Summarized Consolidating Financial Data - Consolidating Cash Flow Statements (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 26, 2015	Jun. 27, 2014	Jun. 26, 2015	Jun. 27, 2014
Operating Activities
Net Cash Provided by (Used in) Operating Activities			$ 1,582	$ 1,445
Investing Activities
Property Additions			(1,288)	(956)
Purchase of Short-term Investments			(775)	(360)
Proceeds from Sales of Short-term Investments			390	646
Proceeds from Property Dispositions			47	37
Other Investing Activities			52	(17)
Net Cash Used in Investing Activities			(1,574)	(650)
Financing Activities
Long-term Debt Issued			600	0
Long-term Debt Repaid			(210)	(244)
Dividends Paid			(336)	(311)
Shares Repurchased	$ (157)	$ (130)	(284)	(257)
Other Financing Activities			(9)	(2)
Net Cash Used in Financing Activities			(239)	(814)
Net Decrease in Cash and Cash Equivalents			(231)	(19)
Cash and Cash Equivalents at Beginning of Period			669	592
Cash and Cash Equivalents at End of Period	438	573	438	573
CSX Corporation
Operating Activities
Net Cash Provided by (Used in) Operating Activities			367	453
Investing Activities
Property Additions			0	0
Purchase of Short-term Investments			(775)	(360)
Proceeds from Sales of Short-term Investments			355	637
Proceeds from Property Dispositions			0	0
Other Investing Activities			(11)	0
Net Cash Used in Investing Activities			(431)	277
Financing Activities
Long-term Debt Issued			600
Long-term Debt Repaid			(200)	(200)
Dividends Paid			(336)	(311)
Shares Repurchased			(284)	(257)
Other Financing Activities			7	6
Net Cash Used in Financing Activities			(213)	(762)
Net Decrease in Cash and Cash Equivalents			(277)	(32)
Cash and Cash Equivalents at Beginning of Period			510	439
Cash and Cash Equivalents at End of Period	233	407	233	407
CSX Transportation
Operating Activities
Net Cash Provided by (Used in) Operating Activities			1,530	1,276
Investing Activities
Property Additions			(1,215)	(867)
Purchase of Short-term Investments			0	0
Proceeds from Sales of Short-term Investments			0	0
Proceeds from Property Dispositions			46	37
Other Investing Activities			72	(95)
Net Cash Used in Investing Activities			(1,097)	(925)
Financing Activities
Long-term Debt Issued			0
Long-term Debt Repaid			(10)	(44)
Dividends Paid			(375)	(285)
Shares Repurchased			0	0
Other Financing Activities			(4)	(10)
Net Cash Used in Financing Activities			(389)	(339)
Net Decrease in Cash and Cash Equivalents			44	12
Cash and Cash Equivalents at Beginning of Period			100	91
Cash and Cash Equivalents at End of Period	144	103	144	103
Eliminations and Other
Operating Activities
Net Cash Provided by (Used in) Operating Activities			(315)	(284)
Investing Activities
Property Additions			(73)	(89)
Purchase of Short-term Investments			0	0
Proceeds from Sales of Short-term Investments			35	9
Proceeds from Property Dispositions			1	0
Other Investing Activities			(9)	78
Net Cash Used in Investing Activities			(46)	(2)
Financing Activities
Long-term Debt Issued			0
Long-term Debt Repaid			0	0
Dividends Paid			375	285
Shares Repurchased			0	0
Other Financing Activities			(12)	2
Net Cash Used in Financing Activities			363	287
Net Decrease in Cash and Cash Equivalents			2	1
Cash and Cash Equivalents at Beginning of Period			59	62
Cash and Cash Equivalents at End of Period	$ 61	$ 63	$ 61	$ 63