Summarized Consolidating Financial Data (Consolidating Cash Flow Statements) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities
Net Cash Provided by (Used in) Operating Activities	$ 4,850	$ 4,641	$ 3,472
Investing Activities
Property Additions	(1,657)	(1,745)	(2,040)
Purchase of Short-term Investments	(2,838)	(736)	(782)
Proceeds from Sales of Short-term Investments	2,108	505	1,193
Proceeds from Property Dispositions	254	319	97
Other Investing Activities	31	(27)	37
Net Cash Used in Investing Activities	(2,102)	(1,684)	(1,495)
Financing Activities
Long-term Debt Issued	2,000	3,000	850
Long-term Debt Repaid	(518)	(19)	(333)
Dividends Paid	(763)	(751)	(708)
Shares Repurchased	(3,373)	(4,671)	(1,970)
Other Financing Activities	6	(59)	(18)
Net Cash Used in Financing Activities	(2,648)	(2,500)	(2,179)
Net Increase (Decrease) in Cash and Cash Equivalents	100	457	(202)
Cash and Cash Equivalents at Beginning of Period	858	401	603
Cash and Cash Equivalents at End of Period	958	858	401
Eliminations and Other
Operating Activities
Net Cash Provided by (Used in) Operating Activities	(862)	(198)	(359)
Investing Activities
Property Additions	(151)	(165)	(192)
Purchase of Short-term Investments	0	(2)	(8)
Proceeds from Sales of Short-term Investments	3	20	3
Proceeds from Property Dispositions	0	0	0
Other Investing Activities	6	(661)	(55)
Net Cash Used in Investing Activities	(142)	(808)	(252)
Financing Activities
Long-term Debt Issued	0	0	0
Long-term Debt Repaid	0	0	0
Dividends Paid	1,000	1,000	600
Shares Repurchased	0	0	0
Other Financing Activities	0	12	0
Net Cash Used in Financing Activities	1,000	1,012	600
Net Increase (Decrease) in Cash and Cash Equivalents	(4)	6	(11)
Cash and Cash Equivalents at Beginning of Period	12	6	17
Cash and Cash Equivalents at End of Period	8	12	6
CSX Corporation
Operating Activities
Net Cash Provided by (Used in) Operating Activities	3,440	3,182	1,719
Investing Activities
Property Additions	0	0	0
Purchase of Short-term Investments	(2,838)	(734)	(774)
Proceeds from Sales of Short-term Investments	2,105	485	1,190
Proceeds from Property Dispositions	0	0	0
Other Investing Activities	15	(4)	(2)
Net Cash Used in Investing Activities	(718)	(253)	414
Financing Activities
Long-term Debt Issued	2,000	3,000	850
Long-term Debt Repaid	(500)	0	(313)
Dividends Paid	(763)	(751)	(708)
Shares Repurchased	(3,373)	(4,671)	(1,970)
Other Financing Activities	12	(65)	(23)
Net Cash Used in Financing Activities	(2,624)	(2,487)	(2,164)
Net Increase (Decrease) in Cash and Cash Equivalents	98	442	(31)
Cash and Cash Equivalents at Beginning of Period	716	274	305
Cash and Cash Equivalents at End of Period	814	716	274
CSX Transportation
Operating Activities
Net Cash Provided by (Used in) Operating Activities	2,272	1,657	2,112
Investing Activities
Property Additions	(1,506)	(1,580)	(1,848)
Purchase of Short-term Investments	0	0	0
Proceeds from Sales of Short-term Investments	0	0	0
Proceeds from Property Dispositions	254	319	97
Other Investing Activities	10	638	94
Net Cash Used in Investing Activities	(1,242)	(623)	(1,657)
Financing Activities
Long-term Debt Issued	0	0	0
Long-term Debt Repaid	(18)	(19)	(20)
Dividends Paid	(1,000)	(1,000)	(600)
Shares Repurchased	0	0	0
Other Financing Activities	(6)	(6)	5
Net Cash Used in Financing Activities	(1,024)	(1,025)	(615)
Net Increase (Decrease) in Cash and Cash Equivalents	6	9	(160)
Cash and Cash Equivalents at Beginning of Period	130	121	281
Cash and Cash Equivalents at End of Period	$ 136	$ 130	$ 121