Summarized Consolidating Financial Data (Consolidating Balance Sheets) (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 30, 2016
Current Assets:
Cash and Cash Equivalents	$ 958	$ 858	$ 401	$ 603
Short-term Investments	996	253
Accounts Receivable - Net	986	1,010
Receivable from Affiliates	0	0
Materials and Supplies	261	263
Other Current Assets	77	181
Total Current Assets	3,278	2,565
Properties	45,100	44,805
Accumulated Depreciation	(12,932)	(12,807)
Properties - Net (Note 6)	32,168	31,998
Right of Use Lease Asset (Note 7)	532	0
Other Long-term Assets	400	387
Total Assets	38,257	36,729
Current Liabilities:
Accounts Payable	1,043	949
Labor and Fringe Benefits Payable	489	550
Payable to Affiliates	0	0
Casualty, Environmental and Other Reserves	100	113
Current Maturities of Long-term Debt	245	18
Income and Other Taxes Payable	69	106
Other Current Liabilities	205	179
Total Current Liabilities	2,151	1,915
Casualty, Environmental and Other Reserves	205	211
Long-term Debt	15,993	14,739
Deferred Income Taxes - Net	6,961	6,690
Long-term lease liabilities	493	0
Other Long-term Liabilities	591	594
Total Liabilities	26,394	24,149
Shareholders' Equity:
Common Stock, $1 Par Value	773	818
Other Capital	346	249
Retained Earnings	11,404	12,157
Accumulated Other Comprehensive Loss	(675)	(661)
Noncontrolling Minority Interest	15	17
Total Shareholders' Equity	11,863	12,580	14,721	11,694
Total Liabilities and Shareholders' Equity	$ 38,257	$ 36,729
Common stock par value (in dollars per share)	$ 1	$ 1
Investments in Conrail
Current Assets:
Investment in Affiliates and Other Companies		$ 943
Affiliates and Other Companies
Current Assets:
Investment in Affiliates and Other Companies	$ 897	836
Investment in Consolidated Subsidiaries
Current Assets:
Investment in Affiliates and Other Companies	0	0
Eliminations and Other
Current Assets:
Cash and Cash Equivalents	8	12	6	17
Short-term Investments	7	3
Accounts Receivable - Net	13	6
Receivable from Affiliates	(8,459)	(6,234)
Materials and Supplies	0	0
Other Current Assets	21	14
Total Current Assets	(8,410)	(6,199)
Properties	2,989	2,907
Accumulated Depreciation	(1,732)	(1,612)
Properties - Net (Note 6)	1,257	1,295
Right of Use Lease Asset (Note 7)	18
Other Long-term Assets	(232)	(213)
Total Assets	(40,900)	(36,191)
Current Liabilities:
Accounts Payable	60	54
Labor and Fringe Benefits Payable	65	69
Payable to Affiliates	(10,126)	(7,606)
Casualty, Environmental and Other Reserves	13	14
Current Maturities of Long-term Debt	0	0
Income and Other Taxes Payable	15	4
Other Current Liabilities	13	6
Total Current Liabilities	(9,960)	(7,459)
Casualty, Environmental and Other Reserves	36	35
Long-term Debt	0	0
Deferred Income Taxes - Net	286	223
Long-term lease liabilities	12
Other Long-term Liabilities	(316)	(338)
Total Liabilities	(9,942)	(7,539)
Shareholders' Equity:
Common Stock, $1 Par Value	(181)	(181)
Other Capital	(5,096)	(5,096)
Retained Earnings	(25,646)	(23,322)
Accumulated Other Comprehensive Loss	(35)	(53)
Noncontrolling Minority Interest	0	0
Total Shareholders' Equity	(30,958)	(28,652)
Total Liabilities and Shareholders' Equity	(40,900)	(36,191)
Eliminations and Other | Investments in Conrail
Current Assets:
Investment in Affiliates and Other Companies	982	943
Eliminations and Other | Affiliates and Other Companies
Current Assets:
Investment in Affiliates and Other Companies	13	16
