Investment in Affiliates and Related-Party Transactions - Schedule of Related Party Consolidated Balance Sheet Components (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023
Corporate Joint Venture \| Conrail
Related Party Transaction [Line Items]
Accounts payable	$ 172	$ 154
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	$ 44	$ 43

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