance at December 31, 2018 $ 5,020 $ 4,841 $ 10,323 $ 20,184 The 2018 increase in goodwill resulted mainly from the acquisition of Andeavor. The goodwill represents the value expected to be created by optimization of crude supply, a nationwide retail and marketing platform, diversification of our refining and midstream footprints and optimization of information systems and business processes. As discussed in Note 5 , this goodwill is based on our preliminary determination of the fair value of assets acquired and liabilities assumed in the Andeavor acquisition. We will complete a final determination of the fair value of certain assets and liabilities and an allocation of the resulting goodwill to our reporting units within one year from the acquisition. Intangible Assets Our finite-lived intangible assets as of December 31, 2018 and 2017 are as shown below. The increases in 2018 reflect preliminary estimates for customer contracts and relationships as well as brand rights and tradenames acquired in the the Andeavor acquisition. December 31, 2018 December 31, 2017 (In millions) Gross Accumulated Amortization Net Gross Accumulated Amortization Net Customer contracts and relationships $ 3,184 $ 261 $ 2,923 $ 654 $ 139 $ 515 Brand rights and tradenames 208 33 175 25 24 1 Royalty agreements 129 70 59 129 63 66 Other 190 33 157 84 35 49 Total $ 3,711 $ 397 $ 3,314 $ 892 $ 261 $ 631 At December 31, 2018 and 2017 , we had indefinite-lived intangible assets of $94 million and $95 million , respectively, which are primarily emission allowance credits and trademarks. Amortization expense for 2018 and 2017 was $134 million and $52 million , respectively. Estimated future amortization expense related to the intangible assets at December 31, 2018 is as follows: (In millions) 2019 $ 387 2020 385 2021 379 2022 378 2023 361

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS Fair Values – Recurring The following tables present assets and liabilities accounted for at fair value on a recurring basis as of December 31, 2018 and 2017 by fair value hierarchy level. We have elected to offset the fair value amounts recognized for multiple derivative contracts executed with the same counterparty, including any related cash collateral as shown below; however, fair value amounts by hierarchy level are presented on a gross basis in the following tables. December 31, 2018 Fair Value Hierarchy (In millions) Level 1 Level 2 Level 3 Netting and Collateral (a) Net Carrying Value on Balance Sheet (b) Collateral Pledged Not Offset Commodity derivative instruments, assets $ 370 $ 31 $ — $ (323 ) $ 78 $ 2 Total assets at fair value $ 370 $ 31 $ — $ (323 ) $ 78 $ 2 Commodity derivative instruments, liabilities $ 255 $ 37 $ — $ (284 ) $ 8 $ — Embedded derivatives in commodity contracts — — 61 — 61 — Total liabilities at fair value $ 255 $ 37 $ 61 $ (284 ) $ 69 $ — 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 — — 64 — 64 — Total liabilities at fair value $ 126 $ — $ 66 $ (126 ) $ 66 $ — (a) Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of December 31, 2018 , cash collateral of $52 million was netted with mark-to-market derivative assets and $13 million was netted with mark-to-market liabilities. As of December 31, 2017 , cash collateral of $8 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. 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 2 instruments are valued based on quoted prices for similar assets and liabilities in active markets, and inputs other than quoted prices, such as liquidity, that are observable for the asset or liability. Commodity derivatives in Level 2 are OTC contracts, which are valued using market quotations from independent price reporting agencies, third-party brokers and commodity exchange price curves that are corroborated with market data. Level 3 instruments are OTC NGL contracts and embedded derivatives in commodity contracts. The embedded derivative liability relates to a natural gas purchase agreement embedded in a keep‑whole processing agreement. The fair value calculation for these Level 3 instruments at December 31, 2018 used significant unobservable inputs including: (1) NGL prices interpolated and extrapolated due to inactive markets ranging from $0.58 to $1.01 per gallon and (2) the probability of renewal of 90 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. Increases or decreases in the fractionation spread result in an increase or decrease in the fair value of the embedded derivative liability. An increase in the probability of renewal would result in an increase in the fair value of the related embedded derivative liability. The following is a reconciliation of the net beginning and ending balances recorded for net liabilities classified as Level 3 in the fair value hierarchy. (In millions) 2018 2017 Beginning balance $ 66 $ 190 Contingent consideration payment — (131 ) Unrealized and realized losses included in net income 3 25 Settlements of derivative instruments (8 ) (18 ) Ending balance $ 61 $ 66 The amount of total losses for the period included in earnings attributable to the change in unrealized losses relating to assets still held at the end of period: Derivative instruments $ 8 $ 8 Contingent consideration agreement — 1 Total $ 8 $ 9 See Note 18 for the income statement impacts of our derivative instruments. Fair Values – Nonrecurring 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. 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. Fair Values – Reported We believe the carrying value of our other financial instruments, including cash and cash equivalents, receivables, accounts payable and certain accrued liabilities approximate fair value. Our fair value assessment incorporates a variety of considerations, including the short-term duration of the instruments and the expected insignificance of bad debt expense, which includes an evaluation of counterparty credit risk. The borrowings under our revolving credit facilities, which include variable interest rates, approximate fair value. The fair value of our fixed rate long-term debt is based on prices from recent trade activity and is categorized in level 3 of the fair value hierarchy. The carrying and fair values of our debt were approximately $27.0 billion and $26.5 billion at December 31, 2018 , respectively, and approximately $12.6 billion and $13.9 billion at December 31, 2017 , respectively. These carrying and fair values of our debt exclude the unamortized issuance costs which are netted against our total debt.

Derivatives

Derivatives	12 Months Ended
	Dec. 31, 2018
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 fair value of derivative instruments as of December 31, 2018 and 2017 and the line items in the balance sheets in which the fair values are reflected. The fair value amounts below are presented on a gross basis and do not reflect the netting of asset and liability positions permitted under the terms of our master netting arrangements including cash collateral on deposit with, or received from, brokers. We offset the recognized fair value amounts for multiple derivative instruments executed with the same counterparty in our financial statements when a legal right of offset exists. As a result, the asset and liability amounts below will not agree with the amounts presented in our consolidated balance sheets. (In millions) December 31, 2018 Balance Sheet Location Asset Liability Commodity derivatives Other current assets $ 400 $ 283 Other current liabilities (a) 1 16 Deferred credits and other liabilities (a) — 54 (In millions) December 31, 2017 Balance Sheet Location Asset Liability Commodity derivatives Other current assets $ 127 $ 126 Other current liabilities (a) — 14 Deferred credits and other liabilities (a) — 52 (a) Includes embedded derivatives. 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, refined products and blending products as of December 31, 2018 . Percentage of contracts that expire next quarter Position (Units in thousands of barrels) Long Short Exchange-traded (a) Crude oil 71.5% 40,257 44,709 Refined products 75.9% 10,210 11,149 Blending products 70.3% 5,194 7,356 OTC Crude oil —% 880 — Blending products 24.1% 2,480 2,480 (a) Included in exchange-traded are spread contracts in thousands of barrels: Crude oil - 7,470 long and 6,800 short; Refined products - 450 long and 450 short; Blending products - 2,678 long and 2,767 short The following table summarizes the effect of all commodity derivative instruments in our consolidated statements of income: (In millions) Gain (Loss) Income Statement Location 2018 2017 2016 Sales and other operating revenues $ 13 $ 5 $ (13 ) Cost of revenues (59 ) (26 ) (167 ) Total $ (46 ) $ (21 ) $ (180 )

Debt

Debt	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Debt	DEBT Our outstanding borrowings at December 31, 2018 and 2017 consisted of the following: December 31, (In millions) 2018 2017 Marathon Petroleum Corporation: Commercial paper $ — $ — 364-day bank revolving credit facility due September 2019 — — Trade receivables securitization facility due July 2019 — — Bank revolving credit facility due October 2023 — — Senior notes, 2.700% due December 2018 — 600 Senior notes, 3.400% due December 2020 650 650 Senior notes, 5.125% due March 2021 1,000 1,000 Senior notes, 5.375% due October 2022 337 — Senior notes, 4.750% due December 2023 614 — Senior notes, 5.125% due April 2024 241 — Senior notes, 3.625%, due September 2024 750 750 Senior notes, 5.125% due December 2026 719 — Senior notes, 3.800% due April 2028 496 — 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, 4.500% due April 2048 498 — Andeavor senior notes, 3.800% - 5.375% due 2022 - 2048 469 — Senior notes, 5.000%, due September 2054 400 400 Capital lease obligations due 2019-2033 629 356 December 31, (In millions) 2018 2017 Notes payable 11 — MPLX LP: MPLX bank revolving credit facility due 2022 — 505 MPLX senior notes, 5.500% due February 2023 — 710 MPLX senior notes, 3.375% due March 2023 500 — MPLX senior notes, 4.500% due July 2023 989 989 MPLX senior notes, 4.875% due December 2024 1,149 1,149 MPLX senior notes, 4.000% due February 2025 500 500 MPLX senior notes, 4.875% due June 2025 1,189 1,189 MarkWest senior notes, 4.500% - 5.500% due 2023 - 2025 23 63 MPLX senior notes, 4.125% due March 2027 1,250 1,250 MPLX senior notes, 4.000% due March 2028 1,250 — MPLX senior notes, 4.800% due February 2029 750 — MPLX senior notes, 4.500% due April 2038 1,750 — MPLX senior notes, 5.200% due March 2047 1,000 1,000 MPLX senior notes, 4.700% due April 2048 1,500 — MPLX senior notes, 5.500% due February 2049 1,500 — MPLX senior notes, 4.900% due April 2058 500 — MPLX capital lease obligations due 2020 6 7 ANDX LP: ANDX revolving and dropdown credit facilities due 2021 1,245 — ANDX senior notes, 5.500% due October 2019 500 — ANDX senior notes, 6.250% due October 2022 300 — ANDX senior notes, 3.500% due December 2022 500 — ANDX senior notes, 6.375% due May 2024 450 — ANDX senior notes, 5.250% due January 2025 750 — ANDX senior notes, 4.250% due December 2027 750 — ANDX senior notes, 5.200% due December 2047 500 — ANDX capital lease obligations 15 — Total 27,980 13,418 Unamortized debt issuance costs (128 ) (59 ) Unamortized (discount) premium, net (328 ) (413 ) Amounts due within one year (544 ) (624 ) Total long-term debt due after one year $ 26,980 $ 12,322 Principal maturities for our debt obligations and capital lease obligations as of December 31, 2018 for the next five years were as follows: (In millions) 2019 $ 544 2020 695 2021 2,296 2022 1,320 2023 2,403 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 2018 , we had no borrowings or repayments under the commercial paper program. At December 31, 2018 , we had no amounts outstanding under the commercial paper program. MPC Revolving Credit Agreements On August 28, 2018, we entered into credit agreements with a syndicate of lenders to replace MPC’s previous five-year $2.5 billion bank revolving credit facility due in 2022 and our previous 364-day $1 billion bank revolving agreement that expired in July 2018. The new credit agreements, which became effective October 1, 2018 in connection with the Andeavor acquisition, provide for a $5 billion five -year revolving credit agreement that expires in 2023 (“new MPC five-year credit agreement”) and a $1 billion 364 -day revolving credit agreement that expires in 2019 (“new MPC 364-day credit agreement” and together with the new MPC five-year credit agreement, the “new MPC credit agreements”). MPC has an option under the new MPC five-year credit agreement to increase the aggregate commitments by up to an additional $1 billion , subject to, among other conditions, the consent of the lenders whose commitments would be increased. In addition, MPC may request up to two one -year extensions of the maturity date of the new MPC five-year 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 new MPC five-year credit agreement includes sub-facilities for swing-line loans of up to $250 million and letters of credit of up to $2.2 billion (which may be increased to up to $3 billion upon receipt of additional letter of credit issuing commitments). 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 new 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 based on changes, if any, to 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. The covenants also restrict, among other things, 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, 2018 , we were in compliance with the covenants contained in the MPC credit agreements. There were no borrowings and $32 million of letters of credit outstanding at December 31, 2018 . 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 qualifying 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. As of December 31, 2018 , 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 as of December 31, 2018 . As of December 31, 2018 , qualified trade receivables supported borrowings and letter of credit issuances of $750 million . MPC Senior Notes As a result of the completion of the Andeavor acquisition, we assumed an aggregate principal amount of $3.374 billion senior notes issued by Andeavor. On October 2, 2018, approximately $2.905 billion aggregate principal amount of Andeavor’s outstanding senior notes were exchanged for new unsecured senior notes issued by MPC having the same maturity and interest rates as the Andeavor senior notes and cash in an exchange offer and consent solicitation undertaken by MPC and Andeavor. The new MPC senior notes consist of approximately $337 million aggregate principal amount of 5.375 percent senior notes due October 1, 2022, approximately $614 million aggregate principal amount of 4.750 percent senior notes due December 15, 2023, approximately $241 million aggregate principal amount of 5.125 percent senior notes due April 1, 2024, approximately $719 million aggregate principal amount of 5.125 percent senior notes due December 15, 2026, approximately $496 million aggregate principal amount of 3.800 percent senior notes due April 1, 2028 and approximately $498 million aggregate principal amount of 4.500 percent senior notes due April 1, 2048. After giving effect to the exchange offer and consent solicitation referred to above, as of December 31, 2018, Andeavor had outstanding approximately $138 million aggregate principal amount of 5.375 percent senior notes due October 1, 2022, approximately $236 million aggregate principal amount of 4.750 percent senior notes due December 15, 2023, approximately $59 million aggregate principal amount of 5.125 percent senior notes due April 1, 2024, approximately $30 million aggregate principal amount of 5.125 percent senior notes due December 15, 2026, approximately $4 million aggregate principal amount of 3.800 percent senior notes due April 1, 2028 and approximately $2 million aggregate principal amount of 4.500 percent senior notes due April 1, 2048. Interest on each series of senior notes is payable semi-annually in arrears. The MPC senior notes are unsecured and unsubordinated obligations of MPC and rank equally with all of MPC’s other existing and future unsecured and unsubordinated indebtedness. The MPC senior notes are non-recourse and structurally subordinated to the indebtedness of our subsidiaries, including the outstanding indebtedness of Andeavor, MPLX and ANDX. The Andeavor senior notes are unsecured, unsubordinated obligations of Andeavor and are non-recourse to MPC and any of MPC’s subsidiaries other than Andeavor. On March 15, 2018, we redeemed 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 were redeemed at a price equal to par plus a make whole premium, plus accrued and unpaid interest. The make whole premium of $2.5 million was calculated based on the market yield of the applicable treasury issue as of the redemption date as determined in accordance with the indenture governing the 2018 senior notes. MPLX Credit Agreement 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. Borrowings under the MPLX credit agreement bear interest, at MPLX’s 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 based on changes, if any, to 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. The covenants also restrict, among other things, 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, 2018 , MPLX was in compliance with the covenants contained in the MPLX credit agreement. During 2018 , MPLX borrowed $1.410 billion under the bank revolving credit facility, at an average interest rate of 3.464 percent , per annum, and repaid $1.915 billion of these borrowings. As of December 31, 2018 , MPLX had no outstanding borrowings and $3 million of letters of credit outstanding under the bank revolving credit facility, resulting in total unused loan availability of $2.25 billion . MPLX Term Loan On January 2, 2018, MPLX entered into a term loan agreement with a syndicate of lenders providing for a $4.1 billion , 364 -day term loan facility. MPLX drew the entire amount of the term loan facility in a single borrowing to fund the cash portion of the consideration for the February 1, 2018 dropdown. On February 8, 2018, MPLX used $4.1 billion of the net proceeds from the issuance of MPLX senior notes to repay the 364 -day term-loan facility. MPLX Senior Notes On November 15, 2018, MPLX issued $2.25 billion in aggregate principal amount of senior notes in a public offering, consisting of $750 million aggregate principal amount of 4.800 percent unsecured senior notes due February 2029 and $1.5 billion aggregate principal amount of 5.500 percent unsecured senior notes due February 2049. On December 10, 2018, a portion of the net proceeds from the offering was used to redeem the $750 million in aggregate principal amount of 5.500 percent unsecured notes due February 2023 issued by MPLX and MarkWest. These notes were redeemed at 101.833 percent of the principal amount, plus the write off of unamortized deferred financing costs, resulting in a loss on extinguishment of debt of $60 million . The remaining net proceeds have or will be used to repay borrowings under MPLX’s revolving credit facility and intercompany loan agreement with MPC and for general partnership purposes. 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. The remaining proceeds were used to repay outstanding borrowings under MPLX’s revolving credit facility and intercompany loan agreement with MPC and for general partnership purposes. Interest on each series of MPLX senior notes is payable semi-annually in arrears. The MPLX senior notes are unsecured, unsubordinated obligations of MPLX and are non-recourse to MPC and its subsidiaries other than MPLX and MPLX GP LLC, as the general partner of MPLX. ANDX Credit Agreements ANDX is party to a $1.1 billion revolving credit facility and a $1.0 billion dropdown credit agreement, both of which expire in January 2021 (together, the “ANDX credit agreements”). The ANDX credit agreements are unsecured, but are guaranteed by substantially all of ANDX’s subsidiaries. The ANDX revolving credit facility includes letter of credit issuing capacity of up to $300 million and swingline loan capacity of up to $50 million . The aggregate borrowing capacity under the ANDX credit agreements may be increased by up to an additional $500 million , subject to certain conditions, including the receipt of additional lender commitments. Borrowings under the ANDX credit agreements bear interest, at ANDX’s election, at LIBOR or the Base Rate (as defined in the ANDX credit agreements) plus an applicable margin . ANDX 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 ANDX credit agreements fluctuate based on changes, if any, to ANDX’s credit ratings. The ANDX credit agreements contain 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 ANDX to maintain a Consolidated Leverage Ratio (as defined in the ANDX credit agreements) 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 used to calculate the Consolidated Leverage Ratio is subject to adjustments for certain acquisitions completed and capital projects undertaken during the relevant period. The covenants also restrict, among other things, ANDX’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, 2018 , ANDX was in compliance with the covenants contained in the ANDX credit agreements. On December 20, 2018, ANDX amended the ANDX credit agreements to, among other things, revise the affirmative and negative covenants and events of default to be commensurate with those customarily contained in investment-grade credit facilities of a similar type and nature. Specifically, among other things, the amendments (i) granted additional flexibility to ANDX and its subsidiaries to create liens and incur indebtedness, subject to the Consolidated Leverage Ratio covenant described above, (ii) remove restrictions on the ability of ANDX and its subsidiaries to make investments and (iii) granted additional flexibility to ANDX and its subsidiaries to enter into acquisitions, sell or dispose of assets and enter into related party transactions. In addition, the amendments made certain legal and technical updates to the ANDX credit agreements, including the removal of collateral and security provisions that are no longer applicable and changes to reflect MPC’s acquisition of Andeavor. The amendments did not impact the borrowing capacity available to ANDX or the interest rates and other fees payable by ANDX under the Credit Agreements. During the fourth quarter of 2018, ANDX borrowed $760 million under the ANDX credit facilities, at an average interest rate of 4.460 percent and repaid $635 million of these borrowings. As of December 31, 2018 , ANDX had $1,245 million outstanding borrowings under the ANDX credit facilities, resulting in total unused loan availability of $855 million . ANDX Senior Notes As of December 31, 2018 , ANDX had $3.750 billion aggregate principal amount of senior notes outstanding. The ANDX senior notes consist of $500 million aggregate principal amount of 5.500 percent senior notes due October 15, 2019, $500 million aggregate principal amount of 3.500 percent senior notes due December 1, 2022, $300 million aggregate principal amount of 6.250 percent senior notes due October 15, 2022, $450 million aggregate principal amount of 6.375 percent senior notes due May 1, 2024, $750 million aggregate principal amount of 5.250 percent senior notes due January 15, 2025, $750 million aggregate principal amount of 4.250 percent senior notes due December 1, 2027 and $500 million aggregate principal amount of 5.200 percent senior notes due December 1, 2047. Interest on each series of ANDX senior notes is payable semi-annually in arrears. The ANDX senior notes are unsecured, unsubordinated obligations of ANDX and are non-recourse to MPC and its subsidiaries other than ANDX and Tesoro Logistics GP, LLC, as the general partner of ANDX.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	12 Months Ended
	Dec. 31, 2018
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information	SUPPLEMENTAL CASH FLOW INFORMATION (In millions) 2018 2017 2016 Net cash provided by operating activities included: Interest paid (net of amounts capitalized) $ 887 $ 525 $ 478 Net income taxes paid to taxing authorities 424 904 140 Non-cash investing and financing activities: Capital leases $ 172 $ 71 $ — Contribution of assets to joint venture (a) — 337 273 Intangible asset acquired — 45 — Acquisition: Fair value of MPC shares issued 19,766 — — Fair value of converted equity awards 203 — — (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 . (In millions) December 31, December 31, Cash and cash equivalents $ 1,687 $ 3,011 Restricted cash (a) 38 4 Cash, cash equivalents and restricted cash (b) $ 1,725 $ 3,015 (a) The restricted cash balance is included within other current assets on the consolidated balance sheets. (b) As a result of the adoption of ASU 2016-18, the consolidated statements of cash flows now explain the change during the period of both cash and cash equivalents and restricted cash. The consolidated statements of cash flows exclude changes to the consolidated balance sheets that did not affect cash. The following is a reconciliation of additions to property, plant and equipment to total capital expenditures: (In millions) 2018 2017 2016 Additions to property, plant and equipment per the consolidated statements of cash flows $ 3,578 $ 2,732 $ 2,892 Asset retirement expenditures (a) 8 2 6 Increase (decrease) in capital accruals 309 67 (127 ) Total capital expenditures $ 3,895 $ 2,801 $ 2,771 (a) Included in All other, net – Operating activities on the consolidated statements of cash flows.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Accumulated Other Comprehensive Loss	ACCUMULATED OTHER COMPREHENSIVE LOSS The following table shows the changes in accumulated other comprehensive loss by component. (In millions) Pension Benefits Other Benefits Gain on Cash Flow Hedge Workers Compensation Total Balance as of December 31, 2016 $ (233 ) $ (7 ) $ 4 $ 2 $ (234 ) Other comprehensive income (loss) before reclassifications 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 — — — (2 ) (2 ) Tax effect (18 ) 2 — — (16 ) Other comprehensive inco me (loss) 43 (41 ) — 1 3 Balance as of December 31, 2017 $ (190 ) $ (48 ) $ 4 $ 3 $ (231 ) (In millions) Pension Benefits Other Benefits Gain on Cash Flow Hedge Workers Compensation Total Balance as of December 31, 2017 $ (190 ) $ (48 ) $ 4 $ 3 $ (231 ) Other comprehensive income (loss) before reclassifications 14 27 (1 ) 9 49 Amounts reclassified from accumulated other comprehensive loss: Amortization – prior service credit (a) (33 ) (3 ) — — (36 ) – actuarial loss (a) 31 (1 ) — — 30 – settlement loss (a) 53 — — — 53 Other — — (1 ) (5 ) (6 ) Tax effect (7 ) 2 — 2 (3 ) Other comprehensive income (loss) 58 25 (2 ) 6 87 Balance as of December 31, 2018 $ (132 ) $ (23 ) $ 2 $ 9 $ (144 ) (a) These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 22 .

