Summarized Consolidating Financial Data (Balance Sheets) (Details) (USD $) In Millions, unless otherwise specified	Dec. 30, 2011	Dec. 31, 2010	Dec. 25, 2009	Dec. 26, 2008
Current Assets
Cash and Cash Equivalents	$ 783	$ 1,292	$ 1,029	$ 669
Short-term Investments	523	54
Accounts Receivable - Net	1,129	993
Receivable from Affiliates	0	0
Materials and Supplies	240	218
Deferred Income Taxes	182	192
Other Current Assets	78	106
Total Current Assets	2,935	2,855
Properties	33,704	32,065
Accumulated Depreciation	(8,730)	(8,266)
Properties - Net	24,974	23,799
Other Long-term Assets	393	353
Total Assets	29,473	28,141
Current Liabilities
Accounts Payable	1,147	1,046
Labor and Fringe Benefits Payable	541	520
Payable to Affiliates	0	0
Casualty, Environmental and Other Reserves	183	176
Current Maturities of Long-term Debt (Note 9)	507	613
Income and Other Taxes Payable	129	85
Other Current Liabilities	180	97
Total Current Liabilities	2,687	2,537
Casualty, Evironmental and Other Reserves	458	502
Long-term Debt	8,734	8,051
Deferred Income Taxes	7,601	7,053
Other Long-term Liabilities	1,525	1,298
Total Liabilities	21,005	19,441
Shareholders' Equity
Common Stock, $1 Par Value	1,049	370
Other Capital	6	0
Retained Earnings	8,275	9,087
Accumulated Other Comprehensive Loss	(875)	(771)	(809)
Noncontrolling Interest	13	14
Total Shareholders' Equity	8,468	8,700	8,768	7,985
Total Liabilities and Shareholders' Equity	29,473	28,141
Investments in Conrail
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	678	673
Affiliates and Other Companies
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	493	461
Investments in Consolidated Subsidiaries
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	0	0
CSX Corporation
Current Assets
Cash and Cash Equivalents	549	1,100	918	559
Short-term Investments	475	0
Accounts Receivable - Net	4	5
Receivable from Affiliates	1,025	1,048
Materials and Supplies	0	0
Deferred Income Taxes	10	15
Other Current Assets	17	46
Total Current Assets	2,080	2,214
Properties	8	8
Accumulated Depreciation	(8)	(8)
Properties - Net	0	0
Other Long-term Assets	176	174
Total Assets	19,736	18,666
Current Liabilities
Accounts Payable	114	116
Labor and Fringe Benefits Payable	41	42
Payable to Affiliates	2,566	1,942
Casualty, Environmental and Other Reserves	0	0
Current Maturities of Long-term Debt (Note 9)	400	517
Income and Other Taxes Payable	(60)	378
Other Current Liabilities	(1)	0
Total Current Liabilities	3,060	2,995
Casualty, Evironmental and Other Reserves	0	0
Long-term Debt	7,609	6,815
Deferred Income Taxes	(246)	(526)
Other Long-term Liabilities	858	696
Total Liabilities	11,281	9,980
Shareholders' Equity
Common Stock, $1 Par Value	1,049	370
Other Capital	6	0
Retained Earnings	8,275	9,087
Accumulated Other Comprehensive Loss	(875)	(771)
Noncontrolling Interest	0	0
Total Shareholders' Equity	8,455	8,686
Total Liabilities and Shareholders' Equity	19,736	18,666
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)	0
CSX Corporation | Investments in Consolidated Subsidiaries
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	17,519	16,278
CSX Transportation
Current Assets
Cash and Cash Equivalents	154	118	30	63
Short-term Investments	0	0
Accounts Receivable - Net	468	447
Receivable from Affiliates	1,772	943
Materials and Supplies	240	218
Deferred Income Taxes	173	171
Other Current Assets	64	56
Total Current Assets	2,871	1,953
Properties	31,958	30,557
Accumulated Depreciation	(7,795)	(7,405)
Properties - Net	24,163	23,152
Other Long-term Assets	109	110
Total Assets	27,717	25,810
Current Liabilities
Accounts Payable	978	904
Labor and Fringe Benefits Payable	458	431
Payable to Affiliates	374	401
Casualty, Environmental and Other Reserves	167	161
Current Maturities of Long-term Debt (Note 9)	105	94
Income and Other Taxes Payable	189	109
Other Current Liabilities	178	96
Total Current Liabilities	2,449	2,196
Casualty, Evironmental and Other Reserves	369	411
Long-term Debt	1,124	1,235
Deferred Income Taxes	7,800	7,228
Other Long-term Liabilities	582	525
Total Liabilities	12,324	11,595
Shareholders' Equity
Common Stock, $1 Par Value	181	181
Other Capital	5,652	5,634
Retained Earnings	9,618	8,443
Accumulated Other Comprehensive Loss	(79)	(65)
Noncontrolling Interest	21	22
Total Shareholders' Equity	15,393	14,215
Total Liabilities and Shareholders' Equity	27,717	25,810
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	574	595
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	80	74	81	47
Short-term Investments	48	54
Accounts Receivable - Net	657	541
Receivable from Affiliates	(2,797)	(1,991)
Materials and Supplies	0	0
Deferred Income Taxes	(1)	6
Other Current Assets	(3)	4
Total Current Assets	(2,016)	(1,312)
Properties	1,738	1,500
Accumulated Depreciation	(927)	(853)
Properties - Net	811	647
Other Long-term Assets	108	69
Total Assets	(17,980)	(16,335)
Current Liabilities
Accounts Payable	55	26
Labor and Fringe Benefits Payable	42	47
Payable to Affiliates	(2,940)	(2,343)
Casualty, Environmental and Other Reserves	16	15
Current Maturities of Long-term Debt (Note 9)	2	2
Income and Other Taxes Payable	0	(402)
Other Current Liabilities	3	1
Total Current Liabilities	(2,822)	(2,654)
Casualty, Evironmental and Other Reserves	89	91
Long-term Debt	1	1
Deferred Income Taxes	47	351
Other Long-term Liabilities	85	77
Total Liabilities	(2,600)	(2,134)
Shareholders' Equity
Common Stock, $1 Par Value	(181)	(181)
Other Capital	(5,652)	(5,634)
Retained Earnings	(9,618)	(8,443)
Accumulated Other Comprehensive Loss	79	65
Noncontrolling Interest	(8)	(8)
Total Shareholders' Equity	(15,380)	(14,201)
Total Liabilities and Shareholders' Equity	(17,980)	(16,335)
Eliminations and Other | Investments in Conrail
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	678	673
Eliminations and Other | Affiliates and Other Companies
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	(42)	(134)
Eliminations and Other | Investments in Consolidated Subsidiaries
Current Assets
Investment in Affiliates, Subsidiaries, and Joint Ventures	$ (17,519)	$ (16,278)