Fair Value Disclosures [Abstract] Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Fair Value, by Balance Sheet Grouping Fair Value, by Balance Sheet Grouping [Table Text Block] Leases [Abstract] Weighted average lease term Operating Lease, Weighted Average Remaining Lease Term Discount rate Lessee, Operating Lease, Discount Rate Annual payments to be received Lessor, Operating Lease, Annual Payments to be Received Lessor, Operating Lease, Annual Payments to be Received Maximum financing available Lessee, Finance Lease, Maximum Financing Available Lessee, Finance Lease, Maximum Financing Available Total costs incurred under lease Lessee, Finance Lease, Total Costs Incurred Lessee, Finance Lease, Total Costs Incurred Term of contract Lessee, Finance Lease, Term of Contract Residual value guarantee Lessee, Finance Lease, Residual Value Guarantee, Percentage Lessee, Finance Lease, Residual Value Guarantee, Percentage Revenue from Contract with Customer [Abstract] Receivables from contracts with customers, included in receivables, less reserves Contract With Customer, Accounts Receivable, Net Contract With Customer, Accounts Receivable, Net Contract asset (liability) Contract with Customer, Liability Discontinued Operations and Disposal Groups [Abstract] Dispositions Disposal Groups, Including Discontinued Operations, Disclosure [Text Block] Equity Method Investments and Joint Ventures [Abstract] Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] EGHoldings EG Holdings [Member] Equatorial Guinea LNG Holdings Limited, in which Marathon owns a 60 percent noncontrolling interest. This entity processes liquefied natural gas. Marathon's investment is accounted for using the equity method. Alba Plant LLC Alba Plant LLC [Member] Alba Plant LLC, in which we have a 52 percent noncontrolling interest. This company processes liquefied petroleum gas. Marathon's investment is accounted for using the equity method. AMPCO AMPCO [Member] Atlantic Methanol Production Company LLC, in which we have a 45 percent interest. This company is engaged in methanol production activity. Marathon's investment is accounted for using the equity method. Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Ownership percentage Equity Method Investment, Ownership Percentage Equity method investments Equity Method Investments Income data: Equity Method Investment, Summarized Financial Information, Income Statement [Abstract] Revenues and other income Equity Method Investment, Summarized Financial Information, Revenue Net income Equity Method Investment, Summarized Financial Information, Net Income (Loss) Earnings Per Share [Abstract] Income (Loss) and Dividends per Common Share Earnings Per Share [Text Block] Supplemental Cash Flow Elements [Abstract] Included in operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Interest paid, net of amounts capitalized Interest Paid, Net Income taxes paid to taxing authorities Income Taxes Paid, Net Noncash investing activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Increase in asset retirement costs Asset Retirement Obligation, Period Increase (Decrease) Asset retirement obligations assumed by buyer(a) Asset Retirement Obligation, Liabilities Transferred Asset Retirement Obligation, Liabilities Transferred Capital expenditures incurred but not yet paid Capital Expenditures Incurred but Not yet Paid Statement of Financial Position [Abstract] Allowance for doubtful accounts Allowance for Doubtful Accounts Receivable, Current Less accumulated depreciation, depletion and amortization Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Preferred stock, no par value Preferred Stock, Par or Stated Value Per Share Preferred stock shares authorized Preferred Stock, Shares Authorized Preferred stock shares issued Preferred Stock, Shares Issued Preferred stock shares outstanding Preferred Stock, Shares Outstanding Common stock, par value per share Common Stock, Par or Stated Value Per Share Common stock shares authorized Common Stock, Shares Authorized Common stock, shares issued Common Stock, Shares, Issued Held in treasury, shares Treasury Stock, Shares Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) [Table] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Commodity Commodity Contract [Member] Derivative Instruments, Gain (Loss) [Line Items] Net loss on commodity derivatives Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net Net gain (loss) on settlements, net Derivative Instrument Not Designated As Hedging Instruments, Gain (Loss) On Settlements, Net Derivative Instrument Not Designated As Hedging Instruments, Gain (Loss) On Settlements, Net Debt Disclosure [Abstract] Line of Credit Facility [Table] Line of Credit Facility [Table] Short-term