Defined Benefit Pension and Oth

Defined Benefit Pension and Other Postretirement Plans	12 Months Ended
	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [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 employees in our Retail segment 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. In connection with the Andeavor acquisition, we assumed a number of additional noncontributory benefit pension plans, covering substantially all former Andeavor employees. Benefits under these plans are determined based on final average compensation and years of service through December 31, 2010 and a cash balance formula for service beginning January 1, 2011. These plans were frozen as of December 31, 2018. We also assumed a number of additional postretirement benefits covering eligible employees. These benefits were merged with our existing benefits beginning January 1, 2019. Obligations and Funded Status The accumulated benefit obligation for all defined benefit pension plans was $2,632 million and $2,008 million as of December 31, 2018 and 2017 . The following summarizes our defined benefit pension plans that have accumulated benefit obligations in excess of plan assets. December 31, (In millions) 2018 2017 Projected benefit obligations $ 2,779 $ 2,164 Accumulated benefit obligations 2,632 2,008 Fair value of plan assets 2,089 1,840 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) 2018 2017 2018 2017 Change in benefit obligations: Benefit obligations at January 1 $ 2,164 $ 2,024 $ 826 $ 740 Service cost 159 132 30 25 Interest cost 83 75 30 30 Actuarial (gain) loss (159 ) 150 (71 ) 61 Benefits paid (273 ) (217 ) (36 ) (30 ) Plan amendments (90 ) — 34 — Acquisitions 895 — 71 — Benefit obligations at December 31 2,779 2,164 884 826 Change in plan assets: Fair value of plan assets at January 1 1,840 1,659 — — Actual return on plan assets (115 ) 270 — — Employer contributions 115 128 36 30 Benefits paid from plan assets (273 ) (217 ) (36 ) (30 ) Acquisitions 522 — — — Fair value of plan assets at December 31 2,089 1,840 — — Funded status of plans at December 31 $ (690 ) $ (324 ) $ (884 ) $ (826 ) Amounts recognized in the consolidated balance sheets: Current liabilities $ (21 ) $ (18 ) $ (44 ) $ (33 ) Noncurrent liabilities (669 ) (306 ) (840 ) (793 ) Accrued benefit cost $ (690 ) $ (324 ) $ (884 ) $ (826 ) Pretax amounts recognized in accumulated other comprehensive loss: (a) Net actuarial loss $ 517 $ 537 $ 9 $ 80 Prior service cost (credit) (295 ) (238 ) 35 (3 ) (a) Amounts exclude those related to LOOP and Explorer, equity method investees with defined benefit pension and postretirement plans for which net losses of $18 million and less than $1 million were recorded in accumulated other comprehensive loss in 2018 , 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) 2018 2017 2016 2018 2017 2016 Components of net periodic benefit cost: Service cost $ 159 $ 132 $ 114 $ 30 $ 25 $ 32 Interest cost 83 75 73 30 30 35 Expected return on plan assets (109 ) (100 ) (98 ) — — — Amortization – prior service credit (33 ) (39 ) (46 ) (3 ) (3 ) (3 ) – actuarial (gain) loss 31 36 38 (1 ) (2 ) 2 – settlement loss 53 52 7 — — — Net periodic benefit cost (a) $ 184 $ 156 $ 88 $ 56 $ 50 $ 66 Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax): Actuarial (gain) loss $ 64 $ (20 ) $ (33 ) $ (71 ) $ 61 $ (101 ) Prior service cost (credit) (90 ) — — 34 — — Amortization of actuarial gain (loss) (84 ) (88 ) (45 ) 1 2 (2 ) Amortization of prior service credit 33 39 46 3 3 3 Other — — — — — — Total recognized in other comprehensive loss $ (77 ) $ (69 ) $ (32 ) $ (33 ) $ 66 $ (100 ) Total recognized in net periodic benefit cost and other comprehensive loss $ 107 $ 87 $ 56 $ 23 $ 116 $ (34 ) (a) Net periodic benefit cost reflects a calculated market-related value of plan assets which recognizes changes in fair value over three years. Lump sum payments to employees retiring in 2018 , 2017 and 2016 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 2018 , 2017 and 2016 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 2019 are $18 million and $45 million , respectively. The estimated amount that will be amortized from accumulated other comprehensive loss into net periodic benefit cost in 2019 is less than $1 million for both the net actuarial gain and prior service credit for our other defined benefit postretirement plans. 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 2018 , 2017 and 2016 . Pension Benefits Other Benefits 2018 2017 2016 2018 2017 2016 Weighted-average assumptions used to determine benefit obligation: Discount rate 4.21 % 3.55 % 3.90 % 4.26 % 3.70 % 4.25 % Rate of compensation increase 5.00 % 5.00 % 5.00 % 5.00 % 5.00 % 5.00 % Weighted-average assumptions used to determine net periodic benefit cost: Discount rate 3.88 % 3.85 % 3.80 % 3.72 % 4.25 % 4.50 % Expected long-term return on plan assets 6.15 % 6.50 % 6.50 % — % — % — % Rate of compensation increase 4.80 % 5.00 % 5.00 % 5.00 % 5.00 % 5.00 % 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, 2018 2017 2016 Health care cost trend rate assumed for the following year: Medical: Pre-65 6.80 % 6.75 % 7.00 % Prescription drugs 9.50 % 8.75 % 9.00 % Rate to which the cost trend rate is assumed to decline (the ultimate trend rate): Medical: Pre-65 4.50 % 4.50 % 4.50 % Prescription drugs 4.50 % 4.50 % 4.50 % Year that the rate reaches the ultimate trend rate: Medical: Pre-65 2027 2026 2026 Prescription drugs 2027 2026 2026 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 34 (30 ) 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, 2018 , the primary plan’s targeted asset allocation was 42 percent equity, private equity, real estate, and timber securities and 58 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, 2018 and 2017 . 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. Other investments classified as Level 1 include mutual funds that are publicly registered, valued at NAV on a daily basis using a market approach. 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, 2018 and 2017 . December 31, 2018 (In millions) Level 1 Level 2 Level 3 Total Cash and cash equivalents $ — $ 25 $ — $ 25 Equity: Common stocks 89 86 — 175 Mutual funds 159 — — 159 Pooled funds — 297 — 297 Fixed income: Corporate 176 684 — 860 Government 98 141 — 239 Pooled funds — 201 — 201 Private equity — — 41 41 Real estate — — 29 29 Other 45 — 18 63 Total investments, at fair value $ 567 $ 1,434 $ 88 $ 2,089 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 The following is a reconciliation of the beginning and ending balances recorded for plan assets classified as Level 3 in the fair value hierarchy: 2018 (In millions) Private Equity Real Estate Other Total Beginning balance $ 51 $ 34 $ 20 $ 105 Actual return on plan assets: Realized 9 2 — 11 Unrealized 2 (1 ) — 1 Purchases 1 1 — 2 Sales (22 ) (7 ) (2 ) (31 ) Ending balance $ 41 $ 29 $ 18 $ 88 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 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 2018 , we made pension contributions totaling $115 million . We have no required funding for 2019 , 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 $19 million and $44 million , respectively, in 2019 . 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 2019 $ 238 $ 44 2020 254 46 2021 219 48 2022 218 50 2023 213 51 2024 through 2028 1,048 271 Contributions to defined contribution plans – We also contribute to several defined contribution plans for eligible employees. Contributions to these plans totaled $144 million , $116 million and $113 million in 2018 , 2017 and 2016 , 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 2018 , 2017 and 2016 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 2018 and 2017 is for the plan’s year ended December 31, 2017 and December 31, 2016 , 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 2018 , 2017 and 2016 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 2018 2017 2018 2017 2016 Central States, Southeast and Southwest Areas Pension Plan (a) 366044243 Red Red Implemented $ 4 $ 4 $ 4 No January 31, 2024 (a) This agreement has a minimum contribution requirement of $328 per week per employee for 2019 . A total of 258 employees participated in the plan as of December 31, 2018 . Multiemployer Health and Welfare Plan We contribute to one multiemployer health and welfare plan that covers both active employees and retirees. Through the health and welfare plan employees receive medical, dental, vision, prescription and disability coverage. Our contributions to this plan totaled $6 million , $7 million and $6 million for 2018 , 2017 and 2016 , respectively.

Stock-Based Compensation Plans

Stock-Based Compensation Plans	12 Months Ended
	Dec. 31, 2018
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”). In connection with the Andeavor acquisition, in October of 2018 we converted the outstanding option and equity incentive awards (other than awards held by non-employee directors of Andeavor, which awards were paid out in connection with the acquisition) under the Andeavor Plans to awards that provide for rights to acquire (in the case of options) or be settled in or otherwise determined in reference to shares of MPC common stock in place of shares of Andeavor common stock (in the case of equity incentive awards). As part of that conversion we used an exchange ratio for the respective share prices of Andeavor common stock and MPC common stock to ensure that the award holders’ economic opportunity remained constant, and for converted awards which included a performance component, performance was determined at the time of the conversion and the awards became subject to a time-based vesting only design. The converted awards otherwise continue to be subject to the terms and conditions of their award agreements and the applicable Andeavor Plan under which such awards were granted. The “Andeavor Plans” as to which the award conversions apply are: the Tesoro Corporation 2006 Long-Term Incentive Plan; the Andeavor Amended and Restated 2011 Long-Term Incentive Plan; the Andeavor 2018 Long-Term Incentive Plan; and the Amended and Restated Northern Tier Energy LP 2012 Long-Term Incentive 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 2018 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, including the converted awards related to the acquisition of Andeavor: (In millions) 2018 2017 2016 Stock-based compensation expense $ 133 $ 51 $ 45 Tax benefit recognized on stock-based compensation expense 32 19 17 Cash received by MPC upon exercise of stock option awards 24 46 10 Tax benefit received for tax deductions for stock awards exercised 14 25 4 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: 2018 2017 2016 Weighted average exercise price per share $ 67.71 $ 50.57 $ 35.27 Expected life in years 6.2 6.3 6.2 Expected volatility 34 % 35 % 38 % Expected dividend yield 3.0 % 3.0 % 3.0 % Risk-free interest rate 2.7 % 2.1 % 1.4 % Weighted average grant date fair value of stock option awards granted $ 17.21 $ 13.42 $ 9.84 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 2018 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 2018 : Number of of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Terms (in years) Aggregate Intrinsic Value (in millions) Outstanding at December 31, 2017 8,465,398 $ 33.74 Granted 903,797 67.71 Converted in acquisition 302,403 7.00 Exercised (916,566 ) 26.24 Forfeited or expired (30,437 ) 48.96 Outstanding at December 31, 2018 8,724,595 37.07 Vested and expected to vest at December 31, 2018 8,707,148 37.01 5.1 $ 199 Exercisable at December 31, 2018 6,586,859 31.42 4.0 182 The intrinsic value of options exercised by MPC employees during 2018 , 2017 and 2016 was $44 million , $75 million and $14 million , respectively. As of December 31, 2018 , unrecognized compensation cost related to stock option awards was $10 million , which is expected to be recognized over a weighted average period of 1.2 years. Restricted Stock Awards The following is a summary of restricted stock award activity of our common stock in 2018 : Shares of Restricted Stock (“RS”) Restricted Stock Units (“RSU”) Number of Shares Weighted Average Grant Date Fair Value Number of Units Weighted Average Grant Date Fair Value Outstanding at December 31, 2017 1,188,662 $ 45.07 285,164 $ 29.95 Granted 470,951 71.19 24,430 72.43 Converted in acquisition 16,972 82.43 4,452,751 82.43 RS Vested/RSUs Issued (624,934 ) 45.98 (526,254 ) 65.34 Forfeited (60,951 ) 50.27 (9,235 ) 82.43 Outstanding at December 31, 2018 990,700 57.23 4,226,856 80.96 Of the 4,226,856 restricted stock units outstanding, 1,106,740 are vested and have a weighted average grant date fair value of $76.90 . These vested but unissued units are held by our non-employee directors, certain of our officers and certain former officers and employees of Andeavor, are non-forfeitable and are issuable upon the director’s departure from our board of directors or officers end of employment with the company or, for certain former officers and employees of Andeavor, upon the expiration of a waiting period under Section 409A of the Code. 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 2018 $ 49 $ 71.19 $ 39 $ 72.43 2017 28 50.25 5 53.19 2016 17 36.17 8 40.85 As of December 31, 2018 , unrecognized compensation cost related to restricted stock awards was $35 million , which is expected to be recognized over a weighted average period of 1.2 years. Unrecognized compensation cost related to restricted stock unit awards was $110 million , which is expected to be recognized over a weighted average period of 1.10 years. Performance Unit Awards The following table presents a summary of the 2018 activity for performance unit awards to be settled in shares: Number of Units Weighted Average Grant Date Fair Value Outstanding at December 31, 2017 6,851,542 $ 0.81 Granted 3,830,000 0.83 Vested (2,052,959 ) 0.95 Forfeited (10,000 ) 0.92 Outstanding at December 31, 2018 8,618,583 0.79 The number of shares that would be issued upon target vesting, using the closing price of our common stock on December 31, 2018 would be 146,053 shares. As of December 31, 2018 , unrecognized compensation cost related to equity-classified performance unit awards was $3 million , which is expected to be recognized over a weighted average period of 1.3 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: 2018 2017 2016 Risk-free interest rate 2.3 % 1.5 % 1.0 % Look-back period (in years) 2.8 2.8 2.8 Expected volatility 34.0 % 36.1 % 34.2 % Grant date fair value of performance units granted $ 0.83 $ 0.92 $ 0.57 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 and ANDX Awards Compensation expense for awards related to MPLX and ANDX was not material to our consolidated financial statements for 2018.

Leases

Leases	12 Months Ended
	Dec. 31, 2018
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, 2018 , 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 2019 $ 70 $ 709 2020 71 619 2021 66 553 2022 75 389 2023 82 295 Later years 586 858 Total minimum lease payments 950 $ 3,423 Less imputed interest costs 301 Present value of net minimum lease payments $ 649 Operating lease rental expense was: (In millions) 2018 2017 2016 Rental expense $ 546 $ 367 $ 370
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 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 2038 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 2033. Our revenue from implicit lease arrangements, excluding executory costs, totaled approximately $221 million , $218 million and $246 million in 2018 , 2017 and 2016 , 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, 2018 , we received $10 million in contingent lease payments and $9 million for the year ended December 31, 2017 . The following is a schedule of minimum future rentals on the non‑cancellable operating leases as of December 31, 2018 : (In millions) 2019 $ 160 2020 159 2021 150 2022 148 2023 142 Later years 1,111 Total minimum lease payments $ 1,870 The following schedule summarizes our investment in assets held for operating lease by major classes as of December 31, 2018 : (In millions) Natural gas gathering and NGL transportation pipelines and facilities $ 965 Natural gas processing facilities 481 Terminal and related assets 133 Land, building, office equipment and other 43 Construction in progress 19 Property, plant and equipment 1,641 Less accumulated depreciation 219 Total property, plant and equipment $ 1,422

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES We are the subject of, or a party to, a number of pending or threatened legal actions, contingencies and commitments involving a variety of matters, including laws and regulations relating to the environment. Some of these matters are discussed below. For matters for which we have not recorded 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, 2018 and 2017 , accrued liabilities for remediation totaled $455 million and $114 million . The increase in accrued liabilities is mainly a result of assuming environmental obligations in connection with the Andeavor acquisition. 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 $35 million and $45 million at December 31, 2018 and 2017 , respectively. Governmental and other entities in California, New York, Maryland and Rhode Island have filed lawsuits against coal, gas, oil and petroleum companies, including the Company. The lawsuits allege damages as a result of climate change and the plaintiffs are seeking unspecified damages and abatement under various tort theories. Similar lawsuits may be filed in other jurisdictions. At this early stage, the ultimate outcome of these matters remain uncertain, and neither the likelihood of an unfavorable outcome nor the ultimate liability, if any, can be determined. We are involved in a number of environmental enforcement matters arising in the ordinary course of business. While the outcome and impact on us cannot be predicted with certainty, management believes the resolution of these environmental matters will not, individually or collectively, have a material adverse effect on our consolidated results of operations, financial position or cash flows. Litigation Relating to the Acquisition of Andeavor Between June 20 and July 11, 2018, six putative class actions (the “Actions”) were filed against some or all of Andeavor, the directors of Andeavor, and MPC, Mahi Inc. (“Merger Sub 1”) and Mahi LLC (n/k/a Andeavor LLC) (“Merger Sub 2” and, together with MPC and Merger Sub 1, the “MPC Defendants”), relating to the Andeavor merger. The Actions generally alleged that Andeavor, the directors of Andeavor and the MPC Defendants disseminated a false or misleading registration statement regarding the merger in violation of Section 14(a) of the Securities Exchange Act of 1934 (the “Exchange Act”) and Rule 14a-9 promulgated thereunder. The Actions further alleged that the directors of Andeavor and/or the MPC Defendants were liable for these violations as “controlling persons” of Andeavor under Section 20(a) of the Exchange Act. The Actions sought injunctive relief, including to enjoin and/or rescind the merger, damages in the event the merger is consummated, and an award of attorneys’ fees, in addition to other relief. The parties ultimately reached an agreement in principle to resolve the Actions in exchange for supplemental disclosures. Consistent with that agreement, Andeavor and MPC each filed a Current Report on Form 8-K on September 14, 2018 that included certain additional disclosures in response to plaintiffs’ allegations. Between September 21 and September 28, 2018, all the Actions were dismissed as moot, and the parties reserved their rights in the event of any dispute over attorneys’ fees and expenses. In the fourth quarter of 2018, the Company resolved the remaining disputes over attorneys’ fees for an amount that was not material to the Company. Other Lawsuits In May 2015, the Kentucky attorney general filed a lawsuit against our wholly-owned subsidiary, MPC LP, in the United States District Court for the Western District of Kentucky asserting claims under federal and state antitrust statutes, the Kentucky Consumer Protection Act, and state common law. The complaint, as amended in July 2015, alleges that MPC LP used deed restrictions, supply agreements with customers and exchange agreements with competitors to unreasonably restrain trade in areas within Kentucky and seeks declaratory relief, unspecified damages, civil penalties, restitution and disgorgement of profits. At this stage, the ultimate outcome of this litigation remains uncertain, and neither the likelihood of an unfavorable outcome nor the ultimate liability, if any, can be determined, and we are unable to estimate a reasonably possible loss (or range of loss) for this matter. We intend to vigorously defend ourselves in this matter. In May 2007, the Kentucky attorney general filed a lawsuit against us and Marathon Oil in state court in Franklin County, Kentucky for alleged violations of Kentucky’s emergency pricing and consumer protection laws following Hurricanes Katrina and Rita in 2005. The lawsuit alleges that we overcharged customers by $89 million during September and October 2005 . The complaint seeks disgorgement of these sums, as well as penalties, under Kentucky’s emergency pricing and consumer protection laws. We are vigorously defending this litigation. We believe that this is the first lawsuit for damages and injunctive relief under the Kentucky emergency pricing laws to progress this far and it contains many novel issues. In May 2011, the Kentucky attorney general amended his complaint to include a request for immediate injunctive relief as well as unspecified damages and penalties related to our wholesale gasoline pricing in April and May 2011 under statewide price controls that were activated by the Kentucky governor on April 26, 2011 and which have since expired. The court denied the attorney general’s request for immediate injunctive relief, and the remainder of the 2011 claims likely will be resolved along with those dating from 2005. If the lawsuit is resolved unfavorably in its entirety, it could materially impact our consolidated results of operations, financial position or cash flows. However, management does not believe the ultimate resolution of this litigation will have a material adverse effect on our consolidated financial position, results of operations, or cash flows. We are also a party to a number of other lawsuits and other proceedings arising in the ordinary course of business. While the ultimate outcome and impact to us cannot be predicted with certainty, we believe that the resolution of these other lawsuits and proceedings will not have a material adverse effect on our consolidated financial position, results of operations or cash flows. Guarantees We have provided certain guarantees, direct and indirect, of the indebtedness of other companies. Under the terms of most of these guarantee arrangements, we would be required to perform should the guaranteed party fail to fulfill its obligations under the specified arrangements. In addition to these financial guarantees, we also have various performance guarantees related to specific agreements. Guarantees related to indebtedness of equity method investees – MPC and MPLX hold interests in an offshore oil port, LOOP, and MPLX holds an interest in a crude oil pipeline system, LOCAP. Both LOOP and LOCAP have secured various project financings with throughput and deficiency agreements. Under the agreements, MPC, as a shipper, is required to advance funds if the investees are unable to service their debt. Any such advances are considered prepayments of future transportation charges. The duration of the agreements vary but tend to follow the terms of the underlying debt, which extend through 2037 . Our maximum potential undiscounted payments under these agreements for the debt principal totaled $171 million as of December 31, 2018 . 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, 2018 , our maximum potential undiscounted payments under this agreement for debt principal totaled $163 million . In connection with our 50 percent indirect interest in Crowley Blue Water Partners, we have agreed to provide a conditional guarantee of up to 50 percent of its outstanding debt balance in the event there is no charter agreement in place with an investment-grade customer for the entity’s three vessels as well as other financial support in certain circumstances. The maximum exposure under these arrangements is 50 percent of the amount of the debt, which was $128 million as of December 31, 2018 . 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, 2018 , which consist of unrecognized tax benefits related to MPC, its consolidated subsidiaries and the refining, marketing and transportation 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 $123 million as of December 31, 2018 , which consist primarily of a commitment to contribute cash to an equity method investee for certain catastrophic events in lieu of procuring insurance coverage and leases of assets containing general lease indemnities and guaranteed residual values. General guarantees associated with dispositions – Over the years, we have sold various assets in the normal course of our business. Certain of the related agreements contain performance and general guarantees, including guarantees regarding inaccuracies in representations, warranties, covenants and agreements, and environmental and general indemnifications that require us to perform upon the occurrence of a triggering event or condition. These guarantees and indemnifications are part of the normal course of selling assets. We are typically not able to calculate the maximum potential amount of future payments that could be made under such contractual provisions because of the variability inherent in the guarantees and indemnities. Most often, the nature of the guarantees and indemnities is such that there is no appropriate method for quantifying the exposure because the underlying triggering event has little or no past experience upon which a reasonable prediction of the outcome can be based. Contractual Commitments and Contingencies At December 31, 2018 and 2017 , our contractual commitments to acquire property, plant and equipment and advance funds to equity method investees totaled $1.8 billion and $484 million . Certain natural gas processing and gathering arrangements require us to construct natural gas processing plants, natural gas gathering pipelines and NGL pipelines and contain certain fees and charges if specified construction milestones are not achieved for reasons other than force majeure. In certain cases, certain producer customers may have the right to cancel the processing arrangements if there are significant delays that are not due to force majeure.

Selected Quarterly Financial Da

Selected Quarterly Financial Data	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Data [Abstract]
Selected Quarterly Financial Data	SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) 2018 2017 (In millions, except per share data) 1st Qtr. 2nd Qtr. 3rd Qtr. 4th Qtr. 1st Qtr. 2nd Qtr. 3rd Qtr. 4th Qtr. (a) Sales and other operating revenues (b) $ 18,866 $ 22,317 $ 22,988 $ 32,333 $ 16,288 $ 18,180 $ 19,210 $ 21,055 Income from operations 440 1,711 1,403 2,017 291 982 1,577 1,168 Net income 235 1,235 941 1,195 101 574 1,004 2,125 Net income attributable to MPC 37 1,055 737 951 30 483 903 2,016 Net income attributable to MPC per share (c) : Basic $ 0.08 $ 2.30 $ 1.63 $ 1.38 $ 0.06 $ 0.94 $ 1.79 $ 4.13 Diluted 0.08 2.27 1.62 1.35 0.06 0.93 1.77 4.09 (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. (b) Includes sales to related parties. The 2018 periods reflect an election to present certain taxes on a net basis concurrent with our adoption of ASC 606. (c) The sum of the per-share amounts for the four quarters may not always equal the annual per-share amounts due to differences in the average number of shares outstanding during the respective periods.

Summary Of Principal Accounti_2

Summary Of Principal Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Principles applied in consolidation	Principles Applied in Consolidation These consolidated financial statements include the accounts of our majority-owned, controlled subsidiaries, MPLX and ANDX. 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, 2018 , we owned 63.6 percent of the outstanding MPLX common units and 63.6 percent of the outstanding ANDX common units and 100 percent of the general partner interest for each entity. Due to our ownership of the general partner interest, we have determined that we control MPLX and ANDX and therefore we consolidate MPLX and ANDX and record a noncontrolling interest for the 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 We recognize revenue based on consideration specified in contracts or agreements with customers when we satisfy our performance obligations by transferring control over products or services to a customer. Concurrent with our adoption of ASU 2014-09, Revenue from Contracts with Customers (“ASC 606”), we made an accounting policy election that all taxes assessed by a governmental authority that are both imposed on and concurrent with a revenue-producing transaction and collected from our customers will be recognized on a net basis within sales and other operating revenues. The adoption of ASC 606 did not materially change our revenue recognition patterns, which are described below by reportable segment: • Refining & Marketing - The vast majority of our Refining & Marketing contracts contain pricing that is based on the market price for the product at the time of delivery. Our obligations to deliver product volumes are typically satisfied and revenue is recognized when control of the product transfers to our customers. Concurrent with the transfer of control, we typically receive the right to payment for the delivered product, the customer accepts the product and the customer has significant risks and rewards of ownership of the product. Payment terms require customers to pay shortly after delivery and do not contain significant financing components. • Retail - Revenue is recognized when our customers receive control of the transportation fuels or merchandise. Payments from customers are received at the time sales occur in cash or by credit or debit card at our company-owned and operated retail locations and shortly after delivery for our direct dealers. Our retail operations offer a loyalty rewards program to its customers. We defer a minor portion of revenue on sales to the loyalty program participants until the participants redeem their rewards. The related contract liability, as defined in ASC 606, is not material to our financial statements. • Midstream - Midstream revenue transactions typically are defined by contracts under which we sell a product or provide a service. Revenues from sales of product are recognized when control of the product transfers to the customer. Revenues from sales of services are recognized over time when the performance obligation is satisfied as services are provided in a series. We have elected to use the output measure of progress to recognize revenue based on the units delivered, processed or transported. The transaction prices in our Midstream contracts often have both fixed components, related to minimum volume commitments, and variable components, which are primarily dependent on volumes. Variable consideration will generally not be estimated at contract inception as the transaction price is specifically allocable to the services provided at each period end. Refer to Note 10 for disclosure of our revenue disaggregated by segment and product line, as well as a description of our reportable segment operations.
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. No revenues are recorded for exchange and matching buy/sell transactions as they are accounted for as exchanges of inventory. The exchange transactions are recognized at the carrying amount of the inventory transferred.
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
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. We mitigate credit risk with master netting agreements with 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 51 years. Such assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset group may not be recoverable. If the sum of the expected undiscounted future cash flows from the use of the asset group and its eventual disposition is less than the carrying amount of the asset group, an impairment assessment is performed and the excess of the book value over the fair value of the asset group 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. The fair value is calculated using the expected present value of future cash flows method. Significant assumptions used in the cash flow forecasts include future net operating margins, future volumes, discount rates, and future capital requirements. If the carrying amount of the reporting unit exceeds its fair value, an impairment loss shall be recognized in an amount equal to that excess, limited to the total amount of goodwill allocated to that reporting unit. 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 and other major maintenance 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 for additional equipment that mitigates or prevents future contamination or improves environmental safety or efficiency of the existing assets are capitalized. 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. Our short-term asset retirement obligations were $30 million and $6 million at December 31, 2018 and 2017 , respectively, which are included in other current liabilities in our consolidated balance sheets. Our long-term asset retirement obligations were $222 million and $121 million at December 31, 2018 and 2017 , respectively, which are included in deferred credits and other liabilities in our consolidated balance sheets. The increase in our asset retirement obligation was mainly due to obligations recognized in connection with the purchase accounting for the Andeavor acquisition. 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. Any excess or surplus of the purchase consideration when compared to the fair value of the net tangible assets acquired, if any, is 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. 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. 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 date, 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 that would have existed as of the date of the acquisition. Any adjustment that arises from information obtained that did not exist as of the date of the acquisition will be recorded in the period of the adjustment. Acquisition-related costs are expensed as incurred in connection with each business combination.
Environmental credits and obligations	Environmental Credits and Obligations In order to comply with certain regulations, specifically the RFS2 requirements implemented by the EPA and the cap-and-trade emission reduction program and low carbon fuel standard implemented by the state of California, we are required to reduce our emissions, blend certain levels of biofuels or obtain allowances or credits to offset the obligations created by our operations. In regard to each program, we record an asset, included in other current or other noncurrent assets on the balance sheet, for allowances or credits owned in excess of our anticipated current period compliance requirements. The asset value is based on the product of the excess allowances or credits as of the balance sheet date, if any, and the weighted average cost of those allowances or credits. We record a liability, included in other current or other noncurrent liabilities on the balance sheet, when we are deficient allowances or credits based on the product of the deficient amount as of the balance sheet date, if any, and the market price of the allowances or credits at the balance sheet date. The cost of allowances or credits used for compliance is reflected in cost of revenues on the income statement. Any gains or losses on the sale or expiration of allowances or credits are classified as other income on the income statement. Proceeds from offset or credits sales are included in investing activities - all other, net on the cash flow statement.

Master Limited Partnerships (Ta

Master Limited Partnerships (Tables)	12 Months Ended
	Dec. 31, 2018
Noncontrolling Interest [Abstract]
Noncontrolling Interest	As a result of equity transactions of MPLX and ANDX, we are required to adjust non-controlling interest and additional paid-in capital. Changes in MPC’s additional paid-in capital resulting from changes in its ownership interest in MPLX and ANDX were as follows: (In millions) 2018 2017 2016 Increase (decrease) due to the issuance of MPLX & ANDX common units to the public $ 6 $ 25 $ (60 ) Increase due to the issuance of MPLX & ANDX common units and general partner units to MPC 1,114 114 121 Increase due to GP/IDR Exchange 1,808 — — Increase in MPC's additional paid-in capital 2,928 139 61 Tax impact (571 ) (29 ) (118 ) Increase (decrease) in MPC's additional paid-in capital, net of tax $ 2,357 $ 110 $ (57 )

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Components of the Fair Value of Consideration Transferred [Table Text Block]	The components of the fair value of consideration transferred are as follows: (In millions) Fair value of MPC shares issued $ 19,766 Cash payment to Andeavor stockholders 3,486 Cash settlement of non-employee director units 7 Fair value of converted equity awards 203 Total fair value of consideration transferred $ 23,462
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	We accounted for the Andeavor acquisition using the acquisition method of accounting, which requires Andeavor assets and liabilities to be recorded to our balance sheet at fair value as of the acquisition date. We will complete a final determination of the fair value of certain assets and liabilities within the one year measurement period from the date of the acquisition as required by FASB ASC Topic 805, “Business Combinations”. Due to the level of effort required to develop fair value measurements and the proximity of the acquisition date to December 31, 2018, the valuation studies necessary to determine the fair value of assets acquired and liabilities assumed are preliminary, including the underlying cash flows used to determine the fair value of identified intangible assets and economic obsolescence adjustments to property, plant and equipment. The size and the breath of the Andeavor acquisition necessitates the use of the one year measurement period to fully analyze all the factors used in establishing the asset and liability fair values as of the acquisition date, including, but not limited to, property, plant and equipment, intangible assets, real property, leases, environmental and asset retirement obligations and the related tax impacts of any changes made. Any potential adjustments made could be material in relation to the preliminary values presented below. (In millions) Cash and cash equivalents $ 382 Receivables 2,744 Inventories 5,204 Other current assets 378 Equity method investments 865 Property, plant and equipment, net 16,545 Other noncurrent assets (a) 3,086 Total assets acquired 29,204 Accounts payable 4,003 Payroll and benefits payable 348 Accrued taxes 590 Debt due within one year 34 Other current liabilities 392 Long-term debt 8,875 Deferred income taxes 1,609 Defined benefit postretirement plan obligations 432 Deferred credit and other liabilities 714 Noncontrolling interests 5,059 Total liabilities and noncontrolling interest assumed 22,056 Net assets acquired excluding goodwill 7,148 Goodwill 16,314 Net assets acquired $ 23,462
Business Acquisition, Pro Forma Information	The following unaudited pro forma financial information presents consolidated results assuming the Andeavor acquisition occurred on January 1, 2017. (In millions, except per share data) 2018 2017 Sales and other operating revenues (a) $ 131,695 $ 117,549 Net income attributable to MPC 4,371 4,832 Net income attributable to MPC per share – basic $ 8.44 $ 6.47 Net income attributable to MPC per share – diluted 8.31 6.41 (a) The 2018 period reflects an election to present certain taxes on a net basis concurrent with our adoption of ASC 606.

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	12 Months Ended
	Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Summarized Balance Sheet Information of VIEs	The assets of MPLX and ANDX can only be used to settle their own obligations and their creditors have no recourse to our assets. The following table present balance sheet information for the assets and liabilities of MPLX and ANDX, which are included in our balance sheets. December 31, December 31, (In millions) MPLX ANDX (a) MPLX Assets Cash and cash equivalents $ 68 $ 10 $ 5 Receivables, less allowance for doubtful accounts 425 199 299 Inventories 77 22 65 Other current assets 45 57 29 Equity method investments 4,174 602 4,010 Property, plant and equipment, net 14,639 6,845 12,187 Goodwill 2,586 1,051 2,245 Other noncurrent assets 458 1,242 479 Liabilities Accounts payable $ 776 $ 215 $ 621 Payroll and benefits payable 2 10 1 Accrued taxes 48 23 38 Debt due within one year 1 504 1 Other current liabilities 177 77 130 Long-term debt 13,392 4,469 6,945 Deferred income taxes 13 1 5 Defined benefit postretirement plan obligations — — — Deferred credits and other liabilities 276 68 230 (a) The balances reflected here are ANDX’s historical balances as the preliminary purchase accounting adjustments related to ANDX’s assets and liabilities in connection with the Andeavor acquisition and reflected on our consolidated balance sheet as of December 31, 2018 have not yet been pushed down to this subsidiary.

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Schedule of Related Party Transactions [Table Text Block]	Transactions with related parties were as follows: (In millions) 2018 2017 2016 Sales to related parties (a) $ 754 $ 629 $ 62 Purchases from related parties (b) 610 570 509 (a) Sales to related parties consists primarily of sales of refined products to PFJ Southeast, an equity affiliate which owns and operates travel plazas primarily in the Southeast region of the United States. (b) We obtain transportation services and purchase ethanol from certain of our equity affiliates, none of which is individually material.

Income per Common Share (Tables

Income per Common Share (Tables)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Summary of Earnings Per Common Share	Since MPC grants certain incentive compensation awards to employees and non-employee directors that are considered to be participating securities, we have calculated our earnings per share using the two-class method. Diluted income per share assumes exercise of certain stock-based compensation awards, provided the effect is not anti-dilutive. (In millions, except per share data) 2018 2017 2016 Basic earnings per share: Allocation of earnings: Net income attributable to MPC $ 2,780 $ 3,432 $ 1,174 Income allocated to participating securities 1 2 1 Income available to common stockholders – basic $ 2,779 $ 3,430 $ 1,173 Weighted average common shares outstanding 518 507 528 Basic earnings per share $ 5.36 $ 6.76 $ 2.22 Diluted earnings per share: Allocation of earnings: Net income attributable to MPC $ 2,780 $ 3,432 $ 1,174 Income allocated to participating securities 1 2 1 Income available to common stockholders – diluted $ 2,779 $ 3,430 $ 1,173 Weighted average common shares outstanding 518 507 528 Effect of dilutive securities 8 5 2 Weighted average common shares, including dilutive effect 526 512 530 Diluted earnings per share $ 5.28 $ 6.70 $ 2.21
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) 2018 2017 2016 Shares issuable under stock-based compensation plans — 1 3

Equity (Tables)

Equity (Tables)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Share Repurchases	Total share repurchases were as follows for the respective periods: (In millions, except per share data) 2018 2017 2016 Number of shares repurchased 47 44 4 Cash paid for shares repurchased $ 3,287 $ 2,372 $ 197 Average cost per share $ 69.46 $ 53.85 $ 41.84

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Income From Operations Attributable To Operating Segments	Segment income represents income from operations attributable to the reportable segments. Corporate administrative expenses, except for those attributable to MPLX and ANDX, 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 the third quarter of 2018, we began reporting segment capital expenditures and investments excluding acquisitions in the current and comparative periods. (In millions) Refining & Marketing Retail Midstream Total Year Ended December 31, 2018 Revenues: Third party $ 68,939 $ 23,538 $ 3,273 $ 95,750 Intersegment 12,914 6 3,387 16,307 Related party 746 8 — 754 Segment revenues $ 82,599 $ 23,552 $ 6,660 $ 112,811 Segment income from operations $ 2,481 $ 1,028 $ 2,752 $ 6,261 Income from equity method investments (b) 15 74 274 363 Depreciation and amortization (b) 1,174 353 885 2,412 Capital expenditures and investments (c) 1,057 460 2,630 4,147 (In millions) Refining & Marketing Retail 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 $ 729 $ 1,339 $ 4,389 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) 832 381 1,755 2,968 (In millions) Refining & Marketing Retail 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 (d) $ 1,357 $ 733 $ 1,048 $ 3,138 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 1,558 2,915 (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 and investments in affiliates. (e) In 2016, the Refining & Marketing and Retail segments include an inventory LCM benefit of $345 million and $25 million , respectively.
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) 2018 2017 2016 Segment income from operations $ 6,261 $ 4,389 $ 3,138 Items not allocated to segments: Corporate and other unallocated items (a) (502 ) (365 ) (266 ) Transaction-related costs (197 ) — — Litigation — (29 ) — Impairments (b) 9 23 (486 ) Income from operations 5,571 4,018 2,386 Net interest and other financial costs 1,003 674 564 Income before income taxes $ 4,568 $ 3,344 $ 1,822 (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 and ANDX, which are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Retail segments. (b) 2018 and 2017 includes MPC’s share of gains from the the sale of assets remaining from the canceled Sandpiper pipeline project. 2016 includes impairments of goodwill and equity method investments. See Note 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) 2018 2017 2016 Segment capital expenditures and investments $ 4,147 $ 2,968 $ 2,915 Less investments in equity method investees 409 305 288 Plus items not allocated to segments: Corporate 77 83 81 Capitalized interest 80 55 63 Total capital expenditures (a) $ 3,895 $ 2,801 $ 2,771 (a) 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) 2018 2017 2016 Refined products $ 83,888 $ 63,846 $ 54,450 Merchandise 5,332 5,174 5,297 Crude oil and refinery feedstocks 4,143 3,403 2,038 Midstream services, transportation and other 2,387 1,681 1,492 Sales and other operating revenues (a) $ 95,750 $ 74,104 $ 63,277

Net Interest and Other Financ_2

Net Interest and Other Financial Costs (Tables)	12 Months Ended
	Dec. 31, 2018
Other Income and Expenses [Abstract]
Net Interest And Other Financial Income (Costs)	Net interest and other financial costs was: (In millions) 2018 2017 2016 Interest income $ (87 ) $ (27 ) $ (6 ) Interest expense 1,026 688 602 Interest capitalized (80 ) (63 ) (64 ) Pension and other postretirement non-service costs (a) 53 49 8 Loss on extinguishment of debt 64 — — Other financial costs 27 27 24 Net interest and other financial costs $ 1,003 $ 674 $ 564 (a) See Note 22 .

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Components Of Income Tax Provisions (Benefits)	Income tax provisions (benefits) were: 2018 2017 2016 (In millions) Current Deferred Total Current Deferred Total Current Deferred Total Federal $ 715 $ 2 $ 717 $ 681 $ (1,270 ) $ (589 ) $ 189 $ 336 $ 525 State and local 178 61 239 98 33 131 27 57 84 Foreign 22 (16 ) 6 (6 ) 4 (2 ) (1 ) 1 — Total $ 915 $ 47 $ 962 $ 773 $ (1,233 ) $ (460 ) $ 215 $ 394 $ 609
Reconciliation Of Federal Statutory Income Tax Rate	A reconciliation of the federal statutory income tax rate applied to income before income taxes to the provision for income taxes follows: 2018 2017 2016 Statutory rate applied to income before income taxes 21 % 35 % 35 % State and local income taxes, net of federal income tax effects 4 2 3 Domestic manufacturing deduction — (1 ) (1 ) Noncontrolling interests (4 ) (4 ) (1 ) Biodiesel excise tax credit — — (1 ) TCJA legislation — (45 ) — Other — (1 ) (2 ) Provision for income taxes 21 % (14 )% 33 %
Components Of Deferred Tax Assets And Liabilities	Deferred tax assets and liabilities resulted from the following: December 31, (In millions) 2018 2017 Deferred tax assets: Employee benefits $ 660 $ 348 Environmental remediation 111 16 Debt financing 39 — Net operating loss carryforwards 17 12 Foreign currency 28 13 Tax credit carryforwards 21 — Other 88 31 Total deferred tax assets 964 420 Deferred tax liabilities: Property, plant and equipment 2,830 1,603 Inventories 678 473 Investments in subsidiaries and affiliates 2,130 912 Intangibles 97 70 Other 64 3 Total deferred tax liabilities 5,799 3,061 Net deferred tax liabilities $ 4,835 $ 2,641 The increase in net deferred tax liabilities is primarily related to the revaluation of MPC’s legacy deferred tax liabilities and the recognition of net deferred tax liabilities both as a result of the Andeavor acquisition.
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) 2018 2017 Assets: Other noncurrent assets $ 29 $ 13 Liabilities: Deferred income taxes 4,864 2,654 Net deferred tax liabilities $ 4,835 $ 2,641
Summary Of Income Tax Returns Subject To Examination	As of December 31, 2018 , our income tax returns remain subject to examination in the following major tax jurisdictions for the tax years indicated: United States Federal 2009 - 2017 States 2006 - 2017
Summary Of Activity In Unrecognized Tax Benefits	The following table summarizes the activity in unrecognized tax benefits: (In millions) 2018 2017 2016 January 1 balance $ 19 $ 7 $ 12 Additions for tax positions of prior years — 13 6 Reductions for tax positions of prior years (5 ) — (10 ) Settlements — (1 ) (1 ) Statute of limitations (12 ) — — Acquired from Andeavor 209 — — December 31 balance $ 211 $ 19 $ 7

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2018
Inventory Disclosure [Abstract]
Summary Of Inventories	December 31, (In millions) 2018 2017 Crude oil and refinery feedstocks $ 3,655 $ 2,056 Refined products 5,234 2,839 Materials and supplies 720 494 Merchandise 228 161 Total $ 9,837 $ 5,550

Equity Method Investments (Tabl

Equity Method Investments (Tables)	12 Months Ended
	Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Schedule Of Equity Method Investments	Ownership as of Carrying value at December 31, December 31, (Dollars in millions) 2018 2018 2017 R&M Watson Cogeneration Company 51% $ 84 $ — Other 121 104 R&M Total $ 205 $ 104 Retail PFJ Southeast LLC 29% $ 341 $ 328 Retail Total $ 341 $ 328 Midstream Andeavor Logistics Rio Pipeline LLC 67% $ 181 $ — Centrahoma Processing LLC 40% 160 121 Crowley Coastal Partners, LLC 50% 190 188 Illinois Extension Pipeline Company, L.L.C 35% 275 284 LOOP LLC 51% 282 282 MarEn Bakken Company LLC 25% 498 520 MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C. 67% 236 164 MarkWest Utica EMG 56% 2,039 2,139 Minnesota Pipe Line Company, LLC 17% 197 — Rendezvous Gas Services, L.L.C. 78% 248 — Sherwood Midstream Holdings LLC (a) 60% 157 165 Sherwood Midstream LLC 50% 366 236 Other 523 256 Midstream Total $ 5,352 $ 4,355 Total $ 5,898 $ 4,787 (a) Excludes Sherwood Midstream LLC’s investment in Sherwood Midstream Holdings LLC.
Summarized Financial Information For Equity Method Investees	Summarized financial information for all equity method investments in affiliated companies, combined, was as follows: (In millions) 2018 2017 2016 Income statement data: Revenues and other income $ 7,726 $ 6,235 $ 2,421 Income (loss) from operations 1,375 1,075 (116 ) Net income (loss) 1,242 922 (250 ) Balance sheet data – December 31: Current assets $ 1,443 $ 860 Noncurrent assets 12,408 10,854 Current liabilities 1,857 547 Noncurrent liabilities 1,788 1,714

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Summary Of Property, Plant And Equipment	(In millions) Estimated Useful Lives December 31, 2018 2017 Refining & Marketing 4 - 30 years $ 27,590 $ 19,490 Retail 4 - 25 years 6,637 5,358 Midstream 3 - 51 years 25,692 14,898 Corporate and Other 4 - 40 years 1,294 792 Total 61,213 40,538 Less accumulated depreciation 16,155 14,095 Property, plant and equipment, net $ 45,058 $ 26,443

Goodwill and Intangibles (Table

Goodwill and Intangibles (Tables)	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in Carrying Amount of Goodwill	The changes in the carrying amount of goodwill for 2017 and 2018 were as follows: (In millions) Refining & Marketing Retail Midstream Total Balance at January 1, 2017 $ 519 $ 792 $ 2,276 $ 3,587 Disposition — (1 ) — (1 ) Balance at December 31, 2017 $ 519 $ 791 $ 2,276 $ 3,586 Acquisitions 4,717 4,050 7,831 16,598 Transfer of assets related to dropdowns (216 ) — 216 — Balance at December 31, 2018 $ 5,020 $ 4,841 $ 10,323 $ 20,184
Schedule of Acquired Finite-Lived Intangible Assets by Major Class	Our finite-lived intangible assets as of December 31, 2018 and 2017 are as shown below. The increases in 2018 reflect preliminary estimates for customer contracts and relationships as well as brand rights and tradenames acquired in the the Andeavor acquisition. December 31, 2018 December 31, 2017 (In millions) Gross Accumulated Amortization Net Gross Accumulated Amortization Net Customer contracts and relationships $ 3,184 $ 261 $ 2,923 $ 654 $ 139 $ 515 Brand rights and tradenames 208 33 175 25 24 1 Royalty agreements 129 70 59 129 63 66 Other 190 33 157 84 35 49 Total $ 3,711 $ 397 $ 3,314 $ 892 $ 261 $ 631
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	Estimated future amortization expense related to the intangible assets at December 31, 2018 is as follows: (In millions) 2019 $ 387 2020 385 2021 379 2022 378 2023 361

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Assets and Liabilities Accounted for at Fair Value on Recurring Basis	The following tables present assets and liabilities accounted for at fair value on a recurring basis as of December 31, 2018 and 2017 by fair value hierarchy level. We have elected to offset the fair value amounts recognized for multiple derivative contracts executed with the same counterparty, including any related cash collateral as shown below; however, fair value amounts by hierarchy level are presented on a gross basis in the following tables. December 31, 2018 Fair Value Hierarchy (In millions) Level 1 Level 2 Level 3 Netting and Collateral (a) Net Carrying Value on Balance Sheet (b) Collateral Pledged Not Offset Commodity derivative instruments, assets $ 370 $ 31 $ — $ (323 ) $ 78 $ 2 Total assets at fair value $ 370 $ 31 $ — $ (323 ) $ 78 $ 2 Commodity derivative instruments, liabilities $ 255 $ 37 $ — $ (284 ) $ 8 $ — Embedded derivatives in commodity contracts — — 61 — 61 — Total liabilities at fair value $ 255 $ 37 $ 61 $ (284 ) $ 69 $ — 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 — — 64 — 64 — Total liabilities at fair value $ 126 $ — $ 66 $ (126 ) $ 66 $ — (a) Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of December 31, 2018 , cash collateral of $52 million was netted with mark-to-market derivative assets and $13 million was netted with mark-to-market liabilities. As of December 31, 2017 , cash collateral of $8 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.
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 liabilities classified as Level 3 in the fair value hierarchy. (In millions) 2018 2017 Beginning balance $ 66 $ 190 Contingent consideration payment — (131 ) Unrealized and realized losses included in net income 3 25 Settlements of derivative instruments (8 ) (18 ) Ending balance $ 61 $ 66 The amount of total losses for the period included in earnings attributable to the change in unrealized losses relating to assets still held at the end of period: Derivative instruments $ 8 $ 8 Contingent consideration agreement — 1 Total $ 8 $ 9

Derivatives (Tables)

Derivatives (Tables)	12 Months Ended
	Dec. 31, 2018
Summary of Derivative Instruments [Abstract]
Classification of Fair Values of Derivative Instruments, Excluding Cash Collateral	The following table presents the fair value of derivative instruments as of December 31, 2018 and 2017 and the line items in the balance sheets in which the fair values are reflected. The fair value amounts below are presented on a gross basis and do not reflect the netting of asset and liability positions permitted under the terms of our master netting arrangements including cash collateral on deposit with, or received from, brokers. We offset the recognized fair value amounts for multiple derivative instruments executed with the same counterparty in our financial statements when a legal right of offset exists. As a result, the asset and liability amounts below will not agree with the amounts presented in our consolidated balance sheets. (In millions) December 31, 2018 Balance Sheet Location Asset Liability Commodity derivatives Other current assets $ 400 $ 283 Other current liabilities (a) 1 16 Deferred credits and other liabilities (a) — 54 (In millions) December 31, 2017 Balance Sheet Location Asset Liability Commodity derivatives Other current assets $ 127 $ 126 Other current liabilities (a) — 14 Deferred credits and other liabilities (a) — 52 (a) Includes embedded derivatives.
Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block]	The table below summarizes open commodity derivative contracts for crude oil, refined products and blending products as of December 31, 2018 . Percentage of contracts that expire next quarter Position (Units in thousands of barrels) Long Short Exchange-traded (a) Crude oil 71.5% 40,257 44,709 Refined products 75.9% 10,210 11,149 Blending products 70.3% 5,194 7,356 OTC Crude oil —% 880 — Blending products 24.1% 2,480 2,480 (a) Included in exchange-traded are spread contracts in thousands of barrels: Crude oil - 7,470 long and 6,800 short; Refined products - 450 long and 450 short; Blending products - 2,678 long and 2,767 short
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 2018 2017 2016 Sales and other operating revenues $ 13 $ 5 $ (13 ) Cost of revenues (59 ) (26 ) (167 ) Total $ (46 ) $ (21 ) $ (180 )

