Goodwill and Purchased Intangible Assets - Schedule of Goodwill (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Goodwill [Roll Forward]
Goodwill	$ 2,769	$ 2,764
Accumulated Impairment Losses	(23)
Total	2,741
Additions	0
Impairment	0
Other	5
Goodwill	2,769
Accumulated Impairment Losses	(23)
Total	2,746
Software
Goodwill [Roll Forward]
Goodwill	1,949	1,944
Accumulated Impairment Losses	(7)
Total	1,937
Additions	0
Impairment	0
Other	5
Goodwill	1,949
Accumulated Impairment Losses	(7)
Total	1,942
Services
Goodwill [Roll Forward]
Goodwill	658	658
Accumulated Impairment Losses	0
Total	658
Additions	0
Impairment	0
Other	0
Goodwill	658
Accumulated Impairment Losses	0
Total	658
Hardware
Goodwill [Roll Forward]
Goodwill	162	$ 162
Accumulated Impairment Losses	(16)
Total	146
Additions	0
Impairment	0
Other	0
Goodwill	162
Accumulated Impairment Losses	(16)
Total	$ 146