Summarized Consolidating Financial Data - Consolidating Cash Flow Statements (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating Activities
Net Cash Provided by (Used in) Operating Activities			$ 2,267	$ 2,009
Investing Activities
Property Additions			(769)	(823)
Proceeds from Property Dispositions			146	141
Purchase of Short-term Investments			(1,427)	(77)
Proceeds from Sales of Short-term Investments			810	12
Other Investing Activities			(16)	(8)
Net Cash Used In Investing Activities			(1,256)	(755)
Financing Activities
Long-term Debt Issued			1,000	2,000
Dividends Paid			(388)	(384)
Shares Repurchased	$ (860)	$ (974)	(1,656)	(1,810)
Accelerated Share Repurchase Pending Final Settlement			0	(90)
Other Financing Activities			28	(51)
Net Cash Used in Financing Activities			(1,016)	(335)
Net (Decrease)/Increase in Cash and Cash Equivalents			(5)	919
Cash and Cash Equivalents at Beginning of Period			858	401
Cash and Cash Equivalents at End of Period	853	1,320	853	1,320
Eliminations and Other
Operating Activities
Net Cash Provided by (Used in) Operating Activities			(433)	(547)
Investing Activities
Property Additions			(62)	(61)
Proceeds from Property Dispositions			0	0
Purchase of Short-term Investments			0	(2)
Proceeds from Sales of Short-term Investments			0	12
Other Investing Activities			(5)	92
Net Cash Used In Investing Activities			(67)	41
Financing Activities
Long-term Debt Issued			0	0
Dividends Paid			500	500
Shares Repurchased			0	0
Accelerated Share Repurchase Pending Final Settlement				0
Other Financing Activities			(1)	5
Net Cash Used in Financing Activities			499	505
Net (Decrease)/Increase in Cash and Cash Equivalents			(1)	(1)
Cash and Cash Equivalents at Beginning of Period			12	6
Cash and Cash Equivalents at End of Period	11	5	11	5
CSX Corporation
Operating Activities
Net Cash Provided by (Used in) Operating Activities			1,636	1,311
Investing Activities
Property Additions			0	0
Proceeds from Property Dispositions			0	0
Purchase of Short-term Investments			(1,427)	(75)
Proceeds from Sales of Short-term Investments			810	0
Other Investing Activities			(5)	(1)
Net Cash Used In Investing Activities			(622)	(76)
Financing Activities
Long-term Debt Issued			1,000	2,000
Dividends Paid			(388)	(384)
Shares Repurchased			(1,656)	(1,810)
Accelerated Share Repurchase Pending Final Settlement				(90)
Other Financing Activities			32	(53)
Net Cash Used in Financing Activities			(1,012)	(337)
Net (Decrease)/Increase in Cash and Cash Equivalents			2	898
Cash and Cash Equivalents at Beginning of Period			716	274
Cash and Cash Equivalents at End of Period	718	1,172	718	1,172
CSX Transportation
Operating Activities
Net Cash Provided by (Used in) Operating Activities			1,064	1,245
Investing Activities
Property Additions			(707)	(762)
Proceeds from Property Dispositions			146	141
Purchase of Short-term Investments			0	0
Proceeds from Sales of Short-term Investments			0	0
Other Investing Activities			(6)	(99)
Net Cash Used In Investing Activities			(567)	(720)
Financing Activities
Long-term Debt Issued			0	0
Dividends Paid			(500)	(500)
Shares Repurchased			0	0
Accelerated Share Repurchase Pending Final Settlement				0
Other Financing Activities			(3)	(3)
Net Cash Used in Financing Activities			(503)	(503)
Net (Decrease)/Increase in Cash and Cash Equivalents			(6)	22
Cash and Cash Equivalents at Beginning of Period			130	121
Cash and Cash Equivalents at End of Period	$ 124	$ 143	$ 124	$ 143