Financial Instruments (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011 basispoint	Dec. 31, 2010
Derivative Financial Instruments
Derivative instruments with credit-risk related contingent features	$ 131	$ 363
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	1,300	1,099
Fair value of total derivative instruments, Liabilities	2,415	3,576
Collateral posted for derivative instruments with credit-risk related contingent features		9
Maximum spread on credit default swap agreements before full overnight collateralization is required (in basis points)	250
Liabilities included in master netting arrangements	324	475
Collateral received for derivative instruments with credit-risk related contingent features	466	88
Cash collateral related to all applicable derivative instruments recorded in other receivables		9
Amounts recognized in accounts payable for the obligation to return cash collateral	466	88
Cash collateral rehypothecated		9
Derivative instruments designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	1,190	794
Fair value of total derivative instruments, Liabilities	428	633
Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	110	305
Fair value of total derivative instruments, Liabilities	103	373
Prepaid expenses and other current assets \| Interest rate contracts \| Derivative instruments designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	50	33
Prepaid expenses and other current assets \| Foreign exchange contracts \| Derivative instruments designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	407	224
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	82	242
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	7	12
Investments and sundry assets \| Interest rate contracts \| Derivative instruments designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	733	514
Investments and sundry assets \| Foreign exchange contracts \| Derivative instruments designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets		22
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	21	51
Long term debt. \| Derivative instruments designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	1,884	1,746
Other accrued expenses and liabilities \| Foreign exchange contracts \| Derivative instruments designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	273	498
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	84	370
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	8	3
Other liabilities. \| Foreign exchange contracts \| Derivative instruments designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	155	135
Other liabilities. \| Foreign exchange contracts \| Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	11
Short term debt \| Derivative instruments designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities		$ 823

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

No definition available.

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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

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- Definition

The fair value, as of the date of each statement of financial position presented, of accounts payable which are collateral received for the repayment of the related debt obligation, and that are reclassified and separately reported in the statement of financial position.

+ References

No definition available.

+ Details

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Namespace Prefix:	ibm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of the obligation to return cash collateral under master netting arrangements that have not been offset against net derivative instrument positions.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=6935481&loc=d3e41678-113959

-Subparagraph (b)

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- Definition

The amount of the right to reclaim cash collateral under master netting arrangements that have not been offset against net derivative instrument positions.

+ References

+ Details

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- Definition

Fair value of derivative asset, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (a),(c)

-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5624163-113959

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 44C

-Subparagraph a

-Clause 1

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 205G

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

Fair value of derivative liability, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

+ References

+ Details

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Balance Type:	credit
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- Definition

The amount as of the balance sheet date of the fair value of derivative liabilities that in accordance with the entity's accounting policy was not offset against the right to reclaim cash collateral under a master netting arrangement.

+ References

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FIN39-1

-Paragraph 10B

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 8

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6935481&loc=d3e41678-113959

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- 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=6935481&loc=SL5624258-113959

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 44D

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Details

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- Definition

The fair value, as of the date of each statement of financial position presented, of other assets which are owned but transferred to serve as collateral for the payment of the related debt obligation, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 140

-Paragraph 15

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6467456&loc=d3e113888-111728

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