Debt, Type [Axis] Short-term Debt, Type [Axis] Short-term Debt, Type [Domain] Short-term Debt, Type [Domain] Revolving Credit Facility Revolving Credit Facility [Member] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Line of credit Line of Credit, Current Maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Covenant, ratio of indebtedness to net capital, maximum Debt Instrument, Covenant, Ratio Of Indebtedness To Net Capital, Maximum Debt Instrument, Covenant, Ratio Of Indebtedness To Net Capital, Maximum Ratio of indebtedness to net capital Ratio of Indebtedness to Net Capital Long-term debt Long-term Debt and Capital Lease Obligations Long-term debt maturing in 2020 Long-term Debt, Maturities, Repayments of Principal in Year Three Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Recurring Fair Value, Measurements, Recurring [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Level 1 Fair Value, Inputs, Level 1 [Member] Level 2 Fair Value, Inputs, Level 2 [Member] Level 3 Fair Value, Inputs, Level 3 [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Derivative instruments, assets Derivative Asset Derivative instruments, liabilities Derivative Liability Fair Value Measurements Fair Value Disclosures [Text Block] Derivative Instruments Balance Sheet [Abstract] Derivative Instrument Detail [Abstract] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Derivatives Fair Value by Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Other current liabilities Other Current Liabilities [Member] Deferred credits and other liabilities Other Noncurrent Liabilities [Member] Other Current Assets [Member] Other Current Assets [Member] Other Noncurrent Assets [Member] Other Noncurrent Assets [Member] Hedging Designation [Axis] Hedging Designation [Axis] Hedging Designation [Domain] Hedging Designation [Domain] Not Designated as Hedges Not Designated as Hedging Instrument [Member] Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] Asset Derivative Asset, Fair Value, Gross Asset Liability Derivative Liability, Fair Value, Gross Liability Derivative Asset, Fair Value, Amount Not Offset Against Collateral Derivative Asset, Fair Value, Amount Not Offset Against Collateral Net Asset (Liability) Derivative Liability, Fair Value, Amount Not Offset Against Collateral Assets Assets [Abstract] Current assets: Assets, Current [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Receivables, less reserve of $12 and $11 Accounts Receivable, Net, Current Inventories Inventory, Net Other current assets Other Assets, Current Current assets held for sale Disposal Group, Including Discontinued Operation, Assets, Current Total current assets Assets, Current Property, plant and equipment, less accumulated depreciation, depletion and amortization of $17,669 and $21,830 Property, Plant and Equipment, Net Goodwill Goodwill Other noncurrent assets Other Assets, Noncurrent Noncurrent assets held for sale Disposal Group, Including Discontinued Operation, Other Assets, Noncurrent Total assets Assets Liabilities Liabilities [Abstract] Current liabilities: Liabilities, Current [Abstract] Accounts payable Accounts Payable, Current Payroll and benefits payable Employee-related Liabilities, Current Accrued taxes Accrued Income Taxes, Current Other current liabilities Other Liabilities, Current Current liabilities held for sale Disposal Group, Including Discontinued Operation, Liabilities, Current Total current liabilities Liabilities, Current Deferred tax liabilities Deferred Income Tax Liabilities, Net Defined benefit postretirement plan obligations Postemployment Benefits Liability, Noncurrent Asset retirement obligations Asset Retirement Obligations, Noncurrent Deferred credits and other liabilities Deferred credit and other liabilities Deferred credit and other liabilities Noncurrent liabilities held for sale Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent Total liabilities Liabilities Commitments and contingencies Commitments and Contingencies Stockholders’ Equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Preferred stock – no shares issued or outstanding (no par value, 26 million shares authorized) Preferred Stock, Value, Issued Common stock: Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract] Issued – 937 million shares and 937 million shares (par value $1 per share, 1.925 billion shares authorized at March 31, 2019 and 1.925 billion shares authorized at December 31, 2018) Common Stock, Value, Issued Held in treasury, at cost – 117 million shares and 118 million shares Treasury Stock, Value Additional paid-in capital Additional Paid in Capital Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax Total stockholders' equity Stockholders' Equity Attributable to Parent