Goodwill, Customer Relationships and Other Intangible Assets - Schedule of Goodwill and Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Finite-Lived and Indefinite-Lived Intangible Assets
Goodwill	$ 0	$ 0		$ 1,970	$ 6,666
Finite lived intangible assets, net	4,237	4,237		4,973
Customer relationships
Finite-Lived and Indefinite-Lived Intangible Assets
Finite lived intangible assets, net	3,810	3,810		4,563
Accumulated amortization	3,896	3,896		3,265
Loss on intangible asset disposition	121	73
Capitalized software
Finite-Lived and Indefinite-Lived Intangible Assets
Finite lived intangible assets, net	427	427		410
Accumulated amortization	419	419		387
Trade names
Finite-Lived and Indefinite-Lived Intangible Assets
Finite lived intangible assets, net	0	0		0
Accumulated amortization	$ 0	$ 0		$ 130
Fully Amortized and Retired Trade Names
Finite-Lived and Indefinite-Lived Intangible Assets
Finite-Lived Intangible Assets, Gross			$ 130