Boardwalk Pipeline Partners (BWP) 10-K 6 Feb 24 2023 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Feb. 06, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	01-32665
Entity Registrant Name	BOARDWALK PIPELINE PARTNERS, LP
Entity Incorporation, State	DE
Entity Tax Identification Number	20-3265614
Entity Address, Address Line One	9 Greenway Plaza,
Entity Address, Address Line Two	Suite 2800
Entity Address, City	Houston,
Entity Address, State	TX
Entity Address, Postal Zip Code	77046
City Area Code	(866)
Local Phone Number	913-2122
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction	false
Entity Shell Company	false
Documents Incorporated by Reference	None.
Entity Central Index Key	0001336047
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding (in shares)		0
Entity Public Float			$ 0

Audit Information

Audit Information	12 Months Ended
	Dec. 31, 2023
Audit Information [Abstract]
Auditor Location	Houston, Texas
Auditor Name	Deloitte & Touche LLP
Auditor Firm ID	34

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Current Assets:
Cash and cash equivalents	$ 20.1	$ 215.6
Receivables:
Trade, net	204.6	148.4
Other	24.9	25.4
Gas transportation receivables	7	22
Gas stored underground and other product inventory	3.3	41.6
Prepayments	24.3	23.7
Other current assets	4.5	8.7
Total current assets	288.7	485.4
Property, Plant and Equipment:
Property, plant and equipment, gross	13,529.5	12,804.3
Less—accumulated depreciation and amortization	4,672.9	4,288.3
Property, plant and equipment, net	8,856.6	8,516
Other Assets:
Goodwill	237.4	237.4
Gas stored underground	99.3	153.5
Other	214.4	177.6
Total other assets	551.1	568.5
Total Assets	9,696.4	9,569.9
Payables:
Trade	113.2	70.7
Gas transportation payables	7.8	41.2
Accrued taxes, other	67.9	62.8
Accrued interest	34.2	33.9
Accrued payroll and employee benefits	44	38.3
Regulatory liabilities	15.1	55.1
Other current liabilities	60.3	50.7
Total current liabilities	362.3	372.7
Long-term debt and finance lease obligation	3,261.9	3,233.4
Other Liabilities and Deferred Credits:
Pension liability	4.7	8.8
Asset retirement obligations	59.2	53.9
Provision for other asset retirement	98.1	93.2
Other	119.1	105.7
Total other liabilities and deferred credits	281.1	261.6
Commitments and Contingencies
Partners' Capital:
Partners' capital	5,867.7	5,781.7
Accumulated other comprehensive loss	(76.6)	(79.5)
Total partners' capital	5,791.1	5,702.2
Total Liabilities and Partners' Capital	9,696.4	9,569.9
Affiliates
Payables:
Payables	3.4	2.6
Other
Payables:
Payables	16.4	17.4
Natural gas transmission and other plant
Property, Plant and Equipment:
Property, plant and equipment, gross	13,242.3	12,616.7
Construction work in progress
Property, Plant and Equipment:
Property, plant and equipment, gross	$ 287.2	$ 187.6

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating Revenues:
Transportation	$ 1,287	$ 1,228.8	$ 1,152.6
Storage, parking and lending	160.9	129.2	110.4
Product sales	100.3	11.1	11.7
Other	69.5	62.9	65.4
Total operating revenues	1,617.7	1,432	1,340.1
Operating Costs and Expenses:
Fuel and transportation	26.3	22.4	22.1
Product costs	87.8	1	0
Operation and maintenance	281	250.9	226.9
Administrative and general	171.9	147.7	144.6
Depreciation and amortization	408.7	392.3	366.3
Loss (gain) on sale of assets, impairments and other	0.3	4	(0.1)
Taxes other than income taxes	115.5	114.5	113.2
Total operating costs and expenses	1,091.5	932.8	873
Operating income	526.2	499.2	467.1
Other Deductions (Income):
Interest expense	155.6	165.9	160.8
Interest income	(12.1)	(3.3)	0
Miscellaneous other income, net	(4.1)	(6.4)	(9.4)
Total other deductions	139.4	156.2	151.4
Income before income taxes	386.8	343	315.7
Income taxes	0.8	0.8	0.7
Net income	$ 386	$ 342.2	$ 315

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 386	$ 342.2	$ 315
Other comprehensive income (loss):
Reclassification adjustment transferred to Net income from cash flow hedges	0.1	0.5	0.9
Pension and other postretirement benefit costs, net of tax	2.8	(7.4)	6.3
Total Comprehensive Income	$ 388.9	$ 335.3	$ 322.2

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
OPERATING ACTIVITIES:
Net income	$ 386	$ 342.2	$ 315
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	408.7	392.3	366.3
Amortization of deferred costs and other	18.5	4	9
Loss (gain) on sale of assets, impairments and other	0.3	4	(0.1)
Changes in operating assets and liabilities:
Trade and other receivables	(7.8)	(16.7)	(19.1)
Gas transportation receivables, storage assets and other product inventory	70.6	(63.4)	(32.8)
Prepayments and other assets	3.1	(9.8)	(2.7)
Trade and other payables	11.5	15.6	1.1
Other payables, affiliates	0.1	(0.2)	0
Gas transportation payables	(20.8)	21	9.3
Accrued liabilities	7.4	(0.9)	(1.3)
Regulatory assets and liabilities	(40.3)	49.3	(4.1)
Other liabilities	(19.9)	(10.6)	(11.3)
Net cash provided by operating activities	817.4	726.8	629.3
INVESTING ACTIVITIES:
Capital expenditures	(382.4)	(344.3)	(349.2)
Proceeds from sale of operating assets	0.3	1.5	1.7
Acquisition of business	(355)	0	0
Net cash used in investing activities	(737.1)	(342.8)	(347.5)
FINANCING ACTIVITIES:
Proceeds from long-term debt, net of issuance cost	0	495	0
Repayment of borrowings from long-term debt	0	(600)	0
Proceeds from borrowings on revolving credit facility	155	0	150
Repayments of borrowings on revolving credit facility, including financing fees	(130.6)	(0.6)	(284.4)
Principal payment of finance lease obligation	(0.9)	(0.8)	(0.8)
Advances from affiliates	0.7	1.1	(8.2)
Distributions paid	(300)	(102.2)	(102.2)
Net cash used in financing activities	(275.8)	(207.5)	(245.6)
(Decrease) increase in cash and cash equivalents	(195.5)	176.5	36.2
Cash and cash equivalents at beginning of period	215.6	39.1	2.9
Cash and cash equivalents at end of period	$ 20.1	$ 215.6	$ 39.1

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN PARTNERS' CAPITAL - USD ($) $ in Millions	Total	Accumulated Other Comprehensive Income (Loss)	Partners' Capital
Beginning Balance at Dec. 31, 2020	$ 5,249.1	$ (79.8)	$ 5,328.9
Add (deduct):
Net income	315		315
Distributions paid	(102.2)		(102.2)
Other comprehensive income (loss), net of tax	7.2	7.2
Ending Balance at Dec. 31, 2021	5,469.1	(72.6)	5,541.7
Add (deduct):
Net income	342.2		342.2
Distributions paid	(102.2)		(102.2)
Other comprehensive income (loss), net of tax	(6.9)	(6.9)
Ending Balance at Dec. 31, 2022	5,702.2	(79.5)	5,781.7
Add (deduct):
Net income	386		386
Distributions paid	(300)		(300)
Other comprehensive income (loss), net of tax	2.9	2.9
Ending Balance at Dec. 31, 2023	$ 5,791.1	$ (76.6)	$ 5,867.7

Corporate Structure

Corporate Structure	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Corporate Structure	Corporate Structure Boardwalk Pipeline Partners, LP (the Company) is a Delaware limited partnership formed in 2005 to own and operate the business conducted by its primary subsidiary Boardwalk Pipelines, LP (Boardwalk Pipelines) and its operating subsidiaries, Gulf South Pipeline Company, LLC (Gulf South), Texas Gas Transmission, LLC (Texas Gas), Boardwalk Louisiana Midstream, LLC (Louisiana Midstream), Boardwalk Louisiana Gas Transmission, LLC, Boardwalk Texas Intrastate, LLC, Boardwalk Petrochemical Pipeline, LLC, and Boardwalk Ethane Pipeline Company, LLC (together, the operating subsidiaries), which consists of integrated pipeline and storage systems for natural gas and natural gas liquids and other hydrocarbons (herein referred to together as NGLs). All of the Company's operations are conducted by the operating subsidiaries. As of December 31, 2023, Boardwalk Pipelines Holding Corp. (BPHC), a wholly owned subsidiary of Loews Corporation (Loews), owned directly or indirectly, 100% of the Company's capital.

Basis of Presentation and Signi

Basis of Presentation and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	Basis of Presentation and Significant Accounting Policies Basis of Presentation The accompanying consolidated financial statements of the Company have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S.) (GAAP). Certain amounts reported in Other revenues and Fuel and transportation expense were reclassified to Product sales and Product costs to conform to the current presentation in connection with the acquisition discussed in Note 3. The amounts reclassified represent NGL product sales that occurred during 2022 and 2021. The effect of the reclassification was a decrease in Other revenues and an increase in Product sales of $11.1 million and $11.7 million for the years ended December 31, 2022 and 2021, and a decrease in Fuel and transportation expense and an increase in Product costs of $1.0 million and an immaterial amount for the years ended December 31, 2022 and 2021. These reclassifications had no impact on Total operating revenues , Operating income or Net income . Principles of Consolidation The consolidated financial statements include the Company's accounts and those of its wholly owned subsidiaries after elimination of intercompany transactions. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, disclosure of contingent assets and liabilities and the fair values of certain items. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, which form the basis for making judgments about the carrying amounts of assets and liabilities that are not readily apparent from other sources. Actual results could differ from such estimates. Segment Information The Company operates in one reportable segment - the operation of interstate natural gas and NGLs pipeline systems and integrated storage facilities. This segment consists of interstate natural gas pipeline systems located in the Gulf Coast region, Oklahoma, Arkansas, Tennessee, Kentucky, Illinois, Indiana and Ohio and integrated natural gas storage facilities located in Indiana, Kentucky, Louisiana and Mississippi, and NGLs pipelines and storage facilities located in Louisiana and Texas. Regulatory Accounting Most of the Company's natural gas pipeline subsidiaries and its interstate ethane transportation pipeline are regulated by the Federal Energy Regulatory Commission (FERC). When certain criteria are met, GAAP requires that certain rate-regulated entities account for and report assets and liabilities consistent with the economic effect of the manner in which independent third-party regulators establish rates (regulatory accounting). This basis of accounting is applicable to operations of the Company's Texas Gas subsidiary, which records certain costs and benefits as regulatory assets and liabilities in order to provide for recovery from or refunds to customers in future periods, but is not applicable to the operations associated with the Fayetteville and Greenville Laterals due to rates charged under negotiated rate agreements and a portion of Texas Gas' storage capacity due to the regulatory treatment associated with the rates charged for that capacity. The Company also applies regulatory accounting for its fuel trackers on Gulf South, under which the value of fuel received from customers paying the maximum tariff rate and the related value of fuel used in transportation are recorded to a regulatory asset or liability depending on whether Gulf South uses more fuel than it collects from customers or collects more fuel than it uses. Other than as described for Texas Gas and for the fuel trackers on Gulf South, regulatory accounting is not applicable to the Company's other FERC-regulated operations. The Company monitors the regulatory and competitive environment in which it operates to determine whether its regulatory assets continue to be probable of recovery. If the Company determines that all or a portion of its regulatory assets no longer meets the criteria for recognition as regulatory assets, that portion which is not recoverable will be written off, net of any regulatory liabilities. Note 11 contains more information regarding the Company's regulatory assets and liabilities. Fair Value Measurements Fair value refers to an exit price that would be received to sell an asset or paid to transfer a liability in an orderly transaction in the principal market in which the reporting entity transacts based on the assumptions market participants would use when pricing the asset or liability assuming its highest and best use. A fair value hierarchy has been established that prioritizes the information used to develop those assumptions giving priority, from highest to lowest, to quoted prices in active markets for identical assets and liabilities (Level 1); observable inputs not included in Level 1, for example, quoted prices for similar assets and liabilities (Level 2); and unobservable data (Level 3), for example, a reporting entity's own internal data based on the best information available in the circumstances. The Company uses fair value measurements to account for business combinations, equity securities, asset retirement obligations (ARO), pension and postretirement benefits other than pension (PBOP) assets and any impairment charges. Notes 3, 7 and 13 contain more information regarding fair value measurements. Cash and Cash Equivalents Cash equivalents are highly liquid investments with an original maturity of three months or less and are stated at cost plus accrued interest, which approximates fair value. The Company had no restricted cash at December 31, 2023 and 2022. Trade and Other Receivables Trade and other receivables are stated at their historical carrying amount, net of allowances for doubtful accounts. The Company establishes an allowance for doubtful accounts under an expected credit loss model based on historical credit loss experience and specific facts and circumstances. Uncollectible receivables are written off when a settlement is reached for an amount that is less than the outstanding historical balance or a receivable amount is deemed otherwise unrealizable. Gas Stored Underground and Gas Receivables and Payables Certain of the Company's operating subsidiaries have underground gas in storage which is utilized for system management and operational balancing, as well as for services including firm and interruptible storage associated with certain no-notice and parking and lending (PAL) services. Gas stored underground includes the historical cost of natural gas volumes owned by the operating subsidiaries, at times reduced by certain operational encroachments upon that gas. The operating subsidiaries provide storage services whereby they store natural gas or NGLs on behalf of customers and also periodically hold customer gas under PAL services. Since the customers retain title to the gas held by the Company in providing these services, the Company does not record the related gas on the Consolidated Balance Sheets . Certain of the Company's operating subsidiaries also periodically lend gas and NGLs to customers. In the course of providing transportation and storage services to customers, the operating subsidiaries may receive different quantities of gas from shippers and operators than the quantities delivered on behalf of those shippers and operators. This results in transportation and exchange gas receivables and payables, commonly known as imbalances, which are primarily settled in cash or the receipt or delivery of gas in the future. Settlement of imbalances requires agreement between the pipelines and shippers or operators as to allocations of volumes to specific transportation contracts and timing of delivery of gas based on operational conditions. The receivables and payables are valued at market price for operations where regulatory accounting is not applicable and are valued at the historical value of gas in storage for operations where regulatory accounting is applicable. Materials and Supplies Materials and supplies are carried at average cost and are included in Other Assets on the Consolidated Balance Sheets. The Company expects its materials and supplies to be used for projects related to its property, plant and equipment (PPE) and for future growth projects. At December 31, 2023 and 2022, the Company held approximately $38.1 million and $34.3 million of materials and supplies. Property, Plant and Equipment and Repair and Maintenance Costs PPE is recorded at its original cost of construction or fair value of assets purchased. Construction costs and expenditures for major renewals and improvements which extend the lives of the respective assets are capitalized. Construction work in progress is included in the financial statements as a component of PPE. Repair and maintenance costs are expensed as incurred. Depreciation of PPE related to operations for which regulatory accounting does not apply is provided for using the straight-line method of depreciation over the estimated useful lives of the assets, which range from 3 to 35 years. The ordinary sale or retirement of PPE for these assets could result in a gain or loss being recorded in the income statement. Depreciation of PPE related to operations for which regulatory accounting is applicable is provided for primarily on the straight-line method at FERC-prescribed rates over estimated useful lives of 5 to 62 years. Reflecting the application of composite depreciation, gains and losses from the ordinary sale or retirement of PPE for these assets are not recognized in earnings and generally do not impact PPE, net. Note 8 contains more information regarding the Company's PPE. Goodwill and Intangible Assets Goodwill represents the excess of the cost of an acquisition over the fair value of the net identifiable assets acquired and liabilities assumed. Goodwill is tested for impairment at the reporting unit level at least annually, as of November 30, or more frequently when events occur and circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount. A reporting entity may perform an optional qualitative assessment on an annual basis to determine whether events occurred or circumstances changed that would more likely than not reduce the fair value of a reporting unit below its carrying amount. If an initial qualitative assessment identifies that it is more likely than not that the fair value of a reporting unit is less than its carrying amount, or the optional qualitative assessment is not performed, a quantitative analysis is performed. The quantitative goodwill impairment test is performed by calculating the fair value of the reporting unit and comparing it to the reporting unit's carrying amount. If the fair value of a reporting unit exceeds its carrying amount, goodwill of the reporting unit is not impaired. However, if the carrying amount of a reporting unit exceeds its fair value, an impairment loss is recognized in an amount equal to that excess, limited to the total amount of goodwill recorded on the reporting unit. Intangible assets are those assets which provide future economic benefit but have no physical substance. The Company recorded intangible assets for customer relationships obtained through its acquisitions. The customer relationships, which are included in Other Assets on the Consolidated Balance Sheets, have a finite life and are being amortized over their estimated useful lives. Notes 3 and 9 contains more information regarding the Company's goodwill and intangible assets. Impairment of Long-lived Assets (including Tangible and Definite-lived Intangible Assets) The Company evaluates its long-lived and intangible assets for impairment when, in management's judgment, events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. When such a determination has been made, management's estimate of undiscounted future cash flows attributable to the remaining economic useful life of the asset (or asset group) is compared to the carrying amount of the asset (or asset group) to determine whether an impairment has occurred. If an impairment of the carrying amount has occurred, the amount of impairment recognized in the financial statements is determined by estimating the fair value of the assets (or asset group) and recording a loss to the extent that the carrying amount exceeds the estimated fair value. Capitalized Interest and Allowance for Funds Used During Construction (AFUDC) The Company records capitalized interest, which represents the cost of borrowed funds used to finance construction activities for operations where regulatory accounting is not applicable. The Company records AFUDC, which represents the cost of funds, including equity funds, applicable to regulated natural gas transmission plant under construction as permitted by FERC regulatory practices, in connection with the Company's operations where regulatory accounting is applicable. Capitalized interest and the allowance for borrowed funds used during construction are recognized as a reduction to Interest expense and the allowance for equity funds used during construction is included in Miscellaneous other income, net on the Consolidated Statements of Income. The following table summarizes capitalized interest and the allowance for borrowed funds and allowance for equity funds used during construction (in millions): For the Year Ended 2023 2022 2021 Capitalized interest and allowance for borrowed funds used during construction $ 3.6 $ 2.2 $ 3.8 Allowance for equity funds used during construction 5.7 6.2 7.9 Income Taxes The Company is not a taxable entity for federal income tax purposes. As such, it does not directly pay federal income tax. The Company's taxable income or loss, which may vary substantially from the net income or loss reported on the Consolidated Statements of Income, is includable in the federal income tax returns of each of its partners. The aggregate difference in the basis of the Company's net assets for financial and income tax purposes is $5.6 billion. The subsidiaries of the Company directly incur some income-based state taxes which are presented in Income taxes on the Consolidated Statements of Income. Note 14 contains more information regarding the Company's income taxes. Asset Retirement Obligations The accounting requirements for existing legal obligations associated with the future retirement of long-lived assets require entities to record the fair value of a liability for an ARO in the period during which the liability is incurred. The liability is initially recognized at fair value and is increased with the passage of time as accretion expense is recorded, until the liability is ultimately settled. The accretion expense is included within Operation and maintenance costs on the Consolidated Statements of Income. An amount corresponding to the amount of the initial liability is capitalized as part of the carrying amount of the related long-lived asset and depreciated over the useful life of that asset. Note 10 contains more information regarding the Company's ARO. Environmental Liabilities The Company records environmental liabilities based on management's estimates of the undiscounted future obligation for probable costs associated with environmental assessment and remediation of operating sites. These estimates are based on evaluations and discussions with counsel and operating personnel and the current known facts and circumstances related to these environmental matters. Note 6 contains more information regarding the Company's environmental liabilities. Defined Benefit Plans The Company maintains postretirement benefit plans for certain employees. The Company funds these plans through periodic contributions which are invested until the benefits are paid out to the participants, and records an asset or liability based on the overfunded or underfunded status of the plan. The net benefit costs of the plans are recorded on the Consolidated Statements of Income. Any deferred amounts related to unrecognized gains and losses or changes in actuarial assumptions are recorded as either a regulatory asset or liability or recorded as a component of accumulated other comprehensive income until those gains or losses are recognized on the Consolidated Statements of Income. Note 13 contains more information regarding the Company's pension and other postretirement benefit obligations. Long-Term Compensation The Company provides performance awards (Performance Awards) to certain of its employees under its 2018 Long-Term Incentive Plan (2018 LTIP). A Performance Award is a long-term incentive award with a stated target amount which is payable in cash, after certain adjustments, upon vesting based on certain specified performance criteria being met. The Company measures the cost of an award issued in exchange for employee services based on the stated target amount for Performance Awards. All outstanding awards are required to be settled in cash and are classified as a liability until settlement. The related compensation expense, less forfeitures, is recognized over the period that employees are required to provide services in exchange for the awards, usually the vesting period. Note 13 contains more information regarding the Company's long-term compensation. Partner Capital Accounts For purposes of maintaining capital accounts, items of income and loss of the Company are allocated among the partners each period, or portion thereof, in accordance with the partnership agreement, based on their respective ownership interests. Leases Operating lease right-of-use assets and lease liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. The discount rate used to determine the commencement date present value of lease payments is typically the Company's secured borrowing rate, as the implicit rate of most of the Company's leases is not readily determinable. The Company has elected not to record any leases with terms of twelve months or less on the Consolidated Balance Sheets. Revenue Recognition Nature of Contracts The Company primarily earns revenues from contracts with customers by providing transportation and storage services for natural gas and NGLs on a firm and interruptible basis and providing ethane supply and transportation services for industrial customers in Louisiana and Texas. The Company also provides interruptible natural gas PAL services. The Company's customers choose, based upon their particular needs, the applicable mix of services depending upon availability of pipeline and storage capacity, the price of services and the volume and timing of customer requirements. The maximum applicable rates that may be charged by the majority of the Company's operating subsidiaries are established through the FERC's cost-based rate-making process; however, the FERC also allows for discounted or negotiated rates as an alternative to cost-based rates. Under the FERC regulations, certain revenues that the Company's subsidiaries collect may be subject to possible refunds to customers. Accordingly, during a rate case, estimated refund liabilities are recorded considering regulatory proceedings, advice of counsel and estimated risk-adjusted total exposure, as well as other factors. The Company's service contracts can range from one to twenty years although the Company may enter into shorter- or longer-term contracts, and services are invoiced monthly with payment from the customer generally expected within ten Firm Service Contracts : The Company offers firm services to its customers. The Company's customers can reserve a specific amount of pipeline capacity at specified receipt and delivery points on the Company's pipeline system (transportation service) or can reserve a specific amount of storage capacity at specified injection and withdrawal points at the Company's storage facilities (storage service). The Company accounts for firm services as a single promise to stand ready each month of the contract term to provide the committed capacity for either transportation or storage services when needed by the customer, which represents a series of distinct monthly services that are substantially the same with the same pattern of transfer to the customer. Although several activities may be required to provide the firm service, the individual activities do not represent distinct performance obligations because all of the activities must be performed in combination in order for the Company to provide the firm service. The transaction price for firm service contracts is comprised of a fixed fee based on the quantity of capacity reserved, regardless of use (capacity reservation fee), plus variable fees in the form of a usage fee paid on the volume of commodity actually transported or injected and withdrawn from storage. Both the fixed and usage fees are allocated to the single performance obligation of providing transportation or storage service and recognized over time based upon the output measure of time as the Company completes its stand-ready obligation to provide contracted capacity and the customer receives and consumes the benefit of the reserved capacity, which corresponds with the transfer of control to the customer. The fixed fee is recognized ratably over the contract term, representative of the proportion of the committed stand-ready capacity obligation that has been fulfilled to date, and the usage fee is recognized upon satisfaction of each distinct monthly performance obligation, consistent with the allocation objective and based upon the level of effort required to satisfy the stand-ready obligation in a given month. Capacity reservation revenues derived from a firm service contract are generally consistent during the contract term, but can be higher in winter periods than the rest of the year based upon seasonal rates. Interruptible Service Contracts : In providing interruptible services to customers, the Company agrees to transport or store natural gas or NGLs for a customer when capacity is available. The Company does not account for interruptible services with a customer as a contract until the customer nominates for service and the Company accepts the nomination based upon available pipeline or storage capacity or product availability because there are no enforceable rights and obligations until that time. The nomination and acceptance process is a daily activity and acceptance is granted based upon priority of service and availability of capacity and products. Upon acceptance, the Company accounts for interruptible services similarly to its firm services. The transaction price for interruptible service contracts is comprised of a variable fee in the form of a usage fee paid on the volume of commodity actually transported or injected and withdrawn from storage. The transaction price is allocated to the single performance obligation of providing interruptible service. Interruptible service revenues for natural gas transportation and storage are generally recognized over time based on the output measure of volume transported or stored when services are rendered upon the successful allocation of the services provided to the customer's account, which best depicts the transfer of control to the customer and satisfaction of the promised service. Interruptible services are recognized in the month services are provided because the Company has a right to consideration from customers in amounts that correspond directly to the value that the customer receives from the Company's performance. The rates charged may vary on a daily, monthly or seasonal basis. Minimum Volume Commitment (MVC) Contracts : Certain of the Company's transportation, storage or ethane supply contracts require customers to transport, store or purchase a minimum volume of commodity over a specified time period. If a customer fails to meet its MVC for the specified time period, the customer is obligated to pay a contractually-determined deficiency fee based upon the shortfall between the actual volumes transported, stored or purchased and the MVC for that period. MVC contracts are generally similar in nature to a firm service contract where the performance obligation is a stand-ready obligation that is a series of distinct services that are substantially the same with the same pattern of transfer to the customer. The transaction price for a MVC is a fee for the volume of commodity actually transported, stored or delivered, which is allocated to each distinct monthly performance obligation, consistent with the allocation objective and based upon the level of effort required to satisfy the obligation of the transacted activities in a given month. Revenues associated with transportation and storage services are generally recognized over time based on the output measure of volume transported or stored and revenues associated with ethane supply are generally recognized at a point in time based on barrels delivered, with the recognition of the deficiency fee in the period when it is known the customer cannot make up the deficient volume in the specified period. Other: Certain ethane supply contracts include a stated volume that the Company supplies to customers, and any volume requested above the stated volume is based on product availability. Revenues for these ethane supply contracts are generally recognized at a point in time when each barrel is transferred to the customer because the customer is able to direct the use of, and obtain substantially all of the remaining benefits from, the product at that time. Periodically, the Company may also enter into contracts with customers for the sale of natural gas or NGLs. The Company recognizes revenues for these transactions at the point in time of the physical sale of the commodity, which corresponds with the transfer of control of the commodity to the customer and the consideration is measured as the stated sales price in the contract. Contract Balances The Company records contract assets primarily related to performance obligations completed but not billed, or partially billed, as of the reporting date. The Company records contract liabilities, or deferred revenue, when payment is received in advance of satisfying its performance obligations.

