Borrowings - Long-Term Debt, Covenants (Details) $ in Millions	9 Months Ended
Sep. 30, 2018 USD ($)
Borrowings
Limit based on net tangible assets	10.00%
Credit Facilities
Borrowings
Minimum net interest expense ratio	2.20
Default provision on credit facility	$ 500

The limit on secured indebtedness and sale and leaseback transactions expressed as a percentage of the company's consolidated net tangible assets. This limit is part of covenant contained in the company's indentures which govern its debt securities and various credit facilities.

No definition available.

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