Goodwill, Customer Relationships and Other Intangible Assets - Schedule of Goodwill (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 9,360	$ 9,360
Finite-lived intangible assets, net	231	343
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, net	0	88
Accumulated amortization	5,699	5,611
Other Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, net	231	255
Accumulated amortization	$ 1,842	$ 1,831