Acquisition

Acquisition	12 Months Ended
	Dec. 31, 2023
Business Combination and Asset Acquisition [Abstract]
Acquisition	Acquisition On September 29, 2023, Boardwalk Resources Company, LLC, a wholly owned subsidiary of the Company, acquired 100% of the equity interests of Williams Olefins Pipeline Holdco LLC (Bayou Ethane) from Williams Field Services Group, LLC for $355.0 million in cash, including working capital. Bayou Ethane owns an approximately 380-mile pipeline system that transports ethane from Mont Belvieu, Texas, to the Mississippi River corridor in Louisiana and two 15-mile pipelines in the Houston Ship Channel area that carry ammonia and hydrogen chloride. Bayou Ethane provides ethane supply and transportation services for industrial customers in Louisiana and Texas. In providing ethane supply services, Bayou Ethane purchases ethane at Mont Belvieu and various locations in Louisiana and utilizes its pipeline to deliver supply to its customers. The acquisition allows the Company to extend its assets, diversify its customer base and service offerings and to complement its existing NGLs operations. The purchase price was funded with available cash on hand. The acquisition was accounted for as a business combination. The purchase price was allocated to the assets acquired and liabilities assumed based on their estimated fair values on the date of acquisition. The fair values for PPE, including rights-of-way, were determined primarily using a combination of the market and cost approaches. The fair values for the customer-based intangibles were determined using a discounted cash flow analysis with inputs not observable in the market, such as estimated future cash flows and weighted-average cost of capital rates, which were considered Level 3 fair value estimates. During the fourth quarter 2023, the purchase price allocation was finalized. The final fair values of the assets acquired and liabilities assumed as of September 29, 2023, the acquisition date, were as follows (in millions): Current assets $ 51.8 Property, plant and equipment 296.2 Customer-based intangibles (1) 33.9 Noncurrent assets 0.5 Total assets acquired 382.4 Current liabilities 26.7 Noncurrent liabilities 0.7 Total liabilities assumed 27.4 Net assets acquired $ 355.0 (1) Customer-based intangibles have a weighted-average useful life of 35 years and are recorded in Other Assets. For the year ended December 31, 2023, the acquisition contributed $101.5 million and $5.5 million to the Company's operating revenues and net income. The Company incurred an immaterial amount of acquisition costs related to the acquisition for the year ended December 31, 2023. Acquisition costs were expensed as incurred and are recorded in Administrative and general on the Consolidated Statements of Income. Pro Forma Financial Information (unaudited) The following unaudited pro forma results of operations are presented as if the acquisition occurred on January 1, 2022. Such results are not necessarily indicative of future results. These pro forma results also do not reflect any cost savings, operating synergies or revenue enhancements that the Company may achieve or the costs necessary to achieve those objectives (in millions): Pro Forma For the Year Ended December 31, 2023 2022 Operating revenue (1)(2) $ 1,962.8 $ 2,253.4 Net income (2) 393.8 357.4 (1) Bayou Ethane provides ethane supply services, which result in ethane sales and purchases being presented on a gross basis in the Consolidated Statements of Income. (2) The average ethane price of $0.25 per gallon for the year ended December 31, 2023, was lower as compared to $0.48 per gallon for the comparable period for 2022, which resulted in higher revenues in the 2022 period. The pro forma information was adjusted for the following items: • Revenues and operating costs were based on actual results for the periods indicated. Acquisition costs were not material and were excluded; and • Depreciation and amortization expense was calculated using PPE and intangible asset amounts as determined by the purchase price allocation and estimated useful lives.

Revenues

Revenues	12 Months Ended
	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Revenues	Revenues The Company operates in one reportable segment. It contracts directly with end-use customers, including electric power generators, local distribution companies, industrial users and exporters of liquefied natural gas. The Company also contracts with other customers, including producers and marketers of natural gas and interstate and intrastate pipelines, who, in turn, provide transportation and storage services for end-users. The following table presents the Company's revenues disaggregated by type of service (in millions): For the Year Ended December 31, 2023 2022 2021 Revenues from Contracts with Customers Firm Service (1)(3) $ 1,489.7 $ 1,311.9 $ 1,247.5 Interruptible Service 51.6 56.2 32.0 Other revenues (3) 40.2 29.9 26.1 Total Revenues from Contracts with Customers 1,581.5 1,398.0 1,305.6 Other operating revenues (2)(3) 36.2 34.0 34.5 Total Operating Revenues $ 1,617.7 $ 1,432.0 $ 1,340.1 (1) Revenues earned from contracts with MVCs are included in firm service given the stand-ready nature of the performance obligation and the guaranteed nature of the fees over the contract term. (2) Other operating revenues include certain revenues earned from operating leases, pipeline management fees and other activities that are not considered central and ongoing major business operations of the Company and do not represent revenues earned from contracts with customers. (3) Revenues attributable to Bayou Ethane were $74.9 million in firm service, $25.4 million in other revenues and $1.2 million in other operating revenues for the year ended December 31, 2023. Contract Balances As of December 31, 2023 and 2022, the Company had receivables recorded in Trade Receivables, net from contracts with customers of $204.6 million and $148.4 million, contract assets recorded in Other Assets from contracts with a customer of $6.2 million and $3.3 million, and contract liabilities recorded in Other Current Liabilities (current portion) and Other Liabilities (noncurrent portion) from contracts with customers of $21.4 million and $23.0 million. As of December 31, 2023, contract liabilities are expected to be recognized through 2040. Significant changes in the contract liability balances during the year ended December 31, 2023, were as follows (in millions): Contract Liabilities Balance as of December 31, 2022 (1) $ 23.0 Revenues recognized that were included in the contract liability (3.9) Increases due to cash received, excluding amounts recognized as 1.8 Other 0.5 Balance as of December 31, 2023 (1) $ 21.4 (1) As of December 31, 2023 and 2022, $3.5 million and $3.6 million were recorded in Other Current Liabilities (current portion), and $17.9 million and $19.4 million were recorded in Other Liabilities (noncurrent portion). Significant changes in the contract liability balances during the year ended December 31, 2022, were as follows (in millions): Contract Liabilities Balance as of December 31, 2021 (1) $ 19.2 Revenues recognized that were included in the contract liability (5.1) Increases due to cash received, excluding amounts recognized as 8.9 Balance as of December 31, 2022 (1) $ 23.0 (1) As of December 31, 2022 and 2021, $3.6 million was recorded in Other Current Liabilities (current portion) and $19.4 million and $15.6 million were recorded in Other Liabilities (noncurrent portion). Performance Obligations The following table includes estimated operating revenues expected to be recognized in the future related to agreements that contain performance obligations that were unsatisfied as of December 31, 2023. The amounts presented primarily consist of fixed fees or MVCs which are typically recognized over time as the performance obligation is satisfied, in accordance with firm service contracts or guaranteed minimum fees associated with the performance obligation that are satisfied at a point in time under certain ethane supply contracts. For the Company's customers that are charged maximum tariff rates related to its FERC-regulated operating subsidiaries, the amounts below reflect the current tariff rate for such services for the term of the agreements; however, the tariff rates may be subject to future adjustment. The Company has elected to exclude the following from the table: (a) unsatisfied performance obligations from usage fees associated with its firm services because of the variable nature of such services; (b) unsatisfied performance obligations from the ethane commodity indexed portion of the ethane supply contracts because of the variable nature of ethane prices, and (c) consideration in contracts that is recognized in revenue as invoiced, such as for interruptible services. The estimated revenues reflected in the table may include estimated revenues that are anticipated under executed precedent transportation agreements for projects that are subject to regulatory approvals. In millions 2024 2025 Thereafter Total Estimated revenues from contracts with customers from unsatisfied performance obligations as of December 31, 2023 $ 1,362.0 $ 1,250.0 $ 6,840.5 $ 9,452.5 Operating revenues which are fixed and 28.0 27.5 163.5 219.0 Total projected operating revenues under committed firm agreements as of December 31, 2023 $ 1,390.0 $ 1,277.5 $ 7,004.0 $ 9,671.5

Leases

Leases	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Leases	Leases The Company has various operating lease commitments extending through 2058, generally covering office space and equipment rentals, some of which contain options to renew or extend the lease term. The Company also has a finance lease related to the lease of an office building in Owensboro, Kentucky, entered into in 2013, that has a fifteen-year term with two twenty-year renewal options. The components of lease cost were as follows (in millions): For the Year Ended December 31, 2023 2022 2021 Operating lease cost $ 3.8 $ 3.8 $ 4.0 Short-term lease cost 4.7 3.1 2.9 Finance lease cost: Amortization of right-of-use asset 0.7 0.7 0.7 Interest on lease liability 0.3 0.3 0.4 Total lease cost $ 9.5 $ 7.9 $ 8.0 The following provides supplemental balance sheet information related to the Company's leases: As of December 31, 2023 2022 Right-of-use assets (in millions) Operating leases (recorded in Other Assets ) $ 18.9 $ 18.7 Finance lease (recorded in Property, Plant and Equipment ) 3.2 4.0 Lease liabilities (in millions) Operating leases (recorded in Other Liabilities , current and non-current) 19.6 20.6 Finance lease (recorded in Other Current Liabilities and Long-term debt and finance lease obligation ) 4.5 5.4 Weighted-average remaining lease term (years) Operating leases 9.9 10.4 Finance lease 4.6 5.6 Weighted-average discount rate Operating leases 3.20 % 2.86 % Finance lease 5.89 % 5.89 % The table below presents the maturities of lease liabilities (in millions): As of December 31, 2023 Operating Finance 2024 $ 3.7 $ 1.1 2025 2.6 1.1 2026 1.9 1.1 2027 1.3 1.1 2028 0.3 0.7 Thereafter 13.3 — Total 23.1 5.1 Less: discount (3.5) (0.6) Total lease liabilities $ 19.6 $ 4.5
Leases	Leases The Company has various operating lease commitments extending through 2058, generally covering office space and equipment rentals, some of which contain options to renew or extend the lease term. The Company also has a finance lease related to the lease of an office building in Owensboro, Kentucky, entered into in 2013, that has a fifteen-year term with two twenty-year renewal options. The components of lease cost were as follows (in millions): For the Year Ended December 31, 2023 2022 2021 Operating lease cost $ 3.8 $ 3.8 $ 4.0 Short-term lease cost 4.7 3.1 2.9 Finance lease cost: Amortization of right-of-use asset 0.7 0.7 0.7 Interest on lease liability 0.3 0.3 0.4 Total lease cost $ 9.5 $ 7.9 $ 8.0 The following provides supplemental balance sheet information related to the Company's leases: As of December 31, 2023 2022 Right-of-use assets (in millions) Operating leases (recorded in Other Assets ) $ 18.9 $ 18.7 Finance lease (recorded in Property, Plant and Equipment ) 3.2 4.0 Lease liabilities (in millions) Operating leases (recorded in Other Liabilities , current and non-current) 19.6 20.6 Finance lease (recorded in Other Current Liabilities and Long-term debt and finance lease obligation ) 4.5 5.4 Weighted-average remaining lease term (years) Operating leases 9.9 10.4 Finance lease 4.6 5.6 Weighted-average discount rate Operating leases 3.20 % 2.86 % Finance lease 5.89 % 5.89 % The table below presents the maturities of lease liabilities (in millions): As of December 31, 2023 Operating Finance 2024 $ 3.7 $ 1.1 2025 2.6 1.1 2026 1.9 1.1 2027 1.3 1.1 2028 0.3 0.7 Thereafter 13.3 — Total 23.1 5.1 Less: discount (3.5) (0.6) Total lease liabilities $ 19.6 $ 4.5