Total liabilities and stockholders' equity Liabilities and Equity Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] United States E&P North America Exploration and Production [Member] The portion of the Exploration and Production ("E&P") segment that relates to North America. The E&P segment explores for, produces and markets liquid hydrocarbons and natural gas on a worldwide basis produces and markets products manufactured from natural gas, such as liquefied natural gas ("LNG"). International E&P International Exploration and Production [Member] The portion of the Exploration and Production ("E&P") segment that relates to areas outside of North America. The E&P segment explores for, produces and markets liquid hydrocarbons and natural gas on a worldwide basis produces and markets products manufactured from natural gas, such as liquefied natural gas ("LNG") . Products and Services [Axis] Products and Services [Axis] Products and Services [Domain] Products and Services [Domain] Crude oil and condensate Crude Oil [Member] Natural gas liquids Natural Gas Liquids [Member] Natural gas Natural Gas [Member] Other Miscellaneous other [Member] Other products by the company. Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] Eagle Ford Eagle Ford [Member] Eagle Ford [Member] Bakken Bakken [Member] Bakken [Member] Oklahoma OKLAHOMA Northern Delaware Northern Delaware [Member] Northern Delaware [Member] Other U.S. Other U.S. [Member] Other U.S. [Member] E.G. EQUATORIAL GUINEA U.K. UNITED KINGDOM Libya LIBYAN ARAB JAMAHIRIYA Other International Other International [Member] A grouping of countries other than those specifically listed. Such grouping is used in reporting geographic information. Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Revenues from contracts with customers Revenue from Contract with Customer, Excluding Assessed Tax Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Preferred Stock Preferred Stock [Member] Common Stock Common Stock [Member] Treasury Stock Treasury Stock [Member] Additional Paid-in Capital Additional Paid-in Capital [Member] Retained Earnings Retained Earnings [Member] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Statement [Line Items] Statement [Line Items] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning balance Shares issued - stock-based compensation Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures Shares repurchased Treasury Stock, Value, Acquired, Cost Method Stock-based compensation Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Net income Net Income (Loss) Attributable to Parent Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Dividends paid (per share amount of $0.05) Dividends, Common Stock, Cash Cumulative Effect on Retained Earnings, Net of Tax Cumulative Effect on Retained Earnings, Net of Tax Ending balance Schedule of Derivative Instruments in the Consolidated Balance Sheets Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Schedule of Notional Amounts of Outstanding Derivative Positions Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block] Document and Entity Information [Abstract] -- None. No documentation exists for this element. -- Document Type Document Type Document Period End Date Document Period End Date Document Fiscal Period Focus Document Fiscal Period Focus Document Fiscal Year Focus Document Fiscal Year Focus Amendment Flag Amendment Flag Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Common Stock Shares Outstanding Entity Common Stock, Shares Outstanding Antidilutive securities excluded from computation of earnings per share (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Net income Weighted average common shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Basic Effect of dilutive securities (in shares) Weighted Average Number Diluted Shares Outstanding Adjustment Weighted average common shares, diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Net income per share: Earnings Per Share, Basic [Abstract] Basic Earnings Per Share, Basic Per diluted share: Earnings Per Share, Diluted [Abstract] Diluted Earnings Per Share, Diluted Dividends per share (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Inventory Disclosure [Abstract] Inventories Inventory Disclosure [Text Block] Retirement Benefits [Abstract] Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Retirement Plan Funding Status [Axis] Retirement Plan Funding Status [Axis] Retirement Plan Funding Status [Domain] Retirement Plan Funding Status [Domain] Funded Plan Funded Plan [Member] Unfunded Plan Unfunded Plan [Member] Retirement Plan Type [Axis] Retirement Plan Type [Axis] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Pension Benefits Pension Plan [Member] Other Benefits Other