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Outstanding Borrowings	Our outstanding borrowings at December 31, 2018 and 2017 consisted of the following: December 31, (In millions) 2018 2017 Marathon Petroleum Corporation: Commercial paper $ — $ — 364-day bank revolving credit facility due September 2019 — — Trade receivables securitization facility due July 2019 — — Bank revolving credit facility due October 2023 — — Senior notes, 2.700% due December 2018 — 600 Senior notes, 3.400% due December 2020 650 650 Senior notes, 5.125% due March 2021 1,000 1,000 Senior notes, 5.375% due October 2022 337 — Senior notes, 4.750% due December 2023 614 — Senior notes, 5.125% due April 2024 241 — Senior notes, 3.625%, due September 2024 750 750 Senior notes, 5.125% due December 2026 719 — Senior notes, 3.800% due April 2028 496 — 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, 4.500% due April 2048 498 — Andeavor senior notes, 3.800% - 5.375% due 2022 - 2048 469 — Senior notes, 5.000%, due September 2054 400 400 Capital lease obligations due 2019-2033 629 356 December 31, (In millions) 2018 2017 Notes payable 11 — MPLX LP: MPLX bank revolving credit facility due 2022 — 505 MPLX senior notes, 5.500% due February 2023 — 710 MPLX senior notes, 3.375% due March 2023 500 — MPLX senior notes, 4.500% due July 2023 989 989 MPLX senior notes, 4.875% due December 2024 1,149 1,149 MPLX senior notes, 4.000% due February 2025 500 500 MPLX senior notes, 4.875% due June 2025 1,189 1,189 MarkWest senior notes, 4.500% - 5.500% due 2023 - 2025 23 63 MPLX senior notes, 4.125% due March 2027 1,250 1,250 MPLX senior notes, 4.000% due March 2028 1,250 — MPLX senior notes, 4.800% due February 2029 750 — MPLX senior notes, 4.500% due April 2038 1,750 — MPLX senior notes, 5.200% due March 2047 1,000 1,000 MPLX senior notes, 4.700% due April 2048 1,500 — MPLX senior notes, 5.500% due February 2049 1,500 — MPLX senior notes, 4.900% due April 2058 500 — MPLX capital lease obligations due 2020 6 7 ANDX LP: ANDX revolving and dropdown credit facilities due 2021 1,245 — ANDX senior notes, 5.500% due October 2019 500 — ANDX senior notes, 6.250% due October 2022 300 — ANDX senior notes, 3.500% due December 2022 500 — ANDX senior notes, 6.375% due May 2024 450 — ANDX senior notes, 5.250% due January 2025 750 — ANDX senior notes, 4.250% due December 2027 750 — ANDX senior notes, 5.200% due December 2047 500 — ANDX capital lease obligations 15 — Total 27,980 13,418 Unamortized debt issuance costs (128 ) (59 ) Unamortized (discount) premium, net (328 ) (413 ) Amounts due within one year (544 ) (624 ) Total long-term debt due after one year $ 26,980 $ 12,322
Schedule Of Debt Payments	Principal maturities for our debt obligations and capital lease obligations as of December 31, 2018 for the next five years were as follows: (In millions) 2019 $ 544 2020 695 2021 2,296 2022 1,320 2023 2,403

Supplemental Cash Flow Inform_2

Supplemental Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2018
Supplemental Cash Flow Information [Abstract]
Summary of Supplemental Cash Flow Information	(In millions) 2018 2017 2016 Net cash provided by operating activities included: Interest paid (net of amounts capitalized) $ 887 $ 525 $ 478 Net income taxes paid to taxing authorities 424 904 140 Non-cash investing and financing activities: Capital leases $ 172 $ 71 $ — Contribution of assets to joint venture (a) — 337 273 Intangible asset acquired — 45 — Acquisition: Fair value of MPC shares issued 19,766 — — Fair value of converted equity awards 203 — — (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 . (In millions) December 31, December 31, Cash and cash equivalents $ 1,687 $ 3,011 Restricted cash (a) 38 4 Cash, cash equivalents and restricted cash (b) $ 1,725 $ 3,015
Schedule of Cash and Cash Equivalents [Table Text Block]	(In millions) December 31, December 31, Cash and cash equivalents $ 1,687 $ 3,011 Restricted cash (a) 38 4 Cash, cash equivalents and restricted cash (b) $ 1,725 $ 3,015 (a) The restricted cash balance is included within other current assets on the consolidated balance sheets. (b) As a result of the adoption of ASU 2016-18, the consolidated statements of cash flows now explain the change during the period of both cash and cash equivalents and restricted cash.
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) 2018 2017 2016 Additions to property, plant and equipment per the consolidated statements of cash flows $ 3,578 $ 2,732 $ 2,892 Asset retirement expenditures (a) 8 2 6 Increase (decrease) in capital accruals 309 67 (127 ) Total capital expenditures $ 3,895 $ 2,801 $ 2,771 (a) Included in All other, net – Operating activities on the consolidated statements of cash flows.

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Loss (Tables)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Changes in Accumulated Other Comprehensive Loss by Component	The following table shows the changes in accumulated other comprehensive loss by component. (In millions) Pension Benefits Other Benefits Gain on Cash Flow Hedge Workers Compensation Total Balance as of December 31, 2016 $ (233 ) $ (7 ) $ 4 $ 2 $ (234 ) Other comprehensive income (loss) before reclassifications 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 — — — (2 ) (2 ) Tax effect (18 ) 2 — — (16 ) Other comprehensive inco me (loss) 43 (41 ) — 1 3 Balance as of December 31, 2017 $ (190 ) $ (48 ) $ 4 $ 3 $ (231 ) (In millions) Pension Benefits Other Benefits Gain on Cash Flow Hedge Workers Compensation Total Balance as of December 31, 2017 $ (190 ) $ (48 ) $ 4 $ 3 $ (231 ) Other comprehensive income (loss) before reclassifications 14 27 (1 ) 9 49 Amounts reclassified from accumulated other comprehensive loss: Amortization – prior service credit (a) (33 ) (3 ) — — (36 ) – actuarial loss (a) 31 (1 ) — — 30 – settlement loss (a) 53 — — — 53 Other — — (1 ) (5 ) (6 ) Tax effect (7 ) 2 — 2 (3 ) Other comprehensive income (loss) 58 25 (2 ) 6 87 Balance as of December 31, 2018 $ (132 ) $ (23 ) $ 2 $ 9 $ (144 ) (a) These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 22 .

Defined Benefit Pension and O_2

Defined Benefit Pension and Other Postretirement Plans (Tables)	12 Months Ended
	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [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) 2018 2017 Projected benefit obligations $ 2,779 $ 2,164 Accumulated benefit obligations 2,632 2,008 Fair value of plan assets 2,089 1,840
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) 2018 2017 2018 2017 Change in benefit obligations: Benefit obligations at January 1 $ 2,164 $ 2,024 $ 826 $ 740 Service cost 159 132 30 25 Interest cost 83 75 30 30 Actuarial (gain) loss (159 ) 150 (71 ) 61 Benefits paid (273 ) (217 ) (36 ) (30 ) Plan amendments (90 ) — 34 — Acquisitions 895 — 71 — Benefit obligations at December 31 2,779 2,164 884 826 Change in plan assets: Fair value of plan assets at January 1 1,840 1,659 — — Actual return on plan assets (115 ) 270 — — Employer contributions 115 128 36 30 Benefits paid from plan assets (273 ) (217 ) (36 ) (30 ) Acquisitions 522 — — — Fair value of plan assets at December 31 2,089 1,840 — — Funded status of plans at December 31 $ (690 ) $ (324 ) $ (884 ) $ (826 ) Amounts recognized in the consolidated balance sheets: Current liabilities $ (21 ) $ (18 ) $ (44 ) $ (33 ) Noncurrent liabilities (669 ) (306 ) (840 ) (793 ) Accrued benefit cost $ (690 ) $ (324 ) $ (884 ) $ (826 ) Pretax amounts recognized in accumulated other comprehensive loss: (a) Net actuarial loss $ 517 $ 537 $ 9 $ 80 Prior service cost (credit) (295 ) (238 ) 35 (3 ) (a) Amounts exclude those related to LOOP and Explorer, equity method investees with defined benefit pension and postretirement plans for which net losses of $18 million and less than $1 million were recorded in accumulated other comprehensive loss in 2018 , 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) 2018 2017 2016 2018 2017 2016 Components of net periodic benefit cost: Service cost $ 159 $ 132 $ 114 $ 30 $ 25 $ 32 Interest cost 83 75 73 30 30 35 Expected return on plan assets (109 ) (100 ) (98 ) — — — Amortization – prior service credit (33 ) (39 ) (46 ) (3 ) (3 ) (3 ) – actuarial (gain) loss 31 36 38 (1 ) (2 ) 2 – settlement loss 53 52 7 — — — Net periodic benefit cost (a) $ 184 $ 156 $ 88 $ 56 $ 50 $ 66 Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax): Actuarial (gain) loss $ 64 $ (20 ) $ (33 ) $ (71 ) $ 61 $ (101 ) Prior service cost (credit) (90 ) — — 34 — — Amortization of actuarial gain (loss) (84 ) (88 ) (45 ) 1 2 (2 ) Amortization of prior service credit 33 39 46 3 3 3 Other — — — — — — Total recognized in other comprehensive loss $ (77 ) $ (69 ) $ (32 ) $ (33 ) $ 66 $ (100 ) Total recognized in net periodic benefit cost and other comprehensive loss $ 107 $ 87 $ 56 $ 23 $ 116 $ (34 ) (a) Net periodic benefit cost reflects a calculated market-related value of plan assets which recognizes changes in fair value over three years.
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) 2018 2017 2016 2018 2017 2016 Components of net periodic benefit cost: Service cost $ 159 $ 132 $ 114 $ 30 $ 25 $ 32 Interest cost 83 75 73 30 30 35 Expected return on plan assets (109 ) (100 ) (98 ) — — — Amortization – prior service credit (33 ) (39 ) (46 ) (3 ) (3 ) (3 ) – actuarial (gain) loss 31 36 38 (1 ) (2 ) 2 – settlement loss 53 52 7 — — — Net periodic benefit cost (a) $ 184 $ 156 $ 88 $ 56 $ 50 $ 66 Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax): Actuarial (gain) loss $ 64 $ (20 ) $ (33 ) $ (71 ) $ 61 $ (101 ) Prior service cost (credit) (90 ) — — 34 — — Amortization of actuarial gain (loss) (84 ) (88 ) (45 ) 1 2 (2 ) Amortization of prior service credit 33 39 46 3 3 3 Other — — — — — — Total recognized in other comprehensive loss $ (77 ) $ (69 ) $ (32 ) $ (33 ) $ 66 $ (100 ) Total recognized in net periodic benefit cost and other comprehensive loss $ 107 $ 87 $ 56 $ 23 $ 116 $ (34 ) (a) Net periodic benefit cost reflects a calculated market-related value of plan assets which recognizes changes in fair value over three years.
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 2018 , 2017 and 2016 . Pension Benefits Other Benefits 2018 2017 2016 2018 2017 2016 Weighted-average assumptions used to determine benefit obligation: Discount rate 4.21 % 3.55 % 3.90 % 4.26 % 3.70 % 4.25 % Rate of compensation increase 5.00 % 5.00 % 5.00 % 5.00 % 5.00 % 5.00 % Weighted-average assumptions used to determine net periodic benefit cost: Discount rate 3.88 % 3.85 % 3.80 % 3.72 % 4.25 % 4.50 % Expected long-term return on plan assets 6.15 % 6.50 % 6.50 % — % — % — % Rate of compensation increase 4.80 % 5.00 % 5.00 % 5.00 % 5.00 % 5.00 %
Assumed Health Care Cost Trend Rates	The following summarizes the assumed health care cost trend rates. December 31, 2018 2017 2016 Health care cost trend rate assumed for the following year: Medical: Pre-65 6.80 % 6.75 % 7.00 % Prescription drugs 9.50 % 8.75 % 9.00 % Rate to which the cost trend rate is assumed to decline (the ultimate trend rate): Medical: Pre-65 4.50 % 4.50 % 4.50 % Prescription drugs 4.50 % 4.50 % 4.50 % Year that the rate reaches the ultimate trend rate: Medical: Pre-65 2027 2026 2026 Prescription drugs 2027 2026 2026
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 34 (30 )
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, 2018 and 2017 . December 31, 2018 (In millions) Level 1 Level 2 Level 3 Total Cash and cash equivalents $ — $ 25 $ — $ 25 Equity: Common stocks 89 86 — 175 Mutual funds 159 — — 159 Pooled funds — 297 — 297 Fixed income: Corporate 176 684 — 860 Government 98 141 — 239 Pooled funds — 201 — 201 Private equity — — 41 41 Real estate — — 29 29 Other 45 — 18 63 Total investments, at fair value $ 567 $ 1,434 $ 88 $ 2,089 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
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: 2018 (In millions) Private Equity Real Estate Other Total Beginning balance $ 51 $ 34 $ 20 $ 105 Actual return on plan assets: Realized 9 2 — 11 Unrealized 2 (1 ) — 1 Purchases 1 1 — 2 Sales (22 ) (7 ) (2 ) (31 ) Ending balance $ 41 $ 29 $ 18 $ 88 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
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 2019 $ 238 $ 44 2020 254 46 2021 219 48 2022 218 50 2023 213 51 2024 through 2028 1,048 271
Multi Employer Pension Plan	Our participation in this plan for 2018 , 2017 and 2016 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 2018 and 2017 is for the plan’s year ended December 31, 2017 and December 31, 2016 , 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 2018 , 2017 and 2016 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 2018 2017 2018 2017 2016 Central States, Southeast and Southwest Areas Pension Plan (a) 366044243 Red Red Implemented $ 4 $ 4 $ 4 No January 31, 2024 (a) This agreement has a minimum contribution requirement of $328 per week per employee for 2019 . A total of 258 employees participated in the plan as of December 31, 2018 .

Stock-Based Compensation Plans

Stock-Based Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2018
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, including the converted awards related to the acquisition of Andeavor: (In millions) 2018 2017 2016 Stock-based compensation expense $ 133 $ 51 $ 45 Tax benefit recognized on stock-based compensation expense 32 19 17 Cash received by MPC upon exercise of stock option awards 24 46 10 Tax benefit received for tax deductions for stock awards exercised 14 25 4
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: 2018 2017 2016 Weighted average exercise price per share $ 67.71 $ 50.57 $ 35.27 Expected life in years 6.2 6.3 6.2 Expected volatility 34 % 35 % 38 % Expected dividend yield 3.0 % 3.0 % 3.0 % Risk-free interest rate 2.7 % 2.1 % 1.4 % Weighted average grant date fair value of stock option awards granted $ 17.21 $ 13.42 $ 9.84
Summary of Stock Option Award Activity	The following is a summary of our common stock option activity in 2018 : Number of of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Terms (in years) Aggregate Intrinsic Value (in millions) Outstanding at December 31, 2017 8,465,398 $ 33.74 Granted 903,797 67.71 Converted in acquisition 302,403 7.00 Exercised (916,566 ) 26.24 Forfeited or expired (30,437 ) 48.96 Outstanding at December 31, 2018 8,724,595 37.07 Vested and expected to vest at December 31, 2018 8,707,148 37.01 5.1 $ 199 Exercisable at December 31, 2018 6,586,859 31.42 4.0 182
Summary of Restricted Stock Award Activity	The following is a summary of restricted stock award activity of our common stock in 2018 : Shares of Restricted Stock (“RS”) Restricted Stock Units (“RSU”) Number of Shares Weighted Average Grant Date Fair Value Number of Units Weighted Average Grant Date Fair Value Outstanding at December 31, 2017 1,188,662 $ 45.07 285,164 $ 29.95 Granted 470,951 71.19 24,430 72.43 Converted in acquisition 16,972 82.43 4,452,751 82.43 RS Vested/RSUs Issued (624,934 ) 45.98 (526,254 ) 65.34 Forfeited (60,951 ) 50.27 (9,235 ) 82.43 Outstanding at December 31, 2018 990,700 57.23 4,226,856 80.96
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 2018 $ 49 $ 71.19 $ 39 $ 72.43 2017 28 50.25 5 53.19 2016 17 36.17 8 40.85
Schedule of Performance Unit Awards	The following table presents a summary of the 2018 activity for performance unit awards to be settled in shares: Number of Units Weighted Average Grant Date Fair Value Outstanding at December 31, 2017 6,851,542 $ 0.81 Granted 3,830,000 0.83 Vested (2,052,959 ) 0.95 Forfeited (10,000 ) 0.92 Outstanding at December 31, 2018 8,618,583 0.79
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: 2018 2017 2016 Risk-free interest rate 2.3 % 1.5 % 1.0 % Look-back period (in years) 2.8 2.8 2.8 Expected volatility 34.0 % 36.1 % 34.2 % Grant date fair value of performance units granted $ 0.83 $ 0.92 $ 0.57

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2018
Leases [Abstract]
Schedule Of Future Minimum Commitments	Future minimum commitments as of December 31, 2018 , 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 2019 $ 70 $ 709 2020 71 619 2021 66 553 2022 75 389 2023 82 295 Later years 586 858 Total minimum lease payments 950 $ 3,423 Less imputed interest costs 301 Present value of net minimum lease payments $ 649
Schedule Of Operating Lease Rental Expense	Operating lease rental expense was: (In millions) 2018 2017 2016 Rental expense $ 546 $ 367 $ 370
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, 2018 : (In millions) 2019 $ 160 2020 159 2021 150 2022 148 2023 142 Later years 1,111 Total minimum lease payments $ 1,870
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, 2018 : (In millions) Natural gas gathering and NGL transportation pipelines and facilities $ 965 Natural gas processing facilities 481 Terminal and related assets 133 Land, building, office equipment and other 43 Construction in progress 19 Property, plant and equipment 1,641 Less accumulated depreciation 219 Total property, plant and equipment $ 1,422

Selected Quarterly Financial _2

Selected Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Data [Abstract]
Schedule Of Quarterly Financial Information	2018 2017 (In millions, except per share data) 1st Qtr. 2nd Qtr. 3rd Qtr. 4th Qtr. 1st Qtr. 2nd Qtr. 3rd Qtr. 4th Qtr. (a) Sales and other operating revenues (b) $ 18,866 $ 22,317 $ 22,988 $ 32,333 $ 16,288 $ 18,180 $ 19,210 $ 21,055 Income from operations 440 1,711 1,403 2,017 291 982 1,577 1,168 Net income 235 1,235 941 1,195 101 574 1,004 2,125 Net income attributable to MPC 37 1,055 737 951 30 483 903 2,016 Net income attributable to MPC per share (c) : Basic $ 0.08 $ 2.30 $ 1.63 $ 1.38 $ 0.06 $ 0.94 $ 1.79 $ 4.13 Diluted 0.08 2.27 1.62 1.35 0.06 0.93 1.77 4.09 (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. (b) Includes sales to related parties. The 2018 periods reflect an election to present certain taxes on a net basis concurrent with our adoption of ASC 606. (c) The sum of the per-share amounts for the four quarters may not always equal the annual per-share amounts due to differences in the average number of shares outstanding during the respective periods.

Description of the Business (De

Description of the Business (Details) bbl / d in Millions	12 Months Ended
	Dec. 31, 2018bbl / drefinery
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Crude capacity | bbl / d	3
Number of refineries | refinery	16

Summary Of Principal Accounti_3

Summary Of Principal Accounting Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Summary Of Principal Accounting Policies [Line Items]
MPC's ownership percentage of the general partner interest	100.00%
Accounts receivable number of days past-due evaluated for doubtful accounts	180 days
Asset retirement obligation, current	$ 30	$ 6
Asset retirement obligations, noncurrent	$ 222	$ 121
MPLX
Summary Of Principal Accounting Policies [Line Items]
MPC's partnership interest in MLPs (in percentage)	63.60%
ANDX
Summary Of Principal Accounting Policies [Line Items]
MPC's partnership interest in MLPs (in percentage)	63.60%
Minimum
Summary Of Principal Accounting Policies [Line Items]
Estimated useful lives (in years)	3 years
Maximum
Summary Of Principal Accounting Policies [Line Items]
Estimated useful lives (in years)	51 years
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%

ASU 2014-09, Revenue - Revenue

ASU 2014-09, Revenue - Revenue from Contracts with Customers (ASC 606) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cumulative effect of adopting new accounting standards			$ 68
Sales and other operating revenues, excluding consumer excise taxes	[1],[2]	$ 95,750
Cost of revenues	[2]	85,456	66,519	$ 56,676
Matching buy/sell receivables		1,640
Income taxes receivable		88
Accounting Standards Update 2014-09 [Member]
Cumulative effect of adopting new accounting standards			4
Accounting Standards Update 2014-09 [Member] | Sales and other operating revenues
Excise and sales taxes			5,150
Accounting Standards Update 2014-09 [Member] | Cost of revenues
Excise and sales taxes			$ 5,150
Accounting Standards Update 2014-09 [Member] | Consumer Excise Tax
Sales and other operating revenues, excluding consumer excise taxes		6,660
Cost of revenues		6,660
Accounting Standards Update 2014-09 [Member] | Third Party Reimbursements, Noncash Consideration and Imbalances
Sales and other operating revenues, excluding consumer excise taxes		502
Cost of revenues		$ 502
[1]	The 2018 period reflects an election to present certain taxes on a net basis concurrent with our adoption of ASC 606.
[2]	The 2018 period reflects an election to present certain taxes on a net basis concurrent with our adoption of ASU 2014-09, Revenue - Revenue from Contracts with Customers (“ASC 606”). See Notes 2 and 3 for further information.

