Boardwalk Pipeline Partners (BWP) 10-Q30 Oct 172017 Q3 Quarterly reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2017	Oct. 30, 2017
Entity Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Trading Symbol	BWP
Entity Registrant Name	BOARDWALK PIPELINE PARTNERS, LP
Entity Central Index Key	1,336,047
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		250,296,782

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Current Assets:
Cash and cash equivalents	$ 22.6	$ 4.6
Receivables:
Trade, net	94.2	127.1
Other	14	12.7
Gas transportation receivables	6.2	8.2
Gas and liquids stored underground	5.6	1.3
Prepayments	19.8	17.7
Other current assets	0.8	2.6
Total current assets	163.2	174.2
Property, Plant and Equipment:
Natural gas transmission and other plant	10,112.5	9,958.8
Construction work in progress	562.2	368.5
Property, plant and equipment, gross	10,674.7	10,327.3
Less—accumulated depreciation and amortization	2,543.1	2,333.8
Property, plant and equipment, net	8,131.6	7,993.5
Other Assets:
Goodwill	237.4	237.4
Gas stored underground	92.5	93.5
Other	137.4	139.2
Total other assets	467.3	470.1
Total Assets	8,762.1	8,637.8
Payables:
Trade	78.2	113.8
Affiliates	1.5	1.4
Other	9.7	23.7
Gas payables	6.1	6.7
Accrued taxes, other	75.7	52.7
Accrued interest	38.7	40.6
Accrued payroll and employee benefits	28.1	38.5
Construction retainage	24.5	19.6
Deferred income	2.9	7.5
Other current liabilities	27.3	28.4
Total current liabilities	292.7	332.9
Long-term debt and capital lease obligation	3,585.7	3,558
Other Liabilities and Deferred Credits:
Pension liability	19.3	22
Asset retirement obligation	44.6	44.7
Provision for other asset retirement	64.6	63.7
Payable to affiliate	16	16
Other	71	69.6
Total other liabilities and deferred credits	215.5	216
Commitments and Contingencies
Partners’ Capital:
Common units - 250.3 million units issued and outstanding as of September 30, 2017, and December 31, 2016	4,655.6	4,522.2
General partner	91.5	88.8
Accumulated other comprehensive loss	(78.9)	(80.1)
Total partners’ capital	4,668.2	4,530.9
Total Liabilities and Partners' Capital	$ 8,762.1	$ 8,637.8

CONDENSED CONSOLIDATED BALANCE3

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - shares shares in Millions	Sep. 30, 2017	Dec. 31, 2016
Common units issued	250.3	250.3
Common units outstanding	250.3	250.3

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF INCOME (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Operating Revenues:
Transportation	$ 272.9	$ 259.6	$ 870.2	$ 835.3
Parking and lending	4.3	4.9	17.6	13.4
Storage	18.9	23.4	62.2	68
Other	4.4	15.4	35.1	37.9
Total operating revenues	300.5	303.3	985.1	954.6
Operating Costs and Expenses:
Fuel and transportation	9	19.1	42.7	51
Operation and maintenance	49	52.1	141	143.8
Administrative and general	26.3	34.4	95.1	104.6
Depreciation and amortization	80.6	80.6	241.4	238.7
(Gain) loss on sale of assets and impairments	0	(0.1)	47.1	(0.1)
Taxes other than income taxes	24.8	23.5	75	72
Total operating costs and expenses	189.7	209.6	642.3	610
Operating income	110.8	93.7	342.8	344.6
Other Deductions (Income):
Interest expense	41	48.4	131.1	136.4
Interest income	0	(0.1)	(0.3)	(0.3)
Miscellaneous other income, net	(0.3)	(1.9)	(1.7)	(5.9)
Total other deductions	40.7	46.4	129.1	130.2
Income before income taxes	70.1	47.3	213.7	214.4
Income taxes	0.3	0	0.9	0.4
Net income	$ 69.8	$ 47.3	$ 212.8	$ 214
Net Income per Unit:
Net income per common unit (in dollars per unit)	$ 0.27	$ 0.19	$ 0.83	$ 0.84
Weighted-average number of common units outstanding (in units)	250.3	250.3	250.3	250.3
Cash distribution declared and paid to common units per common unit (in dollars per unit)	$ 0.10	$ 0.10	$ 0.30	$ 0.30

