Name:	ibm_DefinedBenefitPlanChangeInAccumulatedProjectedBenefitObligationPeriodIncreaseDecrease
Namespace Prefix:	ibm_
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Period Type:	duration

The net increase or decrease in the plan benefit obligation, during the reporting period, on account of changes in discount rate assumptions.

No definition available.

Name:	ibm_DefinedBenefitPlanChangeInDiscountRateBenefitObligationPeriodIncreaseDecrease
Namespace Prefix:	ibm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The net increase/(decrease) in the plan benefit obligation, during the reporting period, on account of changes in mortality rate assumptions.

No definition available.

Name:	ibm_DefinedBenefitPlanChangeInMortalityRateAssumptionsBenefitObligationPeriodIncreaseDecrease
Namespace Prefix:	ibm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Increase (decrease) in expected long-term rate of return on plan assets due to changes in investment strategy.

No definition available.

Name:	ibm_DefinedBenefitPlanExpectedLongTermReturnsOnPlanAssetsIncreaseDecreaseDueToInvestmentStrategy
Namespace Prefix:	ibm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

This element represents the interest crediting rate.

No definition available.

Name:	ibm_DefinedBenefitPlanInterestCreditingRate
Namespace Prefix:	ibm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

No definition available.

Name:	ibm_DiscountRateAbstract
Namespace Prefix:	ibm_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

No definition available.

Name:	ibm_ExpectedLongTermReturnsOnPlanAssetsAbstract
Namespace Prefix:	ibm_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Increase (decrease) in net periodic income due to change in expected long-term rate of return on plan assets

No definition available.

Name:	ibm_IncreaseDecreaseInNetPeriodicIncomeDueToChangeInExpectedLongTermRateOfReturnOnPlanAssets
Namespace Prefix:	ibm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The increase (decrease) in the net periodic income, due to changes in discount rate assumptions.

No definition available.

Name:	ibm_IncreaseDecreaseInNetPeriodicIncomeFromChangeInDiscountRate
Namespace Prefix:	ibm_
Data Type:	xbrli:monetaryItemType
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Period Type:	duration

The increase (decrease) in net periodic income due to change in interest crediting rate.

No definition available.

Name:	ibm_IncreaseDecreaseInNetPeriodicIncomeFromChangeInInterestCreditingRate
Namespace Prefix:	ibm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

No definition available.

Name:	ibm_InterestCreditingRateAbstract
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

This element represents the number of years over which changes in the fair value of plan assets in the expected return on plan assets line in net periodic (Income)/cost is systematically recognized.

No definition available.

Name:	ibm_NumberOfYearsOverWhichChangesInFairValueOfPlanAssetsRecognizedInNetPeriodicIncomeCost
Namespace Prefix:	ibm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

This element represents percentage of interest rate added to average from August to October of the one-year U.S. Treasury Constant Maturity yield for computation of interest crediting rate.

No definition available.

Name:	ibm_PercentageOfInterestRateAddedToAverageFromAugustToOctoberOfOneYearUSTreasuryConstantMaturityYieldForComputationOfInterestCreditingRate
Namespace Prefix:	ibm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

No definition available.

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

The interest rate used to adjust for the time value of money for the plan.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(1)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

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

Expected rate of compensation increases (for pay-related plans).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(2)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

Name:	us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The interest rate used to adjust for the time value of money.

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

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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Expected Long-Term Rate of Return on Plan Assets
-URI http://asc.fasb.org/extlink&oid=6512046

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(3)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

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Expected rate of compensation increases (for pay-related plans).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(2)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

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Data Type:	num:percentItemType
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Period Type:	duration

Amount of effect of a one-percentage-point decrease in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (m)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

Name:	us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnAccumulatedPostretirementBenefitObligation1
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Data Type:	xbrli:monetaryItemType
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Amount of effect of a one-percentage-point decrease in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (m)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

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The effect of a one-percentage-point increase in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (m)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

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Period Type:	duration

The effect of a one-percentage-point increase in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (m)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

Name:	us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnServiceAndInterestCostComponents
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Data Type:	xbrli:monetaryItemType
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The assumed health care cost trend rate for the next year used to measure the expected cost of benefits covered by the plan (gross eligible charges). 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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Health Care Cost Trend Rate
-URI http://asc.fasb.org/extlink&oid=6514820

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (l)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

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

The ultimate trend rate for health care costs.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (l)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

Name:	us-gaap_DefinedBenefitPlanUltimateHealthCareCostTrendRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
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Period Type:	duration

No definition available.

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

No definition available.

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

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (l)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

Name:	us-gaap_DefinedBenefitPlanYearThatRateReachesUltimateTrendRate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	instant

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