Stock Plans and Share-Based Compensation - Schedule of Assumptions and Inputs Used to Estimate Fair Value of Stock Options (Details) - Stock Options - $ / shares	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-Average Fair Value of Units Granted (in dollars per share)	$ 9.47	$ 11.58	$ 9.82
Annual Dividend Yield	1.50%	1.30%	1.40%
Risk-free Interest Rate	4.10%	4.20%	3.80%
Annualized Volatility	26.60%	28.70%	29.60%
Expected Life (in years)	6 years	6 years	6 years
Weighted-average Grant-date Market Price of CSX Stock (Strike Price) (in dollars per share)	$ 33.94	$ 36.73	$ 31.54