Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Weighted average number of shares outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Trading Arrangement: Trading Arrangement [Axis] Other foreign countries Other Foreign Countries [Member] Other foreign countries include the results of non-material operating segments that are not individually reportable. 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[Table Text Block] Line of Credit Line of Credit [Member] Restatement Determination Date Restatement Determination Date Amendment Flag Amendment Flag Goodwill [Line Items] Goodwill [Line Items] Current liabilities Liabilities, Current [Abstract] Provision for credit losses Accounts Receivable, Credit Loss Expense (Reversal) Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Other Other Other [Member] Other [Member] Other comprehensive earnings (losses): Other Comprehensive Income (Loss), Net of Tax [Abstract] Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Property, Plant, and Equipment [Abstract] Property, Plant, and Equipment [Abstract] Entity Address, State or Province Entity Address, State or Province PEO Total Compensation Amount PEO Total Compensation Amount Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Intangibles – net Total intangible assets, 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Results Segment Reporting [Table Text Block] Noncontrolling Interest Noncontrolling Interest [Member] Manufacturing Manufacturing [Member] Manufacturing [Member] Total debt Long-Term Debt PROPERTY, BUILDINGS AND EQUIPMENT Property, Plant, and Equipment [Text Block] Customer lists and relationships Customer-Related Intangible Assets [Member] Income taxes – net Increase (Decrease) in Income Taxes Payable Document Period End Date Document Period End Date Change in operating assets and liabilities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Net cash used in investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Dividend declared (in dollars per share) Dividends Payable, Amount Per Share 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[Member] Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Common stock, shares authorized (in shares) Common Stock, Shares Authorized Trade accounts payable Accounts Payable, Trade Weighted average life Intangible Asset, Finite-Lived, Useful Life Exercise Price Award Exercise Price Cash flows from investing activities: Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Segment Reporting [Line Items] Segment Reporting [Line Items] Document Quarterly Report Document Quarterly Report Long-term debt, fair value Long-Term Debt, Excluding Current Maturities, Fair Value Disclosure Long-Term Debt, Excluding Current Maturities, Fair Value Disclosure Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member] Segments [Domain] Segments [Domain] DEBT Debt Disclosure [Text Block] Payments of debt Repayments of Long-Term Debt Debt issuance cost - net of amortization Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net Debt issuance costs – net of amortization and other Debt Issuance Costs, Net Capital contribution Additional Paid In Capital, Capital Contribution Additional Paid In Capital, Capital Contribution Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Equity Component [Domain] Equity Component [Domain] PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Secured Debt Secured Debt [Member] Adoption Date Trading Arrangement Adoption Date Interest rate Debt Instrument, Interest Rate, Stated Percentage Cash dividends paid Dividends, Common Stock, Cash Total W.W. Grainger, Inc. shareholders’ equity Equity, Attributable to Parent Total other expense – net Nonoperating Income (Expense) Assets Assets [Abstract] Title Trading Arrangement, Individual Title Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Goodwill and intangible asset impairment Intangible Asset, Including Goodwill, Impairment Loss Insider Trading Policies and Procedures [Line Items] Other – net Proceeds from (Payment for) Other Financing Activity Allowance for doubtful accounts Accounts Receivable, Allowance for Credit Loss, Current Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Selling, general and administrative expenses Selling, General and Administrative Expense Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Schedule of Balances and Changes in Carrying Amounts of Goodwill Goodwill [Table Text Block] Entity Central Index Key Entity Central Index Key Weighted average life Weighted Average [Member] Less accumulated depreciation Property, Plant, and Equipment, Accumulated Depreciation, Depletion, and Amortization Additional contributed capital Additional Paid in Capital, Common Stock All Adjustments to Compensation All Adjustments to Compensation [Member] Segment Reporting, Reconciling Item, Corporate Nonsegment Segment Reporting, Reconciling Item, Corporate Nonsegment [Member] Other