Summarized Consolidating Financial Data - Consolidating Cash Flow Statements (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 27, 2015	Mar. 28, 2014
Operating Activities
Net Cash Provided by (Used in) Operating Activities	$ 690	$ 599
Investing Activities
Property Additions	(598)	(475)
Purchase of Short-term Investments	(105)	(165)
Proceeds from Sales of Short-term Investments	140	409
Other Investing Activities	63	4
Net Cash Used in Investing Activities	(500)	(227)
Financing Activities
Repayments of Debt and Capital Lease Obligations	0	209
Dividends Paid	(158)	(151)
Shares Repurchased	(127)	(127)
Other Financing Activities	(13)	(2)
Net Cash Used in Financing Activities	(298)	(489)
Net Decrease in Cash and Cash Equivalents	(108)	(117)
Cash and Cash Equivalents at Beginning of Period	669	592
Cash and Cash Equivalents at End of Period	561	475
CSX Corporation
Operating Activities
Net Cash Provided by (Used in) Operating Activities	134	113
Investing Activities
Property Additions	0	0
Purchase of Short-term Investments	(105)	(165)
Proceeds from Sales of Short-term Investments	105	407
Other Investing Activities	0	0
Net Cash Used in Investing Activities	0	242
Financing Activities
Repayments of Debt and Capital Lease Obligations		200
Dividends Paid	(158)	(151)
Shares Repurchased	(127)	(127)
Other Financing Activities	4	5
Net Cash Used in Financing Activities	(281)	(473)
Net Decrease in Cash and Cash Equivalents	(147)	(118)
Cash and Cash Equivalents at Beginning of Period	510	439
Cash and Cash Equivalents at End of Period	363	321
CSX Transportation
Operating Activities
Net Cash Provided by (Used in) Operating Activities	871	669
Investing Activities
Property Additions	(574)	(443)
Purchase of Short-term Investments	0	0
Proceeds from Sales of Short-term Investments	0	0
Other Investing Activities	(50)	(67)
Net Cash Used in Investing Activities	(624)	(510)
Financing Activities
Repayments of Debt and Capital Lease Obligations		9
Dividends Paid	(188)	(143)
Shares Repurchased	0	0
Other Financing Activities	(17)	(7)
Net Cash Used in Financing Activities	(205)	(159)
Net Decrease in Cash and Cash Equivalents	42	0
Cash and Cash Equivalents at Beginning of Period	100	91
Cash and Cash Equivalents at End of Period	142	91
Eliminations and Other
Operating Activities
Net Cash Provided by (Used in) Operating Activities	(315)	(183)
Investing Activities
Property Additions	(24)	(32)
Purchase of Short-term Investments	0	0
Proceeds from Sales of Short-term Investments	35	2
Other Investing Activities	113	71
Net Cash Used in Investing Activities	124	41
Financing Activities
Repayments of Debt and Capital Lease Obligations		0
Dividends Paid	188	143
Shares Repurchased	0	0
Other Financing Activities	0	0
Net Cash Used in Financing Activities	188	143
Net Decrease in Cash and Cash Equivalents	(3)	1
Cash and Cash Equivalents at Beginning of Period	59	62
Cash and Cash Equivalents at End of Period	$ 56	$ 63