Summarized Consolidating Financial Data - Consolidating Cash Flow Statements (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 23, 2016	Sep. 25, 2015	Sep. 23, 2016	Sep. 25, 2015
Operating Activities
Net Cash Provided by (Used in) Operating Activities			$ 2,488	$ 2,512
Investing Activities
Property Additions			(1,590)	(1,909)
Purchase of Short-term Investments			(410)	(1,170)
Proceeds from Sales of Short-term Investments			1,070	1,040
Proceeds from Property Dispositions			11	46
Other Investing Activities			26	42
Net Cash Used in Investing Activities			(893)	(1,951)
Financing Activities
Long-term Debt Issued			0	600
Long-term Debt Repaid			(19)	(228)
Dividends Paid			(513)	(512)
Stock Options Exercised			0	0
Shares Repurchased	$ (263)	$ (262)	(778)	(546)
Other Financing Activities			(310)	(3)
Net Cash Used in Financing Activities			(1,620)	(689)
Net Decrease in Cash and Cash Equivalents			(25)	(128)
Cash and Cash Equivalents at Beginning of Period			628	669
Cash and Cash Equivalents at End of Period	603	541	603	541
CSX Corporation
Operating Activities
Net Cash Provided by (Used in) Operating Activities			644	637
Investing Activities
Property Additions			0	0
Purchase of Short-term Investments			(410)	(1,170)
Proceeds from Sales of Short-term Investments			1,070	995
Proceeds from Property Dispositions			0	0
Other Investing Activities			(3)	(11)
Net Cash Used in Investing Activities			657	(186)
Financing Activities
Long-term Debt Issued			0	600
Long-term Debt Repaid			0	(200)
Dividends Paid			(513)	(512)
Stock Options Exercised			0	0
Shares Repurchased			(778)	(546)
Other Financing Activities			(6)	8
Net Cash Used in Financing Activities			(1,297)	(650)
Net Decrease in Cash and Cash Equivalents			4	(199)
Cash and Cash Equivalents at Beginning of Period			444	510
Cash and Cash Equivalents at End of Period	448	311	448	311
CSX Transportation
Operating Activities
Net Cash Provided by (Used in) Operating Activities			2,089	2,313
Investing Activities
Property Additions			(1,469)	(1,794)
Purchase of Short-term Investments			0	0
Proceeds from Sales of Short-term Investments			0	0
Proceeds from Property Dispositions			11	46
Other Investing Activities			96	93
Net Cash Used in Investing Activities			(1,362)	(1,655)
Financing Activities
Long-term Debt Issued			0	0
Long-term Debt Repaid			(18)	(28)
Dividends Paid			(450)	(563)
Stock Options Exercised			0	0
Shares Repurchased			0	0
Other Financing Activities			(304)	1
Net Cash Used in Financing Activities			(772)	(590)
Net Decrease in Cash and Cash Equivalents			(45)	68
Cash and Cash Equivalents at Beginning of Period			175	100
Cash and Cash Equivalents at End of Period	130	168	130	168
Eliminations and Other
Operating Activities
Net Cash Provided by (Used in) Operating Activities			(245)	(438)
Investing Activities
Property Additions			(121)	(115)
Purchase of Short-term Investments			0	0
Proceeds from Sales of Short-term Investments			0	45
Proceeds from Property Dispositions			0	0
Other Investing Activities			(67)	(40)
Net Cash Used in Investing Activities			(188)	(110)
Financing Activities
Long-term Debt Issued			0	0
Long-term Debt Repaid			(1)	0
Dividends Paid			450	563
Stock Options Exercised			0	0
Shares Repurchased			0	0
Other Financing Activities			0	(12)
Net Cash Used in Financing Activities			449	551
Net Decrease in Cash and Cash Equivalents			16	3
Cash and Cash Equivalents at Beginning of Period			9	59
Cash and Cash Equivalents at End of Period	$ 25	$ 62	$ 25	$ 62