Postretirement Benefits Plan [Member] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Service cost Defined Benefit Plan, Service Cost Interest cost Defined Benefit Plan, Interest Cost Expected return on plan assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Amortization: Depreciation, Depletion and Amortization [Abstract] – prior service credit Defined Benefit Plan, Amortization of Prior Service Cost (Credit) – actuarial loss Defined Benefit Plan, Amortization of Gain (Loss) Net settlement loss Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement Net periodic benefit cost Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Payment for pension benefits Payment for Pension Benefits Estimated future contributions over the remainder of the current year Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year Payment for other postretirement benefit plans Payment for Other Postretirement Benefits Schedule of Earnings Per Share, Basic and Diluted Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Equity [Abstract] Schedule of Amounts Reclassified out of Accumulated Other Comprehensive Income (Loss) Reclassification out of Accumulated Other Comprehensive Income [Table Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Schedule of Inventory, Current Schedule of Inventory, Current [Table Text Block] Schedule of Net Periodic Benefit Cost Schedule of Net Benefit Costs [Table Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Maximum Maximum [Member] Minimum Minimum [Member] Title of Individual [Axis] Title of Individual [Axis] Relationship to Entity [Domain] Relationship to Entity [Domain] Granted Officer Granted Officer [Member] Granted Officer [Member] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Performance Unit Awards Performance Unit [Member] Performance Unit [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Grant date fair value (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Vesting percentage Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage Impairment Expense [Abstract] Impairment Expense [Abstract] Exploration Expenses [Table] Exploration Expenses [Table] Exploration Expenses [Table] Cost Center [Axis] Cost Center [Axis] Cost Center for Oil and Gas Disclosures [Domain] Cost Center for Oil and Gas Disclosures [Domain] Unproved property impairments Unproved Property Impairments [Member] Unproved Property Impairments [Member] Dry well costs Dry Well Costs [Member] Dry Well Costs [Member] Geological and geophysical Geological and Geophysical [Member] Geological and Geophysical [Member] Other Other Exploration Expenses [Member] Other Exploration Expense [Member] Exploration Expenses [Line Items] Exploration Expenses [Line Items] [Line Items] for Exploration Expenses [Table] Total exploration expenses Exploration Expense Leases Lessee, Operating Leases [Text Block] Leases Lessor, Operating Leases [Text Block] Supplemental Cash Flow Information Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Effective Income Tax Rate Effective Income Tax Rate [Table Text Block] [Table Text Block] for Effective Income Tax Rate [Table] Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Contract with Customer, Liability Contract with Customer, Asset and Liability [Table Text Block] Lease, Cost [Abstract] ROU asset Operating Lease, Right-of-Use Asset Operating lease costs Operating Lease, Cost Short-term lease costs Short-term Lease, Cost Variable lease costs Variable Lease, Cost Total lease costs Lease, Cost ROU assets obtained in exchange for new operating lease liabilities(d) Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Fair Value Measurements, Nonrecurring Fair Value Measurements, Nonrecurring [Table Text Block] Exploration Expenses Exploration Expenses [Table Text Block] [Table Text Block] for Exploration Expenses [Table] Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Segment Reporting [Abstract] Schedule of Segment Reporting Information, by Segment Schedule of Segment Reporting Information, by Segment [Table Text Block] 2019 Lessor, Operating Lease, Payments to be Received, Remainder of Fiscal Year 2020 Lessor, Operating Lease, Payments to be Received, Two Years 2021 Lessor, Operating Lease, Payments to be Received, Three Years 2022 Lessor, Operating Lease, Payments to be Received, Four Years 2023 Lessor, Operating Lease, Payments to be Received, Five Years Thereafter Lessor, Operating Lease, Payments to be Received, Thereafter Total undiscounted cash flows Lessor, Operating Lease, Payments to be Received Current portion of long-term lease liability Operating Lease, Liability, Current Long-term lease liability Operating Lease, Liability, Noncurrent Fair Value Measurements, Recurring and Nonrecurring [Table] Nonrecurring Fair