Summarized Consolidating Financial Data (Balance Sheets) (Details) (USD $) In Millions, unless otherwise specified	Dec. 28, 2012	Dec. 30, 2011	Dec. 31, 2010	Dec. 25, 2009
Current Assets
Cash and Cash Equivalents	$ 784	$ 783	$ 1,292	$ 1,029
Short-term Investments	587	523
Accounts Receivable - Net	962	1,000
Receivable from Affiliates	0	0
Materials and Supplies	274	240
Deferred Income Taxes	119	182
Other Current Assets	75	78
Total Current Assets	2,801	2,806
Properties	35,279	33,704
Accumulated Depreciation	(9,229)	(8,730)
Properties - Net (Note 6)	26,050	24,974
Other Long-term Assets	514	393
Total Assets	30,571	29,344
Current Liabilities
Accounts Payable	1,014	1,018
Labor and Fringe Benefits Payable	468	541
Payable to Affiliates	0	0
Casualty, Environmental and Other Reserves	140	167
Current Maturities of Long-term Debt (Note 9)	780	507
Income and Other Taxes Payable	85	129
Other Current Liabilities	140	196
Total Current Liabilities	2,627	2,558
Casualty, Evironmental and Other Reserves	337	352
Long-term Debt	9,052	8,734
Deferred Income Taxes	8,096	7,601
Other Long-term Liabilities	1,457	1,631
Total Liabilities	21,569	20,876
Shareholders' Equity
Common Stock, $1 Par Value	1,020	1,049
Other Capital	28	6
Retained Earnings	8,876	8,275
Accumulated Other Comprehensive Loss	(936)	(875)	(771)	(809)
Noncontrolling Minority Interest	14	13
Total Shareholders' Equity	9,002	8,468	8,700	8,768
Total Liabilities and Shareholders' Equity	30,571	29,344
Investments in Conrail
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	695	678
Affiliates and Other Companies
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	511	493
Investments in Consolidated Subsidiaries
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	0	0
CSX Corporation
Current Assets
Cash and Cash Equivalents	481	549	1,100	918
Short-term Investments	555	475
Accounts Receivable - Net	3	4
Receivable from Affiliates	993	1,025
Materials and Supplies	0	0
Deferred Income Taxes	52	10
Other Current Assets	11	17
Total Current Assets	2,095	2,080
Properties	8	8
Accumulated Depreciation	(8)	(8)
Properties - Net (Note 6)	0	0
Other Long-term Assets	186	176
Total Assets	21,025	19,736
Current Liabilities
Accounts Payable	133	114
Labor and Fringe Benefits Payable	35	41
Payable to Affiliates	2,679	2,566
Casualty, Environmental and Other Reserves	0	0
Current Maturities of Long-term Debt (Note 9)	700	400
Income and Other Taxes Payable	(262)	(60)
Other Current Liabilities	(1)	(1)
Total Current Liabilities	3,284	3,060
Casualty, Evironmental and Other Reserves	0	0
Long-term Debt	8,005	7,609
Deferred Income Taxes	(153)	(246)
Other Long-term Liabilities	901	858
Total Liabilities	12,037	11,281
Shareholders' Equity
Common Stock, $1 Par Value	1,020	1,049
Other Capital	28	6
Retained Earnings	8,876	8,275
Accumulated Other Comprehensive Loss	(936)	(875)
Noncontrolling Minority Interest	0	0
Total Shareholders' Equity	8,988	8,455
Total Liabilities and Shareholders' Equity	21,025	19,736
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	18,783	17,519
CSX Transportation
Current Assets
Cash and Cash Equivalents	235	154	118	30
Short-term Investments	0	0
Accounts Receivable - Net	427	339
Receivable from Affiliates	1,798	1,772
Materials and Supplies	274	240
Deferred Income Taxes	62	173
Other Current Assets	64	64
Total Current Assets	2,860	2,742
Properties	33,333	31,958
Accumulated Depreciation	(8,225)	(7,795)
Properties - Net (Note 6)	25,108	24,163
Other Long-term Assets	368	109
Total Assets	28,929	27,588
Current Liabilities
Accounts Payable	846	849
Labor and Fringe Benefits Payable	391	458
Payable to Affiliates	411	374
Casualty, Environmental and Other Reserves	124	151
Current Maturities of Long-term Debt (Note 9)	80	105
Income and Other Taxes Payable	334	189
Other Current Liabilities	139	194
Total Current Liabilities	2,325	2,320
Casualty, Evironmental and Other Reserves	256	284
Long-term Debt	1,047	1,124
Deferred Income Taxes	8,131	7,800
Other Long-term Liabilities	656	667
Total Liabilities	12,415	12,195
Shareholders' Equity
Common Stock, $1 Par Value	181	181
Other Capital	5,672	5,652
Retained Earnings	10,740	9,618
Accumulated Other Comprehensive Loss	(102)	(79)
Noncontrolling Minority Interest	23	21
Total Shareholders' Equity	16,514	15,393
Total Liabilities and Shareholders' Equity	28,929	27,588
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	593	574
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	68	80	74	81
Short-term Investments	32	48
Accounts Receivable - Net	532	657
Receivable from Affiliates	(2,791)	(2,797)
Materials and Supplies	0	0
Deferred Income Taxes	5	(1)
Other Current Assets	0	(3)
Total Current Assets	(2,154)	(2,016)
Properties	1,938	1,738
Accumulated Depreciation	(996)	(927)
Properties - Net (Note 6)	942	811
Other Long-term Assets	(40)	108
Total Assets	(19,383)	(17,980)
Current Liabilities
Accounts Payable	35	55
Labor and Fringe Benefits Payable	42	42
Payable to Affiliates	(3,090)	(2,940)
Casualty, Environmental and Other Reserves	16	16
Current Maturities of Long-term Debt (Note 9)	0	2
Income and Other Taxes Payable	13	0
Other Current Liabilities	2	3
Total Current Liabilities	(2,982)	(2,822)
Casualty, Evironmental and Other Reserves	81	68
Long-term Debt	0	1
Deferred Income Taxes	118	47
Other Long-term Liabilities	(100)	106
Total Liabilities	(2,883)	(2,600)
Shareholders' Equity
Common Stock, $1 Par Value	(181)	(181)
Other Capital	(5,672)	(5,652)
Retained Earnings	(10,740)	(9,618)
Accumulated Other Comprehensive Loss	102	79
Noncontrolling Minority Interest	(9)	(8)
Total Shareholders' Equity	(16,500)	(15,380)
Total Liabilities and Shareholders' Equity	(19,383)	(17,980)
Eliminations and Other | Investments in Conrail
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	695	678
Eliminations and Other | Affiliates and Other Companies
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	(43)	(42)
Eliminations and Other | Investments in Consolidated Subsidiaries
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	$ (18,783)	$ (17,519)