Summarized Consolidating Financial Data - Consolidating Cash Flow Statements (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 25, 2016
Operating Activities
Net Cash Provided by (Used in) Operating Activities	$ 1,043	$ 754
Investing Activities
Property Additions	(441)	(425)
Purchase of Short-term Investments	(75)	(235)
Proceeds from Sales of Short-term Investments	205	670
Other Investing Activities	25	31
Net Cash (Used in) Provided by Investing Activities	(286)	41
Financing Activities
Dividends Paid	(166)	(173)
Shares Repurchased	(258)	(249)
Other Financing Activities	(6)	(270)
Net Cash Used in Financing Activities	(430)	(692)
Net Increase in Cash and Cash Equivalents	327	103
Cash and Cash Equivalents at Beginning of Period	603	628
Cash and Cash Equivalents at End of Period	930	731
CSX Corporation
Operating Activities
Net Cash Provided by (Used in) Operating Activities	644	36
Investing Activities
Property Additions	0	0
Purchase of Short-term Investments	(75)	(235)
Proceeds from Sales of Short-term Investments	205	670
Other Investing Activities	(1)	(1)
Net Cash (Used in) Provided by Investing Activities	129	434
Financing Activities
Dividends Paid	(166)	(173)
Shares Repurchased	(258)	(249)
Other Financing Activities	(6)	1
Net Cash Used in Financing Activities	(430)	(421)
Net Increase in Cash and Cash Equivalents	343	49
Cash and Cash Equivalents at Beginning of Period	305	444
Cash and Cash Equivalents at End of Period	648	493
CSX Transportation
Operating Activities
Net Cash Provided by (Used in) Operating Activities	566	834
Investing Activities
Property Additions	(397)	(391)
Purchase of Short-term Investments	0	0
Proceeds from Sales of Short-term Investments	0	0
Other Investing Activities	(24)	26
Net Cash (Used in) Provided by Investing Activities	(421)	(365)
Financing Activities
Dividends Paid	(150)	(150)
Shares Repurchased	0	0
Other Financing Activities	(4)	(271)
Net Cash Used in Financing Activities	(154)	(421)
Net Increase in Cash and Cash Equivalents	(9)	48
Cash and Cash Equivalents at Beginning of Period	281	175
Cash and Cash Equivalents at End of Period	272	223
Eliminations and Other
Operating Activities
Net Cash Provided by (Used in) Operating Activities	(167)	(116)
Investing Activities
Property Additions	(44)	(34)
Purchase of Short-term Investments	0	0
Proceeds from Sales of Short-term Investments	0	0
Other Investing Activities	50	6
Net Cash (Used in) Provided by Investing Activities	6	(28)
Financing Activities
Dividends Paid	150	150
Shares Repurchased	0	0
Other Financing Activities	4	0
Net Cash Used in Financing Activities	154	150
Net Increase in Cash and Cash Equivalents	(7)	6
Cash and Cash Equivalents at Beginning of Period	17	9
Cash and Cash Equivalents at End of Period	$ 10	$ 15