Marathon Petroleum (MPC) 10-K 28 Feb 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2019	Feb. 17, 2020	Jun. 30, 2019
Document And Entity Information [Abstract]
Entity Central Index Key	0001510295
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus (Q1,Q2,Q3,FY)	FY
Amendment Flag	false
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	001-35054
Entity Registrant Name	Marathon Petroleum Corporation
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	27-1284632
Entity Address, Address Line One	539 South Main Street
Entity Address, City or Town	Findlay
Entity Address, State or Province	OH
Entity Address, Postal Zip Code	45840-3229
City Area Code	419
Local Phone Number	422-2121
Title of 12(b) Security	Common Stock, par value $.01
Trading Symbol	MPC
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 36.7
Entity Common Stock, Shares Outstanding		649,503,967

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues and other income:
Sales and other operating revenues, excluding consumer excise taxes	$ 123,949	$ 96,504
Sales and other operating revenue, including excise taxes			$ 74,733
Income from equity method investments	394	373	306
Net gain on disposal of assets	307	23	10
Other income	163	202	320
Total revenues and other income	124,813	97,102	75,369
Costs and expenses:
Cost of revenues (excludes items below)	110,243	86,066	67,089
Impairment expense	1,197	0	0
Depreciation and amortization	3,638	2,490	2,114
Selling, general and administrative expenses	3,408	2,418	1,694
Other taxes	751	557	454
Total costs and expenses	119,237	91,531	71,351
Income from operations	5,576	5,571	4,018
Net interest and other financial costs	1,247	1,003	674
Income before income taxes	4,329	4,568	3,344
Provision (benefit) for income taxes	1,074	962	(460)
Net income	3,255	3,606	3,804
Less net income attributable to:
Redeemable noncontrolling interest	81	75	65
Noncontrolling interests	537	751	307
Net income attributable to MPC	$ 2,637	$ 2,780	$ 3,432
Basic:
Net income attributable to MPC per share	$ 4	$ 5.36	$ 6.76
Weighted average shares outstanding (in shares)	659	518	507
Diluted:
Net income attributable to MPC per share	$ 3.97	$ 5.28	$ 6.70
Weighted average shares outstanding (in shares)	664	526	512

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 3,255	$ 3,606	$ 3,804
Defined benefit plans:
Actuarial changes, net of tax of ($40), $14 and $17, respectively	(147)	75	29
Prior service credit, net of tax of ($17), $12 and ($16), respectively	(27)	8	(26)
Other, net of tax of ($1), $1 and $0, respectively	(2)	4	0
Other comprehensive income (loss)	(176)	87	3
Comprehensive income	3,079	3,693	3,807
Less comprehensive income attributable to:
Redeemable noncontrolling interest	81	75	65
Noncontrolling interests	537	751	307
Comprehensive income attributable to MPC	$ 2,461	$ 2,867	$ 3,435

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Actuarial changes, tax	$ (40)	$ 14	$ 17
Prior service credit, tax	17	(12)	16
Other, tax	$ (1)	$ 1	$ 0

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents		$ 1,527	$ 1,687
Receivables, less allowance for doubtful accounts of $17 and $9, respectively		7,872	5,853
Inventories		10,243	9,837
Other current assets		528	646
Total current assets		20,170	18,023
Equity method investments		6,898	5,898
Property, plant and equipment, net		45,615	45,058
Goodwill		20,040	20,184
Right of use assets	[1]	2,459	0
Other noncurrent assets		3,374	3,777
Total assets		98,556	92,940
Current liabilities:
Accounts payable		11,623	9,366
Payroll and benefits payable		1,126	1,152
Accrued taxes		1,186	1,446
Debt due within one year		711	544
Operating lease liabilities	[1]	604	0
Other current liabilities		897	708
Total current liabilities		16,147	13,216
Long-term debt		28,127	26,980
Deferred income taxes		6,392	4,864
Defined benefit postretirement plan obligations		1,643	1,509
Long-term operating lease liabilities	[1]	1,875	0
Deferred credits and other liabilities		1,265	1,318
Total liabilities		55,449	47,887
Commitments and contingencies (see Note 26)
Redeemable noncontrolling interest		968	1,004
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 – 978 million and 975 million shares (par value $0.01 per share, 2 billion shares authorized)		10	10
Held in treasury, at cost – 329 million and 295 million shares		(15,143)	(13,175)
Additional paid-in capital		33,157	33,729
Retained earnings		15,990	14,755
Accumulated other comprehensive loss		(320)	(144)
Total MPC stockholders’ equity		33,694	35,175
Noncontrolling interests		8,445	8,874
Total equity		42,139	44,049
Total liabilities, redeemable noncontrolling interest and equity		$ 98,556	$ 92,940
[1]	We adopted ASU No. 2016-02, Leases (“ASC 842”), as of January 1, 2019. See Notes 3 and 25 for further information.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Millions, $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 17	$ 9
Preferred stock:
Shares issued	0	0
Shares outstanding	0	0
Par value	$ 0.01
Shares authorized	30
Common stock:
Shares issued	978	975
Par value	$ 0.01
Shares authorized	2,000
Treasury stock	(329)	(295)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities:
Net income	$ 3,255,000	$ 3,606,000	$ 3,804,000
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred financing costs and debt discount	33,000	70,000	64,000
Impairment expense	1,197,000	0	0
Depreciation and amortization	3,638,000	2,490,000	2,114,000
Pension and other postretirement benefits, net	(64,000)	90,000	47,000
Deferred income taxes	1,023,000	47,000	(1,233,000)
Net gain on disposal of assets	(307,000)	(23,000)	(10,000)
Income from equity method investments	(394,000)	(373,000)	(306,000)
Distributions from equity method investments	662,000	519,000	391,000
Changes in the fair value of derivative instruments	(8,000)	(62,000)	116,000
Changes in operating assets and liabilities, net of effects of businesses acquired:
Current receivables	(2,024,000)	1,589,000	(1,093,000)
Inventories	(366,000)	931,000	106,000
Current accounts payable and accrued liabilities	2,502,000	(2,798,000)	2,814,000
Right of use assets and operating lease liabilities, net	14,000	0	0
All other, net	280,000	72,000	(202,000)
Net cash provided by operating activities	9,441,000	6,158,000	6,612,000
Investing activities:
Additions to property, plant and equipment	(5,374,000)	(3,578,000)	(2,732,000)
Acquisitions, net of cash acquired	(129,000)	(3,822,000)	(249,000)
Disposal of assets	127,000	54,000	79,000
Investments – acquisitions, loans and contributions	(1,064,000)	(409,000)	(805,000)
Investments—redemptions, repayments and return of capital	98,000	16,000	62,000
All other, net	81,000	69,000	247,000
Net cash used in investing activities	(6,261,000)	(7,670,000)	(3,398,000)
Financing activities:
Commercial paper – issued	0	0	300,000
Commercial paper - repayments	0	0	(300,000)
Long-term debt – borrowings	14,274,000	13,476,000	2,911,000
Long-term debt – repayments	(13,073,000)	(8,032,000)	(642,000)
Debt issuance costs	(22,000)	(86,000)	(33,000)
Issuance of common stock	10,000	24,000	46,000
Common stock repurchased	(1,950,000)	(3,287,000)	(2,372,000)
Dividends paid	(1,398,000)	(954,000)	(773,000)
Issuance of MPLX LP common units	0	0	473,000
Distributions to noncontrolling interests	(1,245,000)	(903,000)	(694,000)
Contributions from noncontrolling interests	97,000	12,000	129,000
Contingent consideration payment	0	0	(89,000)
All other, net	(69,000)	(28,000)	(47,000)
Net cash provided by (used in) financing activities	(3,376,000)	222,000	(1,091,000)
Net increase (decrease) in cash, cash equivalents and restricted cash	(196,000)	(1,290,000)	2,123,000
Cash, cash equivalents and restricted cash at beginning of period	1,725,000	3,015,000	892,000
Cash, cash equivalents and restricted cash at end of period	$ 1,529,000	$ 1,725,000	$ 3,015,000

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, 2016	$ 20,203	$ 7	$ (7,482)	$ 11,060	$ 10,206	$ (234)	$ 6,646
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	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
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	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
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	3,174				2,637		537
Dividends declared on common stock	(1,402)				(1,402)
Distributions to noncontrolling interests	(1,164)						(1,164)
Contributions from noncontrolling interests	97						97
Other comprehensive income	(176)					(176)
Shares repurchased	(1,950)		(1,950)
Shares issued - stock based compensation		0		112
Shares returned - stock based compensation			(18)
Stock based compensation	101						7
Equity transactions of MPLX & ANDX	(590)			(684)			94
Ending balance at Dec. 31, 2019	$ 42,139	$ 10	$ (15,143)	$ 33,157	$ 15,990	$ (320)	$ 8,445

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, 2016		731
Shares issued - stock-based compensation		3
Ending balance at Dec. 31, 2017		734
Shares issued - stock-based compensation		1
Shares issued - acquisitions		240
Ending balance at Dec. 31, 2018	975	975
Shares issued - stock-based compensation		3
Ending balance at Dec. 31, 2019	978	978

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, 2016		(203)
Number of shares repurchased	(44)	(44)
Shares returned - stock-based compensation		(1)
Ending balance at Dec. 31, 2017		(248)
Number of shares repurchased	(47)	(47)
Shares returned - stock-based compensation		0
Ending balance at Dec. 31, 2018	(295)	(295)
Number of shares repurchased	(34)	(34)
Shares returned - stock-based compensation		0
Ending balance at Dec. 31, 2019	(329)	(329)

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interest - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Temporary Equity [Abstract]
Beginning balance	$ 1,004	$ 1,000	$ 1,000
Net income (loss) attributable to redeemable noncontrolling interest	81	75	65
Distributions to noncontrolling interests	(81)	(71)	(65)
Equity transactions of MPLX & ANDX	(36)
Ending balance	$ 968	$ 1,004	$ 1,000

Consolidated Statements of Eq_4

Consolidated Statements of Equity and Redeemable Noncontrolling Interest (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Stockholders' Equity [Abstract]
Dividends declared per share of common stock (in dollars per share)	$ 2.12	$ 1.84	$ 1.52

Description of the Business and

Description of the Business and Basis of Presentation	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
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. We sell refined products to wholesale marketing customers domestically and internationally, to buyers on the spot market, to consumers through our Retail business segment and to independent entrepreneurs who operate approximately 6,900 branded outlets. Our retail operations own and operate approximately 3,900 retail transportation fuel and convenience stores across the United States and also sell transportation fuel to consumers through approximately 1,070 direct dealer locations under long-term supply contracts. MPC’s midstream operations are primarily conducted through MPLX LP (“MPLX”), which owns and operates crude oil and refined product transportation and logistics infrastructure and natural gas and NGL gathering, processing, and fractionation assets. We own the general partner and a majority limited partner interest in MPLX. Refer to Note 5 for further information on the Andeavor acquisition, which closed on October 1, 2018, and to Notes 4 and 10 for additional information about our operations. On October 31, 2019, we announced plans to separate our retail transportation fuel and convenience store business, which is operated primarily under the Speedway brand, into an independent, publicly traded company through a tax-free distribution to MPC shareholders of publicly traded stock in the new independent retail transportation fuel and convenience store company. This transaction is targeted to be completed by year-end 2020, subject to market, regulatory and certain other conditions, including final approval by the MPC Board of Directors, receipt of customary assurances regarding the intended tax-free nature of the transaction, and the effectiveness of a registration statement to be filed with the SEC. The Speedway business is currently a reporting unit within our Retail segment. Subsequent to the completion of the separation, the historical results of the Speedway business will be presented as discontinued operations in our consolidated financial statements. Basis of Presentation 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, 2019
Accounting Policies [Abstract]
Summary Of Principal Accounting Policies	Principles Applied in Consolidation These consolidated financial statements include the accounts of our majority-owned, controlled subsidiaries and MPLX. As of December 31, 2019 , we owned the general partner and 63 percent of the outstanding MPLX common units. Due to our ownership of the general partner interest, we have determined that we control MPLX and therefore we consolidate MPLX and record a noncontrolling interest for the interest owned by the public. Changes in ownership interest in consolidated subsidiaries that do not result in a change in control are recorded as equity transactions. 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 any 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”), as of January 1, 2018, 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. Speedway offers a loyalty rewards program to its customers. We defer a minor portion of revenue on sales to the loyalty program participants until the participants redeem their rewards. The related contract liability, as defined in 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 20 for disclosure of our revenue disaggregated by segment and product line and to Note 10 for 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. 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 two years 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 using an income and/or market approach which is compared to the carrying value of the reporting unit. The fair value under the income approach 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 would 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. 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 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 the sale of allowances or credits are reported in investing activities - all other, net on the cash flow statement.

Accounting Standards

Accounting Standards	12 Months Ended
	Dec. 31, 2019
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recently Adopted Accounting Pronouncements	Recently Adopted ASU 2016-02, Leases We adopted ASU No. 2016-02, Leases (“ASC 842”), as of January 1, 2019, electing the transition method which permits entities to adopt the provisions of the standard using the modified retrospective approach without adjusting comparative periods. We also elected the package of practical expedients permitted under the transition guidance within the new standard, which among other things, allowed us to grandfather the historical accounting conclusions until a reassessment event is present. We have also elected the practical expedient to not recognize short-term leases on the balance sheet, the practical expedient related to right of way permits and land easements which allows us to carry forward our accounting treatment for those existing agreements, and the practical expedient to combine lease and non-lease components for the majority of our underlying classes of assets except for our third-party contractor service and equipment agreements and boat and barge equipment agreements in which we are the lessee. We did not elect the practical expedient to combine lease and non-lease components for arrangements in which we are the lessor. In instances where the practical expedient was not elected, lease and non-lease consideration is allocated based on relative standalone selling price. Right of use (“ROU”) assets represent our right to use an underlying asset in which we obtain substantially all of the economic benefits and the right to direct the use of the asset during the lease term. Lease liabilities represent our obligation to make lease payments arising from the lease. Operating lease ROU assets and lease liabilities are recognized at commencement date based on the present value of lease payments over the lease term. We recognize ROU assets and lease liabilities on the balance sheet for leases with a lease term of greater than one year. Payments that are not fixed at the commencement of the lease are considered variable and are excluded from the ROU asset and lease liability calculations. In the measurement of our ROU assets and lease liabilities, the fixed lease payments in the agreement are discounted using a secured incremental borrowing rate for a term similar to the duration of the lease, as our leases do not provide implicit rates. Operating lease expense is recognized on a straight-line basis over the lease term. Adoption of the new standard resulted in the recording of ROU assets and lease liabilities of approximately $2.8 billion and $2.9 billion , respectively, as of January 1, 2019. The standard did not materially impact our consolidated statements of income, cash flows or equity as a result of adoption. As a lessor under ASC 842, MPLX may be required to re-classify existing operating leases to sales-type leases upon modification and related reassessment of the leases. Modifications may result in the de-recognition of existing assets and recognition of a receivable in the amount of the present value of fixed payments expected to be received by MPLX under the lease. ASU 2017-04, Intangibles - Goodwill and Other - Simplifying the Test for Goodwill Impairment In connection with our annual goodwill impairment test, we adopted ASU 2017-04 prospectively during the fourth quarter of 2019. Under ASU 2017-04, 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 former 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. During the fourth quarter of 2019, we recorded certain goodwill impairment charges as described in Note 16 . We also adopted the following ASUs during 2019, none of which had a material impact to our financial statements or financial statement disclosures: ASU Effective Date 2018-02 Reporting Comprehensive Income - Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income January 1, 2019 2017-12 Derivatives and Hedging - Targeted Improvements to Accounting for Hedging Activities January 1, 2019
Not Yet Adopted Accounting Pronouncements	Not Yet Adopted ASU 2019-12, Income Taxes (Topic 740) - Simplifying the Accounting for Income Taxes In December 2019, the FASB issued new guidance to simplify the accounting for income taxes. Amendments include removal of certain exceptions to the general principles of ASC 740 and simplification in several other areas such as accounting for a franchise tax or similar tax that is partially based on income. The change is effective for fiscal years beginning after December 15, 2020, and interim periods within those fiscal years. Early adoption is permitted in any interim or annual period, with any adjustments reflected as of the beginning of the fiscal year of adoption. We do not expect the application of this ASU to have a material impact on our consolidated financial statements. ASU 2016-13, Credit Losses - Measurement of Credit Losses on Financial Instruments

Master Limited Partnership

Master Limited Partnership	12 Months Ended
	Dec. 31, 2019
Noncontrolling Interest [Abstract]
Master Limited Partnerships	We own the general partner and a majority limited partner interest in MPLX, which owns and operates crude oil and refined product transportation and logistics infrastructure and natural gas and NGL gathering, processing, and fractionation assets. We control MPLX through our ownership of the general partner interest and as of December 31, 2019 , we owned approximately 63 percent of the outstanding MPLX common units. MPLX’s Acquisition of ANDX On July 30, 2019, MPLX completed its acquisition of Andeavor Logistics LP (“ANDX”), and ANDX survived as a wholly-owned subsidiary of MPLX. At the effective time of the merger, each common unit held by ANDX’s public unitholders was converted into the right to receive 1.135 MPLX common units. ANDX common units held by MPC were converted into the right to receive 1.0328 MPLX common units. Additionally, 600,000 ANDX preferred units were converted into 600,000 preferred units of MPLX (“Series B preferred units”). Series B preferred unitholders are entitled to receive, when and if declared by the MPLX board, a fixed distribution of $68.75 per unit, per annum, payable semi-annually in arrears on February 15 and August 15, or the first business day thereafter, up to and including February 15, 2023. After February 15, 2023, the holders of Series B preferred units are entitled to receive cumulative, quarterly distributions payable in arrears on the 15th day of February, May, August and November of each year, or the first business day thereafter, based on a floating annual rate equal to the three month LIBOR plus 4.652 percent. MPC accounted for this transaction as a common control transaction, as defined by ASC 805, which resulted in an increase to noncontrolling interest and a decrease to additional paid-in capital of approximately $55 million , net of tax. During the third quarter of 2019, we pushed down to MPLX the portion of the goodwill attributable to ANDX as of October 1, 2018. Due to this push down of goodwill, we also recorded an incremental $642 million deferred tax liability associated with the portion of the non-deductible goodwill attributable to the noncontrolling interest in MPLX with an offsetting reduction of our additional paid-in capital balance. As described in Notes 5 and 6 , we have consolidated ANDX since the acquisition date of October 1, 2018 in accordance with ASC 810. Dropdowns to MPLX and GP/IDR Exchange On February 1, 2018, we contributed our refining logistics assets and fuels distribution services to MPLX in exchange for $4.1 billion in cash and approximately 112 million common units and 2 million general partner units from MPLX. MPLX financed the cash portion of the transaction with its $4.1 billion 364 -day term loan facility, which was entered into on January 2, 2018. We agreed to waive approximately one-third of the first quarter 2018 distributions on the common units issued in connection with this transaction. The contributions of these assets were accounted for as transactions between entities under common control and we did not record a gain or loss. Immediately following the February 1, 2018 dropdown to MPLX, our IDRs were cancelled and our economic general partner interest was converted into a non-economic general partner interest, all in exchange for 275 million newly issued MPLX common units (“GP/IDR Exchange”). As a result of this transaction, the general partner units and IDRs were eliminated, are no longer outstanding and no longer participate in distributions of cash from MPLX. On September 1, 2017, we contributed our joint-interest ownership in certain pipelines and storage facilities to MPLX in exchange for $420 million in cash and approximately 19 million 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 for 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. 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. With certain exceptions, these agreements generally contain minimum volume commitments. These transactions are eliminated in consolidation but are reflected as intersegment transactions between our Refining & Marketing and Midstream segments. 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 Corporate and Midstream segments. 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 to reflect these changes in ownership. Changes in MPC’s additional paid-in capital resulting from changes in its ownership interest in MPLX and ANDX were as follows: (In millions) 2019 2018 2017 Increase due to the issuance of MPLX common units and general partner units to MPC $ — $ 1,114 $ 114 Increase due to GP/IDR Exchange — 1,808 — Increase (decrease) due to the issuance of MPLX & ANDX common units (51 ) 6 25 Increase (decrease) in MPC's additional paid-in capital (51 ) 2,928 139 Tax impact (633 ) (571 ) (29 ) Increase (decrease) in MPC's additional paid-in capital, net of tax $ (684 ) $ 2,357 $ 110

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2019
Business Combinations [Abstract]
Acquisitions	Acquisition of Andeavor On October 1, 2018, we acquired 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 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 results 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. The size and the breadth of the Andeavor acquisition necessitated the use of the one year measurement period provided under ASC 805 to fully analyze all the factors used in establishing the asset and liability fair values as of the acquisition date. We completed a final determination of the fair value of certain assets and liabilities during the three months ended September 30, 2019 and recorded final adjustments to our preliminary purchase price allocation. These adjustments reflect the completion of valuation studies of the acquired property, plant and equipment in order to finalize assumptions used in their cost approach valuation methodology and finalization of specific valuation assumptions and data inputs for other individual asset valuation models. The fair value estimates of assets acquired and liabilities assumed as of the acquisition date are noted in the table below. (In millions) As originally reported Adjustments As adjusted Cash and cash equivalents $ 382 $ — $ 382 Receivables 2,744 (5 ) 2,739 Inventories 5,204 37 5,241 Other current assets 378 (6 ) 372 Equity method investments 865 (113 ) 752 Property, plant and equipment, net 16,545 (1,021 ) 15,524 Other noncurrent assets (a) 3,086 (11 ) 3,075 Total assets acquired 29,204 (1,119 ) 28,085 (In millions) As originally reported Adjustments As adjusted Accounts payable 4,003 (41 ) 3,962 Payroll and benefits payable 348 9 357 Accrued taxes 590 (110 ) 480 Debt due within one year 34 — 34 Other current liabilities 392 27 419 Long-term debt 8,875 1 8,876 Deferred income taxes 1,609 (60 ) 1,549 Defined benefit postretirement plan obligations 432 — 432 Deferred credit and other liabilities 714 33 747 Noncontrolling interests 5,059 3 5,062 Total liabilities and noncontrolling interest assumed 22,056 (138 ) 21,918 Net assets acquired excluding goodwill 7,148 (981 ) 6,167 Goodwill 16,314 981 17,295 Net assets acquired $ 23,462 $ — $ 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 purchase consideration allocation resulted in the recognition of $17.3 billion in goodwill, of which $1.0 billion is tax deductible due to a carryover basis from Andeavor. Our Refining & Marketing, Midstream and Retail segments recognized $5.2 billion , $8.1 billion and $3.9 billion of 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 fair value of property, plant and equipment was based primarily on the cost approach. Key assumptions in the cost approach included 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 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 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 definite 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, borrowings under revolving credit agreements and other debt were assumed to approximate fair value. Noncontrolling Interest Through the Andeavor acquisition, we acquired the general partnership interest of ANDX, which was a VIE because the limited partners of ANDX did not have substantive kick-out or substantive participating rights over the general partner. We were the primary beneficiary of ANDX because in addition to our significant economic interest, we also had 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 unit price, units outstanding and the percent of public unitholders of ANDX on October 1, 2018. 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. 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. 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) $ 131,921 $ 118,179 Net income attributable to MPC 4,218 4,712 (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 Terminal and Retail Locations in New York During the third quarter of 2019, we acquired a 900,000 -barrel capacity light product and asphalt terminal and 33 NOCO Express retail stores in Buffalo, Syracuse and Rochester, New York, from NOCO Incorporated for total consideration of $135 million . Based on the final fair value estimates of assets acquired and liabilities assumed at the acquisition date, $38 million of the purchase price was allocated to property, plant and equipment, $3 million to inventory and $94 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 terminal is accounted for within the R&M segment and the retail stores are accounted for within the Retail segment. The amount of revenue and income from operations associated with the acquisition from the acquisition date to December 31, 2019 did not have a material impact on the consolidated financial statements. In addition, assuming the acquisition had occurred on January 1, 2018, the consolidated pro forma results would not have been materially different from the reported results. Acquisition of Express Mart During the fourth quarter of 2018, Speedway acquired 78 transportation fuel and convenience 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 . At the time of the acquisition, the terminal included tanks with 4 million barrels of third-party leased storage capacity and a dock with 120 mbpd of capacity. 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. In the first quarter of 2019, an adjustment to the initial purchase price was made for approximately $5 million related to the final settlement of the acquisition. This reduced the total purchase price to $446 million and resulted in $336 million of property, plant and equipment, $121 million of goodwill and the remainder being attributable to net liabilities assumed. Goodwill 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 opportunity to construct an additional dock at the site. All of the goodwill recognized related to this transaction is tax deductible. 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 de-ethanization 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

Variable Interest Entities

Variable Interest Entities	12 Months Ended
	Dec. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
Variable Interest Entities	Consolidated VIE We control MPLX through our ownership of the general partner. MPLX is a VIE because the limited partners do not have substantive kick-out or substantive participating rights over the general partner. We are the primary beneficiary of MPLX because in addition to our significant economic interest, we also have the ability, through our ownership of the general partner, to control the decisions that most significantly impact MPLX. We therefore consolidate MPLX and record a noncontrolling interest for the interest owned by the public. We also record a redeemable noncontrolling interest related to MPLX’s Series A preferred units. The creditors of MPLX do not have recourse to MPC’s general credit through guarantees or other financial arrangements, except as noted. MPC has effectively guaranteed certain indebtedness of LOOP LLC (“LOOP”) and LOCAP LLC (“LOCAP”), in which MPLX holds an interest. See Note 26 for more information. The assets of MPLX can only be used to settle its own obligations and its creditors have no recourse to our assets, except as noted earlier. On July 30, 2019, MPLX acquired ANDX. We have consolidated ANDX since the acquisition date of October 1, 2018 in accordance with ASC 810. The ANDX balances at December 31, 2018 reflected in the table below are ANDX’s historical balances as the preliminary purchase accounting adjustments related to ANDX’s assets and liabilities in connection with the Andeavor acquisition had not yet been pushed down to ANDX. The MPLX balances at December 31, 2019 reflect the inclusion of ANDX’s balances at fair values determined in connection with MPC’s acquisition of Andeavor on October 1, 2018. See Notes 4 and 5 for additional information. The following table presents 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 MPLX ANDX Assets Cash and cash equivalents $ 15 $ 68 $ 10 Receivables, less allowance for doubtful accounts 615 425 199 Inventories 110 77 22 Other current assets 110 45 57 Equity method investments 5,275 4,174 602 Property, plant and equipment, net 22,174 14,639 6,845 Goodwill 9,536 2,586 1,051 Right of use assets 365 — — Other noncurrent assets 1,323 458 1,242 Liabilities Accounts payable $ 744 $ 776 $ 215 Payroll and benefits payable 5 2 10 Accrued taxes 80 48 23 Debt due within one year 9 1 504 Operating lease liabilities 66 — — Other current liabilities 259 177 77 Long-term debt 19,704 13,392 4,469 Deferred income taxes 12 13 1 Long-term operating lease liabilities 302 — — Deferred credits and other liabilities 409 276 68 Non-Consolidated VIEs Crowley Coastal Partners In May 2016, Crowley Coastal Partners LLC (“Crowley Coastal Partners”) 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, 2019 was $440 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. MPLX VIEs As a result of MPLX’s acquisition of ANDX, MPLX acquired an ownership interest in Rendezvous Gas Services, L.L.C. (“RGS”), Minnesota Pipe Line Company, LLC and Andeavor Logistics Rio Pipeline LLC (“ALRP”), among others. RGS and ALRP have been deemed to be VIEs, however, neither MPLX nor any of its subsidiaries have been deemed to be the primary beneficiary due to voting rights on significant matters. For all of the investments acquired through the merger, MPLX has the ability to exercise influence through participation in the management committees which make all significant decisions. However, since MPLX has equal or proportionate influence over each committee as a joint interest partner and all significant decisions require the consent of the other investors without regard to economic interest, we have determined that these entities should not be consolidated and we apply the equity method of accounting with respect to MPLX’s investment in each entity. In addition to the investments above, MarkWest Utica EMG, L.L.C., Sherwood Midstream, MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C. and Sherwood Midstream Holdings are also deemed to be VIEs. Consistent with the investments above, neither MPLX nor any of its subsidiaries are deemed to be the primary beneficiary due to voting rights on significant matters. Sherwood Midstream has been deemed the primary beneficiary of Sherwood Midstream Holdings due to its controlling financial interest through its authority to manage the joint venture. As a result, Sherwood Midstream consolidates Sherwood Midstream Holdings. MPLX’s maximum exposure to loss as a result of its involvement with equity method investments includes its equity investment, any additional capital contribution commitments and any operating expenses incurred by the subsidiary operator in excess of its compensation received for the performance of the operating services. We account for our ownership interest in each of these investments as an equity method investment. See Note 14 for ownership percentages and investment balances related to these VIEs.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2019
Related Party Transactions [Abstract]
Related Party Transactions	Transactions with related parties were as follows: (In millions) 2019 2018 2017 Sales to related parties $ 768 $ 754 $ 629 Purchases from related parties 763 610 570 Sales to related parties, which are included in sales and other operating revenues, consist 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.

