Commitments and Contingencies (Insurance and Legal) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended
May 31, 2007 entity	Dec. 26, 2014
Insurance
Non-catastrophic property deductible		$ 25
Casualty and catastrophic property deductible		50
Pending Litigation [Member]
Loss Contingency, Estimate [Abstract]
Minimum range of possible loss for legal proceedings		4
Maximum range of possible loss for legal proceedings		$ 13
Fuel Surcharge Antitrust Litigation [Member]
Loss Contingency, Estimate [Abstract]
Number of other U.S.-based entities mentioned in class action lawsuit	3

Deductible amount for casualty and catastrophic property programs.

No definition available.

Name:	csx_CasualtyAndCatastrophicPropertyDeductible
Namespace Prefix:	csx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Deductible amount for non-catastrophic property programs.

+ References

No definition available.

+ Details

Name:	csx_CasualtyAndNonCatastrophicPropertyDeductible
Namespace Prefix:	csx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Loss Contingency, Claims Filed, Number Of Entities

+ References

No definition available.

+ Details

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

- Details

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

- Details

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

- Definition

The estimated maximum amount of possible loss from the contingency.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 9

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349

+ Details

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

- Definition

The estimated minimum amount of possible loss from the contingency.

+ References

+ Details

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

- Details

Name:	us-gaap_LitigationCaseAxis=csx_FuelSurchargeAntitrustLitigationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LitigationStatusAxis=us-gaap_PendingLitigationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: