Summarized Consolidating Financial Data - Consolidating Balance Sheet (Details) - USD ($) $ / shares in Units, $ in Millions	Jun. 30, 2017	Dec. 30, 2016	Jun. 24, 2016	Dec. 25, 2015
Current Assets:
Cash and Cash Equivalents	$ 620	$ 603	$ 566	$ 628
Short-term Investments	477	417
Accounts Receivable - Net	1,015	938
Receivable from Affiliates	0	0
Materials and Supplies	428	407
Other Current Assets	90	122
Total Current Assets	2,630	2,487
Properties	43,751	43,227
Accumulated Depreciation	(12,324)	(12,077)
Properties - Net	31,427	31,150
Other Long-term Assets	317	318
Total Assets	35,861	35,414
Current Liabilities:
Accounts Payable	810	806
Labor and Fringe Benefits Payable	506	545
Payable to Affiliates	0	0
Casualty, Environmental and Other Reserves	115	115
Current Maturities of Long-term Debt	19	331
Income and Other Taxes Payable	95	129
Other Current Liabilities	127	114
Total Current Liabilities	1,672	2,040
Casualty, Environmental and Other Reserves	248	259
Long-term Debt	11,806	10,962
Deferred Income Taxes - Net	9,737	9,596
Other Long-term Liabilities	797	863
Total Liabilities	24,260	23,720
Shareholders' Equity
Common Stock, $1 Par Value	913	928
Other Capital	210	138
Retained Earnings	11,033	11,253
Accumulated Other Comprehensive Loss	(569)	(640)
Noncontrolling Interest	14	15
Total Shareholders' Equity	11,601	11,694
Total Liabilities and Shareholders' Equity	$ 35,861	$ 35,414
Common stock, par value (in dollars per share)	$ 1	$ 1
Investments in Conrail
Current Assets:
Investment in Affiliates and Other Companies	$ 856	$ 840
Affiliates and Other Companies
Current Assets:
Investment in Affiliates and Other Companies	631	619
Investments in Consolidated Subsidiaries
Current Assets:
Investment in Affiliates and Other Companies	0	0
Eliminations and Other
Current Assets:
Cash and Cash Equivalents	9	17	19	9
Short-term Investments	12	2
Accounts Receivable - Net	722	721
Receivable from Affiliates	(3,969)	(3,508)
Materials and Supplies	0	0
Other Current Assets	16	16
Total Current Assets	(3,210)	(2,752)
Properties	2,771	2,708
Accumulated Depreciation	(1,499)	(1,442)
Properties - Net	1,272	1,266
Other Long-term Assets	(288)	(291)
Total Assets	(26,254)	(25,101)
Current Liabilities:
Accounts Payable	41	33
Labor and Fringe Benefits Payable	40	65
Payable to Affiliates	(4,493)	(3,957)
Casualty, Environmental and Other Reserves	13	13
Current Maturities of Long-term Debt	0	(1)
Income and Other Taxes Payable	33	16
Other Current Liabilities	5	2
Total Current Liabilities	(4,361)	(3,829)
Casualty, Environmental and Other Reserves	48	51
Long-term Debt	0	0
Deferred Income Taxes - Net	273	258
Other Long-term Liabilities	(319)	(330)
Total Liabilities	(4,359)	(3,850)
Shareholders' Equity
Common Stock, $1 Par Value	(181)	(181)
Other Capital	(5,095)	(5,095)
Retained Earnings	(16,639)	(15,994)
Accumulated Other Comprehensive Loss	20	19
Noncontrolling Interest	0	0
Total Shareholders' Equity	(21,895)	(21,251)
Total Liabilities and Shareholders' Equity	(26,254)	(25,101)
Eliminations and Other | Investments in Conrail
Current Assets:
Investment in Affiliates and Other Companies	856	840
Eliminations and Other | Affiliates and Other Companies
Current Assets:
Investment in Affiliates and Other Companies	15	15
