Revenues - Accounts Receivables, Net (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Accounts Receivable, net	$ 1,148	$ 912
Freight Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivables, gross	951	716
Allowance for Credit Losses	(14)	(16)
Total Accounts Receivable, net	937	700
Non-Freight Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivables, gross	225	224
Allowance for Credit Losses	(14)	(12)
Total Accounts Receivable, net	$ 211	$ 212