non-current liabilities Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Other Item Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Net cash provided by operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation CONTINGENCIES AND LEGAL MATTERS Legal Matters and Contingencies [Text Block] 4.20% senior notes due 2047 Unsecured Senior Notes, 4.20% [Member] Unsecured Senior Notes, 4.20% [Member] Income Statement [Abstract] Income Statement [Abstract] Document Transition Report Document Transition Report Intersegment Eliminations Intersegment Eliminations [Member] Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Schedule of Balance in Intangible Assets, Net Intangible Asset, Finite-Lived [Table Text Block] Schedule of Revenue by Geographic Location Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Geographical Area, Revenue and Long-Lived Asset [Table Text Block] City Area Code City Area Code Accumulated Other Comprehensive Earnings (Losses) AOCI Attributable to Parent [Member] All Individuals All Individuals [Member] SUBSEQUENT EVENTS Subsequent Events [Text Block] Non-cash lease expense Operating Lease, Right-of-Use Asset, Periodic Reduction Name Forgone Recovery, Individual Name Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Commercial paper and other Other Short-Term Debt Other Short-Term Debt Statement [Line Items] Statement [Line Items] Total assets Assets Accrued sales incentives Contract With Customer, Sales Incentive Liability Contract With Customer, Sales Incentive Liability Cumulative preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Segment Balances Before Intersegment Eliminations and Consolidation Reconciling Items Segments Operating Segments [Member] PEO PEO [Member] Goodwill Goodwill, beginning balance Goodwill, ending balance Goodwill Commercial Services Commercial Services [Member] Commercial [Member] Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Subsequent Event Type [Domain] Subsequent Event Type [Domain] Retained Earnings Retained Earnings [Member] Long-term operating lease liability Operating Lease, Liability, Noncurrent Summarized Information: Segment Reporting Information Assets [Abstract] Capitalized software Software, In-Development, Internally Developed, and Purchased [Member] Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Increase (Decrease) in Stockholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Award Timing Disclosures [Line Items] Diluted (in dollars per share) Earnings Per Share, Diluted Entity Current Reporting Status Entity Current Reporting Status Net cash used in financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Total Shareholder Return Amount Total Shareholder Return Amount Prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Short-term borrowings (repayments), original maturities of 90 days or less, net Proceeds from (Repayments of) Short-Term Debt, Maturing in Three Months or Less Warehousing Warehousing [Member] Warehousing Intangible Asset, Finite-Lived [Line Items] Intangible Asset, Finite-Lived [Line Items] Adjustments to reconcile net earnings to net cash provided by operating activities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Commercial paper and other Other Short-Term Debt [Member] Other Short-Term Debt Cash flows from financing activities: Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Property, buildings and equipment – net Property, buildings and equipment – net Property, Plant, and Equipment, after Accumulated Depreciation, Depletion, and Amortization Net sales Revenue from Contract with Customer, Excluding Assessed Tax Current maturities, fair value Long-Term Debt, Current Maturities, Fair Value Disclosure Long-Term Debt, Current Maturities, Fair Value Disclosure Postretirement benefit plan losses – net of tax benefit of $1, $1, $2, and $2, respectively Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax Purchases of treasury stock Stock Repurchased During Period, Value Debt issuance costs – net of amortization and other, fair value Debt Issuance Cost, Net, Fair Value Debt Issuance Cost, Net, Fair Value Deferred income taxes and tax uncertainties Deferred Income Taxes and Other Tax Liabilities, Noncurrent Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] GOODWILL AND OTHER INTANGIBLE ASSETS Intangible Asset and Goodwill [Text Block] Underlying Securities Award Underlying Securities Amount Total comprehensive earnings (losses) attributable to noncontrolling interest Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Intangible Assets, Gross (Excluding Goodwill), Total Intangible Asset, Excluding Goodwill, before Accumulated Amortization REVENUE Revenue from Contract with Customer [Text Block] Deferred income taxes and tax uncertainties Other Income Tax Expense (Benefit), Continuing Operations Other – net Payment for (Proceeds from) Other Investing Activity Inventories Increase (Decrease) in Inventories