Summarized Consolidating Financial Data - Consolidating Cash Flow Statements (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Operating Activities
Net Cash Provided by (Used in) Operating Activities			$ 3,737	$ 3,406
Investing Activities
Property Additions			(1,191)	(1,240)
Proceeds from Property Dispositions			218	257
Purchases of Short-term Investments			(2,255)	(611)
Proceeds from Sales of Short-term Investments			1,480	15
Other Investing Activities			19	(8)
Net Cash Used In Investing Activities			(1,729)	(1,587)
Financing Activities
Long-term Debt Issued			2,000	2,000
Long-term Debt Repaid			(18)	(19)
Dividends Paid			(577)	(570)
Shares Repurchased	$ (1,111)	$ (1,006)	(2,767)	(2,816)
Accelerated Share Repurchase Pending Final Settlement			0	(100)
Other Financing Activities			17	(52)
Net Cash (Used in) Provided by Financing Activities			(1,345)	(1,557)
Net Increase (Decrease) in Cash and Cash Equivalents			663	262
Cash and Cash Equivalents at Beginning of Period			858	401
Cash and Cash Equivalents at End of Period	1,521	663	1,521	663
Eliminations and Other
Operating Activities
Net Cash Provided by (Used in) Operating Activities			(624)	(803)
Investing Activities
Property Additions			(106)	(106)
Proceeds from Property Dispositions			0	0
Purchases of Short-term Investments			0	(2)
Proceeds from Sales of Short-term Investments			0	15
Other Investing Activities			(18)	142
Net Cash Used In Investing Activities			(124)	49
Financing Activities
Long-term Debt Issued			0	0
Long-term Debt Repaid			0	0
Dividends Paid			750	750
Shares Repurchased			0	0
Accelerated Share Repurchase Pending Final Settlement				0
Other Financing Activities			0	8
Net Cash (Used in) Provided by Financing Activities			750	758
Net Increase (Decrease) in Cash and Cash Equivalents			2	4
Cash and Cash Equivalents at Beginning of Period			12	6
Cash and Cash Equivalents at End of Period	14	10	14	10
CSX Corporation
Operating Activities
Net Cash Provided by (Used in) Operating Activities			2,732	2,417
Investing Activities
Property Additions			0	0
Proceeds from Property Dispositions			0	0
Purchases of Short-term Investments			(2,255)	(609)
Proceeds from Sales of Short-term Investments			1,480	0
Other Investing Activities			4	(1)
Net Cash Used In Investing Activities			(771)	(610)
Financing Activities
Long-term Debt Issued			2,000	2,000
Long-term Debt Repaid			0	0
Dividends Paid			(577)	(570)
Shares Repurchased			(2,767)	(2,816)
Accelerated Share Repurchase Pending Final Settlement				(100)
Other Financing Activities			22	(58)
Net Cash (Used in) Provided by Financing Activities			(1,322)	(1,544)
Net Increase (Decrease) in Cash and Cash Equivalents			639	263
Cash and Cash Equivalents at Beginning of Period			716	274
Cash and Cash Equivalents at End of Period	1,355	537	1,355	537
CSX Transportation
Operating Activities
Net Cash Provided by (Used in) Operating Activities			1,629	1,792
Investing Activities
Property Additions			(1,085)	(1,134)
Proceeds from Property Dispositions			218	257
Purchases of Short-term Investments			0	0
Proceeds from Sales of Short-term Investments			0	0
Other Investing Activities			33	(149)
Net Cash Used In Investing Activities			(834)	(1,026)
Financing Activities
Long-term Debt Issued			0	0
Long-term Debt Repaid			(18)	(19)
Dividends Paid			(750)	(750)
Shares Repurchased			0	0
Accelerated Share Repurchase Pending Final Settlement				0
Other Financing Activities			(5)	(2)
Net Cash (Used in) Provided by Financing Activities			(773)	(771)
Net Increase (Decrease) in Cash and Cash Equivalents			22	(5)
Cash and Cash Equivalents at Beginning of Period			130	121
Cash and Cash Equivalents at End of Period	$ 152	$ 116	$ 152	$ 116