Summarized Consolidating Balance Sheet (Details) (USD $) In Millions, unless otherwise specified	Sep. 28, 2012	Dec. 30, 2011	Sep. 30, 2011	Dec. 31, 2010
Current Assets
Cash and Cash Equivalents	$ 693	$ 783	$ 580	$ 1,292
Short-term Investments	35	523
Accounts Receivable - Net	1,163	1,129
Receivable from Affiliates	0	0
Materials and Supplies	264	240
Deferred Income Taxes	134	182
Other Current Assets	104	78
Total Current Assets	2,393	2,935
Properties	35,020	33,704
Accumulated Depreciation	(9,088)	(8,730)
Properties - Net	25,932	24,974
Other Long-term Assets	410	393
Total Assets	29,930	29,473
Current Liabilities
Accounts Payable	1,197	1,147
Labor and Fringe Benefits Payable	416	541
Payable to Affiliates	0	0
Casualty, Environmental and Other Reserves	169	167
Current Maturities of Long-term Debt	806	507
Income and Other Taxes Payable	261	129
Other Current Liabilities	172	196
Total Current Liabilities	3,021	2,687
Casualty, Evironmental and Other Reserves	319	352
Long-term Debt	8,257	8,734
Deferred Income Taxes	8,018	7,601
Other Long-term Liabilities	1,284	1,631
Total Liabilities	20,899	21,005
Shareholders' Equity
Common Stock, $1 Par Value	1,031	1,049
Other Capital	20	6
Retained Earnings	8,798	8,275
Accumulated Other Comprehensive Loss	(833)	(875)
Noncontrolling Interest	15	13
Total Shareholders' Equity	9,031	8,468
Total Liabilities and Shareholders' Equity	29,930	29,473
Investments in Conrail [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	693	678
Affiliates and Other Companies [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	502	493
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	458	549	367	1,100
Short-term Investments	0	475
Accounts Receivable - Net	1	4
Receivable from Affiliates	992	1,025
Materials and Supplies	0	0
Deferred Income Taxes	65	10
Other Current Assets	14	17
Total Current Assets	1,530	2,080
Properties	8	8
Accumulated Depreciation	(8)	(8)
Properties - Net	0	0
Other Long-term Assets	172	176
Total Assets	20,178	19,736
Current Liabilities
Accounts Payable	150	114
Labor and Fringe Benefits Payable	36	41
Payable to Affiliates	2,488	2,566
Casualty, Environmental and Other Reserves	0	0
Current Maturities of Long-term Debt	700	400
Income and Other Taxes Payable	(40)	(60)
Other Current Liabilities	(1)	(1)
Total Current Liabilities	3,333	3,060
Casualty, Evironmental and Other Reserves	0	0
Long-term Debt	7,208	7,609
Deferred Income Taxes	(149)	(246)
Other Long-term Liabilities	770	858
Total Liabilities	11,162	11,281
Shareholders' Equity
Common Stock, $1 Par Value	1,031	1,049
Other Capital	20	6
Retained Earnings	8,798	8,275
Accumulated Other Comprehensive Loss	(833)	(875)
Noncontrolling Interest	0	0
Total Shareholders' Equity	9,016	8,455
Total Liabilities and Shareholders' Equity	20,178	19,736
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	18,515	17,519
CSX Transportation [Member]
Current Assets
Cash and Cash Equivalents	153	154	140	118
Short-term Investments	0	0
Accounts Receivable - Net	559	468
Receivable from Affiliates	1,636	1,772
Materials and Supplies	264	240
Deferred Income Taxes	74	173
Other Current Assets	78	64
Total Current Assets	2,764	2,871
Properties	33,146	31,958
Accumulated Depreciation	(8,106)	(7,795)
Properties - Net	25,040	24,163
Other Long-term Assets	300	109
Total Assets	28,688	27,717
Current Liabilities
Accounts Payable	1,004	978
Labor and Fringe Benefits Payable	345	458
Payable to Affiliates	364	374
Casualty, Environmental and Other Reserves	153	151
Current Maturities of Long-term Debt	105	105
Income and Other Taxes Payable	308	189
Other Current Liabilities	172	194
Total Current Liabilities	2,451	2,449
Casualty, Evironmental and Other Reserves	247	284
Long-term Debt	1,049	1,124
Deferred Income Taxes	8,067	7,800
Other Long-term Liabilities	605	667
Total Liabilities	12,419	12,324
Shareholders' Equity
Common Stock, $1 Par Value	181	181
Other Capital	5,669	5,652
Retained Earnings	10,475	9,618
Accumulated Other Comprehensive Loss	(79)	(79)
Noncontrolling Interest	23	21
Total Shareholders' Equity	16,269	15,393
Total Liabilities and Shareholders' Equity	28,688	27,717
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	584	574
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	82	80	73	74
Short-term Investments	35	48
Accounts Receivable - Net	603	657
Receivable from Affiliates	(2,628)	(2,797)
Materials and Supplies	0	0
Deferred Income Taxes	(5)	(1)
Other Current Assets	12	(3)
Total Current Assets	(1,901)	(2,016)
Properties	1,866	1,738
Accumulated Depreciation	(974)	(927)
Properties - Net	892	811
Other Long-term Assets	(62)	108
Total Assets	(18,936)	(17,980)
Current Liabilities
Accounts Payable	43	55
Labor and Fringe Benefits Payable	35	42
Payable to Affiliates	(2,852)	(2,940)
Casualty, Environmental and Other Reserves	16	16
Current Maturities of Long-term Debt	1	2
Income and Other Taxes Payable	(7)	0
Other Current Liabilities	1	3
Total Current Liabilities	(2,763)	(2,822)
Casualty, Evironmental and Other Reserves	72	68
Long-term Debt	0	1
Deferred Income Taxes	100	47
Other Long-term Liabilities	(91)	106
Total Liabilities	(2,682)	(2,600)
Shareholders' Equity
Common Stock, $1 Par Value	(181)	(181)
Other Capital	(5,669)	(5,652)
Retained Earnings	(10,475)	(9,618)
Accumulated Other Comprehensive Loss	79	79
Noncontrolling Interest	(8)	(8)
Total Shareholders' Equity	(16,254)	(15,380)
Total Liabilities and Shareholders' Equity	(18,936)	(17,980)
Eliminations and Other [Member] | Investments in Conrail [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	693	678
Eliminations and Other [Member] | Affiliates and Other Companies [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	(43)	(42)
Eliminations and Other [Member] | Investments in Consolidated Subsidiaries [Member]
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	$ (18,515)	$ (17,519)