Goodwill, Customer Relationships and Other Intangible Assets - Rollforward of Goodwill (Details) $ in Millions	6 Months Ended
	Jun. 30, 2020 USD ($)
Goodwill [Roll Forward]
As of December 31, 2019	$ 21,534
Effect of foreign currency exchange rate change and other	(65)
As of June 30, 2020	21,469
International and Global Accounts
Goodwill [Roll Forward]
As of December 31, 2019	2,670
Effect of foreign currency exchange rate change and other	(65)
As of June 30, 2020	2,605
Enterprise
Goodwill [Roll Forward]
As of December 31, 2019	4,738
Effect of foreign currency exchange rate change and other	0
As of June 30, 2020	4,738
Small and Medium Business
Goodwill [Roll Forward]
As of December 31, 2019	3,259
Effect of foreign currency exchange rate change and other	0
As of June 30, 2020	3,259
Wholesale
Goodwill [Roll Forward]
As of December 31, 2019	3,813
Effect of foreign currency exchange rate change and other	0
As of June 30, 2020	3,813
Consumer
Goodwill [Roll Forward]
As of December 31, 2019	7,054
Effect of foreign currency exchange rate change and other	0
As of June 30, 2020	$ 7,054