Intangible Assets Including Goodwill - Goodwill by Segment (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2016	Dec. 31, 2015
Changes in Goodwill Balances
Beginning Balance	$ 32,021	$ 30,556
Goodwill Additions	4,137	2,590
Purchase Price Adjustments	11	(3)
Divestitures	(17)	(26)
Foreign Currency Translation and Other Adjustments	248	(1,096)
Ending Balance	36,401	32,021
Goodwill impairment losses	0	0
Goodwill accumulated impairment losses	0	0
Cognitive Solutions
Changes in Goodwill Balances
Beginning Balance	15,621	15,156
Goodwill Additions	3,769	1,020
Purchase Price Adjustments	4	(2)
Divestitures	(12)	(18)
Foreign Currency Translation and Other Adjustments	134	(535)
Ending Balance	19,516	15,621
Global Business Services
Changes in Goodwill Balances
Beginning Balance	4,396	4,555
Goodwill Additions	278	74
Purchase Price Adjustments	5	0
Divestitures	(1)	(1)
Foreign Currency Translation and Other Adjustments	16	(232)
Ending Balance	4,693	4,396
Technology Services & Cloud Platforms
Changes in Goodwill Balances
Beginning Balance	10,156	9,373
Goodwill Additions	91	1,087
Purchase Price Adjustments	1	(1)
Divestitures	(5)	(7)
Foreign Currency Translation and Other Adjustments	89	(296)
Ending Balance	10,333	10,156
Systems
Changes in Goodwill Balances
Beginning Balance	1,848	1,472
Goodwill Additions		410
Purchase Price Adjustments	2	0
Foreign Currency Translation and Other Adjustments	10	(33)
Ending Balance	$ 1,859	$ 1,848

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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