ASU 2016-16, Income Taxes - Int

ASU 2016-16, Income Taxes - Intra-Entity Transfers of Assets Other Than Inventory (Details) $ in Millions	Dec. 31, 2017USD ($)
Cumulative effect of adopting new accounting standards	$ 68
Accounting Standards Update 2016-16 [Member]
Cumulative effect of adopting new accounting standards	$ 62

Accounting Standards ASU 2016-0

Accounting Standards ASU 2016-02 Leases and related updates (Details) - Accounting Standards Update 2016-02 $ in Billions	12 Months Ended
	Dec. 31, 2018USD ($)
Minimum
Effect of adoption, quantification	$ 2.5
Maximum
Effect of adoption, quantification	$ 3

Master Limited Partnerships (MP

Master Limited Partnerships (MPLX) (Detail)	Dec. 31, 2018
MPLX
Noncontrolling Interest [Line Items]
MPC's partnership interest in MLPs (in percentage)	63.60%

Master Limited Partnerships (_2

Master Limited Partnerships (MPLX-Private Placement of Preferred Units) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	May 13, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Noncontrolling Interest [Line Items]
Issuance of MPLX LP redeemable preferred units		$ 0	$ 0	$ 984
Series A Convertible Preferred Units | MPLX
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
Series A Convertible Preferred Units | MPLX | Preferred Units
Noncontrolling Interest [Line Items]
Sale of units (number of units)	30.8
Units issued, price per unit	$ 32.50

Master Limited Partnerships (_3

Master Limited Partnerships (MPLX-Dropdowns to MPLX and GP/IDR Exchange) (Details) - MPLX - USD ($) shares in Thousands, $ in Millions	Feb. 01, 2018	Sep. 01, 2017	Mar. 01, 2017	Mar. 31, 2016	Jan. 02, 2018
Limited Partner
Noncontrolling Interest [Line Items]
Units issued, number of units	112,000	19,000	13,000	23,000
Conversion of stock, shares issued	275,000
General Partner
Noncontrolling Interest [Line Items]
Units issued, number of units	2,000	378	264	460
MPLX 364-day term loan
Noncontrolling Interest [Line Items]
Line of credit facility, maximum borrowing capacity	$ 4,100				$ 4,100
Debt instrument, term	364 days
Cash and cash equivalents
Noncontrolling Interest [Line Items]
Cash payment for acquisition	$ 4,100	$ 420	$ 1,500

Master Limited Partnerships (AN

Master Limited Partnerships (ANDX) (Details)	Dec. 31, 2018shares
ANDX
MPC's partnership interest in MLPs (in percentage)	63.60%
TexNew Mex units
Units outstanding	80,000

Master Limited Partnerships (No

Master Limited Partnerships (Noncontrolling Interest) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Increase (decrease) in MPC's additional paid-in capital, net of tax	$ (570)	$ 444	$ 658
Additional Paid-in Capital
Increase (decrease) due to the issuance of MPLX & ANDX common units to the public	6	25	(60)
Increase due to the issuance of MPLX & ANDX common units and general partner units to MPC	1,114	114	121
Increase due to GP/IDR Exchange	1,808	0	0
Increase in MPC's additional paid-in capital	2,928	139	61
Tax impact	(571)	(29)	(118)
Increase (decrease) in MPC's additional paid-in capital, net of tax	$ 2,357	$ 110	$ (57)

Acquisitions (Acquisition of An

Acquisitions (Acquisition of Andeavor) (Details) - USD ($) $ / shares in Units, $ in Millions	Oct. 01, 2018	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Fair value of shares issued			$ 19,766	$ 0	$ 0
Fair value of converted equity awards			203	0	0
Goodwill		$ 20,184	20,184	3,586	3,587
Pro-forma, purchase accounting inventory effects and transaction-related costs effect on net income attributable to MPC			727
Refining & Marketing
Business Acquisition [Line Items]
Goodwill		5,020	5,020	519	519
Midstream
Business Acquisition [Line Items]
Goodwill		10,323	$ 10,323	$ 2,276	$ 2,276
Andeavor
Business Acquisition [Line Items]
Common units conversion ratio	1.87
Cash consideration to unitholders (per unit)	$ 152.27
Common shares converted to cash, number of shares	22,900,000
Shares converted, number of shares	128,200,000
Shares issued or issuable, number of shares	239,800,000
Fair value of shares issued	$ 19,766
Cash payment for acquisition	3,486
Fair value of converted equity awards	203
Goodwill	16,314
Goodwill, expected tax deductible amount	893
Property, plant and equipment, net	16,545
Finite-lived intangibles	2,800
Long-term debt	8,875
Transaction costs	$ 47
Sales and other operating revenues		$ 11,300
Andeavor | Minimum
Business Acquisition [Line Items]
Acquired finite-lived intangible assets, weighted average useful life	2 years
Andeavor | Maximum
Business Acquisition [Line Items]
Acquired finite-lived intangible assets, weighted average useful life	10 years
Andeavor | Customer contracts and relationships
Business Acquisition [Line Items]
Finite-lived intangibles	$ 2,500
Andeavor | Refining & Marketing
Business Acquisition [Line Items]
Goodwill	4,700
Andeavor | Midstream
Business Acquisition [Line Items]
Goodwill	7,700
Andeavor | Retail
Business Acquisition [Line Items]
Goodwill	3,900
Andeavor | Line of Credit
Business Acquisition [Line Items]
Long-term debt	1,500
Andeavor | Other Debt Obligations
Business Acquisition [Line Items]
Long-term debt	$ 200

Acquisitions (Fair Value of Con

Acquisitions (Fair Value of Consideration Transferred - Andeavor) (Details) - USD ($) $ in Millions	Oct. 01, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Fair value of MPC shares issued		$ 19,766	$ 0	$ 0
Fair value of converted equity awards		$ 203	$ 0	$ 0
Andeavor
Business Acquisition [Line Items]
Fair value of MPC shares issued	$ 19,766
Cash payment to Andeavor stockholders	3,486
Cash settlement of non-employee director units	7
Fair value of converted equity awards	203
Total fair value of consideration transferred	$ 23,462

Acquisitions (Schedule of Asset

Acquisitions (Schedule of Assets Acquired and Liabilities Assumed - Andeavor) (Details) - USD ($) $ in Millions		Dec. 31, 2018	Oct. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill		$ 20,184		$ 3,586	$ 3,587
Andeavor
Cash and cash equivalents			$ 382
Receivables			2,744
Inventories			5,204
Other current assets			378
Equity method investments			865
Property, plant and equipment, net			16,545
Other noncurrent assets(a)	[1]		3,086
Total assets acquired			29,204
Accounts payable			4,003
Payroll and benefits payable			348
Accrued taxes			590
Debt due within one year			34
Other current liabilities			392
Long-term debt			8,875
Deferred income taxes			1,609
Defined benefit postretirement plan obligations			432
Deferred credit and other liabilities			714
Noncontrolling interests			5,059
Total liabilities and noncontrolling interest assumed			22,056
Net assets acquired excluding goodwill			7,148
Goodwill			16,314
Net assets acquired			$ 23,462
[1]	Includes intangible assets.

Acquisitions (Pro Forma Financi

Acquisitions (Pro Forma Financial Information - Andeavor) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended																12 Months Ended
		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Sales and other operating revenues, excluding consumer excise taxes	[1],[2]																	$ 95,750
Sales and other operating revenue, including excise taxes	[2]																		$ 74,104	$ 63,277
Net income attributable to MPC		$ 951		$ 737		$ 1,055		$ 37		$ 2,016	[3]	$ 903		$ 483		$ 30		$ 2,780	$ 3,432	$ 1,174
Net income attributable to MPC per share – basic		$ 1.38	[4]	$ 1.63	[4]	$ 2.30	[4]	$ 0.08	[4]	$ 4.13	[4]	$ 1.79	[4]	$ 0.94	[4]	$ 0.06	[4]	$ 5.36	$ 6.76	$ 2.22
Net income attributable to MPC per share – diluted		$ 1.35	[4]	$ 1.62	[4]	$ 2.27	[4]	$ 0.08	[4]	$ 4.09	[4]	$ 1.77	[4]	$ 0.93	[4]	$ 0.06	[4]	$ 5.28	$ 6.70	$ 2.21
Andeavor
Business Acquisition [Line Items]
Sales and other operating revenues, excluding consumer excise taxes	[5]																	$ 131,695
Sales and other operating revenue, including excise taxes																			$ 117,549
Net income attributable to MPC																		$ 4,371	$ 4,832
Net income attributable to MPC per share – basic																		$ 8.44	$ 6.47
Net income attributable to MPC per share – diluted																		$ 8.31	$ 6.41
[1]	The 2018 period reflects an election to present certain taxes on a net basis concurrent with our adoption of ASC 606.
[2]	The 2018 period reflects an election to present certain taxes on a net basis concurrent with our adoption of ASU 2014-09, Revenue - Revenue from Contracts with Customers (“ASC 606”). See Notes 2 and 3 for further information.
[3]	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.
[4]	The sum of the per-share amounts for the four quarters may not always equal the annual per-share amounts due to differences in the average number of shares outstanding during the respective periods.
[5]	The 2018 period reflects an election to present certain taxes on a net basis concurrent with our adoption of ASC 606.

Acquisition (Acquisition of Exp

Acquisition (Acquisition of Express Mart) (Details) $ in Millions	Nov. 16, 2018USD ($)Store	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Business Acquisition [Line Items]
Goodwill		$ 20,184	$ 3,586	$ 3,587
Express Mart
Business Acquisition [Line Items]
Number of stores | Store	78
Cash payment for acquisition	$ 266
Property, plant and equipment, net	97
Inventories	9
Finite-lived intangibles	2
Goodwill	$ 158

Acquisitions (Acquisition of Mt

Acquisitions (Acquisition of Mt. Airy Terminal) (Details) bbl / d in Thousands, bbl in Millions, $ in Millions	Sep. 26, 2018USD ($)bbl / dbbl	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Business Acquisition [Line Items]
Goodwill		$ 20,184	$ 3,586	$ 3,587
Mt. Airy Terminal
Business Acquisition [Line Items]
Storage capacity | bbl	4
Barrels handled | bbl / d	120
MPLX | Mt. Airy Terminal
Business Acquisition [Line Items]
Cash payment for acquisition	$ 451
Property, plant and equipment, net	336
Goodwill	$ 126

Acquisitions (Acquisition of Oz

Acquisitions (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
Business Acquisition [Line Items]
Cash payment for acquisition | $	$ 219

Acquisitions (Investment in Pip

Acquisitions (Investment in Pipeline Company) (Details) - USD ($) $ in Millions	Feb. 15, 2017	Dec. 31, 2018
MarEn Bakken Company LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		25.00%
MPLX | 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 | 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 (Formation of Gath

Acquisitions (Formation of Gathering and Processing Joint Venture) (Details) bbl / d in Thousands, $ in Millions		Jan. 01, 2017USD ($)bbl / d	Dec. 31, 2018USD ($)bbl / d	Dec. 31, 2017USD ($)	[1]	Dec. 31, 2016USD ($)	[1]
Schedule of Equity Method Investments [Line Items]
Contribution of fixed assets to joint venture			$ 0	$ 337		$ 273
Capacity | bbl / d			3,000
MPLX
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
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
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	[2]		60.00%
Sherwood Midstream Holdings | Direct Ownership Interest
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		79.00%
Sherwood Midstream Holdings | MPLX
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.
[2]	Excludes Sherwood Midstream LLC’s investment in Sherwood Midstream Holdings LLC.

Acquisitions (Formation of Trav

Acquisitions (Formation of Travel Plaza Joint Venture) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	[1]	Dec. 31, 2016USD ($)Store
Schedule of Equity Method Investments [Line Items]
Contribution of fixed assets to joint venture	$ 0	$ 337		$ 273	[1]
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]
Number of stores | Store				41
PFJ Southeast | Pilot Flying J
Schedule of Equity Method Investments [Line Items]
Number of 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.

Variable Interest Entities (Bal

Variable Interest Entities (Balance Sheet Information for Consolidated VIEs) (Details) - USD ($) $ in Millions		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents		$ 1,687	$ 3,011
Receivables, less allowance for doubtful accounts		5,853	4,695
Inventories		9,837	5,550
Other current assets		646	145
Equity method investments		5,898	4,787
Property, plant and equipment, net		45,058	26,443
Goodwill		20,184	3,586	$ 3,587
Other noncurrent assets		3,777	830
Liabilities
Accounts payable		9,366	8,297
Payroll and benefits payable		1,152	591
Accrued taxes		1,446	670
Debt due within one year		544	624
Other current liabilities		708	296
Long-term debt		26,980	12,322
Defined benefit postretirement plan obligations		1,509	1,099
Deferred credits and other liabilities		1,318	666
VIE, Primary Beneficiary | MPLX
Assets
Cash and cash equivalents		68	5
Receivables, less allowance for doubtful accounts		425	299
Inventories		77	65
Other current assets		45	29
Equity method investments		4,174	4,010
Property, plant and equipment, net		14,639	12,187
Goodwill		2,586	2,245
Other noncurrent assets		458	479
Liabilities
Accounts payable		776	621
Payroll and benefits payable		2	1
Accrued taxes		48	38
Debt due within one year		1	1
Other current liabilities		177	130
Long-term debt		13,392	6,945
Deferred income taxes		13	5
Defined benefit postretirement plan obligations		0	0
Deferred credits and other liabilities		276	$ 230
VIE, Primary Beneficiary | ANDX
Assets
Cash and cash equivalents	[1]	10
Receivables, less allowance for doubtful accounts	[1]	199
Inventories	[1]	22
Other current assets	[1]	57
Equity method investments	[1]	602
Property, plant and equipment, net	[1]	6,845
Goodwill	[1]	1,051
Other noncurrent assets	[1]	1,242
Liabilities
Accounts payable	[1]	215
Payroll and benefits payable	[1]	10
Accrued taxes	[1]	23
Debt due within one year	[1]	504
Other current liabilities	[1]	77
Long-term debt	[1]	4,469
Deferred income taxes	[1]	1
Defined benefit postretirement plan obligations	[1]	0
Deferred credits and other liabilities	[1]	$ 68
[1]	The balances reflected here are ANDX’s historical balances as the preliminary purchase accounting adjustments related to ANDX’s assets and liabilities in connection with the Andeavor acquisition and reflected on our consolidated balance sheet as of December 31, 2018 have not yet been pushed down to this subsidiary.

Variable Interest Entities (Non

Variable Interest Entities (Non-Consolidated VIEs) (Details) bbl / d in Thousands, $ in Millions		Dec. 31, 2018USD ($)bbl / d	Dec. 31, 2017USD ($)	Jan. 01, 2017bbl / d
Schedule of Equity Method Investments [Line Items]
Equity method investments		$ 5,898	$ 4,787
Capacity | bbl / d		3,000
Crowley Coastal Partners, LLC
Schedule of Equity Method Investments [Line Items]
Maximum loss exposure, amount		$ 481
Equity method investments, ownership percentage		50.00%
MarkWest Utica EMG
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		56.00%
Equity method investments		$ 2,000
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		$ 366
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, ownership percentage	[1]	60.00%
Equity method investments		$ 157
Sherwood Midstream Holdings | Direct Ownership Interest
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage				79.00%
Sherwood Midstream Holdings | Indirect Ownership Interest
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage				10.50%
Andeavor Logistics Rio Pipeline
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		67.00%
Equity method investments		$ 181
Rendezvous Gas Services, L.L.C.
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		78.00%
Equity method investments		$ 248
[1]	Excludes Sherwood Midstream LLC’s investment in Sherwood Midstream Holdings LLC.

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transactions [Abstract]
Sales to related parties	[1]	$ 754	$ 629	$ 62
Purchases from related parties	[2]	$ 610	$ 570	$ 509
[1]	Sales to related parties consists primarily of sales of refined products to PFJ Southeast, an equity affiliate which owns and operates travel plazas primarily in the Southeast region of the United States.
[2]	We obtain transportation services and purchase ethanol from certain of our equity affiliates, none of which is individually material.

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, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Basic earnings per share:
Net income attributable to MPC	$ 951		$ 737		$ 1,055		$ 37		$ 2,016	[1]	$ 903		$ 483		$ 30		$ 2,780	$ 3,432	$ 1,174
Income allocated to participating securities, basic																	1	2	1
Income available to common stockholders – basic																	$ 2,779	$ 3,430	$ 1,173
Weighted average common shares outstanding (in shares)																	518	507	528
Net income attributable to MPC per share – basic	$ 1.38	[2]	$ 1.63	[2]	$ 2.30	[2]	$ 0.08	[2]	$ 4.13	[2]	$ 1.79	[2]	$ 0.94	[2]	$ 0.06	[2]	$ 5.36	$ 6.76	$ 2.22
Diluted earnings per share:
Net income attributable to MPC	$ 951		$ 737		$ 1,055		$ 37		$ 2,016	[1]	$ 903		$ 483		$ 30		$ 2,780	$ 3,432	$ 1,174
Income allocated to participating securities, diluted																	1	2	1
Income available to common stockholders – diluted																	$ 2,779	$ 3,430	$ 1,173
Weighted average common shares outstanding (in shares)																	518	507	528
Effect of dilutive securities (in shares)																	8	5	2
Weighted average common shares, including dilutive effect (in shares)																	526	512	530
Net income attributable to MPC per share – diluted	$ 1.35	[2]	$ 1.62	[2]	$ 2.27	[2]	$ 0.08	[2]	$ 4.09	[2]	$ 1.77	[2]	$ 0.93	[2]	$ 0.06	[2]	$ 5.28	$ 6.70	$ 2.21
[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.
[2]	The sum of the per-share amounts for the four quarters may not always equal the annual per-share amounts due to differences in the average number of shares outstanding during the respective periods.

Income Per Common Share (Anti-d

Income Per Common Share (Anti-dilutive Shares) (Detail) - shares shares in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Shares issuable under stock-based compensation plans
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	0	1	3

Equity (Narrative) (Detail)

Equity (Narrative) (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Oct. 01, 2018	Sep. 30, 2018
Equity [Abstract]
Common stock, shares authorized	2,000,000,000	2,000,000,000	1,000,000,000
Stock repurchase plan remaining authorized amount	$ 4,900

Equity (Share Repurchases) (Det

Equity (Share Repurchases) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Equity [Abstract]
Number of shares repurchased	47	44	4
Cash paid for shares repurchased	$ 3,287	$ 2,372	$ 197
Average cost per share	$ 69.46	$ 53.85	$ 41.84

Segment Information (Narrative)

Segment Information (Narrative) (Detail) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2018USD ($)Segmentrefinery	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | Segment									3
Number of refineries | refinery									16
Income from operations	$ 2,017	$ 1,403	$ 1,711	$ 440	$ 1,168	$ 1,577	$ 982	$ 291	$ 5,571	$ 4,018	$ 2,386
None | Maximum
Segment Reporting Information [Line Items]
Percent of annual revenues									10.00%	10.00%	10.00%
Refining Logistics & Fuels Distribution [Member] | Refining & Marketing
Segment Reporting Information [Line Items]
Income from operations									$ (874)
Refining Logistics & Fuels Distribution [Member] | Midstream
Segment Reporting Information [Line Items]
Income from operations									$ 874

Segment Information (Income Fro

Segment Information (Income From Operations Attributable To Operating Segments) (Detail) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes	[1],[2]									$ 95,750
Sales and other operating revenue, including excise taxes	[2]										$ 74,104		$ 63,277
Sales to related parties	[3]									754	629		62
Income from operations		$ 2,017	$ 1,403	$ 1,711	$ 440	$ 1,168	$ 1,577	$ 982	$ 291	5,571	4,018		2,386
Income from equity method investments										373	306		(185)
Depreciation and amortization										2,490	2,114		2,001
Inventory market valuation adjustment										0	0		(370)
Refining & Marketing
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										68,939
Sales and other operating revenue, including excise taxes											52,761		43,167
Sales to related parties										746	621		61
Inventory market valuation adjustment	[4]												345
Retail
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										23,538
Sales and other operating revenue, including excise taxes											19,021		18,282
Sales to related parties										8	8		1
Inventory market valuation adjustment	[4]												25
Midstream
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										3,273
Sales and other operating revenue, including excise taxes											2,322		1,828
Sales to related parties										0	0		0
Reportable Segment [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										95,750
Sales and other operating revenue, including excise taxes											74,104		63,277
Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										16,307
Sales and other operating revenue, including excise taxes											12,756		11,854
Intersegment Eliminations | Refining & Marketing
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										12,914
Sales and other operating revenue, including excise taxes	[5]										11,309		10,589
Intersegment Eliminations | Retail
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										6
Sales and other operating revenue, including excise taxes	[5]										4		3
Intersegment Eliminations | Midstream
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										3,387
Sales and other operating revenue, including excise taxes	[5]										1,443		1,262
Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										112,811
Sales and other operating revenue, including excise taxes											87,489		75,193
Income from operations										6,261	4,389		3,138
Income from equity method investments	[6]									363	283		171
Depreciation and amortization	[6]									2,412	2,056		1,941
Segment capital expenditures and investments	[7]									4,147	2,968		2,915
Operating Segments | Refining & Marketing
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										82,599
Sales and other operating revenue, including excise taxes											64,691		53,817
Income from operations										2,481	2,321	[8]	1,357	[8]
Income from equity method investments										15	17		24
Depreciation and amortization										1,174	1,082		1,063
Segment capital expenditures and investments	[7]									1,057	832		1,054
Operating Segments | Retail
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										23,552
Sales and other operating revenue, including excise taxes											19,033		18,286
Income from operations										1,028	729	[8]	733	[8]
Income from equity method investments										74	69		5
Depreciation and amortization										353	275		273
Segment capital expenditures and investments	[7]									460	381		303
Operating Segments | Midstream
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										6,660
Sales and other operating revenue, including excise taxes											3,765		3,090
Income from operations										2,752	1,339		1,048
Income from equity method investments										274	197		142
Depreciation and amortization										885	699		605
Segment capital expenditures and investments	[7]									$ 2,630	$ 1,755		$ 1,558
[1]	The 2018 period reflects an election to present certain taxes on a net basis concurrent with our adoption of ASC 606.
[2]	The 2018 period reflects an election to present certain taxes on a net basis concurrent with our adoption of ASU 2014-09, Revenue - Revenue from Contracts with Customers (“ASC 606”). See Notes 2 and 3 for further information.
[3]	Sales to related parties consists primarily of sales of refined products to PFJ Southeast, an equity affiliate which owns and operates travel plazas primarily in the Southeast region of the United States.
[4]	2017 includes MPC’s share of gains from the the sale of assets remaining from the canceled Sandpiper pipeline project. 2016 includes impairments of goodwill and equity method investments. See Note 17.
[5]	Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties.
[6]	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
[7]	Capital expenditures include changes in capital accruals and investments in affiliates
[8]	In 2016, the Refining & Marketing and Retail segments include an inventory LCM benefit of $345 million and $25 million, respectively.

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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations		$ 2,017	$ 1,403	$ 1,711	$ 440	$ 1,168	$ 1,577	$ 982	$ 291	$ 5,571	$ 4,018		$ 2,386
Net interest and other financial costs										1,003	674		564
Income before income taxes										4,568	3,344		1,822
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations										6,261	4,389		3,138
Corporate and Other
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations										(502)	(365)	[1]	(266)
Segment Reconciling Items
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Transaction-related costs										(197)	0		0
Litigation										0	(29)		0
Impairment	[2]									$ 9	$ 23		$ (486)
[1]	Corporate and other unallocated items consists primarily of MPC’s corporate administrative expenses and costs related to certain non-operating assets, except for corporate overhead expenses attributable to MPLX and ANDX, which are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Retail segments.
[2]	2017 includes MPC’s share of gains from the the sale of assets remaining from the canceled Sandpiper pipeline project. 2016 includes impairments of goodwill and equity method investments. See Note 17.

Segment Information (Reconcil_2

Segment Information (Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Plus items not allocated to segments:
Total capital expenditures	[1]	$ 3,895	$ 2,801	$ 2,771
Operating Segments
Segment Reporting, Other Significant Reconciling Item [Line Items]
Segment capital expenditures and investments	[2]	4,147	2,968	2,915
Investments in equity method investments		409	305	288
Corporate and Other
Plus items not allocated to segments:
Corporate		77	83	81
Capitalized interest		$ 80	$ 55	$ 63
[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]	Capital expenditures include changes in capital accruals and investments in affiliates

Segment Information (Schedule O

Segment Information (Schedule Of Revenues By Product Line) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Sales and other operating revenue, including excise taxes	[1]		$ 74,104	$ 63,277
Sales and other operating revenues, excluding consumer excise taxes	[1],[2]	$ 95,750
Refined products
Segment Reporting Information [Line Items]
Sales and other operating revenue, including excise taxes			63,846	54,450
Sales and other operating revenues, excluding consumer excise taxes		83,888
Merchandise
Segment Reporting Information [Line Items]
Sales and other operating revenue, including excise taxes			5,174	5,297
Sales and other operating revenues, excluding consumer excise taxes		5,332
Crude oil and refinery feedstocks
Segment Reporting Information [Line Items]
Sales and other operating revenue, including excise taxes			3,403	2,038
Sales and other operating revenues, excluding consumer excise taxes		4,143
Midstream services, transportation and other
Segment Reporting Information [Line Items]
Sales and other operating revenue, including excise taxes			$ 1,681	$ 1,492
Sales and other operating revenues, excluding consumer excise taxes		$ 2,387
[1]	The 2018 period reflects an election to present certain taxes on a net basis concurrent with our adoption of ASU 2014-09, Revenue - Revenue from Contracts with Customers (“ASC 606”). See Notes 2 and 3 for further information.
[2]	The 2018 period reflects an election to present certain taxes on a net basis concurrent with our adoption of ASC 606.

Net Interest And Other Financ_3

Net Interest And Other Financial Costs (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Income and Expenses [Abstract]
Interest income		$ (87)	$ (27)	$ (6)
Interest expense		1,026	688	602
Interest capitalized		(80)	(63)	(64)
Pension and other postretirement non-service costs	[1]	53	49	8
Loss on extinguishment of debt		64	0	0
Other financial costs		27	27	24
Net interest and other financial income (costs)		$ 1,003	$ 674	$ 564
[1]	See Note 22.

