Financial Instruments: (Details 3) (USD $) In Millions, unless otherwise specified	6 Months Ended
Jun. 30, 2013 basispoint	Dec. 31, 2012
Financial Instruments:
Derivative instruments with credit-risk related contingent features	$ 55	$ 94
Collateral posted on derivative instruments	0	0
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	937	918
Fair value of total derivative liabilities and debt	3,883	4,116
Maximum spread on credit default swap agreements before full overnight collateralization is required (in basis points)	250
Liabilities included in master netting arrangements	256	262
Cash collateral received, derivatives	33	69
Net exposure related to derivative assets recorded in the Statement of Financial Position	648	587
Net amount related to derivative liabilities recorded in the Statement of Financial Position	225	242
Non-cash collateral received and not recorded on the Statement of Financial Position	0	31
Cash collateral rehypothecated	0	0
Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	785	744
Fair value of total derivative instruments, Liabilities	265	345
Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	152	174
Fair value of total derivative instruments, Liabilities	216	159
Other receivables
Fair Values of Derivative Instruments
Cash collateral issued, derivatives	0	0
Accounts payable
Fair Values of Derivative Instruments
Cash collateral received, derivatives	33	69
Prepaid expenses and other current assets \| Interest rate contracts \| Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	26	47
Prepaid expenses and other current assets \| Foreign exchange contracts \| Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	393	135
Prepaid expenses and other current assets \| Foreign exchange contracts \| Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	133	142
Prepaid expenses and other current assets \| Equity contracts \| Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	1	9
Investments and sundry assets \| Interest rate contracts \| Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	366	557
Investments and sundry assets \| Foreign exchange contracts \| Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets		5
Investments and sundry assets \| Foreign exchange contracts \| Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	18	23
Other accrued expenses and liabilities \| Foreign exchange contracts \| Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	150	267
Other accrued expenses and liabilities \| Foreign exchange contracts \| Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	183	152
Other accrued expenses and liabilities \| Equity contracts \| Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	33	7
Other liabilities \| Foreign exchange contracts \| Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	115	78
Long term debt \| Designated as hedging instruments \| Net investment hedge
Fair Values of Derivative Instruments
Debt designated as hedging instrument	2,226	3,035
Short term debt \| Designated as hedging instruments \| Net investment hedge
Fair Values of Derivative Instruments
Debt designated as hedging instrument	$ 1,176	$ 578

This item represents the amount of cash collateral rehypothecated as of the balance sheet date.

No definition available.

Name:	ibm_CashCollateralRehypothecated
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The credit default swap spread which, if exceeded, would trigger contingent features of these agreements.

+ References

No definition available.

+ Details

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

- Definition

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4H

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624258-113959

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- Definition

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

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-Publisher FASB

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-Name Accounting Standards Codification

-Topic 210

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-Paragraph 3

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-Publisher FASB

-Name Accounting Standards Codification

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-Publisher FASB

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-Topic 210

-SubTopic 20

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-URI http://asc.fasb.org/extlink&oid=28370219&loc=SL20226008-175313

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 55

-Paragraph 13

-URI http://asc.fasb.org/extlink&oid=28370219&loc=SL20226016-175313

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

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-Paragraph 3

-Subparagraph (d)(2)

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 8

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=d3e41678-113959

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of obligation to return securities collateral under master netting arrangements that have not been offset against derivative assets.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of right to receive cash collateral under master netting arrangements that have not been offset against derivative liabilities.

+ References

+ Details

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

- Definition

Fair value before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

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-Paragraph 7

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-SubTopic 10

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-Paragraph 4B

-Subparagraph (a),(c)

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+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Fair value before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, elected not to be offset against a right to receive collateral under a master netting arrangement.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

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-Paragraph 3

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Namespace Prefix:	us-gaap_
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Balance Type:	credit
Period Type:	instant

- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

+ Details

Name:	us-gaap_DerivativeLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4H

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624258-113959

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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- Definition

Fair value of financial obligations, including, but not limited to, debt instruments, derivative liabilities, federal funds purchased and sold under agreements to repurchase, securities loaned or sold under agreements to repurchase, financial instruments sold not yet purchased, guarantees, line of credit, loans and notes payable, servicing liability, and trading liabilities.

+ References

No definition available.

+ Details

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Balance Type:	credit
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- Details

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