Earnings per Share

Earnings per Share	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Earnings per 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) 2019 2018 2017 Basic earnings per share: Allocation of earnings: Net income attributable to MPC $ 2,637 $ 2,780 $ 3,432 Income allocated to participating securities 1 1 2 Income available to common stockholders – basic $ 2,636 $ 2,779 $ 3,430 Weighted average common shares outstanding 659 518 507 Basic earnings per share $ 4.00 $ 5.36 $ 6.76 Diluted earnings per share: Allocation of earnings: Net income attributable to MPC $ 2,637 $ 2,780 $ 3,432 Income allocated to participating securities 1 1 2 Income available to common stockholders – diluted $ 2,636 $ 2,779 $ 3,430 Weighted average common shares outstanding 659 518 507 Effect of dilutive securities 5 8 5 Weighted average common shares, including dilutive effect 664 526 512 Diluted earnings per share $ 3.97 $ 5.28 $ 6.70 The following table summarizes the shares that were anti-dilutive, and therefore, were excluded from the diluted share calculation. (In millions) 2019 2018 2017 Shares issuable under stock-based compensation plans 3 — 1

Equity

Equity	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Equity	As of December 31, 2019 , we had $2.96 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, tender offers, 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) 2019 2018 2017 Number of shares repurchased 34 47 44 Cash paid for shares repurchased $ 1,950 $ 3,287 $ 2,372 Average cost per share $ 58.87 $ 69.46 $ 53.85

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
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 Gulf Coast, Mid-Continent and West Coast regions of the United States, purchases refined products and ethanol for resale and distributes refined products 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. 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 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 from operations represents income from operations attributable to the reportable segments. Corporate administrative expenses, except for those attributable to MPLX, and costs related to certain non-operating assets are not allocated to the Refining & Marketing and Retail segments. In addition, certain items that affect comparability (as determined by the chief operating decision maker) are not allocated to the reportable segments. (In millions) Refining & Marketing Retail Midstream Total Year Ended December 31, 2019 Revenues: Third party (a) $ 87,056 $ 33,059 $ 3,834 $ 123,949 Intersegment 19,686 8 4,926 24,620 Segment revenues $ 106,742 $ 33,067 $ 8,760 $ 148,569 Segment income from operations $ 2,367 $ 1,582 $ 3,594 $ 7,543 Supplemental Data Depreciation and amortization (b) 1,665 528 1,267 3,460 Capital expenditures and investments (c) 1,999 607 3,290 5,896 (In millions) Refining & Marketing Retail Midstream Total Year Ended December 31, 2018 Revenues: Third party (a) $ 69,685 $ 23,546 $ 3,273 $ 96,504 Intersegment 12,914 6 3,387 16,307 Segment revenues $ 82,599 $ 23,552 $ 6,660 $ 112,811 Segment income from operations $ 2,481 $ 1,028 $ 2,752 $ 6,261 Supplemental Data 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 (a) $ 53,382 $ 19,029 $ 2,322 $ 74,733 Intersegment (d) 11,309 4 1,443 12,756 Segment revenues $ 64,691 $ 19,033 $ 3,765 $ 87,489 Segment income from operations $ 2,321 $ 729 $ 1,339 $ 4,389 Supplemental Data Depreciation and amortization (b) 1,082 275 699 2,056 Capital expenditures and investments (c) 832 381 1,755 2,968 (a) Includes related party sales. See Note 7 for additional information. (b) Differences between segment totals and MPC totals represent amounts related to unallocated items and are included in items not allocated to segment in the reconciliation below. (c) Includes changes in capital expenditure accruals and investments in affiliates. (d) Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties. The following reconciles segment income from operations to income before income taxes as reported in the consolidated statements of income: (In millions) 2019 2018 2017 Segment income from operations $ 7,543 $ 6,261 $ 4,389 Items not allocated to segments: Corporate and other unallocated items (a) (805 ) (502 ) (365 ) Equity method investment restructuring gains (b) 259 — — Transaction-related costs (c) (160 ) (197 ) — Litigation (22 ) — (29 ) Impairments (d) (1,239 ) 9 23 Income from operations 5,576 5,571 4,018 Net interest and other financial costs 1,247 1,003 674 Income before income taxes $ 4,329 $ 4,568 $ 3,344 (a) Corporate and other unallocated items consists primarily of MPC’s corporate administrative expenses and costs related to certain non-operating assets, except for corporate overhead expenses attributable to MPLX, which are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Retail segments. (b) Includes gains related to The Andersons Marathon Holdings LLC and Capline Pipeline Company LLC. See Note 14 . (c) 2019 includes costs incurred in connection with the proposed Speedway separation, Midstream strategic review and other related efforts. Both 2019 and 2018 include employee severance, retention and other costs related to the acquisition of Andeavor. Effective October 1, 2019, we have discontinued reporting Andeavor transaction-related costs as one year has passed since the Andeavor acquisition. The post October 1, 2019 transaction costs are immaterial and reported in corporate and other unallocated items. (d) 2019 reflects impairments of goodwill and equity method investments. See Notes 16 and 14 . 2018 and 2017 includes MPC’s share of gains from the sale of assets remaining from the Sandpiper pipeline project, which was cancelled and impaired in 2016. The following reconciles segment capital expenditures and investments to total capital expenditures: (In millions) 2019 2018 2017 Segment capital expenditures and investments $ 5,896 $ 4,147 $ 2,968 Less investments in equity method investees 1,064 409 305 Plus items not allocated to segments: Corporate 100 77 83 Capitalized interest 137 80 55 Total capital expenditures (a) $ 5,069 $ 3,895 $ 2,801 (a) Includes changes in capital expenditure accruals. See Note 21 for a reconciliation of total capital expenditures to additions to property, plant and equipment as reported in the consolidated statements of cash flows. No single customer accounted for more than 10 percent of annual revenues for the years ended December 31, 2019 , 2018 and 2017 . See Note 20 for the disaggregation of our revenue by segment and product line. 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, 2019
Other Income and Expenses [Abstract]
Net Interest and Other Financial Costs	Net interest and other financial costs was: (In millions) 2019 2018 2017 Interest income $ (40 ) $ (87 ) $ (27 ) Interest expense 1,396 1,026 688 Interest capitalized (158 ) (80 ) (63 ) Pension and other postretirement non-service costs (a) 3 53 49 Loss on extinguishment of debt — 64 — Other financial costs 46 27 27 Net interest and other financial costs $ 1,247 $ 1,003 $ 674 (a) See Note 23

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income tax provision (benefit) was: (In millions) 2019 2018 2017 Current: Federal $ (3 ) $ 715 $ 681 State and local 53 178 98 Foreign 1 22 (6 ) Total current 51 915 773 Deferred: Federal 898 2 (1,270 ) State and local 116 61 33 Foreign 9 (16 ) 4 Total deferred 1,023 47 (1,233 ) Income tax provision (benefit) $ 1,074 $ 962 $ (460 ) A reconciliation of the federal statutory income tax rate applied to income before income taxes to the provision for income taxes follows: 2019 2018 2017 Statutory rate applied to income before income taxes 21 % 21 % 35 % State and local income taxes, net of federal income tax effects 3 4 2 Goodwill impairment 3 — — Noncontrolling interests (3 ) (4 ) (4 ) TCJA legislation — — (45 ) Other 1 — (2 ) Provision for income taxes 25 % 21 % (14 )% Deferred tax assets and liabilities resulted from the following: December 31, (In millions) 2019 2018 Deferred tax assets: Employee benefits $ 693 $ 660 Environmental remediation 99 111 Debt financing 17 39 Net operating loss carryforwards 18 17 Foreign currency 15 28 Tax credit carryforwards 14 21 Other 57 88 Total deferred tax assets 913 964 Deferred tax liabilities: Property, plant and equipment 3,444 2,830 Inventories 652 678 Investments in subsidiaries and affiliates 3,114 2,130 Intangibles 56 97 Other 19 64 Total deferred tax liabilities 7,285 5,799 Net deferred tax liabilities $ 6,372 $ 4,835 Net deferred tax liabilities were classified in the consolidated balance sheets as follows: December 31, (In millions) 2019 2018 Assets: Other noncurrent assets $ 20 $ 29 Liabilities: Deferred income taxes 6,392 4,864 Net deferred tax liabilities $ 6,372 $ 4,835 At December 31, 2019 and 2018 , federal operating loss carryforwards were $7 million and $7 million , respectively, which expire in 2022 through 2038. As of December 31, 2019 and 2018 , state and local operating loss carryforwards were $11 million and $10 million , respectively, which expire in 2020 through 2038. As of December 31, 2019 and 2018 , $11 million and $10 million of valuation allowances have been recorded against foreign tax credits and state net operating losses due to the expectation that these deferred tax assets are not likely to be realized. MPC is continuously undergoing examination of its U.S. federal income tax returns by the Internal Revenue Service (“IRS”). Since 2012, we have continued to participate in the Compliance Assurance Process (“CAP”). CAP is a real-time audit of the U.S. Federal income tax return that allows the IRS, working in conjunction with MPC, to determine tax return compliance with the U.S. Federal tax law prior to filing the return. This program provides us with greater certainty about our tax liability for years under examination by the IRS. While Andeavor also underwent continual IRS examination, it did not participate in the CAP for tax periods prior to the October 1, 2018 acquisition of Andeavor. MPC’s IRS audits have been completed through the 2010 tax year. Andeavor and its subsidiaries’ IRS audits have been completed through the 2010 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, 2019 , our income tax returns remain subject to examination in the following major tax jurisdictions for the tax years indicated: United States Federal 2011 - 2018 States 2006 - 2018 The following table summarizes the activity in unrecognized tax benefits: (In millions) 2019 2018 2017 January 1 balance $ 211 $ 19 $ 7 Additions for tax positions of prior years 2 — 13 Reductions for tax positions of prior years (2 ) (5 ) — Settlements (19 ) — (1 ) Statute of limitations (160 ) (12 ) — Acquired from Andeavor — 209 — December 31 balance $ 32 $ 211 $ 19 If the unrecognized tax benefits as of December 31, 2019 were recognized, $23 million would affect our effective income tax rate. There were $2 million of uncertain tax positions as of December 31, 2019 for which it is reasonably possible that the amount of unrecognized tax benefits would significantly decrease during the next twelve months. For tax years 2009 and 2010, Andeavor had asserted a federal income tax claim for $159 million resulting from the income tax effect of the receipt of the ethanol blender’s excise tax credit, for which the tax benefit was not recorded. The statute of limitations for the IRS appeal process was allowed to expire during the fourth quarter 2019 since the ability to obtain a refund was remote. 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. In the third quarter of 2019, the U.S. Tax court entered a decision in favor of both Marathon Oil and us for all material items and the U.S. Internal Revenue Service is in the process of preparing the final reports for these tax years. 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 26 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 $(2) million , $1 million and $3 million in 2019 , 2018 and 2017 , respectively. As of December 31, 2019 and 2018 , $7 million and $18 million of interest and penalties were accrued related to income taxes.

Inventories

Inventories	12 Months Ended
	Dec. 31, 2019
Inventory Disclosure [Abstract]
Inventories	December 31, (In millions) 2019 2018 Crude oil $ 3,472 $ 3,655 Refined products 5,548 5,234 Materials and supplies 996 720 Merchandise 227 228 Total $ 10,243 $ 9,837 The LIFO method accounted for 90 percent and 92 percent of total inventory value at December 31, 2019 and 2018 , respectively. Current acquisition costs of inventories were estimated to exceed the LIFO inventory value at December 31, 2019 by $871 million . There was no excess of replacement or current cost over our stated LIFO cost at December 31, 2018

Equity Method Investments

Equity Method Investments	12 Months Ended
	Dec. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments	The Andersons Marathon Holdings LLC Effective October 1, 2019, The Andersons, Inc. and MPC contributed jointly owned equity interests in three ethanol entities into a new legal entity, The Andersons Marathon Holdings LLC (“TAMH”). Concurrently, The Andersons, Inc. contributed a wholly-owned ethanol facility to TAMH. In accordance with ASC 845, we derecognized the historical cost of our equity method investments in the legacy entities amounting to $123 million and recognized the new equity method investment in TAMH at fair value. We used a combination of market, income and cost approaches to determine the fair value of our ownership interest in TAMH with more reliance on the market and income approaches. The estimated cash flows used in the income approach were discounted using a weighted average cost of capital estimate and the market approach utilized EBITDA and capacity multiples for similar companies and transactions. This is a nonrecurring fair value measurement and is recognized in Level 3 of the fair value hierarchy. We estimated the fair value of our ownership interest to be $175 million . The excess of the estimated fair value of our ownership interest over the carrying value of the derecognized net assets resulted in a $52 million non-cash net gain recorded as a net gain on disposal of assets in the accompanying consolidated statements of income. Capline LLC During the three months ended March 31, 2019, we executed agreements with Capline Pipeline Company LLC (“Capline LLC”) to contribute our 33 percent undivided interest in the Capline pipeline system in exchange for a 33 percent ownership interest in Capline LLC. In connection with our execution of these agreements, Capline LLC initiated a binding open season for southbound service from Patoka, Illinois to St. James, Louisiana or Liberty, Mississippi with an additional origination point at Cushing, Oklahoma. Service from Cushing, Oklahoma is part of a joint tariff with Diamond pipeline. Crude oil service is expected to begin in the first half of 2021. In accordance with ASC 810, we derecognized our undivided interest amounting to $143 million of net assets and recognized the Capline LLC ownership interest we received at fair value. We used an income approach to determine the fair value of our ownership interest under a Monte Carlo simulation method. We estimated the fair value of our ownership interest to be $350 million . This is a nonrecurring fair value measurement and is categorized in Level 3 of the fair value hierarchy. The Monte Carlo simulation inputs include ranges of tariff rates, operating volumes, operating cost and capital expenditure assumptions. The estimated cash flows were discounted using a Monte Carlo market participant weighted average cost of capital estimate. None of the inputs to the Monte Carlo simulation are individually significant. The excess of the estimated fair value of our ownership interest over the carrying value of the derecognized net assets resulted in a $207 million non-cash net gain recorded as a net gain on disposal of assets in the accompanying consolidated statements of income. As the Capline system is currently idled, Capline LLC is unable to fund its operations without financial support from its equity owners and is a VIE. MPC is not deemed to be the primary beneficiary, due to our inability to unilaterally control significant decision-making rights. Our maximum exposure to loss as a result of our involvement with Capline LLC includes our equity investment, any additional capital contribution commitments and any operating expenses incurred by Capline LLC in excess of compensation received for performance of the operating services. Impairments During the fourth quarter of 2019, two joint ventures in which MPLX has an interest recorded impairments, which impacted the amount of income from equity method investments during the period by approximately $28 million . For one of the joint ventures, MPLX also had a basis difference which was being amortized over the life of the underlying assets. As a result of the impairment recorded by the joint venture, MPLX also assessed this basis difference for impairment and recorded approximately $14 million of impairment expense during the fourth quarter related to this investment. Investments in Equity Method Affiliates Ownership as of Carrying value at December 31, December 31, (Dollars in millions) 2019 2019 2018 Refining & Marketing The Andersons Marathon Holdings LLC 50% $ 177 $ — Watson Cogeneration Company 51% 26 84 Other (a) — 121 Refining & Marketing Total $ 203 $ 205 Retail PFJ Southeast LLC 29% $ 330 $ 341 Retail Total $ 330 $ 341 Midstream MPLX Andeavor Logistics Rio Pipeline LLC 67% $ 202 $ 181 Centrahoma Processing LLC 40% 153 160 Explorer Pipeline Company 25% 83 90 Illinois Extension Pipeline Company, L.L.C 35% 265 275 LOOP LLC 41% 238 226 MarEn Bakken Company LLC 25% 481 498 MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C. 67% 302 236 MarkWest Utica EMG, L.L.C. 56% 1,984 2,039 Minnesota Pipe Line Company, LLC 17% 190 197 Rendezvous Gas Services, L.L.C. 78% 170 248 Sherwood Midstream Holdings LLC 53% 157 157 Sherwood Midstream LLC 50% 537 366 Whistler Pipeline LLC 38% 134 — Wink to Webster Pipeline LLC 15% 126 — Other 253 228 MPLX Total $ 5,275 $ 4,901 MPC-Retained Capline Pipeline Company LLC 33% $ 374 $ — Crowley Coastal Partners, LLC 50% 188 190 Gray Oak Pipeline, LLC 25% 298 73 LOOP LLC 10% 59 56 Other 171 132 MPC-Retained Total $ 1,090 $ 451 Midstream Total $ 6,365 $ 5,352 Total $ 6,898 $ 5,898 (a) 2018 represents our investment in three ethanol entities jointly owned with The Andersons, Inc. In 2019, these entities were contributed into a new legal entity, The Andersons Marathon Holdings, LLC. Summarized financial information for all equity method investments in affiliated companies, combined, was as follows: (In millions) 2019 2018 2017 Income statement data: Revenues and other income $ 7,718 $ 7,726 $ 6,235 Income from operations 1,472 1,375 1,075 Net income 1,284 1,242 922 Balance sheet data – December 31: Current assets $ 1,333 $ 1,443 Noncurrent assets 17,216 12,408 Current liabilities 1,006 1,857 Noncurrent liabilities 2,772 1,788 As of December 31, 2019 , the carrying value of our equity method investments was $1.4 billion higher than the underlying net assets of investees. This basis difference is being amortized into net income over the remaining estimated useful lives of the underlying net assets, except for $700 million of excess related to goodwill and other non-depreciable assets. The basis difference reflects the preliminary purchase price allocation of Capline LLC, which will be completed in the one year measurement period as required by ASC 805, “Business Combinations”. Dividends and partnership distributions received from equity method investees (excluding distributions that represented a return of capital previously contributed) were $662 million , $519 million and $391 million in 2019 , 2018 and 2017 .

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	(In millions) Estimated Useful Lives December 31, 2019 2018 Refining & Marketing 4 - 30 years $ 29,037 $ 27,590 Retail 4 - 25 years 7,104 6,637 Midstream 2 - 51 years 27,193 25,692 Corporate and Other 4 - 40 years 1,289 1,294 Total 64,623 61,213 Less accumulated depreciation 19,008 16,155 Property, plant and equipment, net $ 45,615 $ 45,058 Property, plant and equipment includes gross assets acquired under finance leases of $806 million and $786 million at December 31, 2019 and 2018 , respectively, with related amounts in accumulated depreciation of $226 million and $202 million at December 31, 2019 and 2018 . Property, plant and equipment includes construction in progress of $3.48 billion and $3.49 billion at December 31, 2019 and 2018 , respectively, which primarily relates to capital projects at our refineries and midstream facilities.

Goodwill and Intangibles

Goodwill and Intangibles	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
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 2019, we recorded an impairment of goodwill as outlined below based on MPLX’s annual evaluation. There were no other impairments of goodwill required based on our annual test of goodwill in 2019. In 2018 , our annual testing did not indicate any impairment of goodwill. MPLX annually evaluates goodwill for impairment as of November 30, as well as whenever events or changes in circumstances indicate it is more likely than not that the fair value of a reporting unit with goodwill is less than the carrying amount. As a result of the merger of MPLX and ANDX and subsequent changes to MPLX’s internal organization structure, the number of reporting units within our Midstream segment was reduced from 16 to 7 in conjunction with the annual impairment test, however, this change in structure did not have any impact on MPC’s operating segments. Reporting units are determined based on the way in which segment management operates and reviews each operating segment. MPLX performed a goodwill impairment assessment prior to the change in reporting units in addition to performing an impairment assessment immediately following the change in their reporting units. Significant assumptions used to estimate the reporting units’ fair value include the discount rate as well as estimates of future cash flows, which are impacted primarily by producer customers’ development plans, which impact future volumes and capital requirements. After MPLX performed its evaluations related to the impairment of goodwill, we recorded an impairment of $1,156 million prior to the change in reporting units and additional impairment of $41 million subsequent to the change in reporting units. The remainder of the reporting units fair values were in excess of their carrying values. The impairment was primarily driven by the updated guidance related to the slowing of drilling activity which has reduced production growth forecasts from MPLX’s producer customers. The fair value of the reporting units for the annual goodwill impairment analysis described above was determined based on applying both a discounted cash flow or income approach as well as a market approach. The discounted cash flow fair value estimate is based on known or knowable information at the measurement date. The significant assumptions that were used to develop the estimates of the fair values under the discounted cash flow method included management’s best estimates of the expected future results and discount rates, which range from 9.0 percent to 10.0 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 annual goodwill impairment test will prove to be an accurate prediction of the future. The fair value measurements for the individual reporting units’ overall fair values, and the fair values of the goodwill assigned thereto, represent Level 3 measurements. The changes in the carrying amount of goodwill for 2018 and 2019 were as follows: (In millions) Refining & Marketing Retail Midstream Total Balance at January 1, 2018 $ 519 $ 791 $ 2,276 $ 3,586 Acquisitions 4,717 4,050 7,831 16,598 Dropdowns to MPLX (216 ) — 216 — Balance at December 31, 2018 $ 5,020 $ 4,841 $ 10,323 $ 20,184 Acquisitions 38 56 — 94 Purchase price allocation adjustments 514 54 408 976 Impairments — — (1,197 ) (1,197 ) Dispositions — — (17 ) (17 ) Balance at December 31, 2019 $ 5,572 $ 4,951 $ 9,517 $ 20,040 Intangible Assets Our definite lived intangible assets as of December 31, 2019 and 2018 are as shown below. December 31, 2019 December 31, 2018 (In millions) Gross Accumulated Amortization Net Gross Accumulated Amortization Net Customer contracts and relationships $ 3,273 $ 610 $ 2,663 $ 3,184 $ 261 $ 2,923 Brand rights and tradenames 155 55 100 208 33 175 Royalty agreements 133 78 55 129 70 59 Other 147 37 110 190 33 157 Total $ 3,708 $ 780 $ 2,928 $ 3,711 $ 397 $ 3,314 At December 31, 2019 and 2018 , we had indefinite lived intangible assets of $94 million and $94 million , respectively, which are primarily emission allowance credits and trademarks. Amortization expense for 2019 and 2018 was $372 million and $134 million , respectively. Estimated future amortization expense related to the intangible assets at December 31, 2019 is as follows: (In millions) 2020 $ 387 2021 380 2022 379 2023 363 2024 305

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
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, 2019 and 2018 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, 2019 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 Assets: Commodity contracts $ 57 $ 6 $ — $ (55 ) $ 8 $ 73 Liabilities: Commodity contracts $ 95 $ 11 $ — $ (106 ) $ — $ — Embedded derivatives in commodity contracts — — 60 — 60 — 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 Assets: Commodity contracts $ 370 $ 31 $ — $ (323 ) $ 78 $ 2 Liabilities: Commodity contracts $ 255 $ 37 $ — $ (284 ) $ 8 $ — Embedded derivatives in commodity contracts — — 61 — 61 — (a) Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of December 31, 2019 , $51 million was netted with mark-to-market liabilities. 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 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, 2019 used significant unobservable inputs including: (1) NGL prices interpolated and extrapolated due to inactive markets ranging from $0.43 to $1.23 per gallon and (2) the probability of renewal of 94 percent for the first five-year term and 83 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) 2019 2018 Beginning balance $ 61 $ 66 Unrealized and realized losses included in net income 5 3 Settlements of derivative instruments (6 ) (8 ) Ending balance $ 60 $ 61 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: $ 5 $ 8 See Note 18 for the income statement impacts of our derivative instruments. 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 $28.3 billion and $30.1 billion at December 31, 2019 , respectively, and approximately $27.0 billion and $26.5 billion at December 31, 2018 , 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, 2019
Summary of Derivative Instruments [Abstract]
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, 2019 and 2018 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, 2019 Balance Sheet Location Asset Liability Commodity derivatives Other current assets $ 63 $ 106 Other current liabilities (a) — 5 Deferred credits and other liabilities (a) — 55 (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 (a) Includes embedded derivatives. The table below summarizes open commodity derivative contracts for crude oil, refined products and blending products as of December 31, 2019 . Percentage of contracts that expire next quarter Position (Units in thousands of barrels) Long Short Exchange-traded (a) Crude oil 85.7% 26,287 27,237 Refined products 94.7% 15,298 12,519 Blending products 99.5% 1,976 3,770 (a) Included in exchange-traded are spread contracts in thousands of barrels: Crude oil - 5,130 long and 330 short; Refined products - 950 long and 450 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 2019 2018 2017 Sales and other operating revenues $ (19 ) $ 13 $ 5 Cost of revenues (77 ) (59 ) (26 ) Total $ (96 ) $ (46 ) $ (21 )

