Casualty, Environmental and Other Reserves (Casualty) (Details) (Casualty [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 26, 2014 claims	Dec. 27, 2013	Dec. 28, 2012	Dec. 30, 2011
Casualty [Member]
Loss Contingencies [Line Items]
Loss Contingency Accrual	$ 265	$ 280	$ 325	$ 372
Self-insured retention amount per injury	50
Individual claims expected to exceed self-insured retention amount	0
Change in estimate recorded to adjust reserves	$ 0	$ 0	$ 0

Changes in casualty reserves based on management's review of the actuarial analysis performed by an independent actuarial firm.

No definition available.

+ Details

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Namespace Prefix:	csx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Total number of claims expected to exceed self-insured retention amount, as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	csx_LossContingencyNumberOfClaimsExpectedToExceedSelfInsuredRetentionAmount
Namespace Prefix:	csx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Details

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

- Definition

Amount of loss contingency liability.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying amount (including both current and noncurrent portions) of accrued known and estimated losses incurred as of the balance sheet date for which no insurance coverage exists, and for which a claim has been made or is probable of being asserted, typically arising from workmen's compensation-type of incidents and personal injury to nonemployees from accidents on the entity's property.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.24)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant