Investment in Affiliates and Related-Party Transactions - Schedule of Related Party Consolidated Balance Sheet Components (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Corporate Joint Venture | Conrail | Accounts Payable
Related Party Transaction [Line Items]
Payable to Affiliates	$ 100	$ 50
Corporate Joint Venture | Conrail | Long-term Debt | 1.31% CSX Promissory Note due December 2050
Related Party Transaction [Line Items]
Promissory note interest rate	1.31%	1.31%
Promissory notes payable to Conrail subsidiary	$ 73	$ 73
Corporate Joint Venture | Conrail | Long-term Debt | 1.31% CSXT Promissory Note due December 2050
Related Party Transaction [Line Items]
Promissory note interest rate	1.31%	1.31%
Promissory notes payable to Conrail subsidiary	$ 368	$ 368
Affiliated Entity | TTX | Accounts Payable
Related Party Transaction [Line Items]
Payable to Affiliates	$ 35	$ 40