Financial Instruments (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Financial Instruments:
Fair value of derivative instruments under collateralized arrangements in a liability position	$ 10	$ 21
Collateral posted on derivative instruments	0	0
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	1,991	1,432
Fair value of total derivative liabilities and debt	6,597	7,963
Maximum spread on credit default swap agreements before full collateralization is required	2.50%
Liabilities included in master netting arrangements	141	97
Obligation to return cash collateral	734	487
Net exposure related to derivative assets recorded in the Statement of Financial Position	1,070us-gaap_DerivativeAssets	817us-gaap_DerivativeAssets
Net exposure related to derivative liabilities recorded in the Statement of Financial Position	40us-gaap_DerivativeLiabilities	99us-gaap_DerivativeLiabilities
Cash collateral rehypothecated	0ibm_CashCollateralRehypothecated	0ibm_CashCollateralRehypothecated
U.S. Treasury securities
Fair Values of Derivative Instruments
Non-cash collateral received	46	31
Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	1,724	1,281
Fair value of total derivative instruments, Liabilities	58	72
Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	267	151
Fair value of total derivative instruments, Liabilities	124	125
Other receivables
Fair Values of Derivative Instruments
Cash collateral issued, derivatives	0	0
Accounts payable
Fair Values of Derivative Instruments
Obligation to return cash collateral	734	487
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	5	5
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	966	632
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	214	90
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	18	24
Investments and sundry assets \| Interest rate contracts \| Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	738	628
Investments and sundry assets \| Foreign exchange contracts \| Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	15	17
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	35	37
Investments and sundry assets \| Equity contracts \| Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	0	0
Other accrued expenses and liabilities \| Interest rate contracts \| Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	0	0
Other accrued expenses and liabilities \| Foreign exchange contracts \| Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	43	50
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	111	101
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	10	14
Other liabilities \| Interest rate contracts \| Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	0
Other liabilities \| Foreign exchange contracts \| Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	15	21
Other liabilities \| Foreign exchange contracts \| Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	3	4
Other liabilities \| Equity contracts \| Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	0	5
Long term debt \| Designated as hedging instruments \| Net investment hedge
Fair Values of Derivative Instruments
Debt designated as hedging instrument	6,416	7,766
Short term debt \| Designated as hedging instruments \| Net investment hedge
Fair Values of Derivative Instruments
Debt designated as hedging instrument		$ 0

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

No definition available.

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Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

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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=35706170&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, 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. Includes assets not subject to a master netting arrangement and elected not to be offset.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=34720828&loc=SL20225862-175312

+ 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

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13433-108611

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=34720828&loc=SL20225862-175312

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 55

-Paragraph 10

-URI http://asc.fasb.org/extlink&oid=36459792&loc=SL20226008-175313

+ Details

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Namespace Prefix:	us-gaap_
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=36459792&loc=SL20226016-175313

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (d)(2)

-URI http://asc.fasb.org/extlink&oid=34720828&loc=SL20225862-175312

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 8

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=35706170&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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Data Type:	xbrli:monetaryItemType
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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 liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

+ Details

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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. Includes liabilities not subject to a master netting arrangement and elected not to be offset.

+ References

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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, deducted from derivative liabilities.

+ References

+ Details

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Balance Type:	debit
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=35706170&loc=SL5624258-113959

+ Details

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Namespace Prefix:	us-gaap_
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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
Period Type:	instant

- Details

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- Details

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