Commitments and Contingencies - Schedule of Number of Locomotives and Payments under Long-term Maintenance Program (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Amounts Paid	$ 456	$ 311	$ 236

Unrecorded Unconditional Purchase Obligation, Purchases And Maintenance Cost

No definition available.

Name:	csx_UnrecordedUnconditionalPurchaseObligationPurchasesAndMaintenanceCost
Namespace Prefix:	csx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration