Represents a number of years ago an outdated pension plan was elected to forego by employees.

No definition available.

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

- Definition

Represents the period for which reports need to be submitted to Securities Exchange Commission and court on certain matters, including those relating to compliance with the Foreign Corrupt Practices Act of 1977.

+ References

No definition available.

+ Details

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

- Definition

Number of representative beneficiaries of the UK Trust membership against which the entity initiated legal proceedings.

+ References

No definition available.

+ Details

Name:	ibm_NumberOfRepresentativeBeneficiariesOfTrustMembership
Namespace Prefix:	ibm_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of judgment or settlement awarded to (against) the entity in respect of litigation.

+ References

No definition available.

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 9

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349

+ Details

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

- Definition

Number of defendants named in a legal action.

+ References

No definition available.

+ Details

Name:	us-gaap_LossContingencyNumberOfDefendants
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of pending claims pertaining to a loss contingency.

+ References

+ Details

Name:	us-gaap_LossContingencyPendingClaimsNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of countries in which the entity operates as of balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfCountriesInWhichEntityOperates
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=us-gaap_ForeignCountryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=country_BR
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LitigationCaseAxis=ibm_LitigationRelatedToDefinedBenefitAndDefinedContributionPlansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=country_ES
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LitigationCaseAxis=ibm_LitigationCaseInUnitedStatesDistrictCourtRegardingDivestingMicroelectronicsBusinessMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=ibm_IBMUKPensionsTrustMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=ibm_IBMUnitedKingdomLimitedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=ibm_CivilEnforcementActionWithSECMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=ibm_StateOfIndianaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LitigationStatusAxis=us-gaap_PendingLitigationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Contingencies (Details) $ in Millions			1 Months Ended	6 Months Ended
Contingencies (Details) $ in Millions	Jul. 25, 2013	Jul. 18, 2012 USD ($)	Feb. 13, 2014 USD ($)	Jun. 30, 2015 USD ($) Country Claim Defendant
Loss Contingencies
Clients presence in number of countries \| Country				175
Foreign Tax Authority \| Brazil
Loss Contingencies
Loss contingency, estimate of possible loss				$ 560
Litigation in Spain regarding defined benefit and defined contribution plans \| Spain
Loss Contingencies
Number of years an outdated pension plan was elected to be foregone by employees (in years)				20 years
Litigation Case In United States District Court regarding divesting Microelectronics business
Loss Contingencies
Number of defendants \| Defendant				3
Former IBM UK Defined Benefit Plan Participants \| IBM United Kingdom Limited
Loss Contingencies
Claims pending \| Claim				290
Loss contingency, estimate of possible loss				$ 250
Number of representative beneficiaries of the UK Trust membership \| Defendant				2
Civil enforcement action with the SEC
Loss Contingencies
Period for which reports are to be submitted to SEC and court on certain matters, including those relating to compliance with the FCPA	2 years
State of Indiana \| Pending Litigation
Loss Contingencies
Amount of settlement to be (paid)/received		$ 52	$ 50