Summarized Consolidating Financial Data (Consolidating Income Statement) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 30, 2016
Consolidated Income Statement
Revenue	$ 3,143	$ 3,129	$ 3,102	$ 2,876	$ 2,863	$ 2,743	$ 2,933	$ 2,869	$ 12,250	$ 11,408	$ 11,069
Expense									7,381	7,688	7,656
Operating Income	1,249	1,293	1,283	1,044	1,126	868	957	769	4,869	3,720	3,413
Equity in Earnings of Subsidiaries									0	0	0
Interest Expense									(639)	(546)	(579)
Other Income - Net									74	(32)	(93)
Earnings Before Income Taxes									4,304	3,142	2,741
Income Tax Benefit (Expense)									(995)	2,329	(1,027)
Net Earnings	$ 843	$ 894	$ 877	$ 695	$ 4,140	$ 459	$ 510	$ 362	3,309	5,471	1,714
Total Comprehensive Earnings									3,134	5,625	1,739
Eliminations and Other
Consolidated Income Statement
Revenue									76	74	78
Expense									(143)	(163)	(165)
Operating Income									219	237	243
Equity in Earnings of Subsidiaries									(3,580)	(5,810)	(1,999)
Interest Expense									142	65	39
Other Income - Net									(102)	(20)	(11)
Earnings Before Income Taxes									(3,321)	(5,528)	(1,728)
Income Tax Benefit (Expense)									(62)	4	(93)
Net Earnings									(3,383)	(5,524)	(1,821)
Total Comprehensive Earnings									(3,441)	(5,538)	(1,833)
CSX Corporation
Consolidated Income Statement
Revenue									0	0	0
Expense									(344)	(158)	(265)
Operating Income									344	158	265
Equity in Earnings of Subsidiaries									3,580	5,810	1,997
Interest Expense									(742)	(582)	(583)
Other Income - Net									24	7	(112)
Earnings Before Income Taxes									3,206	5,393	1,567
Income Tax Benefit (Expense)									103	78	147
Net Earnings									3,309	5,471	1,714
Total Comprehensive Earnings									3,134	5,625	1,739
CSX Transportation
Consolidated Income Statement
Revenue									12,174	11,334	10,991
Expense									7,868	8,009	8,086
Operating Income									4,306	3,325	2,905
Equity in Earnings of Subsidiaries									0	0	2
Interest Expense									(39)	(29)	(35)
Other Income - Net									152	(19)	30
Earnings Before Income Taxes									4,419	3,277	2,902
Income Tax Benefit (Expense)									(1,036)	2,247	(1,081)
Net Earnings									3,383	5,524	1,821
Total Comprehensive Earnings									$ 3,441	$ 5,538	$ 1,833