Value, Measurements, Nonrecurring [Member] Fair Value Hierarchy [Domain] Accounting Policies [Abstract] Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Property, Plant and Equipment [Abstract] Property, Plant and Equipment, net of Accumulated Depreciation, Depletion and Amortization Property, Plant and Equipment Disclosure [Text Block] Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] Crude oil and natural gas Liquid Hydrocarbons Natural Gas Carrying amount as of the balance sheet date of crude oil, natural gas liquids, and natural gas inventories. Supplies and other items Inventory Supplies And Sundry Carrying amount as of the balance sheet date of sundry items and miscellaneous supplies. Inventories Dividends paid (in dollars per share) Lease Maturity [Abstract] Lease Maturity [Abstract] 2019 Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year 2020 Lessee, Operating Lease, Liability, Payments, Due Year Two 2021 Lessee, Operating Lease, Liability, Payments, Due Year Three 2022 Lessee, Operating Lease, Liability, Payments, Due Year Four 2023 Lessee, Operating Lease, Liability, Payments, Due Year Five Thereafter Lessee, Operating Lease, Liability, Payments, Due after Year Five Total undiscounted lease payments Lessee, Operating Lease, Liability, Payments, Due Less: Amount representing interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount Total operating lease liabilities Operating Lease, Liability Current portion of long-term lease liability as of March 31, 2019 Long-term lease liability as of March 31, 2019 Asset Retirement Obligation Disclosure [Abstract] Schedule of Changes in Asset Retirement Obligations Schedule of Change in Asset Retirement Obligation [Table Text Block] Impairments Impairments and Exploration Expenses [Text Block] Impairments and Exploration Expenses [Text Block] Class of Treasury Stock [Table] Class of Treasury Stock [Table] Share Repurchase Program [Axis] Share Repurchase Program [Axis] Share Repurchase Program [Domain] Share Repurchase Program [Domain] Share Repurchase Program Share Repurchase Program [Member] Share Repurchase Program [Member] Equity, Class of Treasury Stock [Line Items] Equity, Class of Treasury Stock [Line Items] Shares repurchased (in shares) Treasury Stock, Shares, Acquired Shares repurchased Stock repurchase program, remaining authorized repurchase amount Stock Repurchase Program, Remaining Authorized Repurchase Amount Restricted Stock Awards & Units Restricted Stock Awards And Restricted Stock Units [Member] Restricted Stock Awards And Restricted Stock Units [Member] Number of Shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Outstanding, beginning (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures Options Exercised (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Canceled (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period Outstanding, ending (in shares) Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Outstanding, beginning (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Granted (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Options Exercised (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Canceled (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price Outstanding, ending (in dollars per share) Awards Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Outstanding, beginning (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Stock Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Canceled (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Outstanding, ending (in shares) Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Outstanding, beginning (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Granted (in dollars per share) Stock Vested (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Canceled (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Outstanding, ending (in dollars per share) Weighted average grant date fair value (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Schedule of Equity Method Investments Equity Method Investments [Table Text Block] Subsequent Events [Abstract] Subsequent Events [Text Block] Subsequent Events [Text Block] Incentive Based Compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Debt Debt Disclosure [Text Block] Fair Value, by Balance Sheet Grouping [Table] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement [Member] Portion at Fair Value Measurement [Member] Fair Value Estimate of Fair Value Measurement [Member] Carrying Amount Reported Value Measurement [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Financial assets Assets, Fair Value Disclosure [Abstract] Current assets Other Assets, Fair Value Disclosure Other noncurrent assets Other Noncurrent Assets Fair Value