Summarized Consolidating Financial Data - Consolidating Balance Sheet (Details) - USD ($) $ / shares in Units, $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019		Dec. 31, 2018
Current Assets:
Cash and Cash Equivalents	$ 1,995	$ 958	$ 1,188	[1]	$ 858	[1]
Short-term Investments	487	996
Accounts Receivable - Net	1,008	986
Receivable from Affiliates	0	0
Materials and Supplies	257	261
Other Current Assets	74	77
Total Current Assets	3,821	3,278
Properties	45,065	45,100
Accumulated Depreciation	(12,877)	(12,932)
Properties - Net	32,188	32,168
Right-of-Use Lease Asset	523	532
Other Long-term Assets	401	400
Total Assets	38,834	38,257
Current Liabilities:
Accounts Payable	1,058	1,043
Labor and Fringe Benefits Payable	345	489
Payable to Affiliates	0	0
Casualty, Environmental and Other Reserves	99	100
Current Maturities of Long-term Debt	255	245
Income and Other Taxes Payable	269	69
Other Current Liabilities	185	205
Total Current Liabilities	2,211	2,151
Casualty, Environmental and Other Reserves	210	205
Long-term Debt	16,477	15,993
Deferred Income Taxes - Net	6,991	6,961
Long-term Lease Liability	489	493
Other Long-term Liabilities	568	591
Total Liabilities	26,946	26,394
Shareholders' Equity
Common Stock, $1 Par Value	765	773
Other Capital	366	346
Retained Earnings	11,412	11,404
Accumulated Other Comprehensive Loss	(672)	(675)
Noncontrolling Interest	17	15
Total Shareholders' Equity	11,888	11,863	12,445		12,580
Total Liabilities and Shareholders' Equity	$ 38,834	$ 38,257
Common stock, par value (in dollars per share)	$ 1	$ 1
Investments in Conrail
Current Assets:
Investment in Affiliates and Other Companies	$ 993	$ 982
Affiliates and Other Companies
Current Assets:
Investment in Affiliates and Other Companies	908	897
Investments in Consolidated Subsidiaries
Current Assets:
Investment in Affiliates and Other Companies	0	0
Eliminations and Other
Current Assets:
Cash and Cash Equivalents	13	8	13		12
Short-term Investments	3	7
Accounts Receivable - Net	12	13
Receivable from Affiliates	(8,501)	(8,459)
Materials and Supplies	0	0
Other Current Assets	11	21
Total Current Assets	(8,462)	(8,410)
Properties	3,024	2,989
Accumulated Depreciation	(1,766)	(1,732)
Properties - Net	1,258	1,257
Right-of-Use Lease Asset	22	18
Other Long-term Assets	(225)	(232)
Total Assets	(41,535)	(40,900)
Current Liabilities:
Accounts Payable	53	60
Labor and Fringe Benefits Payable	13	65
Payable to Affiliates	(10,161)	(10,126)
Casualty, Environmental and Other Reserves	13	13
Current Maturities of Long-term Debt	0	0
Income and Other Taxes Payable	22	15
Other Current Liabilities	17	13
Total Current Liabilities	(10,043)	(9,960)
Casualty, Environmental and Other Reserves	36	36
Long-term Debt	0	0
Deferred Income Taxes - Net	277	286
Long-term Lease Liability	16	12
Other Long-term Liabilities	(313)	(316)
Total Liabilities	(10,027)	(9,942)
Shareholders' Equity
Common Stock, $1 Par Value	(181)	(181)
Other Capital	(5,096)	(5,096)
Retained Earnings	(26,195)	(25,646)
Accumulated Other Comprehensive Loss	(36)	(35)
Noncontrolling Interest	0	0
Total Shareholders' Equity	(31,508)	(30,958)
Total Liabilities and Shareholders' Equity	(41,535)	(40,900)
Eliminations and Other | Investments in Conrail
Current Assets:
Investment in Affiliates and Other Companies	993	982
Eliminations and Other | Affiliates and Other Companies
Current Assets:
Investment in Affiliates and Other Companies	13	13
Eliminations and Other | Investments in Consolidated Subsidiaries
Current Assets:
Investment in Affiliates and Other Companies	(35,134)	(34,528)
CSX Corporation
Current Assets:
Cash and Cash Equivalents	1,891	814	1,032		716
Short-term Investments	484	989
Accounts Receivable - Net	0	4
Receivable from Affiliates	827	1,054
Materials and Supplies	0	0
Other Current Assets	0	26
Total Current Assets	3,202	2,887
Properties	1	1
Accumulated Depreciation	(1)	(1)
Properties - Net	0	0
Right-of-Use Lease Asset	0	0
Other Long-term Assets	3	3
Total Assets	38,300	37,379
Current Liabilities:
Accounts Payable	194	153
Labor and Fringe Benefits Payable	30	38
Payable to Affiliates	9,835	9,552
Casualty, Environmental and Other Reserves	0	0
Current Maturities of Long-term Debt	10	0
Income and Other Taxes Payable	(184)	(286)
Other Current Liabilities	0	0
Total Current Liabilities	9,885	9,457
Casualty, Environmental and Other Reserves	0	0
Long-term Debt	16,020	15,534
Deferred Income Taxes - Net	(145)	(152)
Long-term Lease Liability	0	0
Other Long-term Liabilities	669	692
Total Liabilities	26,429	25,531
Shareholders' Equity
Common Stock, $1 Par Value	765	773
Other Capital	366	346
Retained Earnings	11,412	11,404
Accumulated Other Comprehensive Loss	(672)	(675)
Noncontrolling Interest	0	0
Total Shareholders' Equity	11,871	11,848
Total Liabilities and Shareholders' Equity	38,300	37,379
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 | Investments in Consolidated Subsidiaries
Current Assets:
Investment in Affiliates and Other Companies	35,134	34,528
CSX Transportation
Current Assets:
Cash and Cash Equivalents	91	136	$ 143		$ 130
Short-term Investments	0	0
Accounts Receivable - Net	996	969
Receivable from Affiliates	7,674	7,405
Materials and Supplies	257	261
Other Current Assets	63	30
Total Current Assets	9,081	8,801
Properties	42,040	42,110
Accumulated Depreciation	(11,110)	(11,199)
Properties - Net	30,930	30,911
Right-of-Use Lease Asset	501	514
Other Long-term Assets	623	629
Total Assets	42,069	41,778
Current Liabilities:
Accounts Payable	811	830
Labor and Fringe Benefits Payable	302	386
Payable to Affiliates	326	574
Casualty, Environmental and Other Reserves	86	87
Current Maturities of Long-term Debt	245	245
Income and Other Taxes Payable	431	340
Other Current Liabilities	168	192
Total Current Liabilities	2,369	2,654
Casualty, Environmental and Other Reserves	174	169
Long-term Debt	457	459
Deferred Income Taxes - Net	6,859	6,827
Long-term Lease Liability	473	481
Other Long-term Liabilities	212	215
Total Liabilities	10,544	10,805
Shareholders' Equity
Common Stock, $1 Par Value	181	181
Other Capital	5,096	5,096
Retained Earnings	26,195	25,646
Accumulated Other Comprehensive Loss	36	35
Noncontrolling Interest	17	15
Total Shareholders' Equity	31,525	30,973
Total Liabilities and Shareholders' Equity	42,069	41,778
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	934	923
CSX Transportation | Investments in Consolidated Subsidiaries
Current Assets:
Investment in Affiliates and Other Companies	$ 0	$ 0

[1] Certain prior year data has been reclassified to conform to the current presentation.