Tax effects of the net changes to accumulated comprehensive income during the period related to benefit plans.

No definition available.

Name:	gww_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeDeferredTaxes
Namespace Prefix:	gww_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Catastrophic Drug Benefit

+ References

No definition available.

+ Details

Name:	gww_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationCatastrophicDrugBenefit
Namespace Prefix:	gww_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation.

+ References

No definition available.

+ Details

Name:	gww_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationExpectedLongTermReturnOnAssets
Namespace Prefix:	gww_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, HRA Credit Inflation Index For Granfathered Retirees

+ References

No definition available.

+ Details

Name:	gww_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationHRACreditInflationIndexForGranfatheredRetirees
Namespace Prefix:	gww_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Health Care Cost Trend Rate Assumed For Next Fiscal Year, Post Age 65

+ References

No definition available.

+ Details

Name:	gww_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationHealthCareCostTrendRateAssumedForNextFiscalYearPostAge65
Namespace Prefix:	gww_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The assumed health care cost trend rate for the next year used to determine benefit obligations. This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status.

+ References

No definition available.

+ Details

Name:	gww_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationHealthCareCostTrendRateAssumedForNextFiscalYearPreAge65
Namespace Prefix:	gww_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The ultimate trend rate for health care costs used to determine benefit obligations.

+ References

No definition available.

+ Details

Name:	gww_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationUltimateHealthCareCostTrendRate
Namespace Prefix:	gww_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The year when the ultimate health care cost trend rate is expected to be reached, which is used to determine benefit obligations.

+ References

No definition available.

+ Details

Name:	gww_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationYearThatRateReachesUltimateTrendRate
Namespace Prefix:	gww_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined Benefit Plan, Fair Value of Plan Liabilities

+ References

No definition available.

+ Details

Name:	gww_DefinedBenefitPlanFairValueofPlanLiabilities
Namespace Prefix:	gww_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year, Post Age 65

+ References

No definition available.

+ Details

Name:	gww_DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYearPostAge65
Namespace Prefix:	gww_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year, Pre Age 65

+ References

No definition available.

+ Details

Name:	gww_DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYearPreAge65
Namespace Prefix:	gww_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Increase (Decrease) in Unrecognized Losses in AOCE in comparable periods.

+ References

No definition available.

+ Details

Name:	gww_IncreaseDecreaseinUnrecognizedLossesinAOCE
Namespace Prefix:	gww_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the amortization period in years for unrecognized gains (losses) included in net periodic benefits costs, which is based on the average remaining service period for active plan participants expected to retire and receive benefits.

+ References

No definition available.

+ Details

Name:	gww_NetUnrecognizedGainsLossesAmortizationPeriod
Namespace Prefix:	gww_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Profit Sharing Automatic Contribution By Employer, Percentage

+ References

No definition available.

+ Details

Name:	gww_ProfitSharingAutomaticContributionByEmployerPercentage
Namespace Prefix:	gww_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The contribution percentage range of total eligible compensation paid to all eligible employees under the Company's amended noncontributory profit sharing plan.

+ References

No definition available.

+ Details

Name:	gww_ProfitSharingContributionPercentage
Namespace Prefix:	gww_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (i-k)
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669646-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580

+ Details

Name:	us-gaap_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTaxAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, before tax, of accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (j)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580

