SUBSEQUENT EVENTS (Details) - Subsequent events - USD ($) $ / shares in Units, $ in Millions	Feb. 06, 2018	Jan. 30, 2018
Subsequent Events:
Dividend declared (in dollars per share)		$ 1.50
Dividend declared, date		Jan. 30, 2018
Dividend payable, date		Mar. 10, 2018
Shareholders of record, date		Feb. 09, 2018
Bonds issued in February 2018 \| IBM Credit LLC
Subsequent Events:
Bonds issued	$ 2,000
3-year bonds issued in February 2018 \| IBM Credit LLC \| Floating rate debt securities
Subsequent Events:
Bonds issued	$ 450
Term of debt instrument	3 years
3-year bonds issued in February 2018 \| IBM Credit LLC \| Floating rate debt securities \| LIBOR
Subsequent Events:
Variable interest added to basis (as a percent)	0.16%
3-year bonds issued in February 2018 \| IBM Credit LLC \| Fixed rate debt securities
Subsequent Events:
Bonds issued	$ 800
Term of debt instrument	3 years
Coupon rate (as a percent)	2.65%
5-year bonds issued in February 2018 \| IBM Credit LLC \| Fixed rate debt securities
Subsequent Events:
Bonds issued	$ 750
Term of debt instrument	5 years
Coupon rate (as a percent)	3.00%

Aggregate dividends declared during the period for each share of common stock outstanding.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Topic 835
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-Section 45
-Paragraph 2
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Contractual interest rate for funds borrowed, under the debt agreement.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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Date the declared dividend will be paid, in CCYY-MM-DD format.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586

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Date the dividend to be paid was declared, in CCYY-MM-DD format.

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Date the holder must own the stock to be entitled to the dividend, in CCYY-MM-DD format.

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Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

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