Purchases of noncontrolling interests Proceeds from (Payments to) Noncontrolling Interests Segment Reporting [Table] Segment Reporting [Table] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] All Trading Arrangements All Trading Arrangements [Member] Other Performance Measure, Amount Other Performance Measure, Amount Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Operating earnings Segment operating earnings Operating Income (Loss) Current Fiscal Year End Date Current Fiscal Year End Date Healthcare Healthcare Industry [Member] Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Entity File Number Entity File Number Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Common stock, shares issued (in shares) Common Stock, Shares, Issued Measure: Measure [Axis] Treasury stock, shares at cost (in shares) Treasury Stock, Common, Shares Principal amount repaid Debt Instrument, Repaid, Principal Equity Components [Axis] Equity Components [Axis] Accounts receivable Increase (Decrease) in Accounts Receivable 3.75% senior notes due 2046 Unsecured Senior Notes, 3.75% [Member] Unsecured Senior Notes, 3.75% [Member] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Neil Novich [Member] Neil Novich Entity Interactive Data Current Entity Interactive Data Current Less net earnings attributable to noncontrolling interest Net earnings Net Income (Loss) Attributable to Noncontrolling Interest Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Entity Small Business Entity Small Business Comprehensive earnings attributable to W.W. Grainger, Inc. Comprehensive Income (Loss), Net of Tax, Attributable to Parent Postretirement benefit plan reclassification, net of tax benefit Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax Termination Date Trading Arrangement Termination Date Property, Plant, and Equipment [Line Items] Property, Plant, and Equipment [Line Items] 4.60% senior notes due 2045 Unsecured Senior Notes, 4.60% [Member] Unsecured Senior Notes, 4.60% [Member] Trade accounts payable Increase (Decrease) in Accounts Payable, Trade Subsequent Events [Abstract] Subsequent Events [Abstract] Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Interest expense – net Interest Income (Expense), Operating MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Other assets Other Assets, Noncurrent Document Type Document Type Fair Value as of Grant Date Award Grant Date Fair Value Schedule of Goodwill [Table] Goodwill [Table] Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Foreign currency translation adjustments Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax Arrangement Duration Trading Arrangement Duration Subsequent Event [Line Items] Subsequent Event [Line Items] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Local Phone Number Local Phone Number Canada CANADA Consolidation Items [Axis] Consolidation Items [Axis] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Entity Registrant Name Entity Registrant Name Earnings before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Gross carrying amount Intangible Asset, Finite-Lived, before Accumulated Amortization Property, buildings and equipment Property, Plant, and Equipment, before Accumulated Depreciation, Depletion, and Amortization Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Executive Category: Executive Category [Axis] Contractors Contractors [Member] Contractors [Member] Goodwill [Roll Forward] Goodwill [Roll Forward] Liabilities and shareholders' equity Liabilities and Equity [Abstract] Inventories – net Inventory, Net All Award Types Award Type [Domain] Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount PEO Name PEO Name Geographical [Axis] Geographical [Axis] Stock-based compensation APIC, Share-Based Payment Arrangement, ESPP, Increase for Cost Recognition Property, Plant and Equipment, Type [Axis] Long-Lived Asset, Class [Axis] Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Entity Tax Identification Number Entity Tax Identification Number Endless Assortment Endless Assortment [Member] Endless Assortment Cash and cash equivalents at beginning of year Cash and cash equivalents at end of period Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Intangible Asset, Finite-Lived [Table] Intangible Asset, Finite-Lived [Table] Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Total company revenue (as a percent) Percentage Of Company-Wide Revenue Percentage Of Company-Wide Revenue Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Non-NEOs Non-NEOs [Member] Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Comprehensive earnings – net of tax Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Debt Instrument [Axis] Debt Instrument [Axis] Subsequent Event [Table] Subsequent Event [Table] Stock-based compensation Share-Based Payment Arrangement, Noncash Expense High-Touch Solutions N.A. High-Touch Solutions (N.A.) [Member] High-Touch