Document And Entity Information	3 Months Ended
	Mar. 25, 2016 shares
Document and Entity Information [Abstract]
Entity Registrant Name	CSX CORP
Entity Central Index Key	0000277948
Current Fiscal Year End Date	--12-30
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding	955,867,082
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q1
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 25, 2016