Summarized Consolidating Financial Data (Consolidating Income Statement) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Consolidated Income Statement
Revenue	$ 2,885	$ 2,978	$ 3,061	$ 3,013	$ 3,143	$ 3,129	$ 3,102	$ 2,876	$ 11,937	$ 12,250	$ 11,408
Expense									6,972	7,381	7,688
Operating Income	1,154	1,287	1,305	1,219	1,249	1,293	1,283	1,044	4,965	4,869	3,720
Equity in Earnings of Subsidiaries									0	0	0
Interest Expense									(737)	(639)	(546)
Other Income - Net									88	74	(32)
Earnings Before Income Taxes									4,316	4,304	3,142
Income Tax Benefit (Expense)									(985)	(995)	2,329
Net Earnings	$ 771	$ 856	$ 870	$ 834	$ 843	$ 894	$ 877	$ 695	3,331	3,309	5,471
Total Comprehensive Earnings									3,317	3,134	5,625
Eliminations and Other
Consolidated Income Statement
Revenue									81	76	74
Expense									(167)	(143)	(163)
Operating Income									248	219	237
Equity in Earnings of Subsidiaries									(3,505)	(3,580)	(5,810)
Interest Expense									183	142	65
Other Income - Net									(144)	(102)	(20)
Earnings Before Income Taxes									(3,218)	(3,321)	(5,528)
Income Tax Benefit (Expense)									(106)	(62)	4
Net Earnings									(3,324)	(3,383)	(5,524)
Total Comprehensive Earnings									(3,306)	(3,441)	(5,538)
CSX Corporation
Consolidated Income Statement
Revenue									0	0	0
Expense									(549)	(344)	(158)
Operating Income									549	344	158
Equity in Earnings of Subsidiaries									3,505	3,580	5,810
Interest Expense									(878)	(742)	(582)
Other Income - Net									25	24	7
Earnings Before Income Taxes									3,201	3,206	5,393
Income Tax Benefit (Expense)									130	103	78
Net Earnings									3,331	3,309	5,471
Total Comprehensive Earnings									3,317	3,134	5,625
CSX Transportation
Consolidated Income Statement
Revenue									11,856	12,174	11,334
Expense									7,688	7,868	8,009
Operating Income									4,168	4,306	3,325
Equity in Earnings of Subsidiaries									0	0	0
Interest Expense									(42)	(39)	(29)
Other Income - Net									207	152	(19)
Earnings Before Income Taxes									4,333	4,419	3,277
Income Tax Benefit (Expense)									(1,009)	(1,036)	2,247
Net Earnings									3,324	3,383	5,524
Total Comprehensive Earnings									$ 3,306	$ 3,441	$ 5,538