Goodwill, Customer Relationships and Other Intangible Assets - Schedule of Goodwill and Other Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2023	Mar. 31, 2023	Dec. 31, 2022
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 0		$ 1,970
Other intangible assets, net	4,516		4,973
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, net	4,088		4,563
Accumulated amortization	3,735		3,265
Capitalized software
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, net	428		410
Accumulated amortization	401		387
Trade names
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, net	0		0
Accumulated amortization	$ 0		$ 130
Fully Amortized and Retired Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Gross carrying value of intangibles fully amortized and retired		$ 130