Summarized Consolidating Financial Data (Income Statements) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 30, 2016	Sep. 23, 2016	Jun. 24, 2016	Mar. 25, 2016	Dec. 25, 2015	Sep. 25, 2015	Jun. 26, 2015	Mar. 27, 2015	Dec. 30, 2016	Dec. 25, 2015	Dec. 26, 2014
Consolidated Income Statement
Revenue	$ 3,037	$ 2,710	$ 2,704	$ 2,618	$ 2,781	$ 2,939	$ 3,064	$ 3,027	$ 11,069	$ 11,811	$ 12,669
Expense									7,680	8,227	9,056
Operating Income	1,004	841	840	704	791	933	1,017	843	3,389	3,584	3,613
Equity in Earnings of Subsidiaries									0	0	0
Interest Expense									(579)	(544)	(545)
Other Income - Net									(69)	98	(24)
Earnings Before Income Taxes									2,741	3,138	3,044
Income Tax Benefit (Expense)									(1,027)	(1,170)	(1,117)
Net Earnings	$ 458	$ 455	$ 445	$ 356	$ 466	$ 507	$ 553	$ 442	1,714	1,968	1,927
Total Comprehensive Earnings									1,739	1,969	1,784
CSX Corporation
Consolidated Income Statement
Revenue									0	0	0
Expense									(265)	(589)	(427)
Operating Income									265	589	427
Equity in Earnings of Subsidiaries									1,997	1,949	1,996
Interest Expense									(583)	(539)	(520)
Other Income - Net									(112)	(4)	(19)
Earnings Before Income Taxes									1,567	1,995	1,884
Income Tax Benefit (Expense)									147	(27)	43
Net Earnings									1,714	1,968	1,927
Total Comprehensive Earnings									1,739	1,969	1,784
CSX Transportation
Consolidated Income Statement
Revenue									10,991	11,733	12,590
Expense									8,100	8,922	9,585
Operating Income									2,891	2,811	3,005
Equity in Earnings of Subsidiaries									2	0	1
Interest Expense									(35)	(33)	(46)
Other Income - Net									44	111	(4)
Earnings Before Income Taxes									2,902	2,889	2,956
Income Tax Benefit (Expense)									(1,081)	(1,083)	(1,093)
Net Earnings									1,821	1,806	1,863
Total Comprehensive Earnings									1,833	1,806	1,875
Eliminations and Other
Consolidated Income Statement
Revenue									78	78	79
Expense									(155)	(106)	(102)
Operating Income									233	184	181
Equity in Earnings of Subsidiaries									(1,999)	(1,949)	(1,997)
Interest Expense									39	28	21
Other Income - Net									(1)	(9)	(1)
Earnings Before Income Taxes									(1,728)	(1,746)	(1,796)
Income Tax Benefit (Expense)									(93)	(60)	(67)
Net Earnings									(1,821)	(1,806)	(1,863)
Total Comprehensive Earnings									$ (1,833)	$ (1,806)	$ (1,875)