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Proceedings and Settlements The Company and its subsidiaries are parties to various legal actions arising in the normal course of business. Management believes the disposition of these outstanding legal actions, including the legal actions identified below, will not have a material impact on the Company's financial condition, results of operations or cash flows. Mishal and Berger Litigation On May 25, 2018, plaintiffs Tsemach Mishal and Paul Berger (on behalf of themselves and the purported class, Plaintiffs) initiated a purported class action in the Court of Chancery of the State of Delaware (the Trial Court) against the following defendants: the Company, Boardwalk GP, LP (Boardwalk GP), Boardwalk GP, LLC and BPHC (together, Defendants), regarding the potential exercise by Boardwalk GP of its right to purchase the issued and outstanding common units of the Company not already owned by Boardwalk GP or its affiliates (Purchase Right). On June 25, 2018, Plaintiffs and Defendants entered into a Stipulation and Agreement of Compromise and Settlement, subject to the approval of the Trial Court (the Proposed Settlement). Under the terms of the Proposed Settlement, the lawsuit would be dismissed, and related claims against the Defendants would be released by the Plaintiffs, if BPHC, the sole member of the general partner of Boardwalk GP, elected to cause Boardwalk GP to exercise its Purchase Right for a cash purchase price, as determined by the Company's Third Amended and Restated Agreement of Limited Partnership, as amended (the Limited Partnership Agreement), and gave notice of such election as provided in the Limited Partnership Agreement within a period specified by the Proposed Settlement. On June 29, 2018, Boardwalk GP elected to exercise the Purchase Right and gave notice within the period specified by the Proposed Settlement. On July 18, 2018, Boardwalk GP completed the purchase of the Company's common units pursuant to the Purchase Right. On September 28, 2018, the Trial Court denied approval of the Proposed Settlement. On February 11, 2019, a substitute verified class action complaint was filed in this proceeding, which, among other things, added Loews as a Defendant. The Defendants filed a motion to dismiss, which was heard by the Trial Court in July 2019. In October 2019, the Trial Court ruled on the motion and granted a partial dismissal, with certain aspects of the case proceeding to trial. A trial was held the week of February 22, 2021, and post-trial oral arguments were held on July 14, 2021. On November 12, 2021, the Trial Court issued a ruling in the case. The Trial Court held that Boardwalk GP breached the Limited Partnership Agreement and found that Boardwalk GP is liable to the Plaintiffs for approximately $690.0 million in damages, plus pre-judgment interest (approximately $166.0 million), post-judgment interest and attorneys' fees. The Trial Court's ruling and damages award was against Boardwalk GP, and not the Company or its subsidiaries. The Defendants believed that the Trial Court ruling included factual and legal errors. Therefore, on January 3, 2022, the Defendants appealed the Trial Court's ruling to the Supreme Court of the State of Delaware (the Supreme Court). On January 17, 2022, the Plaintiffs filed a cross-appeal to the Supreme Court contesting the calculation of damages by the Trial Court. Oral arguments were held on September 14, 2022, and on December 19, 2022, the Supreme Court reversed the Trial Court's ruling and remanded the case to the Trial Court for further proceedings related to claims not decided by the Trial Court's ruling . Briefing by the parties at the Trial Court on the remanded issues was completed in September 2023. A hearing on the remanded issues is scheduled at the Trial Court in April 2024. City of New Orleans Litigation Gulf South, along with several other energy companies operating in Southern Louisiana, has been named as a defendant in a petition for damages and injunctive relief in state district court for Orleans Parish, Louisiana, (Case No. 19-3466) by the City of New Orleans. The case was filed on March 29, 2019. The lawsuit claims include, among other things, negligence, strict liability, nuisance and breach of contract, alleging that the defendants' drilling, dredging, pipeline and industrial operations since the 1930s have caused increased storm surge risk, increased flood protection costs and unspecified damages to the City of New Orleans. In October 2020, this case was stayed pending the outcome of a consolidated appeal to the Fifth Circuit Court of Appeals in a similar case. On August 5, 2021, the Fifth Circuit Court of Appeals ruled in favor of the oil-and-gas defendants in that consolidated appeal, finding that the two cases being appealed should be re-examined in federal district court since they involve operations that were federally overseen at the time. The ruling reverses a previous decision that allowed the cases to be heard in state court, which the plaintiffs had sought. As a result of the Fifth Circuit Court of Appeals' decision, it is anticipated that this case will be reviewed in federal district court to determine whether the case should be heard in that court. Gulf South and Texas Gas have been named as defendants in several suits in the State of Louisiana that are similar in nature to the City of New Orleans Litigation discussed above. These cases were filed in Louisiana state courts and are advancing to discovery. Environmental and Safety Matters The Company's operating subsidiaries are subject to federal, state, and local environmental laws and regulations in connection with the operation and remediation of various operating sites. As of December 31, 2023 and 2022, the Company had an accrued liability of approximately $10.1 million and $3.0 million related to assessment and/or remediation costs associated with the historical use of polychlorinated biphenyls, petroleum hydrocarbons and mercury. The liability represents management's estimate of the undiscounted future obligations based on evaluations and discussions with counsel and operating personnel and the current known facts and circumstances related to these matters. The related expenditures are expected to occur over the next thirty years. As of December 31, 2023 and 2022, approximately $6.7 million and $1.3 million were recorded in Other Current Liabilities and approximately $3.4 million and $1.7 million were recorded in Other Liabilities . Clean Air Act and Climate Change The Company's pipelines and associated facilities are subject to the Clean Air Act (CAA) and comparable state laws and regulations, which regulate the emission of air pollutants from many sources and impose various compliance monitoring and reporting requirements. Under the CAA, the Company may be required to obtain pre-approval for the construction or modification of certain projects or facilities expected to produce or significantly increase air emissions, obtain and strictly comply with stringent air permit requirements or utilize specific equipment or technologies to control emissions. The need to obtain permits has the potential to delay the development or expansion of the Company's projects. Over the next several years, the Company may be required to incur certain capital expenditures for air pollution control equipment or other air emissions related issues. For example, in 2015, the Environmental Protection Agency (EPA) issued a final rule under the CAA, lowering the National Ambient Air Quality Standard (NAAQS) for ground-level ozone to 70 parts per billion under both the primary and secondary standards to provide requisite protection of public health and welfare, respectively. Since that time, the EPA issued area designations with respect to ground-level ozone, issued final requirements that apply to state, local and tribal air agencies for implementing the 2015 NAAQS for ground-level ozone and, on December 31, 2020, published notice of a final action to retain the 2015 ozone NAAQS without revision on a going-forward basis. However, several groups filed litigation over the December 2020 final action and in October 2021, the EPA announced that it would reconsider the December 2020 determination to maintain the November 2015 NAAQS. In August 2023, the EPA announced a new review of the ozone NAAQS to ensure the standards protect people’s health and reflect the most current, relevant science. The new review will incorporate the reconsideration of the December 2020 final action. Until a final decision following the review is released, the full extent of the impacts of any new standards are not clear. States are expected to implement more stringent regulations that could apply to the Company's operations. Compliance with any final decision could, among other things, require installation of new emission controls on some of the Company's equipment, result in longer permitting timelines and significantly increase its capital expenditures and operating costs. Additionally, the threat of climate change continues to attract considerable public, governmental and scientific attention. As a result, numerous proposals have been made and are likely to continue to be made at the international, national, regional, state and local levels of government to monitor and limit emissions of greenhouse gases (GHGs). These efforts have included consideration of cap-and-trade programs, carbon taxes, and GHG reporting and tracking programs, and regulations that directly limit GHG emissions from certain sources. The EPA has determined that GHG emissions endanger public health and the environment and, as a result, has adopted regulations under the CAA related to GHG emissions. Commitments for Construction The Company's future capital commitments are comprised of binding commitments under purchase orders for materials ordered but not received and firm commitments under binding construction service agreements. As of December 31, 2023, the commitments were approximately $134.2 million, all of which are expected to be settled within the next twelve months. Pipeline Capacity and Storage Agreements The Company's operating subsidiaries have entered into pipeline capacity and storage agreements with third-party pipelines that allow the operating subsidiaries to transport gas to off-system markets on behalf of customers or store natural gas. Additionally, in connection with the Bayou Ethane acquisition, the Company has assumed a pipeline capacity agreement with a third party to facilitate the transportation of ethane and an ethane storage agreement. The Company incurred expenses of $5.8 million, $3.2 million and $7.7 million related to pipeline capacity and storage agreements for the years ended December 31, 2023, 2022 and 2021. The table below presents the future commitments related to these agreements as of December 31, 2023 (in millions): 2024 $ 7.9 2025 8.0 2026 8.0 2027 3.2 2028 0.1 Thereafter — Total $ 27.2

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Financial Assets and Liabilities The Company had equity securities recorded at fair value on a recurring basis in Other Current Assets of $2.3 million and $3.0 million as of December 31, 2023 and 2022. The equity securities were received as part of a settlement of a bankruptcy claim. The equity securities were valued based on quoted market prices at December 31, 2023 and 2022, and were considered Level 1 investments. The Company had no liabilities recorded at fair value on a recurring basis as of December 31, 2023 and 2022. Financial Assets and Liabilities Not Measured at Fair Value The following methods and assumptions were used in estimating the fair value amounts included in the disclosures for financial assets and liabilities: Cash and Cash Equivalents: For cash and short-term financial assets, the carrying amount is a reasonable estimate of fair value due to the short maturity of those instruments. Long-Term Debt: The estimated fair value of the Company's publicly traded debt is based on quoted market prices at December 31, 2023 and 2022. The fair market value of the debt that is not publicly traded is based on market prices of similar debt at December 31, 2023 and 2022. The carrying amount of the Company's variable-rate debt at December 31, 2023, approximated fair value because the instruments bear a floating market-based interest rate. The carrying amounts and estimated fair values of the Company's financial assets and liabilities which were not recorded at fair value on the Consolidated Balance Sheets as of December 31, 2023 and 2022, were as follows (in millions): As of December 31, 2023 Estimated Fair Value Financial Assets Carrying Amount Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 20.1 $ 20.1 $ — $ — $ 20.1 Financial Liabilities Long-term debt $ 3,262.4 (1) $ — $ 3,155.3 $ — $ 3,155.3 (1) The carrying amount of long-term debt excluded a $3.6 million long-term finance lease obligation and $4.1 million of unamortized debt issuance costs. As of December 31, 2022 Estimated Fair Value Financial Assets Carrying Amount Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 215.6 $ 215.6 $ — $ — $ 215.6 Financial Liabilities Long-term debt $ 3,234.0 (1) $ — $ 3,041.4 $ — $ 3,041.4 (1) The carrying amount of long-term debt excluded a $4.5 million long-term finance lease obligation and $5.1 million of unamortized debt issuance costs.

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment The following table presents the Company's PPE as of December 31, 2023 and 2022 (in millions): Category 2023 2023 Weighted-Average Useful Lives (Years) 2022 2022 Weighted-Average Useful Lives (Years) Depreciable plant: Transmission $ 11,405.4 38 $ 10,913.0 38 Storage 951.3 39 921.9 38 Gathering 106.1 24 111.1 24 General, intangibles and other 535.4 20 473.0 21 Total utility depreciable plant 12,998.2 37 12,419.0 37 Non-depreciable: Construction work in progress 287.2 187.6 Storage 197.5 151.6 Land 46.6 46.1 Total non-depreciable assets 531.3 385.3 Total PPE, gross 13,529.5 12,804.3 Less: accumulated depreciation and amortization 4,672.9 4,288.3 Total PPE, net $ 8,856.6 $ 8,516.0 The non-depreciable assets were not included in the calculation of the weighted-average useful lives. For the years ended December 31, 2023, 2022 and 2021, depreciation expense for PPE was $406.5 million, $390.4 million and $364.4 million and was recorded in Depreciation and amortization on the Consolidated Statements of Income. The Company holds undivided interests in certain assets, including the Mobile Bay Pipeline, of which the Company owns 64%, and offshore and other assets, comprised of pipeline and gathering assets in which the Company holds various ownership interests. In addition, the Company owns 83% of two ethylene wells and supporting surface facilities in Choctaw, Louisiana, and certain ethylene and propylene pipelines connecting Louisiana Midstream's storage facilities in Choctaw to chemical manufacturing plants in Geismar, Louisiana. The proportionate share of investment associated with these interests has been recorded as PPE on the Consolidated Balance Sheets. The Company records its portion of direct operating expenses associated with the assets in Operation and maintenance expense. The following table presents the gross PPE investment and related accumulated depreciation for the Company's undivided interests as of December 31, 2023 and 2022 (in millions): 2023 2022 Gross PPE Accumulated Depreciation Gross PPE Accumulated Depreciation Mobile Bay Pipeline $ 15.4 $ 8.3 $ 15.4 $ 7.9 NGLs pipelines and facilities 54.6 13.5 54.4 12.0 Offshore and other assets 13.0 10.9 13.0 10.6 Total $ 83.0 $ 32.7 $ 82.8 $ 30.5 Asset Impairments The Company recognized asset impairment charges of $0.4 million and $7.5 million for the years ended December 31, 2023 and 2022, and immaterial asset impairment charges for the year ended December 31, 2021. The charges recorded in 2022 were primarily due to an increase in the estimate of existing AROs related to retired assets. Base Gas Reclassification In September 2022, Gulf South, a wholly owned subsidiary of the Company, submitted an application with the FERC seeking authorization to reclassify 13.5 billion cubic feet of working gas as additional base gas. The reclassification was necessary to reflect changing operational needs and was supported, among other things, by an operational study of certain storage assets. In the first quarter 2023, the FERC comment period closed with no protests. As of March 31, 2023, as a result of the operational need for the base gas, Gulf South reclassified the carrying amount of approximately $47.8 million of natural gas to Property, Plant and Equipment, of which $40.9 million had been recorded in Gas Stored Underground within Current Assets , and $6.9 million had been recorded in Gas Stored Underground within Other Assets . The application was approved by the FERC in April 2023.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill As of December 31, 2023 and 2022, the Company had recorded on the Consolidated Balance Sheets $237.4 million of goodwill. The Company performed its annual goodwill impairment test for its two reporting units a s of November 30, 2023 and 2022. The results of the quantitative goodwill impairment test indicated that the fair value of the Company's reporting units exceeded their carrying amounts. The fair value measurement of the reporting units was derived based on judgments and assumptions the Company believes market participants would use in assessing the fair value of the reporting units. These judgments and assumptions included the valuation premise, use of a discounted cash flow model to estimate fair value under an income approach and inputs to the valuation model. The inputs included the Company's five-year financial plan operating results, including operating revenues, the long-term outlook for growth in natural gas and NGLs demand, measures of the risk-free rate, equity premium and systematic risk used in the calculation of the applied discount rate under the capital asset pricing model and views regarding future market conditions, among others. The reasonableness of fair value estimates under the income approach were supported by a market approach under which the Company applied earnings before interest, income taxes, depreciation and amortization (EBITDA) multiples derived from publicly-available information to each reporting unit's EBITDA. No impairment charges related to goodwill were recorded for any of the Company's reporting units during 2023, 2022 or 2021. Intangible Assets The following table contains information regarding the Company's intangible assets, which includes customer relationships acquired as part of its acquisitions (in millions): As of December 31, 2023 2022 Gross carrying amount (1) $ 93.3 $ 59.4 Accumulated amortization (21.3) (19.1) Net carrying amount $ 72.0 $ 40.3 (1) The increase in the gross carrying amount during the year ended December 31, 2023, is the result of the Bayou Ethane acquisition as discussed in Note 3. For the year ended December 31, 2023, amortization expense for intangible assets was $2.2 million and was $1.9 million for each of the years ended December 31, 2022 and 2021, and was recorded in Depreciation and amortization on the Consolidated Statements of Income. Amortization expense for the next five years and in total thereafter as of December 31, 2023, is expected to be as follows (in millions): 2024 $ 2.9 2025 3.0 2026 2.9 2027 2.9 2028 2.9 Thereafter 57.4 Total $ 72.0 The weighted-average remaining useful life of the Company's intangible assets as of December 31, 2023, was 25 years.

Asset Retirement Obligations

Asset Retirement Obligations	12 Months Ended
	Dec. 31, 2023
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligations	Asset Retirement Obligations The Company has identified and recorded legal obligations associated with the abandonment of certain pipeline and storage assets, brine ponds, offshore facilities and the abatement of asbestos, consisting of removal, transportation and disposal when removed from certain compressor stations and meter station buildings. Legal obligations exist for the main pipeline and certain other Company assets; however, the fair value of these obligations cannot be determined because the lives of the assets are indefinite. As a result, cash flows associated with retirement of the assets cannot be estimated with the degree of accuracy necessary to establish a liability for the obligations. The following table summarizes the aggregate carrying amount of the Company's ARO (in millions): As of December 31, 2023 2022 Balance at beginning of year $ 71.1 $ 64.9 Liabilities recorded 8.4 1.8 Liabilities settled (10.0) (6.3) Accretion expense 2.1 2.3 Revision of estimates 2.5 8.4 Balance at end of year 74.1 71.1 Less: Current portion of ARO (14.9) (17.2) Long-term ARO $ 59.2 $ 53.9 For the Company's operations where regulatory accounting is applicable, depreciation rates for PPE are comprised of two components. One component is based on economic service life (capital recovery) and the other is based on estimated costs of removal (as a component of negative salvage) which is collected in rates and does not represent an existing legal obligation. The Company has reflected $98.1 million and $93.2 million as of December 31, 2023 and 2022, on the Consolidated Balance Sheets as Provision for other asset retirement related to the estimated cost of removal collected in rates.

Regulatory Assets and Liabiliti

Regulatory Assets and Liabilities	12 Months Ended
	Dec. 31, 2023
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Assets and Liabilities	Regulatory Assets and Liabilities The amounts recorded as regulatory assets and liabilities on the Consolidated Balance Sheets as of December 31, 2023 and 2022, are summarized in the table below. The table also includes amounts related to unamortized debt issuance costs and unamortized discount on long-term debt, which while not regulatory assets and liabilities, are a critical component of the embedded cost of debt financing utilized in Texas Gas' rate proceedings. The tax effect of the equity component of AFUDC represents amounts recoverable from rate payers for the tax recorded in regulatory accounting. Certain amounts in the table are reflected as a negative, or a reduction, to be consistent with the regulatory books of account. The period of recovery for the regulatory assets included in rates varies from one As of December 31, 2023 2022 Regulatory Assets: Pension $ 8.1 $ 8.1 Tax effect of AFUDC equity 0.1 0.1 Other 0.5 0.5 Total regulatory assets $ 8.7 $ 8.7 Regulatory Liabilities: Cashout and fuel tracker $ 15.1 $ 55.1 Provision for other asset retirement 98.1 93.2 Unamortized debt issuance costs (1.0) (1.2) Unamortized discount on long-term debt (0.1) (0.1) Postretirement benefits other than pension 60.6 59.0 Total regulatory liabilities $ 172.7 $ 206.0

