Summarized Consolidating Financial Data - Consolidating Cash Flow Statements (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating Activities
Net Cash Provided by (Used in) Operating Activities	$ 1,178	$ 1,173	[1]
Investing Activities
Property Additions	(381)	(353)	[1]
Proceeds from Property Dispositions	35	48	[1]
Purchases of Short-term Investments	(426)	(813)	[1]
Proceeds from Sales of Short-term Investments	936	250	[1]
Other Investing Activities	(20)	(2)	[1]
Net Cash Provided by (Used In) Investing Activities	144	(870)	[1]
Financing Activities
Long-term Debt Issued	500	1,000	[1]
Dividends Paid	(201)	(195)	[1]
Shares Repurchased	(577)	(796)	[1]
Other Financing Activities	(7)	18	[1]
Net Cash (Used in) Provided by Financing Activities	(285)	27	[1]
Net Increase in Cash and Cash Equivalents	1,037	330	[1]
Cash and Cash Equivalents at Beginning of Period	958	858	[1]
Cash and Cash Equivalents at End of Period	1,995	1,188	[1]
Eliminations and Other
Operating Activities
Net Cash Provided by (Used in) Operating Activities	(191)	(212)
Investing Activities
Property Additions	(40)	(34)
Proceeds from Property Dispositions	0	(3)
Purchases of Short-term Investments	(2)	0
Proceeds from Sales of Short-term Investments	6	0
Other Investing Activities	(18)	0
Net Cash Provided by (Used In) Investing Activities	(54)	(37)
Financing Activities
Long-term Debt Issued	0	0
Dividends Paid	250	250
Shares Repurchased	0	0
Other Financing Activities	0	0
Net Cash (Used in) Provided by Financing Activities	250	250
Net Increase in Cash and Cash Equivalents	5	1
Cash and Cash Equivalents at Beginning of Period	8	12
Cash and Cash Equivalents at End of Period	13	13
CSX Corporation
Operating Activities
Net Cash Provided by (Used in) Operating Activities	855	852
Investing Activities
Property Additions	0	0
Proceeds from Property Dispositions	0	0
Purchases of Short-term Investments	(424)	(813)
Proceeds from Sales of Short-term Investments	930	250
Other Investing Activities	1	(1)
Net Cash Provided by (Used In) Investing Activities	507	(564)
Financing Activities
Long-term Debt Issued	500	1,000
Dividends Paid	(201)	(195)
Shares Repurchased	(577)	(796)
Other Financing Activities	(7)	19
Net Cash (Used in) Provided by Financing Activities	(285)	28
Net Increase in Cash and Cash Equivalents	1,077	316
Cash and Cash Equivalents at Beginning of Period	814	716
Cash and Cash Equivalents at End of Period	1,891	1,032
CSX Transportation
Operating Activities
Net Cash Provided by (Used in) Operating Activities	514	533
Investing Activities
Property Additions	(341)	(319)
Proceeds from Property Dispositions	35	51
Purchases of Short-term Investments	0	0
Proceeds from Sales of Short-term Investments	0	0
Other Investing Activities	(3)	(1)
Net Cash Provided by (Used In) Investing Activities	(309)	(269)
Financing Activities
Long-term Debt Issued	0	0
Dividends Paid	(250)	(250)
Shares Repurchased	0	0
Other Financing Activities	0	(1)
Net Cash (Used in) Provided by Financing Activities	(250)	(251)
Net Increase in Cash and Cash Equivalents	(45)	13
Cash and Cash Equivalents at Beginning of Period	136	130
Cash and Cash Equivalents at End of Period	$ 91	$ 143

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