Document And Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 25, 2015	Jan. 22, 2016	Jun. 26, 2015
Document and Entity Information [Abstract]
Entity Registrant Name	CSX CORP
Entity Central Index Key	0000277948
Current Fiscal Year End Date	--12-25
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 33
Entity Common Stock, Shares Outstanding		963,150,011
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 25, 2015