CONDENSED CONSOLIDATED STATEME5

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 69.8	$ 47.3	$ 212.8	$ 214
Other comprehensive income (loss):
Loss on cash flow hedge	0	0	(1.5)	0
Reclassification adjustment transferred to Net income from cash flow hedges	0.6	0.6	1.9	1.8
Pension and other postretirement benefit costs	0.1	0.6	0.8	2.3
Total Comprehensive Income	$ 70.5	$ 48.5	$ 214	$ 218.1

CONDENSED CONSOLIDATED STATEME6

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating Activities:
Net income	$ 212.8	$ 214
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	241.4	238.7
Amortization of deferred costs and other	4.9	4.3
(Gain) loss on sale of assets and impairments	47.1	(0.1)
Changes in operating assets and liabilities:
Trade and other receivables	31.2	10
Gas receivables and storage assets	(1.3)	0
Costs recoverable from customers	3	0
Other assets	(4.4)	(7.1)
Trade and other payables	(22)	(27)
Other payables, affiliates	0	(0.1)
Gas payables	(5.4)	2.9
Accrued liabilities	9.5	28.7
Other liabilities	(13.6)	(10.1)
Net cash provided by operating activities	503.2	454.2
Investing Activities:
Capital expenditures	(496)	(432.4)
Proceeds from sale of operating assets	63.7	0.2
Net cash used in investing activities	(432.3)	(432.2)
Financing Activities:
Proceeds from long-term debt, net of issuance cost	494	539.1
Repayment of borrowings from long-term debt	(575)	0
Proceeds from borrowings on revolving credit agreement	505	255
Repayment of borrowings on revolving credit agreement, including financing fees	(400)	(630.8)
Principal payment of capital lease obligation	(0.3)	(0.3)
Advances from affiliates	0.1	0
Distributions paid	(76.7)	(76.7)
Net cash (used in) provided by financing activities	(52.9)	86.3
Increase in cash and cash equivalents	18	108.3
Cash and cash equivalents at beginning of period	4.6	3.1
Cash and cash equivalents at end of period	$ 22.6	$ 111.4

CONDENSED CONSOLIDATED STATEME7

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN PARTNERS' CAPITAL (Unaudited) - USD ($) $ in Millions	Total	Accumulated Other Comp Income (Loss)	General Partner	Limited PartnerCommon Units
Beginning balance at Dec. 31, 2015	$ 4,326.7	$ (84.3)	$ 84.8	$ 4,326.2
Add (deduct):
Net income	214		4.3	209.7
Distributions paid	(76.7)		(1.5)	(75.2)
Other comprehensive income, net of tax	4.1	4.1
Ending balance at Sep. 30, 2016	4,468.1	(80.2)	87.6	4,460.7
Beginning balance at Dec. 31, 2016	4,530.9	(80.1)	88.8	4,522.2
Add (deduct):
Net income	212.8		4.2	208.6
Distributions paid	(76.7)		(1.5)	(75.2)
Other comprehensive income, net of tax	1.2	1.2
Ending balance at Sep. 30, 2017	$ 4,668.2	$ (78.9)	$ 91.5	$ 4,655.6

