Goodwill, Customer Relationships and Other Intangible Assets - Schedule of Goodwill and Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 21,534	$ 28,031	$ 30,475
Finite-lived intangible assets, net	7,596	8,911
Indefinite-life intangible assets	269	269
Other intangible assets, net	1,971	1,868
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, net	7,596	8,911
Accumulated amortization	9,809	8,492
Capitalized software
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, net	1,599	1,468
Accumulated amortization	2,957	2,616
Tradenames and patents
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, net	103	131
Accumulated amortization	$ 91	$ 61