Summarized Consolidating Cash Flow Statements (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 29, 2012	Jul. 01, 2011
Operating Activities
Net Cash Provided by (Used in) Operating Activities	$ 1,291	$ 1,585
Investing Activities
Property Additions	(1,223)	(945)
Purchases of Short-term Investments	(58)	(8)
Proceeds from Sales of Short-term Investments	546	42
Other Investing Activities	6	(18)
Net Cash Provided by (Used in) Investing Activities	(729)	(929)
Financing Activities
Long-term Debt Issued	300	600
Long-term Debt Repaid	(455)	(570)
Dividends Paid	(270)	(228)
Stock Options Exercised	10	24
Shares Repurchased	(300)	(528)
Other Financing Activities	12	6
Net Cash Provided by (Used in) Financing Activities	(703)	(696)
Net Increase (Decrease) in Cash and Cash Equivalents	(141)	(40)
Cash and Cash Equivalents at Beginning of Period	783	1,292
Cash and Cash Equivalents at End of Period	642	1,252
CSX Corporation
Operating Activities
Net Cash Provided by (Used in) Operating Activities	37	518
Investing Activities
Property Additions	0	0
Purchases of Short-term Investments	(50)	0
Proceeds from Sales of Short-term Investments	525	0
Other Investing Activities	(3)	(16)
Net Cash Provided by (Used in) Investing Activities	472	(16)
Financing Activities
Long-term Debt Issued	300	600
Long-term Debt Repaid	(400)	(507)
Dividends Paid	(270)	(231)
Stock Options Exercised	10	24
Shares Repurchased	(300)	(528)
Other Financing Activities	7	28
Net Cash Provided by (Used in) Financing Activities	(653)	(614)
Net Increase (Decrease) in Cash and Cash Equivalents	(144)	(112)
Cash and Cash Equivalents at Beginning of Period	549	1,100
Cash and Cash Equivalents at End of Period	405	988
CSX Transportation
Operating Activities
Net Cash Provided by (Used in) Operating Activities	1,445	1,270
Investing Activities
Property Additions	(1,130)	(864)
Purchases of Short-term Investments	0	0
Proceeds from Sales of Short-term Investments	0	0
Other Investing Activities	97	(95)
Net Cash Provided by (Used in) Investing Activities	(1,033)	(959)
Financing Activities
Long-term Debt Issued	0	0
Long-term Debt Repaid	(54)	(61)
Dividends Paid	(357)	(170)
Stock Options Exercised	0	0
Shares Repurchased	0	0
Other Financing Activities	5	(8)
Net Cash Provided by (Used in) Financing Activities	(406)	(239)
Net Increase (Decrease) in Cash and Cash Equivalents	6	72
Cash and Cash Equivalents at Beginning of Period	154	118
Cash and Cash Equivalents at End of Period	160	190
Eliminations and Other
Operating Activities
Net Cash Provided by (Used in) Operating Activities	(191)	(203)
Investing Activities
Property Additions	(93)	(81)
Purchases of Short-term Investments	(8)	(8)
Proceeds from Sales of Short-term Investments	21	42
Other Investing Activities	(88)	93
Net Cash Provided by (Used in) Investing Activities	(168)	46
Financing Activities
Long-term Debt Issued	0	0
Long-term Debt Repaid	(1)	(2)
Dividends Paid	357	173
Stock Options Exercised	0	0
Shares Repurchased	0	0
Other Financing Activities	0	(14)
Net Cash Provided by (Used in) Financing Activities	356	157
Net Increase (Decrease) in Cash and Cash Equivalents	(3)	0
Cash and Cash Equivalents at Beginning of Period	80	74
Cash and Cash Equivalents at End of Period	$ 77	$ 74