Percentage Of Grants With Performance Vesting Operating Ratio

No definition available.

Name:	csx_PercentageOfGrantsWithPerformanceVestingOperatingRatio
Namespace Prefix:	csx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage Of Grants With Performance Vesting, Return On Assets

+ References

No definition available.

+ Details

Name:	csx_PercentageOfGrantsWithPerformanceVestingReturnOnAssets
Namespace Prefix:	csx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Share Based Compensation Arrangement by Share Base Payment Award Number of Equivalent Shares of Common Stock Per Unit (e.g. performance units, restricted stock units, etc.).

+ References

No definition available.

+ Details

Name:	csx_ShareBasedCompensationArrangementByShareBasePaymentAwardNumberOfEquivalentSharesOfCommonStockPerUnit
Namespace Prefix:	csx_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other than Options, Payout Percentage Downward Adjustment

+ References

No definition available.

+ Details

Name:	csx_ShareBasedCompensationArrangementbyShareBasedPaymentAwardEquityInstrumentsOtherthanOptionsPayoutPercentageDownwardAdjustment
Namespace Prefix:	csx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Share Based Compensation Arrangement by Share Based Payment Award Maximum Stock Value Purchased per Employee

+ References

No definition available.

+ Details

Name:	csx_ShareBasedCompensationArrangementbyShareBasedPaymentAwardMaximumStockValuePurchasedperEmployee
Namespace Prefix:	csx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other Than Options, Payout Percentage of Target

+ References

No definition available.

+ Details

Name:	csx_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsPayoutPercentageofTarget
Namespace Prefix:	csx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Aggregate number of common shares reserved for future issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_CommonStockCapitalSharesReservedForFutureIssuance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
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_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The highest percentage of annual salary that an employee is permitted to utilize with respect to the plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

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

- Definition

The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(3)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Gross number of share options (or share units) granted during the period.

+ References

No definition available.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

An excess of the fair value of the modified award over the fair value of the award immediately before the modification.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)(iii)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

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

- Definition

The number of employees affected by the modification of an equity-based compensation plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)(ii)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPlanModificationNumberOfEmployeesAffected
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

Name:	us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_PlanNameAxis=csx_LongTermIncentivePlansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=csx_EquityAwardModificationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_EmployeeStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_PerformanceSharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockUnitsRSUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_EmployeeStockOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TitleOfIndividualAxis=us-gaap_ChiefExecutiveOfficerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Share-Based Compensation - Narrative (Details)			1 Months Ended		3 Months Ended		9 Months Ended
Share-Based Compensation - Narrative (Details)	Feb. 06, 2018 shares	Mar. 06, 2017 employee	Feb. 28, 2018 $ / shares shares	Dec. 31, 2017 shares	Sep. 30, 2018 $ / shares	Sep. 30, 2017 $ / shares shares	Sep. 30, 2018 $ / shares shares	Sep. 30, 2017 USD ($) $ / shares	May 31, 2018 USD ($) shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted (in shares)			950,000			0
Fair value of stock options (in dollars per share) \| $ / shares			$ 14.55
2017 - 2019 LTIP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of payout subject to downward adjustment (up to)							25.00%
2017 - 2019 LTIP \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payout range for participants (as a percent)							0.00%
2017 - 2019 LTIP \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payout range for participants (as a percent)							200.00%
Equity Award Modifications
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of employees impacted (employees) \| employee		70
Share-based compensation expense revaluation of awards \| $								$ 31,000,000
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock registered for ESPP (in shares)									4,000,000
Maximum stock value available for purchase \| $									$ 25,000
Employee Stock Purchase Plan \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum payroll deduction (as a percent)									1.00%
Employee Stock Purchase Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum payroll deduction (as a percent)									10.00%
Performance Units \| 2017 - 2019 LTIP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)			350,000			0
Percentage of grants with performance vesting, operating ratio (as a percent)							50.00%
Percentage of grants with performance vesting, return on assets (as a percent)							50.00%
Performance unit equivalent of CSX common stock (in shares)							1
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)						0
Award vesting period (in years)	3 years
Restricted Stock Units (RSUs) \| 2017 - 2019 LTIP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)	85,000
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of stock options (in dollars per share) \| $ / shares					$ 20.52	$ 0.00	$ 14.65	$ 12.83
Term of stock options (in years)			10 years
Award vesting period (in years)			3 years
Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options forfeited (in shares)				9,000,000