Basis of Presentation

Basis of Presentation	9 Months Ended
Basis of Presentation	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation Boardwalk Pipeline Partners, LP (the Partnership) 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, which consists of integrated natural gas and natural gas liquids and other hydrocarbons (herein referred to together as NGLs) pipeline and storage systems. As of October 27, 2017 , Boardwalk Pipelines Holding Corp. (BPHC), a wholly-owned subsidiary of Loews Corporation (Loews), owned 125.6 million of the Partnership’s common units, and, through Boardwalk GP, LP (Boardwalk GP), an indirect wholly-owned subsidiary of BPHC, holds the 2% general partner interest and all of the incentive distribution rights (IDRs) of the Partnership. As of October 27, 2017 , the common units and general partner interest owned by BPHC represent approximately 51% of the Partnership’s equity interests, excluding the IDRs. The Partnership’s common units are traded under the symbol “BWP” on the New York Stock Exchange. The accompanying unaudited condensed consolidated financial statements of the Partnership were prepared pursuant to the rules and regulations of the Securities and Exchange Commission. Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America (U.S.) (GAAP) have been condensed or omitted pursuant to such rules and regulations. In the opinion of management, the accompanying unaudited condensed consolidated financial statements reflect all adjustments (consisting of only normal recurring accruals) necessary to present fairly the Partnership's financial position as of September 30, 2017 , and December 31, 2016 , and its results of operations and comprehensive income for the three and nine months ended September 30, 2017 and 2016 , and changes in cash flows and changes in partners' capital for the nine months ended September 30, 2017 and 2016 . Reference is made to the Notes to Consolidated Financial Statements in the Partnership's Annual Report on Form 10-K for the year ended December 31, 2016 ( 2016 Annual Report on Form 10-K ), which should be read in conjunction with these unaudited condensed consolidated financial statements. The accounting policies described in Note 2 to the Consolidated Financial Statements included in the 2016 Annual Report on Form 10-K are the same used in preparing the accompanying unaudited condensed consolidated financial statements.

Asset Disposition and Impairmen

Asset Disposition and Impairments	9 Months Ended
Asset Disposition and Impairments	Sep. 30, 2017
Property, Plant and Equipment Assets Held-for-sale Disclosure [Abstract]
Asset Disposition and Impairments	Asset Disposition and Impairments On May 9, 2017 , the Partnership sold its Flag City Processing Partners, LLC subsidiary, which owns the Flag City processing plant and related assets, to a third party for approximately $63.6 million , including customary adjustments. The Partnership recorded losses and impairments, reported within Total Operating Costs and Expenses, of $47.1 million

Gas and Liquids Stored Undergro

Gas and Liquids Stored Underground and Gas and NGLs Receivables and Payables	9 Months Ended
	Sep. 30, 2017
Gas Balancing Arrangements [Abstract]
Gas and Liquids Stored Underground and Gas and NGLs Receivables and Payables	Gas and Liquids Stored Underground and Gas and NGLs Receivables and Payables The operating subsidiaries of the Partnership provide storage services whereby they store natural gas or NGLs on behalf of customers and also periodically hold customer gas under parking and lending (PAL) services. Since the customers retain title to the gas held by the Partnership in providing these services, the Partnership does not record the related gas on its balance sheet. The operating subsidiaries of the Partnership also periodically lend gas to customers under PAL and no-notice services (NNS), and gas or NGLs may be owed to the operating subsidiaries as a result of transportation imbalances. As of September 30, 2017 , the amount of gas owed to the operating subsidiaries of the Partnership due to gas imbalances and gas loaned under PAL and NNS was approximately 8.8 trillion British thermal units (TBtu). Assuming an average market price during September 2017 of $2.86 per million British thermal unit, the market value of that gas was approximately $25.1 million . As of September 30, 2017 , there were no outstanding NGLs imbalances owed to the operating subsidiaries. As of December 31, 2016 , the amount of gas owed to the operating subsidiaries of the Partnership due to gas imbalances and gas loaned under PAL and NNS was approximately 13.6 TBtu. As of December 31, 2016 , the amount of NGLs owed to the operating subsidiaries due to imbalances was less than 0.1

