Summarized Consolidating Financial Data (Cash Flow Statements) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 26, 2014	Dec. 27, 2013	Dec. 28, 2012
Operating Activities
Net Cash Provided by Operating Activities	$ 3,343	$ 3,267	$ 2,946
Investing Activities
Property Additions	(2,449)	(2,313)	(2,341)
Purchase of Short-term Investments	(1,433)	(1,256)	(633)
Proceeds from Sales of Short-term Investments	1,674	1,401	581
Proceeds from Property Dispositions	62	53	186
Other Investing Activities	(37)	(112)	(70)
Net Cash Used in Investing Activities	(2,183)	(2,227)	(2,277)
Financing Activities
Long-term Debt Issued	1,000	500	1,100
Long-term Debt Repaid	(933)	(780)	(508)
Payments of Ordinary Dividends, Common Stock	(629)	(600)	(558)
Stock Options Exercised	0	9	14
Shares acquired, repurchase amount	(517)	(353)	(734)
Other Financing Activities	(4)	(8)	18
Net Cash Used in Financing Activities	(1,083)	(1,232)	(668)
Net (Decrease) Increase in Cash and Cash Equivalents	77	(192)	1
Cash and Cash Equivalents at Beginning of Period	592	784	783
Cash and Cash Equivalents at End of Period	669	592	784
CSX Corporation
Operating Activities
Net Cash Provided by Operating Activities	583	1,004	579
Investing Activities
Property Additions	0	0	0
Purchase of Short-term Investments	(1,419)	(1,251)	(605)
Proceeds from Sales of Short-term Investments	1,642	1,335	525
Proceeds from Property Dispositions	0	0	0
Other Investing Activities	0	(134)	(10)
Net Cash Used in Investing Activities	223	(50)	(90)
Financing Activities
Long-term Debt Issued	1,000	500	1,100
Long-term Debt Repaid	(600)	(700)	(400)
Payments of Ordinary Dividends, Common Stock	(629)	(600)	(558)
Stock Options Exercised	0	9	14
Shares acquired, repurchase amount	(517)	(353)	(734)
Other Financing Activities	11	148	21
Net Cash Used in Financing Activities	(735)	(996)	(557)
Net (Decrease) Increase in Cash and Cash Equivalents	71	(42)	(68)
Cash and Cash Equivalents at Beginning of Period	439	481	549
Cash and Cash Equivalents at End of Period	510	439	481
CSX Transportation
Operating Activities
Net Cash Provided by Operating Activities	3,278	3,005	2,716
Investing Activities
Property Additions	(2,192)	(2,053)	(2,104)
Purchase of Short-term Investments	0	0	0
Proceeds from Sales of Short-term Investments	0	0	0
Proceeds from Property Dispositions	62	53	186
Other Investing Activities	(128)	(315)	102
Net Cash Used in Investing Activities	(2,258)	(2,315)	(1,816)
Financing Activities
Long-term Debt Issued	0	0	0
Long-term Debt Repaid	(333)	(80)	(106)
Payments of Ordinary Dividends, Common Stock	(660)	(730)	(715)
Stock Options Exercised	0	0	0
Shares acquired, repurchase amount	0	0	0
Other Financing Activities	(18)	(24)	2
Net Cash Used in Financing Activities	(1,011)	(834)	(819)
Net (Decrease) Increase in Cash and Cash Equivalents	9	(144)	81
Cash and Cash Equivalents at Beginning of Period	91	235	154
Cash and Cash Equivalents at End of Period	100	91	235
Eliminations and Other
Operating Activities
Net Cash Provided by Operating Activities	(518)	(742)	(349)
Investing Activities
Property Additions	(257)	(260)	(237)
Purchase of Short-term Investments	(14)	(5)	(28)
Proceeds from Sales of Short-term Investments	32	66	56
Proceeds from Property Dispositions	0	0	0
Other Investing Activities	91	337	(162)
Net Cash Used in Investing Activities	(148)	138	(371)
Financing Activities
Long-term Debt Issued	0	0	0
Long-term Debt Repaid	0	0	(2)
Payments of Ordinary Dividends, Common Stock	660	730	715
Stock Options Exercised	0	0	0
Shares acquired, repurchase amount	0	0	0
Other Financing Activities	3	(132)	(5)
Net Cash Used in Financing Activities	663	598	708
Net (Decrease) Increase in Cash and Cash Equivalents	(3)	(6)	(12)
Cash and Cash Equivalents at Beginning of Period	62	68	80
Cash and Cash Equivalents at End of Period	$ 59	$ 62	$ 68