Goodwill and Purchased Intangible Assets - Schedule of Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017
Goodwill [Line Items]
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount			20.00%
Goodwill [Roll Forward]
Goodwill, Gross	$ 2,750	$ 2,756
Accumulated Impairment Losses	(23)	(23)
Goodwill	2,727	2,733
Additions	0	9
Impairment		0
Other	14	(15)
Goodwill, Gross	2,764	2,750
Accumulated Impairment Losses	(23)	(23)
Total	2,727	2,733	$ 2,741
Software Segment [Domain]
Goodwill [Roll Forward]
Goodwill, Gross	1,930	1,936
Accumulated Impairment Losses	(7)	(7)
Goodwill	1,923	1,929
Additions	0	9
Impairment	0	0
Other	14	(15)
Goodwill, Gross	1,944	1,930
Accumulated Impairment Losses	(7)	(7)
Total	1,923	1,929	1,937
Services Segment [Domain]
Goodwill [Roll Forward]
Goodwill, Gross	658	658
Accumulated Impairment Losses	0	0
Goodwill	658	658
Additions	0	0
Impairment	0	0
Other	0	0
Goodwill, Gross	658	658
Accumulated Impairment Losses	0	0
Total	658	658	658
Hardware Segment [Domain]
Goodwill [Roll Forward]
Goodwill, Gross	162	162
Accumulated Impairment Losses	(16)	(16)
Goodwill	146	146
Additions	0	0
Impairment	0	0
Other	0	0
Goodwill, Gross	162	162
Accumulated Impairment Losses	(16)	(16)
Total	$ 146	$ 146	$ 146