Nature of Operations and Significant Accounting Policies (Policies)	6 Months Ended
Jun. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	In the opinion of management, the accompanying consolidated financial statements contain all normal, recurring adjustments necessary to fairly present the consolidated financial statements and accompanying notes. Where applicable, prior year information has been reclassified to conform to the current presentation. Pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”), certain information and disclosures normally included in the notes to the annual financial statements prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) have been omitted from these interim financial statements. CSX suggests that these financial statements be read in conjunction with the audited financial statements and the notes included in CSX's most recent annual report on Form 10-K and any subsequently filed current reports on Form 8-K.
Fiscal Year	The Company's fiscal periods are based upon the calendar year. Except as otherwise specified, references to “second quarter(s)” or “six months” indicate CSX's fiscal periods ending June 30, 2022 and June 30, 2021, and references to "year-end" indicate the fiscal year ended December 31, 2021.
New Accounting Pronouncements	In March 2020, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2020-04, Facilitation of the Effects of Reference Rate Reform on Financial Reporting. As the London Interbank Offered Rate ("LIBOR") will no longer be available beginning July 2023, this standard update provides practical expedients for contract modifications made as part of the transition from LIBOR to alternative reference rates. CSX's revolving line of credit currently uses LIBOR as a reference rate. This standard update can be adopted prospectively through December 31, 2022. The Company continues to evaluate the impact of this standard update, but does not anticipate that adoption will have a material impact on the Company's results of operations or financial position. In November 2021, the FASB issued ASU 2021-10, Disclosure by Business Entities about Government Assistance. This standard update requires annual disclosure of the nature of any government assistance received, accounting policies related to such assistance and the effect of that assistance on the entity’s financial statements. The Company will adopt this guidance effective year end 2022 and the standard update will not impact the Company's results of operations or financial position as the update only impacts disclosures.
Revenue Recognition	The Company generates revenue from rail freight billings under contracts with customers generally on a rate per carload, container or ton-basis based on length of haul and commodities carried. The Company’s performance obligation arises when it receives a bill of lading (“BOL”) to transport a customer's commodities at a negotiated price contained in a transportation services agreement or a publicly disclosed tariff rate. Once a BOL is received, a contract is formed whereby the parties are committed to perform, collectability of consideration is probable and the rights of the parties, shipping terms and conditions, and payment terms are identified. A customer may submit several BOLs for transportation services at various times throughout a service agreement term but each shipment represents a distinct service that is a separately identified performance obligation. The average transit time to complete a rail shipment is between 2 to 8 days depending on market. Payments for transportation services are normally billed once a BOL is received and are generally due within 15 days after the invoice date. The Company recognizes revenue over transit time of freight as it moves from origin to destination. Revenue for services started but not completed at the reporting date is allocated based on the relative transit time in each reporting period, with the portion allocated for services subsequent to the reporting date considered remaining performance obligations. The certain key estimates included in the recognition and measurement of revenue and related accounts receivable are as follows: •revenue associated with shipments in transit, which is recognized ratably over transit time and is based on average cycle times to move commodities and products from their origin to their final destination or interchange; •adjustments to revenue for billing corrections and billing discounts; •adjustments to revenue for overcharge claims filed by customers, which are based on historical payments to customers for rate overcharges as a percentage of total billing; and •incentive-based refunds to customers, which are primarily volume-related, are recorded as a reduction to revenue on the basis of the projected liability (this estimate is based on historical activity, current volume levels and forecasted future volume). Revenue related to interline transportation services that involve the services of another party, such as another railroad, is reported on a net basis. The portion of the gross amount billed to customers that is remitted by the Company to another party is not reflected as revenue. Effective third quarter 2021, trucking revenue includes revenue from the operations of Quality Carriers. This revenue is mostly comprised of truck shipments of chemicals and is recorded ratably over transit time. Other revenue is recorded upon completion of the service and is comprised of revenue from regional subsidiary railroads and incidental charges, including intermodal storage and equipment usage, demurrage and switching. Revenue from regional subsidiary railroads includes shipments by railroads that the Company does not directly operate. Intermodal storage represents charges for customer storage of containers