Other Comprehensive Income (OCI

Other Comprehensive Income (OCI) and Fair Value Measurements	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Other Comprehensive Income (OCI) and Fair Value Measurements	Other Comprehensive Income (OCI) and Fair Value Measurements OCI The Partnership had no outstanding derivatives at September 30, 2017 , and December 31, 2016 , but had $5.6 million and $6.0 million of Accumulated other comprehensive income (loss) (AOCI) related to cash flow hedges as of September 30, 2017 , and December 31, 2016 , which relate to settled treasury rate locks that are being amortized to earnings over the terms of the related interest payments, generally the terms of the related debt. The Partnership estimates that approximately $1.5 million of net losses from cash flow hedges reported in AOCI as of September 30, 2017 , are expected to be reclassified into earnings within the next twelve months. The following table shows the components and reclassifications to net income of AOCI which is included in Partners' Capital on the Condensed Consolidated Balance Sheets for the three months ended September 30, 2017 (in millions): Cash Flow Hedges Pension and Other Postretirement Costs Total Beginning balance, July 1, 2017 $ (6.2 ) $ (73.4 ) $ (79.6 ) Reclassifications: Interest expense 0.6 — 0.6 Pension and other postretirement benefit costs — 0.1 0.1 Ending balance, September 30, 2017 $ (5.6 ) $ (73.3 ) $ (78.9 ) The following table shows the components and reclassifications to net income of AOCI which is included in Partners' Capital on the Condensed Consolidated Balance Sheets for the three months ended September 30, 2016 (in millions): Cash Flow Hedges Pension and Other Postretirement Costs Total Beginning balance, July 1, 2016 $ (7.2 ) $ (74.2 ) $ (81.4 ) Reclassifications: Interest expense 0.6 — 0.6 Pension and other postretirement benefit costs — 0.6 0.6 Ending balance, September 30, 2016 $ (6.6 ) $ (73.6 ) $ (80.2 ) The following table shows the components and reclassifications to net income of AOCI which is included in Partners' Capital on the Condensed Consolidated Balance Sheets for the nine months ended September 30, 2017 (in millions): Cash Flow Hedges Pension and Other Postretirement Costs Total Beginning balance, January 1, 2017 $ (6.0 ) $ (74.1 ) $ (80.1 ) Loss recorded in AOCI (1.5 ) — (1.5 ) Reclassifications: Interest expense 1.9 — 1.9 Pension and other postretirement benefit costs — 0.8 0.8 Ending balance, September 30, 2017 $ (5.6 ) $ (73.3 ) $ (78.9 ) The following table shows the components and reclassifications to net income of AOCI which is included in Partners' Capital on the Condensed Consolidated Balance Sheets for the nine months ended September 30, 2016 (in millions): Cash Flow Hedges Pension and Other Postretirement Costs Total Beginning balance, January 1, 2016 $ (8.4 ) $ (75.9 ) $ (84.3 ) Reclassifications: Interest expense 1.8 — 1.8 Pension and other postretirement benefit costs — 2.3 2.3 Ending balance, September 30, 2016 $ (6.6 ) $ (73.6 ) $ (80.2 ) Financial Assets and Liabilities The following methods and assumptions were used in estimating the fair value amounts included in the disclosures for financial assets and liabilities, which are consistent with those disclosed in the 2016 Annual Report on Form 10-K : 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 Partnership's publicly traded debt is based on quoted market prices at September 30, 2017 , and December 31, 2016 . The fair market value of the debt that is not publicly traded is based on market prices of similar debt at September 30, 2017 , and December 31, 2016 . The carrying amount of the Partnership's variable-rate debt at September 30, 2017 , and December 31, 2016 , approximated fair value. The carrying amounts and estimated fair values of the Partnership's financial assets and liabilities which were not recorded at fair value on the Condensed Consolidated Balance Sheets as of September 30, 2017 , and December 31, 2016 , were as follows (in millions): As of September 30, 2017 Estimated Fair Value Financial Assets Carrying Amount Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 22.6 $ 22.6 $ — $ — $ 22.6 Financial Liabilities Long-term debt $ 3,586.7 (1) $ — $ 3,792.1 $ — $ 3,792.1 (1) The carrying amount of long-term debt excludes an $8.2 million long-term capital lease obligation and $9.2 million of unamortized debt issuance costs. As of December 31, 2016 Estimated Fair Value Financial Assets Carrying Amount Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 4.6 $ 4.6 $ — $ — $ 4.6 Financial Liabilities Long-term debt $ 3,558.9 (1) $ — $ 3,709.2 $ — $ 3,709.2 (1) The carrying amount of long-term debt excludes an $8.6 million long-term capital lease obligation and $9.5 million