Debt

Debt	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Debt	Our outstanding borrowings at December 31, 2019 and 2018 consisted of the following: (In millions) December 31, December 31, Marathon Petroleum Corporation: Senior notes $ 8,474 $ 8,474 Notes payable 10 11 Finance lease obligations 679 629 MPLX LP: Term loan facility 1,000 — Senior notes 19,100 13,850 Finance lease obligations 19 6 ANDX LP: (a) Revolving and dropdown credit facilities — 1,245 Senior notes — 3,750 Finance lease obligations — 15 Total debt $ 29,282 $ 27,980 Unamortized debt issuance costs (134 ) (128 ) Unamortized discount (310 ) (328 ) Amounts due within one year (711 ) (544 ) Total long-term debt due after one year $ 28,127 $ 26,980 (a) On July 30, 2019, MPLX acquired ANDX and assumed its debt obligations. See Note 4 and the discussion below for additional information. MPC Senior Notes December 31, (In millions) 2019 2018 Marathon Petroleum Corporation: 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 337 337 Senior notes, 4.750% due December 2023 614 614 Senior notes, 5.125% due April 2024 241 241 Senior notes, 3.625%, due September 2024 750 750 Senior notes, 5.125% due December 2026 719 719 Senior notes, 3.800% due April 2028 496 496 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 498 498 Andeavor senior notes, 3.800% - 5.375% due 2022 - 2048 469 469 Senior notes, 5.000%, due September 2054 400 400 Total 8,474 8,474 In connection with the acquisition of Andeavor on October 1, 2018, we assumed an aggregate principal amount of $3.374 billion senior notes issued by Andeavor, with interest rates ranging from 3.800 percent to 5.375 percent and maturity dates ranging from 2022 to 2048. In October 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. After giving effect to the exchange offer, approximately $469 million aggregate principal of outstanding senior notes issued by Andeavor remain outstanding. 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 and 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 Term Loan On September 26, 2019, MPLX entered into a term loan agreement which provides for a committed term loan facility for up to an aggregate of $1 billion available to be drawn in up to four separate borrowings, subject to the satisfaction or waiver of certain customary conditions. Borrowings under the term loan agreement bear interest, at MPLX’s election, at either the Adjusted LIBO Rate (as defined in the term loan agreement) plus a margin or the Alternate Base Rate (as defined in the term loan agreement) plus a margin . The applicable margins to the benchmark interest rates fluctuate from time-to-time based on our credit ratings. The proceeds from borrowings under the term loan agreement were used to fund the repayment of MPLX’s existing indebtedness and/or for general business purposes. Amounts borrowed under the term loan agreement will be due and payable on September 26, 2021. As of December 31, 2019 , MPLX had drawn $1 billion on the term loan at an average interest rate of 2.561 percent . The term loan agreement contains representations and warranties, affirmative and negative covenants and events of default that we consider to be customary for an agreement of this type and are substantially similar to MPLX’s existing revolving credit facility, including a covenant that requires MPLX’s ratio of Consolidated Total Debt to Consolidated EBITDA (as both terms are defined in the term loan agreement) for the four prior fiscal quarters not to exceed 5.0 to 1.0 as of the last day of each fiscal quarter (or during the six-month period following certain acquisitions, 5.5 to 1.0). Consolidated EBITDA is subject to adjustments for certain acquisitions completed and capital projects undertaken during the relevant period. 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 Average December 31, (In millions) Rate 2019 2018 MPLX LP: Floating rate notes due September 2021 2.948 % 1,000 — Floating rate notes due September 2022 3.148 % 1,000 — Senior notes, 6.250% due October 2022 266 — Senior notes, 3.500% due December 2022 486 — Senior notes, 3.375% due March 2023 500 500 Senior notes, 4.500% due July 2023 989 989 Senior notes, 6.375% due May 2024 381 — Senior notes, 4.875% due December 2024 1,149 1,149 Senior notes, 5.250% due January 2025 708 — Senior notes, 4.000% due February 2025 500 500 Senior notes, 4.875% due June 2025 1,189 1,189 MarkWest senior notes, 4.500% - 5.500% due 2023 - 2025 23 23 Senior notes, 4.125% due March 2027 1,250 1,250 Senior notes, 4.250% due December 2027 732 — Senior notes, 4.000% due March 2028 1,250 1,250 Senior notes, 4.800% due February 2029 750 750 Senior notes, 4.500% due April 2038 1,750 1,750 Senior notes, 5.200% due March 2047 1,000 1,000 Senior notes, 5.200% due December 2047 487 — ANDX senior notes, 3.500% - 6.375% due 2019 - 2047 190 — Senior notes, 4.700% due April 2048 1,500 1,500 Senior notes, 5.500% due February 2049 1,500 1,500 Senior notes, 4.900% due April 2058 500 500 Total 19,100 13,850 On September 9, 2019, MPLX issued $2 billion aggregate principal amount of floating rate senior notes in a public offering, consisting of $1 billion aggregate principal amount of notes due September 2021 and $1 billion aggregate principal amount of notes due September 2022. Net proceeds from the issuance of the floating rate senior notes were used to repay MPLX’s existing indebtedness and/or for general business purposes. The interest rate applicable to the floating rate senior notes due September 2021 is LIBOR plus 0.9 percent per annum while the interest rate applicable to the floating rate senior notes due September 2022 is LIBOR plus 1.1 percent per annum. Interest is payable in March, June, September and December, commencing on December 9, 2019. Both series of floating rate notes are callable, in whole or in part, at par plus accrued and unpaid interest at any time on or after September 10, 2020. In connection with MPLX’s acquisition of ANDX on July 30, 2019, MPLX assumed ANDX’s outstanding senior notes, which had an aggregate principal amount of $3.75 billion , with interest rates ranging from 3.500 percent to 6.375 percent and maturity dates ranging from 2019 to 2047. On September 23, 2019, approximately $3.06 billion aggregate principal amount of ANDX’s outstanding senior notes were exchanged for new unsecured senior notes issued by MPLX having the same maturity and interest rates as the ANDX senior notes in an exchange offer and consent solicitation undertaken by MPLX, leaving approximately $690 million aggregate principal of outstanding senior notes issued by ANDX. Of this, $500 million was related to the 5.500 percent unsecured senior notes due 2019. The principal amount of $500 million and accrued interest of $14 million was paid on October 15, 2019, which included interest through the payoff date. On November 15, 2018, MPLX issued $2.25 billion in aggregate principal amount of senior notes in a public offering. 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. The make whole premium plus the write off of unamortized deferred financing costs resulted in a loss on extinguishment of debt of $60 million . The remaining net proceeds were 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. On February 8, 2018, $4.1 billion of the net proceeds were used to repay the 364-day term-loan facility entered into on January 2, 2018. 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 fixed rate 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 except as otherwise noted. Schedule of Maturities Principal maturities of long-term debt, excluding finance lease obligations, as of December 31, 2019 for the next five years are as follows: (In millions) 2020 $ 650 2021 3,008 2022 2,275 2023 2,350 2024 2,652 Available Capacity under our Facilities (Dollars in millions) Total Capacity Outstanding Borrowings Outstanding Letters of Credit Available Capacity Weighted Average Interest Rate Expiration MPC 364-day bank revolving credit facility $ 1,000 $ — $ — $ 1,000 — September 2020 MPC bank revolving credit facility 5,000 — 1 4,999 — October 2023 MPC trade receivables securitization facility 750 — — 750 — July 2021 MPLX bank revolving credit facility 3,500 — — 3,500 — July 2024 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 2019 , we had no borrowings or repayments under the commercial paper program. At December 31, 2019 , we had no amounts outstanding under the commercial paper program. MPC Revolving Credit Agreements On August 28, 2018, in connection with the Andeavor acquisition, MPC entered into a credit agreement with a syndicate of lenders providing for a $5 billion five-year revolving credit facility that expires in 2023. The five-year credit agreement became effective on October 1, 2018. On July 26, 2019, MPC entered into a credit agreement with a syndicate of lenders providing for a new $1 billion 364-day revolving credit facility that became effective upon the expiration of MPC’s previously existing $1 billion 364-day revolving credit facility in September 2019. The new 364-day credit agreement contains substantially the same terms and conditions as our previously existing 364-day revolving credit facility and will expire in September 2020. MPC has an option under its $5 billion 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 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 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 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 margins 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, 2019 , we were in compliance with the covenants contained in the MPC credit agreements. Trade Receivables Securitization Facility 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 borrowings under 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, 2019 , we were in compliance with the covenants contained in the receivables purchase agreement and receivables sale agreement. MPLX Credit Agreement Upon the completion of the merger of MPLX and ANDX on July 30, 2019, the MPLX bank revolving credit facility was amended and restated to increase the borrowing capacity to $3.5 billion and to extend the maturity date to July 30, 2024. The ANDX revolving and dropdown credit facilities were terminated and all outstanding balances were repaid and funded with borrowings under the amended and restated MPLX $3.5 billion bank revolving credit facility. The MPLX credit agreement includes letter of credit issuing capacity of up to approximately $300 million and swingline loan capacity of up to $150 million . The revolving borrowing capacity may be increased by up to an additional $1 billion , 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, 2019 , MPLX was in compliance with the covenants contained in the MPLX credit agreement.

Revenue

Revenue	12 Months Ended
	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Revenue	The following table presents our revenues disaggregated by segment and product line: (In millions) Refining & Marketing Retail Midstream Total Year Ended December 31, 2019 Refined products $ 82,169 $ 26,681 $ 809 $ 109,659 Merchandise 4 6,281 — 6,285 Crude oil 4,402 — — 4,402 Midstream services and other 481 97 3,025 3,603 Sales and other operating revenues $ 87,056 $ 33,059 $ 3,834 $ 123,949 (In millions) Refining & Marketing Retail Midstream Total Year Ended December 31, 2018 Refined products $ 65,916 $ 18,279 $ 887 $ 85,082 Merchandise 11 5,227 — 5,238 Crude oil 3,345 — — 3,345 Midstream services and other 413 40 2,386 2,839 Sales and other operating revenues $ 69,685 $ 23,546 $ 3,273 $ 96,504 (In millions) Refining & Marketing Retail Midstream Total Year Ended December 31, 2017 Refined products $ 50,193 $ 14,113 $ 889 $ 65,195 Merchandise 4 4,893 — 4,897 Crude oil 2,862 — — 2,862 Midstream services and other 323 23 1,433 1,779 Sales and other operating revenues $ 53,382 $ 19,029 $ 2,322 $ 74,733 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, 2019 , 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, 2019 include matching buy/sell receivables of $2.24 billion

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	12 Months Ended
	Dec. 31, 2019
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information	(In millions) 2019 2018 2017 Net cash provided by operating activities included: Interest paid (net of amounts capitalized) $ 1,174 $ 887 $ 525 Net income taxes paid to taxing authorities 491 424 904 Cash paid for amounts included in the measurement of lease liabilities Payments on operating leases (a) 764 — — Interest payments under finance lease obligations (a) 34 — — Net cash provided by financing activities included: Principal payments under finance lease obligations (a) 55 — — Non-cash investing and financing activities: Capital leases — 172 71 Right of use assets obtained in exchange for new operating lease obligations (a) 352 — — Right of use assets obtained in exchange for new finance lease obligations (a) 96 — — Contribution of assets (b) 266 — 337 Fair value of assets acquired (c) 525 — 45 Acquisition: Fair value of MPC shares issued — 19,766 — Fair value of converted equity awards — 203 — (a) Disclosure added in 2019 following the adoption of ASC 842. (b) 2019 includes the contribution of net assets to The Andersons Marathon Holdings LLC and Capline LLC. See Note 14 . 2017 includes MPLX’s contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. See Note 5 . (c) 2019 includes the recognition of The Andersons Marathon Holdings LLC and Capline LLC equity method investments. See Note 14 . 2017 represents emission allowance credits received as part of a litigation settlement agreement. (In millions) December 31, December 31, Cash and cash equivalents $ 1,527 $ 1,687 Restricted cash (a) 2 38 Cash, cash equivalents and restricted cash $ 1,529 $ 1,725 (a) The restricted cash balance is included within other current assets on the consolidated balance sheets. 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) 2019 2018 2017 Additions to property, plant and equipment per the consolidated statements of cash flows $ 5,374 $ 3,578 $ 2,732 Asset retirement expenditures 1 8 2 Increase (decrease) in capital accruals (306 ) 309 67 Total capital expenditures $ 5,069 $ 3,895 $ 2,801

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
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, 2017 $ (190 ) $ (48 ) $ 4 $ 3 $ (231 ) Other comprehensive income (loss) before reclassifications, net of tax of $23 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 — — — (5 ) (5 ) Tax effect (7 ) 2 (1 ) 2 (4 ) Other comprehensive income (loss) 58 25 (2 ) 6 87 Balance as of December 31, 2018 $ (132 ) $ (23 ) $ 2 $ 9 $ (144 ) (In millions) Pension Benefits Other Benefits Gain on Cash Flow Hedge Workers Compensation Total Balance as of December 31, 2018 $ (132 ) $ (23 ) $ 2 $ 9 $ (144 ) Other comprehensive income (loss) before reclassifications, net of tax of ($52) (71 ) (92 ) — 1 (162 ) Amounts reclassified from accumulated other comprehensive loss: Amortization – prior service credit (a) (45 ) — — — (45 ) – actuarial loss (a) 22 (1 ) — — 21 – settlement loss (a) 9 — — — 9 Other — — (1 ) (4 ) (5 ) Tax effect 5 — — 1 6 Other comprehensive loss (80 ) (93 ) (1 ) (2 ) (176 ) Balance as of December 31, 2019 $ (212 ) $ (116 ) $ 1 $ 7 $ (320 ) (a) These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 23 .

Pension and Other Postretiremen

Pension and Other Postretirement Benefits	12 Months Ended
	Dec. 31, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
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 qualified and nonqualified 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. Further, as of December 31, 2019, the qualified plans were merged with our existing qualified plans in which the actuarial assumptions were materially the same between the plans. 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 $3,031 million and $2,632 million as of December 31, 2019 and 2018 . The following summarizes our defined benefit pension plans that have accumulated benefit obligations in excess of plan assets. December 31, (In millions) 2019 2018 Projected benefit obligations $ 3,239 $ 2,779 Accumulated benefit obligations 3,031 2,632 Fair value of plan assets 2,531 2,089 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) 2019 2018 2019 2018 Change in benefit obligations: Benefit obligations at January 1 $ 2,779 $ 2,164 $ 884 $ 826 Service cost 234 159 31 30 Interest cost 108 83 37 30 Actuarial (gain) loss 401 (159 ) 125 (71 ) Benefits paid (283 ) (273 ) (45 ) (36 ) Plan amendments — (90 ) (1 ) 34 Acquisitions — 895 — 71 Benefit obligations at December 31 3,239 2,779 1,031 884 Change in plan assets: Fair value of plan assets at January 1 2,089 1,840 — — Actual return on plan assets 436 (115 ) — — Employer contributions 289 115 45 36 Benefits paid from plan assets (283 ) (273 ) (45 ) (36 ) Acquisitions — 522 — — Fair value of plan assets at December 31 2,531 2,089 — — Funded status of plans at December 31 $ (708 ) $ (690 ) $ (1,031 ) $ (884 ) Amounts recognized in the consolidated balance sheets: Current liabilities $ (49 ) $ (21 ) $ (47 ) $ (44 ) Noncurrent liabilities (659 ) (669 ) (984 ) (840 ) Accrued benefit cost $ (708 ) $ (690 ) $ (1,031 ) $ (884 ) Pretax amounts recognized in accumulated other comprehensive loss: (a) Net actuarial loss $ 579 $ 517 $ 135 $ 9 Prior service cost (credit) (250 ) (295 ) 33 35 (a) Amounts exclude those related to LOOP and Explorer, equity method investees with defined benefit pension and postretirement plans for which net losses of $17 million and less than $1 million were recorded in accumulated other comprehensive loss in 2019 , 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) 2019 2018 2017 2019 2018 2017 Components of net periodic benefit cost: Service cost $ 234 $ 159 $ 132 $ 31 $ 30 $ 25 Interest cost 108 83 75 37 30 30 Expected return on plan assets (127 ) (109 ) (100 ) — — — Amortization – prior service credit (45 ) (33 ) (39 ) — (3 ) (3 ) – actuarial (gain) loss 22 31 36 (1 ) (1 ) (2 ) – settlement loss 9 53 52 — — — Net periodic benefit cost (a) $ 201 $ 184 $ 156 $ 67 $ 56 $ 50 Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax): Actuarial (gain) loss $ 93 $ 64 $ (20 ) $ 125 $ (71 ) $ 61 Prior service cost (credit) — (90 ) — (1 ) 34 — Amortization of actuarial gain (loss) (31 ) (84 ) (88 ) 1 1 2 Amortization of prior service credit 45 33 39 — 3 3 Total recognized in other comprehensive loss $ 107 $ (77 ) $ (69 ) $ 125 $ (33 ) $ 66 Total recognized in net periodic benefit cost and other comprehensive loss $ 308 $ 107 $ 87 $ 192 $ 23 $ 116 (a) Net periodic benefit cost reflects a calculated market-related value of plan assets which recognizes changes in fair value over three years. For certain of our pension plans, lump sum payments to employees retiring in 2019 , 2018 and 2017 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 2019 , 2018 and 2017 . 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 2020 are $33 million and $45 million , respectively. The estimated amount that will be amortized from accumulated other comprehensive loss into net periodic benefit cost in 2020 is $3 million for net actuarial loss and less than $1 million for prior service cost 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 2019 , 2018 and 2017 . Pension Benefits Other Benefits 2019 2018 2017 2019 2018 2017 Weighted-average assumptions used to determine benefit obligation: Discount rate 3.03 % 4.21 % 3.55 % 3.00 % 4.26 % 3.70 % Rate of compensation increase 4.90 % 5.00 % 5.00 % 4.90 % 5.00 % 5.00 % Weighted-average assumptions used to determine net periodic benefit cost: Discount rate 4.05 % 3.88 % 3.85 % 4.30 % 3.72 % 4.25 % Expected long-term return on plan assets 6.00 % 6.15 % 6.50 % — % — % — % Rate of compensation increase 4.90 % 4.80 % 5.00 % 4.90 % 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, 2019 2018 2017 Health care cost trend rate assumed for the following year: Medical: Pre-65 6.20 % 6.80 % 6.75 % Prescription drugs 8.10 % 9.50 % 8.75 % 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 2027 2026 Prescription drugs 2027 2027 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 effect 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 $ 6 $ (5 ) Effect on other postretirement benefit obligations 52 (45 ) 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, 2019 , 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, 2019 and 2018 . 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 the 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 the 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, 2019 and 2018 . December 31, 2019 (In millions) Level 1 Level 2 Level 3 Total Cash and cash equivalents $ — $ 22 $ — $ 22 Equity: Common stocks 125 135 — 260 Mutual funds 188 — — 188 Pooled funds — 442 — 442 Fixed income: Corporate 160 815 — 975 Government 113 217 — 330 Pooled funds — 229 — 229 Private equity — — 30 30 Real estate — — 24 24 Other 58 (46 ) 19 31 Total investments, at fair value $ 644 $ 1,814 $ 73 $ 2,531 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 The following is a reconciliation of the beginning and ending balances recorded for plan assets classified as Level 3 in the fair value hierarchy: 2019 (In millions) Private Equity Real Estate Other Total Beginning balance $ 41 $ 29 $ 18 $ 88 Actual return on plan assets: Realized 5 2 — 7 Unrealized (3 ) (2 ) 1 (4 ) Purchases 1 1 — 2 Sales (14 ) (6 ) — (20 ) Ending balance $ 30 $ 24 $ 19 $ 73 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 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 2019 , we made contributions totaling $270 million to our funded pension plans. For 2020 , we have an immaterial amount of required funding, but we may also make voluntary contributions to our funded pension plans at our discretion. Cash contributions to be paid from our general assets for the unfunded pension and postretirement plans are estimated to be approximately $49 million and $47 million , respectively, in 2020 . 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 2020 $ 248 $ 47 2021 216 49 2022 218 50 2023 220 51 2024 233 52 2025 through 2029 1,187 283 Contributions to defined contribution plans – We also contribute to several defined contribution plans for eligible employees. Contributions to these plans totaled $217 million , $144 million and $116 million in 2019 , 2018 and 2017 , 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 2019 , 2018 and 2017 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 2019 and 2018 is for the plan’s year ended December 31, 2018 and December 31, 2017 , 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 2019 , 2018 and 2017 contributions. Our portion of the contributions does not make up more than five percent of total contributions to the plan. Pension FIP/RP Status MPC Contributions In millions ) Surcharge Expiration Date of Pension Fund EIN 2019 2018 2019 2018 2017 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 2020 . A total of 263 employees participated in the plan as of December 31, 2019 . 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 , $6 million and $7 million for 2019 , 2018 and 2017 , respectively.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Share-based Payment Arrangement [Text Block]	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. 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 2019 were granted 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 and do not receive dividend equivalents. 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) 2019 2018 2017 Stock-based compensation expense $ 161 $ 133 $ 51 Tax benefit recognized on stock-based compensation expense 37 32 19 Cash received by MPC upon exercise of stock option awards 10 24 46 Tax (expense)/benefit received for tax deductions for stock awards exercised (3 ) 14 25 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: 2019 2018 2017 Weighted average exercise price per share $ 61.92 $ 67.71 $ 50.57 Expected life in years 6.0 6.2 6.3 Expected volatility 32 % 34 % 35 % Expected dividend yield 3.4 % 3.0 % 3.0 % Risk-free interest rate 2.4 % 2.7 % 2.1 % Weighted average grant date fair value of stock option awards granted $ 13.65 $ 17.21 $ 13.42 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 2019 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 2019 : Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Terms (in years) Aggregate Intrinsic Value (in millions) Outstanding at December 31, 2018 8,724,595 $ 37.07 Granted 1,952,324 61.92 Exercised (529,706 ) 19.12 Forfeited or expired (128,846 ) 61.29 Outstanding at December 31, 2019 10,018,367 42.55 Vested and expected to vest at December 31, 2019 9,987,326 26.84 5.2 $ 187 Exercisable at December 31, 2019 7,404,952 35.85 4.0 183 The intrinsic value of options exercised by MPC employees during 2019 , 2018 and 2017 was $23 million , $44 million and $75 million , respectively. As of December 31, 2019 , unrecognized compensation cost related to stock option awards was $14 million , which is expected to be recognized over a weighted average period of 1.4 years. Restricted Stock and Restricted Stock Unit Awards The following is a summary of restricted stock award activity of our common stock in 2019 : Restricted Stock Restricted Stock Units Number of Shares Weighted Average Grant Date Fair Value Number of Units Weighted Unvested at December 31, 2018 989,019 $ 57.19 3,120,116 $ 82.40 Granted 1,059,837 61.14 36,391 58.30 Vested (595,440 ) 52.16 (1,527,145 ) 81.84 Forfeited (103,618 ) 61.20 (147,616 ) 82.37 Unvested at December 31, 2019 1,349,798 62.20 1,481,746 82.39 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 2019 $ 32 $ 61.14 $ 120 $ 58.30 2018 49 71.19 39 72.43 2017 28 50.25 5 53.19 As of December 31, 2019 , unrecognized compensation cost related to restricted stock awards was $56 million , which is expected to be recognized over a weighted average period of 1.46 years. Unrecognized compensation cost related to restricted stock unit awards was $28 million , which is expected to be recognized over a weighted average period of 0.66 years. Performance Unit Awards The following table presents a summary of the 2019 activity for performance unit awards to be settled in shares: Number of Units Weighted Average Grant Date Fair Value Unvested at December 31, 2018 8,607,250 $ 0.79 Granted 6,256,250 0.72 Vested (3,494,000 ) 0.62 Forfeited (170,000 ) 0.81 Unvested at December 31, 2019 11,199,500 0.80 The number of shares that would be issued upon target vesting, using the closing price of our common stock on December 31, 2019 would be 206,216 shares. As of December 31, 2019 , unrecognized compensation cost related to equity-classified performance unit awards was $2 million , which is expected to be recognized over a weighted average period of 0.82 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: 2019 2018 2017 Risk-free interest rate 2.5 % 2.3 % 1.5 % Look-back period (in years) 2.8 2.8 2.8 Expected volatility 29.7 % 34.0 % 36.1 % Grant date fair value of performance units granted $ 0.72 $ 0.83 $ 0.92 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 of MPLX and ANDX units are not material to our consolidated financial statements for 2019.

