Financial Instruments (Details 3) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2013	Dec. 31, 2012
Financial Instruments:
Derivative instruments with credit-risk related contingent features	$ 222	$ 94
Collateral posted on derivative instruments	0	0
Derivatives, Fair Value [Line Items]
Fair value of total derivative instruments, Assets	793	918
Fair value of total derivative liabilities and debt	4,097	4,116
Maximum spread on credit default swap agreements before full overnight collateralization is required	2.50%
Liabilities included in master netting arrangements	343	262
Cash collateral received, derivatives	45	69
Net exposure related to derivative assets recorded in the Statement of Financial Position	404	587
Net amount related to derivative liabilities recorded in the Statement of Financial Position	239	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
Derivatives, Fair Value [Line Items]
Fair value of total derivative instruments, Assets	550	744
Fair value of total derivative instruments, Liabilities	528	345
Derivative instruments not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Fair value of total derivative instruments, Assets	242	174
Fair value of total derivative instruments, Liabilities	53	159
Other receivables
Derivatives, Fair Value [Line Items]
Cash collateral issued, derivatives	0	0
Accounts payable
Derivatives, Fair Value [Line Items]
Cash collateral received, derivatives	45	69
Prepaid expenses and other current assets \| Interest rate contracts \| Designated as hedging instruments
Derivatives, Fair Value [Line Items]
Fair value of total derivative instruments, Assets	41	47
Prepaid expenses and other current assets \| Foreign exchange contracts \| Designated as hedging instruments
Derivatives, Fair Value [Line Items]
Fair value of total derivative instruments, Assets	138	135
Prepaid expenses and other current assets \| Foreign exchange contracts \| Derivative instruments not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Fair value of total derivative instruments, Assets	208	142
Prepaid expenses and other current assets \| Equity contracts \| Derivative instruments not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Fair value of total derivative instruments, Assets	9	9
Investments and sundry assets \| Interest rate contracts \| Designated as hedging instruments
Derivatives, Fair Value [Line Items]
Fair value of total derivative instruments, Assets	371	557
Investments and sundry assets \| Foreign exchange contracts \| Designated as hedging instruments
Derivatives, Fair Value [Line Items]
Fair value of total derivative instruments, Assets		5
Investments and sundry assets \| Foreign exchange contracts \| Derivative instruments not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Fair value of total derivative instruments, Assets	25	23
Other accrued expenses and liabilities \| Foreign exchange contracts \| Designated as hedging instruments
Derivatives, Fair Value [Line Items]
Fair value of total derivative instruments, Liabilities	378	267
Other accrued expenses and liabilities \| Foreign exchange contracts \| Derivative instruments not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Fair value of total derivative instruments, Liabilities	47	152
Other accrued expenses and liabilities \| Equity contracts \| Derivative instruments not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Fair value of total derivative instruments, Liabilities	7	7
Other liabilities \| Foreign exchange contracts \| Designated as hedging instruments
Derivatives, Fair Value [Line Items]
Fair value of total derivative instruments, Liabilities	150	78
Long term debt \| Designated as hedging instruments \| Net investment hedge
Derivatives, Fair Value [Line Items]
Debt designated as hedging instrument	2,297	3,035
Short term debt \| Designated as hedging instruments \| Net investment hedge
Derivatives, Fair Value [Line Items]
Debt designated as hedging instrument	$ 1,219	$ 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:	num:percentItemType
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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- 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

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-Section 50

-Paragraph 10

-Subparagraph (a)

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-Name Accounting Standards Codification

-Topic 210

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-Topic 210

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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

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-Paragraph 13

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

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-Name Accounting Standards Codification

-Topic 210

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-SubTopic 10

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-Paragraph 8

-Subparagraph (b)

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

+ Details

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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

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Balance Type:	credit
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- 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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Data Type:	xbrli:monetaryItemType
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- 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

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-Paragraph 4B

-Subparagraph (a),(c)

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- 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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- 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

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- 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

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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

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- 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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