Summarized Consolidating Cash Flow Statements (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 28, 2013	Jun. 29, 2012
Operating Activities
Net Cash Provided by (Used in) Operating Activities	$ 1,579	$ 1,291
Investing Activities
Property Additions	(1,085)	(1,223)
Purchase of Short-term Investments	(690)	(58)
Proceeds from Sales of Short-term Investments	904	546
Other Investing Activities	(50)	6
Net Cash Provided by (Used in) Investing Activities	(921)	(729)
Financing Activities
Long-term Debt Issued	0	300
Long-term Debt Repaid	(455)	(455)
Dividends Paid	(296)	(270)
Stock Options Exercised	9	10
Shares Repurchased	(95)	(300)
Other Financing Activities	9	12
Net Cash Used in Financing Activities	(828)	(703)
Net Decrease in Cash and Cash Equivalents	(170)	(141)
Cash and Cash Equivalents at Beginning of Period	784	783
Cash and Cash Equivalents at End of Period	614	642
CSX Corporation [Member]
Operating Activities
Net Cash Provided by (Used in) Operating Activities	582	37
Investing Activities
Property Additions	0	0
Purchase of Short-term Investments	(685)	(50)
Proceeds from Sales of Short-term Investments	840	525
Other Investing Activities	(2)	(3)
Net Cash Provided by (Used in) Investing Activities	153	472
Financing Activities
Long-term Debt Issued		300
Long-term Debt Repaid	(400)	(400)
Dividends Paid	(296)	(270)
Stock Options Exercised	9	10
Shares Repurchased	(95)	(300)
Other Financing Activities	7	7
Net Cash Used in Financing Activities	(775)	(653)
Net Decrease in Cash and Cash Equivalents	(40)	(144)
Cash and Cash Equivalents at Beginning of Period	481	549
Cash and Cash Equivalents at End of Period	441	405
CSX Transportation [Member]
Operating Activities
Net Cash Provided by (Used in) Operating Activities	1,319	1,445
Investing Activities
Property Additions	(988)	(1,130)
Purchase of Short-term Investments	0	0
Proceeds from Sales of Short-term Investments	0	0
Other Investing Activities	(35)	97
Net Cash Provided by (Used in) Investing Activities	(1,023)	(1,033)
Financing Activities
Long-term Debt Issued		0
Long-term Debt Repaid	(55)	(54)
Dividends Paid	(365)	(357)
Stock Options Exercised	0	0
Shares Repurchased	0	0
Other Financing Activities	4	5
Net Cash Used in Financing Activities	(416)	(406)
Net Decrease in Cash and Cash Equivalents	(120)	6
Cash and Cash Equivalents at Beginning of Period	235	154
Cash and Cash Equivalents at End of Period	115	160
Eliminations and Other [Member]
Operating Activities
Net Cash Provided by (Used in) Operating Activities	(322)	(191)
Investing Activities
Property Additions	(97)	(93)
Purchase of Short-term Investments	(5)	(8)
Proceeds from Sales of Short-term Investments	64	21
Other Investing Activities	(13)	(88)
Net Cash Provided by (Used in) Investing Activities	(51)	(168)
Financing Activities
Long-term Debt Issued		0
Long-term Debt Repaid	0	(1)
Dividends Paid	365	357
Stock Options Exercised	0	0
Shares Repurchased	0	0
Other Financing Activities	(2)	0
Net Cash Used in Financing Activities	363	356
Net Decrease in Cash and Cash Equivalents	(10)	(3)
Cash and Cash Equivalents at Beginning of Period	68	80
Cash and Cash Equivalents at End of Period	$ 58	$ 77