Leases

Leases	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Leases of Lessee Disclosure	For further information regarding the adoption of ASC 842, including the method of adoption and practical expedients elected, see Note 3 . Lessee We lease a wide variety of facilities and equipment including land and building space, office and field equipment, storage facilities and transportation equipment. Our remaining lease terms range from less than one year to 59 years . Most long-term leases include renewal options ranging from less than one year to 50 years and, in certain leases, also include purchase options. The lease term included in the measurement of right of use assets and lease liabilities includes options to extend or terminate our leases that we are reasonably certain to exercise. Options were included in the lease term primarily for retail store sites where we constructed property, plant and equipment on leased land that is expected to exist beyond the initial lease term. Under ASC 842, the components of lease cost were as follows: (In millions) 2019 Finance lease cost: Amortization of right of use assets $ 64 Interest on lease liabilities 43 Operating lease cost 793 Variable lease cost 91 Short-term lease cost 746 Total lease cost $ 1,737 Supplemental balance sheet data related to leases were as follows: (In millions) December 31, 2019 Operating leases Assets Right of use assets $ 2,459 Liabilities Operating lease liabilities $ 604 Long-term operating lease liabilities 1,875 Total operating lease liabilities $ 2,479 Weighted average remaining lease term (in years) 6.2 Weighted average discount rate 4.02 % Finance leases Assets Property, plant and equipment, gross $ 807 Accumulated depreciation 227 Property, plant and equipment, net $ 580 Liabilities Debt due within one year $ 62 Long-term debt 636 Total finance lease liabilities $ 698 Weighted average remaining lease term (in years) 11.9 Weighted average discount rate 6.50 % As of December 31, 2019 , maturities of lease liabilities for operating lease obligations and finance lease obligations having initial or remaining non-cancellable lease terms in excess of one year are as follows: (In millions) Operating Finance 2020 $ 698 $ 96 2021 590 87 2022 402 95 2023 287 98 2024 222 84 2025 and thereafter 634 527 Gross lease payments 2,833 987 Less: imputed interest 354 289 Total lease liabilities $ 2,479 $ 698 Presented in accordance with ASC 840, future minimum commitments as of December 31, 2018 for operating lease obligations and capital lease obligations having initial or remaining non-cancellable lease terms in excess of one year were as follows: (In millions) Operating Capital 2019 $ 709 $ 70 2020 619 71 2021 553 66 2022 389 75 2023 295 82 2024 and thereafter 858 586 Total minimum lease payments $ 3,423 950 Less: imputed interest costs 301 Present value of net minimum lease payments $ 649
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 operating lease arrangements in accordance with GAAP. MPLX’s primary natural gas 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 natural gas 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 terms of these natural gas processing agreements expire during 2023 and 2033 and will continue thereafter on a year-to-year basis until terminated by either party. MPLX did not elect to use the practical expedient to combine lease and non-lease components for lessor arrangements. The tables below represent the portion of the contract allocated to the lease component based on relative standalone selling price. Lessor agreements are currently deemed operating, as MPLX elected the practical expedient to carry forward historical classification conclusions. If and when a modification of an existing agreement occurs and the agreement is required to assessed under ASC 842, MPLX assesses the amended agreement and makes a determination as to whether a reclassification of the lease is required. Under ASC 840, our revenue from implicit lease arrangements, excluding executory costs, totaled approximately $254 million , $221 million and $218 million in 2019 , 2018 and 2017 , respectively. The following is a schedule of minimum future rentals on the non‑cancellable operating leases as of December 31, 2019 : (In millions) 2020 $ 186 2021 179 2022 177 2023 170 2024 167 2025 and thereafter 1,072 Total minimum future rentals $ 1,951 The following schedule summarizes our investment in assets held for operating lease by major classes as of December 31, 2019 : (In millions) Natural gas gathering and NGL transportation pipelines and facilities $ 1,121 Natural gas processing facilities 686 Terminals and related assets 83 Land, building, office equipment and other 45 Property, plant and equipment 1,935 Less accumulated depreciation 327 Total property, plant and equipment, net $ 1,608

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
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, 2019 and 2018 , accrued liabilities for remediation totaled $433 million and $455 million , respectively. It is not presently possible to estimate the ultimate amount of all remediation costs that might be incurred or the penalties if any that may be imposed. Receivables for recoverable costs from certain states, under programs to assist companies in clean-up efforts related to underground storage tanks at presently or formerly owned or operated retail marketing sites, were $29 million and $35 million at December 31, 2019 and 2018 , 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. Asset Retirement Obligations Our short-term asset retirement obligations were $24 million and $30 million at December 31, 2019 and 2018 , respectively, which are included in other current liabilities in our consolidated balance sheets. Our long-term asset retirement obligations were $206 million and $222 million at December 31, 2019 and 2018 , respectively, which are included in deferred credits and other liabilities in our consolidated balance sheets. 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. 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, 2019 . In connection with our 25 percent interest in Gray Oak Pipeline, LLC (“Gray Oak Pipeline”), we have entered into an Equity Contribution Agreement obligating us to make certain equity contributions to Gray Oak Pipeline to support its obligations under a construction loan facility. Gray Oak oil pipeline is a crude oil transportation system from West Texas and the Eagle Ford formation to destinations in the Ingleside, Corpus Christi and Sweeney, Texas markets. Gray Oak Pipeline entered into the construction loan facility with a syndicate of banks to finance a portion of the construction costs of the pipeline project. The Equity Contribution Agreement requires us to contribute our pro rata share of any amounts necessary to allow Gray Oak Pipeline to cure any payment defaults under the construction loan facility or to repay all amounts outstanding under the facility, including principal, accrued interest, fees and expenses, in certain circumstances, including the failure of Gray Oak Pipeline to repay or refinance the construction loan facility prior to its scheduled maturity date of June 3, 2022. Gray Oak may borrow up to $1.43 billion under the construction loan facility (after giving effect to the exercise of all options to increase its borrowing capacity). As of December 31, 2019 , our maximum potential undiscounted payments under the Equity Contribution Agreement for the debt principal totaled $292 million . In connection with MPLX’s approximate 9 percent indirect interest in a joint venture that owns and operates the Dakota Access Pipeline and Energy Transfer Crude Oil Pipeline projects, collectively referred to as the Bakken Pipeline system, MPLX entered into a Contingent Equity Contribution Agreement. MPLX, along with the other joint venture owners in the Bakken Pipeline system, have agreed to make equity contributions to the joint venture upon certain events occurring to allow the entities that own and operate the Bakken Pipeline system to satisfy their senior note payment obligations. The senior notes were issued to repay amounts owed by the pipeline companies to fund the cost of construction of the Bakken Pipeline system. As of December 31, 2019 , our maximum potential undiscounted payments under the Contingent Equity Contribution Agreement was approximately $230 million . 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, 2019 , our maximum potential undiscounted payments under this agreement for debt principal totaled $130 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. As of December 31, 2019 , our maximum potential undiscounted payments under this arrangement was $122 million . Marathon Oil indemnifications – The separation and distribution agreement and other agreements with Marathon Oil to effect our spinoff provide for cross-indemnities between Marathon Oil and us. In general, Marathon Oil is required to indemnify us for any liabilities relating to Marathon Oil’s historical oil and gas exploration and production operations, oil sands mining operations and integrated gas operations, and we are required to indemnify Marathon Oil for any liabilities relating to Marathon Oil’s historical refining, marketing and transportation operations. The terms of these indemnifications are indefinite and the amounts are not capped. Other guarantees – We have entered into other guarantees with maximum potential undiscounted payments totaling $121 million as of December 31, 2019 , which consist primarily of a commitment to contribute cash to an equity method investee for certain catastrophic events in lieu of procuring insurance coverage, a commitment to fund a share of the bonds issued by a government entity for construction of public utilities in the event that other industrial users of the facility default on their utility payments and leases of assets containing general lease indemnities and guaranteed residual values. General guarantees associated with dispositions – Over the years, we have sold various assets in the normal course of our business. Certain of the related agreements contain performance and general guarantees, including guarantees regarding inaccuracies in representations, warranties, covenants and agreements, and environmental and general indemnifications that require us to perform upon the occurrence of a triggering event or condition. These guarantees and indemnifications are part of the normal course of selling assets. We are typically not able to calculate the maximum potential amount of future payments that could be made under such contractual provisions because of the variability inherent in the guarantees and indemnities. Most often, the nature of the guarantees and indemnities is such that there is no appropriate method for quantifying the exposure because the underlying triggering event has little or no past experience upon which a reasonable prediction of the outcome can be based. Contractual Commitments and Contingencies At December 31, 2019 and 2018 , our contractual commitments to acquire property, plant and equipment and advance funds to equity method investees totaled $1.6 billion and $1.8 billion , respectively. 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, 2019
Quarterly Financial Data [Abstract]
Selected Quarterly Financial Data	2019 Quarter Ended (In millions, except per share data) March 31 June 30 September 30 December 31 Sales and other operating revenues (a) $ 28,267 $ 33,547 $ 31,043 $ 31,092 Income from operations 669 2,042 2,024 841 Net income 259 1,367 1,367 262 Net income (loss) attributable to MPC (7 ) 1,106 1,095 443 Net income (loss) attributable to MPC per share (b) : Basic $ (0.01 ) $ 1.67 $ 1.67 $ 0.68 Diluted (0.01 ) 1.66 1.66 0.68 2018 Quarter Ended (In millions, except per share data) March 31 June 30 September 30 December 31 Sales and other operating revenues (a) $ 18,866 $ 22,317 $ 22,988 $ 32,333 Income from operations 440 1,711 1,403 2,017 Net income 235 1,235 941 1,195 Net income attributable to MPC 37 1,055 737 951 Net income attributable to MPC per share (b) : Basic $ 0.08 $ 2.30 $ 1.63 $ 1.38 Diluted 0.08 2.27 1.62 1.35 (a) Includes sales to related parties. (b) 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, 2019
Accounting Policies [Abstract]
Principles applied in consolidation	Principles Applied in Consolidation These consolidated financial statements include the accounts of our majority-owned, controlled subsidiaries and MPLX. As of December 31, 2019 , we owned the general partner and 63 percent of the outstanding MPLX common units. Due to our ownership of the general partner interest, we have determined that we control MPLX and therefore we consolidate MPLX and record a noncontrolling interest for the interest owned by the public. Changes in ownership interest in consolidated subsidiaries that do not result in a change in control are recorded as equity transactions. 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 any 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”), as of January 1, 2018, 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. Speedway offers a loyalty rewards program to its customers. We defer a minor portion of revenue on sales to the loyalty program participants until the participants redeem their rewards. The related contract liability, as defined in 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 20 for disclosure of our revenue disaggregated by segment and product line and to Note 10 for 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.
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 two years 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 using an income and/or market approach which is compared to the carrying value of the reporting unit. The fair value under the income approach 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 would 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. 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 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 the sale of allowances or credits are reported in investing activities - all other, net on the cash flow statement.

Master Limited Partnership (Tab

Master Limited Partnership (Tables)	12 Months Ended
	Dec. 31, 2019
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 to reflect these changes in ownership. Changes in MPC’s additional paid-in capital resulting from changes in its ownership interest in MPLX and ANDX were as follows: (In millions) 2019 2018 2017 Increase due to the issuance of MPLX common units and general partner units to MPC $ — $ 1,114 $ 114 Increase due to GP/IDR Exchange — 1,808 — Increase (decrease) due to the issuance of MPLX & ANDX common units (51 ) 6 25 Increase (decrease) in MPC's additional paid-in capital (51 ) 2,928 139 Tax impact (633 ) (571 ) (29 ) Increase (decrease) in MPC's additional paid-in capital, net of tax $ (684 ) $ 2,357 $ 110

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2019
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]	The fair value estimates of assets acquired and liabilities assumed as of the acquisition date are noted in the table below. (In millions) As originally reported Adjustments As adjusted Cash and cash equivalents $ 382 $ — $ 382 Receivables 2,744 (5 ) 2,739 Inventories 5,204 37 5,241 Other current assets 378 (6 ) 372 Equity method investments 865 (113 ) 752 Property, plant and equipment, net 16,545 (1,021 ) 15,524 Other noncurrent assets (a) 3,086 (11 ) 3,075 Total assets acquired 29,204 (1,119 ) 28,085 (In millions) As originally reported Adjustments As adjusted Accounts payable 4,003 (41 ) 3,962 Payroll and benefits payable 348 9 357 Accrued taxes 590 (110 ) 480 Debt due within one year 34 — 34 Other current liabilities 392 27 419 Long-term debt 8,875 1 8,876 Deferred income taxes 1,609 (60 ) 1,549 Defined benefit postretirement plan obligations 432 — 432 Deferred credit and other liabilities 714 33 747 Noncontrolling interests 5,059 3 5,062 Total liabilities and noncontrolling interest assumed 22,056 (138 ) 21,918 Net assets acquired excluding goodwill 7,148 (981 ) 6,167 Goodwill 16,314 981 17,295 Net assets acquired $ 23,462 $ — $ 23,462 (a) Includes intangible assets.
Business Acquisition, Pro Forma Information	he 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) $ 131,921 $ 118,179 Net income attributable to MPC 4,218 4,712 (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, 2019
Equity Method Investments and Joint Ventures [Abstract]
Summarized Balance Sheet Information of VIEs	The following table presents 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 MPLX ANDX Assets Cash and cash equivalents $ 15 $ 68 $ 10 Receivables, less allowance for doubtful accounts 615 425 199 Inventories 110 77 22 Other current assets 110 45 57 Equity method investments 5,275 4,174 602 Property, plant and equipment, net 22,174 14,639 6,845 Goodwill 9,536 2,586 1,051 Right of use assets 365 — — Other noncurrent assets 1,323 458 1,242 Liabilities Accounts payable $ 744 $ 776 $ 215 Payroll and benefits payable 5 2 10 Accrued taxes 80 48 23 Debt due within one year 9 1 504 Operating lease liabilities 66 — — Other current liabilities 259 177 77 Long-term debt 19,704 13,392 4,469 Deferred income taxes 12 13 1 Long-term operating lease liabilities 302 — — Deferred credits and other liabilities 409 276 68

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2019
Related Party Transactions [Abstract]
Schedule of Related Party Transactions [Table Text Block]	Transactions with related parties were as follows: (In millions) 2019 2018 2017 Sales to related parties $ 768 $ 754 $ 629 Purchases from related parties 763 610 570

Earnings per Share (Tables)

Earnings per Share (Tables)	12 Months Ended
	Dec. 31, 2019
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) 2019 2018 2017 Basic earnings per share: Allocation of earnings: Net income attributable to MPC $ 2,637 $ 2,780 $ 3,432 Income allocated to participating securities 1 1 2 Income available to common stockholders – basic $ 2,636 $ 2,779 $ 3,430 Weighted average common shares outstanding 659 518 507 Basic earnings per share $ 4.00 $ 5.36 $ 6.76 Diluted earnings per share: Allocation of earnings: Net income attributable to MPC $ 2,637 $ 2,780 $ 3,432 Income allocated to participating securities 1 1 2 Income available to common stockholders – diluted $ 2,636 $ 2,779 $ 3,430 Weighted average common shares outstanding 659 518 507 Effect of dilutive securities 5 8 5 Weighted average common shares, including dilutive effect 664 526 512 Diluted earnings per share $ 3.97 $ 5.28 $ 6.70
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) 2019 2018 2017 Shares issuable under stock-based compensation plans 3 — 1

Equity (Tables)

Equity (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Share Repurchases	Total share repurchases were as follows for the respective periods: (In millions, except per share data) 2019 2018 2017 Number of shares repurchased 34 47 44 Cash paid for shares repurchased $ 1,950 $ 3,287 $ 2,372 Average cost per share $ 58.87 $ 69.46 $ 53.85

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Income From Operations Attributable To Operating Segments	Segment income from operations represents income from operations attributable to the reportable segments. Corporate administrative expenses, except for those attributable to MPLX, and costs related to certain non-operating assets are not allocated to the Refining & Marketing and Retail segments. In addition, certain items that affect comparability (as determined by the chief operating decision maker) are not allocated to the reportable segments. (In millions) Refining & Marketing Retail Midstream Total Year Ended December 31, 2019 Revenues: Third party (a) $ 87,056 $ 33,059 $ 3,834 $ 123,949 Intersegment 19,686 8 4,926 24,620 Segment revenues $ 106,742 $ 33,067 $ 8,760 $ 148,569 Segment income from operations $ 2,367 $ 1,582 $ 3,594 $ 7,543 Supplemental Data Depreciation and amortization (b) 1,665 528 1,267 3,460 Capital expenditures and investments (c) 1,999 607 3,290 5,896 (In millions) Refining & Marketing Retail Midstream Total Year Ended December 31, 2018 Revenues: Third party (a) $ 69,685 $ 23,546 $ 3,273 $ 96,504 Intersegment 12,914 6 3,387 16,307 Segment revenues $ 82,599 $ 23,552 $ 6,660 $ 112,811 Segment income from operations $ 2,481 $ 1,028 $ 2,752 $ 6,261 Supplemental Data 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 (a) $ 53,382 $ 19,029 $ 2,322 $ 74,733 Intersegment (d) 11,309 4 1,443 12,756 Segment revenues $ 64,691 $ 19,033 $ 3,765 $ 87,489 Segment income from operations $ 2,321 $ 729 $ 1,339 $ 4,389 Supplemental Data Depreciation and amortization (b) 1,082 275 699 2,056 Capital expenditures and investments (c) 832 381 1,755 2,968 (a) Includes related party sales. See Note 7 for additional information. (b) Differences between segment totals and MPC totals represent amounts related to unallocated items and are included in items not allocated to segment in the reconciliation below. (c) Includes changes in capital expenditure accruals and investments in affiliates. (d) Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties.
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) 2019 2018 2017 Segment income from operations $ 7,543 $ 6,261 $ 4,389 Items not allocated to segments: Corporate and other unallocated items (a) (805 ) (502 ) (365 ) Equity method investment restructuring gains (b) 259 — — Transaction-related costs (c) (160 ) (197 ) — Litigation (22 ) — (29 ) Impairments (d) (1,239 ) 9 23 Income from operations 5,576 5,571 4,018 Net interest and other financial costs 1,247 1,003 674 Income before income taxes $ 4,329 $ 4,568 $ 3,344 (a) Corporate and other unallocated items consists primarily of MPC’s corporate administrative expenses and costs related to certain non-operating assets, except for corporate overhead expenses attributable to MPLX, which are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Retail segments. (b) Includes gains related to The Andersons Marathon Holdings LLC and Capline Pipeline Company LLC. See Note 14 . (c) 2019 includes costs incurred in connection with the proposed Speedway separation, Midstream strategic review and other related efforts. Both 2019 and 2018 include employee severance, retention and other costs related to the acquisition of Andeavor. Effective October 1, 2019, we have discontinued reporting Andeavor transaction-related costs as one year has passed since the Andeavor acquisition. The post October 1, 2019 transaction costs are immaterial and reported in corporate and other unallocated items. (d) 2019 reflects impairments of goodwill and equity method investments. See Notes 16 and 14 . 2018 and 2017 includes MPC’s share of gains from the sale of assets remaining from the Sandpiper pipeline project, which was cancelled and impaired in 2016.
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) 2019 2018 2017 Segment capital expenditures and investments $ 5,896 $ 4,147 $ 2,968 Less investments in equity method investees 1,064 409 305 Plus items not allocated to segments: Corporate 100 77 83 Capitalized interest 137 80 55 Total capital expenditures (a) $ 5,069 $ 3,895 $ 2,801 (a) Includes changes in capital expenditure accruals. See Note 21 for a reconciliation of total capital expenditures to additions to property, plant and equipment as reported in the consolidated statements of cash flows.

Net Interest and Other Financ_2

Net Interest and Other Financial Costs (Tables)	12 Months Ended
	Dec. 31, 2019
Other Income and Expenses [Abstract]
Net Interest And Other Financial Income (Costs)	Net interest and other financial costs was: (In millions) 2019 2018 2017 Interest income $ (40 ) $ (87 ) $ (27 ) Interest expense 1,396 1,026 688 Interest capitalized (158 ) (80 ) (63 ) Pension and other postretirement non-service costs (a) 3 53 49 Loss on extinguishment of debt — 64 — Other financial costs 46 27 27 Net interest and other financial costs $ 1,247 $ 1,003 $ 674 (a) See Note 23

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Components Of Income Tax Provisions (Benefits)	Income tax provision (benefit) was: (In millions) 2019 2018 2017 Current: Federal $ (3 ) $ 715 $ 681 State and local 53 178 98 Foreign 1 22 (6 ) Total current 51 915 773 Deferred: Federal 898 2 (1,270 ) State and local 116 61 33 Foreign 9 (16 ) 4 Total deferred 1,023 47 (1,233 ) Income tax provision (benefit) $ 1,074 $ 962 $ (460 )
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: 2019 2018 2017 Statutory rate applied to income before income taxes 21 % 21 % 35 % State and local income taxes, net of federal income tax effects 3 4 2 Goodwill impairment 3 — — Noncontrolling interests (3 ) (4 ) (4 ) TCJA legislation — — (45 ) Other 1 — (2 ) Provision for income taxes 25 % 21 % (14 )%
Components Of Deferred Tax Assets And Liabilities	Deferred tax assets and liabilities resulted from the following: December 31, (In millions) 2019 2018 Deferred tax assets: Employee benefits $ 693 $ 660 Environmental remediation 99 111 Debt financing 17 39 Net operating loss carryforwards 18 17 Foreign currency 15 28 Tax credit carryforwards 14 21 Other 57 88 Total deferred tax assets 913 964 Deferred tax liabilities: Property, plant and equipment 3,444 2,830 Inventories 652 678 Investments in subsidiaries and affiliates 3,114 2,130 Intangibles 56 97 Other 19 64 Total deferred tax liabilities 7,285 5,799 Net deferred tax liabilities $ 6,372 $ 4,835
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) 2019 2018 Assets: Other noncurrent assets $ 20 $ 29 Liabilities: Deferred income taxes 6,392 4,864 Net deferred tax liabilities $ 6,372 $ 4,835
Summary Of Income Tax Returns Subject To Examination	As of December 31, 2019 , our income tax returns remain subject to examination in the following major tax jurisdictions for the tax years indicated: United States Federal 2011 - 2018 States 2006 - 2018
Summary Of Activity In Unrecognized Tax Benefits	The following table summarizes the activity in unrecognized tax benefits: (In millions) 2019 2018 2017 January 1 balance $ 211 $ 19 $ 7 Additions for tax positions of prior years 2 — 13 Reductions for tax positions of prior years (2 ) (5 ) — Settlements (19 ) — (1 ) Statute of limitations (160 ) (12 ) — Acquired from Andeavor — 209 — December 31 balance $ 32 $ 211 $ 19

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2019
Inventory Disclosure [Abstract]
Summary Of Inventories	December 31, (In millions) 2019 2018 Crude oil $ 3,472 $ 3,655 Refined products 5,548 5,234 Materials and supplies 996 720 Merchandise 227 228 Total $ 10,243 $ 9,837

Equity Method Investments (Tabl

Equity Method Investments (Tables)	12 Months Ended
	Dec. 31, 2019
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) 2019 2019 2018 Refining & Marketing The Andersons Marathon Holdings LLC 50% $ 177 $ — Watson Cogeneration Company 51% 26 84 Other (a) — 121 Refining & Marketing Total $ 203 $ 205 Retail PFJ Southeast LLC 29% $ 330 $ 341 Retail Total $ 330 $ 341 Midstream MPLX Andeavor Logistics Rio Pipeline LLC 67% $ 202 $ 181 Centrahoma Processing LLC 40% 153 160 Explorer Pipeline Company 25% 83 90 Illinois Extension Pipeline Company, L.L.C 35% 265 275 LOOP LLC 41% 238 226 MarEn Bakken Company LLC 25% 481 498 MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C. 67% 302 236 MarkWest Utica EMG, L.L.C. 56% 1,984 2,039 Minnesota Pipe Line Company, LLC 17% 190 197 Rendezvous Gas Services, L.L.C. 78% 170 248 Sherwood Midstream Holdings LLC 53% 157 157 Sherwood Midstream LLC 50% 537 366 Whistler Pipeline LLC 38% 134 — Wink to Webster Pipeline LLC 15% 126 — Other 253 228 MPLX Total $ 5,275 $ 4,901 MPC-Retained Capline Pipeline Company LLC 33% $ 374 $ — Crowley Coastal Partners, LLC 50% 188 190 Gray Oak Pipeline, LLC 25% 298 73 LOOP LLC 10% 59 56 Other 171 132 MPC-Retained Total $ 1,090 $ 451 Midstream Total $ 6,365 $ 5,352 Total $ 6,898 $ 5,898 (a) 2018 represents our investment in three ethanol entities jointly owned with The Andersons, Inc. In 2019, these entities were contributed into a new legal entity, The Andersons Marathon 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) 2019 2018 2017 Income statement data: Revenues and other income $ 7,718 $ 7,726 $ 6,235 Income from operations 1,472 1,375 1,075 Net income 1,284 1,242 922 Balance sheet data – December 31: Current assets $ 1,333 $ 1,443 Noncurrent assets 17,216 12,408 Current liabilities 1,006 1,857 Noncurrent liabilities 2,772 1,788

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Summary Of Property, Plant And Equipment	(In millions) Estimated Useful Lives December 31, 2019 2018 Refining & Marketing 4 - 30 years $ 29,037 $ 27,590 Retail 4 - 25 years 7,104 6,637 Midstream 2 - 51 years 27,193 25,692 Corporate and Other 4 - 40 years 1,289 1,294 Total 64,623 61,213 Less accumulated depreciation 19,008 16,155 Property, plant and equipment, net $ 45,615 $ 45,058

Goodwill and Intangibles (Table

Goodwill and Intangibles (Tables)	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in Carrying Amount of Goodwill	The changes in the carrying amount of goodwill for 2018 and 2019 were as follows: (In millions) Refining & Marketing Retail Midstream Total Balance at January 1, 2018 $ 519 $ 791 $ 2,276 $ 3,586 Acquisitions 4,717 4,050 7,831 16,598 Dropdowns to MPLX (216 ) — 216 — Balance at December 31, 2018 $ 5,020 $ 4,841 $ 10,323 $ 20,184 Acquisitions 38 56 — 94 Purchase price allocation adjustments 514 54 408 976 Impairments — — (1,197 ) (1,197 ) Dispositions — — (17 ) (17 ) Balance at December 31, 2019 $ 5,572 $ 4,951 $ 9,517 $ 20,040
Schedule of Acquired Finite-Lived Intangible Assets by Major Class	Our definite lived intangible assets as of December 31, 2019 and 2018 are as shown below. December 31, 2019 December 31, 2018 (In millions) Gross Accumulated Amortization Net Gross Accumulated Amortization Net Customer contracts and relationships $ 3,273 $ 610 $ 2,663 $ 3,184 $ 261 $ 2,923 Brand rights and tradenames 155 55 100 208 33 175 Royalty agreements 133 78 55 129 70 59 Other 147 37 110 190 33 157 Total $ 3,708 $ 780 $ 2,928 $ 3,711 $ 397 $ 3,314
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	Estimated future amortization expense related to the intangible assets at December 31, 2019 is as follows: (In millions) 2020 $ 387 2021 380 2022 379 2023 363 2024 305

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2019
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, 2019 and 2018 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, 2019 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 Assets: Commodity contracts $ 57 $ 6 $ — $ (55 ) $ 8 $ 73 Liabilities: Commodity contracts $ 95 $ 11 $ — $ (106 ) $ — $ — Embedded derivatives in commodity contracts — — 60 — 60 — 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 Assets: Commodity contracts $ 370 $ 31 $ — $ (323 ) $ 78 $ 2 Liabilities: Commodity contracts $ 255 $ 37 $ — $ (284 ) $ 8 $ — Embedded derivatives in commodity contracts — — 61 — 61 — (a) Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of December 31, 2019 , $51 million was netted with mark-to-market liabilities. 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 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) 2019 2018 Beginning balance $ 61 $ 66 Unrealized and realized losses included in net income 5 3 Settlements of derivative instruments (6 ) (8 ) Ending balance $ 60 $ 61 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: $ 5 $ 8

Derivatives (Tables)

Derivatives (Tables)	12 Months Ended
	Dec. 31, 2019
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, 2019 and 2018 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, 2019 Balance Sheet Location Asset Liability Commodity derivatives Other current assets $ 63 $ 106 Other current liabilities (a) — 5 Deferred credits and other liabilities (a) — 55 (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 (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, 2019 . Percentage of contracts that expire next quarter Position (Units in thousands of barrels) Long Short Exchange-traded (a) Crude oil 85.7% 26,287 27,237 Refined products 94.7% 15,298 12,519 Blending products 99.5% 1,976 3,770 (a) Included in exchange-traded are spread contracts in thousands of barrels: Crude oil - 5,130 long and 330 short; Refined products - 950 long and 450 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 2019 2018 2017 Sales and other operating revenues $ (19 ) $ 13 $ 5 Cost of revenues (77 ) (59 ) (26 ) Total $ (96 ) $ (46 ) $ (21 )

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2019
Debt Instrument [Line Items]
Outstanding Borrowings	Our outstanding borrowings at December 31, 2019 and 2018 consisted of the following: (In millions) December 31, December 31, Marathon Petroleum Corporation: Senior notes $ 8,474 $ 8,474 Notes payable 10 11 Finance lease obligations 679 629 MPLX LP: Term loan facility 1,000 — Senior notes 19,100 13,850 Finance lease obligations 19 6 ANDX LP: (a) Revolving and dropdown credit facilities — 1,245 Senior notes — 3,750 Finance lease obligations — 15 Total debt $ 29,282 $ 27,980 Unamortized debt issuance costs (134 ) (128 ) Unamortized discount (310 ) (328 ) Amounts due within one year (711 ) (544 ) Total long-term debt due after one year $ 28,127 $ 26,980 (a) On July 30, 2019, MPLX acquired ANDX and assumed its debt obligations. See Note 4 and the discussion below for additional information.
Schedule Of Debt Payments	Principal maturities of long-term debt, excluding finance lease obligations, as of December 31, 2019 for the next five years are as follows: (In millions) 2020 $ 650 2021 3,008 2022 2,275 2023 2,350 2024 2,652
Schedule of Line of Credit Facilities [Table Text Block]	(Dollars in millions) Total Capacity Outstanding Borrowings Outstanding Letters of Credit Available Capacity Weighted Average Interest Rate Expiration MPC 364-day bank revolving credit facility $ 1,000 $ — $ — $ 1,000 — September 2020 MPC bank revolving credit facility 5,000 — 1 4,999 — October 2023 MPC trade receivables securitization facility 750 — — 750 — July 2021 MPLX bank revolving credit facility 3,500 — — 3,500 — July 2024
Marathon Petroleum Corporation | Senior Notes
Debt Instrument [Line Items]
Outstanding Borrowings	December 31, (In millions) 2019 2018 Marathon Petroleum Corporation: 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 337 337 Senior notes, 4.750% due December 2023 614 614 Senior notes, 5.125% due April 2024 241 241 Senior notes, 3.625%, due September 2024 750 750 Senior notes, 5.125% due December 2026 719 719 Senior notes, 3.800% due April 2028 496 496 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 498 498 Andeavor senior notes, 3.800% - 5.375% due 2022 - 2048 469 469 Senior notes, 5.000%, due September 2054 400 400 Total 8,474 8,474
MPLX | Senior Notes
Debt Instrument [Line Items]
Outstanding Borrowings	Average December 31, (In millions) Rate 2019 2018 MPLX LP: Floating rate notes due September 2021 2.948 % 1,000 — Floating rate notes due September 2022 3.148 % 1,000 — Senior notes, 6.250% due October 2022 266 — Senior notes, 3.500% due December 2022 486 — Senior notes, 3.375% due March 2023 500 500 Senior notes, 4.500% due July 2023 989 989 Senior notes, 6.375% due May 2024 381 — Senior notes, 4.875% due December 2024 1,149 1,149 Senior notes, 5.250% due January 2025 708 — Senior notes, 4.000% due February 2025 500 500 Senior notes, 4.875% due June 2025 1,189 1,189 MarkWest senior notes, 4.500% - 5.500% due 2023 - 2025 23 23 Senior notes, 4.125% due March 2027 1,250 1,250 Senior notes, 4.250% due December 2027 732 — Senior notes, 4.000% due March 2028 1,250 1,250 Senior notes, 4.800% due February 2029 750 750 Senior notes, 4.500% due April 2038 1,750 1,750 Senior notes, 5.200% due March 2047 1,000 1,000 Senior notes, 5.200% due December 2047 487 — ANDX senior notes, 3.500% - 6.375% due 2019 - 2047 190 — Senior notes, 4.700% due April 2048 1,500 1,500 Senior notes, 5.500% due February 2049 1,500 1,500 Senior notes, 4.900% due April 2058 500 500 Total 19,100 13,850

