Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount Per Share

No definition available.

Name:	csx_EffectiveIncomeTaxRateReconciliationChangeinEnactedTaxRateAmountPerShare
Namespace Prefix:	csx_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Related Party Transaction, Notes Payable, Number of Notes

+ References

No definition available.

+ Details

Name:	csx_RelatedPartyTransactionNotesPayableNumberofNotes
Namespace Prefix:	csx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Difference between amount at which an investment accounted for under the equity method of accounting is carried (reported) on the balance sheet and amount of underlying equity in net assets the reporting Entity has in the investee.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentDifferenceBetweenCarryingAmountAndUnderlyingEquity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66022249&loc=d3e33749-111570

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_EquityMethodInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations, attributable to increase (decrease) in the income tax rates.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=84176650&loc=d3e32059-109318

+ Details

Name:	us-gaap_IncomeTaxReconciliationChangeInEnactedTaxRate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of interest expense incurred on a debt or other obligation to related party.

+ References

No definition available.

+ Details

Name:	us-gaap_InterestExpenseRelatedParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_CorporateJointVentureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=csx_TTXCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	csx_VotingInterestAxis=csx_VotinginterestinrelatedpartywhichisalsoanequitymethodinvestmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	csx_EconomicInterestAxis=csx_EconomicinterestinrelatedpartywhichisalsoanequitymethodinvestmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Related Parties and Affiliates - Narrative (Details) $ / shares in Units, $ in Millions		3 Months Ended	12 Months Ended
	Dec. 22, 2017 $ / shares	Dec. 31, 2017 USD ($) $ / shares	Dec. 31, 2017 USD ($)	Dec. 30, 2016 USD ($)	Dec. 25, 2015 USD ($)	Dec. 26, 2014 note
Related Party Transaction [Line Items]
Effect of change in enacted tax rate		$ 3,600	$ (3,506)	$ 0	$ 0
Effect of change in tax rate (in dollars per share) \| $ / shares	$ 3.81	$ 3.91
Corporate Joint Venture
Related Party Transaction [Line Items]
Difference between carrying amount and underlying equity		$ 347	347
Promissory notes executed \| note						2
Interest expense			$ 6	$ 6
TTX Company
Related Party Transaction [Line Items]
Ownership percentage		20.00%	20.00%
Equity method investments		$ 626	$ 626
Voting interest in related party which is also an equity method investment \| Corporate Joint Venture
Related Party Transaction [Line Items]
Ownership percentage		50.00%	50.00%
Economic interest in related party which is also an equity method investment \| Corporate Joint Venture
Related Party Transaction [Line Items]
Ownership percentage		42.00%	42.00%