Financing

Financing	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Financing	Financing Long-Term Debt The following table presents all long-term debt issuances outstanding as of December 31, 2023 and 2022 (in millions): 2023 2022 Notes and Debentures: Boardwalk Pipelines 4.95% Notes due 2024 (Boardwalk Pipelines 2024 Notes) $ 600.0 $ 600.0 5.95% Notes due 2026 550.0 550.0 4.45% Notes due 2027 500.0 500.0 4.80% Notes due 2029 500.0 500.0 3.40% Notes due 2031 500.0 500.0 3.60% Notes due 2032 500.0 500.0 Texas Gas 7.25% Debentures due 2027 100.0 100.0 Total notes and debentures 3,250.0 3,250.0 Revolving Credit Facility: Boardwalk Pipelines 25.0 — Total revolving credit facility 25.0 — Finance lease obligation 3.6 4.5 3,278.6 3,254.5 Less: Unamortized debt discount (12.6) (16.0) Unamortized debt issuance costs (4.1) (5.1) Total Long-Term Debt and Finance Lease Obligation $ 3,261.9 $ 3,233.4 Maturities of the Company's long-term debt for the next five years and in total thereafter are as follows (in millions): 2024 $ 600.0 2025 — 2026 550.0 2027 600.0 2028 25.0 Thereafter 1,500.0 Total long-term debt $ 3,275.0 The Company has included the Boardwalk Pipelines 2024 Notes which mature in less than one year as long-term debt on its Consolidated Balance Sheets as of December 31, 2023. The Company has the intent and the ability to refinance the notes near or at their maturity through available capital resources including borrowing under the revolving credit facility or issuing debt securities. Notes and Debentures As of December 31, 2023 and 2022, the weighted-average interest rate of the Company's notes and debentures was 4.84%. The Company's notes and debentures are redeemable, in whole or in part, at the Company's option at any time, at a redemption price equal to the greater of 100% of the principal amount of the notes to be redeemed or a "make whole" redemption price based on the remaining scheduled payments of principal and interest discounted to the date of redemption at a rate equal to the U.S. Treasury rate plus 20 to 50 basis points depending upon the particular issue of notes, plus accrued and unpaid interest, if any. Other customary covenants apply, including those concerning events of default. The indentures governing the notes and debentures have restrictive covenants which provide that, with certain exceptions, neither the Company nor any of its subsidiaries may create, assume or suffer to exist any lien upon any property to secure any indebtedness unless the debentures and notes shall be equally and ratably secured. All of the Company's debt obligations are unsecured. As of December 31, 2023, the Company and its subsidiaries were in compliance with their debt covenants. Redemption of Notes On November 1, 2022, the Company retired the outstanding $300.0 million aggregate principal amount of Boardwalk Pipelines 3.375% notes due 2023 at a redemption price of 100% of the principal amount plus unpaid and accrued interest. The retirement was funded from available cash. Revolving Credit Facility The Company has a revolving credit facility that includes Boardwalk Pipelines, Texas Gas and Gulf South as borrowers (Borrowers) that is evidenced by a credit agreement. Interest is determined, at the Company's election, by reference to (a) the base rate which is the highest of (1) the prime rate, (2) the federal funds rate plus 0.50% and (3) the one month term Secured Overnight Financing Rate plus 1.00%, or (b) the term Secured Overnight Financing Rate plus a flat 10 basis point credit spread adjustment across all available interest periods. The credit agreement provides for a quarterly commitment fee charged on the average daily unused amount of the revolving credit facility ranging from 0.10% to 0.275% which is determined based on the individual Borrower's credit rating from time to time. The revolving credit facility has a borrowing capacity of $1.0 billion through May 27, 2027, and a borrowing capacity of $912.2 million from May 28, 2027, to May 26, 2028. The credit agreement contains various restrictive covenants and other usual and customary terms and conditions, including restrictions regarding the incurrence of additional debt, the sale of assets and sale-leaseback transactions. The financial covenants under the credit agreement require the Company and its subsidiaries to maintain, among other things, a ratio of total consolidated debt to consolidated EBITDA (as defined in the credit agreement) measured for the previous twelve months of not more than 5.0 to 1.0, or up to 5.5 to 1.0 for (i) the quarter in which the consummation of a qualified acquisition or series of acquisitions, where the purchase price exceeds $100.0 million over a rolling 12-month period and (ii) the three quarters following the qualified acquisition quarter. The Company and its subsidiaries were in compliance with all covenant requirements under the credit agreement as of December 31, 2023. Outstanding borrowings under the Company's revolving credit facility as of December 31, 2023, were $25.0 million, with a weighted-average interest rate of 6.71%. As of December 31, 2022, the Company had the entire $1.0 billion of borrowing capacity available under its revolving credit facility. As of February 2, 2024, the Company had $75.0 million of outstanding borrowings and $925.0 million of available borrowing capacity under its revolving credit facility. Cash Distributions Cash distributions the Company paid to BPHC and Boardwalk GP were $300.0 million for the year ended December 31, 2023, and $102.2 million for each of the years ended December 31, 2022 and 2021.

Employee Benefits

Employee Benefits	12 Months Ended
	Dec. 31, 2023
Retirement Benefits [Abstract]
Employee Benefits	Employee Benefits Retirement Plans Defined Benefit Retirement Plans (Retirement Plans) Texas Gas employees hired prior to November 1, 2006, are covered under a non-contributory, defined benefit pension plan (Pension Plan). The Texas Gas Supplemental Retirement Plan (SRP) provides pension benefits for the portion of an eligible employee's pension benefit under the Pension Plan that becomes subject to compensation limitations under the Internal Revenue Code. Collectively, the Company refers to the Pension Plan and the SRP as Retirement Plans. The Company uses a measurement date of December 31 for the Retirement Plans. As a result of the Texas Gas rate case settlement in 2006, the Company is required to fund the amount of annual net periodic pension cost associated with the Pension Plan, including a minimum of $3.0 million, which is the amount included in rates. In 2023 and 2022, the Company funded $4.9 million and $4.6 million to the Pension Plan and expects to fund an additional $3.0 million to the plan in 2024. In 2023, no SRP payments were made and in 2022 there were SRP payments made of $2.8 million. The Company recognizes in expense each year the actuarially determined amount of net periodic pension cost associated with the Retirement Plans, including a minimum amount of $3.0 million related to its Pension Plan, in accordance with the 2006 rate case settlement. Texas Gas is permitted to seek future rate recovery for amounts of annual Pension Plan costs in excess of $6.0 million and is precluded from seeking future recovery of annual Pension Plan costs between $3.0 million and $6.0 million. As a result, the Company would recognize a regulatory asset for amounts of annual Pension Plan costs in excess of $6.0 million and would reduce its regulatory asset to the extent that annual Pension Plan costs are less than $3.0 million. Annual Pension Plan costs between $3.0 million and $6.0 million will be charged to expense. Postretirement Benefits Other Than Pension Texas Gas provides postretirement medical benefits and life insurance to retired employees who were employed full time, hired prior to January 1, 1996, and have met certain other requirements. In 2023 and 2022, the Company contributed $0.1 million and $0.2 million to the PBOP plan. The PBOP plan is in an overfunded status; therefore, the Company does not expect to make any contributions to the plan in 2024. The Company does not anticipate that any plan assets will be returned to the Company during 2024. The Company uses a measurement date of December 31 for its PBOP plan. Projected Benefit Obligation, Fair Value of Assets and Funded Status The projected benefit obligation, fair value of assets, funded status and the amounts not yet recognized as components of net periodic pension and postretirement benefits cost for the Retirement Plans and PBOP at December 31, 2023 and 2022, were as follows (in millions): Retirement Plans PBOP For the Year Ended For the Year Ended December 31, 2023 2022 2023 2022 Change in benefit obligation: Benefit obligation at beginning of period $ 86.4 $ 109.1 $ 23.7 $ 30.6 Service cost 1.9 2.2 — — Interest cost 4.1 3.1 1.2 0.8 Plan participants' contributions — — 1.0 1.0 Actuarial loss/(gain) 4.0 (7.9) 2.3 (4.4) Benefits paid (0.5) (0.5) (4.8) (4.3) Settlements (7.9) (19.6) — — Benefit obligation at end of period $ 88.0 $ 86.4 $ 23.4 $ 23.7 Change in plan assets: Fair value of plan assets at beginning of period $ 77.6 $ 103.5 $ 81.2 $ 93.0 Actual return on plan assets 9.2 (13.2) 4.8 (8.6) Company's contribution 4.9 7.4 0.1 0.2 Plan participants' contributions — — 1.0 0.9 Benefits paid (0.5) (0.5) (4.8) (4.3) Settlements (7.9) (19.6) — — Fair value of plan assets at end of period $ 83.3 $ 77.6 $ 82.3 $ 81.2 Funded status $ (4.7) $ (8.8) $ 58.9 $ 57.5 Items not recognized as components of net periodic cost: Net actuarial loss $ 12.7 $ 16.9 $ 3.0 $ 3.2 At December 31, 2023 and 2022, the following aggregate information relates only to the underfunded plans (in millions): Retirement Plans For the Year Ended 2023 2022 Projected benefit obligation $ 88.0 $ 86.4 Accumulated benefit obligation 84.6 82.7 Fair value of plan assets 83.3 77.6 Components of Net Periodic Benefit Cost Components of net periodic benefit cost for both the Retirement Plans and PBOP for the years ended December 31, 2023, 2022 and 2021, were as follows (in millions): Retirement Plans PBOP For the Year Ended For the Year Ended 2023 2022 2021 2023 2022 2021 Service cost $ 1.9 $ 2.2 $ 2.6 $ — $ — $ 0.1 Interest cost 4.1 3.1 2.1 1.2 0.8 0.9 Expected return on plan assets (3.6) (5.3) (6.2) (2.4) (1.8) (2.7) Amortization of prior service cost 0.1 0.1 — — — — Amortization of unrecognized net loss 1.2 0.7 0.8 — — — Settlement charge 1.3 2.9 1.6 — — — Regulatory asset decrease — — 2.5 — — — Net periodic benefit cost $ 5.0 $ 3.7 $ 3.4 $ (1.2) $ (1.0) $ (1.7) Due to the Texas Gas rate case settlement in 2006, Texas Gas is permitted to seek future rate recovery for amounts of annual Pension Plan costs in excess of $6.0 million. Estimated Future Benefit Payments The following table shows benefit payments, which reflect expected future service, as appropriate, which are expected to be paid for both the Retirement Plans and PBOP (in millions): Retirement Plans PBOP 2024 $ 18.4 $ 2.0 2025 12.5 2.0 2026 10.7 1.9 2027 10.5 1.8 2028 8.4 1.7 2029-2033 22.6 7.2 Weighted-Average Assumptions Weighted-average assumptions used to determine benefit obligations for the years ended December 31, 2023 and 2022, were as follows: Retirement Plans PBOP For the Year Ended For the Year Ended 2023 2022 2023 2022 Pension SRP Pension SRP Discount rate 4.90 % 4.90 % 5.30 % 5.30 % 5.10 % 5.40 % Expected return on plan assets 5.00 % 5.00 % 5.00 % 5.00 % 3.25 % 2.99 % Rate of compensation increase 3.00%-3.50% 3.00%-3.50% 3.00%-4.50% 3.00%-4.50% — % — % Weighted-average assumptions used to determine net periodic benefit cost for the periods indicated were as follows: Retirement Plans PBOP For the Year Ended For the Year Ended 2023 2022 2021 2023 2022 2021 Pension SRP Pension SRP Pension SRP Discount rate (1) 4.90 % (1) (2) (1) 1.55 % 5.40 % 2.90 % 2.60 % Expected return on plan assets 5.00% 5.00 % 6.25% 6.25 % 6.50% 6.50 % 2.99 % 2.01 % 2.81 % Rate of compensation increase 3.00% - 4.50% 3.00% - 4.50% 3.00% 3.00 % 3.00% 3.00 % — % — % — % (1) Pension expense was remeasured quarterly in 2023, 2022 and 2021. The quarterly remeasurements for each quarter in 2023, 2022 and 2021 were as follows: Quarter 1: 5.35%, 3.00% and 2.05%; Quarter 2: 5.15%, 4.10% and 2.05%; Quarter 3: 5.45%, 4.65% and 1.95%; and Quarter 4: 4.90%, 5.30% and 2.30%. (2) SRP expense was remeasured with discount rates of 4.15% at June 30, 2022, and 5.30% at December 31, 2022, to reflect settlements. In determining the discount rate assumption, current market and liability information is utilized, including a discounted cash flow analysis of the pension and postretirement obligations. In particular, the basis for the discount rate selection was the yield on indices of highly rated fixed income debt securities with durations comparable to that of the Company's plan liabilities. The yield curve was applied to expected future retirement plan payments to adjust the discount rate to reflect the cash flow characteristics of the plans. The yield curves and indices evaluated in the selection of the discount rate were comprised of high-quality corporate bonds that are rated AA by an accepted rating agency. The expected long-term rate of return for plan assets is determined based on widely-accepted capital market principles, long-term return analysis for global fixed income and equity markets as well as the active total return oriented portfolio management style. Long-term trends are evaluated relative to market factors such as inflation, interest rates and fiscal and monetary policies, in order to assess the capital market assumptions as applied to the plan. Consideration of diversification needs and rebalancing is maintained. Pension Plan and PBOP Asset Allocation and Investment Strategy Pension Plan The Pension Plan assets are held in the Texas Gas Trust, established by Texas Gas, which manages and administers the Pension Plan. The Texas Gas Trust assets are measured at fair value. Equity securities are publicly traded securities which are valued using quoted market prices and are considered Level 1 investments under the fair value hierarchy. Short-term investments that are actively traded or have quoted prices, such as money market funds or treasury bills, are considered Level 1 investments. Fixed income mutual funds include highly liquid government securities and exchange traded bonds, valued using quoted market prices, and are considered Level 1 investments. Tax exempt securities are valued using a methodology based on information generated by market transactions involving identical or comparable assets, a discounted cash flow methodology or a combination of both when necessary. Common inputs for these securities, which are considered Level 2 investments, include pricing for similar securities, marketplace quotes, benchmark yields, spreads off benchmark yields, interest rates, U.S. Treasury or swap curves and other pricing models utilizing observable inputs. The following table sets forth, by level within the fair value hierarchy, a summary of the Texas Gas Trust's assets measured at fair value on a recurring basis at December 31, 2023 (in millions): Pension Plan Trust Assets Level 1 Level 2 Level 3 Total Equity securities $ 34.6 $ — $ — $ 34.6 Short-term investments 17.3 — — 17.3 Fixed income mutual funds 26.3 — — 26.3 Tax exempt securities — 5.1 — 5.1 Total assets $ 78.2 $ 5.1 $ — $ 83.3 The following table sets forth, by level within the fair value hierarchy, a summary of the Texas Gas Trust's assets measured at fair value on a recurring basis at December 31, 2022 (in millions): Pension Plan Trust Assets Level 1 Level 2 Level 3 Total Equity securities $ 17.5 $ — $ — $ 17.5 Short-term investments 28.3 — — 28.3 Fixed income mutual funds 31.8 — — 31.8 Total assets $ 77.6 $ — $ — $ 77.6 PBOP The PBOP plan assets are held in a trust and are measured at fair value. Short-term investments and other assets that are actively traded or have quoted prices, such as money market or mutual funds, are considered Level 1 investments. Fixed income securities, such as tax exempt securities and corporate bonds, and asset-backed securities are valued using a methodology based on information generated by market transactions involving identical or comparable assets, a discounted cash flow methodology or a combination of both when necessary. Common inputs for these securities, which are considered Level 2 investments, include pricing for similar securities, marketplace quotes, benchmark yields, spreads off benchmark yields, interest rates, U.S. Treasury or swap curves and other pricing models utilizing observable inputs. Other liabilities are primarily pending purchase transactions for certain investments that were executed on the last day of the year and not settled until the following year. The following table sets forth, by level within the fair value hierarchy, a summary of the PBOP trust investments measured at fair value on a recurring basis at December 31, 2023 (in millions): PBOP Trust Assets Level 1 Level 2 Level 3 Total Short-term investments $ 12.8 $ — $ — $ 12.8 Other assets 2.1 — — 2.1 Asset-backed securities — 0.8 — 0.8 Corporate bonds — 67.0 — 67.0 Tax exempt securities — 38.9 — 38.9 Total assets $ 14.9 $ 106.7 $ — $ 121.6 Other liabilities (39.3) — — (39.3) Total liabilities $ (39.3) $ — $ — $ (39.3) The following table sets forth, by level within the fair value hierarchy, a summary of the PBOP trust investments measured at fair value on a recurring basis at December 31, 2022 (in millions): PBOP Trust Assets Level 1 Level 2 Level 3 Total Short-term investments $ 2.2 $ — $ — $ 2.2 Other assets 1.8 — — 1.8 Asset-backed securities — 0.9 — 0.9 Corporate bonds — 54.9 — 54.9 Tax exempt securities — 34.4 — 34.4 Total assets $ 4.0 $ 90.2 $ — $ 94.2 Other liabilities (13.0) — — (13.0) Total liabilities $ (13.0) $ — $ — $ (13.0) Investment Strategy Pension Plan: The Company employs a total-return approach using a mix of equities and fixed income securities designed to maximize the long-term return on plan assets for a prudent level of risk and generate cash flows adequate to meet plan requirements. The intent of this strategy is to minimize plan expenses by generating investment returns that exceed the growth of the plan liabilities over the long run. Risk tolerance is established through careful consideration of the plan liabilities, plan funded status and corporate financial conditions. The target allocation of plan assets is 85% of the investment portfolio to equity and fixed income securities, with the remainder primarily invested in cash. Investment risk is monitored through annual liability measurements, periodic asset and liability studies and quarterly investment portfolio reviews. PBOP: The investment strategy for the PBOP assets is to reduce the volatility of plan investments while protecting the initial investment given the overfunded status of the plan. The Company uses a broad array of public and private assets and investment vehicles to achieve a return that is targeted to meet or exceed the plan blended benchmark indices. At December 31, 2023 and 2022, the investment portfolio contained a diversified blend of fixed income securities, such as tax exempt securities and corporate bonds, asset-backed securities, short-term securities and other assets. Defined Contribution Plan Texas Gas employees hired on or after November 1, 2006, and all other employees of the Company are provided retirement benefits under a defined contribution plan, which also provides 401(k) plan benefits to its participants. Costs related to the Company's defined contribution plan were $14.0 million, $12.7 million and $12.8 million for the years ended December 31, 2023, 2022 and 2021. Long-Term Incentive Compensation Plans The 2018 LTIP provides for grants of Performance Awards to selected employees of the Company. A Performance Award is a long-term incentive award with a stated target amount which is payable in cash, after adjustments, upon vesting based on certain specified performance criteria being met. In the case of retirement, any outstanding and unvested awards would become fully vested upon retirement and the Performance Awards will be paid at the original vesting date. In 2023 and 2022, the Company granted to certain employees $16.3 million and $12.5 million of Performance Awards. The Company recorded compensation expense of $14.2 million, $12.3 million and $12.7 million related to Performance Awards for the years ended December 31, 2023, 2022 and 2021, and had $9.8 million and $7.2 million of remaining unrecognized compensation expense related to Performance Awards as of December 31, 2023 and 2022.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company is not a taxable entity for federal income tax purposes. The following is a summary of the provision for income taxes for the years ended December 31, 2023, 2022 and 2021 (in millions): For the Year Ended December 31, 2023 2022 2021 Current expense: State $ 0.8 $ 0.8 $ 0.5 Deferred provision: State — — 0.2 Income taxes $ 0.8 $ 0.8 $ 0.7 The Company's tax years 2020 through 2023 remain subject to examination by the Internal Revenue Service and the states in which it operates. There were no differences between the provision at the statutory rate to the income tax provision at December 31, 2023, 2022 and 2021. As of December 31, 2023 and 2022, there were no significant deferred income tax assets or liabilities.

Credit Risk

Credit Risk	12 Months Ended
	Dec. 31, 2023
Risks and Uncertainties [Abstract]
Credit Risk	Credit Risk Major Customers For the years ended December 31, 2023, 2022 and 2021, no customer comprised 10% or more of the Company's operating revenues. Gas Loaned to Customers Natural gas price volatility can cause changes in credit risk related to gas and NGLs loaned to customers. As of December 31, 2023, the amount of gas owed to the Company's operating subsidiaries due to gas imbalances and gas loaned under PAL and certain firm service agreements was approximately 11.2 trillion British thermal units (TBtu). Assuming an average market price during December 2023 of $2.33 per million British thermal unit (MMBtu), the market value of that gas was approximately $26.1 million. As of December 31, 2022, the amount of gas owed to the Company's operating subsidiaries due to gas imbalances and gas loaned under PAL and certain firm service agreements was approximately 13.3 TBtu. Assuming an average market price during December 2022 of $5.33 per MMBtu, the market value of that gas was approximately $70.9 million. As of December 31, 2023 and 2022, there were no outstanding NGL imbalances owed to the Company's operating subsidiaries. If any significant customer should have credit or financial problems resulting in a delay or failure to pay for services provided or repay the gas owed to the operating subsidiaries, it could have a material adverse effect on the Company's financial condition, results of operations and cash flows.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2023
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Loews provides a variety of corporate services to the Company under services agreements, including risk management, finance and accounting, legal, tax and corporate development services, and charges the Company for allocated overheads. The Company incurred charges related to these services of $4.3 million, $3.7 million and $5.5 million for the years ended December 31, 2023, 2022 and 2021, which were recorded in Administrative and general on the Consolidated Statements of Income. Total distributions paid to BPHC and Boardwalk GP were $300.0 million for the year ended December 31, 2023, and $102.2 million for each of the years ended December 31, 2022 and 2021.

