Summarized Consolidating Financial Data - Consolidating Cash Flow Statements (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating Activities
Net Cash Provided by (Used in) Operating Activities	$ 1,173	$ 966
Investing Activities
Property Additions	(353)	(368)
Proceeds from Property Dispositions	48	52
Purchase of Short-term Investments	(813)	0
Proceeds from Sales of Short-term Investments	250	8
Other Investing Activities	(2)	(8)
Net Cash Used In Investing Activities	(870)	(316)
Financing Activities
Long-term Debt Issued	1,000	2,000
Dividends Paid	(195)	(194)
Shares Repurchased	(796)	(836)
Other Financing Activities	18	(41)
Net Cash Provided by Financing Activities	27	929
Net Increase in Cash and Cash Equivalents	330	1,579
Cash and Cash Equivalents at Beginning of Period	858	401
Cash and Cash Equivalents at End of Period	1,188	1,980
Eliminations and Other
Operating Activities
Net Cash Provided by (Used in) Operating Activities	(212)	(346)
Investing Activities
Property Additions	(34)	(29)
Proceeds from Property Dispositions	(3)	0
Purchase of Short-term Investments	0
Proceeds from Sales of Short-term Investments	0	8
Other Investing Activities	0	113
Net Cash Used In Investing Activities	(37)	92
Financing Activities
Long-term Debt Issued	0	0
Dividends Paid	250	250
Shares Repurchased	0	0
Other Financing Activities	0	3
Net Cash Provided by Financing Activities	250	253
Net 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	13	5
CSX Corporation
Operating Activities
Net Cash Provided by (Used in) Operating Activities	852	691
Investing Activities
Property Additions	0	0
Proceeds from Property Dispositions	0	0
Purchase of Short-term Investments	(813)
Proceeds from Sales of Short-term Investments	250	0
Other Investing Activities	(1)	(1)
Net Cash Used In Investing Activities	(564)	(1)
Financing Activities
Long-term Debt Issued	1,000	2,000
Dividends Paid	(195)	(194)
Shares Repurchased	(796)	(836)
Other Financing Activities	19	(40)
Net Cash Provided by Financing Activities	28	930
Net Increase in Cash and Cash Equivalents	316	1,620
Cash and Cash Equivalents at Beginning of Period	716	274
Cash and Cash Equivalents at End of Period	1,032	1,894
CSX Transportation
Operating Activities
Net Cash Provided by (Used in) Operating Activities	533	621
Investing Activities
Property Additions	(319)	(339)
Proceeds from Property Dispositions	51	52
Purchase of Short-term Investments	0
Proceeds from Sales of Short-term Investments	0	0
Other Investing Activities	(1)	(120)
Net Cash Used In Investing Activities	(269)	(407)
Financing Activities
Long-term Debt Issued	0	0
Dividends Paid	(250)	(250)
Shares Repurchased	0	0
Other Financing Activities	(1)	(4)
Net Cash Provided by Financing Activities	(251)	(254)
Net Increase in Cash and Cash Equivalents	13	(40)
Cash and Cash Equivalents at Beginning of Period	130	121
Cash and Cash Equivalents at End of Period	$ 143	$ 81