Acquisitions/Divestitures - Other Disposal Groups (Details) $ in Millions				3 Months Ended			9 Months Ended	12 Months Ended
	Oct. 01, 2014	Jan. 23, 2014 USD ($)	Sep. 10, 2013 USD ($)	Sep. 30, 2016 USD ($) item	Jun. 30, 2016 item	Mar. 31, 2016 USD ($) item	Sep. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Industry Standard x86 Server Portfolio | Disposal group disposed of by sale, not discontinued operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Transaction price for sale of business		$ 2,100
Approximate amount of transaction price received in cash		$ 1,800
Pre-tax gain/(loss) on sale of business							$ 36	$ 63
Expected pre-tax gain (loss) on sale of business				$ 1,600			1,600
Disposal group expected total gain (loss) on sale, net of associated costs				1,300			1,300
Cumulative gain on sale of business, net of transition and performance-based costs				1,200			1,200
Industry Standard x86 Server Portfolio | Minimum | Disposal group disposed of by sale, not discontinued operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Transition service agreement duration	1 year
Industry Standard x86 Server Portfolio | Maximum | Disposal group disposed of by sale, not discontinued operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal group equity consideration ownership (as a percent)		5.00%
Transition service agreement duration	3 years
Customer Care Business Process Outsourcing Services | Disposal group disposed of by sale, not discontinued operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Transaction price for sale of business			$ 501
Approximate amount of transaction price received in cash			430
Amount of transaction price received in stock			$ 71
Pre-tax gain/(loss) on sale of business								$ 7	$ 202
Cumulative pre-tax gain/(loss) on sale of business				$ 213			$ 213
Customer Care Business Process Outsourcing Services | Maximum | Disposal group disposed of by sale, not discontinued operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal group equity consideration ownership (as a percent)			5.00%
Others
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Pre-tax gain/(loss) on sale of business						$ 36
Number of divestitures | item				0	0	4