Summarized Consolidating Financial Data - Consolidating Cash Flow Statements (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 25, 2015	Sep. 26, 2014	Sep. 25, 2015	Sep. 26, 2014
Operating Activities
Net Cash Provided by (Used in) Operating Activities			$ 2,512	$ 2,302
Investing Activities
Property Additions			(1,909)	(1,557)
Purchase of Short-term Investments			(1,170)	(1,170)
Proceeds from Sales of Short-term Investments			1,040	1,102
Proceeds from Property Dispositions			46	57
Other Investing Activities			42	(52)
Net Cash Used in Investing Activities			(1,951)	(1,620)
Financing Activities
Long-term Debt Issued			600	1,000
Long-term Debt Repaid			(228)	(932)
Dividends Paid			(512)	(470)
Shares Repurchased	$ (262)	$ (131)	(546)	(388)
Other Financing Activities			(3)	(5)
Net Cash Used in Financing Activities			(689)	(795)
Net Decrease in Cash and Cash Equivalents			(128)	(113)
Cash and Cash Equivalents at Beginning of Period			669	592
Cash and Cash Equivalents at End of Period	541	479	541	479
CSX Corporation
Operating Activities
Net Cash Provided by (Used in) Operating Activities			637	397
Investing Activities
Property Additions			0	0
Purchase of Short-term Investments			(1,170)	(1,170)
Proceeds from Sales of Short-term Investments			995	1,077
Proceeds from Property Dispositions			0	0
Other Investing Activities			(11)	0
Net Cash Used in Investing Activities			(186)	(93)
Financing Activities
Long-term Debt Issued			600	1,000
Long-term Debt Repaid			(200)	(600)
Dividends Paid			(512)	(470)
Shares Repurchased			(546)	(388)
Other Financing Activities			8	10
Net Cash Used in Financing Activities			(650)	(448)
Net Decrease in Cash and Cash Equivalents			(199)	(144)
Cash and Cash Equivalents at Beginning of Period			510	439
Cash and Cash Equivalents at End of Period	311	295	311	295
CSX Transportation
Operating Activities
Net Cash Provided by (Used in) Operating Activities			2,313	2,301
Investing Activities
Property Additions			(1,794)	(1,398)
Purchase of Short-term Investments			0	0
Proceeds from Sales of Short-term Investments			0	0
Proceeds from Property Dispositions			46	57
Other Investing Activities			93	(147)
Net Cash Used in Investing Activities			(1,655)	(1,488)
Financing Activities
Long-term Debt Issued			0	0
Long-term Debt Repaid			(28)	(332)
Dividends Paid			(563)	(428)
Shares Repurchased			0	0
Other Financing Activities			1	(16)
Net Cash Used in Financing Activities			(590)	(776)
Net Decrease in Cash and Cash Equivalents			68	37
Cash and Cash Equivalents at Beginning of Period			100	91
Cash and Cash Equivalents at End of Period	168	128	168	128
Eliminations and Other
Operating Activities
Net Cash Provided by (Used in) Operating Activities			(438)	(396)
Investing Activities
Property Additions			(115)	(159)
Purchase of Short-term Investments			0	0
Proceeds from Sales of Short-term Investments			45	25
Proceeds from Property Dispositions			0	0
Other Investing Activities			(40)	95
Net Cash Used in Investing Activities			(110)	(39)
Financing Activities
Long-term Debt Issued			0	0
Long-term Debt Repaid			0	0
Dividends Paid			563	428
Shares Repurchased			0	0
Other Financing Activities			(12)	1
Net Cash Used in Financing Activities			551	429
Net Decrease in Cash and Cash Equivalents			3	(6)
Cash and Cash Equivalents at Beginning of Period			59	62
Cash and Cash Equivalents at End of Period	$ 62	$ 56	$ 62	$ 56