Revenues - Accounts Receivable, Net (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Accounts Receivable, net	$ 1,277	$ 1,148
Freight Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, gross	1,081	951
Allowance for Credit Losses	(15)	(14)
Total Accounts Receivable, net	1,066	937
Non-Freight Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, gross	226	225
Allowance for Credit Losses	(15)	(14)
Total Accounts Receivable, net	$ 211	$ 211