+ Details

Name:	us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, before tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (j)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanActualReturnOnPlanAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanActuarialGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of prior service cost (credit) recognized in net periodic benefit cost (credit) of defined benefit plan.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_DefinedBenefitPlanAmountsThatWillBeAmortizedFromAccumulatedOtherComprehensiveIncomeLossInNextFiscalYearAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of defined benefit plan.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanBenefitObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 60
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)(6)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanBenefitObligationBenefitsPaid
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of contributions received by defined benefit plan from participant which increase benefit obligation.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanBenefitObligationContributionsByPlanParticipant
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointChangeInAssumedHealthCareCostTrendRatesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of decrease in accumulated postretirement benefit obligation from one-percentage-point decrease in assumed health care cost trend rate.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnAccumulatedPostretirementBenefitObligation1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of decrease in service and interest cost components of net periodic postretirement benefit cost from one-percentage-point decrease in assumed health care cost trend rate.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnServiceAndInterestCostComponents1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of increase in accumulated postretirement benefit obligation from one-percentage-point increase in assumed health care cost trend rate.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnAccumulatedPostretirementBenefitObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of increase in service and interest cost components of net periodic postretirement benefit cost from one-percentage-point increase in assumed health care cost trend rate.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnServiceAndInterestCostComponents
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_DefinedBenefitPlanEstimatedFutureBenefitPaymentsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of cost (credit) included in accumulated other comprehensive (income) loss expected to be recognized in net periodic benefit cost (credit) for fiscal year following most recent annual statement of financial position.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanExpectedAmortizationNextFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount included in accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan expected to be recognized in net periodic benefit (cost) credit for fiscal year following most recent annual statement of financial position.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanExpectedAmortizationOfGainLossNextFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount included in accumulated other comprehensive (income) loss for prior service cost (credit) expected to be recognized in net periodic benefit cost (credit) for fiscal year following most recent annual statement of financial position.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanExpectedAmortizationOfPriorServiceCostCreditNextFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of benefits for defined benefit plan expected to be paid in five fiscal years after fifth fiscal year following latest fiscal year.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of benefits for defined benefit plan expected to be paid in next fiscal year following latest fiscal year.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of benefits for defined benefit plan expected to be paid in fifth fiscal year following latest fiscal year.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of benefits for defined benefit plan expected to be paid in fourth fiscal year following latest fiscal year.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of benefits for defined benefit plan expected to be paid in third fiscal year following latest fiscal year.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of benefits for defined benefit plan expected to be paid in second fiscal year following latest fiscal year.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of cost recognized for passage of time related to defined benefit plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)(2)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanInterestCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of net periodic benefit cost (credit) for defined benefit plan.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of defined benefit plan cost (credit), classified as other.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedBenefitPlanOtherCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of increase (decrease) in benefit obligation of defined benefit plan from change in terms of existing plan or initiation of new plan.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanPlanAmendments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of payment to participant under defined benefit plan which decreases plan assets. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 60
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(5)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanPlanAssetsBenefitsPaid
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of contributions received by defined benefit plan from participant which increases plan assets.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanPlanAssetsContributionsByPlanParticipant
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)(1)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanServiceCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Ultimate trend rate for health care cost for defined benefit postretirement plan.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanUltimateHealthCareCostTrendRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingBenefitObligationAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingNetPeriodicBenefitCostAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Year ultimate health care cost trend rate is expected to be reached, in CCYY format.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanYearHealthCareCostTrendRateReachesUltimateTrendRate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of cost for defined contribution plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

+ Details

Name:	us-gaap_DefinedContributionPlanCostRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of tax expense (benefit) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e640-108580

+ Details

Name:	us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of cost (reversal of cost) for pension and other postretirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(b)(4))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(b)(2))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

+ Details

Name:	us-gaap_PensionAndOtherPostretirementBenefitExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_PensionAndOtherPostretirementBenefitExpenseAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of liability, recognized in statement of financial position, for defined benefit pension and other postretirement plans, classified as noncurrent.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64852052&loc=d3e1731-114919

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(24))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64852052&loc=d3e1703-114919

+ Details

Name:	us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=gww_PlanAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=gww_FidelitySpartanUSEquityIndexFundMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=gww_Vanguard500IndexFundMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=gww_VanguardTotalInternationalStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=gww_TotalRegisteredInvestmentCompaniesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