Supplemental Disclosure of Cash

Supplemental Disclosure of Cash Flow Information	12 Months Ended
	Dec. 31, 2023
Supplemental Cash Flow Elements [Abstract]
Supplemental Disclosure of Cash Flow Information	Supplemental Disclosure of Cash Flow Information (in millions): For the Year Ended December 31, 2023 2022 2021 Cash paid during the period for: Amounts included in the measurement of operating lease liabilities $ 4.9 $ 3.7 $ 4.1 Amounts included in the measurement of finance lease liability 1.1 1.1 1.1 Interest (net of amount capitalized) 147.3 156.3 152.2 Income taxes, net 0.7 0.6 0.5 Non-cash investing activities: Accounts payable and PPE 47.7 44.4 19.4 Right-of-use asset obtained in exchange for lease obligations 3.4 0.2 13.1 Gas stored underground and PPE 47.8 — —

Basis of Presentation and Sig_2

Basis of Presentation and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the Company's accounts and those of its wholly owned subsidiaries after elimination of intercompany transactions.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, disclosure of contingent assets and liabilities and the fair values of certain items. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, which form the basis for making judgments about the carrying amounts of assets and liabilities that are not readily apparent from other sources. Actual results could differ from such estimates.
Segment Information	Segment Information The Company operates in one reportable segment - the operation of interstate natural gas and NGLs pipeline systems and integrated storage facilities. This segment consists of interstate natural gas pipeline systems located in the Gulf Coast region, Oklahoma, Arkansas, Tennessee, Kentucky, Illinois, Indiana and Ohio and integrated natural gas storage facilities located in Indiana, Kentucky, Louisiana and Mississippi, and NGLs pipelines and storage facilities located in Louisiana and Texas.
Regulatory Accounting	Regulatory Accounting Most of the Company's natural gas pipeline subsidiaries and its interstate ethane transportation pipeline are regulated by the Federal Energy Regulatory Commission (FERC). When certain criteria are met, GAAP requires that certain rate-regulated entities account for and report assets and liabilities consistent with the economic effect of the manner in which independent third-party regulators establish rates (regulatory accounting). This basis of accounting is applicable to operations of the Company's Texas Gas subsidiary, which records certain costs and benefits as regulatory assets and liabilities in order to provide for recovery from or refunds to customers in future periods, but is not applicable to the operations associated with the Fayetteville and Greenville Laterals due to rates charged under negotiated rate agreements and a portion of Texas Gas' storage capacity due to the regulatory treatment associated with the rates charged for that capacity. The Company also applies regulatory accounting for its fuel trackers on Gulf South, under which the value of fuel received from customers paying the maximum tariff rate and the related value of fuel used in transportation are recorded to a regulatory asset or liability depending on whether Gulf South uses more fuel than it collects from customers or collects more fuel than it uses. Other than as described for Texas Gas and for the fuel trackers on Gulf South, regulatory accounting is not applicable to the Company's other FERC-regulated operations. The Company monitors the regulatory and competitive environment in which it operates to determine whether its regulatory assets continue to be probable of recovery. If the Company determines that all or a portion of its regulatory assets no longer meets the criteria for recognition as regulatory assets, that portion which is not recoverable will be written off, net of any regulatory liabilities.
Fair Value Measurements	Fair Value Measurements Fair value refers to an exit price that would be received to sell an asset or paid to transfer a liability in an orderly transaction in the principal market in which the reporting entity transacts based on the assumptions market participants would use when pricing the asset or liability assuming its highest and best use. A fair value hierarchy has been established that prioritizes the information used to develop those assumptions giving priority, from highest to lowest, to quoted prices in active markets for identical assets and liabilities (Level 1); observable inputs not included in Level 1, for example, quoted prices for similar assets and liabilities (Level 2); and unobservable data (Level 3), for example, a reporting entity's own internal data based on the best information available in the circumstances. The Company uses fair value measurements to account for business combinations, equity securities, asset retirement obligations (ARO), pension and postretirement benefits other than pension (PBOP) assets and any impairment charges.
Cash and Cash Equivalents	Cash and Cash Equivalents
Trade and Other Receivables	Trade and Other Receivables Trade and other receivables are stated at their historical carrying amount, net of allowances for doubtful accounts. The Company establishes an allowance for doubtful accounts under an expected credit loss model based on historical credit loss experience and specific facts and circumstances. Uncollectible receivables are written off when a settlement is reached for an amount that is less than the outstanding historical balance or a receivable amount is deemed otherwise unrealizable.
Gas Stored Underground and Gas Receivables and Payables	Gas Stored Underground and Gas Receivables and Payables Certain of the Company's operating subsidiaries have underground gas in storage which is utilized for system management and operational balancing, as well as for services including firm and interruptible storage associated with certain no-notice and parking and lending (PAL) services. Gas stored underground includes the historical cost of natural gas volumes owned by the operating subsidiaries, at times reduced by certain operational encroachments upon that gas. The operating subsidiaries provide storage services whereby they store natural gas or NGLs on behalf of customers and also periodically hold customer gas under PAL services. Since the customers retain title to the gas held by the Company in providing these services, the Company does not record the related gas on the Consolidated Balance Sheets . Certain of the Company's operating subsidiaries also periodically lend gas and NGLs to customers. In the course of providing transportation and storage services to customers, the operating subsidiaries may receive different quantities of gas from shippers and operators than the quantities delivered on behalf of those shippers and operators. This results in transportation and exchange gas receivables and payables, commonly known as imbalances, which are primarily settled in cash or the receipt or delivery of gas in the future. Settlement of imbalances requires agreement between the pipelines and shippers or operators as to allocations of volumes to specific transportation contracts and timing of delivery of gas based on operational conditions. The receivables and payables are valued at market price for operations where regulatory accounting is not applicable and are valued at the historical value of gas in storage for operations where regulatory accounting is applicable.
Materials and Supplies	Materials and Supplies Materials and supplies are carried at average cost and are included in Other Assets
Property, Plant and Equipment and Repair and Maintenance Costs	Property, Plant and Equipment and Repair and Maintenance Costs PPE is recorded at its original cost of construction or fair value of assets purchased. Construction costs and expenditures for major renewals and improvements which extend the lives of the respective assets are capitalized. Construction work in progress is included in the financial statements as a component of PPE. Repair and maintenance costs are expensed as incurred.
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill represents the excess of the cost of an acquisition over the fair value of the net identifiable assets acquired and liabilities assumed. Goodwill is tested for impairment at the reporting unit level at least annually, as of November 30, or more frequently when events occur and circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount. A reporting entity may perform an optional qualitative assessment on an annual basis to determine whether events occurred or circumstances changed that would more likely than not reduce the fair value of a reporting unit below its carrying amount. If an initial qualitative assessment identifies that it is more likely than not that the fair value of a reporting unit is less than its carrying amount, or the optional qualitative assessment is not performed, a quantitative analysis is performed. The quantitative goodwill impairment test is performed by calculating the fair value of the reporting unit and comparing it to the reporting unit's carrying amount. If the fair value of a reporting unit exceeds its carrying amount, goodwill of the reporting unit is not impaired. However, if the carrying amount of a reporting unit exceeds its fair value, an impairment loss is recognized in an amount equal to that excess, limited to the total amount of goodwill recorded on the reporting unit. Intangible assets are those assets which provide future economic benefit but have no physical substance. The Company recorded intangible assets for customer relationships obtained through its acquisitions. The customer relationships, which are included in Other Assets on the Consolidated Balance Sheets, have a finite life and are being amortized over their estimated useful lives.
Impairment of Long-lived Assets (including Tangible and Definite-lived Intangible Assets)	Impairment of Long-lived Assets (including Tangible and Definite-lived Intangible Assets) The Company evaluates its long-lived and intangible assets for impairment when, in management's judgment, events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. When such a determination has been made, management's estimate of undiscounted future cash flows attributable to the remaining economic useful life of the asset (or asset group) is compared to the carrying amount of the asset (or asset group) to determine whether an impairment has occurred. If an impairment of the carrying amount has occurred, the amount of impairment recognized in the financial statements is determined by estimating the fair value of the assets (or asset group) and recording a loss to the extent that the carrying amount exceeds the estimated fair value.
Capitalized Interest and Allowance for Funds Used During Construction (AFUDC)	Capitalized Interest and Allowance for Funds Used During Construction (AFUDC) The Company records capitalized interest, which represents the cost of borrowed funds used to finance construction activities for operations where regulatory accounting is not applicable. The Company records AFUDC, which represents the cost of funds, including equity funds, applicable to regulated natural gas transmission plant under construction as permitted by FERC regulatory practices, in connection with the Company's operations where regulatory accounting is applicable. Capitalized interest and the allowance for borrowed funds used during construction are recognized as a reduction to Interest expense and the allowance for equity funds used during construction is included in Miscellaneous other income, net
Income Taxes	Income Taxes
Asset Retirement Obligations	Asset Retirement Obligations The accounting requirements for existing legal obligations associated with the future retirement of long-lived assets require entities to record the fair value of a liability for an ARO in the period during which the liability is incurred. The liability is initially recognized at fair value and is increased with the passage of time as accretion expense is recorded, until the liability is ultimately settled. The accretion expense is included within Operation and maintenance
Environmental Liabilities	Environmental Liabilities
Defined Benefit Plans	Defined Benefit Plans The Company maintains postretirement benefit plans for certain employees. The Company funds these plans through periodic contributions which are invested until the benefits are paid out to the participants, and records an asset or liability based on the overfunded or underfunded status of the plan. The net benefit costs of the plans are recorded on the Consolidated Statements of Income. Any deferred amounts related to unrecognized gains and losses or changes in actuarial assumptions are recorded as either a regulatory asset or liability or recorded as a component of accumulated other comprehensive income until those gains or losses are recognized on the Consolidated Statements of Income.
Long-Term Compensation	Long-Term Compensation The Company provides performance awards (Performance Awards) to certain of its employees under its 2018 Long-Term Incentive Plan (2018 LTIP). A Performance Award is a long-term incentive award with a stated target amount which is payable in cash, after certain adjustments, upon vesting based on certain specified performance criteria being met.
Partner Capital Accounts	Partner Capital Accounts For purposes of maintaining capital accounts, items of income and loss of the Company are allocated among the partners each period, or portion thereof, in accordance with the partnership agreement, based on their respective ownership interests.
Leases	Leases Operating lease right-of-use assets and lease liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. The discount rate used to determine the commencement date present value of lease payments is typically the Company's secured borrowing rate, as the implicit rate of most of the Company's leases is not readily determinable. The Company has elected not to record any leases with terms of twelve months or less on the Consolidated Balance Sheets.
Revenue Recognition and Contract Balances	Revenue Recognition Nature of Contracts The Company primarily earns revenues from contracts with customers by providing transportation and storage services for natural gas and NGLs on a firm and interruptible basis and providing ethane supply and transportation services for industrial customers in Louisiana and Texas. The Company also provides interruptible natural gas PAL services. The Company's customers choose, based upon their particular needs, the applicable mix of services depending upon availability of pipeline and storage capacity, the price of services and the volume and timing of customer requirements. The maximum applicable rates that may be charged by the majority of the Company's operating subsidiaries are established through the FERC's cost-based rate-making process; however, the FERC also allows for discounted or negotiated rates as an alternative to cost-based rates. Under the FERC regulations, certain revenues that the Company's subsidiaries collect may be subject to possible refunds to customers. Accordingly, during a rate case, estimated refund liabilities are recorded considering regulatory proceedings, advice of counsel and estimated risk-adjusted total exposure, as well as other factors. The Company's service contracts can range from one to twenty years although the Company may enter into shorter- or longer-term contracts, and services are invoiced monthly with payment from the customer generally expected within ten Firm Service Contracts : The Company offers firm services to its customers. The Company's customers can reserve a specific amount of pipeline capacity at specified receipt and delivery points on the Company's pipeline system (transportation service) or can reserve a specific amount of storage capacity at specified injection and withdrawal points at the Company's storage facilities (storage service). The Company accounts for firm services as a single promise to stand ready each month of the contract term to provide the committed capacity for either transportation or storage services when needed by the customer, which represents a series of distinct monthly services that are substantially the same with the same pattern of transfer to the customer. Although several activities may be required to provide the firm service, the individual activities do not represent distinct performance obligations because all of the activities must be performed in combination in order for the Company to provide the firm service. The transaction price for firm service contracts is comprised of a fixed fee based on the quantity of capacity reserved, regardless of use (capacity reservation fee), plus variable fees in the form of a usage fee paid on the volume of commodity actually transported or injected and withdrawn from storage. Both the fixed and usage fees are allocated to the single performance obligation of providing transportation or storage service and recognized over time based upon the output measure of time as the Company completes its stand-ready obligation to provide contracted capacity and the customer receives and consumes the benefit of the reserved capacity, which corresponds with the transfer of control to the customer. The fixed fee is recognized ratably over the contract term, representative of the proportion of the committed stand-ready capacity obligation that has been fulfilled to date, and the usage fee is recognized upon satisfaction of each distinct monthly performance obligation, consistent with the allocation objective and based upon the level of effort required to satisfy the stand-ready obligation in a given month. Capacity reservation revenues derived from a firm service contract are generally consistent during the contract term, but can be higher in winter periods than the rest of the year based upon seasonal rates. Interruptible Service Contracts : In providing interruptible services to customers, the Company agrees to transport or store natural gas or NGLs for a customer when capacity is available. The Company does not account for interruptible services with a customer as a contract until the customer nominates for service and the Company accepts the nomination based upon available pipeline or storage capacity or product availability because there are no enforceable rights and obligations until that time. The nomination and acceptance process is a daily activity and acceptance is granted based upon priority of service and availability of capacity and products. Upon acceptance, the Company accounts for interruptible services similarly to its firm services. The transaction price for interruptible service contracts is comprised of a variable fee in the form of a usage fee paid on the volume of commodity actually transported or injected and withdrawn from storage. The transaction price is allocated to the single performance obligation of providing interruptible service. Interruptible service revenues for natural gas transportation and storage are generally recognized over time based on the output measure of volume transported or stored when services are rendered upon the successful allocation of the services provided to the customer's account, which best depicts the transfer of control to the customer and satisfaction of the promised service. Interruptible services are recognized in the month services are provided because the Company has a right to consideration from customers in amounts that correspond directly to the value that the customer receives from the Company's performance. The rates charged may vary on a daily, monthly or seasonal basis. Minimum Volume Commitment (MVC) Contracts : Certain of the Company's transportation, storage or ethane supply contracts require customers to transport, store or purchase a minimum volume of commodity over a specified time period. If a customer fails to meet its MVC for the specified time period, the customer is obligated to pay a contractually-determined deficiency fee based upon the shortfall between the actual volumes transported, stored or purchased and the MVC for that period. MVC contracts are generally similar in nature to a firm service contract where the performance obligation is a stand-ready obligation that is a series of distinct services that are substantially the same with the same pattern of transfer to the customer. The transaction price for a MVC is a fee for the volume of commodity actually transported, stored or delivered, which is allocated to each distinct monthly performance obligation, consistent with the allocation objective and based upon the level of effort required to satisfy the obligation of the transacted activities in a given month. Revenues associated with transportation and storage services are generally recognized over time based on the output measure of volume transported or stored and revenues associated with ethane supply are generally recognized at a point in time based on barrels delivered, with the recognition of the deficiency fee in the period when it is known the customer cannot make up the deficient volume in the specified period. Other: Certain ethane supply contracts include a stated volume that the Company supplies to customers, and any volume requested above the stated volume is based on product availability. Revenues for these ethane supply contracts are generally recognized at a point in time when each barrel is transferred to the customer because the customer is able to direct the use of, and obtain substantially all of the remaining benefits from, the product at that time. Periodically, the Company may also enter into contracts with customers for the sale of natural gas or NGLs. The Company recognizes revenues for these transactions at the point in time of the physical sale of the commodity, which corresponds with the transfer of control of the commodity to the customer and the consideration is measured as the stated sales price in the contract. Contract Balances The Company records contract assets primarily related to performance obligations completed but not billed, or partially billed, as of the reporting date. The Company records contract liabilities, or deferred revenue, when payment is received in advance of satisfying its performance obligations.

Basis of Presentation and Sig_3

Basis of Presentation and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Summary of Capitalized Interest and Allowance for Borrowed Funds	The following table summarizes capitalized interest and the allowance for borrowed funds and allowance for equity funds used during construction (in millions): For the Year Ended 2023 2022 2021 Capitalized interest and allowance for borrowed funds used during construction $ 3.6 $ 2.2 $ 3.8 Allowance for equity funds used during construction 5.7 6.2 7.9

Acquisition (Tables)

Acquisition (Tables)	12 Months Ended
	Dec. 31, 2023
Business Combination and Asset Acquisition [Abstract]
Final Fair Values of the Assets Acquired and Liabilities Assumed	The final fair values of the assets acquired and liabilities assumed as of September 29, 2023, the acquisition date, were as follows (in millions): Current assets $ 51.8 Property, plant and equipment 296.2 Customer-based intangibles (1) 33.9 Noncurrent assets 0.5 Total assets acquired 382.4 Current liabilities 26.7 Noncurrent liabilities 0.7 Total liabilities assumed 27.4 Net assets acquired $ 355.0 (1) Customer-based intangibles have a weighted-average useful life of 35 years and are recorded in Other Assets.
Pro Forma Information	The following unaudited pro forma results of operations are presented as if the acquisition occurred on January 1, 2022. Such results are not necessarily indicative of future results. These pro forma results also do not reflect any cost savings, operating synergies or revenue enhancements that the Company may achieve or the costs necessary to achieve those objectives (in millions): Pro Forma For the Year Ended December 31, 2023 2022 Operating revenue (1)(2) $ 1,962.8 $ 2,253.4 Net income (2) 393.8 357.4 (1) Bayou Ethane provides ethane supply services, which result in ethane sales and purchases being presented on a gross basis in the Consolidated Statements of Income. (2) The average ethane price of $0.25 per gallon for the year ended December 31, 2023, was lower as compared to $0.48 per gallon for the comparable period for 2022, which resulted in higher revenues in the 2022 period.