at an intermodal terminal, ramp facility or offsite location beyond a specified period of time. Demurrage represents charges assessed when freight cars are held by a customer beyond a specified period of time. Switching represents charges assessed when a railroad switches cars for a customer or another railroad. Remaining performance obligations represent the transaction price allocated to future reporting periods for freight services started but not completed at the reporting date. This includes the unearned portion of billed and unbilled amounts for cancellable freight shipments in transit. The Company expects to recognize the unearned portion of revenue for freight services in transit within one week of the reporting date.The timing of revenue recognition, billings and cash collections results in accounts receivable and customer advances and deposits (contract liabilities) on the consolidated balance sheets. Freight receivables include amounts earned, billed and unbilled, and currently due from customers for transportation-related services. Non-freight receivables include amounts billed and unbilled and currently due related to government reimbursement receivables and other non-revenue receivables. At June 30, 2022, non-freight receivables include a $124 million receivable related to the sale of property rights to the Commonwealth of Virginia. See Note 1, Nature of Operations and Significant Accounting Policies, for more details about this transaction. The Company maintains an allowance for credit losses to provide for the estimated amount of receivables that will not be collected. The allowance is based upon an assessment of risk characteristics, historical payment experience, and the age of outstanding receivables adjusted for forward-looking economic conditions as necessary.
Fair Value Measurements	The Financial Instruments Topic in the ASC requires disclosures about fair value of financial instruments in annual reports as well as in quarterly reports. For CSX, this statement applies to certain investments, long-term debt and interest rate derivatives. Disclosure of the fair value of pension plan assets is only required annually. Also, this rule clarifies the definition of fair value for financial reporting, establishes a framework for measuring fair value and requires additional disclosures about the use of fair value measurements. Various inputs are considered when determining the value of the Company's investments, pension plan assets, long-term debt and interest rate derivatives. The inputs or methodologies used for valuing securities are not necessarily an indication of the risk associated with investing in these securities. These inputs are summarized in the three broad levels listed below. •Level 1 - observable market inputs that are unadjusted quoted prices for identical assets or liabilities in active markets; •Level 2 - other significant observable inputs (including quoted prices for similar securities, interest rates, credit risk, etc.); and •Level 3 - significant unobservable inputs (including the Company's own assumptions about the assumptions market participants would use in determining the fair value of investments). The valuation methods described below may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. Furthermore, while the Company believes its valuation methods are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different fair value measurement at the reporting date. Investments The Company's investment assets are carried at fair value on the consolidated balance sheet in accordance with the Fair Value Measurements and Disclosures Topic in the ASC. They are valued with assistance from a third-party trustee and consist of fixed income mutual funds, corporate bonds and government securities. The fixed income mutual funds are valued at the net asset value of shares held based on quoted market prices determined in an active market, which are Level 1 inputs. The corporate bonds and government securities are valued using broker quotes that utilize observable market inputs, which are Level 2 inputs. Long-term Debt Long-term debt is reported at carrying amount on the consolidated balance sheets and is the Company's only financial instrument with fair values significantly different from their carrying amounts. The majority of the Company's long-term debt is valued with assistance from a third party that utilizes closing transactions, market quotes or market values of comparable debt. For those instruments not valued by the third party, the fair value has been estimated by applying market rates of similar instruments to the scheduled contractual debt payments and maturities. These market rates are provided by the same third party. All of the inputs used to determine the fair value of the Company's long-term debt are Level 2 inputs. The fair value of outstanding debt fluctuates with changes in a number of factors. Such factors include, but are not limited to, interest rates, market conditions, credit ratings, values of similar financial instruments, size of the transaction, cash flow projections and comparable trades. Fair value will exceed carrying value when the current market interest rate is lower than the interest rate at which the debt was originally issued. The fair value of a company's debt is a measure of its current value under present market conditions. It does not impact the financial statements under current accounting rules.Interest Rate DerivativesThe Company’s fixed-to-floating and forward starting interest rate swaps are carried at their respective fair values, which are determined with assistance from a third party based upon pricing models using inputs observed from actively quoted markets. All of the inputs used to determine the fair value of the swaps are Level 2 inputs.

