Debt and Credit Agreements (Debt Issuance and Early Redemption of Long-term Debt) (Details) - USD ($)	12 Months Ended
Dec. 26, 2014	Dec. 25, 2015
Debt Instrument [Line Items]
Other expense recognized for early redemption premium	$ 16,000,000
Early redemption amount	663,000,000
Unsecured Debt [Member] \| Three Point Nine Five Percent Notes Due 2050 [Member]
Debt Instrument [Line Items]
Face amount of debt issued		$ 600,000,000
Notes issued, interest rate		3.95%
Unsecured Debt [Member] \| Three Point Three Five Percent Notes Due 2025 [Member] [Domain]
Debt Instrument [Line Items]
Face amount of debt issued		$ 600,000,000
Notes issued, interest rate		3.35%
Unsecured Debt [Member] \| Three Point Four Percent Notes Due 2024 [Member]
Debt Instrument [Line Items]
Face amount of debt issued	$ 550,000,000
Notes issued, interest rate	3.40%
Unsecured Debt [Member] \| Four Point Five Percent Notes Due 2054 [Member]
Debt Instrument [Line Items]
Face amount of debt issued	$ 450,000,000
Notes issued, interest rate	4.50%
Unsecured Debt [Member] \| CSX's Notes Payable Maturing April 1, 2015 [Member]
Debt Instrument [Line Items]
Face amount of debt issued	$ 400,000,000
Notes issued, interest rate	6.25%
Equipment Obligations [Member] \| Secured Equipment Notes Due October 15, 2014 [Member]
Debt Instrument [Line Items]
Face amount of debt issued	$ 263,000,000
Notes issued, interest rate	8.375%

Face (par) amount of debt instrument at time of issuance.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ 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 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- 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.

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- Definition

Gross amount of debt extinguished.

+ References

No definition available.

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- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=49170532&loc=d3e12317-112629

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=49170532&loc=d3e12355-112629

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