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table presents our revenues disaggregated by segment and product line: (In millions) Refining & Marketing Retail Midstream Total Year Ended December 31, 2019 Refined products $ 82,169 $ 26,681 $ 809 $ 109,659 Merchandise 4 6,281 — 6,285 Crude oil 4,402 — — 4,402 Midstream services and other 481 97 3,025 3,603 Sales and other operating revenues $ 87,056 $ 33,059 $ 3,834 $ 123,949 (In millions) Refining & Marketing Retail Midstream Total Year Ended December 31, 2018 Refined products $ 65,916 $ 18,279 $ 887 $ 85,082 Merchandise 11 5,227 — 5,238 Crude oil 3,345 — — 3,345 Midstream services and other 413 40 2,386 2,839 Sales and other operating revenues $ 69,685 $ 23,546 $ 3,273 $ 96,504 (In millions) Refining & Marketing Retail Midstream Total Year Ended December 31, 2017 Refined products $ 50,193 $ 14,113 $ 889 $ 65,195 Merchandise 4 4,893 — 4,897 Crude oil 2,862 — — 2,862 Midstream services and other 323 23 1,433 1,779 Sales and other operating revenues $ 53,382 $ 19,029 $ 2,322 $ 74,733

Supplemental Cash Flow Inform_2

Supplemental Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2019
Supplemental Cash Flow Information [Abstract]
Summary of Supplemental Cash Flow Information	(In millions) 2019 2018 2017 Net cash provided by operating activities included: Interest paid (net of amounts capitalized) $ 1,174 $ 887 $ 525 Net income taxes paid to taxing authorities 491 424 904 Cash paid for amounts included in the measurement of lease liabilities Payments on operating leases (a) 764 — — Interest payments under finance lease obligations (a) 34 — — Net cash provided by financing activities included: Principal payments under finance lease obligations (a) 55 — — Non-cash investing and financing activities: Capital leases — 172 71 Right of use assets obtained in exchange for new operating lease obligations (a) 352 — — Right of use assets obtained in exchange for new finance lease obligations (a) 96 — — Contribution of assets (b) 266 — 337 Fair value of assets acquired (c) 525 — 45 Acquisition: Fair value of MPC shares issued — 19,766 — Fair value of converted equity awards — 203 — (a) Disclosure added in 2019 following the adoption of ASC 842. (b) 2019 includes the contribution of net assets to The Andersons Marathon Holdings LLC and Capline LLC. See Note 14 . 2017 includes MPLX’s contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. See Note 5 . (c) 2019 includes the recognition of The Andersons Marathon Holdings LLC and Capline LLC equity method investments. See Note 14 . 2017 represents emission allowance credits received as part of a litigation settlement agreement.
Schedule of Cash and Cash Equivalents [Table Text Block]	(In millions) December 31, December 31, Cash and cash equivalents $ 1,527 $ 1,687 Restricted cash (a) 2 38 Cash, cash equivalents and restricted cash $ 1,529 $ 1,725 (a) The restricted cash balance is included within other current assets on the consolidated balance sheets.
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) 2019 2018 2017 Additions to property, plant and equipment per the consolidated statements of cash flows $ 5,374 $ 3,578 $ 2,732 Asset retirement expenditures 1 8 2 Increase (decrease) in capital accruals (306 ) 309 67 Total capital expenditures $ 5,069 $ 3,895 $ 2,801

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Loss (Tables)	12 Months Ended
	Dec. 31, 2019
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, 2017 $ (190 ) $ (48 ) $ 4 $ 3 $ (231 ) Other comprehensive income (loss) before reclassifications, net of tax of $23 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 — — — (5 ) (5 ) Tax effect (7 ) 2 (1 ) 2 (4 ) Other comprehensive income (loss) 58 25 (2 ) 6 87 Balance as of December 31, 2018 $ (132 ) $ (23 ) $ 2 $ 9 $ (144 ) (In millions) Pension Benefits Other Benefits Gain on Cash Flow Hedge Workers Compensation Total Balance as of December 31, 2018 $ (132 ) $ (23 ) $ 2 $ 9 $ (144 ) Other comprehensive income (loss) before reclassifications, net of tax of ($52) (71 ) (92 ) — 1 (162 ) Amounts reclassified from accumulated other comprehensive loss: Amortization – prior service credit (a) (45 ) — — — (45 ) – actuarial loss (a) 22 (1 ) — — 21 – settlement loss (a) 9 — — — 9 Other — — (1 ) (4 ) (5 ) Tax effect 5 — — 1 6 Other comprehensive loss (80 ) (93 ) (1 ) (2 ) (176 ) Balance as of December 31, 2019 $ (212 ) $ (116 ) $ 1 $ 7 $ (320 ) (a) These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 23 .

Pension and Other Postretirem_2

Pension and Other Postretirement Benefits (Tables)	12 Months Ended
	Dec. 31, 2019
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) 2019 2018 Projected benefit obligations $ 3,239 $ 2,779 Accumulated benefit obligations 3,031 2,632 Fair value of plan assets 2,531 2,089
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) 2019 2018 2019 2018 Change in benefit obligations: Benefit obligations at January 1 $ 2,779 $ 2,164 $ 884 $ 826 Service cost 234 159 31 30 Interest cost 108 83 37 30 Actuarial (gain) loss 401 (159 ) 125 (71 ) Benefits paid (283 ) (273 ) (45 ) (36 ) Plan amendments — (90 ) (1 ) 34 Acquisitions — 895 — 71 Benefit obligations at December 31 3,239 2,779 1,031 884 Change in plan assets: Fair value of plan assets at January 1 2,089 1,840 — — Actual return on plan assets 436 (115 ) — — Employer contributions 289 115 45 36 Benefits paid from plan assets (283 ) (273 ) (45 ) (36 ) Acquisitions — 522 — — Fair value of plan assets at December 31 2,531 2,089 — — Funded status of plans at December 31 $ (708 ) $ (690 ) $ (1,031 ) $ (884 ) Amounts recognized in the consolidated balance sheets: Current liabilities $ (49 ) $ (21 ) $ (47 ) $ (44 ) Noncurrent liabilities (659 ) (669 ) (984 ) (840 ) Accrued benefit cost $ (708 ) $ (690 ) $ (1,031 ) $ (884 ) Pretax amounts recognized in accumulated other comprehensive loss: (a) Net actuarial loss $ 579 $ 517 $ 135 $ 9 Prior service cost (credit) (250 ) (295 ) 33 35 (a) Amounts exclude those related to LOOP and Explorer, equity method investees with defined benefit pension and postretirement plans for which net losses of $17 million and less than $1 million were recorded in accumulated other comprehensive loss in 2019 , reflecting our ownership share.
Components of Net Periodic Benefit Costs	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) 2019 2018 2017 2019 2018 2017 Components of net periodic benefit cost: Service cost $ 234 $ 159 $ 132 $ 31 $ 30 $ 25 Interest cost 108 83 75 37 30 30 Expected return on plan assets (127 ) (109 ) (100 ) — — — Amortization – prior service credit (45 ) (33 ) (39 ) — (3 ) (3 ) – actuarial (gain) loss 22 31 36 (1 ) (1 ) (2 ) – settlement loss 9 53 52 — — — Net periodic benefit cost (a) $ 201 $ 184 $ 156 $ 67 $ 56 $ 50 Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax): Actuarial (gain) loss $ 93 $ 64 $ (20 ) $ 125 $ (71 ) $ 61 Prior service cost (credit) — (90 ) — (1 ) 34 — Amortization of actuarial gain (loss) (31 ) (84 ) (88 ) 1 1 2 Amortization of prior service credit 45 33 39 — 3 3 Total recognized in other comprehensive loss $ 107 $ (77 ) $ (69 ) $ 125 $ (33 ) $ 66 Total recognized in net periodic benefit cost and other comprehensive loss $ 308 $ 107 $ 87 $ 192 $ 23 $ 116 (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)	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) 2019 2018 2017 2019 2018 2017 Components of net periodic benefit cost: Service cost $ 234 $ 159 $ 132 $ 31 $ 30 $ 25 Interest cost 108 83 75 37 30 30 Expected return on plan assets (127 ) (109 ) (100 ) — — — Amortization – prior service credit (45 ) (33 ) (39 ) — (3 ) (3 ) – actuarial (gain) loss 22 31 36 (1 ) (1 ) (2 ) – settlement loss 9 53 52 — — — Net periodic benefit cost (a) $ 201 $ 184 $ 156 $ 67 $ 56 $ 50 Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax): Actuarial (gain) loss $ 93 $ 64 $ (20 ) $ 125 $ (71 ) $ 61 Prior service cost (credit) — (90 ) — (1 ) 34 — Amortization of actuarial gain (loss) (31 ) (84 ) (88 ) 1 1 2 Amortization of prior service credit 45 33 39 — 3 3 Total recognized in other comprehensive loss $ 107 $ (77 ) $ (69 ) $ 125 $ (33 ) $ 66 Total recognized in net periodic benefit cost and other comprehensive loss $ 308 $ 107 $ 87 $ 192 $ 23 $ 116 (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	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 2019 , 2018 and 2017 . Pension Benefits Other Benefits 2019 2018 2017 2019 2018 2017 Weighted-average assumptions used to determine benefit obligation: Discount rate 3.03 % 4.21 % 3.55 % 3.00 % 4.26 % 3.70 % Rate of compensation increase 4.90 % 5.00 % 5.00 % 4.90 % 5.00 % 5.00 % Weighted-average assumptions used to determine net periodic benefit cost: Discount rate 4.05 % 3.88 % 3.85 % 4.30 % 3.72 % 4.25 % Expected long-term return on plan assets 6.00 % 6.15 % 6.50 % — % — % — % Rate of compensation increase 4.90 % 4.80 % 5.00 % 4.90 % 5.00 % 5.00 %
Assumed Health Care Cost Trend Rates	The following summarizes the assumed health care cost trend rates. December 31, 2019 2018 2017 Health care cost trend rate assumed for the following year: Medical: Pre-65 6.20 % 6.80 % 6.75 % Prescription drugs 8.10 % 9.50 % 8.75 % 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 2027 2026 Prescription drugs 2027 2027 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 $ 6 $ (5 ) Effect on other postretirement benefit obligations 52 (45 )
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, 2019 and 2018 . December 31, 2019 (In millions) Level 1 Level 2 Level 3 Total Cash and cash equivalents $ — $ 22 $ — $ 22 Equity: Common stocks 125 135 — 260 Mutual funds 188 — — 188 Pooled funds — 442 — 442 Fixed income: Corporate 160 815 — 975 Government 113 217 — 330 Pooled funds — 229 — 229 Private equity — — 30 30 Real estate — — 24 24 Other 58 (46 ) 19 31 Total investments, at fair value $ 644 $ 1,814 $ 73 $ 2,531 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
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: 2019 (In millions) Private Equity Real Estate Other Total Beginning balance $ 41 $ 29 $ 18 $ 88 Actual return on plan assets: Realized 5 2 — 7 Unrealized (3 ) (2 ) 1 (4 ) Purchases 1 1 — 2 Sales (14 ) (6 ) — (20 ) Ending balance $ 30 $ 24 $ 19 $ 73 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
Estimated Future Benefit Payment	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 2020 $ 248 $ 47 2021 216 49 2022 218 50 2023 220 51 2024 233 52 2025 through 2029 1,187 283
Multi Employer Pension Plan	Our participation in this plan for 2019 , 2018 and 2017 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 2019 and 2018 is for the plan’s year ended December 31, 2018 and December 31, 2017 , 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 2019 , 2018 and 2017 contributions. Our portion of the contributions does not make up more than five percent of total contributions to the plan. Pension FIP/RP Status MPC Contributions In millions ) Surcharge Expiration Date of Pension Fund EIN 2019 2018 2019 2018 2017 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 2020 . A total of 263 employees participated in the plan as of December 31, 2019 .

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [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) 2019 2018 2017 Stock-based compensation expense $ 161 $ 133 $ 51 Tax benefit recognized on stock-based compensation expense 37 32 19 Cash received by MPC upon exercise of stock option awards 10 24 46 Tax (expense)/benefit received for tax deductions for stock awards exercised (3 ) 14 25
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: 2019 2018 2017 Weighted average exercise price per share $ 61.92 $ 67.71 $ 50.57 Expected life in years 6.0 6.2 6.3 Expected volatility 32 % 34 % 35 % Expected dividend yield 3.4 % 3.0 % 3.0 % Risk-free interest rate 2.4 % 2.7 % 2.1 % Weighted average grant date fair value of stock option awards granted $ 13.65 $ 17.21 $ 13.42
Summary of Stock Option Award Activity	The following is a summary of our common stock option activity in 2019 : Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Terms (in years) Aggregate Intrinsic Value (in millions) Outstanding at December 31, 2018 8,724,595 $ 37.07 Granted 1,952,324 61.92 Exercised (529,706 ) 19.12 Forfeited or expired (128,846 ) 61.29 Outstanding at December 31, 2019 10,018,367 42.55 Vested and expected to vest at December 31, 2019 9,987,326 26.84 5.2 $ 187 Exercisable at December 31, 2019 7,404,952 35.85 4.0 183
Summary of Restricted Stock Award Activity	The following is a summary of restricted stock award activity of our common stock in 2019 : Restricted Stock Restricted Stock Units Number of Shares Weighted Average Grant Date Fair Value Number of Units Weighted Unvested at December 31, 2018 989,019 $ 57.19 3,120,116 $ 82.40 Granted 1,059,837 61.14 36,391 58.30 Vested (595,440 ) 52.16 (1,527,145 ) 81.84 Forfeited (103,618 ) 61.20 (147,616 ) 82.37 Unvested at December 31, 2019 1,349,798 62.20 1,481,746 82.39
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 2019 $ 32 $ 61.14 $ 120 $ 58.30 2018 49 71.19 39 72.43 2017 28 50.25 5 53.19
Schedule of Performance Unit Awards	The following table presents a summary of the 2019 activity for performance unit awards to be settled in shares: Number of Units Weighted Average Grant Date Fair Value Unvested at December 31, 2018 8,607,250 $ 0.79 Granted 6,256,250 0.72 Vested (3,494,000 ) 0.62 Forfeited (170,000 ) 0.81 Unvested at December 31, 2019 11,199,500 0.80
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: 2019 2018 2017 Risk-free interest rate 2.5 % 2.3 % 1.5 % Look-back period (in years) 2.8 2.8 2.8 Expected volatility 29.7 % 34.0 % 36.1 % Grant date fair value of performance units granted $ 0.72 $ 0.83 $ 0.92

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Lease, Cost	Under ASC 842, the components of lease cost were as follows: (In millions) 2019 Finance lease cost: Amortization of right of use assets $ 64 Interest on lease liabilities 43 Operating lease cost 793 Variable lease cost 91 Short-term lease cost 746 Total lease cost $ 1,737
Supplemental Balance Sheet Disclosures [Text Block]	Supplemental balance sheet data related to leases were as follows: (In millions) December 31, 2019 Operating leases Assets Right of use assets $ 2,459 Liabilities Operating lease liabilities $ 604 Long-term operating lease liabilities 1,875 Total operating lease liabilities $ 2,479 Weighted average remaining lease term (in years) 6.2 Weighted average discount rate 4.02 % Finance leases Assets Property, plant and equipment, gross $ 807 Accumulated depreciation 227 Property, plant and equipment, net $ 580 Liabilities Debt due within one year $ 62 Long-term debt 636 Total finance lease liabilities $ 698 Weighted average remaining lease term (in years) 11.9 Weighted average discount rate 6.50 %
Operating & Finance Leases, Liability, Maturity [Table Text Block]	As of December 31, 2019 , maturities of lease liabilities for operating lease obligations and finance lease obligations having initial or remaining non-cancellable lease terms in excess of one year are as follows: (In millions) Operating Finance 2020 $ 698 $ 96 2021 590 87 2022 402 95 2023 287 98 2024 222 84 2025 and thereafter 634 527 Gross lease payments 2,833 987 Less: imputed interest 354 289 Total lease liabilities $ 2,479 $ 698 Presented in accordance with ASC 840, future minimum commitments as of December 31, 2018 for operating lease obligations and capital lease obligations having initial or remaining non-cancellable lease terms in excess of one year were as follows: (In millions) Operating Capital 2019 $ 709 $ 70 2020 619 71 2021 553 66 2022 389 75 2023 295 82 2024 and thereafter 858 586 Total minimum lease payments $ 3,423 950 Less: imputed interest costs 301 Present value of net minimum lease payments $ 649
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, 2019 : (In millions) 2020 $ 186 2021 179 2022 177 2023 170 2024 167 2025 and thereafter 1,072 Total minimum future rentals $ 1,951
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, 2019 : (In millions) Natural gas gathering and NGL transportation pipelines and facilities $ 1,121 Natural gas processing facilities 686 Terminals and related assets 83 Land, building, office equipment and other 45 Property, plant and equipment 1,935 Less accumulated depreciation 327 Total property, plant and equipment, net $ 1,608

Selected Quarterly Financial _2

Selected Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Data [Abstract]
Schedule Of Quarterly Financial Information	2019 Quarter Ended (In millions, except per share data) March 31 June 30 September 30 December 31 Sales and other operating revenues (a) $ 28,267 $ 33,547 $ 31,043 $ 31,092 Income from operations 669 2,042 2,024 841 Net income 259 1,367 1,367 262 Net income (loss) attributable to MPC (7 ) 1,106 1,095 443 Net income (loss) attributable to MPC per share (b) : Basic $ (0.01 ) $ 1.67 $ 1.67 $ 0.68 Diluted (0.01 ) 1.66 1.66 0.68 2018 Quarter Ended (In millions, except per share data) March 31 June 30 September 30 December 31 Sales and other operating revenues (a) $ 18,866 $ 22,317 $ 22,988 $ 32,333 Income from operations 440 1,711 1,403 2,017 Net income 235 1,235 941 1,195 Net income attributable to MPC 37 1,055 737 951 Net income attributable to MPC per share (b) : Basic $ 0.08 $ 2.30 $ 1.63 $ 1.38 Diluted 0.08 2.27 1.62 1.35 (a) Includes sales to related parties. (b) 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 a_2

Description of the Business and Basis of Presentation (Description of the Business and Basis of Presentation) (Details) bbl / d in Millions	12 Months Ended
	Dec. 31, 2019Storebbl / drefinery
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Crude capacity | bbl / d	3
Number of refineries | refinery	16
Number of branded outlets	6,900
Number of retail transportation fuel and convenience stores	3,900
Number of direct dealer locations	1,070

Summary of Principal Accounti_3

Summary of Principal Accounting Policies (Principal Accounting Policies) (Details)	12 Months Ended
	Dec. 31, 2019
Summary Of Principal Accounting Policies [Line Items]
Accounts receivable number of days past-due evaluated for doubtful accounts	180 days
Stock Options
Summary Of Principal Accounting Policies [Line Items]
Implied volatility rate weighting (in percentage)	50.00%
Historical volatility rate weighting (in percentage)	50.00%
Minimum
Summary Of Principal Accounting Policies [Line Items]
Estimated useful lives (in years)	2 years
Maximum
Summary Of Principal Accounting Policies [Line Items]
Estimated useful lives (in years)	51 years
MPLX | MPC
Summary Of Principal Accounting Policies [Line Items]
MPC's partnership interest in MLPs (in percentage)	63.00%

Accounting Standards (ASU 2016-

Accounting Standards (ASU 2016-02 Leases and related updates) (Details) - Accounting Standards Update 2016-02 $ in Billions	12 Months Ended
	Dec. 31, 2019USD ($)
Operating Lease Right Of Use Asset
Effect of adoption, quantification	$ 2.8
Operating Lease Liability
Effect of adoption, quantification	$ 2.9

Master Limited Partnership (Det

Master Limited Partnership (Details)	Dec. 31, 2019
MPLX | MPC
Noncontrolling Interest [Line Items]
MPC's partnership interest in MLPs (in percentage)	63.00%

Master Limited Partnership (MPL

Master Limited Partnership (MPLX's Acquisition of ANDX) (Details) - USD ($) $ / shares in Units, $ in Millions	Jul. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Noncontrolling Interest [Line Items]
Equity transactions of MPLX & ANDX		$ (590)	$ (570)	$ 444
Additional Paid-in Capital
Noncontrolling Interest [Line Items]
Equity transactions of MPLX & ANDX	$ (55)	(684)	2,357	110
Deferred income tax impact from changes in equity	$ 642	$ 633	$ 571	$ 29
Preferred Partner | Preferred Class B
Noncontrolling Interest [Line Items]
Distributions declared, per unit	$ 68.75
Public
Noncontrolling Interest [Line Items]
Common units conversion ratio - ANDX to MPLX	1.135
Nonpublic
Noncontrolling Interest [Line Items]
Common units conversion ratio - ANDX to MPLX	1.0328
ANDX
Noncontrolling Interest [Line Items]
Preferred units, outstanding	600,000
MPLX | Series B Preferred Stock
Noncontrolling Interest [Line Items]
Preferred units, outstanding	600,000

Master Limited Partnership (M_2

Master Limited Partnership (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
Limited Partner
Noncontrolling Interest [Line Items]
Units issued, number of units	112,000	19,000	13,000
Conversion of stock, shares issued	275,000
General Partner
Noncontrolling Interest [Line Items]
Units issued, number of units	2,000	378	264
MPLX 364-day term loan
Noncontrolling Interest [Line Items]
Line of credit facility, maximum borrowing capacity	$ 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 Partnership (Non

Master Limited Partnership (Noncontrolling Interest) (Details) - USD ($) $ in Millions	Jul. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Increase (decrease) in MPC's additional paid-in capital, net of tax		$ (590)	$ (570)	$ 444
Additional Paid-in Capital
Increase due to the issuance of MPLX common units and general partner units to MPC		0	1,114	114
Increase due to GP/IDR Exchange		0	1,808	0
Increase (decrease) due to the issuance of MPLX & ANDX common units		(51)	6	25
Increase (decrease) in MPC's additional paid-in capital		(51)	2,928	139
Tax impact	$ (642)	(633)	(571)	(29)
Increase (decrease) in MPC's additional paid-in capital, net of tax	$ (55)	$ (684)	$ 2,357	$ 110

Acquisitions (Acquisition of An

Acquisitions (Acquisition of Andeavor) (Details) - USD ($) $ / shares in Units, $ in Millions	Oct. 01, 2018	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Fair value of converted equity awards			$ 0	$ 203	$ 0
Goodwill		$ 20,184	20,040	20,184	3,586
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	5,572	5,020	519
Midstream
Business Acquisition [Line Items]
Goodwill		10,323	$ 9,517	$ 10,323	$ 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
Cash payment for acquisition	$ 3,486
Fair value of converted equity awards	203
Goodwill	17,295
Goodwill, expected tax deductible amount	1,000
Finite-lived intangibles	2,800
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	5,200
Andeavor | Midstream
Business Acquisition [Line Items]
Goodwill	8,100
Andeavor | Retail
Business Acquisition [Line Items]
Goodwill	$ 3,900

Acquisitions (Fair Value of Con

Acquisitions (Fair Value of Consideration Transferred - Andeavor) (Details) - USD ($) $ in Millions	Oct. 01, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Fair value of MPC shares issued		$ 0	$ 19,766	$ 0
Fair value of converted equity awards		$ 0	$ 203	$ 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, 2019	Dec. 31, 2018	Oct. 01, 2018	Dec. 31, 2017
Goodwill		$ 20,040	$ 20,184		$ 3,586
Andeavor
Cash and cash equivalents				$ 382
Receivables				2,739
Inventories				5,241
Other current assets				372
Equity method investments				752
Property, plant and equipment, net				15,524
Other noncurrent assets	[1]			3,075
Total assets acquired				28,085
Accounts payable				3,962
Payroll and benefits payable				357
Accrued taxes				480
Debt due within one year				34
Other current liabilities				419
Long-term debt				8,876
Deferred income taxes				1,549
Defined benefit postretirement plan obligations				432
Deferred credit and other liabilities				747
Noncontrolling interests				5,062
Total liabilities and noncontrolling interest assumed				21,918
Net assets acquired excluding goodwill				6,167
Goodwill				17,295
Net assets acquired				23,462
Andeavor | Previously Reported
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	[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
Andeavor | Restatement Adjustment
Cash and cash equivalents				0
Receivables				(5)
Inventories				37
Other current assets				(6)
Equity method investments				(113)
Property, plant and equipment, net				(1,021)
Other noncurrent assets	[1]			(11)
Total assets acquired				(1,119)
Accounts payable				(41)
Payroll and benefits payable				9
Accrued taxes				(110)
Debt due within one year				0
Other current liabilities				27
Long-term debt				1
Deferred income taxes				(60)
Defined benefit postretirement plan obligations				0
Deferred credit and other liabilities				33
Noncontrolling interests				3
Total liabilities and noncontrolling interest assumed				(138)
Net assets acquired excluding goodwill				(981)
Goodwill				981
Net assets acquired				$ 0
[1]	Includes intangible assets.

Acquisitions (Pro Forma Financi

Acquisitions (Pro Forma Financial Information - Andeavor) (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										$ 123,949	$ 96,504
Sales and other operating revenue, including excise taxes												$ 74,733
Net income attributable to MPC		$ 443	$ 1,095	$ 1,106	$ (7)	$ 951	$ 737	$ 1,055	$ 37	$ 2,637	2,780	3,432
Andeavor
Business Acquisition [Line Items]
Sales and other operating revenues, excluding consumer excise taxes	[1]										131,921
Sales and other operating revenue, including excise taxes	[1]											118,179
Net income attributable to MPC											$ 4,218	$ 4,712
[1]	he 2018 period reflects an election to present certain taxes on a net basis concurrent with our adoption of ASC 606.