Nature of Operations and Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2022

Organization, Consolidation and Presentation of Financial Statements [Abstract]

In the opinion of management, the accompanying consolidated financial statements contain all normal, recurring adjustments necessary to fairly present the consolidated financial statements and accompanying notes. Where applicable, prior year information has been reclassified to conform to the current presentation. Pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”), certain information and disclosures normally included in the notes to the annual financial statements prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) have been omitted from these interim financial statements. CSX suggests that these financial statements be read in conjunction with the audited financial statements and the notes included in CSX's most recent annual report on Form 10-K and any subsequently filed current reports on Form 8-K.

Fiscal Year

The Company's fiscal periods are based upon the calendar year. Except as otherwise specified, references to “second quarter(s)” or “six months” indicate CSX's fiscal periods ending June 30, 2022 and June 30, 2021, and references to "year-end" indicate the fiscal year ended December 31, 2021.

New Accounting Pronouncements

In March 2020, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2020-04, Facilitation of the Effects of Reference Rate Reform on Financial Reporting. As the London Interbank Offered Rate ("LIBOR") will no longer be available beginning July 2023, this standard update provides practical expedients for contract modifications made as part of the transition from LIBOR to alternative reference rates. CSX's revolving line of credit currently uses LIBOR as a reference rate. This standard update can be adopted prospectively through December 31, 2022. The Company continues to evaluate the impact of this standard update, but does not anticipate that adoption will have a material impact on the Company's results of operations or financial position.

In November 2021, the FASB issued ASU 2021-10, Disclosure by Business Entities about Government Assistance. This standard update requires annual disclosure of the nature of any government assistance received, accounting policies related to such assistance and the effect of that assistance on the entity’s financial statements. The Company will adopt this guidance effective year end 2022 and the standard update will not impact the Company's results of operations or financial position as the update only impacts disclosures.

Revenue Recognition

The Company generates revenue from rail freight billings under contracts with customers generally on a rate per carload, container or ton-basis based on length of haul and commodities carried. The Company’s performance obligation arises when it receives a bill of lading (“BOL”) to transport a customer's commodities at a negotiated price contained in a transportation services agreement or a publicly disclosed tariff rate. Once a BOL is received, a contract is formed whereby the parties are committed to perform, collectability of consideration is probable and the rights of the parties, shipping terms and conditions, and payment terms are identified. A customer may submit several BOLs for transportation services at various times throughout a service agreement term but each shipment represents a distinct service that is a separately identified performance obligation.

The average transit time to complete a rail shipment is between 2 to 8 days depending on market. Payments for transportation services are normally billed once a BOL is received and are generally due within 15 days after the invoice date. The Company recognizes revenue over transit time of freight as it moves from origin to destination. Revenue for services started but not completed at the reporting date is allocated based on the relative transit time in each reporting period, with the portion allocated for services subsequent to the reporting date considered remaining performance obligations.

The certain key estimates included in the recognition and measurement of revenue and related accounts receivable are as follows:

•revenue associated with shipments in transit, which is recognized ratably over transit time and is based on average cycle times to move commodities and products from their origin to their final destination or interchange;

•adjustments to revenue for billing corrections and billing discounts;

•adjustments to revenue for overcharge claims filed by customers, which are based on historical payments to customers for rate overcharges as a percentage of total billing; and

•incentive-based refunds to customers, which are primarily volume-related, are recorded as a reduction to revenue on the basis of the projected liability (this estimate is based on historical activity, current volume levels and forecasted future volume).

Revenue related to interline transportation services that involve the services of another party, such as another railroad, is reported on a net basis. The portion of the gross amount billed to customers that is remitted by the Company to another party is not reflected as revenue.

Effective third quarter 2021, trucking revenue includes revenue from the operations of Quality Carriers. This revenue is mostly comprised of truck shipments of chemicals and is recorded ratably over transit time.

Other revenue is recorded upon completion of the service and is comprised of revenue from regional subsidiary railroads and incidental charges, including intermodal storage and equipment usage, demurrage and switching. Revenue from regional subsidiary railroads includes shipments by railroads that the Company does not directly operate. Intermodal storage represents charges for customer storage of containers at an intermodal terminal, ramp facility or offsite location beyond a specified period of time. Demurrage represents charges assessed when freight cars are held by a customer beyond a specified period of time. Switching represents charges assessed when a railroad switches cars for a customer or another railroad.