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Proceedings and Settlements The Partnership's subsidiaries are parties to various legal actions arising in the normal course of business. Management believes the disposition of these outstanding legal actions will not have a material impact on the Partnership's financial condition, results of operations or cash flows. Refer to Note 4 of the Consolidated Financial Statements included in Part II, Item 8 of the Partnership's 2016 Annual Report on Form 10-K for further information regarding the Partnership’s legal proceedings. Southeast Louisiana Flood Protection Litigation The Partnership and its subsidiary, Gulf South Pipeline Company, LP, (Gulf South) along with approximately 100 other energy companies operating in Southern Louisiana, have been named as defendants in a petition for damages and injunctive relief in state district court for Orleans Parish, Louisiana, (Case No. 13-6911) by the Board of Commissioners of the Southeast Louisiana Flood Protection Authority - East (Flood Protection Authority). The case was filed in state court, but was removed to the U.S. District Court for the Eastern District of New Orleans (Court) in August 2013. The lawsuit claims include negligence, strict liability, public nuisance, private nuisance, breach of contract and breach of the natural servitude of drain against the defendants, 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 Flood Protection Authority. In addition to attorney fees and unspecified monetary damages, the lawsuit seeks abatement and restoration of the coastal lands, including backfilling and revegetating of canals dredged and used by the defendants, and abatement and restoration activities such as wetlands creation, reef creation, land bridge construction, hydrologic restoration, shoreline protection, structural protection, bank stabilization and ridge restoration. On February 13, 2015, the Court dismissed the case with prejudice. The Flood Protection Authority appealed the dismissal of the case to the U.S. Court of Appeals for the Fifth Circuit in May 2015 (Case No. 15-CV-30162). On March 3, 2017, the U.S. Court of Appeals for the Fifth Circuit upheld the Court’s dismissal. On April 12, 2017, the Fifth Circuit denied the Flood Protection Authorities' Petition for Rehearing En Banc. On July 11, 2017, the plaintiffs filed a writ of certiorari with the United States Supreme Court to review the case. Settlements and Insurance Proceeds In the second quarter 2016 , the Partnership received $12.7 million in cash from the settlement of a legal claim which was recorded in Transportation revenues. Environmental and Safety Matters The 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 September 30, 2017 , and December 31, 2016 , the Partnership had an accrued liability of approximately $5.1 million and $5.0 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 facts and circumstances related to these matters. The related expenditures are expected to occur over the next five years . As of September 30, 2017 , and December 31, 2016 , $1.1 million and $1.7 million were recorded in Other current liabilities and $4.0 million and $3.3 million were recorded in Other Liabilities and Deferred Credits . Commitments for Construction The Partnership’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. The commitments as of September 30, 2017 , were approximately $248.1 million , all of which are expected to be settled within the next twelve months. There were no substantial changes to the Partnership’s operating lease commitments, pipeline capacity agreements or capital lease obligation disclosed in Notes 4 and 10 to the Partnership’s 2016 Annual Report on Form 10-K

