Goodwill, Customer Relationships and Other Intangible Assets - Schedule of Goodwill, Customer Relationships, and Other Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Goodwill [Line Items]
Goodwill	$ 21,507	$ 28,031
Finite-lived intangible assets, net	7,902	8,911
Indefinite-life intangible assets	269	269
Total other intangible assets, net	1,977	1,868
Customer relationships
Goodwill [Line Items]
Finite-lived intangible assets, net	7,902	8,911
Accumulated amortization	9,481	8,492
Computer Software, Intangible Asset
Goodwill [Line Items]
Finite-lived intangible assets, net	1,599	1,468
Accumulated amortization	2,858	2,616
Trade Names and Patents
Goodwill [Line Items]
Finite-lived intangible assets, net	109	131
Accumulated amortization	$ 83	$ 61