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

Number of years for which substantially all of the loss and tax credit carryforwards are available.

No definition available.

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

Number of years for which the majority of loss and tax credit carryforwards are available.

No definition available.

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

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-6

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

Amount, before allocation of a valuation allowances, of deferred tax assets attributable to deductible tax credit carryforwards including, but not limited to, research, foreign, general business, alternative minimum tax, and other deductible tax credit carryforwards.