Cash Distributions and Net Inco

Cash Distributions and Net Income per Unit	9 Months Ended
Cash Distributions and Net Income per Unit	Sep. 30, 2017
Partners' Capital Notes [Abstract]
Cash Distributions and Net Income per Unit	Cash Distributions and Net Income per Unit Cash Distributions In the third quarters 2017 and 2016 , the Partnership declared and paid quarterly distributions to its common unitholders of record of $0.10 per common unit and an amount to the general partner on behalf of its 2% general partner interest. In October 2017 , the Partnership declared a quarterly cash distribution to unitholders of record of $0.10 per common unit. Net Income per Unit For purposes of calculating net income per unit, net income for the current period is reduced by the amount of available cash that will be distributed with respect to that period. Payments made on account of the Partnership’s various ownership interests are determined in relation to actual declared distributions, and are not based on the assumed allocations required under GAAP. Any residual amount representing undistributed net income (or loss) is assumed to be allocated to the various ownership interests in accordance with the contractual provisions of the partnership agreement on a pro rata basis. Net income per unit is calculated based on the weighted-average number of units outstanding for the period. The following table provides a reconciliation of net income and the assumed allocation of net income to the common units for purposes of computing net income per unit for the three months ended September 30, 2017 (in millions, except per unit data): Total Common Units General Partner and IDRs Net income $ 69.8 Declared distribution 25.5 $ 25.0 $ 0.5 Assumed allocation of undistributed net loss 44.3 43.4 0.9 Assumed allocation of net income attributable to limited $ 69.8 $ 68.4 $ 1.4 Weighted-average units outstanding 250.3 Net income per unit $ 0.27 The following table provides a reconciliation of net income and the assumed allocation of net income to the common units for purposes of computing net income per unit for the three months ended September 30, 2016 (in millions, except per unit data): Total Common Units General Partner and IDRs Net income $ 47.3 Declared distribution 25.5 $ 25.0 $ 0.5 Assumed allocation of undistributed net income 21.8 21.4 0.4 Assumed allocation of net income attributable to limited $ 47.3 $ 46.4 $ 0.9 Weighted-average units outstanding 250.3 Net income per unit $ 0.19 The following table provides a reconciliation of net income and the assumed allocation of net income to the common units for purposes of computing net income per unit for the nine months ended September 30, 2017 (in millions, except per unit data): Total Common Units General Partner and IDRs Net income $ 212.8 Declared distribution 76.6 $ 75.1 $ 1.5 Assumed allocation of undistributed net income 136.2 133.5 2.7 Assumed allocation of net income attributable to limited $ 212.8 $ 208.6 $ 4.2 Weighted-average units outstanding 250.3 Net income per unit $ 0.83 The following table provides a reconciliation of net income and the assumed allocation of net income to the common units for purposes of computing net income per unit for the nine months ended September 30, 2016 (in millions, except per unit data): Total Common Units General Partner and IDRs Net income $ 214.0 Declared distribution 76.6 $ 75.1 $ 1.5 Assumed allocation of undistributed net income 137.4 134.7 2.7 Assumed allocation of net income attributable to limited $ 214.0 $ 209.8 $ 4.2 Weighted-average units outstanding 250.3 Net income per unit $ 0.84

Financing

Financing	9 Months Ended
Financing	Sep. 30, 2017
Debt Disclosure [Abstract]
Financing	Financing Notes and Debentures As of September 30, 2017 , and December 31, 2016 , the Partnership had notes and debentures outstanding of $3.3 billion and $3.4 billion with weighted-average interest rates of 5.18% and 5.46% . The indentures governing the notes and debentures have restrictive covenants which provide that, with certain exceptions, neither the Partnership 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 Partnership's debt obligations are unsecured. At September 30, 2017 , Boardwalk Pipelines and its operating subsidiaries were in compliance with their debt covenants. The Partnership has included $185.0 million of notes which mature in less than one year as long-term debt on its Condensed Consolidated Balance Sheet as of September 30, 2017 . The Partnership has the intent and the ability to refinance the notes through the available borrowing capacity under its revolving credit facility as of September 30, 2017 . The Partnership expects to retire these notes at their maturity. Issuance of Notes For the nine months ended September 30, 2017 and 2016 , the Partnership completed the following debt issuances (in millions, except interest rates): Date of Issuance Issuing Subsidiary Amount of Issuance Purchaser Discounts and Expenses Net Proceeds Interest Rate Maturity Date Interest Payable January 2017 Boardwalk Pipelines $ 500.0 $ 6.0 $ 494.0 (1) 4.45% July 15, 2027 January 15 and July 15 May 2016 Boardwalk Pipelines $ 550.0 $ 10.9 $ 539.1 (2) 5.95% June 1, 2026 June 1 and December 1 (1) The net proceeds of this offering were used to retire the outstanding $275.0 million aggregate principal amount of Gulf South's 6.30% notes due 2017 (Gulf South 2017 Notes) and to fund growth capital expenditures. (2) The net proceeds of this offering were used to retire the outstanding $250.0 million aggregate principal amount of Boardwalk Pipelines 5.875% notes due 2016 and the outstanding $300.0 million aggregate principal amount of Boardwalk Pipelines 5.50% notes due 2017 at their maturity. Revolving Credit Facility Outstanding borrowings under the Partnership’s revolving credit facility as of September 30, 2017 , and December 31, 2016 , were $285.0 million and $180.0 million , with weighted-average borrowing rates of 2.49% and 1.96% . The Partnership and its subsidiaries were in compliance with all covenant requirements under the revolving credit facility as of September 30, 2017 . In July 2017, the Partnership extended the maturity date of the revolving credit facility by one additional year to May 26, 2022. The revolving credit facility has a borrowing capacity of $1.5 billion through May 26, 2020, and a borrowing capacity of $1.475 billion from May 27, 2020, to May 26, 2022. Subordinated Loan Agreement with Affiliate The Partnership has in place a Subordinated Loan Agreement with BPHC (Subordinated Loan) under which the Partnership can borrow up to $300.0 million through December 31, 2018 . Through the date of this Report, the Partnership had no