Revenues (Tables)

Revenues (Tables)	12 Months Ended
	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table presents the Company's revenues disaggregated by type of service (in millions): For the Year Ended December 31, 2023 2022 2021 Revenues from Contracts with Customers Firm Service (1)(3) $ 1,489.7 $ 1,311.9 $ 1,247.5 Interruptible Service 51.6 56.2 32.0 Other revenues (3) 40.2 29.9 26.1 Total Revenues from Contracts with Customers 1,581.5 1,398.0 1,305.6 Other operating revenues (2)(3) 36.2 34.0 34.5 Total Operating Revenues $ 1,617.7 $ 1,432.0 $ 1,340.1 (1) Revenues earned from contracts with MVCs are included in firm service given the stand-ready nature of the performance obligation and the guaranteed nature of the fees over the contract term. (2) Other operating revenues include certain revenues earned from operating leases, pipeline management fees and other activities that are not considered central and ongoing major business operations of the Company and do not represent revenues earned from contracts with customers. (3) Revenues attributable to Bayou Ethane were $74.9 million in firm service, $25.4 million in other revenues and $1.2 million in other operating revenues for the year ended December 31, 2023.
Contract Liabilities	Significant changes in the contract liability balances during the year ended December 31, 2023, were as follows (in millions): Contract Liabilities Balance as of December 31, 2022 (1) $ 23.0 Revenues recognized that were included in the contract liability (3.9) Increases due to cash received, excluding amounts recognized as 1.8 Other 0.5 Balance as of December 31, 2023 (1) $ 21.4 (1) As of December 31, 2023 and 2022, $3.5 million and $3.6 million were recorded in Other Current Liabilities (current portion), and $17.9 million and $19.4 million were recorded in Other Liabilities (noncurrent portion). Significant changes in the contract liability balances during the year ended December 31, 2022, were as follows (in millions): Contract Liabilities Balance as of December 31, 2021 (1) $ 19.2 Revenues recognized that were included in the contract liability (5.1) Increases due to cash received, excluding amounts recognized as 8.9 Balance as of December 31, 2022 (1) $ 23.0 (1) As of December 31, 2022 and 2021, $3.6 million was recorded in Other Current Liabilities (current portion) and $19.4 million and $15.6 million were recorded in Other Liabilities (noncurrent portion).
Remaining Performance Obligation	The following table includes estimated operating revenues expected to be recognized in the future related to agreements that contain performance obligations that were unsatisfied as of December 31, 2023. The amounts presented primarily consist of fixed fees or MVCs which are typically recognized over time as the performance obligation is satisfied, in accordance with firm service contracts or guaranteed minimum fees associated with the performance obligation that are satisfied at a point in time under certain ethane supply contracts. For the Company's customers that are charged maximum tariff rates related to its FERC-regulated operating subsidiaries, the amounts below reflect the current tariff rate for such services for the term of the agreements; however, the tariff rates may be subject to future adjustment. The Company has elected to exclude the following from the table: (a) unsatisfied performance obligations from usage fees associated with its firm services because of the variable nature of such services; (b) unsatisfied performance obligations from the ethane commodity indexed portion of the ethane supply contracts because of the variable nature of ethane prices, and (c) consideration in contracts that is recognized in revenue as invoiced, such as for interruptible services. The estimated revenues reflected in the table may include estimated revenues that are anticipated under executed precedent transportation agreements for projects that are subject to regulatory approvals. In millions 2024 2025 Thereafter Total Estimated revenues from contracts with customers from unsatisfied performance obligations as of December 31, 2023 $ 1,362.0 $ 1,250.0 $ 6,840.5 $ 9,452.5 Operating revenues which are fixed and 28.0 27.5 163.5 219.0 Total projected operating revenues under committed firm agreements as of December 31, 2023 $ 1,390.0 $ 1,277.5 $ 7,004.0 $ 9,671.5

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Components of Lease Cost	The components of lease cost were as follows (in millions): For the Year Ended December 31, 2023 2022 2021 Operating lease cost $ 3.8 $ 3.8 $ 4.0 Short-term lease cost 4.7 3.1 2.9 Finance lease cost: Amortization of right-of-use asset 0.7 0.7 0.7 Interest on lease liability 0.3 0.3 0.4 Total lease cost $ 9.5 $ 7.9 $ 8.0
Schedule of Supplemental Balance Sheet Information Related to Leases	The following provides supplemental balance sheet information related to the Company's leases: As of December 31, 2023 2022 Right-of-use assets (in millions) Operating leases (recorded in Other Assets ) $ 18.9 $ 18.7 Finance lease (recorded in Property, Plant and Equipment ) 3.2 4.0 Lease liabilities (in millions) Operating leases (recorded in Other Liabilities , current and non-current) 19.6 20.6 Finance lease (recorded in Other Current Liabilities and Long-term debt and finance lease obligation ) 4.5 5.4 Weighted-average remaining lease term (years) Operating leases 9.9 10.4 Finance lease 4.6 5.6 Weighted-average discount rate Operating leases 3.20 % 2.86 % Finance lease 5.89 % 5.89 %
Maturity of Operating Lease Liabilities	The table below presents the maturities of lease liabilities (in millions): As of December 31, 2023 Operating Finance 2024 $ 3.7 $ 1.1 2025 2.6 1.1 2026 1.9 1.1 2027 1.3 1.1 2028 0.3 0.7 Thereafter 13.3 — Total 23.1 5.1 Less: discount (3.5) (0.6) Total lease liabilities $ 19.6 $ 4.5
Maturity of Finance Lease Liabilities	The table below presents the maturities of lease liabilities (in millions): As of December 31, 2023 Operating Finance 2024 $ 3.7 $ 1.1 2025 2.6 1.1 2026 1.9 1.1 2027 1.3 1.1 2028 0.3 0.7 Thereafter 13.3 — Total 23.1 5.1 Less: discount (3.5) (0.6) Total lease liabilities $ 19.6 $ 4.5

Commitment and Contingencies (T

Commitment and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Schedule of Pipeline Capacity and Storage Agreements Future Commitments	The table below presents the future commitments related to these agreements as of December 31, 2023 (in millions): 2024 $ 7.9 2025 8.0 2026 8.0 2027 3.2 2028 0.1 Thereafter — Total $ 27.2

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value, by Balance Sheet Grouping	The carrying amounts and estimated fair values of the Company's financial assets and liabilities which were not recorded at fair value on the Consolidated Balance Sheets as of December 31, 2023 and 2022, were as follows (in millions): As of December 31, 2023 Estimated Fair Value Financial Assets Carrying Amount Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 20.1 $ 20.1 $ — $ — $ 20.1 Financial Liabilities Long-term debt $ 3,262.4 (1) $ — $ 3,155.3 $ — $ 3,155.3 (1) The carrying amount of long-term debt excluded a $3.6 million long-term finance lease obligation and $4.1 million of unamortized debt issuance costs. As of December 31, 2022 Estimated Fair Value Financial Assets Carrying Amount Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 215.6 $ 215.6 $ — $ — $ 215.6 Financial Liabilities Long-term debt $ 3,234.0 (1) $ — $ 3,041.4 $ — $ 3,041.4 (1) The carrying amount of long-term debt excluded a $4.5 million long-term finance lease obligation and $5.1 million of unamortized debt issuance costs.

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Schedule of Property, Plant and Equipment	The following table presents the Company's PPE as of December 31, 2023 and 2022 (in millions): Category 2023 2023 Weighted-Average Useful Lives (Years) 2022 2022 Weighted-Average Useful Lives (Years) Depreciable plant: Transmission $ 11,405.4 38 $ 10,913.0 38 Storage 951.3 39 921.9 38 Gathering 106.1 24 111.1 24 General, intangibles and other 535.4 20 473.0 21 Total utility depreciable plant 12,998.2 37 12,419.0 37 Non-depreciable: Construction work in progress 287.2 187.6 Storage 197.5 151.6 Land 46.6 46.1 Total non-depreciable assets 531.3 385.3 Total PPE, gross 13,529.5 12,804.3 Less: accumulated depreciation and amortization 4,672.9 4,288.3 Total PPE, net $ 8,856.6 $ 8,516.0
Schedule of Gross PPE Investments and Related Accumulated Depreciation	The following table presents the gross PPE investment and related accumulated depreciation for the Company's undivided interests as of December 31, 2023 and 2022 (in millions): 2023 2022 Gross PPE Accumulated Depreciation Gross PPE Accumulated Depreciation Mobile Bay Pipeline $ 15.4 $ 8.3 $ 15.4 $ 7.9 NGLs pipelines and facilities 54.6 13.5 54.4 12.0 Offshore and other assets 13.0 10.9 13.0 10.6 Total $ 83.0 $ 32.7 $ 82.8 $ 30.5

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Finite-Lived Intangible Assets	The following table contains information regarding the Company's intangible assets, which includes customer relationships acquired as part of its acquisitions (in millions): As of December 31, 2023 2022 Gross carrying amount (1) $ 93.3 $ 59.4 Accumulated amortization (21.3) (19.1) Net carrying amount $ 72.0 $ 40.3 (1) The increase in the gross carrying amount during the year ended December 31, 2023, is the result of the Bayou Ethane acquisition as discussed in Note 3.
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	Amortization expense for the next five years and in total thereafter as of December 31, 2023, is expected to be as follows (in millions): 2024 $ 2.9 2025 3.0 2026 2.9 2027 2.9 2028 2.9 Thereafter 57.4 Total $ 72.0

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	12 Months Ended
	Dec. 31, 2023
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligation	The following table summarizes the aggregate carrying amount of the Company's ARO (in millions): As of December 31, 2023 2022 Balance at beginning of year $ 71.1 $ 64.9 Liabilities recorded 8.4 1.8 Liabilities settled (10.0) (6.3) Accretion expense 2.1 2.3 Revision of estimates 2.5 8.4 Balance at end of year 74.1 71.1 Less: Current portion of ARO (14.9) (17.2) Long-term ARO $ 59.2 $ 53.9

Regulatory Assets and Liabili_2

Regulatory Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2023
Regulatory Assets and Liabilities Disclosure [Abstract]
Schedule of Regulatory Assets	The amounts recorded as regulatory assets and liabilities on the Consolidated Balance Sheets as of December 31, 2023 and 2022, are summarized in the table below. The table also includes amounts related to unamortized debt issuance costs and unamortized discount on long-term debt, which while not regulatory assets and liabilities, are a critical component of the embedded cost of debt financing utilized in Texas Gas' rate proceedings. The tax effect of the equity component of AFUDC represents amounts recoverable from rate payers for the tax recorded in regulatory accounting. Certain amounts in the table are reflected as a negative, or a reduction, to be consistent with the regulatory books of account. The period of recovery for the regulatory assets included in rates varies from one As of December 31, 2023 2022 Regulatory Assets: Pension $ 8.1 $ 8.1 Tax effect of AFUDC equity 0.1 0.1 Other 0.5 0.5 Total regulatory assets $ 8.7 $ 8.7 Regulatory Liabilities: Cashout and fuel tracker $ 15.1 $ 55.1 Provision for other asset retirement 98.1 93.2 Unamortized debt issuance costs (1.0) (1.2) Unamortized discount on long-term debt (0.1) (0.1) Postretirement benefits other than pension 60.6 59.0 Total regulatory liabilities $ 172.7 $ 206.0
Schedule of Regulatory Liabilities	The amounts recorded as regulatory assets and liabilities on the Consolidated Balance Sheets as of December 31, 2023 and 2022, are summarized in the table below. The table also includes amounts related to unamortized debt issuance costs and unamortized discount on long-term debt, which while not regulatory assets and liabilities, are a critical component of the embedded cost of debt financing utilized in Texas Gas' rate proceedings. The tax effect of the equity component of AFUDC represents amounts recoverable from rate payers for the tax recorded in regulatory accounting. Certain amounts in the table are reflected as a negative, or a reduction, to be consistent with the regulatory books of account. The period of recovery for the regulatory assets included in rates varies from one As of December 31, 2023 2022 Regulatory Assets: Pension $ 8.1 $ 8.1 Tax effect of AFUDC equity 0.1 0.1 Other 0.5 0.5 Total regulatory assets $ 8.7 $ 8.7 Regulatory Liabilities: Cashout and fuel tracker $ 15.1 $ 55.1 Provision for other asset retirement 98.1 93.2 Unamortized debt issuance costs (1.0) (1.2) Unamortized discount on long-term debt (0.1) (0.1) Postretirement benefits other than pension 60.6 59.0 Total regulatory liabilities $ 172.7 $ 206.0

Financing (Tables)

Financing (Tables)	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments and Debt Issuances	The following table presents all long-term debt issuances outstanding as of December 31, 2023 and 2022 (in millions): 2023 2022 Notes and Debentures: Boardwalk Pipelines 4.95% Notes due 2024 (Boardwalk Pipelines 2024 Notes) $ 600.0 $ 600.0 5.95% Notes due 2026 550.0 550.0 4.45% Notes due 2027 500.0 500.0 4.80% Notes due 2029 500.0 500.0 3.40% Notes due 2031 500.0 500.0 3.60% Notes due 2032 500.0 500.0 Texas Gas 7.25% Debentures due 2027 100.0 100.0 Total notes and debentures 3,250.0 3,250.0 Revolving Credit Facility: Boardwalk Pipelines 25.0 — Total revolving credit facility 25.0 — Finance lease obligation 3.6 4.5 3,278.6 3,254.5 Less: Unamortized debt discount (12.6) (16.0) Unamortized debt issuance costs (4.1) (5.1) Total Long-Term Debt and Finance Lease Obligation $ 3,261.9 $ 3,233.4
Schedule of Maturities of Long-term Debt	Maturities of the Company's long-term debt for the next five years and in total thereafter are as follows (in millions): 2024 $ 600.0 2025 — 2026 550.0 2027 600.0 2028 25.0 Thereafter 1,500.0 Total long-term debt $ 3,275.0

Employee Benefits (Tables)

Employee Benefits (Tables)	12 Months Ended
	Dec. 31, 2023
Retirement Benefits [Abstract]
Schedule of Projected Benefit Obligation, Fair Value of Assets, Funded Status and the Amounts Not Yet Recognized As Components of Net Periodic Pension and Postretirement Benefits Cost	Projected Benefit Obligation, Fair Value of Assets and Funded Status The projected benefit obligation, fair value of assets, funded status and the amounts not yet recognized as components of net periodic pension and postretirement benefits cost for the Retirement Plans and PBOP at December 31, 2023 and 2022, were as follows (in millions): Retirement Plans PBOP For the Year Ended For the Year Ended December 31, 2023 2022 2023 2022 Change in benefit obligation: Benefit obligation at beginning of period $ 86.4 $ 109.1 $ 23.7 $ 30.6 Service cost 1.9 2.2 — — Interest cost 4.1 3.1 1.2 0.8 Plan participants' contributions — — 1.0 1.0 Actuarial loss/(gain) 4.0 (7.9) 2.3 (4.4) Benefits paid (0.5) (0.5) (4.8) (4.3) Settlements (7.9) (19.6) — — Benefit obligation at end of period $ 88.0 $ 86.4 $ 23.4 $ 23.7 Change in plan assets: Fair value of plan assets at beginning of period $ 77.6 $ 103.5 $ 81.2 $ 93.0 Actual return on plan assets 9.2 (13.2) 4.8 (8.6) Company's contribution 4.9 7.4 0.1 0.2 Plan participants' contributions — — 1.0 0.9 Benefits paid (0.5) (0.5) (4.8) (4.3) Settlements (7.9) (19.6) — — Fair value of plan assets at end of period $ 83.3 $ 77.6 $ 82.3 $ 81.2 Funded status $ (4.7) $ (8.8) $ 58.9 $ 57.5 Items not recognized as components of net periodic cost: Net actuarial loss $ 12.7 $ 16.9 $ 3.0 $ 3.2
Schedule of Accumulated Benefit Obligations in Excess of Fair Value of Plan Assets	At December 31, 2023 and 2022, the following aggregate information relates only to the underfunded plans (in millions): Retirement Plans For the Year Ended 2023 2022 Projected benefit obligation $ 88.0 $ 86.4 Accumulated benefit obligation 84.6 82.7 Fair value of plan assets 83.3 77.6
Schedule of Net Periodic Benefit Cost	Components of net periodic benefit cost for both the Retirement Plans and PBOP for the years ended December 31, 2023, 2022 and 2021, were as follows (in millions): Retirement Plans PBOP For the Year Ended For the Year Ended 2023 2022 2021 2023 2022 2021 Service cost $ 1.9 $ 2.2 $ 2.6 $ — $ — $ 0.1 Interest cost 4.1 3.1 2.1 1.2 0.8 0.9 Expected return on plan assets (3.6) (5.3) (6.2) (2.4) (1.8) (2.7) Amortization of prior service cost 0.1 0.1 — — — — Amortization of unrecognized net loss 1.2 0.7 0.8 — — — Settlement charge 1.3 2.9 1.6 — — — Regulatory asset decrease — — 2.5 — — — Net periodic benefit cost $ 5.0 $ 3.7 $ 3.4 $ (1.2) $ (1.0) $ (1.7)
Schedule of Expected Benefit Payments	The following table shows benefit payments, which reflect expected future service, as appropriate, which are expected to be paid for both the Retirement Plans and PBOP (in millions): Retirement Plans PBOP 2024 $ 18.4 $ 2.0 2025 12.5 2.0 2026 10.7 1.9 2027 10.5 1.8 2028 8.4 1.7 2029-2033 22.6 7.2
Schedule of Weighted-Average Assumptions Used to Determine Benefit Obligations and Net Periodic Benefit Cost	Weighted-average assumptions used to determine benefit obligations for the years ended December 31, 2023 and 2022, were as follows: Retirement Plans PBOP For the Year Ended For the Year Ended 2023 2022 2023 2022 Pension SRP Pension SRP Discount rate 4.90 % 4.90 % 5.30 % 5.30 % 5.10 % 5.40 % Expected return on plan assets 5.00 % 5.00 % 5.00 % 5.00 % 3.25 % 2.99 % Rate of compensation increase 3.00%-3.50% 3.00%-3.50% 3.00%-4.50% 3.00%-4.50% — % — % Weighted-average assumptions used to determine net periodic benefit cost for the periods indicated were as follows: Retirement Plans PBOP For the Year Ended For the Year Ended 2023 2022 2021 2023 2022 2021 Pension SRP Pension SRP Pension SRP Discount rate (1) 4.90 % (1) (2) (1) 1.55 % 5.40 % 2.90 % 2.60 % Expected return on plan assets 5.00% 5.00 % 6.25% 6.25 % 6.50% 6.50 % 2.99 % 2.01 % 2.81 % Rate of compensation increase 3.00% - 4.50% 3.00% - 4.50% 3.00% 3.00 % 3.00% 3.00 % — % — % — % (1) Pension expense was remeasured quarterly in 2023, 2022 and 2021. The quarterly remeasurements for each quarter in 2023, 2022 and 2021 were as follows: Quarter 1: 5.35%, 3.00% and 2.05%; Quarter 2: 5.15%, 4.10% and 2.05%; Quarter 3: 5.45%, 4.65% and 1.95%; and Quarter 4: 4.90%, 5.30% and 2.30%. (2) SRP expense was remeasured with discount rates of 4.15% at June 30, 2022, and 5.30% at December 31, 2022, to reflect settlements.
Schedule of Fair Value of Plan Assets	The following table sets forth, by level within the fair value hierarchy, a summary of the Texas Gas Trust's assets measured at fair value on a recurring basis at December 31, 2023 (in millions): Pension Plan Trust Assets Level 1 Level 2 Level 3 Total Equity securities $ 34.6 $ — $ — $ 34.6 Short-term investments 17.3 — — 17.3 Fixed income mutual funds 26.3 — — 26.3 Tax exempt securities — 5.1 — 5.1 Total assets $ 78.2 $ 5.1 $ — $ 83.3 The following table sets forth, by level within the fair value hierarchy, a summary of the Texas Gas Trust's assets measured at fair value on a recurring basis at December 31, 2022 (in millions): Pension Plan Trust Assets Level 1 Level 2 Level 3 Total Equity securities $ 17.5 $ — $ — $ 17.5 Short-term investments 28.3 — — 28.3 Fixed income mutual funds 31.8 — — 31.8 Total assets $ 77.6 $ — $ — $ 77.6 The following table sets forth, by level within the fair value hierarchy, a summary of the PBOP trust investments measured at fair value on a recurring basis at December 31, 2023 (in millions): PBOP Trust Assets Level 1 Level 2 Level 3 Total Short-term investments $ 12.8 $ — $ — $ 12.8 Other assets 2.1 — — 2.1 Asset-backed securities — 0.8 — 0.8 Corporate bonds — 67.0 — 67.0 Tax exempt securities — 38.9 — 38.9 Total assets $ 14.9 $ 106.7 $ — $ 121.6 Other liabilities (39.3) — — (39.3) Total liabilities $ (39.3) $ — $ — $ (39.3) The following table sets forth, by level within the fair value hierarchy, a summary of the PBOP trust investments measured at fair value on a recurring basis at December 31, 2022 (in millions): PBOP Trust Assets Level 1 Level 2 Level 3 Total Short-term investments $ 2.2 $ — $ — $ 2.2 Other assets 1.8 — — 1.8 Asset-backed securities — 0.9 — 0.9 Corporate bonds — 54.9 — 54.9 Tax exempt securities — 34.4 — 34.4 Total assets $ 4.0 $ 90.2 $ — $ 94.2 Other liabilities (13.0) — — (13.0) Total liabilities $ (13.0) $ — $ — $ (13.0)