Disclosure This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents financial assets reported as Other noncurrent assets on the Balance Sheet. Financial assets here include the noncurrent portion of receivables from United States Steel, restricted cash, long-term receivables, environmental receivables, and cost method investments. Total financial assets Financial Assets Fair Value Disclosure This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents total financial assets. Financial liabilities Financial Liabilities Fair Value Disclosure [Abstract] Other current liabilities Other Currentl Labilities Fair Value Disclosure This element represents the portion of the Current Liabilities balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Long-term debt, including current portion Long-term Debt, Fair Value Deferred credits and other liabilities Other Liabilities, Fair Value Disclosure Total financial liabilities Financial Liabilities Fair Value Disclosure Segment Information Segment Reporting Disclosure [Text Block] Disposal Groups, Including Discontinued Operations [Table] Disposal Groups, Including Discontinued Operations [Table] Disposal Group Name [Axis] Disposal Group Name [Axis] Disposal Group Name [Domain] Disposal Group Name [Domain] Non-core [Member] Non-core [Member] Marathon Oil Libya Limited Marathon Oil Libya Limited [Member] Marathon Oil Libya Limited [Member] Disposal Group Classification [Axis] Disposal Group Classification [Axis] Disposal Group Classification [Domain] Disposal Group Classification [Domain] Disposal Group, Held-for-sale, Not Discontinued Operations Disposal Group, Held-for-sale, Not Discontinued Operations [Member] Disposal Group, Disposed of by Sale, Not Discontinued Operations Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Proceeds from sale of oil and gas property and equipment Proceeds from Sale of Oil and Gas Property and Equipment Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Disposal group, assets Disposal Group, Including Discontinued Operation, Assets Disposal group, liabilities Disposal Group, Including Discontinued Operation, Liabilities Asset retirement obligations Disposal Group, Including Discontinued Operations, Asset Retirement Obligations Disposal Group, Including Discontinued Operations, Asset Retirement Obligations Disposal Group, Including Discontinued Operation, Percentage of Oil and Gas Property Disposed Disposal Group, Including Discontinued Operation, Percentage of Oil and Gas Property Disposed Disposal Group, Including Discontinued Operation, Percentage of Oil and Gas Property Disposed Net gain (loss) on disposal of assets Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal Long-lived assets, Fair Value Property, Plant, and Equipment, Fair Value Disclosure Long-lived assets, Impairment Assets, Fair Value Adjustment Statement of Cash Flows [Abstract] Cash held for sale Cash and Cash Equivalents, Period Increase (Decrease) from Cash Held for Sale Cash and Cash Equivalents, Period Increase (Decrease) from Cash Held for Sale Schedule of Stock Options, Restricted Stock Awards and Restricted Stock Units Activity Schedule of Share-based Compensation, Stock Options Activity and Nonvested Restricted Stock Units Activity [Table Text Block] 2011 taxonomy has new elements for the stock option activity and restricted stock activity tables, if they are reported separately. Because MRO combine the two tables, we still need a custom element. The previously used custom element was not a table text block type, so this one is totally new and based upon the 2011 elements for separate stock option and restricted stock activity: Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block] and Schedule of Nonvested Restricted Stock Units Activity [Table Text Block] . Asset Retirement Obligations Asset Retirement Obligation Disclosure [Text Block] Commitments and Contingencies Disclosure [Abstract] Loss Contingencies [Table] Loss Contingencies [Table] Income Tax Authority [Axis] Income Tax Authority [Axis] Income Tax Authority [Domain] Income Tax Authority [Domain] Foreign Tax Authority Foreign Tax Authority [Member] Income Tax Authority, Name [Axis] Income Tax Authority, Name [Axis] Income Tax Authority, Name [Domain] Income Tax Authority, Name [Domain] UK Government UK Government [Member] UK Government [Member] Loss Contingencies [Line Items] Loss Contingencies [Line Items] Income taxes paid from settlement with taxing authority Income Tax Examination, Liability (Refund) Adjustment from Settlement with Taxing Authority Equity Method Investments Equity Method Investments and Joint Ventures Disclosure [Text Block] Reclassifications Out of Accumulated Other Comprehensive Income (Loss) Comprehensive Income (Loss) Note [Text Block] Derivative [Table] Derivative [Table] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event [Member] Subsequent Event [Member] Three-Way Collars - Crude Oil July-December 2019, Ceiling, Two [Member] Three-Way Collars - Crude Oil July-December 2019, Ceiling, Two [Member] Three-Way Collars - Crude Oil July-December 2019, Ceiling, Two [Member] Three-Way Collars - Crude Oil July-December 2019, One [Member] Three-Way Collars - Crude Oil July-December 2019, One [Member] Three-Way Collars - Crude Oil July-December 2019, One [Member] Three-Way Collars - Crude Oil January-June 2020 [Member] Three-Way Collars - Crude Oil January-June 2020 [Member] Three-Way Collars - Crude Oil January-June 2020 [Member] Three-Way Collars - Crude Oil July-December 2019, Ceiling, One [Member] Three-Way Collars - Crude Oil July-December 2019, Ceiling, One [Member] Three-Way Collars - Crude Oil July-December 2019, Ceiling, One [Member] Midland Basis Swaps - Crude Oil 2019 Q2 [Member] [Domain] Midland Basis Swaps - Crude Oil 2019 Q2 [Member] [Domain] Midland Basis Swaps - Crude Oil 2019 Q2 [Member] [Domain] Midland Basis Swaps - Crude Oil 2019 Q4 [Member] [Domain] Midland Basis Swaps - 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Other net periodic benefit costs Income tax provision (benefit) Income Tax Expense (Benefit) Net Income (Loss) Attributable to Parent Capital expenditures Property, Plant and Equipment, Additions Change In Contract With Customer, Liability [Roll Forward] Change In Contract With Customer, Liability [Roll Forward] Change In Contract With Customer, Liability [Roll Forward] Contract asset (liability) balance as of January 1, 2019 Revenue recognized as performance obligations are satisfied Contract with Customer, Liability, Revenue Recognized Amounts invoiced to customers Contract with Customer, Asset, Reclassified to Receivable Contract asset (liability) balance as of March 31, 2019 Supplemental Balance Sheet Information Assets And Liabilities, Lessee [Table Text Block] Assets And Liabilities, Lessee [Table Text Block] Lease Costs Lease, Cost [Table Text Block] Operating Lease, Maturity Lessee, Operating Lease, Liability, Maturity [Table Text Block] Operating Lease, Undiscounted Cash Flows 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net of tax Other Comprehensive Income (Loss), Net of Tax [Abstract] Postretirement and postemployment plans: Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax [Abstract] Change in actuarial loss in postretirement and postemployment plans Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax Postretirement and postemployment plans, net of tax Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Other comprehensive income (loss) Comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Income Statement [Abstract] Revenues and other income: Revenues [Abstract] Revenues from contracts with customers Total revenues and other income Revenues Costs and expenses: Shipping, handling and other operating Other Expenses Total costs and expenses Costs and Expenses Income from operations Operating Income (Loss) Provision (benefit) for income taxes Net income per share: Per diluted share: Weighted average common shares outstanding: Weighted Average Number of Shares Outstanding, Diluted and Basic [Abstract] Weighted Average Number of Shares Outstanding, Diluted and Basic [Abstract] Basic Diluted New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Total operating lease liabilities Supplemental Cash Flow Information Cash Flow, Supplemental Disclosures [Text Block] Defined Benefit Postretirement Plans Pension and Other Postretirement Benefits Disclosure [Text Block] Schedule of Property, Plant and Equipment Property, Plant and Equipment [Table Text Block] Income Tax Contingency [Table] Income Tax Contingency [Table] UNITED STATES UNITED STATES UNITED KINGDOM Libya Tax Authority Libya Tax Authority [Member] Libya Tax Authority [Member] Income Tax Contingency [Line Items] Income Tax Contingency [Line Items] Effective Income Tax Rate Reconciliation, Percent Effective Income Tax Rate Reconciliation, Percent Tax Adjustments, Settlements, and Unusual Provisions Tax Adjustments, Settlements, and Unusual Provisions Effective income tax expense (benefit) rate(a) Effective Income Tax Rate Excluding Discrete Items Effective Income Tax Rate Excluding Discrete Items Tax benefit from settlement with taxing authority Effective income tax rate excluding Libya Effective income tax rate excluding Libya A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations excluding Libya for the period Income Taxes Receivable, Current Income Taxes Receivable, Current Derivatives Derivative Instruments and Hedging Activities Disclosure [Text Block]