Segments (Details 1) $ in Millions	3 Months Ended
Mar. 31, 2016 USD ($) BusinessSegment	Mar. 31, 2015 USD ($)
Segment Information
Revenue	$ 18,684	$ 19,590
Pre-tax income/(loss) from continuing operations	$ 1,034	3,001
Number of business segments (in segments) \| BusinessSegment	5
Total Segments
Segment Information
Revenue	$ 18,619	19,523
Cognitive Solutions
Segment Information
Revenue	3,979	4,047
Global Business Services
Segment Information
Revenue	4,131	4,318
Technology Services & Cloud Platforms
Segment Information
Revenue	8,424	8,554
Systems
Segment Information
Revenue	1,675	2,142
Global Financing
Segment Information
Revenue	410	461
Business Segments \| Total Segments
Segment Information
Revenue	20,264	21,213
Pre-tax income/(loss) from continuing operations	$ 1,837	$ 4,023
Revenue year-to-year change (as a percent)	(4.50%)
Pre-tax income year-to-year change (as a percent)	(54.30%)
Pre-tax income margin (as a percent)	9.10%	19.00%
Business Segments \| Cognitive Solutions
Segment Information
Revenue	$ 4,647	$ 4,682
Pre-tax income/(loss) from continuing operations	$ 1,013	$ 1,528
Revenue year-to-year change (as a percent)	(0.80%)
Pre-tax income year-to-year change (as a percent)	(33.70%)
Pre-tax income margin (as a percent)	21.80%	32.60%
Business Segments \| Global Business Services
Segment Information
Revenue	$ 4,245	$ 4,449
Pre-tax income/(loss) from continuing operations	$ 190	$ 588
Revenue year-to-year change (as a percent)	(4.60%)
Pre-tax income year-to-year change (as a percent)	(67.70%)
Pre-tax income margin (as a percent)	4.50%	13.20%
Business Segments \| Technology Services & Cloud Platforms
Segment Information
Revenue	$ 8,589	$ 8,720
Pre-tax income/(loss) from continuing operations	$ 258	$ 1,131
Revenue year-to-year change (as a percent)	(1.50%)
Pre-tax income year-to-year change (as a percent)	(77.20%)
Pre-tax income margin (as a percent)	3.00%	13.00%
Business Segments \| Systems
Segment Information
Revenue	$ 1,888	$ 2,314
Pre-tax income/(loss) from continuing operations	$ (10)	$ 261
Revenue year-to-year change (as a percent)	(18.40%)
Pre-tax income margin (as a percent)	(0.50%)	11.30%
Business Segments \| Global Financing
Segment Information
Revenue	$ 896	$ 1,048
Pre-tax income/(loss) from continuing operations	$ 386	$ 515
Revenue year-to-year change (as a percent)	(14.50%)
Pre-tax income year-to-year change (as a percent)	(25.00%)
Pre-tax income margin (as a percent)	43.10%	49.20%
Internal transactions
Segment Information
Pre-tax income/(loss) from continuing operations	$ (355)	$ (363)
Internal transactions \| Total Segments
Segment Information
Revenue	(1,645)	(1,690)
Internal transactions \| Cognitive Solutions
Segment Information
Revenue	(668)	(635)
Internal transactions \| Global Business Services
Segment Information
Revenue	(113)	(131)
Internal transactions \| Technology Services & Cloud Platforms
Segment Information
Revenue	(165)	(166)
Internal transactions \| Systems
Segment Information
Revenue	(212)	(173)
Internal transactions \| Global Financing
Segment Information
Revenue	$ (486)	$ (586)

The percentage change from year to year in the pre-tax income for segment reporting purposes.

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The pre-tax income margin percentage for segment reporting purposes.

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The percentage change from year to year in the revenue for segment reporting purposes.

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This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 20
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=51673353&loc=d3e41242-110953

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 10
-Article 5

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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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.

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