Early termination fees associated with a debt agreement.

No definition available.

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

- Definition

The number of tranches in which aggregate debt issued.

+ References

No definition available.

+ Details

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Namespace Prefix:	ibm_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the fee for available but unused credit capacity under the credit facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=ibm_BridgeLoanCreditFacility2018Member
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_NotesPayableOtherPayablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=ibm_NotesPayableOtherPayablesTrancheOneMember
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
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Data Type:	na
Balance Type:
Period Type:

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Name:	us-gaap_DebtInstrumentAxis=ibm_NotesPayableOtherPayablesTrancheTwoMember
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Name:	us-gaap_DebtInstrumentAxis=ibm_NotesPayableOtherPayablesTrancheThreeMember
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Name:	us-gaap_DebtInstrumentAxis=ibm_NotesPayableOtherPayablesTrancheSixMember
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Borrowings - Long-Term Debt, Debt Issued (Details)			3 Months Ended
Borrowings - Long-Term Debt, Debt Issued (Details)	May 19, 2019 USD ($)	May 15, 2019 USD ($) tranche	Dec. 31, 2018 USD ($)
Lines of Credit
Lines of Credit
Early termination fees	$ 0
364-Day Bridge Facility
Lines of Credit
Term of debt instrument			364 days
Amount of credit facility			$ 20,000,000,000
Fees related to the credit facility			$ 60,000,000
Long-term Debt Instrument
Lines of Credit
Aggregate amount of debt issued		$ 20,000,000,000
Number of tranches of facility \| tranche		8
Tranche One
Lines of Credit
Term of debt instrument		2 years
Aggregate amount of debt issued		$ 1,500,000,000
Tranche One \| 3 month LIBOR
Lines of Credit
Basis points		0.40%
Tranche Two
Lines of Credit
Term of debt instrument		2 years
Aggregate amount of debt issued		$ 1,500,000,000
Coupon rate (as a percentage)		2.80%
Tranche Three
Lines of Credit
Term of debt instrument		3 years
Aggregate amount of debt issued		$ 2,750,000,000
Coupon rate (as a percentage)		2.85%
Tranche Four
Lines of Credit
Term of debt instrument		5 years
Aggregate amount of debt issued		$ 3,000,000,000.0
Coupon rate (as a percentage)		3.00%
Tranche Five
Lines of Credit
Term of debt instrument		7 years
Aggregate amount of debt issued		$ 3,000,000,000.0
Coupon rate (as a percentage)		3.30%
Tranche Six
Lines of Credit
Term of debt instrument		10 years
Aggregate amount of debt issued		$ 3,250,000,000
Coupon rate (as a percentage)		3.50%
Tranche Seven
Lines of Credit
Term of debt instrument		20 years
Aggregate amount of debt issued		$ 2,000,000,000.0
Coupon rate (as a percentage)		4.15%
Tranche Eight
Lines of Credit
Term of debt instrument		30 years
Aggregate amount of debt issued		$ 3,000,000,000.0
Coupon rate (as a percentage)		4.25%