Summarized Consolidating Financial Data (Consolidating Income Statement) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 30, 2016	Sep. 23, 2016	Jun. 24, 2016	Mar. 25, 2016	Dec. 31, 2017	Dec. 30, 2016	Dec. 25, 2015
Consolidated Income Statement
Revenue	$ 2,863	$ 2,743	$ 2,933	$ 2,869	$ 3,037	$ 2,710	$ 2,704	$ 2,618	$ 11,408	$ 11,069	$ 11,811
Expense									7,741	7,680	8,227
Operating Income	1,121	876	958	712	1,004	841	840	704	3,667	3,389	3,584
Equity in Earnings of Subsidiaries									0	0	0
Interest Expense									(546)	(579)	(544)
Other Income - Net									21	(69)	98
Earnings Before Income Taxes									3,142	2,741	3,138
Income Tax Benefit									2,329	(1,027)	(1,170)
Net Earnings	$ 4,140	$ 459	$ 510	$ 362	$ 458	$ 455	$ 445	$ 356	5,471	1,714	1,968
Total Comprehensive Earnings									5,625	1,739	1,969
Eliminations and Other
Consolidated Income Statement
Revenue									74	78	78
Expense									(171)	(155)	(106)
Operating Income									245	233	184
Equity in Earnings of Subsidiaries									(5,810)	(1,999)	(1,949)
Interest Expense									65	39	28
Other Income - Net									(28)	(1)	(9)
Earnings Before Income Taxes									(5,528)	(1,728)	(1,746)
Income Tax Benefit									4	(93)	(60)
Net Earnings									(5,524)	(1,821)	(1,806)
Total Comprehensive Earnings									(5,538)	(1,833)	(1,806)
CSX Corporation
Consolidated Income Statement
Revenue									0	0	0
Expense									(158)	(265)	(589)
Operating Income									158	265	589
Equity in Earnings of Subsidiaries									5,810	1,997	1,949
Interest Expense									(582)	(583)	(539)
Other Income - Net									7	(112)	(4)
Earnings Before Income Taxes									5,393	1,567	1,995
Income Tax Benefit									78	147	(27)
Net Earnings									5,471	1,714	1,968
Total Comprehensive Earnings									5,625	1,739	1,969
CSX Transportation
Consolidated Income Statement
Revenue									11,334	10,991	11,733
Expense									8,070	8,100	8,922
Operating Income									3,264	2,891	2,811
Equity in Earnings of Subsidiaries									0	2	0
Interest Expense									(29)	(35)	(33)
Other Income - Net									42	44	111
Earnings Before Income Taxes									3,277	2,902	2,889
Income Tax Benefit									2,247	(1,081)	(1,083)
Net Earnings									5,524	1,821	1,806
Total Comprehensive Earnings									$ 5,538	$ 1,833	$ 1,806