Eliminations and Other | Investment in Consolidated Subsidiaries
Current Assets:
Investment in Affiliates and Other Companies	(34,528)	(32,033)
CSX Corporation
Current Assets:
Cash and Cash Equivalents	814	716	274	305
Short-term Investments	989	250
Accounts Receivable - Net	4	1
Receivable from Affiliates	1,054	1,020
Materials and Supplies	0	0
Other Current Assets	26	63
Total Current Assets	2,887	2,050
Properties	1	1
Accumulated Depreciation	(1)	(1)
Properties - Net (Note 6)	0	0
Right of Use Lease Asset (Note 7)	0
Other Long-term Assets	3	2
Total Assets	37,379	34,046
Current Liabilities:
Accounts Payable	153	132
Labor and Fringe Benefits Payable	38	41
Payable to Affiliates	9,552	6,973
Casualty, Environmental and Other Reserves	0	0
Current Maturities of Long-term Debt	0	0
Income and Other Taxes Payable	(286)	(290)
Other Current Liabilities	0	11
Total Current Liabilities	9,457	6,867
Casualty, Environmental and Other Reserves	0	0
Long-term Debt	15,534	14,029
Deferred Income Taxes - Net	(152)	(134)
Long-term lease liabilities	0
Other Long-term Liabilities	692	721
Total Liabilities	25,531	21,483
Shareholders' Equity:
Common Stock, $1 Par Value	773	818
Other Capital	346	249
Retained Earnings	11,404	12,157
Accumulated Other Comprehensive Loss	(675)	(661)
Noncontrolling Minority Interest	0	0
Total Shareholders' Equity	11,848	12,563
Total Liabilities and Shareholders' Equity	37,379	34,046
CSX Corporation | Investments in Conrail
Current Assets:
Investment in Affiliates and Other Companies	0	0
CSX Corporation | Affiliates and Other Companies
Current Assets:
Investment in Affiliates and Other Companies	(39)	(39)
CSX Corporation | Investment in Consolidated Subsidiaries
Current Assets:
Investment in Affiliates and Other Companies	34,528	32,033
CSX Transportation
Current Assets:
Cash and Cash Equivalents	136	130	$ 121	$ 281
Short-term Investments	0	0
Accounts Receivable - Net	969	1,003
Receivable from Affiliates	7,405	5,214
Materials and Supplies	261	263
Other Current Assets	30	104
Total Current Assets	8,801	6,714
Properties	42,110	41,897
Accumulated Depreciation	(11,199)	(11,194)
Properties - Net (Note 6)	30,911	30,703
Right of Use Lease Asset (Note 7)	514
Other Long-term Assets	629	598
Total Assets	41,778	38,874
Current Liabilities:
Accounts Payable	830	763
Labor and Fringe Benefits Payable	386	440
Payable to Affiliates	574	633
Casualty, Environmental and Other Reserves	87	99
Current Maturities of Long-term Debt	245	18
Income and Other Taxes Payable	340	392
Other Current Liabilities	192	162
Total Current Liabilities	2,654	2,507
Casualty, Environmental and Other Reserves	169	176
Long-term Debt	459	710
Deferred Income Taxes - Net	6,827	6,601
Long-term lease liabilities	481
Other Long-term Liabilities	215	211
Total Liabilities	10,805	10,205
Shareholders' Equity:
Common Stock, $1 Par Value	181	181
Other Capital	5,096	5,096
Retained Earnings	25,646	23,322
Accumulated Other Comprehensive Loss	35	53
Noncontrolling Minority Interest	15	17
Total Shareholders' Equity	30,973	28,669
Total Liabilities and Shareholders' Equity	41,778	38,874
CSX Transportation | Investments in Conrail
Current Assets:
Investment in Affiliates and Other Companies	0	0
CSX Transportation | Affiliates and Other Companies
Current Assets:
Investment in Affiliates and Other Companies	923	859
CSX Transportation | Investment in Consolidated Subsidiaries
Current Assets:
Investment in Affiliates and Other Companies	$ 0	$ 0