Acquisitions (Acquisition of Te

Acquisitions (Acquisition of Terminal and Retail Locations in New York) (Details) $ in Millions	Jul. 12, 2019USD ($)Storebbl	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Business Acquisition [Line Items]
Goodwill		$ 20,040	$ 20,184	$ 3,586
NOCO
Business Acquisition [Line Items]
Barrels handled | bbl	900,000
Number of stores | Store	33
Cash payment for acquisition	$ 135
Property, plant and equipment, net	38
Inventories	3
Goodwill	$ 94

Acquisitions (Acquisition of Ex

Acquisitions (Acquisition of Express Mart) (Details) $ in Millions	Nov. 16, 2018USD ($)Store	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Business Acquisition [Line Items]
Goodwill		$ 20,040	$ 20,184	$ 3,586
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 ($)bbl / dbbl	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Business Acquisition [Line Items]
Goodwill		$ 20,040	$ 20,184	$ 3,586
Mt. Airy Terminal
Business Acquisition [Line Items]
Storage capacity | bbl	4
Barrels handled | bbl / d	120
Mt. Airy Terminal | MPLX
Business Acquisition [Line Items]
Cash payment for acquisition	$ 446
Property, plant and equipment, net	336
Goodwill	121
Mt. Airy Terminal | MPLX | Previously Reported
Business Acquisition [Line Items]
Cash payment for acquisition	451
Mt. Airy Terminal | MPLX | Restatement Adjustment
Business Acquisition [Line Items]
Cash payment for acquisition	$ 5

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) $ in Millions	Feb. 15, 2017USD ($)
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, 2019bbl / d
Schedule of Equity Method Investments [Line Items]
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 | 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

Variable Interest Entities (Bal

Variable Interest Entities (Balance Sheet Information for Consolidated VIEs) (Details) - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Assets
Cash and cash equivalents		$ 1,527	$ 1,687
Receivables, less allowance for doubtful accounts		7,872	5,853
Inventories		10,243	9,837
Other current assets		528	646
Equity method investments		6,898	5,898
Property, plant and equipment, net		45,615	45,058
Goodwill		20,040	20,184	$ 3,586
Right of use assets	[1]	2,459	0
Other noncurrent assets		3,374	3,777
Liabilities
Accounts payable		11,623	9,366
Payroll and benefits payable		1,126	1,152
Accrued taxes		1,186	1,446
Debt due within one year		711	544
Operating lease liabilities	[1]	604	0
Other current liabilities		897	708
Long-term debt		28,127	26,980
Long-term operating lease liabilities	[1]	1,875	0
Deferred credits and other liabilities		1,265	1,318
VIE, Primary Beneficiary | MPLX
Assets
Cash and cash equivalents		15	68
Receivables, less allowance for doubtful accounts		615	425
Inventories		110	77
Other current assets		110	45
Equity method investments		5,275	4,174
Property, plant and equipment, net		22,174	14,639
Goodwill		9,536	2,586
Right of use assets		365	0
Other noncurrent assets		1,323	458
Liabilities
Accounts payable		744	776
Payroll and benefits payable		5	2
Accrued taxes		80	48
Debt due within one year		9	1
Operating lease liabilities		66	0
Other current liabilities		259	177
Long-term debt		19,704	13,392
Deferred income taxes		12	13
Long-term operating lease liabilities		302	0
Deferred credits and other liabilities		$ 409	276
VIE, Primary Beneficiary | ANDX
Assets
Cash and cash equivalents			10
Receivables, less allowance for doubtful accounts			199
Inventories			22
Other current assets			57
Equity method investments			602
Property, plant and equipment, net			6,845
Goodwill			1,051
Right of use assets			0
Other noncurrent assets			1,242
Liabilities
Accounts payable			215
Payroll and benefits payable			10
Accrued taxes			23
Debt due within one year			504
Operating lease liabilities			0
Other current liabilities			77
Long-term debt			4,469
Deferred income taxes			1
Long-term operating lease liabilities			0
Deferred credits and other liabilities			$ 68
[1]	We adopted ASU No. 2016-02, Leases (“ASC 842”), as of January 1, 2019. See Notes 3 and 25 for further information.

Variable Interest Entities (Non

Variable Interest Entities (Non-Consolidated VIEs) (Details) $ in Millions	Dec. 31, 2019USD ($)
Crowley Coastal Partners, LLC
Schedule of Equity Method Investments [Line Items]
Maximum loss exposure, amount	$ 440

Related Party Transactions (Rel

Related Party Transactions (Related Party Transactions) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transactions [Abstract]
Sales to related parties	$ 768	$ 754	$ 629
Purchases from related parties	$ 763	$ 610	$ 570

Earnings per Share (Summary Of

Earnings per Share (Summary Of Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended																12 Months Ended
	Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Basic earnings per share:
Net income attributable to MPC	$ 443		$ 1,095		$ 1,106		$ (7)		$ 951		$ 737		$ 1,055		$ 37		$ 2,637	$ 2,780	$ 3,432
Income allocated to participating securities, basic																	1	1	2
Income available to common stockholders – basic																	$ 2,636	$ 2,779	$ 3,430
Weighted average common shares outstanding (in shares)																	659	518	507
Net income attributable to MPC per share – basic	$ 0.68	[1]	$ 1.67	[1]	$ 1.67	[1]	$ (0.01)	[1]	$ 1.38	[1]	$ 1.63	[1]	$ 2.30	[1]	$ 0.08	[1]	$ 4	$ 5.36	$ 6.76
Diluted earnings per share:
Net income attributable to MPC	$ 443		$ 1,095		$ 1,106		$ (7)		$ 951		$ 737		$ 1,055		$ 37		$ 2,637	$ 2,780	$ 3,432
Income allocated to participating securities, diluted																	1	1	2
Income available to common stockholders – diluted																	$ 2,636	$ 2,779	$ 3,430
Weighted average common shares outstanding (in shares)																	659	518	507
Effect of dilutive securities (in shares)																	5	8	5
Weighted average common shares, including dilutive effect (in shares)																	664	526	512
Net income attributable to MPC per share – diluted	$ 0.68	[1]	$ 1.66	[1]	$ 1.66	[1]	$ (0.01)	[1]	$ 1.35	[1]	$ 1.62	[1]	$ 2.27	[1]	$ 0.08	[1]	$ 3.97	$ 5.28	$ 6.70
[1]	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.

Earnings per Share (Anti-diluti

Earnings per Share (Anti-dilutive Shares) (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
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	3	0	1

Equity (Narrative) (Details)

Equity (Narrative) (Details) $ in Millions	Dec. 31, 2019USD ($)
Equity [Abstract]
Stock repurchase plan remaining authorized amount	$ 2,960

Equity (Share Repurchases) (Det

Equity (Share Repurchases) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Equity [Abstract]
Number of shares repurchased	34	47	44
Cash paid for shares repurchased	$ 1,950	$ 3,287	$ 2,372
Average cost per share	$ 58.87	$ 69.46	$ 53.85

Segment Information (Narrative)

Segment Information (Narrative) (Details)	12 Months Ended
	Dec. 31, 2019refinerySegment	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Number of reportable segments | Segment	3
Number of refineries | refinery	16
None | Maximum
Segment Reporting Information [Line Items]
Percent of annual revenues	10.00%	10.00%	10.00%

Segment Information (Income Fro

Segment Information (Income From Operations Attributable To Operating Segments) (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										$ 123,949	$ 96,504
Sales and other operating revenue, including excise taxes												$ 74,733
Income from operations		$ 841	$ 2,024	$ 2,042	$ 669	$ 2,017	$ 1,403	$ 1,711	$ 440	5,576	5,571	4,018
Depreciation and amortization										3,638	2,490	2,114
Refining & Marketing
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										87,056	69,685
Sales and other operating revenue, including excise taxes	[1]											53,382
Retail
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										33,059	23,546
Sales and other operating revenue, including excise taxes	[1]											19,029
Midstream
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										3,834	3,273
Sales and other operating revenue, including excise taxes	[1]											2,322
Reportable Segment [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										123,949	96,504
Sales and other operating revenue, including excise taxes	[1]											74,733
Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										24,620	16,307
Sales and other operating revenue, including excise taxes	[2]											12,756
Intersegment Eliminations | Refining & Marketing
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										19,686	12,914
Sales and other operating revenue, including excise taxes	[2]											11,309
Intersegment Eliminations | Retail
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										8	6
Sales and other operating revenue, including excise taxes	[2]											4
Intersegment Eliminations | Midstream
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										4,926	3,387
Sales and other operating revenue, including excise taxes	[2]											1,443
Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										148,569	112,811
Sales and other operating revenue, including excise taxes												87,489
Income from operations										7,543	6,261	4,389
Depreciation and amortization										3,460	2,412	2,056	[3]
Segment capital expenditures and investments										5,896	4,147	2,968	[4]
Operating Segments | Refining & Marketing
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										106,742	82,599
Sales and other operating revenue, including excise taxes												64,691
Income from operations										2,367	2,481	2,321
Depreciation and amortization										1,665	1,174	1,082
Segment capital expenditures and investments										1,999	1,057	832
Operating Segments | Retail
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										33,067	23,552
Sales and other operating revenue, including excise taxes												19,033
Income from operations										1,582	1,028	729
Depreciation and amortization										528	353	275
Segment capital expenditures and investments										607	460	381
Operating Segments | Midstream
Segment Reporting Information [Line Items]
Sales and other operating revenues, excluding consumer excise taxes										8,760	6,660
Sales and other operating revenue, including excise taxes												3,765
Income from operations										3,594	2,752	1,339
Depreciation and amortization										1,267	885	699
Segment capital expenditures and investments										$ 3,290	$ 2,630	$ 1,755
[1]	Includes related party sales. See Note 7 for additional information.
[2]	Management believes intersegment transactions were conducted under terms comparable to those with unaffiliated parties.
[3]	Differences between segment totals and MPC totals represent amounts related to unallocated items and are included in items not allocated to segment in the reconciliation below
[4]	ncludes changes in capital expenditure accruals and investments in affiliates

Segment Information (Reconcilia

Segment Information (Reconciliation Of Segment Income From Operations To Income Before Income Taxes) (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations		$ 841	$ 2,024	$ 2,042	$ 669	$ 2,017	$ 1,403	$ 1,711	$ 440	$ 5,576		$ 5,571		$ 4,018
Net interest and other financial costs										1,247		1,003		674
Income before income taxes										4,329		4,568		3,344
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations										7,543		6,261		4,389
Corporate and Other
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations	[1]									(805)		(502)		(365)
Segment Reconciling Items
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Equity method investment restructuring gains										259	[2]	0		0
Transaction-related costs										(160)	[3]	(197)	[3]	0
Litigation										(22)		0		(29)
Impairment	[4]									$ (1,239)		$ 9		$ 23
[1]	Corporate and other unallocated items consists primarily of MPC’s corporate administrative expenses and costs related to certain non-operating assets, except for corporate overhead expenses attributable to MPLX, which are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Retail segments.
[2]	Includes gains related to The Andersons Marathon Holdings LLC and Capline Pipeline Company LLC. See Note 14 .
[3]	2019 includes costs incurred in connection with the proposed Speedway separation, Midstream strategic review and other related efforts. Both 2019 and 2018 include employee severance, retention and other costs related to the acquisition of Andeavor. Effective October 1, 2019, we have discontinued reporting Andeavor transaction-related costs as one year has passed since the Andeavor acquisition. The post October 1, 2019 transaction costs are immaterial and reported in corporate and other unallocated items.
[4]	2018 and 2017 includes MPC’s share of gains from the sale of assets remaining from the Sandpiper pipeline project, which was cancelled and impaired in 2016.

Segment Information (Reconcil_2

Segment Information (Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Plus items not allocated to segments:
Total capital expenditures	[1]	$ 5,069	$ 3,895	$ 2,801
Operating Segments
Segment Reporting, Other Significant Reconciling Item [Line Items]
Segment capital expenditures and investments		5,896	4,147	2,968	[2]
Investments in equity method investments		1,064	409	305
Corporate and Other
Plus items not allocated to segments:
Corporate		100	77	83
Capitalized interest		$ 137	$ 80	$ 55
[1]	ncludes changes in capital expenditure accruals. See Note 21 for a reconciliation of total capital expenditures to additions to property, plant and equipment as reported in the consolidated statements of cash flows.
[2]	ncludes changes in capital expenditure accruals and investments in affiliates

Net Interest and Other Financ_3

Net Interest and Other Financial Costs (Net Interest and Other Financial Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Income and Expenses [Abstract]
Interest income	$ (40)	$ (87)	$ (27)
Interest expense	1,396	1,026	688
Interest capitalized	(158)	(80)	(63)
Pension and other postretirement non-service costs	3	53	49
Loss on extinguishment of debt	0	64	0
Other financial costs	46	27	27
Net interest and other financial income (costs)	$ 1,247	$ 1,003	$ 674

Income Taxes (Income Taxes Narr

Income Taxes (Income Taxes Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ 11	$ 10
Unrecognized tax benefits that would impact effective income tax rate	23
Uncertain tax positions, reasonably possible increase or decrease during the next twelve months	2
Statute of limitations	160	12	$ 0
Unrecognized tax benefits income tax net penalties and interest expense (benefits)	(2)	1	$ 3
Interest and penalties accrued	7	18
United States Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	7	7
States
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	11	$ 10
Andeavor
Operating Loss Carryforwards [Line Items]
Statute of limitations	$ 159

Income Taxes (Components Of Inc

Income Taxes (Components Of Income Tax Provisions (Benefits)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current:
Federal	$ (3)	$ 715	$ 681
State and local	53	178	98
Foreign	1	22	(6)
Total current	51	915	773
Deferred:
Federal	898	2	(1,270)
State and local	116	61	33
Foreign	9	(16)	4
Total deferred	1,023	47	(1,233)
Income tax provision (benefit)	$ 1,074	$ 962	$ (460)

Income Taxes (Reconciliation Of

Income Taxes (Reconciliation Of Federal Statutory Income Tax Rate) (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Statutory rate applied to income before income taxes	21.00%	21.00%	35.00%
State and local income taxes, net of federal income tax effects	3.00%	4.00%	2.00%
Goodwill impairment	3.00%	0.00%	0.00%
Noncontrolling interests	(3.00%)	(4.00%)	(4.00%)
TCJA legislation	0.00%	0.00%	(45.00%)
Other	1.00%	0.00%	(2.00%)
Provision for income taxes	25.00%	21.00%	(14.00%)

Income Taxes (Components Of Def

Income Taxes (Components Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Employee benefits	$ 693	$ 660
Environmental remediation	99	111
Debt financing	17	39
Net operating loss carryforwards	18	17
Foreign currency	15	28
Tax credit carryforwards	14	21
Other	57	88
Total deferred tax assets	913	964
Deferred tax liabilities:
Property, plant and equipment	3,444	2,830
Inventories	652	678
Investments in subsidiaries and affiliates	3,114	2,130
Intangibles	56	97
Other	19	64
Total deferred tax liabilities	7,285	5,799
Net deferred tax liabilities	$ 6,372	$ 4,835

Income Taxes (Components Of Net

Income Taxes (Components Of Net Deferred Tax Liabilities Classified In Consolidated Balance Sheets) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Assets
Other noncurrent assets	$ 20	$ 29
Liabilities
Deferred income taxes	6,392	4,864
Net deferred tax liabilities	$ 6,372	$ 4,835

Income Taxes (Summary Of Income

Income Taxes (Summary Of Income Tax Returns Subject To Examination) (Details)	12 Months Ended
	Dec. 31, 2019
United States Federal | Minimum
Income Tax Examination [Line Items]
Tax years	2011
United States Federal | Maximum
Income Tax Examination [Line Items]
Tax years	2018
States | Minimum
Income Tax Examination [Line Items]
Tax years	2006
States | Maximum
Income Tax Examination [Line Items]
Tax years	2018

Income Taxes (Summary Of Activi

Income Taxes (Summary Of Activity In Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
January 1 balance	$ 211	$ 19	$ 7
Additions for tax positions of prior years	2	0	13
Reductions for tax positions of prior years	(2)	(5)	0
Settlements, decrease	(19)	0	(1)
Statute of limitations	160	12	0
Acquired from Andeavor	0	209	0
December 31 balance	$ 32	$ 211	$ 19

Inventories (Summary Of Invento

Inventories (Summary Of Inventories) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Crude oil	$ 3,472	$ 3,655
Refined products	5,548	5,234
Materials and supplies	996	720
Merchandise	227	228
Total	$ 10,243	$ 9,837

Inventories (Narrative) (Detail

Inventories (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Total inventory LIFO percentage	90.00%	92.00%
Excess of current acquisition costs over stated LIFO value	$ 871	$ 0
Effect of LIFO inventory liquidation on income	$ 0	$ 0	$ 0

Equity Method Investments (The

Equity Method Investments (The Andersons Marathon Holdings LLC) (Details) - USD ($) $ in Millions	Oct. 01, 2019	Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Contribution of net assets		$ 266	[1]	$ 0	$ 337	[1]
Fair value of asset acquired		$ 525	[2]	$ 0	$ 45	[2]
The Andersons Marathon Holdings LLC
Schedule of Equity Method Investments [Line Items]
Contribution of net assets	$ 123
Fair value of asset acquired	175
Non-cash gain on exchange of equity ownership interests	$ 52
[1]	2019 includes the contribution of net assets to The Andersons Marathon Holdings LLC and Capline LLC. See Note 14 . 2017 includes MPLX’s contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. See Note 5 .
[2]	2019 includes the recognition of The Andersons Marathon Holdings LLC and Capline LLC equity method investments. See Note 14 . 2017 represents emission allowance credits received as part of a litigation settlement agreement.

Equity Method Investments (Capl

Equity Method Investments (Capline LLC) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Contribution of net assets		$ 266	[1]	$ 0	$ 337	[1]
Fair value of asset acquired		$ 525	[2]	$ 0	$ 45	[2]
Capline LLC
Schedule of Equity Method Investments [Line Items]
Undivided joint interest, ownership percentage	33.00%
Equity method investments, ownership percentage	33.00%
Contribution of net assets	$ 143
Fair value of asset acquired	350
Equity method investment restructuring gains	$ 207
[1]	2019 includes the contribution of net assets to The Andersons Marathon Holdings LLC and Capline LLC. See Note 14 . 2017 includes MPLX’s contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. See Note 5 .
[2]	2019 includes the recognition of The Andersons Marathon Holdings LLC and Capline LLC equity method investments. See Note 14 . 2017 represents emission allowance credits received as part of a litigation settlement agreement.

Equity Method Investments (Impa

Equity Method Investments (Impairments) (Details) - MPLX $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments from asset impairment and elimination of basis differential	$ 28
Equity Method Investment - Basis Difference
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments from asset impairment and elimination of basis differential	$ 14

Equity Method Investments (Sche

Equity Method Investments (Schedule Of Equity Method Investments) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 6,898		$ 5,898
The Andersons Marathon Holdings LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	50.00%
Watson Cogeneration Company
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	51.00%
PFJ Southeast
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	29.00%
Sherwood Midstream
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	50.00%
Capline LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage		33.00%
Gray Oak Pipeline LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	25.00%
MPLX | Andeavor Logistics Rio Pipeline
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	67.00%
MPLX | Centrahoma Processing LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	40.00%
MPLX | Explorer Pipeline [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	25.00%
MPLX | Illinois Extension Pipeline
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	35.00%
MPLX | LOOP
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	41.00%
MPLX | MarEn Bakken Company LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	25.00%
MPLX | MarkWest EMG Jefferson Dry Gas
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	67.00%
MPLX | MarkWest Utica EMG
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	56.00%
MPLX | Minnesota Pipe Line Company, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	17.00%
MPLX | Rendezvous Gas Services, L.L.C.
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	78.00%
MPLX | Sherwood Midstream Holdings
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	53.00%
MPLX | Sherwood Midstream
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	50.00%
MPLX | Whistler Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	38.00%
MPLX | Wink to Webster Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	15.00%
Marathon Petroleum Corporation | LOOP
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	10.00%
Marathon Petroleum Corporation | Capline LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	33.00%
Marathon Petroleum Corporation | Crowley Coastal Partners, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	50.00%
Marathon Petroleum Corporation | Gray Oak Pipeline LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	25.00%
Refining & Marketing
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 203		205
Refining & Marketing | The Andersons Marathon Holdings LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	177		0
Refining & Marketing | Watson Cogeneration Company
Schedule of Equity Method Investments [Line Items]
Equity method investments	26		84
Refining & Marketing | Other equity method investees
Schedule of Equity Method Investments [Line Items]
Equity method investments	0		121	[1]
Retail
Schedule of Equity Method Investments [Line Items]
Equity method investments	330		341
Retail | PFJ Southeast
Schedule of Equity Method Investments [Line Items]
Equity method investments	330		341
Midstream
Schedule of Equity Method Investments [Line Items]
Equity method investments	6,365		5,352
Midstream | MPLX
Schedule of Equity Method Investments [Line Items]
Equity method investments	5,275		4,901
Midstream | MPLX | Andeavor Logistics Rio Pipeline
Schedule of Equity Method Investments [Line Items]
Equity method investments	202		181
Midstream | MPLX | Centrahoma Processing LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	153		160
Midstream | MPLX | Explorer Pipeline [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	83		90
Midstream | MPLX | Illinois Extension Pipeline
Schedule of Equity Method Investments [Line Items]
Equity method investments	265		275
Midstream | MPLX | LOOP
Schedule of Equity Method Investments [Line Items]
Equity method investments	238		226
Midstream | MPLX | MarEn Bakken Company LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	481		498
Midstream | MPLX | MarkWest EMG Jefferson Dry Gas
Schedule of Equity Method Investments [Line Items]
Equity method investments	302		236
Midstream | MPLX | MarkWest Utica EMG
Schedule of Equity Method Investments [Line Items]
Equity method investments	1,984		2,039
Midstream | MPLX | Minnesota Pipe Line Company, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	190		197
Midstream | MPLX | Rendezvous Gas Services, L.L.C.
Schedule of Equity Method Investments [Line Items]
Equity method investments	170		248
Midstream | MPLX | Sherwood Midstream Holdings
Schedule of Equity Method Investments [Line Items]
Equity method investments	157		157
Midstream | MPLX | Sherwood Midstream
Schedule of Equity Method Investments [Line Items]
Equity method investments	537		366
Midstream | MPLX | Whistler Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	134		0
Midstream | MPLX | Wink to Webster Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	126		0
Midstream | MPLX | Other equity method investees
Schedule of Equity Method Investments [Line Items]
Equity method investments	253		228
Midstream | Marathon Petroleum Corporation
Schedule of Equity Method Investments [Line Items]
Equity method investments	1,090		451
Midstream | Marathon Petroleum Corporation | LOOP
Schedule of Equity Method Investments [Line Items]
Equity method investments	59		56
Midstream | Marathon Petroleum Corporation | Capline LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	374		0
Midstream | Marathon Petroleum Corporation | Crowley Coastal Partners, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	188		190
Midstream | Marathon Petroleum Corporation | Gray Oak Pipeline LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	298		73
Midstream | Marathon Petroleum Corporation | Other equity method investees
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 171		$ 132
[1]	2018 represents our investment in three ethanol entities jointly owned with The Andersons, Inc. In 2019, these entities were contributed into a new legal entity, The Andersons Marathon Holdings, LLC.

Equity Method Investments (Summ

Equity Method Investments (Summarized Financial Information For Equity Method Investees) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income statement data:
Revenues and other income	$ 7,718	$ 7,726	$ 6,235
Income from operations	1,472	1,375	1,075
Net income	1,284	1,242	$ 922
Balance sheet data – December 31:
Current assets	1,333	1,443
Noncurrent assets	17,216	12,408
Current liabilities	1,006	1,857
Noncurrent liabilities	$ 2,772	$ 1,788

Equity Method Investments (Narr

Equity Method Investments (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Equity method investment difference between carrying amount and underlying equity	$ 1,400
Equity method investment difference between carrying amount and underlying equity, portion related to goodwill which is not being amortized	700
Dividends and partnership distributions received from equity method investees	$ 662	$ 519	$ 391

Property, Plant and Equipment_2

Property, Plant and Equipment (Summary Of Property, Plant And Equipment) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 64,623	$ 61,213
Accumulated depreciation	19,008	16,155
Net property, plant and equipment	45,615	45,058
Operating Segments | Refining & Marketing
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	29,037	27,590
Operating Segments | Retail
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	7,104	6,637
Operating Segments | Midstream
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	27,193	25,692
Corporate and Other
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 1,289	$ 1,294
Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives (in years)	2 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)	2 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) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 64,623	$ 61,213
Property, plant and equipment, accumulated depreciation	19,008	16,155
Assets held under capital leases
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	806	786
Property, plant and equipment, accumulated depreciation	226	202
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 3,480	$ 3,490

(Goodwill) (Details)

(Goodwill) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Finite-Lived Intangible Assets [Line Items]
Impairment	$ 1,197
Income Approach | Discount Rate | Minimum
Finite-Lived Intangible Assets [Line Items]
Fair value inputs	9.00%
Income Approach | Discount Rate | Maximum
Finite-Lived Intangible Assets [Line Items]
Fair value inputs	10.00%
Midstream
Finite-Lived Intangible Assets [Line Items]
Impairment	$ 1,197
Midstream | Prior to change in reporting units
Finite-Lived Intangible Assets [Line Items]
Impairment	1,156
Midstream | Subsequent to change in reporting units
Finite-Lived Intangible Assets [Line Items]
Impairment	$ 41

(Changes In Carrying Amount Of

(Changes In Carrying Amount Of Goodwill) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Line Items]
Beginning balance	$ 20,184	$ 3,586
Acquisitions	94	16,598
Dropdowns to MPLX		0
Purchase price allocation adjustments	976
Impairments	(1,197)
Dispositions	(17)
Ending balance	20,040	20,184
Refining & Marketing
Goodwill [Line Items]
Beginning balance	5,020	519
Acquisitions	38	4,717
Dropdowns to MPLX		(216)
Purchase price allocation adjustments	514
Impairments	0
Dispositions	0
Ending balance	5,572	5,020
Retail
Goodwill [Line Items]
Beginning balance	4,841	791
Acquisitions	56	4,050
Dropdowns to MPLX		0
Purchase price allocation adjustments	54
Impairments	0
Dispositions	0
Ending balance	4,951	4,841
Midstream
Goodwill [Line Items]
Beginning balance	10,323	2,276
Acquisitions	0	7,831
Dropdowns to MPLX		216
Purchase price allocation adjustments	408
Impairments	(1,197)
Dispositions	(17)
Ending balance	$ 9,517	$ 10,323

Goodwill and Intangibles (Intan

Goodwill and Intangibles (Intangible Assets by Major Class) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	$ 3,708	$ 3,711
Accumulated amortization	780	397
Net	2,928	3,314
Customer contracts and relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	3,273	3,184
Accumulated amortization	610	261
Net	2,663	2,923
Brand rights and tradenames
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	155	208
Accumulated amortization	55	33
Net	100	175
Royalty agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	133	129
Accumulated amortization	78	70
Net	55	59
Other intangible assets
Acquired Finite-Lived Intangible Assets [Line Items]
Gross	147	190
Accumulated amortization	37	33
Net	$ 110	$ 157

Goodwill and Intangibles (Int_2

Goodwill and Intangibles (Intangibles Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Indefinite-lived intangible assets	$ 94	$ 94
Amortization expense	$ 372	$ 134

Goodwill and Intangibles (Estim

Goodwill and Intangibles (Estimated Future Amortization Expense) (Details) $ in Millions	Dec. 31, 2019USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2020	$ 387
2021	380
2022	379
2023	363
2024	$ 305

Fair Value Measurements (Assets

Fair Value Measurements (Assets And Liabilities Accounted For At Fair Value On Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash collateral netted with derivative liabilities	$ 51	$ 13
Cash collateral netted with derivative assets		52
Fair Value, Measurements, Recurring | Commodity derivative instruments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - collateral and netting	(55)	(323)	[1]
Commodity derivative instruments, assets - net	8	78	[2]
Commodity derivative instruments, assets - collateral pledged not offset	73	2
Commodity derivative instruments, liabilities - netting and collateral	(106)	(284)	[1]
Commodity derivative instruments, liabilities, net	0	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	57	370
Commodity derivative instruments, liabilities - gross	95	255
Fair Value, Measurements, Recurring | Commodity derivative instruments | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, assets - gross	6	31
Commodity derivative instruments, liabilities - gross	11	37
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	0
Fair Value, Measurements, Recurring | Embedded derivative in commodity contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity derivative instruments, liabilities - netting and collateral	0	0	[1]
Commodity derivative instruments, liabilities, net	60	61	[2]
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	$ 60	$ 61
[1]	Represents the impact of netting assets, liabilities and cash collateral when a legal right of offset exists. As of December 31, 2019 , $51 million was netted with mark-to-market liabilities. 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 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) (Details)	12 Months Ended
	Dec. 31, 2019USD ($)
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	$ 0.43
Level 3 | Commodity derivative instruments | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward commodity price	$ 1.23
Level 3 | Embedded derivative in commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Probability of renewal	94.00%
Probability of renewal second term	83.00%

Fair Value Measurements (Reconc

Fair Value Measurements (Reconciliation Of Net Beginning And Ending Balances Recorded For Net Assets And Liabilities Classified As Level 3) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 61	$ 66
Unrealized and realized losses included in net income	5	3
Settlements of derivative instruments	(6)	(8)
Ending balance	$ 60	$ 61

Fair Value Measurements (Gains_

Fair Value Measurements (Gains/Losses Included In Earnings Relating to Assets Still Held at the End of Period) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
The amount of total losses for the period included in earnings attributable to the change in unrealized losses relating to assets still held at the end of period:	$ 5	$ 8

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Values - Reported) (Details) - USD ($) $ in Billions	Dec. 31, 2019	Dec. 31, 2018
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 28.3	$ 27
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 30.1	$ 26.5

Derivatives (Classification Of

Derivatives (Classification Of Gross Fair Values Of Derivative Instruments, Excluding Cash Collateral) (Details) - Commodity derivative instruments - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018
Other current assets
Derivatives, Fair Value [Line Items]
Asset		$ 63	$ 400
Liability		106	283
Other current liabilities(a)
Derivatives, Fair Value [Line Items]
Asset		0	1	[1]
Liability	[1]	5	16
Deferred credits and other liabilities
Derivatives, Fair Value [Line Items]
Asset		0	0	[1]
Liability	[1]	$ 55	$ 54
[1]	Includes embedded derivatives.

