Summarized Consolidating Balance Sheet (Details) (USD $) In Millions, unless otherwise specified	Jun. 28, 2013	Dec. 28, 2012	Jun. 29, 2012	Dec. 30, 2011
Current Assets
Cash and Cash Equivalents	$ 614	$ 784	$ 642	$ 783
Short-term Investments	403	587
Accounts Receivable - Net	946	962
Receivable from Affiliates	0	0
Materials and Supplies	264	274
Deferred Income Taxes	144	119
Other Current Assets	118	75
Total Current Assets	2,489	2,801
Properties	36,149	35,279
Accumulated Depreciation	(9,550)	(9,229)
Properties - Net	26,599	26,050
Other Long-term Assets	565	514
Total Assets	30,881	30,571
Current Liabilities
Accounts Payable	1,022	1,014
Labor and Fringe Benefits Payable	452	468
Payable to Affiliates	0	0
Casualty, Environmental and Other Reserves	150	140
Current Maturities of Long-term Debt	564	780
Income and Other Taxes Payable	111	85
Other Current Liabilities	119	140
Total Current Liabilities	2,418	2,627
Casualty, Evironmental and Other Reserves	299	337
Long-term Debt	8,811	9,052
Deferred Income Taxes	8,313	8,096
Other Long-term Liabilities	1,378	1,457
Total Liabilities	21,219	21,569
Shareholders' Equity
Common Stock $1 Par Value	1,019	1,020
Other Capital	44	28
Retained Earnings	9,482	8,876
Accumulated Other Comprehensive Loss	(902)	(936)
Noncontrolling Interest	19	14
Total Shareholders' Equity	9,662	9,002
Total Liabilities and Shareholders' Equity	30,881	30,571
Investments in Conrail [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	709	695
Affiliates and Other Companies [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	519	511
Investments in Consolidated Subsidiaries [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	0	0
CSX Corporation [Member]
Current Assets
Cash and Cash Equivalents	441	481	405	549
Short-term Investments	400	555
Accounts Receivable - Net	3	3
Receivable from Affiliates	1,060	993
Materials and Supplies	0	0
Deferred Income Taxes	64	52
Other Current Assets	12	11
Total Current Assets	1,980	2,095
Properties	8	8
Accumulated Depreciation	(8)	(8)
Properties - Net	0	0
Other Long-term Assets	182	186
Total Assets	21,578	21,025
Current Liabilities
Accounts Payable	123	133
Labor and Fringe Benefits Payable	34	35
Payable to Affiliates	3,075	2,679
Casualty, Environmental and Other Reserves	0	0
Current Maturities of Long-term Debt	500	700
Income and Other Taxes Payable	(350)	(262)
Other Current Liabilities	0	(1)
Total Current Liabilities	3,382	3,284
Casualty, Evironmental and Other Reserves	0	0
Long-term Debt	7,806	8,005
Deferred Income Taxes	(146)	(153)
Other Long-term Liabilities	893	901
Total Liabilities	11,935	12,037
Shareholders' Equity
Common Stock $1 Par Value	1,019	1,020
Other Capital	44	28
Retained Earnings	9,482	8,876
Accumulated Other Comprehensive Loss	(902)	(936)
Noncontrolling Interest	0	0
Total Shareholders' Equity	9,643	8,988
Total Liabilities and Shareholders' Equity	21,578	21,025
CSX Corporation [Member] | Investments in Conrail [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	0	0
CSX Corporation [Member] | Affiliates and Other Companies [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	(39)	(39)
CSX Corporation [Member] | Investments in Consolidated Subsidiaries [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	19,455	18,783
CSX Transportation [Member]
Current Assets
Cash and Cash Equivalents	115	235	160	154
Short-term Investments	0	0
Accounts Receivable - Net	371	427
Receivable from Affiliates	2,219	1,798
Materials and Supplies	264	274
Deferred Income Taxes	79	62
Other Current Assets	96	64
Total Current Assets	3,144	2,860
Properties	34,109	33,333
Accumulated Depreciation	(8,489)	(8,225)
Properties - Net	25,620	25,108
Other Long-term Assets	385	368
Total Assets	29,750	28,929
Current Liabilities
Accounts Payable	871	846
Labor and Fringe Benefits Payable	395	391
Payable to Affiliates	429	411
Casualty, Environmental and Other Reserves	134	124
Current Maturities of Long-term Debt	64	80
Income and Other Taxes Payable	450	334
Other Current Liabilities	117	139
Total Current Liabilities	2,460	2,325
Casualty, Evironmental and Other Reserves	231	256
Long-term Debt	1,005	1,047
Deferred Income Taxes	8,320	8,131
Other Long-term Liabilities	612	656
Total Liabilities	12,628	12,415
Shareholders' Equity
Common Stock $1 Par Value	181	181
Other Capital	5,077	5,672
Retained Earnings	11,941	10,740
Accumulated Other Comprehensive Loss	(100)	(102)
Noncontrolling Interest	23	23
Total Shareholders' Equity	17,122	16,514
Total Liabilities and Shareholders' Equity	29,750	28,929
CSX Transportation [Member] | Investments in Conrail [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	0	0
CSX Transportation [Member] | Affiliates and Other Companies [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	601	593
CSX Transportation [Member] | Investments in Consolidated Subsidiaries [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	0	0
Eliminations and Other [Member]
Current Assets
Cash and Cash Equivalents	58	68	77	80
Short-term Investments	3	32
Accounts Receivable - Net	572	532
Receivable from Affiliates	(3,279)	(2,791)
Materials and Supplies	0	0
Deferred Income Taxes	1	5
Other Current Assets	10	0
Total Current Assets	(2,635)	(2,154)
Properties	2,032	1,938
Accumulated Depreciation	(1,053)	(996)
Properties - Net	979	942
Other Long-term Assets	(2)	(40)
Total Assets	(20,447)	(19,383)
Current Liabilities
Accounts Payable	28	35
Labor and Fringe Benefits Payable	23	42
Payable to Affiliates	(3,504)	(3,090)
Casualty, Environmental and Other Reserves	16	16
Current Maturities of Long-term Debt	0	0
Income and Other Taxes Payable	11	13
Other Current Liabilities	2	2
Total Current Liabilities	(3,424)	(2,982)
Casualty, Evironmental and Other Reserves	68	81
Long-term Debt	0	0
Deferred Income Taxes	139	118
Other Long-term Liabilities	(127)	(100)
Total Liabilities	(3,344)	(2,883)
Shareholders' Equity
Common Stock $1 Par Value	(181)	(181)
Other Capital	(5,077)	(5,672)
Retained Earnings	(11,941)	(10,740)
Accumulated Other Comprehensive Loss	100	102
Noncontrolling Interest	(4)	(9)
Total Shareholders' Equity	(17,103)	(16,500)
Total Liabilities and Shareholders' Equity	(20,447)	(19,383)
Eliminations and Other [Member] | Investments in Conrail [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	709	695
Eliminations and Other [Member] | Affiliates and Other Companies [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	(43)	(43)
Eliminations and Other [Member] | Investments in Consolidated Subsidiaries [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	$ (19,455)	$ (18,783)