Employee Benefits

Employee Benefits	9 Months Ended
Employee Benefits	Sep. 30, 2017
Retirement Benefits [Abstract]
Employee Benefits	Employee Benefits Defined Benefit Retirement Plans and Postretirement Benefits Other Than Pension (PBOP) Components of net periodic benefit cost for both the Retirement Plans and PBOP for the three months ended September 30, 2017 and 2016 , were as follows (in millions): Retirement Plans PBOP For the For the 2017 2016 2017 2016 Service cost $ 0.8 $ 0.9 $ — $ 0.1 Interest cost 1.2 1.2 0.4 0.5 Expected return on plan assets (2.0 ) (2.0 ) (1.1 ) (1.2 ) Amortization of prior service credit — — — (0.2 ) Amortization of unrecognized net loss 0.4 0.6 — — Settlement charge 0.4 0.7 — — Net periodic benefit cost $ 0.8 $ 1.4 $ (0.7 ) $ (0.8 ) Components of net periodic benefit cost for both the Retirement Plans and PBOP for the nine months ended September 30, 2017 and 2016 , were as follows (in millions): Retirement Plans PBOP For the For the 2017 2016 2017 2016 Service cost $ 2.6 $ 2.7 $ 0.1 $ 0.3 Interest cost 3.5 3.6 1.2 1.5 Expected return on plan assets (5.9 ) (6.0 ) (3.3 ) (3.6 ) Amortization of prior service credit — — — (0.7 ) Amortization of unrecognized net loss 1.3 1.8 — — Settlement charge 1.5 2.7 — — Net periodic benefit cost $ 3.0 $ 4.8 $ (2.0 ) $ (2.5 ) The Partnership contributed $3.0 million to the defined benefit pension plan in the third quarter 2017 . Defined Contribution Plans Texas Gas Transmission, LLC employees hired on or after November 1, 2006, and all other employees of the Partnership are provided retirement benefits under a defined contribution money purchase plan. The Partnership also provides 401(k) plan benefits to its employees. Costs related to the Partnership’s defined contribution plans were $2.7 million for each of the three months ended September 30, 2017 and 2016 , and $8.1 million and $7.8 million for the nine months ended September 30, 2017 and 2016

Related Party Transactions

Related Party Transactions	9 Months Ended
Related Party Transactions	Sep. 30, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Loews provides a variety of corporate services to the Partnership under service agreements, including but not limited to, information technology, tax, risk management, internal audit and corporate development services and also charges the Partnership for allocated overheads. The Partnership incurred charges related to these services of $1.7 million and $1.8 million for the three months ended September 30, 2017 and 2016 , and $5.0 million and $5.3 million for the nine months ended September 30, 2017 and 2016 . Distributions paid related to limited partner units held by BPHC and the 2% general partner interest held by Boardwalk GP were $13.1 million and $13.2 million for the three months ended September 30, 2017 and 2016 , and $39.2 million and $39.5 million for the nine months ended September 30, 2017 and 2016

Supplemental Disclosure of Cash

Supplemental Disclosure of Cash Flow Information	9 Months Ended
Supplemental Disclosure of Cash Flow Information	Sep. 30, 2017
Supplemental Cash Flow Elements [Abstract]
Supplemental Disclosure of Cash Flow Information	Supplemental Disclosure of Cash Flow Information (in millions): For the 2017 2016 Cash paid during the period for: Interest (net of amount capitalized) $ 125.8 $ 122.3 Non-cash adjustments: Accounts payable and property, plant and equipment 66.6 81.0

