Belgium [Member] Canada [Member] Germany [Member] France [Member] United Kingdom [Member] Italy [Member] Singapore [Member] United States [Member] Pension Benefits - U.S. U.S. [Member] Accounting Changes [Text Block] Accounting changes Summary of Accounting Policies [Abstract] Accounts payable and accrued liabilities current Accounts payable and accrued liabilities Total Total Income taxes payable Unrealized change in fair value of stock investments Beginning Balance, Unrealized Change in Stock Investments Ending Balance, Unrealized Change in Stock Investments Postretirement benefits reserves adjustment Postretirement benefits reserves adjustment Ending Balance, Postretirement Benefits Reserves Adjustment Beginning Balance, Postretirement Benefits Reserves Adjustment Ending Balance, Postretirement Benefits Reserves Adjustment Beginning Balance, Postretirement Benefits Reserves Adjustment Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax, Total Cumulative foreign exchange translation adjustment Ending Balance, Cumulative Foreign Exchange Translation Adjustment Beginning Balance, Cumulative Foreign Exchange Translation Adjustment Cumulative Translation adjustments Accumulated Other Comprehensive Income [Member] Exxon Mobil Share Of Accumulated Other Comprehensive Income [Member] Accumulated Other Comprehensive Income (Loss), Net of Tax Ending Balance, Total Beginning Balance, Total Accumulated Other Comprehensive Income (Loss), Net of Tax, Total Accumulated other comprehensive income Adjustments to Additional Paid in Capital, Tax Effect from Share-based Compensation Tax benefits related to stock-based awards Assets Assets and Liabilities Lessee [Abstract] Total assets Total assets Total assets Total current assets Total current assets Total current assets Current assets Current assets Basis Of Presentation Disclosure [Table Text Block] Basis Of Financial Statement Preparation Shares issued for 2017 noncash transactions Business Acquisition Equity Interests Issued Or Issuable Number Of Shares Issued CapitalizedExploratoryWellCostChargedToExpense1 Charged to expense in period Capitalized Exploratory Well Costs [Abstract] Carrying Value Reported Amount Fair Value Disclosure [Member] Carrying Reported Amount Fair Value Disclosure [Member] Increase/(decrease) in cash and cash equivalents Increase/(decrease) in cash and cash equivalents Cash and cash equivalents Cash and cash equivalents at end of period Cash and cash equivalents at beginning of period Cash and Cash Equivalents, at Carrying Value, Total Commitments and contingencies Commitments and contingencies (Note 3) Common Stock [Member] Exxon Mobil Share Of Common Stock [Member] Common stock, shares authorized Common stock, without par value Dividends per common share (dollars) Dividends paid per common share (dollars) Common stock, shares issued Common Stock, Shares, Issued, Total Balance (in shares) - issued Balance (in shares) - issued Common Stock, Shares, Outstanding Balance (in shares) - outstanding Balance (in shares) - outstanding Common stock, shares, outstanding Common stock without par value (9,000) million shares authorized, 8,019 million shares issued) Common Stock, Value, Issued, Ending Balance Common Stock, Value, Issued, Beginning Balance Common stock without par value (9,000 million shares authorized, 8,019 million shares issued) Common Stock, Value, Issued, Total Compensation And Retirement Disclosure [Abstract] Comprehensive income attributable to noncontrolling interests Comprehensive income attributable to noncontrolling interests Comprehensive Income, Net of Tax, Attributable to Noncontrolling Interest, Total Comprehensive Income Note [Text Block] Summary of the change in accumulated other comprehensive income Other Comprehensive Income Information Other Comprehensive Income Information [Abstract] Comprehensive income attributable to ExxonMobil Comprehensive income attributable to ExxonMobil Comprehensive income attributable to ExxonMobil Comprehensive income including noncontrolling interests Net income including noncontrolling interests Comprehensive income including noncontrolling interests Costs and other deductions Costs And Expenses Total costs and other deductions Total costs and other deductions Crude Oil [Member] Debt Instrument Fair Value Long-term debt (excluding capitalized lease obligations) Fair value of long term debt by hierarchy level Debt, Current, Total Notes and loans payable Total Short-term debt Deferred income tax liabilities Net pension enhancement and curtailment/settlement expense Net pension enhancement and curtailment/settlement cost Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments, Total Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlement and Curtailments Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Expected return on plan assets Expected return on plan assets Interest cost Interest cost Net benefit cost Net periodic benefit cost Net benefit cost Service cost Service cost Depreciation and depletion Depreciation and depletion expense Segment Reporting Information, Depreciation, Depletion, and Amortization Expense, Total Derivative Nonmonetary Notional Amount Volume Net notional long / short position of derivative instruments bbl Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net Abstract Derivative Assets Current Derivative assets Derivative [Table] Derivative Instruments Not Designated As Hedging Instruments Abstract Derivative Liabilities Current Derivative liabilities Derivative Instruments Gain Loss By Hedging Relationship By Income Statement Location By Derivative Instrument Risk [Table] Derivative Instruments Gain Loss [Line Items] Realized and Unrealized Before-Tax Gain / Loss on Derivative Instruments Recognized in the Consolidated Statement of Income Derivatives, Policy [Text Block] Dividends - common shares Dividends - common shares (company) Dividends, Common Stock, Total United States Pension Plans Of U S Entity Defined Benefit [Member] Pension Benefits - U.S. [Member] Due To Related Parties Noncurrent Long-term obligations to equity companies Earnings Per Share Text Block Earnings Per Share Earnings per common share (dollars) Earnings per common share (dollars) Earnings Per Share, Basic, Total Earnings Per Common Share [Abstract] Earnings per common share Earnings per common share - assuming dilution (dollars) Earnings per common share - assuming dilution Earnings Per Share, Diluted, Total Earnings Per Share [Abstract] Effects of exchange rate changes on cash Effect of Exchange Rate on Cash and Cash Equivalents, Total Energy Related Inventory Crude oil, products and merchandise Total Total Energy [Axis] Energy [Domain] Equity Component [Domain] Equity Component [Domain] Error Corrections and Prior Period Adjustments [Line Items] Excess Tax Benefit From Share Based Compensation Financing Activities Tax benefits related to stock-based awards Exploration expenses, including dry holes Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Table] Financial Instruments [Abstract] Fair Value By Measurement Basis [Axis] Defined Benefit Plan, Fair Value of Plan Assets by Measurement [Axis] Fair Value Plan Asset Measurement [Domain] Fair Value Plan Asset Measurement [Domain] Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] Financial Instrument [Line Items] Fair Value Disclosure Item Amounts [Domain] Fair Value Inputs Level3 [Member] Level 3 [Member] Fair Value Inputs Level1 [Member] Level 1 [Member] Fair Value Inputs Level2 [Member] Level 2 [Member] Foreign Pension Plans Defined Benefit [Member] Pension Benefits - Non-U.S. [Member] Gain Loss On Derivative Instruments Net Pretax Total Guarantees