Derivatives (Open Commodity Der

Derivatives (Open Commodity Derivative Contracts) (Details) - Exchange Traded gal in Thousands, bbl in Thousands	12 Months Ended
	Dec. 31, 2019bblgal
Crude oil
Derivative [Line Items]
Percentage of derivative contracts expiring next quarter	85.70%
Crude oil | Long
Derivative [Line Items]
Notional contracts (contract volumes)	26,287	[1]
Crude oil | Long | Spread contracts
Derivative [Line Items]
Notional contracts (contract volumes)	5,130
Crude oil | Short
Derivative [Line Items]
Notional contracts (contract volumes) | gal	27,237	[1]
Crude oil | Short | Spread contracts
Derivative [Line Items]
Notional contracts (contract volumes)	330
Refined products
Derivative [Line Items]
Percentage of derivative contracts expiring next quarter	94.70%
Refined products | Long
Derivative [Line Items]
Notional contracts (contract volumes)	15,298	[1]
Refined products | Long | Spread contracts
Derivative [Line Items]
Notional contracts (contract volumes)	950
Refined products | Short
Derivative [Line Items]
Notional contracts (contract volumes) | gal	12,519	[1]
Blending products
Derivative [Line Items]
Percentage of derivative contracts expiring next quarter	99.50%
Blending products | Long
Derivative [Line Items]
Notional contracts (contract volumes)	1,976	[1]
Blending products | Short
Derivative [Line Items]
Notional contracts (contract volumes) | gal	3,770	[1]
[1]	Included in exchange-traded are spread contracts in thousands of barrels: Crude oil - 5,130 long and 330 short; Refined products - 950 long and 450 short

Derivatives (Effect Of Commodit

Derivatives (Effect Of Commodity Derivative Instruments In Statements Of Income) (Details) - Commodity derivative instruments - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	$ (96)	$ (46)	$ (21)
Sales and other operating revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	(19)	13	5
Cost of revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss)	$ (77)	$ (59)	$ (26)

Debt (Outstanding Borrowings) (

Debt (Outstanding Borrowings) (Details) - USD ($) $ in Millions		Dec. 31, 2019	Sep. 09, 2019	Dec. 31, 2018	Nov. 15, 2018	Oct. 02, 2018	Feb. 08, 2018
Debt Instrument [Line Items]
Finance lease obligations		$ 698		$ 649
Total debt		29,282		27,980
Unamortized debt issuance costs		(134)		(128)
Unamortized discount		(310)		(328)
Amounts due within one year		(711)		(544)
Total long-term debt due after one year		28,127		26,980
Marathon Petroleum Corporation
Debt Instrument [Line Items]
Notes payable		10		11
Marathon Petroleum Corporation | Senior Notes
Debt Instrument [Line Items]
Long-term debt outstanding		8,474		8,474		$ 2,905
Marathon Petroleum Corporation | Finance Lease
Debt Instrument [Line Items]
Finance lease obligations		679		629
MPLX | Senior Notes
Debt Instrument [Line Items]
Long-term debt outstanding		19,100	$ 2,000	13,850	$ 2,250		$ 5,500
MPLX | Line of Credit | Term loan facility
Debt Instrument [Line Items]
Long-term debt outstanding		1,000		0
MPLX | Finance Lease
Debt Instrument [Line Items]
Finance lease obligations		19		6
ANDX | Senior Notes
Debt Instrument [Line Items]
Long-term debt outstanding	[1]	0		3,750
ANDX | Line of Credit | Revolving and dropdown credit facilities
Debt Instrument [Line Items]
Long-term debt outstanding	[1]	0		1,245
ANDX | Finance Lease
Debt Instrument [Line Items]
Finance lease obligations	[1]	$ 0		$ 15
[1]	On July 30, 2019, MPLX acquired ANDX and assumed its debt obligations. See Note 4 and the discussion below for additional information.

Debt (MPC Senior Notes) (Detail

Debt (MPC Senior Notes) (Details) - USD ($) $ in Millions	Mar. 15, 2018	Dec. 31, 2019	Dec. 31, 2018	Oct. 02, 2018	Oct. 01, 2018
Andeavor
Debt Instrument [Line Items]
Long-term debt acquired					$ 8,876
Senior Notes | Andeavor
Debt Instrument [Line Items]
Long-term debt acquired					$ 3,374
Senior Notes | Andeavor | Andeavor senior notes, 3.800% - 5.375% due 2022 - 2048
Debt Instrument [Line Items]
Long-term debt outstanding				$ 469
Senior Notes | Marathon Petroleum Corporation
Debt Instrument [Line Items]
Long-term debt outstanding		$ 8,474	$ 8,474	$ 2,905
Senior Notes | Marathon Petroleum Corporation | Senior notes, 3.400% due December 2020
Debt Instrument [Line Items]
Long-term debt outstanding		650	650
Senior Notes | Marathon Petroleum Corporation | Senior notes, 5.125% due March 2021
Debt Instrument [Line Items]
Long-term debt outstanding		1,000	1,000
Senior Notes | Marathon Petroleum Corporation | Senior notes, 5.375% due October 2022
Debt Instrument [Line Items]
Long-term debt outstanding		337	337
Senior Notes | Marathon Petroleum Corporation | Senior notes, 4.750% due December 2023
Debt Instrument [Line Items]
Long-term debt outstanding		614	614
Senior Notes | Marathon Petroleum Corporation | Senior notes, 5.125% due April 2024
Debt Instrument [Line Items]
Long-term debt outstanding		241	241
Senior Notes | Marathon Petroleum Corporation | Senior notes, 3.625%, due September 2024
Debt Instrument [Line Items]
Long-term debt outstanding		750	750
Senior Notes | Marathon Petroleum Corporation | Senior notes, 5.125% due December 2026
Debt Instrument [Line Items]
Long-term debt outstanding		719	719
Senior Notes | Marathon Petroleum Corporation | Senior notes, 3.800% due April 2028
Debt Instrument [Line Items]
Long-term debt outstanding		496	496
Senior Notes | Marathon Petroleum Corporation | Senior notes, 6.500% due March 2041
Debt Instrument [Line Items]
Long-term debt outstanding		1,250	1,250
Senior Notes | Marathon Petroleum Corporation | Senior notes, 4.750% due September 2044
Debt Instrument [Line Items]
Long-term debt outstanding		800	800
Senior Notes | Marathon Petroleum Corporation | Senior notes, 5.850% due December 2045
Debt Instrument [Line Items]
Long-term debt outstanding		250	250
Senior Notes | Marathon Petroleum Corporation | Senior notes, 4.500% due April 2048
Debt Instrument [Line Items]
Long-term debt outstanding		498	498
Senior Notes | Marathon Petroleum Corporation | Senior notes, 5.000%, due September 2054
Debt Instrument [Line Items]
Long-term debt outstanding		400	400
Senior Notes | Marathon Petroleum Corporation | Senior notes, 2.700% due December 2018
Debt Instrument [Line Items]
Repayments of long-term debt	$ 600
Make whole premium	$ 2.5
Senior Notes | Marathon Petroleum Corporation | Andeavor | Andeavor senior notes, 3.800% - 5.375% due 2022 - 2048
Debt Instrument [Line Items]
Long-term debt outstanding		$ 469	$ 469

Debt (MPLX Term Loan) (Details)

Debt (MPLX Term Loan) (Details) - MPLX $ in Billions	Sep. 26, 2019USD ($)	Feb. 08, 2018USD ($)	Dec. 31, 2019USD ($)	Jan. 02, 2018USD ($)
Term loan facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 1
Debt instrument, description of variable rate basis	at either the Adjusted LIBO Rate (as defined in the term loan agreement) plus a margin or the Alternate Base Rate (as defined in the term loan agreement) plus a margin
Borrowings			$ 1
Weighted average interest rate			2.561%
Number of prior quarterly reporting periods covenant	4
Term loan facility | Maximum
Debt Instrument [Line Items]
Covenant ratio debt to EBITDA	5
Covenant ratio debt to EBITDA post acquisition	5.5
MPLX 364-day term loan
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity				$ 4.1
Repayments of short-term debt		$ 4.1

Debt (MPLX Senior Notes) (Detai

Debt (MPLX Senior Notes) (Details) - USD ($) $ in Millions	Dec. 10, 2018	Feb. 08, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Sep. 23, 2019	Sep. 09, 2019	Jul. 30, 2019	Nov. 15, 2018
Debt Instrument [Line Items]
Loss on extinguishment of debt			$ 0	$ (64)	$ 0
Senior Notes | ANDX
Debt Instrument [Line Items]
Long-term debt outstanding						$ 690
Senior Notes | Senior notes, 5.500%, due October 2019 | ANDX
Debt Instrument [Line Items]
Long-term debt outstanding						500
Repayments of long-term debt			500
Interest costs incurred			14
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	$ 19,100	13,850			$ 2,000		$ 2,250
MPLX | Senior Notes | MPLX
Debt Instrument [Line Items]
Long-term debt outstanding						$ 3,060
MPLX | Senior Notes | Floating rate senior notes due September 2021
Debt Instrument [Line Items]
Interest rate, effective percentage			2.948%
Long-term debt outstanding			$ 1,000	0			1,000
MPLX | Senior Notes | Floating rate senior notes due September 2022
Debt Instrument [Line Items]
Interest rate, effective percentage			3.148%
Long-term debt outstanding			$ 1,000	0			$ 1,000
MPLX | Senior Notes | Senior notes, 6.250% due October 2022
Debt Instrument [Line Items]
Long-term debt outstanding			266	0
MPLX | Senior Notes | Senior notes, 3.500% due December 2022
Debt Instrument [Line Items]
Long-term debt outstanding			486	0
MPLX | Senior Notes | Senior notes, 3.375% due March 2023
Debt Instrument [Line Items]
Long-term debt outstanding			500	500
MPLX | Senior Notes | Senior notes, 4.500% due July 2023
Debt Instrument [Line Items]
Long-term debt outstanding			989	989
MPLX | Senior Notes | Senior notes, 6.375% due May 2024
Debt Instrument [Line Items]
Long-term debt outstanding			381	0
MPLX | Senior Notes | Senior notes, 4.875% due December 2024
Debt Instrument [Line Items]
Long-term debt outstanding			1,149	1,149
MPLX | Senior Notes | Senior notes, 5.250% due January 2025
Debt Instrument [Line Items]
Long-term debt outstanding			708	0
MPLX | Senior Notes | Senior notes, 4.000% due February 2025
Debt Instrument [Line Items]
Long-term debt outstanding			500	500
MPLX | Senior Notes | Senior notes, 4.875% due June 2025
Debt Instrument [Line Items]
Long-term debt outstanding			1,189	1,189
MPLX | Senior Notes | Senior notes, 4.125% due March 2027
Debt Instrument [Line Items]
Long-term debt outstanding			1,250	1,250
MPLX | Senior Notes | Senior notes, 4.250% due December 2027
Debt Instrument [Line Items]
Long-term debt outstanding			732	0
MPLX | Senior Notes | Senior notes, 4.000% due March 2028
Debt Instrument [Line Items]
Long-term debt outstanding			1,250	1,250
MPLX | Senior Notes | Senior notes, 4.800% due February 2029
Debt Instrument [Line Items]
Long-term debt outstanding			750	750
MPLX | Senior Notes | Senior notes, 4.500% due April 2038
Debt Instrument [Line Items]
Long-term debt outstanding			1,750	1,750
MPLX | Senior Notes | Senior notes, 5.200% due March 2047
Debt Instrument [Line Items]
Long-term debt outstanding			1,000	1,000
MPLX | Senior Notes | Senior notes, 5.200% due December 2047
Debt Instrument [Line Items]
Long-term debt outstanding			487	0
MPLX | Senior Notes | Senior notes, 4.700% due April 2048
Debt Instrument [Line Items]
Long-term debt outstanding			1,500	1,500
MPLX | Senior Notes | Senior notes, 5.500% due February 2049
Debt Instrument [Line Items]
Long-term debt outstanding			1,500	1,500
MPLX | Senior Notes | Senior notes, 4.900% due April 2058
Debt Instrument [Line Items]
Long-term debt outstanding			500	500
MPLX | Senior Notes | Senior notes, 5.500%, due February 2023
Debt Instrument [Line Items]
Repayments of long-term debt	$ 750
Redemption price, percentage	101.833%
Loss on extinguishment of debt	$ 60
MPLX | Senior Notes | MarkWest | MarkWest senior notes, 4.500% - 5.500% due 2023 - 2025
Debt Instrument [Line Items]
Long-term debt outstanding			23	23
MPLX | Senior Notes | ANDX
Debt Instrument [Line Items]
Long-term debt acquired								$ 3,750
MPLX | Senior Notes | ANDX | ANDX senior notes, 3.500% - 6.375% due 2019 - 2047
Debt Instrument [Line Items]
Long-term debt outstanding			$ 190	$ 0

Debt (Schedule Of Debt Payments

Debt (Schedule Of Debt Payments) (Details) $ in Millions	Dec. 31, 2019USD ($)
Debt Disclosure [Abstract]
2020	$ 650
2021	3,008
2022	2,275
2023	2,350
2024	$ 2,652

Debt (Available Capacity under

Debt (Available Capacity under our Facilities) (Details) $ in Millions	Dec. 31, 2019USD ($)
MPC 364-day bank revolving credit facility
Line of Credit Facility [Line Items]
Total Capacity	$ 1,000
Outstanding Borrowings	0
Outstanding Letters of Credit	0
Available Capacity	$ 1,000
Weighted Average Interest Rate	0.00%
MPC bank revolving credit facility
Line of Credit Facility [Line Items]
Total Capacity	$ 5,000
Outstanding Borrowings	0
Outstanding Letters of Credit	1
Available Capacity	$ 4,999
Weighted Average Interest Rate	0.00%
MPC trade receivables securitization facility
Line of Credit Facility [Line Items]
Total Capacity	$ 750
Outstanding Borrowings	0
Outstanding Letters of Credit	0
Available Capacity	$ 750
Weighted Average Interest Rate	0.00%
MPLX bank revolving credit facility
Line of Credit Facility [Line Items]
Total Capacity	$ 3,500
Outstanding Borrowings	0
Outstanding Letters of Credit	0
Available Capacity	$ 3,500
Weighted Average Interest Rate	0.00%

Debt (Commercial Paper) (Detail

Debt (Commercial Paper) (Details) - USD ($) $ in Thousands	Feb. 26, 2016	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Commercial paper – issued		$ 0	$ 0	$ 300,000
Commercial paper - repayments		0	$ 0	$ 300,000
Commercial paper outstanding		$ 0
Commercial Paper
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 2,000,000
Debt instrument, term	397 days

Debt (MPC Revolving Credit Agre

Debt (MPC Revolving Credit Agreements) (Details) $ in Millions	Oct. 01, 2018USD ($)Period	Dec. 31, 2019USD ($)	Jul. 26, 2019USD ($)
MPC 364-day bank revolving credit facility
Line of Credit Facility [Line Items]
Total capacity		$ 1,000
Marathon Petroleum Corporation | Bank revolving credit facility due October 2023
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 5,000
Number of renewal periods | Period	2
Marathon Petroleum Corporation | Bank revolving credit facility due October 2023 | Letter of Credit
Line of Credit Facility [Line Items]
Total capacity	$ 2,200
Marathon Petroleum Corporation | Bank revolving credit facility due October 2023 | Maximum
Line of Credit Facility [Line Items]
Line of credit facility additional borrowing capacity	1,000
Marathon Petroleum Corporation | Bank revolving credit facility due October 2023 | Maximum | Bridge Loan
Line of Credit Facility [Line Items]
Total capacity	250
Marathon Petroleum Corporation | Bank revolving credit facility due October 2023 | Maximum | Letter of Credit
Line of Credit Facility [Line Items]
Total capacity	3,000
Marathon Petroleum Corporation | MPC 364-Day Revolver due September 2020 [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity			$ 1,000
Marathon Petroleum Corporation | MPC 364-day bank revolving credit facility
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 1,000
Marathon Petroleum Corporation | MPC bank revolving credit facilities
Line of Credit Facility [Line Items]
Debt instrument, description of variable rate basis	at either the Adjusted LIBO Rate or the Alternate Base Rate (both as defined in the MPC credit agreements), plus an applicable margin
Marathon Petroleum Corporation | MPC bank revolving credit facilities | Maximum
Line of Credit Facility [Line Items]
Ratio of indebtedness to net capital	0.65

Debt (Trade Receivables Securit

Debt (Trade Receivables Securitization Facility) (Details) - MPC trade receivables securitization facility $ in Millions	Jul. 20, 2016USD ($)
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 750
Letter of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 750

Debt (MPLX Credit Agreement) (D

Debt (MPLX Credit Agreement) (Details) - MPLX - MPLX revolving credit facility due July 2024 [Member] $ in Millions	Jul. 30, 2019USD ($)
Debt Instrument [Line Items]
Total capacity	$ 3,500
Debt instrument, description of variable rate basis	at the Adjusted LIBO Rate or the Alternate Base Rate (both as defined in the MPLX credit agreement) plus an applicable margin
Maximum
Debt Instrument [Line Items]
Line of credit facility additional borrowing capacity	$ 1,000
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 | Maximum
Debt Instrument [Line Items]
Total capacity	$ 300
Bridge Loan | Maximum
Debt Instrument [Line Items]
Total capacity	$ 150

Revenue (Disaggregated by Segme

Revenue (Disaggregated by Segment and Product Line) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Sales and other operating revenues, excluding consumer excise taxes		$ 123,949	$ 96,504
Sales and other operating revenue, including excise taxes				$ 74,733
Refined products
Sales and other operating revenues, excluding consumer excise taxes		109,659	85,082
Sales and other operating revenue, including excise taxes				65,195
Merchandise
Sales and other operating revenues, excluding consumer excise taxes		6,285	5,238
Sales and other operating revenue, including excise taxes				4,897
Crude oil
Sales and other operating revenues, excluding consumer excise taxes		4,402	3,345
Sales and other operating revenue, including excise taxes				2,862
Midstream services and other
Sales and other operating revenues, excluding consumer excise taxes		3,603	2,839
Sales and other operating revenue, including excise taxes				1,779
Refining & Marketing
Sales and other operating revenues, excluding consumer excise taxes		87,056	69,685
Sales and other operating revenue, including excise taxes	[1]			53,382
Refining & Marketing | Refined products
Sales and other operating revenues, excluding consumer excise taxes		82,169	65,916
Sales and other operating revenue, including excise taxes				50,193
Refining & Marketing | Merchandise
Sales and other operating revenues, excluding consumer excise taxes		4	11
Sales and other operating revenue, including excise taxes				4
Refining & Marketing | Crude oil
Sales and other operating revenues, excluding consumer excise taxes		4,402	3,345
Sales and other operating revenue, including excise taxes				2,862
Refining & Marketing | Midstream services and other
Sales and other operating revenues, excluding consumer excise taxes		481	413
Sales and other operating revenue, including excise taxes				323
Retail
Sales and other operating revenues, excluding consumer excise taxes		33,059	23,546
Sales and other operating revenue, including excise taxes	[1]			19,029
Retail | Refined products
Sales and other operating revenues, excluding consumer excise taxes		26,681	18,279
Sales and other operating revenue, including excise taxes				14,113
Retail | Merchandise
Sales and other operating revenues, excluding consumer excise taxes		6,281	5,227
Sales and other operating revenue, including excise taxes				4,893
Retail | Crude oil
Sales and other operating revenues, excluding consumer excise taxes		0	0
Sales and other operating revenue, including excise taxes				0
Retail | Midstream services and other
Sales and other operating revenues, excluding consumer excise taxes		97	40
Sales and other operating revenue, including excise taxes				23
Midstream
Sales and other operating revenues, excluding consumer excise taxes		3,834	3,273
Sales and other operating revenue, including excise taxes	[1]			2,322
Midstream | Refined products
Sales and other operating revenues, excluding consumer excise taxes		809	887
Sales and other operating revenue, including excise taxes				889
Midstream | Merchandise
Sales and other operating revenues, excluding consumer excise taxes		0	0
Sales and other operating revenue, including excise taxes				0
Midstream | Crude oil
Sales and other operating revenues, excluding consumer excise taxes		0	0
Sales and other operating revenue, including excise taxes				0
Midstream | Midstream services and other
Sales and other operating revenues, excluding consumer excise taxes		$ 3,025	$ 2,386
Sales and other operating revenue, including excise taxes				$ 1,433
[1]	Includes related party sales. See Note 7 for additional information.

Revenue (Receivables) (Details)

Revenue (Receivables) (Details) $ in Millions	Dec. 31, 2019USD ($)
Revenue from Contract with Customer [Abstract]
Matching buy/sell receivables	$ 2,240

Supplemental Cash Flow Inform_3

Supplemental Cash Flow Information (Summary Of Supplemental Cash Flow Information) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Net cash provided by operating activities included:
Interest paid (net of amounts capitalized)	$ 1,174		$ 887	$ 525
Net income taxes paid to taxing authorities	491		424	904
Payments on operating leases	764	[1]	0	0
Interest payments under finance lease obligations	34	[1]	0	0
Net cash provided by financing activities included:
Principal payments under finance lease obligations	55	[1]	0	0
Non-cash investing and financing activities:
Capital leases	0		172	71
Right of use assets obtained in exchange for new operating lease obligations	352	[1]	0	0
Right of use assets obtained in exchange for new finance lease obligations	96	[1]	0	0
Contribution of assets	266	[2]	0	337	[2]
Fair value of asset acquired	525	[3]	0	45	[3]
Acquisition:
Fair value of MPC shares issued	0		19,766	0
Fair value of converted equity awards	$ 0		$ 203	$ 0
[1]	Disclosure added in 2019 following the adoption of ASC 842.
[2]	2019 includes the contribution of net assets to The Andersons Marathon Holdings LLC and Capline LLC. See Note 14 . 2017 includes MPLX’s contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. See Note 5 .
[3]	2019 includes the recognition of The Andersons Marathon Holdings LLC and Capline LLC equity method investments. See Note 14 . 2017 represents emission allowance credits received as part of a litigation settlement agreement.

Supplemental Cash Flow Inform_4

Supplemental Cash Flow Information (Change in Cash and Cash Equivalents) (Details) - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Cash Flow Elements [Abstract]
Cash and cash equivalents		$ 1,527	$ 1,687
Restricted cash	[1]	2	38
Cash, cash equivalents and restricted cash		$ 1,529	$ 1,725	$ 3,015	$ 892
[1]	The restricted cash balance is included within other current assets on the consolidated balance sheets.

Supplemental Cash Flow Inform_5

Supplemental Cash Flow Information (Reconciliation Of Additions To Property, Plant And Equipment To Total Capital Expenditures) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Supplemental Cash Flow Information [Abstract]
Additions to property, plant and equipment per the consolidated statements of cash flows		$ 5,374	$ 3,578	$ 2,732
Asset retirement expenditures		1	8	2
Increase (decrease) in capital accruals		(306)	309	67
Total capital expenditures	[1]	$ 5,069	$ 3,895	$ 2,801
[1]	ncludes changes in capital expenditure accruals. See Note 21 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, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		$ (144)	$ (231)
Other comprehensive income (loss) before reclassifications, net of tax of ($52)		(162)	49
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit		(45)	(36)
Amortization– actuarial loss		21	30
Amortization– settlement loss		9	53
Other		(5)	(5)
Tax effect		6	(4)
Other comprehensive income (loss)		(176)	87	$ 3
Ending balance		(320)	(144)	(231)
Other comprehensive income (loss) before reclassifications, tax		(52)	23
Pension Benefits
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit		(45)	(33)	(39)
Other Benefits
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit		0	(3)	(3)
Accumulated Defined Benefit Plans Adjustment | Pension Benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(132)	(190)
Other comprehensive income (loss) before reclassifications, net of tax of ($52)		(71)	14
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit	[1]	(45)	(33)
Amortization– actuarial loss	[1]	22	31
Amortization– settlement loss	[1]	9	53
Tax effect		5	(7)
Other comprehensive income (loss)		(80)	58
Ending balance		(212)	(132)	(190)
Accumulated Defined Benefit Plans Adjustment | Other Benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(23)	(48)
Other comprehensive income (loss) before reclassifications, net of tax of ($52)		(92)	27
Amounts reclassified from accumulated other comprehensive loss:
Amortization - prior service credit	[1]	0	(3)
Amortization– actuarial loss	[1]	(1)	(1)
Amortization– settlement loss	[1]	0	0
Tax effect		0	2
Other comprehensive income (loss)		(93)	25
Ending balance		(116)	(23)	(48)
Gain on Cash Flow Hedge
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		2	4
Other comprehensive income (loss) before reclassifications, net of tax of ($52)		0	(1)
Amounts reclassified from accumulated other comprehensive loss:
Reclassified to earnings, net		(1)
Tax effect		0	(1)
Other comprehensive income (loss)		(1)	(2)
Ending balance		1	2	4
Workers Compensation
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		9	3
Other comprehensive income (loss) before reclassifications, net of tax of ($52)		1	9
Amounts reclassified from accumulated other comprehensive loss:
Other		(4)	(5)
Tax effect		1	2
Other comprehensive income (loss)		(2)	6
Ending balance		$ 7	$ 9	$ 3
[1]	These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See Note 23 .

