Summarized Consolidating Balance Sheet (Details) (USD $) In Millions, unless otherwise specified	Mar. 29, 2013	Dec. 28, 2012	Mar. 30, 2012	Dec. 30, 2011
Current Assets
Cash and Cash Equivalents	$ 705	$ 784	$ 627	$ 783
Short-term Investments	367	587
Accounts Receivable - Net	976	962
Receivable from Affiliates	0	0
Materials and Supplies	283	274
Deferred Income Taxes	133	119
Other Current Assets	103	75
Total Current Assets	2,567	2,801
Properties	35,674	35,279
Accumulated Depreciation	(9,386)	(9,229)
Properties - Net	26,288	26,050
Other Long-term Assets	516	514
Total Assets	30,586	30,571
Current Liabilities
Accounts Payable	1,043	1,014
Labor and Fringe Benefits Payable	376	468
Payable to Affiliates	0	0
Casualty, Environmental and Other Reserves	139	140
Current Maturities of Long-term Debt	572	780
Income and Other Taxes Payable	206	85
Other Current Liabilities	138	140
Total Current Liabilities	2,474	2,627
Casualty, Evironmental and Other Reserves	323	337
Long-term Debt	8,846	9,052
Deferred Income Taxes	8,202	8,096
Other Long-term Liabilities	1,393	1,457
Total Liabilities	21,238	21,569
Shareholders' Equity
Common Stock $1 Par Value	1,022	1,020
Other Capital	36	28
Retained Earnings	9,191	8,876
Accumulated Other Comprehensive Loss	(919)	(936)
Noncontrolling Interest	18	14
Total Shareholders' Equity	9,348	9,002
Total Liabilities and Shareholders' Equity	30,586	30,571
Investments in Conrail [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	703	695
Affiliates and Other Companies [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	512	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	445	481	385	549
Short-term Investments	330	555
Accounts Receivable - Net	0	3
Receivable from Affiliates	1,113	993
Materials and Supplies	0	0
Deferred Income Taxes	57	52
Other Current Assets	12	11
Total Current Assets	1,957	2,095
Properties	8	8
Accumulated Depreciation	(8)	(8)
Properties - Net	0	0
Other Long-term Assets	185	186
Total Assets	21,196	21,025
Current Liabilities
Accounts Payable	163	133
Labor and Fringe Benefits Payable	33	35
Payable to Affiliates	2,801	2,679
Casualty, Environmental and Other Reserves	0	0
Current Maturities of Long-term Debt	500	700
Income and Other Taxes Payable	(181)	(262)
Other Current Liabilities	0	(1)
Total Current Liabilities	3,316	3,284
Casualty, Evironmental and Other Reserves	0	0
Long-term Debt	7,806	8,005
Deferred Income Taxes	(154)	(153)
Other Long-term Liabilities	898	901
Total Liabilities	11,866	12,037
Shareholders' Equity
Common Stock $1 Par Value	1,022	1,020
Other Capital	36	28
Retained Earnings	9,191	8,876
Accumulated Other Comprehensive Loss	(919)	(936)
Noncontrolling Interest	0	0
Total Shareholders' Equity	9,330	8,988
Total Liabilities and Shareholders' Equity	21,196	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	19,093	18,783
CSX Transportation [Member]
Current Assets
Cash and Cash Equivalents	208	235	159	154
Short-term Investments	0	0
Accounts Receivable - Net	383	427
Receivable from Affiliates	1,939	1,798
Materials and Supplies	283	274
Deferred Income Taxes	71	62
Other Current Assets	89	64
Total Current Assets	2,973	2,860
Properties	33,690	33,333
Accumulated Depreciation	(8,353)	(8,225)
Properties - Net	25,337	25,108
Other Long-term Assets	367	368
Total Assets	29,271	28,929
Current Liabilities
Accounts Payable	855	846
Labor and Fringe Benefits Payable	315	391
Payable to Affiliates	473	411
Casualty, Environmental and Other Reserves	123	124
Current Maturities of Long-term Debt	72	80
Income and Other Taxes Payable	377	334
Other Current Liabilities	135	139
Total Current Liabilities	2,350	2,325
Casualty, Evironmental and Other Reserves	250	256
Long-term Debt	1,040	1,047
Deferred Income Taxes	8,224	8,131
Other Long-term Liabilities	625	656
Total Liabilities	12,489	12,415
Shareholders' Equity
Common Stock $1 Par Value	181	181
Other Capital	5,074	5,672
Retained Earnings	11,607	10,740
Accumulated Other Comprehensive Loss	(102)	(102)
Noncontrolling Interest	22	23
Total Shareholders' Equity	16,782	16,514
Total Liabilities and Shareholders' Equity	29,271	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	594	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	52	68	83	80
Short-term Investments	37	32
Accounts Receivable - Net	593	532
Receivable from Affiliates	(3,052)	(2,791)
Materials and Supplies	0	0
Deferred Income Taxes	5	5
Other Current Assets	2	0
Total Current Assets	(2,363)	(2,154)
Properties	1,976	1,938
Accumulated Depreciation	(1,025)	(996)
Properties - Net	951	942
Other Long-term Assets	(36)	(40)
Total Assets	(19,881)	(19,383)
Current Liabilities
Accounts Payable	25	35
Labor and Fringe Benefits Payable	28	42
Payable to Affiliates	(3,274)	(3,090)
Casualty, Environmental and Other Reserves	16	16
Current Maturities of Long-term Debt	0	0
Income and Other Taxes Payable	10	13
Other Current Liabilities	3	2
Total Current Liabilities	(3,192)	(2,982)
Casualty, Evironmental and Other Reserves	73	81
Long-term Debt	0	0
Deferred Income Taxes	132	118
Other Long-term Liabilities	(130)	(100)
Total Liabilities	(3,117)	(2,883)
Shareholders' Equity
Common Stock $1 Par Value	(181)	(181)
Other Capital	(5,074)	(5,672)
Retained Earnings	(11,607)	(10,740)
Accumulated Other Comprehensive Loss	102	102
Noncontrolling Interest	(4)	(9)
Total Shareholders' Equity	(16,764)	(16,500)
Total Liabilities and Shareholders' Equity	(19,881)	(19,383)
Eliminations and Other [Member] | Investments in Conrail [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	703	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	$ (19,093)	$ (18,783)