Investment in Affiliates and Related-Party Transactions - Schedule of Related Party Consolidated Balance Sheet Components (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Corporate Joint Venture \| Conrail
Related Party Transaction [Line Items]
Accounts payable	$ 154	$ 136
Corporate Joint Venture \| Conrail \| 1.31% CSX Promissory Note due December 2050
Related Party Transaction [Line Items]
Notes payable	$ 73	$ 73
Promissory note interest rate	1.31%	1.31%
Corporate Joint Venture \| Conrail \| 1.31% CSXT Promissory Note due December 2050
Related Party Transaction [Line Items]
Notes payable	$ 368	$ 368
Promissory note interest rate	1.31%	1.31%
Related Party \| TTX
Related Party Transaction [Line Items]
Accounts payable	$ 43	$ 38

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business.

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