Document And Entity Information (USD $) In Billions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 30, 2011	Jan. 27, 2012	Jul. 01, 2011
Document Information [Line Items]
Entity Registrant Name	CSX CORP
Entity Central Index Key	0000277948
Current Fiscal Year End Date	--12-30
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 26
Entity Common Stock, Shares Outstanding		1,052,267,692
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 30, 2011