Acquisitions/Divestitures (Narratives) (Details 1) $ in Millions	9 Months Ended
	Sep. 30, 2015 USD ($) Acquisition	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Acquisitions:
Businesses acquired, number (in entities) | Acquisition	7
Businesses acquired, aggregate cost	$ 782
Goodwill	30,275	$ 30,556	$ 31,184
Software
Acquisitions:
Goodwill	$ 20,957	21,000	21,121
Businesses acquired, privately held companies number (in entities) | Acquisition	6
Global Technology Services
Acquisitions:
Goodwill	$ 3,506	$ 3,530	$ 3,608
Businesses acquired, privately held companies number (in entities) | Acquisition	1
Acquisitions
Acquisitions:
Acquired intangible asset, weighted average useful life	5 years 10 months
Expected percent of goodwill deductible for tax purposes	1.00%
Total purchase price	$ 782
Goodwill	637
Acquisitions | Software
Acquisitions:
Goodwill	574
Acquisitions | Global Technology Services
Acquisitions:
Goodwill	$ 62