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Detail) - USD ($) $ in Millions	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Statutory rate applied to income before income taxes	21.00%		21.00%	35.00%	35.00%
Change in enacted tax rate, amount		$ 1,500		$ 1,500
Unrecognized tax benefits that would impact effective income tax rate			$ 201
Uncertain tax positions, reasonably possible increase or decrease during the next twelve months			15
Unrecognized tax benefits income tax net penalties and interest expense (benefits)			1	3	$ (5)
Interest and penalties accrued		$ 17	$ 18	$ 17

Income Taxes (Components Of Inc

Income Taxes (Components Of Income Tax Provisions (Benefits)) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current
Federal	$ 715	$ 681	$ 189
State and local	178	98	27
Foreign	22	(6)	(1)
Total	915	773	215
Deferred
Federal	2	(1,270)	336
State and local	61	33	57
Foreign	(16)	4	1
Total	47	(1,233)	394
Total
Federal	717	(589)	525
State and local	239	131	84
Foreign	6	(2)	0
Total	$ 962	$ (460)	$ 609

Income Taxes (Reconciliation Of

Income Taxes (Reconciliation Of Federal Statutory Income Tax Rate) (Detail)	Jan. 01, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Statutory rate applied to income before income taxes	21.00%	21.00%	35.00%	35.00%
State and local income taxes, net of federal income tax effects		4.00%	2.00%	3.00%
Domestic manufacturing deduction		(0.00%)	(1.00%)	(1.00%)
Noncontrolling interests		(4.00%)	(4.00%)	(1.00%)
Biodiesel excise tax credit		(0.00%)	(0.00%)	(1.00%)
TCJA legislation		(0.00%)	(45.00%)	(0.00%)
Other		(0.00%)	(1.00%)	(2.00%)
Provision for income taxes		21.00%	(14.00%)	33.00%

Income Taxes (Components Of Def

Income Taxes (Components Of Deferred Tax Assets And Liabilities) (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Employee benefits	$ 660	$ 348
Environmental remediation	111	16
Debt financing	39	0
Net operating loss carryforwards	17	12
Foreign currency	28	13
Tax credit carryforwards	21	0
Other	88	31
Total deferred tax assets	964	420
Deferred tax liabilities:
Property, plant and equipment	2,830	1,603
Inventories	678	473
Investments in subsidiaries and affiliates	2,130	912
Intangibles	97	70
Other	64	3
Total deferred tax liabilities	5,799	3,061
Net deferred tax liabilities	$ 4,835	$ 2,641

Income Taxes (Components Of Net

Income Taxes (Components Of Net Deferred Tax Liabilities Classified In Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Assets
Other noncurrent assets	$ 29	$ 13
Liabilities
Deferred income taxes	4,864	2,654
Net deferred tax liabilities	$ 4,835	$ 2,641

Income Taxes (Tax Carryforwards

Income Taxes (Tax Carryforwards) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
United States Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 7	$ 5
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, 2037
States
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 10	$ 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, 2037

Income Taxes (Valuation Allowan

Income Taxes (Valuation Allowances) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Valuation allowance	$ 10	$ 11

Income Taxes (Summary Of Income

Income Taxes (Summary Of Income Tax Returns Subject To Examination) (Detail)	12 Months Ended
	Dec. 31, 2018
United States Federal | Minimum
Income Tax Examination [Line Items]
Tax years	2,009
United States Federal | Maximum
Income Tax Examination [Line Items]
Tax years	2,017
States | Minimum
Income Tax Examination [Line Items]
Tax years	2,006
States | Maximum
Income Tax Examination [Line Items]
Tax years	2,017

Income Taxes (Summary Of Activi

Income Taxes (Summary Of Activity In Unrecognized Tax Benefits) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
January 1 balance	$ 19	$ 7	$ 12
Additions for tax positions of prior years	0	13	6
Reductions for tax positions of prior years	(5)	0	(10)
Settlements, decrease	0	(1)	(1)
Statute of limitations	(12)	0	0
Acquired from Andeavor	209	0	0
December 31 balance	$ 211	$ 19	$ 7

Inventories (Summary Of Invento

Inventories (Summary Of Inventories) (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Crude oil and refinery feedstocks	$ 3,655	$ 2,056
Refined products	5,234	2,839
Materials and supplies	720	494
Merchandise	228	161
Total	$ 9,837	$ 5,550

Inventories (Narrative) (Detail

Inventories (Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Total inventory LIFO percentage	92.00%	90.00%
Excess of current acquisition costs over stated LIFO value	$ 0	$ 1,210
Effect of LIFO inventory liquidation on income	$ 0	$ (7)	$ 0

Equity Method Investments (Sche

Equity Method Investments (Schedule Of Equity Method Investments) (Detail) - USD ($) $ in Millions		Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Equity method investments		$ 5,898	$ 4,787
Andeavor Logistics Rio Pipeline
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		67.00%
Equity method investments		$ 181
Centrahoma Processing LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		40.00%
Crowley Coastal Partners, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		50.00%
Illinois Extension Pipeline
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		35.00%
LOOP
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		51.00%
MarEn Bakken Company LLC
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%
MarkWest Utica EMG
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		56.00%
Equity method investments		$ 2,000
Minnesota Pipe Line Company, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		17.00%
Rendezvous Gas Services, L.L.C.
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		78.00%
Equity method investments		$ 248
PFJ Southeast
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		29.00%
Sherwood Midstream Holdings
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	[1]	60.00%
Equity method investments		$ 157
Sherwood Midstream
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		50.00%
Equity method investments		$ 366
Watson Cogeneration Company
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		51.00%
Refining & Marketing
Schedule of Equity Method Investments [Line Items]
Equity method investments		$ 205	104
Refining & Marketing | Watson Cogeneration Company
Schedule of Equity Method Investments [Line Items]
Equity method investments		84	0
Refining & Marketing | Other equity method investees
Schedule of Equity Method Investments [Line Items]
Equity method investments		121	104
Retail
Schedule of Equity Method Investments [Line Items]
Equity method investments		341	328
Retail | PFJ Southeast
Schedule of Equity Method Investments [Line Items]
Equity method investments		341	328
Midstream
Schedule of Equity Method Investments [Line Items]
Equity method investments		5,352	4,355
Midstream | Andeavor Logistics Rio Pipeline
Schedule of Equity Method Investments [Line Items]
Equity method investments		181	0
Midstream | Centrahoma Processing LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments		160	121
Midstream | Crowley Coastal Partners, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments		190	188
Midstream | Illinois Extension Pipeline
Schedule of Equity Method Investments [Line Items]
Equity method investments		275	284
Midstream | LOOP
Schedule of Equity Method Investments [Line Items]
Equity method investments		282	282
Midstream | MarEn Bakken Company LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments		498	520
Midstream | MarkWest EMG Jefferson Dry Gas
Schedule of Equity Method Investments [Line Items]
Equity method investments		236	164
Midstream | MarkWest Utica EMG
Schedule of Equity Method Investments [Line Items]
Equity method investments		2,039	2,139
Midstream | Minnesota Pipe Line Company, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments		197	0
Midstream | Rendezvous Gas Services, L.L.C.
Schedule of Equity Method Investments [Line Items]
Equity method investments		248	0
Midstream | Sherwood Midstream Holdings
Schedule of Equity Method Investments [Line Items]
Equity method investments		157	165
Midstream | Sherwood Midstream
Schedule of Equity Method Investments [Line Items]
Equity method investments		366	236
Midstream | Other equity method investees
Schedule of Equity Method Investments [Line Items]
Equity method investments		$ 523	$ 256
[1]	Excludes Sherwood Midstream LLC’s investment in Sherwood Midstream Holdings LLC.

Equity Method Investments (Summ

Equity Method Investments (Summarized Financial Information For Equity Method Investees) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income statement data:
Revenues and other income	$ 7,726	$ 6,235	$ 2,421
Income (loss) from operations	1,375	1,075	(116)
Net income (loss)	1,242	922	$ (250)
Balance sheet data – December 31:
Current assets	1,443	860
Noncurrent assets	12,408	10,854
Current liabilities	1,857	547
Noncurrent liabilities	$ 1,788	$ 1,714

Equity Method Investments (Narr

Equity Method Investments (Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Equity Method Investments and Joint Ventures [Abstract]
Equity method investment difference between carrying amount and underlying equity	$ 1,590
Equity method investment difference between carrying amount and underlying equity, portion related to goodwill which is not being amortized	721
Dividends and partnership distributions received from equity method investees	$ 519	$ 391	$ 317

Property, Plant And Equipment_2

Property, Plant And Equipment (Summary Of Property, Plant And Equipment) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 61,213	$ 40,538
Less accumulated depreciation	16,155	14,095
Net property, plant and equipment	45,058	26,443
Operating Segments | Refining & Marketing
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	27,590	19,490
Operating Segments | Retail
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	6,637	5,358
Operating Segments | Midstream
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	25,692	14,898
Corporate and Other
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 1,294	$ 792
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 | Retail
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)	51 years
Maximum | Operating Segments | Refining & Marketing
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	30 years
Maximum | Operating Segments | Retail
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)	51 years
Maximum | Corporate and Other
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	40 years

Property, Plant And Equipment_3

Property, Plant And Equipment (Narrative) (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 61,213	$ 40,538
Property, plant and equipment, accumulated depreciation	16,155	14,095
Assets held under capital leases
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	786	602
Property, plant and equipment, accumulated depreciation	202	248
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 3,490	$ 2,200

Goodwill (Changes In Carrying A

Goodwill (Changes In Carrying Amount Of Goodwill) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
Beginning balance		$ 3,586	$ 3,587
Disposition			(1)
Acquisitions		16,598
Transfer of assets related to dropdowns		0
Ending balance		20,184	3,586
Refining & Marketing
Goodwill [Line Items]
Beginning balance		519	519
Disposition			0
Acquisitions		4,717
Transfer of assets related to dropdowns		(216)
Ending balance		5,020	519
Retail
Goodwill [Line Items]
Beginning balance		791	792
Disposition			(1)
Acquisitions	[1]	4,050
Transfer of assets related to dropdowns	[1]	0
Ending balance		4,841	791
Midstream
Goodwill [Line Items]
Beginning balance		2,276	2,276
Disposition			0
Acquisitions		7,831
Transfer of assets related to dropdowns		216
Ending balance		$ 10,323	$ 2,276
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Intangibles (Intangible Assets

Intangibles (Intangible Assets by Major Class) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	$ 3,711	$ 892
Accumulated amortization	397	261
Net	3,314	631
Customer contracts and relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	3,184	654
Accumulated amortization	261	139
Net	2,923	515
Brand rights and tradenames
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	208	25
Accumulated amortization	33	24
Net	175	1
Royalty agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	129	129
Accumulated amortization	70	63
Net	59	66
Other intangible assets
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	190	84
Accumulated amortization	33	35
Net	$ 157	$ 49

Intangibles (Narrative) (Detail

Intangibles (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Indefinite-lived intangible assets	$ 94	$ 95
Amortization expense	$ 134	$ 52

Intangibles (Estimated Future A

Intangibles (Estimated Future Amortization Expense) (Details) $ in Millions	Dec. 31, 2018USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2,019	$ 387
2,020	385
2,021	379
2,022	378
2,023	$ 361

Fair Value Measurements (Assets

Fair Value Measurements (Assets And Liabilities Accounted For At Fair Value On Recurring Basis) (Detail) - USD ($) $ in Millions		Dec. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash collateral netted with derivative assets		$ 52
Cash collateral netted with derivative liabilities		13	$ 8
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - collateral and netting		(323)	(118)
Commodity derivative instruments, assets - collateral pledged not offset		2	8
Other assets			3
Total assets at fair value		78	12
Commodity derivative instruments, liabilities - netting and collateral		(284)	(126)
Commodity derivative instruments, liabilities - collateral pledged not offset		0	0
Total liabilities at fair value		69	66
Fair Value, Measurements, Recurring | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets			3
Total assets at fair value		370	130
Total liabilities at fair value		255	126
Fair Value, Measurements, Recurring | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets			0
Total assets at fair value		31	0
Total liabilities at fair value		37	0
Fair Value, Measurements, Recurring | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets			0
Total assets at fair value		0	0
Total liabilities at fair value		61	66
Fair Value, Measurements, Recurring | Commodity derivative instruments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - collateral and netting	[1]	(323)	(118)
Commodity derivative instruments, assets - net	[2]	78	9
Commodity derivative instruments, assets - collateral pledged not offset		2	8
Commodity derivative instruments, liabilities - netting and collateral	[1]	(284)	(126)
Commodity derivative instruments, liabilities, net	[2]	8	2
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		370	127
Commodity derivative instruments, liabilities - gross		255	126
Fair Value, Measurements, Recurring | Commodity derivative instruments | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - gross		31	0
Commodity derivative instruments, liabilities - gross		37	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		0	2
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	[1]	0	0
Commodity derivative instruments, liabilities, net	[2]	61	64
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		$ 61	$ 64
[1]	Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of December 31, 2018, cash collateral of $52 million was netted with mark-to-market derivative assets and $13 million was netted with mark-to-market liabilities. As of December 31, 2017, cash collateral of $8 million was netted with mark-to-market derivative liabilities.
[2]	We have no derivative contracts which are subject to master netting arrangements reflected gross on the balance sheet.

Fair Value Measurements (Recurr

Fair Value Measurements (Recurring Narrative) (Detail)	12 Months Ended
	Dec. 31, 2018USD ($)
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 | Commodity derivative instruments | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward commodity price	$ 0.58
Level 3 | Commodity derivative instruments | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward commodity price	$ 1.01
Level 3 | Embedded derivative in commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Probability of renewal	90.00%
Probability of renewal second term	80.00%

Fair Value Measurements (Reconc

Fair Value Measurements (Reconciliation Of Net Beginning And Ending Balances Recorded For Net Assets And Liabilities Classified As Level 3) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 66	$ 190
Contingent consideration payment	0	(131)
Unrealized and realized losses included in net income	3	25
Settlements of derivative instruments	(8)	(18)
Ending balance	$ 61	$ 66

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, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in unrealized loss	$ 8	$ 9
Derivative
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in unrealized loss	8	8
Contingent Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in unrealized loss	$ 0	$ 1

Fair Value Measurements (Nonrec

Fair Value Measurements (Nonrecurring Narrative) (Details) $ in Millions	3 Months Ended			12 Months Ended		38 Months Ended
	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)reporting_unit	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of reporting units | reporting_unit			3
Number of reporting units impaired | reporting_unit			2
Goodwill, impairment expense				$ 0	$ 0
Midstream
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill, impairment expense		$ 1	$ 129
Midstream | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill, measurement input			0.115
Measurement Input, Discount Rate | Midstream | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill, measurement input			0.105
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
North Dakota Pipeline | Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Income (loss) from equity method investments	$ (267)
Ohio Condensate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investments, ownership percentage		60.00%
Ohio Condensate | Fair Value, Measurements, Nonrecurring
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)
Equity Method Investments | Ohio Condensate | Measurement Input, Discount Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate		0.112

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Values - Reported) (Detail) - USD ($) $ in Billions	Dec. 31, 2018	Dec. 31, 2017
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 27	$ 12.6
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 26.5	$ 13.9

Derivatives (Classification Of

Derivatives (Classification Of Gross Fair Values Of Derivative Instruments, Excluding Cash Collateral) (Detail) - Commodity derivative instruments - USD ($) $ in Millions		Dec. 31, 2018	Dec. 31, 2017
Other current assets
Derivatives, Fair Value [Line Items]
Asset		$ 400	$ 127
Liability		283	126
Other current liabilities(a)
Derivatives, Fair Value [Line Items]
Asset	[1]	1	0
Liability	[1]	16	14
Deferred credits and other liabilities
Derivatives, Fair Value [Line Items]
Asset	[1]	0	0
Liability	[1]	$ 54	$ 52
[1]	Includes embedded derivatives.

Derivatives (Open Commodity Der

Derivatives (Open Commodity Derivative Contracts) (Detail) gal in Thousands, bbl in Thousands	12 Months Ended
	Dec. 31, 2018bblgal
Exchange Traded | Crude oil
Derivative [Line Items]
Percentage of derivative contracts expiring next quarter	71.50%
Exchange Traded | Crude oil | Long
Derivative [Line Items]
Notional contracts (contract volumes)	40,257	[1]
Exchange Traded | Crude oil | Long | Spread contracts
Derivative [Line Items]
Notional contracts (contract volumes)	7,470
Exchange Traded | Crude oil | Short
Derivative [Line Items]
Notional contracts (contract volumes) | gal	44,709	[1]
Exchange Traded | Crude oil | Short | Spread contracts
Derivative [Line Items]
Notional contracts (contract volumes)	6,800
Exchange Traded | Refined products
Derivative [Line Items]
Percentage of derivative contracts expiring next quarter	75.90%
Exchange Traded | Refined products | Long
Derivative [Line Items]
Notional contracts (contract volumes)	10,210	[1]
Exchange Traded | Refined products | Long | Spread contracts
Derivative [Line Items]
Notional contracts (contract volumes)	450
Exchange Traded | Refined products | Short
Derivative [Line Items]
Notional contracts (contract volumes) | gal	11,149	[1]
Exchange Traded | Refined products | Short | Spread contracts
Derivative [Line Items]
Notional contracts (contract volumes)	450
Exchange Traded | Blending products
Derivative [Line Items]
Percentage of derivative contracts expiring next quarter	70.30%
Exchange Traded | Blending products | Long
Derivative [Line Items]
Notional contracts (contract volumes)	5,194	[1]
Exchange Traded | Blending products | Long | Spread contracts
Derivative [Line Items]
Notional contracts (contract volumes)	2,678
Exchange Traded | Blending products | Short
Derivative [Line Items]
Notional contracts (contract volumes) | gal	7,356	[1]
Exchange Traded | Blending products | Short | Spread contracts
Derivative [Line Items]
Notional contracts (contract volumes)	2,767
OTC | Crude oil
Derivative [Line Items]
Percentage of derivative contracts expiring next quarter	0.00%
OTC | Crude oil | Long
Derivative [Line Items]
Notional contracts (contract volumes)	880
OTC | Crude oil | Short
Derivative [Line Items]
Notional contracts (contract volumes)	0
OTC | Blending products
Derivative [Line Items]
Percentage of derivative contracts expiring next quarter	24.10%
OTC | Blending products | Long
Derivative [Line Items]
Notional contracts (contract volumes)	2,480
OTC | Blending products | Short
Derivative [Line Items]
Notional contracts (contract volumes) | gal	2,480
[1]	Included in exchange-traded are spread contracts in thousands of barrels: Crude oil - 7,470 long and 6,800 short; Refined products - 450 long and 450 short; Blending products - 2,678 long and 2,767 short

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, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	$ (46)	$ (21)	$ (180)
Sales and other operating revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	13	5	(13)
Cost of revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	$ (59)	$ (26)	$ (167)