Remaining performance obligations represent the transaction price allocated to future reporting periods for freight services started but not completed at the reporting date. This includes the unearned portion of billed and unbilled amounts for cancellable freight shipments in transit. The Company expects to recognize the unearned portion of revenue for freight services in transit within one week of the reporting date.The timing of revenue recognition, billings and cash collections results in accounts receivable and customer advances and deposits (contract liabilities) on the consolidated balance sheets. Freight receivables include amounts earned, billed and unbilled, and currently due from customers for transportation-related services. Non-freight receivables include amounts billed and unbilled and currently due related to government reimbursement receivables and other non-revenue receivables. At June 30, 2022, non-freight receivables include a $124 million receivable related to the sale of property rights to the Commonwealth of Virginia. See Note 1, Nature of Operations and Significant Accounting Policies, for more details about this transaction. The Company maintains an allowance for credit losses to provide for the estimated amount of receivables that will not be collected. The allowance is based upon an assessment of risk characteristics, historical payment experience, and the age of outstanding receivables adjusted for forward-looking economic conditions as necessary.

Fair Value Measurements

The Financial Instruments Topic in the ASC requires disclosures about fair value of financial instruments in annual reports as well as in quarterly reports. For CSX, this statement applies to certain investments, long-term debt and interest rate derivatives. Disclosure of the fair value of pension plan assets is only required annually. Also, this rule clarifies the definition of fair value for financial reporting, establishes a framework for measuring fair value and requires additional disclosures about the use of fair value measurements.

Various inputs are considered when determining the value of the Company's investments, pension plan assets, long-term debt and interest rate derivatives. The inputs or methodologies used for valuing securities are not necessarily an indication of the risk associated with investing in these securities. These inputs are summarized in the three broad levels listed below.

•Level 1 - observable market inputs that are unadjusted quoted prices for identical assets or liabilities in active markets;

•Level 2 - other significant observable inputs (including quoted prices for similar securities, interest rates, credit risk, etc.); and

•Level 3 - significant unobservable inputs (including the Company's own assumptions about the assumptions market participants would use in determining the fair value of investments).

The valuation methods described below may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. Furthermore, while the Company believes its valuation methods are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different fair value measurement at the reporting date.

Investments

The Company's investment assets are carried at fair value on the consolidated balance sheet in accordance with the Fair Value Measurements and Disclosures Topic in the ASC. They are valued with assistance from a third-party trustee and consist of fixed income mutual funds, corporate bonds and government securities. The fixed income mutual funds are valued at the net asset value of shares held based on quoted market prices determined in an active market, which are Level 1 inputs. The corporate bonds and government securities are valued using broker quotes that utilize observable market inputs, which are Level 2 inputs.

Long-term Debt

Long-term debt is reported at carrying amount on the consolidated balance sheets and is the Company's only financial instrument with fair values significantly different from their carrying amounts. The majority of the Company's long-term debt is valued with assistance from a third party that utilizes closing transactions, market quotes or market values of comparable debt. For those instruments not valued by the third party, the fair value has been estimated by applying market rates of similar instruments to the scheduled contractual debt payments and maturities. These market rates are provided by the same third party. All of the inputs used to determine the fair value of the Company's long-term debt are Level 2 inputs.

The fair value of outstanding debt fluctuates with changes in a number of factors. Such factors include, but are not limited to, interest rates, market conditions, credit ratings, values of similar financial instruments, size of the transaction, cash flow projections and comparable trades. Fair value will exceed carrying value when the current market interest rate is lower than the interest rate at which the debt was originally issued. The fair value of a company's debt is a measure of its current value under present market conditions. It does not impact the financial statements under current accounting rules.Interest Rate DerivativesThe Company’s fixed-to-floating and forward starting interest rate swaps are carried at their respective fair values, which are determined with assistance from a third party based upon pricing models using inputs observed from actively quoted markets. All of the inputs used to determine the fair value of the swaps are Level 2 inputs.