Summarized Consolidating Financial Data - Consolidating Cash Flow Statements (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 24, 2016	Jun. 30, 2017	Jun. 24, 2016
Operating Activities
Net Cash Provided by (Used in) Operating Activities			$ 1,566	$ 1,592
Investing Activities
Property Additions			(955)	(1,066)
Purchase of Short-term Investments			(545)	(260)
Proceeds from Sales of Short-term Investments			492	810
Other Investing Activities			41	35
Net Cash Used In Investing Activities			(967)	(481)
Financing Activities
Long-term Debt Issued			850	0
Long-term Debt Repaid			313	0
Dividends Paid			(350)	(344)
Shares Repurchased	$ (499)	$ (266)	(757)	(515)
Other Financing Activities			(12)	(314)
Net Cash Used in Financing Activities			(582)	(1,173)
Net Increase (Decrease) in Cash and Cash Equivalents			17	(62)
Cash and Cash Equivalents at Beginning of Period			603	628
Cash and Cash Equivalents at End of Period	620	566	620	566
Eliminations and Other
Operating Activities
Net Cash Provided by (Used in) Operating Activities			(221)	(152)
Investing Activities
Property Additions			(82)	(72)
Purchase of Short-term Investments			(6)	0
Proceeds from Sales of Short-term Investments			2	0
Other Investing Activities			(8)	(67)
Net Cash Used In Investing Activities			(94)	(139)
Financing Activities
Long-term Debt Issued			0
Long-term Debt Repaid			0
Dividends Paid			300	300
Shares Repurchased			0	0
Other Financing Activities			7	1
Net Cash Used in Financing Activities			307	301
Net Increase (Decrease) in Cash and Cash Equivalents			(8)	10
Cash and Cash Equivalents at Beginning of Period			17	9
Cash and Cash Equivalents at End of Period	9	19	9	19
CSX Corporation
Operating Activities
Net Cash Provided by (Used in) Operating Activities			814	295
Investing Activities
Property Additions			0	0
Purchase of Short-term Investments			(539)	(260)
Proceeds from Sales of Short-term Investments			490	810
Other Investing Activities			(2)	(2)
Net Cash Used In Investing Activities			(51)	548
Financing Activities
Long-term Debt Issued			850
Long-term Debt Repaid			313
Dividends Paid			(350)	(344)
Shares Repurchased			(757)	(515)
Other Financing Activities			(15)	(8)
Net Cash Used in Financing Activities			(585)	(867)
Net Increase (Decrease) in Cash and Cash Equivalents			178	(24)
Cash and Cash Equivalents at Beginning of Period			305	444
Cash and Cash Equivalents at End of Period	483	420	483	420
CSX Transportation
Operating Activities
Net Cash Provided by (Used in) Operating Activities			973	1,449
Investing Activities
Property Additions			(873)	(994)
Purchase of Short-term Investments			0	0
Proceeds from Sales of Short-term Investments			0	0
Other Investing Activities			51	104
Net Cash Used In Investing Activities			(822)	(890)
Financing Activities
Long-term Debt Issued			0
Long-term Debt Repaid			0
Dividends Paid			(300)	(300)
Shares Repurchased			0	0
Other Financing Activities			(4)	(307)
Net Cash Used in Financing Activities			(304)	(607)
Net Increase (Decrease) in Cash and Cash Equivalents			(153)	(48)
Cash and Cash Equivalents at Beginning of Period			281	175
Cash and Cash Equivalents at End of Period	$ 128	$ 127	$ 128	$ 127