Summarized Consolidating Financial Data - Consolidating Cash Flow Statements (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 25, 2016	Mar. 27, 2015
Operating Activities
Net Cash Provided by (Used in) Operating Activities	$ 754	$ 690
Investing Activities
Property Additions	(425)	(598)
Purchase of Short-term Investments	(235)	(105)
Proceeds from Sales of Short-term Investments	670	140
Other Investing Activities	31	63
Net Cash Provided by (Used in) Investing Activities	41	(500)
Financing Activities
Dividends Paid	(173)	(158)
Shares Repurchased	(249)	(127)
Other Financing Activities	(270)	(13)
Net Cash Used in Financing Activities	(692)	(298)
Net Increase (Decrease) in Cash and Cash Equivalents	103	(108)
Cash and Cash Equivalents at Beginning of Period	628	669
Cash and Cash Equivalents at End of Period	731	561
CSX Corporation
Operating Activities
Net Cash Provided by (Used in) Operating Activities	36	134
Investing Activities
Property Additions	0	0
Purchase of Short-term Investments	(235)	(105)
Proceeds from Sales of Short-term Investments	670	105
Other Investing Activities	(1)	0
Net Cash Provided by (Used in) Investing Activities	434	0
Financing Activities
Dividends Paid	(173)	(158)
Shares Repurchased	(249)	(127)
Other Financing Activities	1	4
Net Cash Used in Financing Activities	(421)	(281)
Net Increase (Decrease) in Cash and Cash Equivalents	49	(147)
Cash and Cash Equivalents at Beginning of Period	444	510
Cash and Cash Equivalents at End of Period	493	363
CSX Transportation
Operating Activities
Net Cash Provided by (Used in) Operating Activities	834	871
Investing Activities
Property Additions	(391)	(574)
Purchase of Short-term Investments	0	0
Proceeds from Sales of Short-term Investments	0	0
Other Investing Activities	26	(50)
Net Cash Provided by (Used in) Investing Activities	(365)	(624)
Financing Activities
Dividends Paid	(150)	(188)
Shares Repurchased	0	0
Other Financing Activities	(271)	(17)
Net Cash Used in Financing Activities	(421)	(205)
Net Increase (Decrease) in Cash and Cash Equivalents	48	42
Cash and Cash Equivalents at Beginning of Period	175	100
Cash and Cash Equivalents at End of Period	223	142
Eliminations and Other
Operating Activities
Net Cash Provided by (Used in) Operating Activities	(116)	(315)
Investing Activities
Property Additions	(34)	(24)
Purchase of Short-term Investments	0	0
Proceeds from Sales of Short-term Investments	0	35
Other Investing Activities	6	113
Net Cash Provided by (Used in) Investing Activities	(28)	124
Financing Activities
Dividends Paid	150	188
Shares Repurchased	0	0
Other Financing Activities	0	0
Net Cash Used in Financing Activities	150	188
Net Increase (Decrease) in Cash and Cash Equivalents	6	(3)
Cash and Cash Equivalents at Beginning of Period	9	59
Cash and Cash Equivalents at End of Period	$ 15	$ 56