Summarized Consolidating Financial Data (Income Statements) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 26, 2014	Sep. 26, 2014	Jun. 27, 2014	Mar. 28, 2014	Dec. 27, 2013	Sep. 27, 2013	Jun. 28, 2013	Mar. 29, 2013	Dec. 26, 2014	Dec. 27, 2013	Dec. 28, 2012
Consolidated Income Statement
Revenue	$ 3,192	$ 3,221	$ 3,244	$ 3,012	$ 3,032	$ 2,985	$ 3,046	$ 2,963	$ 12,669	$ 12,026	$ 11,763
Operating Expenses									9,056	8,553	8,299
Operating Income	901	976	997	739	813	840	940	880	3,613	3,473	3,464
Equity in Earnings of Subsidiaries									0	0	0
Interest Expense									(545)	(562)	(566)
Other Income - Net									(24)	11	73
Earnings Before Income Taxes									3,044	2,922	2,971
Income Tax Benefit (Expense)									(1,117)	(1,058)	(1,108)
Net Earnings	491	509	529	398	426	455	521	462	1,927	1,864	1,863
Comprehensive Earnings									1,784	2,277	1,802
CSX Corporation
Consolidated Income Statement
Revenue									0	0	0
Operating Expenses									(427)	(371)	(355)
Operating Income									427	371	355
Equity in Earnings of Subsidiaries									1,996	1,964	1,992
Interest Expense									(520)	(516)	(513)
Nonoperating Income (Expense)											(3)
Other Income - Net									(19)	(7)
Earnings Before Income Taxes									1,884	1,812	1,831
Income Tax Benefit (Expense)									43	52	32
Net Earnings									1,927	1,864	1,863
Comprehensive Earnings									1,784	2,277	1,802
CSX Transportation
Consolidated Income Statement
Revenue									12,590	11,950	11,696
Operating Expenses									9,585	9,091	8,779
Operating Income									3,005	2,859	2,917
Equity in Earnings of Subsidiaries									1	(1)	(2)
Interest Expense									(46)	(62)	(70)
Nonoperating Income (Expense)											61
Other Income - Net									(4)	(2)
Earnings Before Income Taxes									2,956	2,794	2,906
Income Tax Benefit (Expense)									(1,093)	(1,028)	(1,065)
Net Earnings									1,863	1,766	1,841
Comprehensive Earnings									1,875	1,825	1,818
Eliminations and Other
Consolidated Income Statement
Revenue									79	76	67
Operating Expenses									(102)	(167)	(125)
Operating Income									181	243	192
Equity in Earnings of Subsidiaries									(1,997)	(1,963)	(1,990)
Interest Expense									21	16	17
Nonoperating Income (Expense)											15
Other Income - Net									(1)	20
Earnings Before Income Taxes									(1,796)	(1,684)	(1,766)
Income Tax Benefit (Expense)									(67)	(82)	(75)
Net Earnings									(1,863)	(1,766)	(1,841)
Comprehensive Earnings									$ (1,875)	$ (1,825)	$ (1,818)