Debt (Outstanding Borrowings) (

Debt (Outstanding Borrowings) (Detail) - USD ($) $ in Millions	Jul. 20, 2016	Dec. 31, 2018	Oct. 02, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total		$ 27,980		$ 13,418
Unamortized debt issuance costs		(128)		(59)
Unamortized (discount) premium, net		(328)		(413)
Amounts due within one year		(544)		(624)
Total long-term debt due after one year		26,980		12,322
Trade receivables securitization facility due July 2019
Debt Instrument [Line Items]
Line of credit facility, expiration date	Jul. 19, 2019
Marathon Petroleum Corporation
Debt Instrument [Line Items]
Commercial paper		0		0
Notes payable		11		0
Marathon Petroleum Corporation | Line of Credit | 364-day bank revolving credit facility due September 2019
Debt Instrument [Line Items]
Long-term debt, gross		$ 0		0
Line of credit facility, expiration date		Sep. 30, 2019
Marathon Petroleum Corporation | Line of Credit | Bank revolving credit facility due October 2023
Debt Instrument [Line Items]
Long-term debt, gross		$ 0		0
Line of credit facility, expiration date		Oct. 1, 2023
Marathon Petroleum Corporation | Secured Debt | Trade receivables securitization facility due July 2019
Debt Instrument [Line Items]
Long-term debt, gross		$ 0		0
Line of credit facility, expiration date		Jul. 19, 2019
Marathon Petroleum Corporation | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross			$ 2,905
Marathon Petroleum Corporation | Senior Notes | Senior notes, 2.700% due December 2018
Debt Instrument [Line Items]
Long-term debt, gross		$ 0		600
Debt instrument, maturity date		Dec. 14, 2018
Debt instrument, interest rate		2.70%
Marathon Petroleum Corporation | Senior Notes | Senior notes, 3.400% due December 2020
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 | Senior notes, 5.125% due March 2021
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 | Senior notes, 4.750% due December 2023
Debt Instrument [Line Items]
Long-term debt, gross		$ 614	$ 614	0
Debt instrument, maturity date		Dec. 15, 2023
Debt instrument, interest rate		4.75%	4.75%
Marathon Petroleum Corporation | Senior Notes | Senior notes, 5.125% due April 2024
Debt Instrument [Line Items]
Long-term debt, gross		$ 241	$ 241	0
Debt instrument, maturity date		Apr. 1, 2024
Debt instrument, interest rate		5.125%	5.125%
Marathon Petroleum Corporation | Senior Notes | Senior notes, 3.625%, due September 2024
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 | Senior notes, 5.125% due December 2026
Debt Instrument [Line Items]
Long-term debt, gross		$ 719	$ 719	0
Debt instrument, maturity date		Dec. 15, 2026
Debt instrument, interest rate		5.125%	5.125%
Marathon Petroleum Corporation | Senior Notes | Senior notes, 3.800% due April 2028
Debt Instrument [Line Items]
Long-term debt, gross		$ 496	$ 496	0
Debt instrument, maturity date		Apr. 1, 2028
Debt instrument, interest rate		3.80%	3.80%
Marathon Petroleum Corporation | Senior Notes | Senior notes, 6.500% due March 2041
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 | Senior notes, 4.750% due September 2044
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 | Senior notes, 5.850% due December 2045
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 | Senior notes, 5.000%, due September 2054
Debt Instrument [Line Items]
Long-term debt, gross		$ 400		400
Debt instrument, maturity date		Sep. 15, 2054
Debt instrument, interest rate		5.00%
Marathon Petroleum Corporation | Senior Notes | MPLX senior notes, 4.700% due April 2048
Debt Instrument [Line Items]
Long-term debt, gross		$ 498	$ 498	0
Debt instrument, maturity date		Apr. 1, 2048
Debt instrument, interest rate		4.50%	4.50%
Marathon Petroleum Corporation | Senior Notes | ANDX senior notes, 6.250% due October 2022
Debt Instrument [Line Items]
Long-term debt, gross		$ 337	$ 337	0
Debt instrument, maturity date		Oct. 1, 2022
Debt instrument, interest rate		5.375%	5.375%
Marathon Petroleum Corporation | Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Capital lease obligations		$ 629		356
Debt instrument maturity year, start		Jan. 1, 2019
Debt instrument maturity year, end		Mar. 31, 2033
MPLX | Line of Credit | MPLX bank revolving credit facility due 2022
Debt Instrument [Line Items]
Long-term debt, gross		$ 0		505
Line of credit facility, expiration date		Jul. 21, 2022
MPLX | Senior Notes | MPLX senior notes, 5.500% due February 2023
Debt Instrument [Line Items]
Long-term debt, gross		$ 0		710
Debt instrument, maturity date		Feb. 15, 2023
Debt instrument, interest rate		5.50%
MPLX | Senior Notes | MPLX senior notes, 3.375% due March 2023
Debt Instrument [Line Items]
Long-term debt, gross		$ 500		0
Debt instrument, maturity date		Mar. 15, 2023
Debt instrument, interest rate		3.375%
MPLX | Senior Notes | MPLX senior notes, 4.500% due July 2023
Debt Instrument [Line Items]
Long-term debt, gross		$ 989		989
Debt instrument, maturity date		Jul. 15, 2023
Debt instrument, interest rate		4.50%
MPLX | Senior Notes | MPLX senior notes, 4.875% due December 2024
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,149		1,149
Debt instrument, maturity date		Dec. 1, 2024
Debt instrument, interest rate		4.875%
MPLX | Senior Notes | MPLX senior notes, 4.000% due February 2025
Debt Instrument [Line Items]
Long-term debt, gross		$ 500		500
Debt instrument, maturity date		Feb. 15, 2025
Debt instrument, interest rate		4.00%
MPLX | Senior Notes | MPLX senior notes, 4.875% due June 2025
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,189		1,189
Debt instrument, maturity date		Jun. 1, 2025
Debt instrument, interest rate		4.875%
MPLX | Senior Notes | MPLX senior notes, 4.125% due March 2027
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,250		1,250
Debt instrument, maturity date		Mar. 1, 2027
Debt instrument, interest rate		4.125%
MPLX | Senior Notes | MPLX senior notes, 4.000% due March 2028
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,250		0
Debt instrument, maturity date		Mar. 15, 2028
Debt instrument, interest rate		4.00%
MPLX | Senior Notes | MPLX senior notes, 4.800% due February 2029
Debt Instrument [Line Items]
Long-term debt, gross		$ 750		0
Debt instrument, maturity date		Feb. 15, 2019
Debt instrument, interest rate		4.80%
MPLX | Senior Notes | MPLX senior notes, 4.500% due April 2038
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,750		0
Debt instrument, maturity date		Apr. 15, 2038
Debt instrument, interest rate		4.50%
MPLX | Senior Notes | MPLX senior notes, 5.200% due March 2047
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,000		1,000
Debt instrument, maturity date		Mar. 1, 2047
Debt instrument, interest rate		5.20%
MPLX | Senior Notes | MPLX senior notes, 4.700% due April 2048
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,500		0
Debt instrument, maturity date		Apr. 15, 2048
Debt instrument, interest rate		4.70%
MPLX | Senior Notes | MPLX senior notes, 5.500% due February 2049
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,500		0
Debt instrument, maturity date		Feb. 15, 2049
Debt instrument, interest rate		5.50%
MPLX | Senior Notes | MPLX senior notes, 4.900% due April 2058
Debt Instrument [Line Items]
Long-term debt, gross		$ 500		0
Debt instrument, maturity date		Apr. 15, 2058
Debt instrument, interest rate		4.90%
MPLX | Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Capital lease obligations		$ 6		7
Debt instrument maturity year, start		Jan. 1, 2019
Debt instrument maturity year, end		Mar. 31, 2020
ANDX | Line of Credit | ANDX revolving and dropdown credit facilities due 2021
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,245		0
Line of credit facility, expiration date		Jan. 29, 2021
ANDX | Senior Notes | ANDX senior notes, 5.500% due October 2019
Debt Instrument [Line Items]
Long-term debt, gross		$ 500		0
Debt instrument, maturity date		Oct. 1, 2019
Debt instrument, interest rate		5.50%
ANDX | Senior Notes | ANDX senior notes, 6.250% due October 2022
Debt Instrument [Line Items]
Long-term debt, gross		$ 300		0
Debt instrument, maturity date		Oct. 15, 2022
Debt instrument, interest rate		6.25%
ANDX | Senior Notes | ANDX senior notes, 3.500% due December 2022
Debt Instrument [Line Items]
Long-term debt, gross		$ 500		0
Debt instrument, maturity date		Dec. 1, 2022
Debt instrument, interest rate		3.50%
ANDX | Senior Notes | ANDX senior notes, 6.375% due May 2024
Debt Instrument [Line Items]
Long-term debt, gross		$ 450		0
Debt instrument, maturity date		May 1, 2024
Debt instrument, interest rate		6.375%
ANDX | Senior Notes | ANDX senior notes, 5.250% due January 2025
Debt Instrument [Line Items]
Long-term debt, gross		$ 750		0
Debt instrument, maturity date		Jan. 15, 2025
Debt instrument, interest rate		5.25%
ANDX | Senior Notes | ANDX senior notes, 4.250% due December 2027
Debt Instrument [Line Items]
Long-term debt, gross		$ 750		0
Debt instrument, maturity date		Dec. 1, 2027
Debt instrument, interest rate		4.25%
ANDX | Senior Notes | ANDX senior notes, 5.200% due December 2047
Debt Instrument [Line Items]
Long-term debt, gross		$ 500		0
Debt instrument, maturity date		Dec. 1, 2047
Debt instrument, interest rate		5.20%
ANDX | Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Capital lease obligations		$ 15		0
Andeavor | Marathon Petroleum Corporation | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 469		0
Andeavor | Marathon Petroleum Corporation | Senior Notes | Senior notes, 4.750% due December 2023
Debt Instrument [Line Items]
Debt instrument, maturity date		Dec. 15, 2023
Debt instrument, interest rate		4.75%
Andeavor | Marathon Petroleum Corporation | Senior Notes | Senior notes, 5.125% due April 2024
Debt Instrument [Line Items]
Debt instrument, maturity date		Apr. 1, 2024
Debt instrument, interest rate		5.125%
Andeavor | Marathon Petroleum Corporation | Senior Notes | Senior notes, 5.125% due December 2026
Debt Instrument [Line Items]
Debt instrument, maturity date		Dec. 15, 2026
Debt instrument, interest rate		5.125%
Andeavor | Marathon Petroleum Corporation | Senior Notes | Senior notes, 3.800% due April 2028
Debt Instrument [Line Items]
Debt instrument, maturity date		Apr. 1, 2028
Debt instrument, interest rate		3.80%
Andeavor | Marathon Petroleum Corporation | Senior Notes | MPLX senior notes, 4.700% due April 2048
Debt Instrument [Line Items]
Debt instrument, maturity date		Apr. 1, 2048
Debt instrument, interest rate		4.50%
Andeavor | Marathon Petroleum Corporation | Senior Notes | ANDX senior notes, 6.250% due October 2022
Debt Instrument [Line Items]
Debt instrument, maturity date		Oct. 1, 2022
Debt instrument, interest rate		5.375%
MarkWest | MPLX | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross		$ 23		$ 63
MarkWest | MPLX | Senior Notes | MPLX senior notes, 5.500% due February 2023
Debt Instrument [Line Items]
Debt instrument, maturity date		Feb. 15, 2023
Debt instrument, interest rate		5.50%
MarkWest | MPLX | Senior Notes | MPLX senior notes, 4.500% due July 2023
Debt Instrument [Line Items]
Debt instrument, maturity date		Jul. 15, 2023
Debt instrument, interest rate		4.50%
MarkWest | MPLX | Senior Notes | MPLX senior notes, 4.875% due December 2024
Debt Instrument [Line Items]
Debt instrument, maturity date		Dec. 1, 2024
Debt instrument, interest rate		4.875%
MarkWest | MPLX | Senior Notes | MPLX senior notes, 4.875% due June 2025
Debt Instrument [Line Items]
Debt instrument, maturity date		Jun. 1, 2025
Debt instrument, interest rate		4.875%

Debt (Schedule Of Debt Payments

Debt (Schedule Of Debt Payments) (Detail) $ in Millions	Dec. 31, 2018USD ($)
Debt Disclosure [Abstract]
2,019	$ 544
2,020	695
2,021	2,296
2,022	1,320
2,023	$ 2,403

Debt (Commercial Paper) (Detail

Debt (Commercial Paper) (Details) - USD ($) $ in Millions	Feb. 26, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Commercial paper – issued		$ 0	$ 300	$ 1,263
Commercial paper - repayments		0	300	$ 1,263
Commercial Paper
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 2,000
Debt instrument, term	397 days
Marathon Petroleum Corporation
Debt Instrument [Line Items]
Commercial paper outstanding		$ 0	$ 0

Debt (MPC Revolving Credit Agre

Debt (MPC Revolving Credit Agreements) (Detail) $ in Millions	Oct. 01, 2018USD ($)Period	Dec. 31, 2018USD ($)	Jul. 20, 2016USD ($)
Bank revolving credit facility due October 2023
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity			$ 2,500
Repayments		$ 0
364-day bank revolving credit facility due September 2019
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity			$ 1,000
Borrowings		0
Repayments		0
Bank revolving credit facility due 2023
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 5,000
Debt instrument, term	5 years
Number of renewal periods | Period	2
Line of credit facility duration of renewal period	1 year
Borrowings		0
Bank revolving credit facility due 2023 | Letter of Credit
Line of Credit Facility [Line Items]
Line of credit facility, current borrowing capacity	$ 2,200
Bank revolving credit facility due 2023 | Maximum
Line of Credit Facility [Line Items]
Line of credit facility additional borrowing capacity	1,000
Bank revolving credit facility due 2023 | Maximum | Bridge Loan
Line of Credit Facility [Line Items]
Line of credit facility, current borrowing capacity	250
Bank revolving credit facility due 2023 | Maximum | Letter of Credit
Line of Credit Facility [Line Items]
Line of credit facility, current borrowing capacity	$ 3,000
Bank revolving credit facility due 2023 | Line of Credit
Line of Credit Facility [Line Items]
Line of credit facility, expiration date	Oct. 1, 2023
364-day revolving credit facility due 2019
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 1,000
Debt instrument, term	364 days
364-day revolving credit facility due 2019 | Line of Credit
Line of Credit Facility [Line Items]
Line of credit facility, expiration date	Sep. 30, 2019
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 new 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
Marathon Petroleum Corporation | Bank revolving credit facility due October 2023 | Letter of Credit
Line of Credit Facility [Line Items]
Letters of credit outstanding		$ 32
Marathon Petroleum Corporation | Bank revolving credit facility due October 2023 | Line of Credit
Line of Credit Facility [Line Items]
Line of credit facility, expiration date		Oct. 1, 2023
Marathon Petroleum Corporation | 364-day bank revolving credit facility due September 2019 | Letter of Credit
Line of Credit Facility [Line Items]
Letters of credit outstanding		$ 0
Marathon Petroleum Corporation | 364-day bank revolving credit facility due September 2019 | Line of Credit
Line of Credit Facility [Line Items]
Line of credit facility, expiration date		Sep. 30, 2019

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, 2018	Dec. 31, 2017	Oct. 30, 2015
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
Borrowings		0
Repayments		0
Letter of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 750
Marathon Petroleum Corporation | Letter of Credit
Debt Instrument [Line Items]
Letters of credit outstanding		$ 0
Marathon Petroleum Corporation | Secured Debt
Debt Instrument [Line Items]
Line of credit facility, expiration date		Jul. 19, 2019
Long-term debt outstanding		$ 0	$ 0

Debt (MPC Senior Notes) (Detail

Debt (MPC Senior Notes) (Details) - USD ($) $ in Millions	Mar. 15, 2018	Dec. 31, 2018	Oct. 02, 2018	Oct. 01, 2018	Dec. 31, 2017
Senior notes, 2.700% due December 2018
Debt Instrument [Line Items]
Repayments of long-term debt	$ 600
Make whole premium	$ 2.5
Andeavor
Debt Instrument [Line Items]
Long-term debt				$ 8,875
Senior Notes | Andeavor
Debt Instrument [Line Items]
Long-term debt				$ 3,374
Senior Notes | Marathon Petroleum Corporation
Debt Instrument [Line Items]
Long-term debt outstanding			$ 2,905
Senior Notes | Marathon Petroleum Corporation | Senior notes, 5.375% due October 2022
Debt Instrument [Line Items]
Long-term debt outstanding		$ 337	$ 337		$ 0
Debt instrument, interest rate		5.375%	5.375%
Senior Notes | Marathon Petroleum Corporation | Senior notes, 4.750% due December 2023
Debt Instrument [Line Items]
Long-term debt outstanding		$ 614	$ 614		0
Debt instrument, interest rate		4.75%	4.75%
Senior Notes | Marathon Petroleum Corporation | Senior notes, 5.125% due April 2024
Debt Instrument [Line Items]
Long-term debt outstanding		$ 241	$ 241		0
Debt instrument, interest rate		5.125%	5.125%
Senior Notes | Marathon Petroleum Corporation | Senior notes, 5.125% due December 2026
Debt Instrument [Line Items]
Long-term debt outstanding		$ 719	$ 719		0
Debt instrument, interest rate		5.125%	5.125%
Senior Notes | Marathon Petroleum Corporation | Senior notes, 3.800% due April 2028
Debt Instrument [Line Items]
Long-term debt outstanding		$ 496	$ 496		0
Debt instrument, interest rate		3.80%	3.80%
Senior Notes | Marathon Petroleum Corporation | Senior notes, 4.500% due April 2048
Debt Instrument [Line Items]
Long-term debt outstanding		$ 498	$ 498		0
Debt instrument, interest rate		4.50%	4.50%
Senior Notes | Marathon Petroleum Corporation | Senior notes, 2.700% due December 2018
Debt Instrument [Line Items]
Long-term debt outstanding		$ 0			600
Debt instrument, interest rate		2.70%
Senior Notes | Marathon Petroleum Corporation | Andeavor
Debt Instrument [Line Items]
Long-term debt outstanding		$ 469			$ 0
Senior Notes | Marathon Petroleum Corporation | Andeavor | Senior notes, 5.375% due October 2022
Debt Instrument [Line Items]
Debt instrument, interest rate		5.375%
Senior Notes | Marathon Petroleum Corporation | Andeavor | Senior notes, 4.750% due December 2023
Debt Instrument [Line Items]
Debt instrument, interest rate		4.75%
Senior Notes | Marathon Petroleum Corporation | Andeavor | Senior notes, 5.125% due April 2024
Debt Instrument [Line Items]
Debt instrument, interest rate		5.125%
Senior Notes | Marathon Petroleum Corporation | Andeavor | Senior notes, 5.125% due December 2026
Debt Instrument [Line Items]
Debt instrument, interest rate		5.125%
Senior Notes | Marathon Petroleum Corporation | Andeavor | Senior notes, 3.800% due April 2028
Debt Instrument [Line Items]
Debt instrument, interest rate		3.80%
Senior Notes | Marathon Petroleum Corporation | Andeavor | Senior notes, 4.500% due April 2048
Debt Instrument [Line Items]
Debt instrument, interest rate		4.50%
Senior Notes | Andeavor | Senior notes, 5.375% due October 2022
Debt Instrument [Line Items]
Long-term debt outstanding			$ 138
Debt instrument, interest rate			5.375%
Senior Notes | Andeavor | Senior notes, 4.750% due December 2023
Debt Instrument [Line Items]
Long-term debt outstanding			$ 236
Debt instrument, interest rate			4.75%
Senior Notes | Andeavor | Senior notes, 5.125% due April 2024
Debt Instrument [Line Items]
Long-term debt outstanding			$ 59
Debt instrument, interest rate			5.125%
Senior Notes | Andeavor | Senior notes, 5.125% due December 2026
Debt Instrument [Line Items]
Long-term debt outstanding			$ 30
Debt instrument, interest rate			5.125%
Senior Notes | Andeavor | Senior notes, 3.800% due April 2028
Debt Instrument [Line Items]
Long-term debt outstanding			$ 4
Debt instrument, interest rate			3.80%
Senior Notes | Andeavor | Senior notes, 4.500% due April 2048
Debt Instrument [Line Items]
Long-term debt outstanding			$ 2
Debt instrument, interest rate			4.50%

Debt (MPLX Credit Agreement) (D

Debt (MPLX Credit Agreement) (Details) - MPLX - MPLX bank revolving credit facility due 2022 $ in Millions	Jul. 21, 2017USD ($)	Dec. 31, 2018USD ($)	Oct. 27, 2015USD ($)
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 2,250		$ 2,000
Debt instrument, term	5 years
Debt instrument, description of variable rate basis	Adjusted LIBO Rate or the Alternate Base Rate (both as defined in the MPLX credit agreement)
Borrowings		$ 1,410
Interest rate during period		3.464%
Repayments		$ 1,915
Remaining borrowing capacity		2,250
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

Debt (MPLX Term Loan) (Details)

Debt (MPLX Term Loan) (Details) - MPLX - MPLX 364-day term loan - USD ($) $ in Millions	Feb. 08, 2018	Feb. 01, 2018	Jan. 02, 2018
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 4,100	$ 4,100
Debt instrument, term		364 days
Borrowings		$ 4,100
Repayments of short-term debt	$ 4,100

Debt (MPLX Senior Notes) (Detai

Debt (MPLX Senior Notes) (Details) - USD ($) $ in Millions	Dec. 10, 2018	Feb. 08, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Nov. 15, 2018
Debt Instrument [Line Items]
Loss on extinguishment of debt			$ 64	$ 0	$ 0
MPLX senior notes, 5.500% due February 2023
Debt Instrument [Line Items]
Redemption price, percentage	101.833%
Loss on extinguishment of debt			$ 60
MPLX | MPLX 364-day term loan
Debt Instrument [Line Items]
Repayments of short-term debt		$ 4,100
MPLX | Senior Notes
Debt Instrument [Line Items]
Long-term debt outstanding		5,500				$ 2,250
MPLX | Senior Notes | MPLX senior notes, 4.800% due February 2029
Debt Instrument [Line Items]
Long-term debt outstanding						$ 750
Debt instrument, interest rate						4.80%
MPLX | Senior Notes | MPLX senior notes, 5.500% due February 2049
Debt Instrument [Line Items]
Long-term debt outstanding						$ 1,500
Debt instrument, interest rate						5.50%
MPLX | Senior Notes | MPLX senior notes, 5.500% due February 2023
Debt Instrument [Line Items]
Debt instrument, interest rate	5.50%
Repayments of long-term debt	$ 750
MPLX | Senior Notes | MPLX senior notes, 3.375% due March 2023
Debt Instrument [Line Items]
Long-term debt outstanding		$ 500
Debt instrument, interest rate		3.375%
MPLX | Senior Notes | MPLX senior notes, 4.000% due March 2028
Debt Instrument [Line Items]
Long-term debt outstanding		$ 1,250
Debt instrument, interest rate		4.00%
MPLX | Senior Notes | MPLX senior notes, 4.500% due April 2038
Debt Instrument [Line Items]
Long-term debt outstanding		$ 1,750
Debt instrument, interest rate		4.50%
MPLX | Senior Notes | MPLX senior notes, 4.700% due April 2048
Debt Instrument [Line Items]
Long-term debt outstanding		$ 1,500
Debt instrument, interest rate		4.70%
MPLX | Senior Notes | MPLX senior notes, 4.900% due April 2058
Debt Instrument [Line Items]
Long-term debt outstanding		$ 500
Debt instrument, interest rate		4.90%

Debt (ANDX Credit Agreements) (

Debt (ANDX Credit Agreements) (Details) $ in Millions	Oct. 01, 2018USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
ANDX revolving and dropdown credit facilities due 2021
Debt Instrument [Line Items]
Debt instrument, description of variable rate basis	at LIBOR or the Base Rate (as defined in the ANDX credit agreements) plus an applicable margin
ANDX | ANDX revolving credit facility due 2021
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 1,100
ANDX | ANDX dropdown credit facility due 2021
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	1,000
ANDX | ANDX revolving and dropdown credit facilities due 2021
Debt Instrument [Line Items]
Borrowings		$ 760
Interest rate during period		4.46%
Repayments		$ 635
Remaining borrowing capacity		855
ANDX | ANDX revolving and dropdown credit facilities due 2021 | 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
ANDX | Letter of Credit | ANDX revolving and dropdown credit facilities due 2021 | Maximum
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity	$ 300
ANDX | Bridge Loan | ANDX revolving and dropdown credit facilities due 2021 | Maximum
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity	$ 50
ANDX | Line of Credit | ANDX revolving and dropdown credit facilities due 2021
Debt Instrument [Line Items]
Long-term debt outstanding		$ 1,245	$ 0

Debt (ANDX Senior Notes) (Detai

Debt (ANDX Senior Notes) (Details) - Andeavor $ in Millions	Oct. 01, 2018USD ($)
Debt Instrument [Line Items]
Long-term debt	$ 8,875
Senior Notes
Debt Instrument [Line Items]
Long-term debt	3,374
ANDX | Senior Notes
Debt Instrument [Line Items]
Long-term debt	3,750
ANDX | Senior Notes | ANDX senior notes, 5.500% due October 2019
Debt Instrument [Line Items]
Long-term debt	$ 500
Debt instrument, interest rate	5.50%
ANDX | Senior Notes | ANDX senior notes, 3.500% due December 2022
Debt Instrument [Line Items]
Long-term debt	$ 500
Debt instrument, interest rate	3.50%
ANDX | Senior Notes | ANDX senior notes, 6.250% due October 2022
Debt Instrument [Line Items]
Long-term debt	$ 300
Debt instrument, interest rate	6.25%
ANDX | Senior Notes | ANDX senior notes, 6.375% due May 2024
Debt Instrument [Line Items]
Long-term debt	$ 450
Debt instrument, interest rate	6.375%
ANDX | Senior Notes | ANDX senior notes, 5.250% due January 2025
Debt Instrument [Line Items]
Long-term debt	$ 750
Debt instrument, interest rate	5.25%
ANDX | Senior Notes | ANDX senior notes, 4.250% due December 2027
Debt Instrument [Line Items]
Long-term debt	$ 750
Debt instrument, interest rate	4.25%
ANDX | Senior Notes | ANDX senior notes, 5.200% due December 2047
Debt Instrument [Line Items]
Long-term debt	$ 500
Debt instrument, interest rate	5.20%

Supplemental Cash Flow Inform_3

Supplemental Cash Flow Information (Summary Of Supplemental Cash Flow Information) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Net cash provided by operating activities included:
Interest paid (net of amounts capitalized)	$ 887	$ 525		$ 478
Net income taxes paid to taxing authorities	424	904		140
Non-cash investing and financing activities:
Capital leases	172	71		0
Contribution of fixed assets to joint venture	0	337	[1]	273	[1]
Intangible asset acquired	0	45		0
Acquisition:
Fair value of MPC shares issued	19,766	0		0
Fair value of converted equity awards	$ 203	$ 0		$ 0
[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.

Supplemental Cash Flow Inform_4

Supplemental Cash Flow Information (Change in Cash and Cash Equivalents) (Details) - USD ($) $ in Millions		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Supplemental Cash Flow Elements [Abstract]
Cash and cash equivalents		$ 1,687		$ 3,011
Restricted cash	[1]	38		4
Cash, cash equivalents and restricted cash		$ 1,725	[2]	$ 3,015	[2]	$ 892	$ 1,136
[1]	The restricted cash balance is included within other current assets on the consolidated balance sheets.
[2]	As a result of the adoption of ASU 2016-18, the consolidated statements of cash flows now explain the change during the period of both cash and cash equivalents and restricted cash.

Supplemental Cash Flow Inform_5

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, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Cash Flow Information [Abstract]
Additions to property, plant and equipment per the consolidated statements of cash flows		$ 3,578	$ 2,732	$ 2,892
Asset retirement expenditures	[1]	8	2	6
Increase (decrease) in capital accruals		309	67	(127)
Total capital expenditures	[2]	$ 3,895	$ 2,801	$ 2,771
[1]	Included in All other, net – Operating activities on the consolidated statements of cash flows.
[2]	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 Comprehensi_3

Accumulated Other Comprehensive Loss (Changes in Accumulated Other Comprehensive Loss by Component) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		$ (231)	$ (234)
Other comprehensive income (loss) before reclassifications		49	(23)
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit		(36)	(42)
Amortization– actuarial loss		30	34
Amortization– settlement loss		53	52
Other		(6)	(2)
Tax effect		(3)	(16)
Other comprehensive income		87	3	$ 84
Ending balance		(144)	(231)	(234)
Pension Benefits
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit		(33)	(39)	(46)
Other Benefits
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit		(3)	(3)	(3)
Accumulated Defined Benefit Plans Adjustment | Pension Benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(190)	(233)
Other comprehensive income (loss) before reclassifications		14	12
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit	[1]	(33)	(39)
Amortization– actuarial loss	[1]	31	36
Amortization– settlement loss	[1]	53	52
Tax effect		(7)	(18)
Other comprehensive income		58	43
Ending balance		(132)	(190)	(233)
Accumulated Defined Benefit Plans Adjustment | Other Benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(48)	(7)
Other comprehensive income (loss) before reclassifications		27	(38)
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit	[1]	(3)	(3)
Amortization– actuarial loss	[1]	(1)	(2)
Amortization– settlement loss	[1]	0	0
Tax effect		2	2
Other comprehensive income		25	(41)
Ending balance		(23)	(48)	(7)
Gain on Cash Flow Hedge
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		4	4
Other comprehensive income (loss) before reclassifications		(1)	0
Amounts reclassified from accumulated other comprehensive loss:
Reclassified to earnings, net		(1)
Other comprehensive income		(2)	0
Ending balance		2	4	4
Workers Compensation
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		3	2
Other comprehensive income (loss) before reclassifications		9	3
Amounts reclassified from accumulated other comprehensive loss:
Other		(5)	(2)
Tax effect		2	0
Other comprehensive income		6	1
Ending balance		$ 9	$ 3	$ 2
[1]	These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 22.

