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

Third level of employer's automatic contribution to a defined contribution plan, expressed as a percentage of employees' eligible compensation, based on eligibility to participate in the plan as of a specified date.

No definition available.

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

Second level of employer's automatic contribution to a defined contribution plan, expressed as a percentage of employees' eligible compensation, based on eligibility to participate in the plan as of a specified date.

No definition available.

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

Percentage of employees' eligible compensation for which the employer contributes a matching contribution to a defined contribution plan for employees hired prior to a specified date.

No definition available.

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

Percentage of employees' eligible compensation for which the employer contributes a matching contribution to a defined contribution plan for employees hired on or subsequent to a specified date.

No definition available.

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

The minimum service period after which employees receive automatic contributions and matching contributions to a defined contribution plan.

No definition available.

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

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.

No definition available.

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

Name:	us-gaap_RetirementPlanNameAxis=ibm_IBM401kPlusPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RetirementPlanTaxStatusAxis=us-gaap_NonqualifiedPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RetirementPlanNameAxis=ibm_IBMExcess401kPlusPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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