Eliminations and Other | Investments in Consolidated Subsidiaries
Current Assets:
Investment in Affiliates and Other Companies	(24,899)	(24,179)
CSX Corporation
Current Assets:
Cash and Cash Equivalents	483	305	420	444
Short-term Investments	465	415
Accounts Receivable - Net	1	2
Receivable from Affiliates	1,158	1,157
Materials and Supplies	0	0
Other Current Assets	2	0
Total Current Assets	2,109	1,879
Properties	1	1
Accumulated Depreciation	(1)	(1)
Properties - Net	0	0
Other Long-term Assets	9	2
Total Assets	26,978	26,021
Current Liabilities:
Accounts Payable	100	95
Labor and Fringe Benefits Payable	70	40
Payable to Affiliates	3,998	3,457
Casualty, Environmental and Other Reserves	0	0
Current Maturities of Long-term Debt	0	313
Income and Other Taxes Payable	(387)	(346)
Other Current Liabilities	(1)	0
Total Current Liabilities	3,780	3,559
Casualty, Environmental and Other Reserves	0	0
Long-term Debt	11,050	10,203
Deferred Income Taxes - Net	(169)	(203)
Other Long-term Liabilities	730	783
Total Liabilities	15,391	14,342
Shareholders' Equity
Common Stock, $1 Par Value	913	928
Other Capital	210	138
Retained Earnings	11,033	11,253
Accumulated Other Comprehensive Loss	(569)	(640)
Noncontrolling Interest	0	0
Total Shareholders' Equity	11,587	11,679
Total Liabilities and Shareholders' Equity	26,978	26,021
CSX Corporation | Investments in Conrail
Current Assets:
Investment in Affiliates and Other Companies	0	0
CSX Corporation | Affiliates and Other Companies
Current Assets:
Investment in Affiliates and Other Companies	(39)	(39)
CSX Corporation | Investments in Consolidated Subsidiaries
Current Assets:
Investment in Affiliates and Other Companies	24,899	24,179
CSX Transportation
Current Assets:
Cash and Cash Equivalents	128	281	$ 127	$ 175
Short-term Investments	0	0
Accounts Receivable - Net	292	215
Receivable from Affiliates	2,811	2,351
Materials and Supplies	428	407
Other Current Assets	72	106
Total Current Assets	3,731	3,360
Properties	40,979	40,518
Accumulated Depreciation	(10,824)	(10,634)
Properties - Net	30,155	29,884
Other Long-term Assets	596	607
Total Assets	35,137	34,494
Current Liabilities:
Accounts Payable	669	678
Labor and Fringe Benefits Payable	396	440
Payable to Affiliates	495	500
Casualty, Environmental and Other Reserves	102	102
Current Maturities of Long-term Debt	19	19
Income and Other Taxes Payable	449	459
Other Current Liabilities	123	112
Total Current Liabilities	2,253	2,310
Casualty, Environmental and Other Reserves	200	208
Long-term Debt	756	759
Deferred Income Taxes - Net	9,633	9,541
Other Long-term Liabilities	386	410
Total Liabilities	13,228	13,228
Shareholders' Equity
Common Stock, $1 Par Value	181	181
Other Capital	5,095	5,095
Retained Earnings	16,639	15,994
Accumulated Other Comprehensive Loss	(20)	(19)
Noncontrolling Interest	14	15
Total Shareholders' Equity	21,909	21,266
Total Liabilities and Shareholders' Equity	35,137	34,494
CSX Transportation | Investments in Conrail
Current Assets:
Investment in Affiliates and Other Companies	0	0
CSX Transportation | Affiliates and Other Companies
Current Assets:
Investment in Affiliates and Other Companies	655	643
CSX Transportation | Investments in Consolidated Subsidiaries
Current Assets:
Investment in Affiliates and Other Companies	$ 0	$ 0