Basis of Presentation - Reclassification (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018		Sep. 30, 2019		Sep. 30, 2018
Revenues	$ 18,028	$ 18,756		$ 55,370		$ 57,830
Cost of Revenue	9,692	9,953		29,982		31,582
Services
Revenues	11,703	12,043	[1]	35,454	[1]	36,848	[1]
Cost of Revenue	7,840	7,951	[1]	24,293	[1]	25,238	[1]
Sales
Revenues	5,981	6,324	[1]	18,817	[1]	19,787	[1]
Cost of Revenue	$ 1,635	1,714	[1]	4,979	[1]	5,498	[1]
Reclassification | Services
Revenues		(500)		(1,000)		(1,600)
Cost of Revenue		(100)		(200)		(300)
Reclassification | Sales
Revenues		500		1,000		1,600
Cost of Revenue		$ 100		$ 200		$ 300

[1] Reclassified to conform to current period presentation. Refer to note 1, “Basis of Presentation.”