Segments: (Segment reconciliations) (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Pre-tax Income
Income before income taxes	$ 5,171	$ 4,144	$ 8,151	$ 7,750
Total reportable segments
Pre-tax Income
Income before income taxes	5,983	4,989	9,812	9,425
Pre-tax reconciliations items
Pre-tax Income
Amortization of acquired intangible assets	(200)	(178)	(395)	(361)
Acquisition-related charges	(4)	(4)	(10)	(15)
Non-operating retirement-related (costs)/income	(52)	(262)	(175)	(546)
Eliminations of internal transactions
Pre-tax Income
Income before income taxes	(507)	(379)	(1,031)	(718)
Unallocated corporate amounts
Pre-tax Income
Income before income taxes	$ (50)	$ (22)	$ (50)	$ (35)

Charges excluded from segment pre-tax income including: acquisition-related in-process research and development, transaction costs, applicable restructuring and tax charges related to acquisition integration.

No definition available.

+ Details

Name:	ibm_AcquisitionRelatedCharges
Namespace Prefix:	ibm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The aggregate expense charged against earnings to allocate the cost of acquired intangible assets.

+ References

No definition available.

+ Details

Name:	ibm_AmortizationAcquiredIntangibleAssets
Namespace Prefix:	ibm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Income and charges excluded from operating earnings and segment pre-tax income including: defined benefit plan and other postretirement benefit plan interest cost, expected return on plan assets, amortized actuarial gains/losses, the impacts of any plan curtailments/settlements, multi-employer pension costs and insolvency insurance costs.

+ References

No definition available.

+ Details

Name:	ibm_NonoperatingRetirementRelatedCosts
Namespace Prefix:	ibm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 10

-Article 5

+ Details

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

- Details

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