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense	The following is a summary of the provision for income taxes for the years ended December 31, 2023, 2022 and 2021 (in millions): For the Year Ended December 31, 2023 2022 2021 Current expense: State $ 0.8 $ 0.8 $ 0.5 Deferred provision: State — — 0.2 Income taxes $ 0.8 $ 0.8 $ 0.7

Supplemental Disclosure of Ca_2

Supplemental Disclosure of Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2023
Supplemental Cash Flow Elements [Abstract]
Schedule of Cash Flow, Supplemental Disclosures	Supplemental Disclosure of Cash Flow Information (in millions): For the Year Ended December 31, 2023 2022 2021 Cash paid during the period for: Amounts included in the measurement of operating lease liabilities $ 4.9 $ 3.7 $ 4.1 Amounts included in the measurement of finance lease liability 1.1 1.1 1.1 Interest (net of amount capitalized) 147.3 156.3 152.2 Income taxes, net 0.7 0.6 0.5 Non-cash investing activities: Accounts payable and PPE 47.7 44.4 19.4 Right-of-use asset obtained in exchange for lease obligations 3.4 0.2 13.1 Gas stored underground and PPE 47.8 — —

Corporate Structure (Details)

Corporate Structure (Details)	Dec. 31, 2023
Boardwalk Pipelines Holding Corp. (BPHC) | Boardwalk Pipeline Partners, LP
Noncontrolling Interest [Line Items]
Ownership percentage	100%

Basis of Presentation and Sig_4

Basis of Presentation and Significant Accounting Policies - Narrative (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) reportable_segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Revenue Recognition [Line Items]
Other revenue, decrease	$ (69,500,000)	$ (62,900,000)	$ (65,400,000)
Product sales, increase	100,300,000	11,100,000	11,700,000
Fuel and transportation expense, decrease	(26,300,000)	(22,400,000)	(22,100,000)
Product costs, increase	$ 87,800,000	1,000,000	0
Number of reportable segments | reportable_segment	1
Restricted cash	$ 0	0
Materials and supplies	38,100,000	34,300,000
Aggregate basis difference in net assets for financial and income tax purposes	$ 5,600,000,000
Minimum
Revenue Recognition [Line Items]
Depreciation range for PPE related to operations for which regulatory accounting does not apply	3 years
Depreciation range for PPE related to operations for which regulatory accounting is applicable	5 years
Service contract duration (years)	one
Expected payment of invoiced services (days)	10 days
Maximum
Revenue Recognition [Line Items]
Depreciation range for PPE related to operations for which regulatory accounting does not apply	35 years
Depreciation range for PPE related to operations for which regulatory accounting is applicable	62 years
Service contract duration (years)	twenty years
Expected payment of invoiced services (days)	30 days
Revision of Prior Period, Reclassification, Adjustment
Revenue Recognition [Line Items]
Other revenue, decrease		11,100,000	11,700,000
Product sales, increase		11,100,000	11,700,000
Fuel and transportation expense, decrease		1,000,000	0
Product costs, increase		$ 1,000,000	$ 0

Basis of Presentation and Sig_5

Basis of Presentation and Significant Accounting Policies - Summary Capitalized Interest and Allowances (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accounting Policies [Abstract]
Capitalized interest and allowance for borrowed funds used during construction	$ 3.6	$ 2.2	$ 3.8
Allowance for equity funds used during construction	$ 5.7	$ 6.2	$ 7.9

Acquisition - Narrative (Detail

Acquisition - Narrative (Details) - Bayou Ethane - Boardwalk Resources Company, LLC $ in Millions		12 Months Ended
	Sep. 29, 2023 USD ($) pipeline mi	Dec. 31, 2023 USD ($)
Business Acquisition [Line Items]
Percentage of voting interests acquired	100%
Payments to acquire business	$ 355
Pipeline system owned, number of miles | mi	380
Number of pipelines owned | pipeline	2
Pipelines owned, number of miles | mi	15
Acquisition, operating revenue contribution		$ 101.5
Acquisition, net income contribution		$ 5.5

Acquisition - Recognized Assets

Acquisition - Recognized Assets Acquired and Liabilities Assumed (Details) - Bayou Ethane - Boardwalk Resources Company, LLC $ in Millions	Sep. 29, 2023 USD ($)
Business Acquisition [Line Items]
Current assets	$ 51.8
Property, plant and equipment	296.2
Customer-based intangibles	33.9
Noncurrent assets	0.5
Total assets acquired	382.4
Current liabilities	26.7
Noncurrent liabilities	0.7
Total liabilities assumed	27.4
Net assets acquired	$ 355
Intangibles, weighted-average useful life	35 years

Acquisition - Pro Forma Financi

Acquisition - Pro Forma Financial Information (unaudited) (Details) - Bayou Ethane - Boardwalk Resources Company, LLC $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) $ / gal	Dec. 31, 2022 USD ($) $ / gal
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Operating revenue	$ 1,962.8	$ 2,253.4
Net income	$ 393.8	$ 357.4
Average ethane price (in dollars per gallon) | $ / gal	0.25	0.48

Revenues - Narrative (Details)

Revenues - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) reportable_segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Revenue from Contract with Customer [Abstract]
Number of reportable segments | reportable_segment	1
Receivables from contracts with customers	$ 204.6	$ 148.4
Contract assets from contracts with a customer	6.2	3.3
Contract liabilities from contracts with customers	$ 21.4	$ 23	$ 19.2

Revenues - Disaggregation of Re

Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	$ 1,581.5	$ 1,398	$ 1,305.6
Other operating revenues	36.2	34	34.5
Total operating revenues	1,617.7	1,432	1,340.1
Firm Service
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	1,489.7	1,311.9	1,247.5
Firm Service | Bayou Ethane | Boardwalk Resources Company, LLC
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	74.9
Interruptible Service
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	51.6	56.2	32
Interruptible Service | Bayou Ethane | Boardwalk Resources Company, LLC
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	25.4
Other revenues
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	40.2	$ 29.9	$ 26.1
Other revenues | Bayou Ethane | Boardwalk Resources Company, LLC
Disaggregation of Revenue [Line Items]
Total Revenues from Contracts with Customers	$ 1.2

Revenues - Contract Liability B

Revenues - Contract Liability Balance Activity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Contract With Customer, Liability [Roll Forward]
Beginning Balance	$ 23	$ 19.2
Revenues recognized that were included in the contract liability balances at the beginning of the period	(3.9)	(5.1)
Increases due to cash received, excluding amounts recognized as revenues during the period	1.8	8.9
Other	0.5
Ending Balance	21.4	23
Contract with customer, liability, current	3.5	3.6	$ 3.6
Contract with customer, liability, noncurrent	$ 17.9	$ 19.4	$ 15.6

Revenues - Performance Obligati

Revenues - Performance Obligations (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Estimated revenues from contracts with customers from unsatisfied performance obligations as of December 31, 2023	$ 9,452.5
Operating revenues which are fixed and determinable (operating leases)	219
Total projected operating revenues under committed firm agreements as of December 31, 2023	$ 9,671.5
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, period	1 year
Estimated revenues from contracts with customers from unsatisfied performance obligations as of December 31, 2023	$ 1,362
Operating revenues which are fixed and determinable (operating leases)	28
Total projected operating revenues under committed firm agreements as of December 31, 2023	$ 1,390
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, period	1 year
Estimated revenues from contracts with customers from unsatisfied performance obligations as of December 31, 2023	$ 1,250
Operating revenues which are fixed and determinable (operating leases)	27.5
Total projected operating revenues under committed firm agreements as of December 31, 2023	$ 1,277.5
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, period
Estimated revenues from contracts with customers from unsatisfied performance obligations as of December 31, 2023	$ 6,840.5
Operating revenues which are fixed and determinable (operating leases)	163.5
Total projected operating revenues under committed firm agreements as of December 31, 2023	$ 7,004

Leases - Narrative (Details)

Leases - Narrative (Details)	12 Months Ended
	Dec. 31, 2023 lease_renewal
Leases [Abstract]
Finance lease, term	15 years
Finance lease, number of renewal options	2
Finance lease, renewal term	20 years

Leases - Lease Cost (Details)

Leases - Lease Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
Operating lease cost	$ 3.8	$ 3.8	$ 4
Short-term lease cost	4.7	3.1	2.9
Finance lease cost:
Amortization of right-of-use asset	0.7	0.7	0.7
Interest on lease liability	0.3	0.3	0.4
Total lease cost	$ 9.5	$ 7.9	$ 8

Leases - Supplemental Balance S

Leases - Supplemental Balance Sheet Information Related to Leases (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Right-of-use assets (in millions)
Operating leases (recorded in Other Assets)	$ 18.9	$ 18.7
Right-of-use assets operating leases, statement of financial position	Other	Other
Finance lease (recorded in Property, Plant and Equipment)	$ 3.2	$ 4
Right-of-use assets finance lease, statement of financial position	Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization	Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization
Lease liabilities (in millions)
Operating leases (recorded in Other Liabilities, current and non-current)	$ 19.6	$ 20.6
Operating lease, liability, current, statement of financial position	Other current liabilities	Other current liabilities
Operating lease, liability, noncurrent, statement of financial position	Other	Other
Finance lease (recorded in Other Current Liabilities and Long-term debt and finance lease obligation)	$ 4.5	$ 5.4
Finance lease liability, statement of financial position	Long-term debt and finance lease obligation, Other current liabilities	Long-term debt and finance lease obligation, Other current liabilities
Weighted-average remaining lease term (years)
Operating leases	9 years 10 months 24 days	10 years 4 months 24 days
Finance lease	4 years 7 months 6 days	5 years 7 months 6 days
Weighted-average discount rate
Operating leases	3.20%	2.86%
Finance lease	5.89%	5.89%

Leases - Maturities of Operatin

Leases - Maturities of Operating and Finance Lease Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Operating Leases
2024	$ 3.7
2025	2.6
2026	1.9
2027	1.3
2028	0.3
Thereafter	13.3
Total	23.1
Less: discount	(3.5)
Total lease liabilities	19.6	$ 20.6
Finance Lease
2024	1.1
2025	1.1
2026	1.1
2027	1.1
2028	0.7
Thereafter	0
Total	5.1
Less: discount	(0.6)
Total lease liabilities	$ 4.5	$ 5.4

Commitments and Contingencies -

Commitments and Contingencies - Legal Proceedings and Settlements (Details) $ in Millions	Nov. 12, 2021 USD ($)	Aug. 05, 2021 case
City of New Orleans Litigation | Pending Litigation
Loss Contingencies [Line Items]
Number of cases | case		2
Boardwalk GP, LP
Loss Contingencies [Line Items]
Legal damages awarded to other party (approximately)	$ 690
Pre-judgment interest awarded to other party (approximately)	$ 166

Commitments and Contingencies_2

Commitments and Contingencies - Environmental and Safety Matters (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Accrual for environmental loss contingencies	$ 10.1	$ 3
Environmental Loss Contingency Statement Of Financial Position Extensible Enumeration Not Disclosed Flag	$ 10.1	3
Number of years the related expenditures are expected to cover assessment and remediation costs (in years)	30 years
Accrued environmental loss contingencies, current	$ 6.7	$ 1.3
Accrued Environmental Loss Contingency, Current, Statement of Financial Position	Other current liabilities	Other current liabilities
Accrued environmental loss contingencies, noncurrent	$ 3.4	$ 1.7
Accrued Environmental Loss Contingency, Noncurrent, Statement of Financial Position	Other	Other

Commitments and Contingencies_3

Commitments and Contingencies - Commitments for Construction (Details) $ in Millions	Dec. 31, 2023 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Purchase commitment, expected to be settled in the next twelve months	$ 134.2

Commitments and Contingencies_4

Commitments and Contingencies - Pipeline Capacity and Storage Agreements, Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pipeline Capacity and Storage Agreements
Unrecorded Unconditional Purchase Obligation [Line Items]
Expenses related to pipeline capacity and storage agreements	$ 5.8	$ 3.2	$ 7.7

Commitments and Contingencies_5

Commitments and Contingencies - Pipeline Capacity and Storage Agreements Future Commitments (Details) - Pipeline Capacity and Storage Agreements $ in Millions	Dec. 31, 2023 USD ($)
Unrecorded Unconditional Purchase Obligation [Line Items]
2024	$ 7.9
2025	8
2026	8
2027	3.2
2028	0.1
Thereafter	0
Total	$ 27.2

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - Fair Value, Measurements, Recurring - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities, fair value, recurring basis	$ 0	$ 0
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities, fair value, recurring basis	$ 2,300,000	$ 3,000,000

Fair Value Measurements - Finan

Fair Value Measurements - Financial Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Financial Assets
Cash and cash equivalents	$ 20.1	$ 215.6
Financial Liabilities
Long-term debt	3,155.3	3,041.4
Long-term finance lease obligation	3.6	4.5
Unsecured Debt
Financial Liabilities
Unamortized debt issuance costs	4.1	5.1
Carrying Amount
Financial Assets
Cash and cash equivalents	20.1	215.6
Financial Liabilities
Long-term debt	3,262.4	3,234
Estimated Fair Value | Level 1
Financial Assets
Cash and cash equivalents	20.1	215.6
Financial Liabilities
Long-term debt	0	0
Estimated Fair Value | Level 2
Financial Assets
Cash and cash equivalents	0	0
Financial Liabilities
Long-term debt	3,155.3	3,041.4
Estimated Fair Value | Level 3
Financial Assets
Cash and cash equivalents	0	0
Financial Liabilities
Long-term debt	$ 0	$ 0

Property, Plant and Equipment -

Property, Plant and Equipment - Class and Useful Life (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Depreciation expense for PPE	$ 406.5	$ 390.4	$ 364.4
Property, Plant and Equipment [Line Items]
Total PPE, gross	13,529.5	12,804.3
Less:  accumulated depreciation and amortization	4,672.9	4,288.3
Property, plant and equipment, net	8,856.6	8,516
Depreciable plant:
Property, Plant and Equipment [Line Items]
Total PPE, gross	$ 12,998.2	$ 12,419
Weighted-Average Useful Lives	37 years	37 years
Transmission
Property, Plant and Equipment [Line Items]
Total PPE, excluding finance lease	$ 11,405.4	$ 10,913
Weighted-Average Useful Lives	38 years	38 years
Storage
Property, Plant and Equipment [Line Items]
Total PPE, excluding finance lease	$ 951.3	$ 921.9
Weighted-Average Useful Lives	39 years	38 years
Gathering
Property, Plant and Equipment [Line Items]
Total PPE, excluding finance lease	$ 106.1	$ 111.1
Weighted-Average Useful Lives	24 years	24 years
General, intangibles and other
Property, Plant and Equipment [Line Items]
Total PPE, gross	$ 535.4	$ 473
Weighted-Average Useful Lives	20 years	21 years
Non-depreciable:
Property, Plant and Equipment [Line Items]
Total PPE, excluding finance lease	$ 531.3	$ 385.3
Construction work in progress
Property, Plant and Equipment [Line Items]
Total PPE, excluding finance lease	287.2	187.6
Total PPE, gross	287.2	187.6
Storage
Property, Plant and Equipment [Line Items]
Total PPE, excluding finance lease	197.5	151.6
Land
Property, Plant and Equipment [Line Items]
Total PPE, excluding finance lease	$ 46.6	$ 46.1

Property, Plant and Equipment_2

Property, Plant and Equipment - Undivided Interests (Details)	Dec. 31, 2023 well
Mobile Bay Pipeline
Undivided Interest Property [Line Items]
Undivided interest in pipeline	64%
NGLs pipelines and facilities
Undivided Interest Property [Line Items]
Undivided interest in ethylene wells	83%
Undivided interest, number of ethylene wells	2

Property, Plant and Equipment_3

Property, Plant and Equipment - Undivided Interests Gross PPE and Accumulated Depreciation (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Undivided Interest Property [Line Items]
Gross PPE Investment	$ 83	$ 82.8
Accumulated Depreciation	32.7	30.5
Mobile Bay Pipeline
Undivided Interest Property [Line Items]
Gross PPE Investment	15.4	15.4
Accumulated Depreciation	8.3	7.9
NGLs pipelines and facilities
Undivided Interest Property [Line Items]
Gross PPE Investment	54.6	54.4
Accumulated Depreciation	13.5	12
Offshore and other assets
Undivided Interest Property [Line Items]
Gross PPE Investment	13	13
Accumulated Depreciation	$ 10.9	$ 10.6

Property, Plant and Equipment_4

Property, Plant and Equipment - Asset Impairments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Asset impairment charges	$ 0.4	$ 7.5	$ 0

Property, Plant and Equipment_5

Property, Plant and Equipment - Base Gas Reclassification (Details) $ in Millions, Bcf in Billions	Mar. 31, 2023 USD ($)	Sep. 30, 2022 Bcf
Property, Plant and Equipment [Abstract]
Natural gas requested to be reclassified as base gas measurement | Bcf		13.5
Natural gas carrying value reclassified to PPE, total	$ 47.8
Natural gas carrying value reclassified to PPE, current	40.9
Natural gas carrying value reclassified to PPE, noncurrent	$ 6.9

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Goodwill (Details)			12 Months Ended
	Nov. 30, 2023 report	Nov. 30, 2022 report	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill			$ 237,400,000	$ 237,400,000
Number of reporting units | report	2	2
Goodwill impairment loss			$ 0	$ 0	$ 0

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Goodwill and Intangible Assets Disclosure [Abstract]
Gross carrying amount	$ 93.3	$ 59.4
Accumulated amortization	(21.3)	(19.1)
Net carrying amount	$ 72	$ 40.3

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Amortization Expense, Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible assets, amortization expense	$ 2.2	$ 1.9	$ 1.9
Intangible assets, weighted-average useful life	25 years

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets - Amortization Expense (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Goodwill and Intangible Assets Disclosure [Abstract]
2024	$ 2.9
2025	3
2026	2.9
2027	2.9
2028	2.9
Thereafter	57.4
Net carrying amount	$ 72	$ 40.3

Asset Retirement Obligations -

Asset Retirement Obligations - Aggregate Carrying Amount (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	$ 71.1	$ 64.9
Liabilities recorded	8.4	1.8
Liabilities settled	(10)	(6.3)
Accretion expense	2.1	2.3
Revision of estimates	2.5	8.4
Balance at end of year	74.1	71.1
Less:  Current portion of ARO	(14.9)	(17.2)
Long-term ARO	$ 59.2	$ 53.9

Asset Retirement Obligations _2

Asset Retirement Obligations - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Asset Retirement Obligation Disclosure [Abstract]
Provision for other asset retirement	$ 98.1	$ 93.2

Regulatory Assets and Liabili_3

Regulatory Assets and Liabilities - Narrative (Details)	12 Months Ended
	Dec. 31, 2023
Regulatory Assets and Liabilities Disclosure [Abstract]
Period of recovery-minimum (in years)	1 year
Period of recovery-maximum (in years)	18 years

Regulatory Assets and Liabili_4

Regulatory Assets and Liabilities - Regulatory Assets (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Regulatory Assets [Line Items]
Total regulatory assets	$ 8.7	$ 8.7
Pension
Regulatory Assets [Line Items]
Total regulatory assets	8.1	8.1
Tax effect of AFUDC equity
Regulatory Assets [Line Items]
Total regulatory assets	0.1	0.1
Other
Regulatory Assets [Line Items]
Total regulatory assets	$ 0.5	$ 0.5

