Number of days after which receivables are considered past-due.

No definition available.

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Namespace Prefix:	ibm_
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Period Type:	duration

- Definition

The maturity tenure of derivative used in classifying the derivative as current or noncurrent.

+ References

No definition available.

+ Details

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

- Definition

This element represents minimum percentage of tax positions expected to be realized upon settlement.

+ References

No definition available.

+ Details

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

- Details

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

- Definition

Expected realization period for debt securities to be classified as current assets.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_AccountingPoliciesAbstract
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Period Type:	duration

- Definition

Face amount or stated value per share of common stock.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.29)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 30

-Article 5

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Details

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

- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_OtherIntangibleAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_SoftwareDevelopmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=ibm_BuildingEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_ComputerEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_EquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_LeaseholdImprovementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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Significant Accounting Policies (Details 5) (USD $)	12 Months Ended
Significant Accounting Policies (Details 5) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Significant Accounting Policies
Minimum percentage of likelihood of being realized upon settlement for benefits from tax positions (as a percent)	50.00%
Maturity tenure of derivative used in classifying it as current or noncurrent	12 months
Common stock, par value (in dollars per share)	$ 0.2	$ 0.2
Expected realization period for debt securities included in current assets	1 year
Number of days after which receivables are past-due	90 days
Minimum \| Restricted Stock Units
Stock-Based Compensation
Vesting period	1 year
Maximum \| Restricted Stock Units
Stock-Based Compensation
Vesting period	5 years
Capitalized software \| Maximum
Property, Plant and Equipment and Finite-Lived Intangible Assets
Estimated useful lives of intangible assets	3 years
Capitalized costs for internal-use software \| Maximum
Property, Plant and Equipment and Finite-Lived Intangible Assets
Estimated useful lives of intangible assets	2 years
Other intangible assets \| Minimum
Property, Plant and Equipment and Finite-Lived Intangible Assets
Estimated useful lives of intangible assets	1 year
Other intangible assets \| Maximum
Property, Plant and Equipment and Finite-Lived Intangible Assets
Estimated useful lives of intangible assets	7 years
Buildings \| Minimum
Property, Plant and Equipment and Finite-Lived Intangible Assets
Estimated useful lives of plant, rental machines and other property	30 years
Buildings \| Maximum
Property, Plant and Equipment and Finite-Lived Intangible Assets
Estimated useful lives of plant, rental machines and other property	50 years
Building equipment \| Minimum
Property, Plant and Equipment and Finite-Lived Intangible Assets
Estimated useful lives of plant, rental machines and other property	10 years
Building equipment \| Maximum
Property, Plant and Equipment and Finite-Lived Intangible Assets
Estimated useful lives of plant, rental machines and other property	20 years
Land improvements
Property, Plant and Equipment and Finite-Lived Intangible Assets
Estimated useful lives of plant, rental machines and other property	20 years
Plant, laboratory and office equipment \| Minimum
Property, Plant and Equipment and Finite-Lived Intangible Assets
Estimated useful lives of plant, rental machines and other property	2 years
Plant, laboratory and office equipment \| Maximum
Property, Plant and Equipment and Finite-Lived Intangible Assets
Estimated useful lives of plant, rental machines and other property	20 years
Computer equipment \| Minimum
Property, Plant and Equipment and Finite-Lived Intangible Assets
Estimated useful lives of plant, rental machines and other property	1 year 6 months
Computer equipment \| Maximum
Property, Plant and Equipment and Finite-Lived Intangible Assets
Estimated useful lives of plant, rental machines and other property	5 years
Leasehold improvements \| Maximum
Property, Plant and Equipment and Finite-Lived Intangible Assets
Estimated useful lives of plant, rental machines and other property	25 years