Summarized Consolidating Balance Sheet (Details) (USD $) In Millions, unless otherwise specified	Sep. 26, 2014	Dec. 27, 2013	Sep. 27, 2013	Dec. 28, 2012
Current Assets:
Cash and Cash Equivalents	$ 479	$ 592	$ 591	$ 784
Short-term Investments	575	487
Accounts Receivable - Net	1,123	1,052
Receivable from Affiliates	0	0
Materials and Supplies	276	252
Deferred Income Taxes	128	155
Other Current Assets	95	64
Total Current Assets	2,676	2,602
Properties	38,533	37,184
Accumulated Depreciation	(10,539)	(9,893)
Properties - Net	27,994	27,291
Other Long-term Assets	608	591
Total Assets	32,623	31,782
Current Liabilities:
Accounts Payable	986	957
Labor and Fringe Benefits Payable	507	587
Payable to Affiliates	0	0
Casualty, Environmental and Other Reserves	151	151
Current Maturities of Long-term Debt	230	533
Income and Other Taxes Payable	249	91
Other Current Liabilities	108	105
Total Current Liabilities	2,231	2,424
Casualty, Environmental and Other Reserves	281	300
Long-term Debt	9,387	9,022
Deferred Income Taxes	8,742	8,662
Other Long-term Liabilities	840	870
Total Liabilities	21,481	21,278
Shareholders' Equity
Common Stock $1 Par Value	995	1,009
Other Capital	80	61
Retained Earnings	10,527	9,936
Accumulated Other Comprehensive Loss	(483)	(523)
Noncontrolling Interest	23	21
Total Shareholders' Equity	11,142	10,504
Total Liabilities and Shareholders' Equity	32,623	31,782
Casualty, Environmental and Other [Member]
Current Liabilities:
Casualty, Environmental and Other Reserves	151	151
Casualty, Environmental and Other Reserves	281	300
Investments in Conrail
Current Assets:
Investment in Affiliates, Subsidiaries, and Joint Ventures	775	752
Affiliates and Other Companies
Current Assets:
Investment in Affiliates, Subsidiaries, and Joint Ventures	570	546
Investments in Consolidated Subsidiaries
Current Assets:
Investment in Affiliates, Subsidiaries, and Joint Ventures	0	0
CSX Corporation
Current Assets:
Cash and Cash Equivalents	295	439	432	481
Short-term Investments	565	472
Accounts Receivable - Net	5	3
Receivable from Affiliates	1,268	1,141
Materials and Supplies	0	0
Deferred Income Taxes	(4)	(5)
Other Current Assets	17	1
Total Current Assets	2,146	2,051
Properties	1	1
Accumulated Depreciation	(1)	(1)
Properties - Net	0	0
Other Long-term Assets	216	217
Total Assets	23,622	22,455
Current Liabilities:
Accounts Payable	144	110
Labor and Fringe Benefits Payable	35	38
Payable to Affiliates	3,287	3,298
Casualty, Environmental and Other Reserves	0	0
Current Maturities of Long-term Debt	200	200
Income and Other Taxes Payable	(273)	(397)
Other Current Liabilities	0	0
Total Current Liabilities	3,393	3,249
Casualty, Environmental and Other Reserves	0	0
Long-term Debt	8,705	8,308
Deferred Income Taxes	(62)	(64)
Other Long-term Liabilities	467	479
Total Liabilities	12,503	11,972
Shareholders' Equity
Common Stock $1 Par Value	995	1,009
Other Capital	80	61
Retained Earnings	10,527	9,936
Accumulated Other Comprehensive Loss	(483)	(523)
Noncontrolling Interest	0	0
Total Shareholders' Equity	11,119	10,483
Total Liabilities and Shareholders' Equity	23,622	22,455
CSX Corporation | Investments in Conrail
Current Assets:
Investment in Affiliates, Subsidiaries, and Joint Ventures	0	0
CSX Corporation | Affiliates and Other Companies
Current Assets:
Investment in Affiliates, Subsidiaries, and Joint Ventures	(39)	(39)
CSX Corporation | Investments in Consolidated Subsidiaries
Current Assets:
Investment in Affiliates, Subsidiaries, and Joint Ventures	21,299	20,226
CSX Transportation
Current Assets:
Cash and Cash Equivalents	128	91	101	235
Short-term Investments	0	0
Accounts Receivable - Net	189	240
Receivable from Affiliates	2,618	2,635
Materials and Supplies	276	252
Deferred Income Taxes	132	161
Other Current Assets	65	57
Total Current Assets	3,408	3,436
Properties	36,177	34,987
Accumulated Depreciation	(9,330)	(8,778)
Properties - Net	26,847	26,209
Other Long-term Assets	389	388
Total Assets	31,280	30,645
Current Liabilities:
Accounts Payable	811	809
Labor and Fringe Benefits Payable	427	491
Payable to Affiliates	503	535
Casualty, Environmental and Other Reserves	136	136
Current Maturities of Long-term Debt	30	333
Income and Other Taxes Payable	510	479
Other Current Liabilities	103	103
Total Current Liabilities	2,520	2,886
Casualty, Environmental and Other Reserves	216	231
Long-term Debt	682	714
Deferred Income Taxes	8,615	8,548
Other Long-term Liabilities	497	512
Total Liabilities	12,530	12,891
Shareholders' Equity
Common Stock $1 Par Value	181	181
Other Capital	5,077	5,077
Retained Earnings	13,500	12,514
Accumulated Other Comprehensive Loss	(35)	(43)
Noncontrolling Interest	27	25
Total Shareholders' Equity	18,750	17,754
Total Liabilities and Shareholders' Equity	31,280	30,645
CSX Transportation | Investments in Conrail
Current Assets:
Investment in Affiliates, Subsidiaries, and Joint Ventures	0	0
CSX Transportation | Affiliates and Other Companies
Current Assets:
Investment in Affiliates, Subsidiaries, and Joint Ventures	636	612
CSX Transportation | Investments in Consolidated Subsidiaries
Current Assets:
Investment in Affiliates, Subsidiaries, and Joint Ventures	0	0
Eliminations and Other
Current Assets:
Cash and Cash Equivalents	56	62	58	68
Short-term Investments	10	15
Accounts Receivable - Net	929	809
Receivable from Affiliates	(3,886)	(3,776)
Materials and Supplies	0	0
Deferred Income Taxes	0	(1)
Other Current Assets	13	6
Total Current Assets	(2,878)	(2,885)
Properties	2,355	2,196
Accumulated Depreciation	(1,208)	(1,114)
Properties - Net	1,147	1,082
Other Long-term Assets	3	(14)
Total Assets	(22,279)	(21,318)
Current Liabilities:
Accounts Payable	31	38
Labor and Fringe Benefits Payable	45	58
Payable to Affiliates	(3,790)	(3,833)
Casualty, Environmental and Other Reserves	15	15
Current Maturities of Long-term Debt	0	0
Income and Other Taxes Payable	12	9
Other Current Liabilities	5	2
Total Current Liabilities	(3,682)	(3,711)
Casualty, Environmental and Other Reserves	65	69
Long-term Debt	0	0
Deferred Income Taxes	189	178
Other Long-term Liabilities	(124)	(121)
Total Liabilities	(3,552)	(3,585)
Shareholders' Equity
Common Stock $1 Par Value	(181)	(181)
Other Capital	(5,077)	(5,077)
Retained Earnings	(13,500)	(12,514)
Accumulated Other Comprehensive Loss	35	43
Noncontrolling Interest	(4)	(4)
Total Shareholders' Equity	(18,727)	(17,733)
Total Liabilities and Shareholders' Equity	(22,279)	(21,318)
Eliminations and Other | Investments in Conrail
Current Assets:
Investment in Affiliates, Subsidiaries, and Joint Ventures	775	752
Eliminations and Other | Affiliates and Other Companies
Current Assets:
Investment in Affiliates, Subsidiaries, and Joint Ventures	(27)	(27)
Eliminations and Other | Investments in Consolidated Subsidiaries
Current Assets:
Investment in Affiliates, Subsidiaries, and Joint Ventures	$ (21,299)	$ (20,226)