Pension and Other Postretirem_3

Pension and Other Postretirement Benefits (Summary Of Defined Benefit Plans With Accumulated Benefit Obligations In Excess Of Plan Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Projected benefit obligations	$ 3,239	$ 2,779
Accumulated benefit obligations	3,031	2,632
Fair value of plan assets	$ 2,531	$ 2,089

Pension and Other Postretirem_4

Pension and Other Postretirement Benefits (Summary Of Projected Benefit Obligations And Funded Status For Defined Benefit Pension And Other Postretirement Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Change in plan assets:
Fair value of plan assets at January 1	$ 2,089
Fair value of plan assets at December 31	2,531		$ 2,089
Amounts recognized in the consolidated balance sheets:
Noncurrent liabilities	(1,643)		(1,509)
Pension Benefits
Change in benefit obligations:
Benefit obligations at January 1	2,779		2,164
Service cost	234		159	$ 132
Interest cost	108		83	75
Actuarial (gain) loss	401		(159)
Benefits paid	(283)		(273)
Plan amendments	0		(90)
Acquisitions	0		895
Benefit obligations at December 31	3,239		2,779	2,164
Change in plan assets:
Fair value of plan assets at January 1	2,089		1,840
Actual return on plan assets	436		(115)
Employer contributions	289		115
Benefits paid from plan assets	(283)		(273)
Acquisitions	0		522
Fair value of plan assets at December 31	2,531		2,089	1,840
Funded status of plans at December 31	(708)		(690)
Amounts recognized in the consolidated balance sheets:
Current liabilities	(49)		(21)
Noncurrent liabilities	(659)		(669)
Accrued benefit cost	(708)		(690)
Pretax amounts recognized in accumulated other comprehensive loss:
Net actuarial loss	579	[1]	517
Prior service cost (credit)	(250)	[1]	(295)
Pension Benefits | LOOP LLC and Explorer Pipeline
Pretax amounts recognized in accumulated other comprehensive loss:
Net actuarial loss	17
Other Benefits
Change in benefit obligations:
Benefit obligations at January 1	884		826
Service cost	31		30	25
Interest cost	37		30	30
Actuarial (gain) loss	125		(71)
Benefits paid	(45)		(36)
Plan amendments	(1)		34
Acquisitions	0		71
Benefit obligations at December 31	1,031		884	826
Change in plan assets:
Fair value of plan assets at January 1	0		0
Actual return on plan assets	0		0
Employer contributions	45		36
Benefits paid from plan assets	(45)		(36)
Acquisitions	0		0
Fair value of plan assets at December 31	0		0	$ 0
Funded status of plans at December 31	(1,031)		(884)
Amounts recognized in the consolidated balance sheets:
Current liabilities	(47)		(44)
Noncurrent liabilities	(984)		(840)
Accrued benefit cost	(1,031)		(884)
Pretax amounts recognized in accumulated other comprehensive loss:
Net actuarial loss	135	[1]	9
Prior service cost (credit)	33	[1]	$ 35
Other Benefits | LOOP LLC and Explorer Pipeline
Pretax amounts recognized in accumulated other comprehensive loss:
Net actuarial loss	$ 1
[1]	Amounts exclude those related to LOOP and Explorer, equity method investees with defined benefit pension and postretirement plans for which net losses of $17 million and less than $1 million were recorded in accumulated other comprehensive loss in 2019 , reflecting our ownership share.

Pension and Other Postretirem_5

Pension and Other Postretirement Benefits (Components Of Net Periodic Benefit Cost And Other Comprehensive Loss) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax):
Amortization of prior service credit		$ 45	$ 36
Pension Benefits
Components of net periodic benefit cost:
Service cost		234	159	$ 132
Interest cost		108	83	75
Expected return on plan assets		(127)	(109)	(100)
Amortization – prior service credit		(45)	(33)	(39)
Amortization – actuarial loss		22	31	36
Amortization – settlement loss		9	53	52
Net periodic benefit cost	[1]	201	184	156
Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax):
Actuarial (gain) loss		93	64	(20)
Prior service cost (credit)		0	(90)	0
Amortization of actuarial gain (loss)		(31)	(84)	(88)
Amortization of prior service credit		45	33	39
Total recognized in other comprehensive loss		107	(77)	(69)
Total recognized in net periodic benefit cost and other comprehensive loss		308	107	87
Estimated net gain (loss) that will be amortized from accumulated other comprehensive loss in 2020		(33)
Estimated prior service cost (credit) that will be amortized from accumulated other comprehensive loss in 2020		(45)
Other Benefits
Components of net periodic benefit cost:
Service cost		31	30	25
Interest cost		37	30	30
Expected return on plan assets		0	0	0
Amortization – prior service credit		0	(3)	(3)
Amortization – actuarial loss		(1)	(1)	(2)
Amortization – settlement loss		0	0	0
Net periodic benefit cost	[1]	67	56	50
Other changes in plan assets and benefit obligations recognized in other comprehensive loss (pretax):
Actuarial (gain) loss		125	(71)	61
Prior service cost (credit)		(1)	34	0
Amortization of actuarial gain (loss)		1	1	2
Amortization of prior service credit		0	3	3
Total recognized in other comprehensive loss		125	(33)	66
Total recognized in net periodic benefit cost and other comprehensive loss		192	$ 23	$ 116
Estimated net gain (loss) that will be amortized from accumulated other comprehensive loss in 2020		(3)
Estimated prior service cost (credit) that will be amortized from accumulated other comprehensive loss in 2020		$ 1
[1]	Net periodic benefit cost reflects a calculated market-related value of plan assets which recognizes changes in fair value over three years.

Pension and Other Postretirem_6

Pension and Other Postretirement Benefits (Summary Of Assumptions Used To Determine Benefit Obligations And Net Periodic Benefit Cost) (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits
Weighted-average assumptions used to determine benefit obligation:
Discount rate	3.03%	4.21%	3.55%
Rate of compensation increase	4.90%	5.00%	5.00%
Weighted-average assumptions used to determine net periodic benefit cost:
Discount rate	4.05%	3.88%	3.85%
Expected long-term return on plan assets	6.00%	6.15%	6.50%
Rate of compensation increase	4.90%	4.80%	5.00%
Other Benefits
Weighted-average assumptions used to determine benefit obligation:
Discount rate	3.00%	4.26%	3.70%
Rate of compensation increase	4.90%	5.00%	5.00%
Weighted-average assumptions used to determine net periodic benefit cost:
Discount rate	4.30%	3.72%	4.25%
Expected long-term return on plan assets	0.00%	0.00%	0.00%
Rate of compensation increase	4.90%	5.00%	5.00%

Pension and Other Postretirem_7

Pension and Other Postretirement Benefits (Expected Long-Term Return on Plan Assets) (Details)	12 Months Ended
	Dec. 31, 2019
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

Pension and Other Postretirem_8

Pension and Other Postretirement Benefits (Summarizes Assumed Health Care Cost Trend Rates) (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Medical Pre-65
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for the following year:	6.20%	6.80%	6.75%
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:	2027	2027	2026
Prescription drugs
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for the following year:	8.10%	9.50%	8.75%
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:	2027	2027	2026
Medical Post-65 | Maximum
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for the following year:	4.00%

Pension and Other Postretirem_9

Pension and Other Postretirement Benefits (Effects Of One Percentage Point Change In Assumed Health Care Cost Trend Rates) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Effect on total of service and interest cost components, 1-Percentage-Point-Increase	$ 6
Effect on other postretirement benefit obligations, 1-Percentage-Point-Increase	52
Effect on total of service and interest cost components, 1-Percentage-Point Decrease	(5)
Effect on other postretirement benefit obligations, 1-Percentage-Point-Decrease	$ (45)

Pension and Other Postretire_10

Pension and Other Postretirement Benefits (Plan Investment Policies And Strategies) (Details)	12 Months Ended
	Dec. 31, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, investment goals	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.
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%

Pension and Other Postretire_11

Pension and Other Postretirement Benefits (Fair Values Of Defined Benefit Pension Plan Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	$ 2,531	$ 2,089
Level 1
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	644	567
Level 2
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	1,814	1,434
Level 3
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	73	88	$ 105
Cash and cash equivalents
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	22	25
Cash and cash equivalents | Level 1
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	0	0
Cash and cash equivalents | Level 2
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	22	25
Cash and cash equivalents | Level 3
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	0	0
Common stocks
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	260	175
Common stocks | Level 1
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	125	89
Common stocks | Level 2
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	135	86
Common stocks | Level 3
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	0	0
Mutual funds
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	188	159
Mutual funds | Level 1
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	188	159
Mutual funds | Level 2
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	0	0
Mutual funds | Level 3
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	0	0
Pooled funds
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	442	297
Pooled funds | Level 1
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	0	0
Pooled funds | Level 2
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	442	297
Pooled funds | Level 3
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	0	0
Corporate
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	975	860
Corporate | Level 1
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	160	176
Corporate | Level 2
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	815	684
Corporate | Level 3
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	0	0
Government
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	330	239
Government | Level 1
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	113	98
Government | Level 2
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	217	141
Government | Level 3
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	0	0
Pooled funds
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	229	201
Pooled funds | Level 1
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	0	0
Pooled funds | Level 2
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	229	201
Pooled funds | Level 3
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	0	0
Private equity
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	30	41
Private equity | Level 1
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	0	0
Private equity | Level 2
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	0	0
Private equity | Level 3
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	30	41	51
Real estate
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	24	29
Real estate | Level 1
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	0	0
Real estate | Level 2
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	0	0
Real estate | Level 3
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	24	29	$ 34
Other
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	31	63
Other | Level 1
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	58	45
Other | Level 2
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	(46)	0
Other | Level 3
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Plan asset investments, at fair value	$ 19	$ 18

Pension and Other Postretire_12

Pension and Other Postretirement Benefits (Reconciliation Of Beginning And Ending Balances Of Plan Assets Classified As Level 3) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Plan Assets, Level 3 Reconciliation [Line Items]
Fair value of plan assets at January 1	$ 2,089
Actual return on plan assets:
Fair value of plan assets at December 31	2,531	$ 2,089
Private equity
Defined Benefit Plan, Plan Assets, Level 3 Reconciliation [Line Items]
Fair value of plan assets at January 1	41
Actual return on plan assets:
Fair value of plan assets at December 31	30	41
Real estate
Defined Benefit Plan, Plan Assets, Level 3 Reconciliation [Line Items]
Fair value of plan assets at January 1	29
Actual return on plan assets:
Fair value of plan assets at December 31	24	29
Level 3
Defined Benefit Plan, Plan Assets, Level 3 Reconciliation [Line Items]
Fair value of plan assets at January 1	88	105
Actual return on plan assets:
Realized	7	11
Unrealized	(4)	1
Purchases	2	2
Sales	(20)	(31)
Fair value of plan assets at December 31	73	88
Level 3 | Private equity
Defined Benefit Plan, Plan Assets, Level 3 Reconciliation [Line Items]
Fair value of plan assets at January 1	41	51
Actual return on plan assets:
Realized	5	9
Unrealized	(3)	2
Purchases	1	1
Sales	(14)	(22)
Fair value of plan assets at December 31	30	41
Level 3 | Real estate
Defined Benefit Plan, Plan Assets, Level 3 Reconciliation [Line Items]
Fair value of plan assets at January 1	29	34
Actual return on plan assets:
Realized	2	2
Unrealized	(2)	(1)
Purchases	1	1
Sales	(6)	(7)
Fair value of plan assets at December 31	24	29
Level 3 | Other
Defined Benefit Plan, Plan Assets, Level 3 Reconciliation [Line Items]
Fair value of plan assets at January 1	18	20
Actual return on plan assets:
Realized	0	0
Unrealized	1	0
Purchases	0	0
Sales	0	(2)
Fair value of plan assets at December 31	$ 19	$ 18

Pension and Other Postretire_13

Pension and Other Postretirement Benefits (Contributions To Defined Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions to defined contribution plans	$ 217	$ 144	$ 116
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension contributions	270
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	49
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	$ 47

Pension and Other Postretire_14

Pension and Other Postretirement Benefits (Estimated Future Benefit Payments) (Details) $ in Millions	Dec. 31, 2019USD ($)
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
2020	$ 248
2021	216
2022	218
2023	220
2024	233
2025 through 2029	1,187
Other Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
2020	47
2021	49
2022	50
2023	51
2024	52
2025 through 2029	$ 283

Pension and Other Postretire_15

Pension and Other Postretirement Benefits (Multi Employee Plans) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)Plan	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
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%
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	$ 6	$ 7

Pension and Other Postretire_16

Pension and Other Postretirement Benefits (Multi Employer Pension Plan) (Details)	12 Months Ended
	Dec. 31, 2019USD ($)Employee		Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Multiemployer Plans [Line Items]
Pension Protection Act zone status	Red		Red
Funding improvement plan and rehabilitation plan	Implemented
Surcharge - imposed	No
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	263
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 2020 . A total of 263 employees participated in the plan as of December 31, 2019 .

Stock-Based Compensation (Narra

Stock-Based Compensation (Narrative) (Details) shares in Millions	12 Months Ended
	Dec. 31, 2019$ / 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 (Stock

Stock-Based Compensation (Stock-Based Compensation Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Payment Arrangement [Abstract]
Stock-based compensation expense	$ 161	$ 133	$ 51
Tax benefit recognized on stock-based compensation expense	37	32	19
Cash received by MPC upon exercise of stock option awards	10	24	46
Tax (expense)/benefit received for tax deductions for stock awards exercised	$ (3)	$ 14	$ 25

Stock-Based Compensation (Weigh

Stock-Based Compensation (Weighted Average Assumptions Used To Value Stock Options Awards) (Details) - Stock Options - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average exercise price per share	$ 61.92	$ 67.71	$ 50.57
Expected life in years	6 years	6 years 2 months 12 days	6 years 3 months 18 days
Expected volatility	32.00%	34.00%	35.00%
Expected dividend yield	3.40%	3.00%	3.00%
Risk-free interest rate	2.40%	2.70%	2.10%
Weighted average grant date fair value of stock option awards granted	$ 13.65	$ 17.21	$ 13.42
Implied volatility rate weighting (in percentage)	50.00%
Historical volatility rate weighting (in percentage)	50.00%

Stock-Based Compensation (Summa

Stock-Based Compensation (Summary Of Stock Option Award Activity) (Details) - Stock Options - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of options exercised	$ 23	$ 44	$ 75
Unrecognized compensation cost	$ 14
Weighted average recognition period, in years	1 year 4 months 24 days
Number of Shares
Outstanding, beginning balance	8,724,595
Granted	1,952,324
Exercised	(529,706)
Forfeited or expired	(128,846)
Outstanding, ending balance	10,018,367	8,724,595
Vested and expected to vest at December 31, 2019 (in shares)	9,987,326
Exercisable at December 31, 2019 (in shares)	7,404,952
Weighted Average Exercise Price
Outstanding, beginning balance (in USD per share)	$ 37.07
Granted (in USD per share)	61.92	$ 67.71	$ 50.57
Exercised (in USD per share)	19.12
Forfeited or expired (in USD per share)	61.29
Outstanding, ending balance (in USD per share)	42.55	$ 37.07
Vested and expected to vest at December 31, 2019 (in USD per share)	26.84
Exercisable at December 31, 2019 (in USD per share)	$ 35.85
Weighted Average Remaining Contractual Terms (in years)
Vested and expected to vest at December 31, 2019 (in years)	5 years 2 months 12 days
Exercisable at December 31, 2019 (in years)	4 years
Aggregate Intrinsic Value (in millions)
Vested and expected to vest at December 31, 2019 (in USD)	$ 187
Exercisable at December 31, 2019 (in USD)	$ 183

Stock-Based Compensation (Sum_2

Stock-Based Compensation (Summary Of Restricted Stock Award Activity) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restricted Stock
Number of Shares
Unvested, beginning balance	989,019
Granted	1,059,837
Vested	(595,440)
Forfeited	(103,618)
Unvested, ending balance	1,349,798	989,019
Weighted Average Grant Date Fair Value
Unvested, beginning balance (in USD per share)	$ 57.19
Granted (in USD per share)	61.14	$ 71.19	$ 50.25
Vested (in USD per share)	52.16
Forfeited (in USD per share)	61.20
Unvested, ending balance (in USD per share)	$ 62.20	$ 57.19
Restricted Stock Units
Number of Shares
Unvested, beginning balance	3,120,116
Granted	36,391
Vested	(1,527,145)
Forfeited	(147,616)
Unvested, ending balance	1,481,746	3,120,116
Weighted Average Grant Date Fair Value
Unvested, beginning balance (in USD per share)	$ 82.40
Granted (in USD per share)	58.30	$ 72.43	$ 53.19
Vested (in USD per share)	81.84
Forfeited (in USD per share)	82.37
Unvested, ending balance (in USD per share)	$ 82.39	$ 82.40

Stock-Based Compensation (Sum_3

Stock-Based Compensation (Summary Of Values Related To Vested And Unvested Restricted Stock Awards) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic Value of Awards Vested During the Period (in millions)	$ 32	$ 49	$ 28
Weighted Average Grant Date Fair Value of Awards Granted During the Period	$ 61.14	$ 71.19	$ 50.25
Unrecognized compensation cost	$ 56
Weighted average recognition period, in years	1 year 5 months 15 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)	$ 120	$ 39	$ 5
Weighted Average Grant Date Fair Value of Awards Granted During the Period	$ 58.30	$ 72.43	$ 53.19
Unrecognized compensation cost	$ 28
Weighted average recognition period, in years	7 months 28 days

Stock-Based Compensation (Sum_4

Stock-Based Compensation (Summary Of Performance Unit Awards) (Details) - Performance Unit Awards - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued in period	206,216
Unrecognized compensation cost	$ 2
Weighted average recognition period, in years	9 months 25 days
Number of Shares
Unvested, beginning balance	8,607,250
Granted	6,256,250
Vested	(3,494,000)
Forfeited	(170,000)
Unvested, ending balance	11,199,500	8,607,250
Weighted Average Grant Date Fair Value
Unvested, beginning balance (in USD per share)	$ 0.79
Granted (in USD per share)	0.72	$ 0.83	$ 0.92
Vested (in USD per share)	0.62
Canceled (in USD per share)	0.81
Unvested, ending balance (in USD per share)	$ 0.80	$ 0.79

Stock-Based Compensation (Wei_2

Stock-Based Compensation (Weighted Average Assumptions Used to Value Performance Unit Awards) (Details) - Performance Unit Awards - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.50%	2.30%	1.50%
Look-back period (in years)	2 years 9 months 18 days	2 years 9 months 18 days	2 years 9 months 18 days
Expected volatility	29.70%	34.00%	36.10%
Grant date fair value of performance units granted	$ 0.72	$ 0.83	$ 0.92

Leases (Lessee Narrative) (Deta

Leases (Lessee Narrative) (Details)	12 Months Ended
	Dec. 31, 2019
Minimum
Term of agreements	1 year
Renewal term agreement	1 year
Maximum
Term of agreements	59 years
Renewal term agreement	50 years

Leases (Components of Lease Cos

Leases (Components of Lease Costs) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Finance lease cost:
Amortization of right of use assets	$ 64
Interest on lease liabilities	43
Operating lease cost	793
Variable lease cost	91
Short-term lease cost	746
Total lease cost	$ 1,737

Leases (Supplemental Balance Sh

Leases (Supplemental Balance Sheet Disclosure) (Details) - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018
Assets
Right of use assets	[1]	$ 2,459	$ 0
Liabilities
Operating lease liabilities	[1]	604	0
Long-term operating lease liabilities	[1]	1,875	0
Total operating lease liabilities		$ 2,479
Weighted average remaining lease term (in years)		6 years 2 months 12 days
Weighted average discount rate		4.02%
Assets
Property, plant and equipment, gross		$ 64,623	61,213
Accumulated depreciation		19,008	16,155
Property, plant and equipment, net		45,615	45,058
Liabilities
Debt due within one year		711	544
Long-term debt		28,127	26,980
Total finance lease liabilities		698	$ 649
Finance Lease
Assets
Property, plant and equipment, gross		807
Accumulated depreciation		227
Property, plant and equipment, net		580
Liabilities
Debt due within one year		62
Long-term debt		636
Total finance lease liabilities		$ 698
Weighted average remaining lease term (in years)		11 years 10 months 24 days
Weighted average discount rate		6.50%
[1]	We adopted ASU No. 2016-02, Leases (“ASC 842”), as of January 1, 2019. See Notes 3 and 25 for further information.

Leases (Schedule Of Future Mini

Leases (Schedule Of Future Minimum Commitments) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Operating
Due next twelve months	$ 698	$ 709
Due year two	590	619
Due year three	402	553
Due year four	287	389
Due year five	222	295
Due after year five	634	858
Gross lease payments	2,833	3,423
Less: imputed interest	354
Total operating lease liabilities	2,479
Finance
Due next twelve months	96	70
Due year two	87	71
Due year three	95	66
Due year four	98	75
Due year five	84	82
Due after year five	527	586
Gross lease payments	987	950
Less: imputed interest	289	301
Finance lease obligations	$ 698	$ 649

Leases (Lessor Narrative) (Deta

Leases (Lessor Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Leases [Abstract]
Operating lease revenue	$ 254	$ 221	$ 218

Leases (Minimum Future Rentals

Leases (Minimum Future Rentals On The Non-Cancellable Operating Leases) (Details) $ in Millions	Dec. 31, 2019USD ($)
Leases [Abstract]
2020	$ 186
2021	179
2022	177
2023	170
2024	167
2025 and thereafter	1,072
Total minimum future rentals	$ 1,951

Leases (Investments In Assets H

Leases (Investments In Assets Held For Operating Lease By Major Classes) (Details) $ in Millions	Dec. 31, 2019USD ($)
Operating Leased Assets [Line Items]
Property, plant and equipment, gross	$ 1,935
Less accumulated depreciation	327
Property, plant and equipment, net	1,608
Natural gas gathering and NGL transportation pipelines and facilities
Operating Leased Assets [Line Items]
Property, plant and equipment, gross	1,121
Natural gas processing facilities
Operating Leased Assets [Line Items]
Property, plant and equipment, gross	686
Terminals and related assets
Operating Leased Assets [Line Items]
Property, plant and equipment, gross	83
Land, building, office equipment and other
Operating Leased Assets [Line Items]
Property, plant and equipment, gross	$ 45

Commitments and Contingencies (

Commitments and Contingencies (Details)	12 Months Ended
	Dec. 31, 2019
Pending Litigation
Loss Contingencies [Line Items]
Loss contingency, inestimable loss	For matters for which we have not recorded an accrued liability, we are unable to estimate a range of possible loss because the issues involved have not been fully developed through pleadings and discovery

Commitments and Contingencies_2

Commitments and Contingencies (Environmental Matters) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Accrued liabilities for remediation	$ 433	$ 455
Receivables for recoverable costs	$ 29	$ 35

Commitments and Contingencies_3

Commitments and Contingencies (Asset Retirement Obligations) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Asset retirement obligation, current	$ 24	$ 30
Asset retirement obligations, noncurrent	$ 206	$ 222

Commitments and Contingencies_4

Commitments and Contingencies (Guarantees) (Details) $ in Millions	Dec. 31, 2019USD ($)
Gray Oak Pipeline LLC [Member]
Loss Contingencies [Line Items]
Equity method investments, ownership percentage	25.00%
Crowley Blue Water Partners
Loss Contingencies [Line Items]
Equity method investments, ownership percentage	50.00%
Indirect Ownership Interest | Bakken Pipeline System
Loss Contingencies [Line Items]
Equity method investments, ownership percentage	9.00%
Financial Guarantee | Guarantee of Indebtedness of Others | LOOP and LOCAP LLC
Loss Contingencies [Line Items]
Maximum potential undiscounted payments	$ 171
Financial Guarantee | Guarantee of Indebtedness of Others | Gray Oak Pipeline LLC [Member]
Loss Contingencies [Line Items]
Maximum potential undiscounted payments	292
Line of credit facility, maximum borrowing capacity	1,430
Financial Guarantee | Guarantee of Indebtedness of Others | Bakken Pipeline System
Loss Contingencies [Line Items]
Maximum potential undiscounted payments	230
Financial Guarantee | Guarantee of Indebtedness of Others | Crowley Ocean Partners
Loss Contingencies [Line Items]
Maximum potential undiscounted payments	130
Financial Guarantee | Guarantee of Indebtedness of Others | Crowley Blue Water Partners
Loss Contingencies [Line Items]
Maximum potential undiscounted payments	122
Other Guarantees
Loss Contingencies [Line Items]
Maximum potential undiscounted payments	121
Guarantee of Indebtedness of Others | Financial Guarantee | Crowley Ocean Partners | Crowley Term Loan
Loss Contingencies [Line Items]
Line of credit facility, maximum borrowing capacity	$ 325

Commitments and Contingencies_5

Commitments and Contingencies (Contractual Commitments and Contingencies) (Details) - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Contractual commitments to acquire property, plant and equipment and advance funds to equity method investees	$ 1.6	$ 1.8

Selected Quarterly Financial _3

Selected Quarterly Financial Data (Schedule Of Quarterly Financial Information) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended																12 Months Ended
		Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Data [Abstract]
Sales and other operating revenues	[1]	$ 31,092		$ 31,043		$ 33,547		$ 28,267		$ 32,333		$ 22,988		$ 22,317		$ 18,866
Income from operations		841		2,024		2,042		669		2,017		1,403		1,711		440		$ 5,576	$ 5,571	$ 4,018
Net income		262		1,367		1,367		259		1,195		941		1,235		235		3,255	3,606	3,804
Net income attributable to MPC		$ 443		$ 1,095		$ 1,106		$ (7)		$ 951		$ 737		$ 1,055		$ 37		$ 2,637	$ 2,780	$ 3,432
Net income attributable to MPC per share:
Net income attributable to MPC per share – basic		$ 0.68	[2]	$ 1.67	[2]	$ 1.67	[2]	$ (0.01)	[2]	$ 1.38	[2]	$ 1.63	[2]	$ 2.30	[2]	$ 0.08	[2]	$ 4	$ 5.36	$ 6.76
Net income attributable to MPC per share – diluted		$ 0.68	[2]	$ 1.66	[2]	$ 1.66	[2]	$ (0.01)	[2]	$ 1.35	[2]	$ 1.62	[2]	$ 2.27	[2]	$ 0.08	[2]	$ 3.97	$ 5.28	$ 6.70
[1]	Includes sales to related parties.
[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.