Summarized Consolidating Financial Data (Cash Flow Statements) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 28, 2012	Dec. 30, 2011	Dec. 31, 2010
Operating Activities
Net Cash Provided by (Used in) Operating Activities	$ 2,946	$ 3,491	$ 3,261
Investing Activities
Property Additions	(2,341)	(2,297)	(1,840)
Purchase of Short-term Investments	(633)	(492)	0
Proceeds from Sales of Short-term Investments	581	74	41
Proceeds from Property Dispositions	186	240	108
Other Investing Activities	(70)	(112)	(80)
Net Cash Used in Investing Activities	(2,277)	(2,587)	(1,771)
Financing Activities
Long-term Debt Issued	1,100	1,200	800
Long-term Debt Repaid	(508)	(605)	(113)
Dividends Paid	(558)	(480)	(372)
Stock Options Exercised	14	29	42
Shares Repurchased	(734)	(1,564)	(1,452)
Other Financing Activities	18	7	(132)
Net Cash Used in Financing Activities	(668)	(1,413)	(1,227)
Net Increase (Decrease) in Cash and Cash Equivalents	1	(509)	263
Cash and Cash Equivalents at Beginning of Period	783	1,292	1,029
Cash and Cash Equivalents at End of Period	784	783	1,292
CSX Corporation
Operating Activities
Net Cash Provided by (Used in) Operating Activities	579	1,231	944
Investing Activities
Property Additions	0	0	0
Purchase of Short-term Investments	(605)	(475)	0
Proceeds from Sales of Short-term Investments	525	0	0
Proceeds from Property Dispositions	0	0	0
Other Investing Activities	(10)	(20)	301
Net Cash Used in Investing Activities	(90)	(495)	301
Financing Activities
Long-term Debt Issued	1,100	1,200	800
Long-term Debt Repaid	(400)	(507)	0
Dividends Paid	(558)	(480)	(372)
Stock Options Exercised	14	29	42
Shares Repurchased	(734)	(1,564)	(1,452)
Other Financing Activities	21	35	(81)
Net Cash Used in Financing Activities	(557)	(1,287)	(1,063)
Net Increase (Decrease) in Cash and Cash Equivalents	(68)	(551)	182
Cash and Cash Equivalents at Beginning of Period	549	1,100	918
Cash and Cash Equivalents at End of Period	481	549	1,100
CSX Transportation
Operating Activities
Net Cash Provided by (Used in) Operating Activities	2,716	2,746	2,393
Investing Activities
Property Additions	(2,104)	(2,034)	(1,587)
Purchase of Short-term Investments	0	0	0
Proceeds from Sales of Short-term Investments	0	0	0
Proceeds from Property Dispositions	186	239	107
Other Investing Activities	102	(133)	(110)
Net Cash Used in Investing Activities	(1,816)	(1,928)	(1,590)
Financing Activities
Long-term Debt Issued	0	0	0
Long-term Debt Repaid	(106)	(95)	(111)
Dividends Paid	(715)	(680)	(590)
Stock Options Exercised	0	0	0
Shares Repurchased	0	0	0
Other Financing Activities	2	(7)	(14)
Net Cash Used in Financing Activities	(819)	(782)	(715)
Net Increase (Decrease) in Cash and Cash Equivalents	81	36	88
Cash and Cash Equivalents at Beginning of Period	154	118	30
Cash and Cash Equivalents at End of Period	235	154	118
Eliminations and Other
Operating Activities
Net Cash Provided by (Used in) Operating Activities	(349)	(486)	(76)
Investing Activities
Property Additions	(237)	(263)	(253)
Purchase of Short-term Investments	(28)	(17)	0
Proceeds from Sales of Short-term Investments	56	74	41
Proceeds from Property Dispositions	0	1	1
Other Investing Activities	(162)	41	(271)
Net Cash Used in Investing Activities	(371)	(164)	(482)
Financing Activities
Long-term Debt Issued	0	0	0
Long-term Debt Repaid	(2)	(3)	(2)
Dividends Paid	715	680	590
Stock Options Exercised	0	0	0
Shares Repurchased	0	0	0
Other Financing Activities	(5)	(21)	(37)
Net Cash Used in Financing Activities	708	656	551
Net Increase (Decrease) in Cash and Cash Equivalents	(12)	6	(7)
Cash and Cash Equivalents at Beginning of Period	80	74	81
Cash and Cash Equivalents at End of Period	$ 68	$ 80	$ 74