Summarized Consolidating Balance Sheet (Details) (USD $) In Millions, unless otherwise specified	Sep. 27, 2013	Dec. 28, 2012	Sep. 28, 2012	Dec. 30, 2011
Current Assets
Cash and Cash Equivalents	$ 591	$ 784	$ 693	$ 783
Short-term Investments	128	587
Accounts Receivable - Net	981	962
Receivable from Affiliates	0	0
Materials and Supplies	267	274
Deferred Income Taxes	148	119
Other Current Assets	85	75
Total Current Assets	2,200	2,801
Properties	36,637	35,279
Accumulated Depreciation	(9,691)	(9,229)
Properties - Net	26,946	26,050
Other Long-term Assets	556	514
Total Assets	30,943	30,571
Current Liabilities
Accounts Payable	1,078	1,014
Labor and Fringe Benefits Payable	511	468
Payable to Affiliates	0	0
Current Maturities of Long-term Debt	264	780
Income and Other Taxes Payable	138	85
Other Current Liabilities	111	140
Total Current Liabilities	2,251	2,627
Long-term Debt	8,787	9,052
Deferred Income Taxes	8,387	8,096
Other Long-term Liabilities	1,366	1,457
Total Liabilities	21,075	21,569
Shareholders' Equity
Common Stock $1 Par Value	1,014	1,020
Other Capital	50	28
Retained Earnings	9,670	8,876
Accumulated Other Comprehensive Loss	(886)	(936)
Noncontrolling Interest	20	14
Total Shareholders' Equity	9,868	9,002
Total Liabilities and Shareholders' Equity	30,943	30,571
Casualty, Environmental and Other [Member]
Current Liabilities
Loss Contingency, Accrual, Current (Note 4)	149	140
Loss Contingency, Accrual, Noncurrent (Note 4)	284	337
Investments in Conrail [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	715	695
Affiliates and Other Companies [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	526	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	432	481	458	549
Short-term Investments	120	555
Accounts Receivable - Net	2	3
Receivable from Affiliates	1,179	993
Materials and Supplies	0	0
Deferred Income Taxes	(3)	52
Other Current Assets	11	11
Total Current Assets	1,741	2,095
Properties	3	8
Accumulated Depreciation	(3)	(8)
Properties - Net	0	0
Other Long-term Assets	180	186
Total Assets	21,648	21,025
Current Liabilities
Accounts Payable	143	133
Labor and Fringe Benefits Payable	36	35
Payable to Affiliates	3,309	2,679
Current Maturities of Long-term Debt	200	700
Income and Other Taxes Payable	(379)	(262)
Other Current Liabilities	0	(1)
Total Current Liabilities	3,309	3,284
Long-term Debt	7,808	8,005
Deferred Income Taxes	(204)	(153)
Other Long-term Liabilities	887	901
Total Liabilities	11,800	12,037
Shareholders' Equity
Common Stock $1 Par Value	1,014	1,020
Other Capital	50	28
Retained Earnings	9,670	8,876
Accumulated Other Comprehensive Loss	(886)	(936)
Noncontrolling Interest	0	0
Total Shareholders' Equity	9,848	8,988
Total Liabilities and Shareholders' Equity	21,648	21,025
CSX Corporation [Member] | Casualty, Environmental and Other [Member]
Current Liabilities
Loss Contingency, Accrual, Current (Note 4)	0	0
Loss Contingency, Accrual, Noncurrent (Note 4)	0	0
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	19,766	18,783
CSX Transportation [Member]
Current Assets
Cash and Cash Equivalents	101	235	153	154
Short-term Investments	0	0
Accounts Receivable - Net	363	427
Receivable from Affiliates	2,389	1,798
Materials and Supplies	267	274
Deferred Income Taxes	152	62
Other Current Assets	61	64
Total Current Assets	3,333	2,860
Properties	34,535	33,333
Accumulated Depreciation	(8,606)	(8,225)
Properties - Net	25,929	25,108
Other Long-term Assets	384	368
Total Assets	30,253	28,929
Current Liabilities
Accounts Payable	898	846
Labor and Fringe Benefits Payable	429	391
Payable to Affiliates	481	411
Current Maturities of Long-term Debt	64	80
Income and Other Taxes Payable	490	334
Other Current Liabilities	109	139
Total Current Liabilities	2,605	2,325
Long-term Debt	979	1,047
Deferred Income Taxes	8,448	8,131
Other Long-term Liabilities	603	656
Total Liabilities	12,852	12,415
Shareholders' Equity
Common Stock $1 Par Value	181	181
Other Capital	5,077	5,672
Retained Earnings	12,217	10,740
Accumulated Other Comprehensive Loss	(98)	(102)
Noncontrolling Interest	24	23
Total Shareholders' Equity	17,401	16,514
Total Liabilities and Shareholders' Equity	30,253	28,929
CSX Transportation [Member] | Casualty, Environmental and Other [Member]
Current Liabilities
Loss Contingency, Accrual, Current (Note 4)	134	124
Loss Contingency, Accrual, Noncurrent (Note 4)	217	256
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	607	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	82	80
Short-term Investments	8	32
Accounts Receivable - Net	616	532
Receivable from Affiliates	(3,568)	(2,791)
Materials and Supplies	0	0
Deferred Income Taxes	(1)	5
Other Current Assets	13	0
Total Current Assets	(2,874)	(2,154)
Properties	2,099	1,938
Accumulated Depreciation	(1,082)	(996)
Properties - Net	1,017	942
Other Long-term Assets	(8)	(40)
Total Assets	(20,958)	(19,383)
Current Liabilities
Accounts Payable	37	35
Labor and Fringe Benefits Payable	46	42
Payable to Affiliates	(3,790)	(3,090)
Current Maturities of Long-term Debt	0	0
Income and Other Taxes Payable	27	13
Other Current Liabilities	2	2
Total Current Liabilities	(3,663)	(2,982)
Long-term Debt	0	0
Deferred Income Taxes	143	118
Other Long-term Liabilities	(124)	(100)
Total Liabilities	(3,577)	(2,883)
Shareholders' Equity
Common Stock $1 Par Value	(181)	(181)
Other Capital	(5,077)	(5,672)
Retained Earnings	(12,217)	(10,740)
Accumulated Other Comprehensive Loss	98	102
Noncontrolling Interest	(4)	(9)
Total Shareholders' Equity	(17,381)	(16,500)
Total Liabilities and Shareholders' Equity	(20,958)	(19,383)
Eliminations and Other [Member] | Casualty, Environmental and Other [Member]
Current Liabilities
Loss Contingency, Accrual, Current (Note 4)	15	16
Loss Contingency, Accrual, Noncurrent (Note 4)	67	81
Eliminations and Other [Member] | Investments in Conrail [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	715	695
Eliminations and Other [Member] | Affiliates and Other Companies [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	(42)	(43)
Eliminations and Other [Member] | Investments in Consolidated Subsidiaries [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	$ (19,766)	$ (18,783)