Solutions (N.A.) Customer [Domain] Customer [Domain] Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Basic (in dollars per share) Earnings Per Share, Basic Purchases of treasury stock Payments for Repurchase of Common Stock Total current assets Assets, Current Statistical Measurement [Axis] Statistical Measurement [Axis] Insider Trading Arrangements [Line Items] Long-term debt Long-term debt Long-Term Debt, Excluding Current Maturities Award Type Award Type [Axis] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Accounts receivable (less allowance for credit losses of $33 and $32, respectively) Accounts Receivable, after Allowance for Credit Loss, Current Retained earnings Retained Earnings (Accumulated Deficit) Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Furniture, fixtures, machinery and equipment Furniture, Fixtures, Machinery and Equipment [Member] Furniture, Fixtures, Machinery and Equipment [Member] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Common Stock Common Stock [Member] 1.85% senior notes due 2025 Unsecured Senior Notes, 1.85% [Member] Unsecured Senior Notes, 1.85% Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Cover [Abstract] Cover [Abstract] Government Government Customer [Member] Government Customer [Member] Translation Goodwill, Foreign Currency Translation, Gain (Loss) Equity Awards Adjustments Equity Awards Adjustments [Member] Total liabilities and shareholders' equity Liabilities and Equity Employee Stock Option Share-Based Payment Arrangement, Option [Member] Noncontrolling interest Equity, Attributable to Noncontrolling Interest Segments [Axis] Segments [Axis] Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Intangible Assets [Axis] Asset Class [Axis] Tabular List, Table Tabular List [Table Text Block] Other – net Other Nonoperating Income (Expense) Name Awards Close in Time to MNPI Disclosures, Individual Name Shareholders' equity Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Foreign currency translation adjustments Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Noncontrolling Interest Other, fair value Other Short-Term Debt, Fair Value Other Short-Term Debt, Fair Value Property, Plant and Equipment, Type [Domain] Long-Lived Asset, Class [Domain] Cumulative preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Property, Plant, and Equipment [Table] Property, Plant, and Equipment [Table] Cumulative preferred stock – $5 par value – 12,000,000 shares authorized; none issued or outstanding Preferred Stock, Value, Issued Adjustment to Compensation: Adjustment to Compensation [Axis] 4.45% senior notes due 2034 Unsecured Senior Notes, 4.45% [Member] Unsecured Senior Notes, 4.45% Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Transactions with noncontrolling interests, net Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests Credit Facility [Axis] Credit Facility [Axis] Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Name Measure Name Pay vs Performance Disclosure [Line Items] Debt Instrument [Line Items] Debt Instrument [Line Items] Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Additional Contributed Capital Additional Paid-in Capital [Member] Entity Filer Category Entity Filer Category Accrued expenses Accrued Liabilities Name Trading Arrangement, Individual Name Cash and cash equivalents Cash and Cash Equivalent Company Selected Measure Amount Company Selected Measure Amount Less comprehensive earnings (losses) attributable to noncontrolling interest Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest [Abstract] Depreciation, amortization and non-cash lease expense Depreciation, Depletion and Amortization Net earnings Net earnings Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Current assets Assets, Current [Abstract] Non-PEO NEO Non-PEO NEO [Member] Senior Notes Senior Notes Senior Notes [Member] Entity Address, Address Line One Entity Address, Address Line One Income tax provision Income Tax Expense (Benefit) Cost of goods sold Cost of Product and Service Sold Award Timing Method Award Timing Method [Text Block] Net change in cash and cash equivalents Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Net earnings attributable to W.W. Grainger, Inc. Net Income (Loss) Attributable to Parent Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Statement [Table] Statement [Table] Proceeds from sale of assets Proceeds from Sale of Property, Plant, and Equipment Total net sales (as a percent) Revenue From Contract With Customer, Excluding Assessed Tax, Percentage Revenue From Contract With Customer, Excluding Assessed Tax, Percentage Restatement Determination Date: Restatement Determination Date [Axis] Proceeds from stock options exercised Proceeds from Stock Options Exercised Japan JAPAN Other non-current liabilities Liability, Other Postretirement Defined Benefit Plan, Noncurrent Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block]