The amount of pension funds allocated to portfolio, which are available for future investments.

No definition available.

Name:	ibm_DefinedBenefitPlanAmountAvailableForFutureInvestments
Namespace Prefix:	ibm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The net increase or decrease in the accumulated plan benefit obligation, during the reporting period, on account of changes in discount rate assumptions.

+ References

No definition available.

+ Details

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

- Definition

The net increase or decrease in the plan benefit obligation, during the reporting period, on account of changes in discount rate assumptions.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

The increase (decrease) in the net periodic income (cost), due to changes in discount rate assumptions.

+ References

No definition available.

+ Details

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- Definition

The increase (decrease) in net periodic (income) cost due to change in interest crediting rate.

+ References

No definition available.

+ Details

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

- Definition

This element represents the increase (decrease) in healthcare cost trend rate of defined benefit plan assumed over the next four years.

+ References

No definition available.

+ Details

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Namespace Prefix:	ibm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the interest crediting rate.

+ References

No definition available.

+ Details

Name:	ibm_DefinedBenefitPlanInterestCreditingRate
Namespace Prefix:	ibm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	ibm_DiscountRateAbstract
Namespace Prefix:	ibm_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

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Balance Type:	na
Period Type:	duration

- Definition

This element represents the number of years over which changes in the fair value of plan assets in the expected return on plan assets line in net periodic (Income)/cost is systematically recognized.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

The percentage of board members, elected by employees and retirees for managing investments.

+ References

No definition available.

+ Details

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Namespace Prefix:	ibm_
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Balance Type:	na
Period Type:	duration

- Definition

This element represents percentage of interest rate added to average from August to October of the one-year U.S. Treasury Constant Maturity yield for computation of interest crediting rate.

+ References

No definition available.

+ Details

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Namespace Prefix:	ibm_
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- Details

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- Details

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- Definition

The interest rate used to adjust for the time value of money for the plan.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph j

-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 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(1)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

+ Details

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- Definition

Expected rate of compensation increases (for pay-related plans).

+ References

+ Details

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- Definition

The interest rate used to adjust for the time value of money.

+ References

+ Details

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- Definition

An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(3)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 87

-Paragraph 264

-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 132R

-Paragraph 5

-Subparagraph j

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Expected Long-Term Rate of Return on Plan Assets

-URI http://asc.fasb.org/extlink&oid=6512013

+ Details

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- Definition

Expected rate of compensation increases (for pay-related plans).

+ References

+ Details

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- Definition

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Section 35

-Paragraph 50

-URI http://asc.fasb.org/extlink&oid=6867990&loc=d3e12355-114930

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 87

-Paragraph 49

-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 132R

-Paragraph 5

-Subparagraph d(iv)(b)(i)

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-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.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

+ Details

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- Definition

The assumed health care cost trend rate for the next year used to measure the expected cost of benefits covered by the plan (gross eligible charges). This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status.

+ References

+ Details

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- Definition

Target allocation of investments of this type to total plan assets presented on a weighted average basis.

+ References

+ Details

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- Definition

Percentage of fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of plan assets held.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 5

-Subparagraph (c)

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (d)(1)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph d(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.