EMPLOYEE BENEFITS - Postretirement Benefits (Details) $ in Thousands		12 Months Ended
	Aug. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Profit Sharing Automatic Contribution By Employer, Percentage		3.00%
Decrease in postretirement benefit obligation	$ 75,700
Postretirement benefit plan re-measurement, tax	29,200
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Plan amendment	$ (75,700)
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
HRA credit inflation index for grandfathered retirees		0.0250
Defined Benefit Plan, Estimated Future Benefit Payments [Abstract]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		$ 120,000	$ 84,000	$ 121,000
Defined Contribution Plan, Cost		18,000	12,000	11,000
Postretirement Benefits [Member]
Decrease in postretirement benefit obligation		34,182	0
Postretirement Benefits
Service cost		7,423	8,238	10,128
Interest cost		8,103	9,855	9,649
Expected return on assets		(11,826)	(10,113)	(10,375)
Amortization of prior service credits		(7,570)	(6,688)	(6,801)
Amortization of unrecognized losses		(2,437)	129	1,512
Net periodic benefit costs		(6,307)	1,421	4,113
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year		265,028	239,348
Service cost		7,423	8,238	10,128
Interest cost		8,103	9,855	9,649
Plan participants' contributions		3,346	2,943
Actuarial (gains) losses		(34,236)	13,218
Plan amendment		(34,182)	0
Benefits paid		(8,631)	(9,439)
Prescription drug rebates		1,499	865
Benefit obligation at end of year		208,350	265,028	$ 239,348
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Prescription drug rebates		1,499	865
Noncurrent postretirement benefit obligation		18,858	101,483
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax [Abstract]
Prior service credit		80,426	53,814
Unrecognized gains (losses)		36,794	(12,656)
Deferred tax (liability)		(43,793)	(15,861)
Net accumulated gains		73,427	$ 25,297
Increase in unrecognized Losses in AOCE		49,000
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year [Abstract]
Amortization of prior service credit		(9,696)
Amortization of unrecognized gains		(2,787)
Estimated amount to be amortized from AOCE into net periodic postretirement benefit costs		$ (12,483)
Net unrecognized gains (losses), amortization period		13 years 2 months 12 days
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate		4.00%	4.20%	3.89%
Long-term rate of return on plan assets, net of tax		7.13%	6.65%	6.65%
Initial healthcare cost trend rate - pre age 65		0.0681	0.0700	0.0725
Initial healthcare cost trend rate, post age 65		0.0936	0.0700	0.0725
Ultimate healthcare cost trend rate		4.50%	4.50%	4.50%
Year ultimate healthcare cost trend rate reached		2026	2026	2026
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate		3.44%	4.00%	4.20%
Expected long-term rate of return on plan assets, net of tax		7.13%	7.13%	6.65%
Initial healthcare cost trend rate - pre age 65		6.56%	6.81%	7.00%
Initial healthcare cost trend rate - post age 65			9.36%	7.00%
Catastrophic drug benefit		0.1250
Ultimate healthcare cost trend rate		4.50%	4.50%	4.50%
Year ultimate healthcare cost trend rate reached		2026	2026	2026
Defined Benefit Plan, Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rate [Abstract]
Effect of one percentage point increase on service and interest cost		$ 1,269
Effect of one percentage point decrease on service and interest cost		(1,053)
Effect of one percentage point increase on postretirement benefit obligation		5,516
Effect of one percentage point decrease on postretirement benefit obligation		(5,095)
Defined Benefit Plan, Estimated Future Benefit Payments [Abstract]
Estimated gross benefit payments, 2018		7,365
Estimated gross benefit payments, 2019		8,956
Estimated gross benefit payments, 2020		10,029
Estimated gross benefit payments, 2021		11,025
Estimated gross benefit payments, 2022		12,077
Estimated gross benefit payments, 2023-2027		67,760
Postretirement Benefits [Member] \| Plan Assets [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Prescription drug rebates		1,499	$ 865
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets available for benefits at beginning of year		163,545	155,611
Actual returns on plan assets		29,477	13,557
Plan participants' contributions		3,266	2,774
Benefits paid		(8,295)	(9,262)
Prescription drug rebates		1,499	865
Plan assets available for benefits at end of year		189,492	163,545	$ 155,611
Postretirement Benefits [Member] \| Fidelity Spartan US Equity Index Fund [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets available for benefits at beginning of year		70,950
Plan assets available for benefits at end of year		83,238	70,950
Postretirement Benefits [Member] \| Vanguard 500 Index Fund [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets available for benefits at beginning of year		87,587
Plan assets available for benefits at end of year		103,706	87,587
Postretirement Benefits [Member] \| Vanguard Total International Stock Member \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets available for benefits at beginning of year		24,056
Plan assets available for benefits at end of year		30,684	24,056
Postretirement Benefits [Member] \| Total Registered Investment Companies [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Trust liabilities		(28,136)	(19,048)
Postretirement Benefits [Member] \| Total Registered Investment Companies [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets available for benefits at beginning of year		182,593
Plan assets available for benefits at end of year		$ 217,628	$ 182,593
Minimum [Member]
Defined Benefit Plan, Estimated Future Benefit Payments [Abstract]
Profit Sharing Contribution Percentage		8.00%
Maximum [Member]
Defined Benefit Plan, Estimated Future Benefit Payments [Abstract]
Profit Sharing Contribution Percentage		18.00%