Document And Entity Information	9 Months Ended
	Sep. 25, 2015 shares
Document and Entity Information [Abstract]
Entity Registrant Name	CSX CORP
Entity Central Index Key	0000277948
Current Fiscal Year End Date	--12-25
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding	974,944,791
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q3
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 25, 2015