Fee income earned from related parties related to financing incentives to a third party.

No definition available.

Name:	ibmc_FeeIncomeFromRelatedPartyRelatedToFinancingIncentivesToThirdParty
Namespace Prefix:	ibmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The change from year to year in the fee income earned from related parties.

+ References

No definition available.

+ Details

Name:	ibmc_RelatedPartyInformationFeeIncomeChange
Namespace Prefix:	ibmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The increase (decrease) in finance income earned from a related party over the prior year.

+ References

No definition available.

+ Details

Name:	ibmc_RelatedPartyInformationFinancialServicesRevenueChange
Namespace Prefix:	ibmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The increase (decrease) in interest income earned from a related party over the prior year.

+ References

No definition available.

+ Details

Name:	ibmc_RelatedPartyInformationInterestIncomeChange
Namespace Prefix:	ibmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of revenue earned from financing of related party trade receivables.

+ References

No definition available.

+ Details

Name:	ibmc_TradeReceivableFinanceRevenueFromRelatedParty
Namespace Prefix:	ibmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

For an unclassified balance sheet, amount of receivables due from an entity that is affiliated with the reporting entity by means of direct or indirect ownership.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39599-107864

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(k)(1))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.3)
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39622-107864

+ Details

Name:	us-gaap_DueFromAffiliates
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of interest income earned from interest-bearing assets owed to the entity by related party.

+ References

No definition available.

+ Details

Name:	us-gaap_InterestIncomeRelatedParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919230-210447

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=118952595&loc=d3e4428-111522

+ Details

Name:	us-gaap_NotesReceivableNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

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

- Details

Name:	us-gaap_IncomeStatementLocationAxis=ibmc_FinancialServicesRevenueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=ibmc_LoansAndLeasesReceivableFromRelatedPartyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=ibmc_LongTermParticipatedReceivablesFromRelatedPartyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=ibmc_ShortTermPurchasedReceivablesFromRelatedPartyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=ibmc_InternationalBusinessMachinesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=ibmc_ExcessCashInShortTermInterestBearingAccountsWithParentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Relationship with IBM and Related Party Transactions - Operating Relationship (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Disclosures
Other receivables from IBM	$ 742		$ 513
Financing revenue
Disclosures
Fee income from related party related to financing incentives to third party	41
Change in fee income	(7)
Financing receivables from IBM
Disclosures
Net financing receivables	3,771		3,870
Long-term participated receivables from IBM
Disclosures
Net financing receivables	4,186		4,303
Short-term purchased receivables from IBM
Disclosures
Net financing receivables	72		56
IBM
Disclosures
Other receivables from IBM	742		513
IBM \| Excess cash in short-term interest-bearing accounts with parent
Disclosures
Other receivables from IBM	736		$ 509
IBM \| Financing revenue \| Excess cash in short-term interest-bearing accounts with parent
Disclosures
Interest income from a related party	2	$ 8
IBM \| Financing receivables from IBM \| Financing revenue
Disclosures
Interest income from a related party	34
Increase (decrease) in interest income over the prior year	(10)
IBM \| Long-term participated receivables from IBM \| Financing revenue
Disclosures
Interest income from a related party	51
Increase (decrease) in financial services revenue over the prior year	1
IBM \| Short-term purchased receivables from IBM \| Financing revenue
Disclosures
Financing revenue	4
Increase (decrease) in financial services revenue over the prior year	$ (11)