Summarized Consolidating Cash Flow Statements (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 30, 2012	Apr. 01, 2011
Operating Activities
Net Cash Provided by (Used in) Operating Activities	$ 444	$ 495
Investing Activities
Property Additions	(469)	(379)
Purchases of Short-term Investments	(53)	(8)
Proceeds from Sales of Short-term Investments	437	20
Other Investing Activities	8	2
Net Cash Provided by (Used in) Investing Activities	(77)	(365)
Financing Activities
Long-term Debt Issued	300	0
Long-term Debt Repaid	(413)	(524)
Dividends Paid	(125)	(96)
Stock Options Exercised	8	19
Shares Repurchased	(300)	(300)
Other Financing Activities	7	13
Net Cash Provided by (Used in) Financing Activities	(523)	(888)
Net Increase (Decrease) in Cash and Cash Equivalents	(156)	(758)
Cash and Cash Equivalents at Beginning of Period	783	1,292
Cash and Cash Equivalents at End of Period	627	534
CSX Corporation
Operating Activities
Net Cash Provided by (Used in) Operating Activities	(23)	196
Investing Activities
Property Additions	0	0
Purchases of Short-term Investments	(50)	0
Proceeds from Sales of Short-term Investments	425	0
Other Investing Activities	1	(13)
Net Cash Provided by (Used in) Investing Activities	376	(13)
Financing Activities
Long-term Debt Issued	300
Long-term Debt Repaid	(400)	(507)
Dividends Paid	(125)	(96)
Stock Options Exercised	8	19
Shares Repurchased	(300)	(300)
Other Financing Activities	0	22
Net Cash Provided by (Used in) Financing Activities	(517)	(862)
Net Increase (Decrease) in Cash and Cash Equivalents	(164)	(679)
Cash and Cash Equivalents at Beginning of Period	549	1,100
Cash and Cash Equivalents at End of Period	385	421
CSX Transportation
Operating Activities
Net Cash Provided by (Used in) Operating Activities	641	541
Investing Activities
Property Additions	(435)	(344)
Purchases of Short-term Investments	0	0
Proceeds from Sales of Short-term Investments	0	0
Other Investing Activities	(13)	(85)
Net Cash Provided by (Used in) Investing Activities	(448)	(429)
Financing Activities
Long-term Debt Issued	0
Long-term Debt Repaid	(13)	(16)
Dividends Paid	(179)	(170)
Stock Options Exercised	0	0
Shares Repurchased	0	0
Other Financing Activities	4	0
Net Cash Provided by (Used in) Financing Activities	(188)	(186)
Net Increase (Decrease) in Cash and Cash Equivalents	5	(74)
Cash and Cash Equivalents at Beginning of Period	154	118
Cash and Cash Equivalents at End of Period	159	44
Eliminations and Other
Operating Activities
Net Cash Provided by (Used in) Operating Activities	(174)	(242)
Investing Activities
Property Additions	(34)	(35)
Purchases of Short-term Investments	(3)	(8)
Proceeds from Sales of Short-term Investments	12	20
Other Investing Activities	20	100
Net Cash Provided by (Used in) Investing Activities	(5)	77
Financing Activities
Long-term Debt Issued	0
Long-term Debt Repaid	0	(1)
Dividends Paid	179	170
Stock Options Exercised	0	0
Shares Repurchased	0	0
Other Financing Activities	3	(9)
Net Cash Provided by (Used in) Financing Activities	182	160
Net Increase (Decrease) in Cash and Cash Equivalents	3	(5)
Cash and Cash Equivalents at Beginning of Period	80	74
Cash and Cash Equivalents at End of Period	$ 83	$ 69