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- Details

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Retirement-Related Benefits (Details 5) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
U.S. Plan(s) \| Sovereign Debt
Investment Policies And Strategies
Fair Value of Plan Assets	$ 847
Non-U.S. Plans \| Italy Spain and Ireland \| Maximum
Investment Policies And Strategies
Fair value of plan assets as percent of total non-US plan assets	1.00%
Non-U.S. Plans \| Sovereign Debt
Investment Policies And Strategies
Fair Value of Plan Assets	11,000
Defined Benefit Pension Plans
Discount Rate
Period over which changes in fair value of plan assets recognized	5 years
Defined Benefit Pension Plans \| U.S. Plan(s)
Weighted-average assumptions used to measure net periodic (income)/cost for the year ended December 31
Discount rate (as a percent)	4.20%	5.00%	5.60%
Expected long-term returns on plan assets (as a percent)	8.00%	8.00%	8.00%
Weighted-average assumptions used to measure benefit obligations at December 31
Discount rate (as a percent)	3.60%	4.20%	5.00%
Discount Rate
Increase (decrease) in net periodic income (cost) due to change in discount rate	(258)	(171)	(40)
Increase in projected benefit obligation due to change in discount rate	3,414	4,216
Investment Policies And Strategies
Fair Value of Plan Assets	53,630	51,218	50,259
Defined Benefit Pension Plans \| Non-U.S. Plans
Weighted-average assumptions used to measure net periodic (income)/cost for the year ended December 31
Discount rate (as a percent)	4.28%	4.33%	4.84%
Expected long-term returns on plan assets (as a percent)	6.26%	6.41%	6.56%
Rate of compensation increase (as a percent)	2.43%	2.37%	2.92%
Weighted-average assumptions used to measure benefit obligations at December 31
Discount rate (as a percent)	3.23%	4.28%	4.33%
Rate of compensation increase (as a percent)	2.51%	2.43%	2.37%
Investment Policies And Strategies
Percentage of board members, elected by employees and retirees for managing investments (as a percent)	50.00%
Fair Value of Plan Assets	38,058	35,362	35,722
Defined Benefit Pension Plans \| Non-U.S. Plans \| Equity securities
Investment Policies And Strategies
Target allocation (as a percent)	35.00%
Defined Benefit Pension Plans \| Non-U.S. Plans \| Fixed income:
Investment Policies And Strategies
Target allocation (as a percent)	54.00%
Defined Benefit Pension Plans \| Non-U.S. Plans \| Private real estate
Investment Policies And Strategies
Target allocation (as a percent)	2.00%
Defined Benefit Pension Plans \| Non-U.S. Plans \| Other securities
Investment Policies And Strategies
Target allocation (as a percent)	9.00%
Personal Pension Plan (PPP)
Interest Crediting Rate
Percentage interest rate added to average interest from August to October of the one-year U.S Treasury Constant Maturity yield for computation of interest crediting rate (as a percent)	1.00%	1.00%
Interest crediting rate (as a percent)	1.10%	1.30%	1.40%	2.80%
Increase (decrease) in net periodic (income) cost due to change in interest crediting rate	10	4	62
Qualified PPP (Qualified defined benefit pension plans) \| U.S. Plan(s)
Investment Policies And Strategies
Commitments for future investments in private markets	2,509
Fair Value of Plan Assets	53,630	51,218
Qualified PPP (Qualified defined benefit pension plans) \| U.S. Plan(s) \| Equity securities
Investment Policies And Strategies
Target allocation (as a percent)	43.00%
Qualified PPP (Qualified defined benefit pension plans) \| U.S. Plan(s) \| Fixed income:
Investment Policies And Strategies
Target allocation (as a percent)	47.00%
Qualified PPP (Qualified defined benefit pension plans) \| U.S. Plan(s) \| Private real estate
Investment Policies And Strategies
Target allocation (as a percent)	5.00%
Qualified PPP (Qualified defined benefit pension plans) \| U.S. Plan(s) \| Other securities
Investment Policies And Strategies
Target allocation (as a percent)	5.00%
Qualified PPP (Qualified defined benefit pension plans) \| U.S. Plan(s) \| Private equities and private real estate investments
Investment Policies And Strategies
Fair Value of Plan Assets	6,946
Nonpension Postretirement Plans
Discount Rate
Increase in accumulated projected benefit obligation due to change in discount rate	252	359
Healthcare Cost Trend Rate
Health care cost trend rate assumed for next fiscal year (as a percent)	7.00%
Health care cost trend rate assumed over the next four years (as a percent)	5.00%
Nonpension Postretirement Plans \| U.S. Plan(s)
Weighted-average assumptions used to measure net periodic (income)/cost for the year ended December 31
Discount rate (as a percent)	3.90%	4.80%	5.40%
Weighted-average assumptions used to measure benefit obligations at December 31
Discount rate (as a percent)	3.30%	3.90%	4.80%
Investment Policies And Strategies
Fair Value of Plan Assets	433	38	35
Nonpension Postretirement Plans \| Non-U.S. Plans
Weighted-average assumptions used to measure net periodic (income)/cost for the year ended December 31
Discount rate (as a percent)	7.37%	7.75%	7.92%
Expected long-term returns on plan assets (as a percent)	9.01%	9.07%	9.16%
Weighted-average assumptions used to measure benefit obligations at December 31
Discount rate (as a percent)	6.43%	7.37%	7.75%
Investment Policies And Strategies
Fair Value of Plan Assets	$ 119	$ 112	$ 120