Defined Benefit Pension And O_3

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, 2018	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Projected benefit obligations	$ 2,779	$ 2,164
Accumulated benefit obligations	2,632	2,008
Fair value of plan assets	$ 2,089	$ 1,840

Defined Benefit Pension And O_4

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, 2018		Dec. 31, 2017	Dec. 31, 2016
Change in plan assets:
Fair value of plan assets at January 1		$ 1,840
Fair value of plan assets at December 31		2,089		$ 1,840
Amounts recognized in the consolidated balance sheets:
Noncurrent liabilities		(1,509)		(1,099)
Pension Benefits
Change in benefit obligations:
Benefit obligations at January 1		2,164		2,024
Service cost		159		132	$ 114
Interest cost		83		75	73
Actuarial (gain) loss		(159)		150
Benefits paid		(273)		(217)
Plan amendments		(90)		0
Acquisitions		895		0
Benefit obligations at December 31		2,779		2,164	2,024
Change in plan assets:
Fair value of plan assets at January 1		1,840		1,659
Actual return on plan assets		(115)		270
Employer contributions		115		128
Benefits paid from plan assets		(273)		(217)
Acquisitions		522		0
Fair value of plan assets at December 31		2,089		1,840	1,659
Funded status of plans at December 31		(690)		(324)
Amounts recognized in the consolidated balance sheets:
Current liabilities		(21)		(18)
Noncurrent liabilities		(669)		(306)
Accrued benefit cost		(690)		(324)
Pretax amounts recognized in accumulated other comprehensive loss:
Net actuarial loss		517	[1]	537
Prior service cost (credit)		(295)	[1]	(238)
Pension Benefits | LOOP LLC and Explorer Pipeline
Pretax amounts recognized in accumulated other comprehensive loss:
Net actuarial loss	[1]	18
Other Benefits
Change in benefit obligations:
Benefit obligations at January 1		826		740
Service cost		30		25	32
Interest cost		30		30	35
Actuarial (gain) loss		(71)		61
Benefits paid		(36)		(30)
Plan amendments		34		0
Acquisitions		71		0
Benefit obligations at December 31		884		826	740
Change in plan assets:
Fair value of plan assets at January 1		0		0
Actual return on plan assets		0		0
Employer contributions		36		30
Benefits paid from plan assets		(36)		(30)
Acquisitions		0		0
Fair value of plan assets at December 31		0		0	$ 0
Funded status of plans at December 31		(884)		(826)
Amounts recognized in the consolidated balance sheets:
Current liabilities		(44)		(33)
Noncurrent liabilities		(840)		(793)
Accrued benefit cost		(884)		(826)
Pretax amounts recognized in accumulated other comprehensive loss:
Net actuarial loss		9	[1]	80
Prior service cost (credit)		35	[1]	$ (3)
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 $18 million and less than $1 million were recorded in accumulated other comprehensive loss in 2018, reflecting our ownership share.

Defined Benefit Pension And O_5

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, 2018	Dec. 31, 2017	Dec. 31, 2016
Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax):
Amortization of prior service credit		$ 36	$ 42
Pension Benefits
Components of net periodic benefit cost:
Service cost		159	132	$ 114
Interest cost		83	75	73
Expected return on plan assets		(109)	(100)	(98)
Amortization – prior service credit		(33)	(39)	(46)
Amortization – actuarial loss		31	36	38
Amortization – settlement loss		53	52	7
Net periodic benefit cost	[1]	184	156	88
Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax):
Actuarial (gain) loss		64	(20)	(33)
Prior service cost (credit)		(90)	0	0
Amortization of actuarial gain (loss)		(84)	(88)	(45)
Amortization of prior service credit		33	39	46
Other		0	0	0
Total recognized in other comprehensive loss		(77)	(69)	(32)
Total recognized in net periodic benefit cost and other comprehensive loss		107	87	56
Estimated net gain (loss) that will be amortized from accumulated other comprehensive loss in 2017		18
Estimated prior service cost that will be amortized from accumulated other comprehensive loss in 2017		45
Other Benefits
Components of net periodic benefit cost:
Service cost		30	25	32
Interest cost		30	30	35
Expected return on plan assets		0	0	0
Amortization – prior service credit		(3)	(3)	(3)
Amortization – actuarial loss		(1)	(2)	2
Amortization – settlement loss		0	0	0
Net periodic benefit cost	[1]	56	50	66
Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax):
Actuarial (gain) loss		(71)	61	(101)
Prior service cost (credit)		34	0	0
Amortization of actuarial gain (loss)		1	2	(2)
Amortization of prior service credit		3	3	3
Other		0	0	0
Total recognized in other comprehensive loss		(33)	66	(100)
Total recognized in net periodic benefit cost and other comprehensive loss		23	$ 116	$ (34)
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		$ 0
[1]	Net periodic benefit cost reflects a calculated market-related value of plan assets which recognizes changes in fair value over three years.

Defined Benefit Pension And O_6

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, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits
Weighted-average assumptions used to determine benefit obligation:
Discount rate	4.21%	3.55%	3.90%
Rate of compensation increase	5.00%	5.00%	5.00%
Weighted-average assumptions used to determine net periodic benefit cost:
Discount rate	3.88%	3.85%	3.80%
Expected long-term return on plan assets	6.15%	6.50%	6.50%
Rate of compensation increase	4.80%	5.00%	5.00%
Other Benefits
Weighted-average assumptions used to determine benefit obligation:
Discount rate	4.26%	3.70%	4.25%
Rate of compensation increase	5.00%	5.00%	5.00%
Weighted-average assumptions used to determine net periodic benefit cost:
Discount rate	3.72%	4.25%	4.50%
Expected long-term return on plan assets	0.00%	0.00%	0.00%
Rate of compensation increase	5.00%	5.00%	5.00%

Defined Benefit Pension and O_7

Defined Benefit Pension and Other Postretirement Plans (Expected Long-Term Return on Plan Assets) (Details)	12 Months Ended
	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Defined benefit plan, plan assets, expected long-term rate-of-return, description	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 O_8

Defined Benefit Pension And Other Postretirement Plans (Summarizes Assumed Health Care Cost Trend Rates) (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Medical Pre-65
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for the following year:	6.80%	6.75%	7.00%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate):	4.50%	4.50%	4.50%
Year that the rate reaches the ultimate trend rate:	2,027	2,026	2,026
Prescription drugs
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for the following year:	9.50%	8.75%	9.00%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate):	4.50%	4.50%	4.50%
Year that the rate reaches the ultimate trend rate:	2,027	2,026	2,026
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 O_9

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, 2018USD ($)
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	34
Effect on total of service and interest cost components, 1-Percentage-Point Decrease	(4)
Effect on other postretirement benefit obligations, 1-Percentage-Point-Decrease	$ (30)

Defined Benefit Pension and _10

Defined Benefit Pension and Other Postretirement Plans (Plan Investment Policies And Strategies) (Details)	12 Months Ended
	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, investment goals	<div style="line-height:120%;padding-top:12px;text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">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.</font></div></div>" id="sjs-B4">&lt;div style="font-family:Times New Roman;font-size:10pt;">&lt;div style="line-height:120%;padding-top:12px;text-align:left;font-size:10pt;">&lt;font style="font-family:inherit;font-size:10pt;">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&#8217; 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.&lt;/font>&lt;/div>&lt;/div>
Equity Securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Targeted asset allocation	42.00%
Fixed Income Securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Targeted asset allocation	58.00%

Defined Benefit Pension And _11

Defined Benefit Pension And Other Postretirement Plans (Fair Values Of Defined Benefit Pension Plan Assets) (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	$ 2,089	$ 1,840
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	25	14
Equity investments, common stocks
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	175	36
Equity funds, mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	159	227
Equity funds, pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	297	507
Fixed income, corporate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	860	674
Fixed income, government
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	239	98
Fixed income, pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	201	176
Private equity
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	41	51
Real estate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	29	34
Other
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	63	23
Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	567	265
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	89	36
Level 1 | Equity funds, mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	159	227
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	176	0
Level 1 | Fixed income, government
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	98	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	45	2
Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	1,434	1,470
Level 2 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	25	14
Level 2 | Equity investments, common stocks
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	86	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	297	507
Level 2 | Fixed income, corporate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	684	673
Level 2 | Fixed income, government
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	141	98
Level 2 | Fixed income, pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	201	176
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	0	2
Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	88	105	$ 118
Level 3 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 3 | Equity investments, common stocks
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 3 | Equity funds, mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 3 | Equity funds, pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	0
Level 3 | Fixed income, corporate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	0	1
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	41	51	60
Level 3 | Real estate
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	29	34	$ 39
Level 3 | Other
Defined Benefit Plan Disclosure [Line Items]
Plan asset investments, at fair value	$ 18	$ 19

Defined Benefit Pension And _12

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, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	$ 1,840
Actual return on plan assets:
Fair value of plan assets at December 31	2,089	$ 1,840
Private equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	51
Actual return on plan assets:
Fair value of plan assets at December 31	41	51
Real estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	34
Actual return on plan assets:
Fair value of plan assets at December 31	29	34
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	105	118
Actual return on plan assets:
Realized	11	14
Unrealized	1	0
Purchases	2	4
Sales	(31)	(31)
Fair value of plan assets at December 31	88	105
Level 3 | Private equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	51	60
Actual return on plan assets:
Realized	9	11
Unrealized	2	(1)
Purchases	1	2
Sales	(22)	(21)
Fair value of plan assets at December 31	41	51
Level 3 | Real estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	34	39
Actual return on plan assets:
Realized	2	3
Unrealized	(1)	0
Purchases	1	1
Sales	(7)	(9)
Fair value of plan assets at December 31	29	34
Level 3 | Fixed income corporate and other plan assets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	20	19
Actual return on plan assets:
Realized	0	0
Unrealized	0	1
Purchases	0	1
Sales	(2)	(1)
Fair value of plan assets at December 31	$ 18	$ 20

Defined Benefit Pension and _13

Defined Benefit Pension and Other Postretirement Plans (Contributions To Defined Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions to defined contribution plans	$ 144	$ 116	$ 113
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension contributions	115
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	19
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	$ 44

Defined Benefit Pension And _14

Defined Benefit Pension And Other Postretirement Plans (Estimated Future Benefit Payments) (Detail) $ in Millions	Dec. 31, 2018USD ($)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
2,019	$ 238
2,020	254
2,021	219
2,022	218
2,023	213
2024 through 2028	1,048
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
2,019	44
2,020	46
2,021	48
2,022	50
2,023	51
2024 through 2028	$ 271

Defined Benefit Pension And _15

Defined Benefit Pension And Other Postretirement Plans (Multiemployee Plans) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)Plan	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
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	<div style="line-height:120%;padding-top:12px;text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">There have been no significant changes that affect the comparability of </font><font style="font-family:inherit;font-size:10pt;">2018</font><font style="font-family:inherit;font-size:10pt;">, </font><font style="font-family:inherit;font-size:10pt;">2017</font><font style="font-family:inherit;font-size:10pt;"> and </font><font style="font-family:inherit;font-size:10pt;">2016</font><font style="font-family:inherit;font-size:10pt;"> contributions.</font></div></div>" id="sjs-B9">&lt;div style="font-family:Times New Roman;font-size:10pt;">&lt;div style="line-height:120%;padding-top:12px;text-align:left;font-size:10pt;">&lt;font style="font-family:inherit;font-size:10pt;">There have been no significant changes that affect the comparability of &lt;/font>&lt;font style="font-family:inherit;font-size:10pt;">2018&lt;/font>&lt;font style="font-family:inherit;font-size:10pt;">, &lt;/font>&lt;font style="font-family:inherit;font-size:10pt;">2017&lt;/font>&lt;font style="font-family:inherit;font-size:10pt;"> and &lt;/font>&lt;font style="font-family:inherit;font-size:10pt;">2016&lt;/font>&lt;font style="font-family:inherit;font-size:10pt;"> contributions.&lt;/font>&lt;/div>&lt;/div>
Multiemployer Plans, Postretirement Benefit
Defined Benefit Plan Disclosure [Line Items]
Number of multiemployer defined benefit pension or health and welfare plan	1
MPC contributions | $	$ 6	$ 7	$ 6

Defined Benefit Pension And _16

Defined Benefit Pension And Other Postretirement Plans (Multi Employer Pension Plan) (Detail)	12 Months Ended
	Dec. 31, 2018USD ($)Employee		Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
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, 2024
Multiemployer Plans, Pension
Multiemployer Plans [Line Items]
Multiemployer pension plan, minimum contribution requirement per week per employee	$ 328
Number of employees participated in the plan | Employee	258
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 $328 per week per employee for 2019. A total of 258 employees participated in the plan as of December 31, 2018.

Stock-Based Compensation Plan_2

Stock-Based Compensation Plans (Narrative) (Detail) shares in Millions	12 Months Ended
	Dec. 31, 2018$ / 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 Unit Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target payout | $ / shares	$ 1
Maximum | Performance Unit Awards
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 Unit Awards
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 Plan_3

Stock-Based Compensation Plans (Stock-Based Compensation Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-based compensation expense	$ 133	$ 51	$ 45
Tax benefit recognized on stock-based compensation expense	32	19	17
Cash received by MPC upon exercise of stock option awards	24	46	10
Tax benefit received for tax deductions for stock awards exercised	$ 14	$ 25	$ 4

Stock-Based Compensation Plan_4

Stock-Based Compensation Plans (Weighted Average Assumptions Used To Value Stock Options Awards) (Detail) - Stock Options - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average exercise price per share	$ 67.71	$ 50.57	$ 35.27
Expected life in years	6 years 2 months 14 days	6 years 3 months 20 days	6 years 2 months 14 days
Expected volatility	34.00%	35.00%	38.00%
Expected dividend yield	3.00%	3.00%	3.00%
Risk-free interest rate	2.70%	2.10%	1.40%
Weighted average grant date fair value of stock option awards granted	$ 17.21	$ 13.42	$ 9.84
Implied volatility rate weighting (in percentage)	50.00%
Historical volatility rate weighting (in percentage)	50.00%

Stock-Based Compensation Plan_5

Stock-Based Compensation Plans (Summary Of Stock Option Award Activity) (Detail) - Stock Options - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of options exercised	$ 44	$ 75	$ 14
Unrecognized compensation cost	$ 10
Weighted average recognition period, in years	1 year 2 months 14 days
Number of Shares
Outstanding, beginning balance	8,465,398
Granted	903,797
Converted in acquisition	302,403
Exercised	(916,566)
Forfeited or expired	(30,437)
Outstanding, ending balance	8,724,595	8,465,398
Vested and expected to vest at December 31, 2018 (in shares)	8,707,148
Exercisable at December 31, 2018 (in shares)	6,586,859
Weighted Average Exercise Price
Outstanding, beginning balance (in USD per share)	$ 33.74
Granted (in USD per share)	67.71	$ 50.57	$ 35.27
Converted in acquisition (in USD per share)	7
Exercised (in USD per share)	26.24
Forfeited or expired (in USD per share)	48.96
Outstanding, ending balance (in USD per share)	37.07	$ 33.74
Vested and expected to vest at December 31, 2018 (in USD per share)	37.01
Exercisable at December 31, 2018 (in USD per share)	$ 31.42
Weighted Average Remaining Contractual Terms (in years)
Vested and expected to vest at December 31, 2018 (in years)	5 years 1 month
Exercisable at December 31, 2018 (in years)	4 years
Aggregate Intrinsic Value (in millions)
Vested and expected to vest at December 31, 2018 (in USD)	$ 199
Exercisable at December 31, 2018 (in USD)	$ 182

Stock-Based Compensation Plan_6

Stock-Based Compensation Plans (Summary Of Restricted Stock Award Activity) (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted units outstanding	4,226,856
Restricted Stock
Number of Shares
Outstanding, beginning balance	1,188,662
Granted	470,951
Converted in acquisition	16,972
RS Vested/RSUs Issued	(624,934)
Forfeited	(60,951)
Outstanding, ending balance	990,700	1,188,662
Weighted Average Grant Date Fair Value
Outstanding, beginning balance (in USD per share)	$ 45.07
Granted (in USD per share)	71.19	$ 50.25	$ 36.17
Converted in acquisition (in USD per share)	82.43
RS's Vested/RSU's Issued (in USD per share)	45.98
Forfeited (in USD per share)	50.27
Outstanding, ending balance (in USD per share)	$ 57.23	$ 45.07
Restricted Stock Units
Number of Shares
Outstanding, beginning balance	285,164
Granted	24,430
Converted in acquisition	4,452,751
RS Vested/RSUs Issued	(526,254)
Forfeited	(9,235)
Outstanding, ending balance	4,226,856	285,164
Weighted Average Grant Date Fair Value
Outstanding, beginning balance (in USD per share)	$ 29.95
Granted (in USD per share)	72.43	$ 53.19	$ 40.85
Converted in acquisition (in USD per share)	82.43
RS's Vested/RSU's Issued (in USD per share)	65.34
Forfeited (in USD per share)	82.43
Outstanding, ending balance (in USD per share)	$ 80.96	$ 29.95
Non-Employee Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted units vested	1,106,740
Weighted average fair value, vested	$ 76.90

Stock-Based Compensation Plan_7

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, 2018	Dec. 31, 2017	Dec. 31, 2016
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic Value of Awards Vested During the Period (in millions)	$ 49	$ 28	$ 17
Weighted Average Grant Date Fair Value of Awards Granted During the Period	$ 71.19	$ 50.25	$ 36.17
Unrecognized compensation cost	$ 35
Weighted average recognition period, in years	1 year 1 month 28 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)	$ 39	$ 5	$ 8
Weighted Average Grant Date Fair Value of Awards Granted During the Period	$ 72.43	$ 53.19	$ 40.85
Unrecognized compensation cost	$ 110
Weighted average recognition period, in years	1 year 1 month 6 days

Stock-Based Compensation Plan_8

Stock-Based Compensation Plans (Summary Of Performance Unit Awards) (Detail) - Performance Unit Awards - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued in period	146,053
Unrecognized compensation cost	$ 3
Weighted average recognition period, in years	1 year 3 months
Number of Shares
Outstanding, beginning balance	6,851,542
Granted	3,830,000
Vested	(2,052,959)
Forfeited	(10,000)
Outstanding, ending balance	8,618,583	6,851,542
Weighted Average Grant Date Fair Value
Outstanding, beginning balance (in USD per share)	$ 0.81
Granted (in USD per share)	0.83	$ 0.92	$ 0.57
Vested (in USD per share)	0.95
Canceled (in USD per share)	0.92
Outstanding, ending balance (in USD per share)	$ 0.79	$ 0.81

Stock-Based Compensation Plan_9

Stock-Based Compensation Plans (Weighted Average Assumptions Used to Value Performance Unit Awards) (Details) - Performance Unit Awards - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.30%	1.50%	1.00%
Look-back period (in years)	2 years 9 months 30 days	2 years 9 months 30 days	2 years 9 months 30 days
Expected volatility	34.00%	36.10%	34.20%
Grant date fair value of performance units granted	$ 0.83	$ 0.92	$ 0.57

Leases (Schedule Of Future Mini

Leases (Schedule Of Future Minimum Commitments) (Detail) $ in Millions	Dec. 31, 2018USD ($)
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2,019	$ 70
2,020	71
2,021	66
2,022	75
2,023	82
Later years	586
Total minimum lease payments	950
Less imputed interest costs	(301)
Present value of net minimum lease payments	649
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2,019	709
2,020	619
2,021	553
2,022	389
2,023	295
Later years	858
Total minimum lease payments	$ 3,423

Leases (Schedule Of Operating L

Leases (Schedule Of Operating Lease Rental Expense) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Leases [Abstract]
Rental expense	$ 546	$ 367	$ 370

Leases (Narrative) (Details)

Leases (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Leases [Abstract]
Operating lease revenue	$ 221	$ 218	$ 246
Contingent lease payments received	$ 10	$ 9

Leases (Minimum Future Rentals

Leases (Minimum Future Rentals On The Non-Cancellable Operating Leases) (Details) $ in Millions	Dec. 31, 2018USD ($)
Leases [Abstract]
2,019	$ 160
2,020	159
2,021	150
2,022	148
2,023	142
Later years	1,111
Total minimum lease payments	$ 1,870

Leases (Investments In Assets H

Leases (Investments In Assets Held For Operating Lease By Major Classes) (Details) $ in Millions	Dec. 31, 2018USD ($)
Operating Leased Assets [Line Items]
Property, plant and equipment, gross	$ 1,641
Less accumulated depreciation	219
Property, plant and equipment, net	1,422
Natural gas gathering and NGL transportation pipelines and facilities
Operating Leased Assets [Line Items]
Property, plant and equipment, gross	965
Natural gas processing facilities
Operating Leased Assets [Line Items]
Property, plant and equipment, gross	481
Terminal and related assets
Operating Leased Assets [Line Items]
Property, plant and equipment, gross	133
Land, building, office equipment and other
Operating Leased Assets [Line Items]
Property, plant and equipment, gross	43
Construction in progress
Operating Leased Assets [Line Items]
Property, plant and equipment, gross	$ 19

Commitments and Contingencies (

Commitments and Contingencies (Detail)	12 Months Ended
	Dec. 31, 2018
Pending Litigation
Loss Contingencies [Line Items]
Loss contingency, inestimable loss	<div style="line-height:120%;padding-top:12px;text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">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.</font></div></div>" id="sjs-B5">&lt;div style="font-family:Times New Roman;font-size:10pt;">&lt;div style="line-height:120%;padding-top:12px;text-align:left;font-size:10pt;">&lt;font style="font-family:inherit;font-size:10pt;">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.&lt;/font>&lt;/div>&lt;/div>

Commitments and Contingencies_2

Commitments and Contingencies (Environmental Matters) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Accrued liabilities for remediation	$ 455	$ 114
Receivables for recoverable costs	$ 35	$ 45

Commitments and Contingencies_3

Commitments and Contingencies (Lawsuits) (Details) - Emergency Pricing And Consumer Protection Laws - Pending Litigation $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Loss Contingencies [Line Items]
Plaintiff	Commonwealth of Kentucky
Damages sought	$ 89
Loss contingency, period of occurrence	during September and October 2005

Commitments and Contingencies_4

Commitments and Contingencies (Guarantees) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Crowley Blue Water Partners
Loss Contingencies [Line Items]
Equity method investments, ownership percentage	50.00%
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
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	123
Guarantee of Indebtedness of Others | Financial Guarantee | LOOP and LOCAP LLC
Loss Contingencies [Line Items]
Maximum potential undiscounted payments	171
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	$ 128

Commitments and Contingences (C

Commitments and Contingences (Contractual Commitments and Contingencies) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Contractual commitments to acquire property, plant and equipment and advance funds to equity method investees	$ 1,800	$ 484

Selected Quarterly Financial _3

Selected Quarterly Financial Data (Schedule Of Quarterly Financial Information) (Detail) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended																12 Months Ended
		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Data [Abstract]
Sales and other operating revenues	[1]	$ 32,333		$ 22,988		$ 22,317		$ 18,866		$ 21,055		$ 19,210		$ 18,180		$ 16,288
Income from operations		2,017		1,403		1,711		440		1,168		1,577		982		291		$ 5,571	$ 4,018	$ 2,386
Net income		1,195		941		1,235		235		2,125	[2]	1,004		574		101		3,606	3,804	1,213
Net income attributable to MPC		$ 951		$ 737		$ 1,055		$ 37		$ 2,016	[2]	$ 903		$ 483		$ 30		$ 2,780	$ 3,432	$ 1,174
Net income attributable to MPC per share:
Net income attributable to MPC per share – basic		$ 1.38	[3]	$ 1.63	[3]	$ 2.30	[3]	$ 0.08	[3]	$ 4.13	[3]	$ 1.79	[3]	$ 0.94	[3]	$ 0.06	[3]	$ 5.36	$ 6.76	$ 2.22
Net income attributable to MPC per share – diluted		$ 1.35	[3]	$ 1.62	[3]	$ 2.27	[3]	$ 0.08	[3]	$ 4.09	[3]	$ 1.77	[3]	$ 0.93	[3]	$ 0.06	[3]	$ 5.28	$ 6.70	$ 2.21
Change in enacted tax rate, amount										$ 1,500									$ 1,500
[1]	Includes sales to related parties. The 2018 periods reflect an election to present certain taxes on a net basis concurrent with our adoption of ASC 606.
[2]	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.
[3]	The sum of the per-share amounts for the four quarters may not always equal the annual per-share amounts due to differences in the average number of shares outstanding during the respective periods.