Regulatory Assets and Liabili_5

Regulatory Assets and Liabilities - Regulatory Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Regulatory Liabilities [Line Items]
Total regulatory liabilities	$ 172.7	$ 206
Total regulatory assets	(8.7)	(8.7)
Cashout and fuel tracker
Regulatory Liabilities [Line Items]
Total regulatory liabilities	15.1	55.1
Provision for other asset retirement
Regulatory Liabilities [Line Items]
Total regulatory liabilities	98.1	93.2
Postretirement benefits other than pension
Regulatory Liabilities [Line Items]
Total regulatory liabilities	60.6	59
Unamortized debt issuance costs
Regulatory Liabilities [Line Items]
Total regulatory assets	(1)	(1.2)
Unamortized discount on long-term debt
Regulatory Liabilities [Line Items]
Total regulatory assets	$ (0.1)	$ (0.1)

Financing - Long-Term Debt (Det

Financing - Long-Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Instruments [Abstract]
Finance lease obligation	$ 3.6	$ 4.5
Total notes and debentures, revolving credit facility and Finance lease obligation	3,278.6	3,254.5
Less:
Total Long-Term Debt and Finance Lease Obligation	3,261.9	3,233.4
Unsecured Debt
Debt Instruments [Abstract]
Total notes and debentures	3,275
Less:
Unamortized debt discount	(12.6)	(16)
Unamortized debt issuance costs	$ (4.1)	$ (5.1)
Unsecured Debt | Boardwalk Pipelines 4.95% Notes Due 2024
Debt Instruments [Abstract]
Debt, interest rate	4.95%	4.95%
Total notes and debentures	$ 600	$ 600
Unsecured Debt | Boardwalk Pipelines 5.95% Notes Due 2026
Debt Instruments [Abstract]
Debt, interest rate	5.95%	5.95%
Total notes and debentures	$ 550	$ 550
Unsecured Debt | Boardwalk Pipelines 4.45% Notes Due 2027
Debt Instruments [Abstract]
Debt, interest rate	4.45%	4.45%
Total notes and debentures	$ 500	$ 500
Unsecured Debt | Boardwalk Pipelines 4.8% Notes Due 2029
Debt Instruments [Abstract]
Debt, interest rate	4.80%	4.80%
Total notes and debentures	$ 500	$ 500
Unsecured Debt | Boardwalk Pipelines 3.40% Notes Due 2031
Debt Instruments [Abstract]
Debt, interest rate	3.40%	3.40%
Total notes and debentures	$ 500	$ 500
Unsecured Debt | Boardwalk Pipelines 3.60% Notes Due 2032
Debt Instruments [Abstract]
Debt, interest rate	3.60%	3.60%
Total notes and debentures	$ 500	$ 500
Unsecured Debt | Texas Gas 7.25% Debentures Due 2027
Debt Instruments [Abstract]
Debt, interest rate	7.25%	7.25%
Total notes and debentures	$ 100	$ 100
Unsecured Debt | Total Notes and Debentures
Debt Instruments [Abstract]
Total notes and debentures	3,250	3,250
Line of Credit
Debt Instruments [Abstract]
Total revolving credit facility	25	0
Line of Credit | Boardwalk Pipelines Revolving Credit Facility
Debt Instruments [Abstract]
Total revolving credit facility	$ 25	$ 0

Financing - Long-Term Debt Matu

Financing - Long-Term Debt Maturities (Details) - Unsecured Debt $ in Millions	Dec. 31, 2023 USD ($)
Debt Instrument [Line Items]
2024	$ 600
2025	0
2026	550
2027	600
2028	25
Thereafter	1,500
Total long-term debt	$ 3,275

Financing - Narrative (Details)

Financing - Narrative (Details)		12 Months Ended
	Nov. 01, 2022 USD ($)	Dec. 31, 2023 USD ($) qtr	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Feb. 02, 2024 USD ($)
Debt Instrument [Line Items]
Repayments of borrowings from long-term debt		$ 0	$ 600,000,000	$ 0
Cash dividends paid to parent company		$ 300,000,000	$ 102,200,000	$ 102,200,000
Unsecured Debt
Debt Instrument [Line Items]
Weighted-average interest rate		4.84%	4.84%
Redemption price, percentage		100%
Unsecured Debt | US Treasury Rate | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate		0.20%
Unsecured Debt | US Treasury Rate | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate		0.50%
Unsecured Debt | Boardwalk Pipelines 3.375% Notes Due 2023
Debt Instrument [Line Items]
Redemption price, percentage	100%
Repayments of borrowings from long-term debt	$ 300,000,000
Debt, interest rate	3.375%
Line of Credit
Debt Instrument [Line Items]
Weighted-average interest rate		6.71%
Maximum ratio of debt to EBITDA		5
Maximum ratio of debt to EBITDA, after acquisition		5.5
Qualified acquisition purchase price target, over rolling 12-month period (exceeds)		$ 100,000,000
Qualified acquisition purchase price target, covenant, number of quarters following qualified acquisition quarter | qtr		3
Line of credit, outstanding borrowings		$ 25,000,000	$ 0
Line of credit, available borrowing capacity			$ 1,000,000,000
Line of Credit | Subsequent Event
Debt Instrument [Line Items]
Line of credit, outstanding borrowings					$ 75,000,000
Line of credit, available borrowing capacity					$ 925,000,000
Line of Credit | Minimum
Debt Instrument [Line Items]
Commitment fee. percentage		0.10%
Line of Credit | Maximum
Debt Instrument [Line Items]
Commitment fee. percentage		0.275%
Line of Credit | Federal Funds Effective Swap Rate
Debt Instrument [Line Items]
Basis spread on variable rate		0.50%
Line of Credit | SOFR Overnight Index Swap Rate
Debt Instrument [Line Items]
Basis spread on variable rate		1%
Line of Credit | Amendment No. 4 Credit Agreement - 2022 | SOFR Overnight Index Swap Rate
Debt Instrument [Line Items]
Basis spread on variable rate		0.10%
Line of Credit | Amendment No. 3 Credit Agreement - 2021
Debt Instrument [Line Items]
Borrowing capacity		$ 1,000,000,000
Line of Credit | Amendment No. 5 Credit Agreement - 2023
Debt Instrument [Line Items]
Borrowing capacity		$ 912,200,000

Employee Benefits - Narrative (

Employee Benefits - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined contribution plan, cost	$ 14,000,000	$ 12,700,000	$ 12,800,000
Pension
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contribution to defined benefit pension plan	4,900,000	4,600,000
Expected future contributions	3,000,000
Minimum amount of recognized expense each year associated with retirement plan	3,000,000
Future rate recovery amount	$ 6,000,000
Pension | Equity securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target allocation percentage	85%
Pension | Fixed income mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target allocation percentage	85%
Pension | Minimum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Required amount of funding of periodic pension cost	$ 3,000,000
Precluded future recovery of annual pension costs	3,000,000
Recognition of regulatory assets (in excess of)	6,000,000
Pension plan costs charged to expense	3,000,000
Pension | Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Precluded future recovery of annual pension costs	6,000,000
Reduction of regulatory assets (less than)	3,000,000
Pension plan costs charged to expense	6,000,000
SRP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contribution to defined benefit pension plan	0	2,800,000
PBOP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contribution to defined benefit pension plan	100,000	$ 200,000
Expected future contributions	$ 0

Employee Benefits - Projected B

Employee Benefits - Projected Benefit Obligation, Fair Value of Assets, Funded Status and the Amounts Not Yet Recognized As Components of Net Periodic Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Retirement Plans
Change in benefit obligation:
Benefit obligation at beginning of period	$ 86.4	$ 109.1
Service cost	1.9	2.2	$ 2.6
Interest cost	4.1	3.1	2.1
Plan participants' contributions	0	0
Actuarial loss/(gain)	4	(7.9)
Benefits paid	(0.5)	(0.5)
Settlements	(7.9)	(19.6)
Benefit obligation at end of period	88	86.4	109.1
Change in plan assets:
Fair value of plan assets at beginning of period	77.6	103.5
Actual return on plan assets	9.2	(13.2)
Company's contribution	4.9	7.4
Plan participants' contributions	0	0
Benefits paid	(0.5)	(0.5)
Settlements	(7.9)	(19.6)
Fair value of plan assets at end of period	83.3	77.6	103.5
Funded status	(4.7)	(8.8)
Items not recognized as components of net periodic cost:
Net actuarial loss	12.7	16.9
PBOP
Change in benefit obligation:
Benefit obligation at beginning of period	23.7	30.6
Service cost	0	0	0.1
Interest cost	1.2	0.8	0.9
Plan participants' contributions	1	1
Actuarial loss/(gain)	2.3	(4.4)
Benefits paid	(4.8)	(4.3)
Settlements	0	0
Benefit obligation at end of period	23.4	23.7	30.6
Change in plan assets:
Fair value of plan assets at beginning of period	81.2	93
Actual return on plan assets	4.8	(8.6)
Company's contribution	0.1	0.2
Plan participants' contributions	1	0.9
Benefits paid	(4.8)	(4.3)
Settlements	0	0
Fair value of plan assets at end of period	82.3	81.2	$ 93
Funded status	58.9	57.5
Items not recognized as components of net periodic cost:
Net actuarial loss	$ 3	$ 3.2

Employee Benefits - Aggregate I

Employee Benefits - Aggregate Information Related Only to the Underfunded Plans (Details) - Retirement Plans - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Projected benefit obligation	$ 88	$ 86.4
Accumulated benefit obligation	84.6	82.7
Fair value of plan assets	$ 83.3	$ 77.6

Employee Benefits - Components

Employee Benefits - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Retirement Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 1.9	$ 2.2	$ 2.6
Interest cost	4.1	3.1	2.1
Expected return on plan assets	(3.6)	(5.3)	(6.2)
Amortization of prior service cost	0.1	0.1	0
Amortization of unrecognized net loss	1.2	0.7	0.8
Settlement charge	1.3	2.9	1.6
Regulatory asset decrease	0	0	2.5
Net periodic benefit cost	5	3.7	3.4
PBOP
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	0	0	0.1
Interest cost	1.2	0.8	0.9
Expected return on plan assets	(2.4)	(1.8)	(2.7)
Amortization of prior service cost	0	0	0
Amortization of unrecognized net loss	0	0	0
Settlement charge	0	0	0
Regulatory asset decrease	0	0	0
Net periodic benefit cost	$ (1.2)	$ (1)	$ (1.7)

Employee Benefits - Estimated F

Employee Benefits - Estimated Future Benefit Payments (Details) $ in Millions	Dec. 31, 2023 USD ($)
Retirement Plans
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2024	$ 18.4
2025	12.5
2026	10.7
2027	10.5
2028	8.4
2029-2033	22.6
PBOP
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2024	2
2025	2
2026	1.9
2027	1.8
2028	1.7
2029-2033	$ 7.2

Employee Benefits - Weighted-Av

Employee Benefits - Weighted-Average Assumptions Used to Determine Benefit Obligations (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Pension
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	4.90%	5.30%
Expected return on plan assets	5%	5%
Pension | Minimum
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Rate of compensation increase	3%	3%
Pension | Maximum
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Rate of compensation increase	3.50%	4.50%
SRP
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	4.90%	5.30%
Expected return on plan assets	5%	5%
SRP | Minimum
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Rate of compensation increase	3%	3%
SRP | Maximum
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Rate of compensation increase	3.50%	4.50%
PBOP
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	5.10%	5.40%
Expected return on plan assets	3.25%	2.99%
Rate of compensation increase	0%	0%

Employee Benefits - Weighted-_2

Employee Benefits - Weighted-Average Assumptions Used to Determine Net Periodic Benefit Cost (Details)			3 Months Ended												12 Months Ended
	Dec. 31, 2022	Jun. 30, 2022	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate			4.90%	5.45%	5.15%	5.35%	5.30%	4.65%	4.10%	3%	2.30%	1.95%	2.05%	2.05%
Expected return on plan assets															5%	6.25%	6.50%
Rate of compensation increase																3%	3%
Pension | Minimum
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Rate of compensation increase															3%
Pension | Maximum
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Rate of compensation increase															4.50%
SRP
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	5.30%	4.15%													4.90%		1.55%
Expected return on plan assets															5%	6.25%	6.50%
Rate of compensation increase																3%	3%
SRP | Minimum
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Rate of compensation increase															3%
SRP | Maximum
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Rate of compensation increase															4.50%
PBOP
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate															5.40%	2.90%	2.60%
Expected return on plan assets															2.99%	2.01%	2.81%
Rate of compensation increase															0%	0%	0%

Employee Benefits - Master Trus

Employee Benefits - Master Trust Pension Fair Value Hierarchy (Details) - Fair Value, Measurements, Recurring - Pension Plan - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Defined Contribution Plan Disclosure [Line Items]
Total assets	$ 83.3	$ 77.6
Equity securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	34.6	17.5
Short-term investments
Defined Contribution Plan Disclosure [Line Items]
Total assets	17.3	28.3
Fixed income mutual funds
Defined Contribution Plan Disclosure [Line Items]
Total assets	26.3	31.8
Tax exempt securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	5.1
Level 1
Defined Contribution Plan Disclosure [Line Items]
Total assets	78.2	77.6
Level 1 | Equity securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	34.6	17.5
Level 1 | Short-term investments
Defined Contribution Plan Disclosure [Line Items]
Total assets	17.3	28.3
Level 1 | Fixed income mutual funds
Defined Contribution Plan Disclosure [Line Items]
Total assets	26.3	31.8
Level 1 | Tax exempt securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	0
Level 2
Defined Contribution Plan Disclosure [Line Items]
Total assets	5.1	0
Level 2 | Equity securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	0	0
Level 2 | Short-term investments
Defined Contribution Plan Disclosure [Line Items]
Total assets	0	0
Level 2 | Fixed income mutual funds
Defined Contribution Plan Disclosure [Line Items]
Total assets	0	0
Level 2 | Tax exempt securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	5.1
Level 3
Defined Contribution Plan Disclosure [Line Items]
Total assets	0	0
Level 3 | Equity securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	0	0
Level 3 | Short-term investments
Defined Contribution Plan Disclosure [Line Items]
Total assets	0	0
Level 3 | Fixed income mutual funds
Defined Contribution Plan Disclosure [Line Items]
Total assets	0	$ 0
Level 3 | Tax exempt securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	$ 0

Employee Benefits - Master Tr_2

Employee Benefits - Master Trust PBOP Fair Value Hierarchy (Details) - PBOP - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Other liabilities
Defined Contribution Plan Disclosure [Line Items]
Total liabilities	$ (39.3)	$ (13)
Short-term investments
Defined Contribution Plan Disclosure [Line Items]
Total assets	12.8	2.2
Other assets
Defined Contribution Plan Disclosure [Line Items]
Total assets	2.1	1.8
Asset-backed securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	0.8	0.9
Corporate bonds
Defined Contribution Plan Disclosure [Line Items]
Total assets	67	54.9
Tax exempt securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	38.9	34.4
Total assets
Defined Contribution Plan Disclosure [Line Items]
Total assets	121.6	94.2
Level 1 | Other liabilities
Defined Contribution Plan Disclosure [Line Items]
Total liabilities	(39.3)	(13)
Level 2 | Other liabilities
Defined Contribution Plan Disclosure [Line Items]
Total liabilities	0	0
Level 3 | Other liabilities
Defined Contribution Plan Disclosure [Line Items]
Total liabilities	0	0
Fair Value, Measurements, Recurring | Level 1 | Short-term investments
Defined Contribution Plan Disclosure [Line Items]
Total assets	12.8	2.2
Fair Value, Measurements, Recurring | Level 1 | Other assets
Defined Contribution Plan Disclosure [Line Items]
Total assets	2.1	1.8
Fair Value, Measurements, Recurring | Level 1 | Asset-backed securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	0	0
Fair Value, Measurements, Recurring | Level 1 | Corporate bonds
Defined Contribution Plan Disclosure [Line Items]
Total assets	0	0
Fair Value, Measurements, Recurring | Level 1 | Tax exempt securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	0	0
Fair Value, Measurements, Recurring | Level 1 | Total assets
Defined Contribution Plan Disclosure [Line Items]
Total assets	14.9	4
Fair Value, Measurements, Recurring | Level 2 | Short-term investments
Defined Contribution Plan Disclosure [Line Items]
Total assets	0	0
Fair Value, Measurements, Recurring | Level 2 | Other assets
Defined Contribution Plan Disclosure [Line Items]
Total assets	0	0
Fair Value, Measurements, Recurring | Level 2 | Asset-backed securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	0.8	0.9
Fair Value, Measurements, Recurring | Level 2 | Corporate bonds
Defined Contribution Plan Disclosure [Line Items]
Total assets	67	54.9
Fair Value, Measurements, Recurring | Level 2 | Tax exempt securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	38.9	34.4
Fair Value, Measurements, Recurring | Level 2 | Total assets
Defined Contribution Plan Disclosure [Line Items]
Total assets	106.7	90.2
Fair Value, Measurements, Recurring | Level 3 | Short-term investments
Defined Contribution Plan Disclosure [Line Items]
Total assets	0	0
Fair Value, Measurements, Recurring | Level 3 | Other assets
Defined Contribution Plan Disclosure [Line Items]
Total assets	0	0
Fair Value, Measurements, Recurring | Level 3 | Asset-backed securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	0	0
Fair Value, Measurements, Recurring | Level 3 | Corporate bonds
Defined Contribution Plan Disclosure [Line Items]
Total assets	0	0
Fair Value, Measurements, Recurring | Level 3 | Tax exempt securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	0	0
Fair Value, Measurements, Recurring | Level 3 | Total assets
Defined Contribution Plan Disclosure [Line Items]
Total assets	$ 0	$ 0

Employee Benefits - Long-Term I

Employee Benefits - Long-Term Incentive Compensation Plans (Details) - Performance Awards - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Granted amount	$ 16.3	$ 12.5
Compensation expense	14.2	12.3	$ 12.7
Unrecognized compensation expense	$ 9.8	$ 7.2

Income Taxes - Provision for In

Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current expense:
State	$ 0.8	$ 0.8	$ 0.5
Deferred provision:
State	0	0	0.2
Income taxes	$ 0.8	$ 0.8	$ 0.7

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Open tax year	2020 2021 2022 2023
Significant deferred tax assets or liabilities	$ 0	$ 0

Credit Risk (Details)

Credit Risk (Details) MMBTU in Millions, $ in Millions	Dec. 31, 2023 USD ($) $ / MMBTU MMBTU MMBbls	Dec. 31, 2022 USD ($) $ / MMBTU MMBTU MMBbls
Risks and Uncertainties [Abstract]
Gas balancing measurement (in TBtu) | MMBTU	11.2	13.3
Average market price of gas assumed (in dollars per MMBTU) | $ / MMBTU	2.33	5.33
Gas imbalance to subsidiaries asset liability | $	$ 26.1	$ 70.9
Natural gas liquids balancing volume (in MMBbls) | MMBbls	0	0

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Related Party Transaction [Line Items]
Administrative and general	$ 171.9	$ 147.7	$ 144.6
Cash dividends paid to parent company	300	102.2	102.2
Affiliates
Related Party Transaction [Line Items]
Administrative and general	4.3	3.7	5.5
Parent Company
Related Party Transaction [Line Items]
Cash dividends paid to parent company	$ 300	$ 102.2	$ 102.2

Supplemental Disclosure of Ca_3

Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash paid during the period for:
Amounts included in the measurement of operating lease liabilities	$ 4.9	$ 3.7	$ 4.1
Amounts included in the measurement of finance lease liability	1.1	1.1	1.1
Interest (net of amount capitalized)	147.3	156.3	152.2
Income taxes, net	0.7	0.6	0.5
Non-cash investing activities:
Accounts payable and PPE	47.7	44.4	19.4
Right-of-use asset obtained in exchange for lease obligations	3.4	0.2	13.1
Gas stored underground and PPE	$ 47.8	$ 0	$ 0