Cover Page - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2019	Jan. 31, 2020	Jun. 30, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	1-8022
Entity Registrant Name	CSX CORPORATION
Entity Incorporation, State or Country Code	VA
Entity Tax Identification Number	62-1051971
Entity Address, Address Line One	500 Water Street
Entity Address, Address Line Two	15th Floor
Entity Address, City or Town	Jacksonville
Entity Address, State or Province	FL
Entity Address, Postal Zip Code	32202
City Area Code	904
Local Phone Number	359-3200
Title of 12(b) Security	Common Stock, $1 Par Value
Trading Symbol	CSX
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 59
Entity Common Stock, Shares Outstanding		773,825,565
Entity Central Index Key	0000277948
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false