Recently Issued Accounting Pron

Recently Issued Accounting Pronouncements	9 Months Ended
Recently Issued Accounting Pronouncements	Sep. 30, 2017
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update 2014-09, Revenue from Contracts with Customers (Topic 606), (ASU 2014-09) which will require entities to recognize revenue in an amount that reflects the transfer of promised goods or services to a customer in an amount based on the consideration the entity expects to be entitled to in exchange for those goods or services. ASU 2014-09 also requires disclosures regarding the nature, amount, timing and uncertainty of revenues and cash flows from contracts with customers. The amendments may be applied retrospectively to each prior period presented, or retrospectively with the cumulative effect recognized as of the date of initial application. ASU 2014-09 is effective for interim and annual reporting periods beginning after December 15, 2017. The Partnership has substantially completed a review of its contracts with customers in relation to the requirements of ASU 2014-09, and has tentatively concluded that the implementation of ASU 2014-09 will not have a material impact on the timing or amount of revenue recognized for most of its contracts. The Partnership intends to apply ASU 2014-09 to its financial statements retrospectively with the cumulative effect of implementation recognized as of January 1, 2018. In February 2016, the FASB issued Accounting Standards Update 2016-02, Leases (Topic 842)

Guarantee of Securities of Subs

Guarantee of Securities of Subsidiaries	9 Months Ended
Guarantee of Securities of Subsidiaries	Sep. 30, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Guarantee of Securities of Subsidiaries	Guarantee of Securities of Subsidiaries Boardwalk Pipelines (Subsidiary Issuer) has issued securities which have been fully and unconditionally guaranteed by the Partnership (Parent Guarantor). The Subsidiary Issuer is 100% owned by the Parent Guarantor. The Partnership's subsidiaries had no significant restrictions on their ability to pay distributions or make loans to the Partnership except as noted in the debt covenants and had no restricted assets at September 30, 2017 , and December 31, 2016 . Note 7 contains additional information regarding the Partnership's debt and related covenants. The Partnership has provided the following condensed consolidating financial information in accordance with Regulation S-X Rule 3-10, Financial Statements of Guarantors and Issuers of Guaranteed Securities Registered or Being Registered . Condensed Consolidating Balance Sheets as of September 30, 2017 (Millions) Assets Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Cash and cash equivalents $ 0.4 $ 15.1 $ 7.1 $ — $ 22.6 Receivables — — 108.2 — 108.2 Receivables - affiliate — — 6.9 (6.9 ) — Gas and liquids stored underground — — 5.6 — 5.6 Prepayments 0.4 — 19.4 — 19.8 Advances to affiliates — 1.4 22.4 (23.8 ) — Other current assets — — 8.2 (1.2 ) 7.0 Total current assets 0.8 16.5 177.8 (31.9 ) 163.2 Investment in consolidated subsidiaries 2,602.8 6,665.8 — (9,268.6 ) — Property, plant and equipment, gross 0.6 — 10,674.1 — 10,674.7 Less–accumulated depreciation and amortization 0.6 — 2,542.5 — 2,543.1 Property, plant and equipment, net — — 8,131.6 — 8,131.6 Advances to affiliates – noncurrent 2,082.4 886.4 373.4 (3,342.2 ) — Other noncurrent assets — 3.4 464.1 (0.2 ) 467.3 Total other assets 2,082.4 889.8 837.5 (3,342.4 ) 467.3 Total Assets $ 4,686.0 $ 7,572.1 $ 9,146.9 $ (12,642.9 ) $ 8,762.1 Liabilities and Partners' Capital Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Payables $ 0.1 $ 0.2 $ 87.6 $ — $ 87.9 Payable to affiliates 1.5 — 6.9 (6.9 ) 1.5 Advances from affiliates — 22.4 1.4 (23.8 ) — Other current liabilities 0.2 29.9 174.6 (1.4 ) 203.3 Total current liabilities 1.8 52.5 270.5 (32.1 ) 292.7 Long-term debt and capital lease obligation — 2,461.0 1,124.7 — 3,585.7 Payable to affiliate - noncurrent 16.0 — — — 16.0 Advances from affiliates - noncurrent — 2,455.8 886.4 (3,342.2 ) — Other noncurrent liabilities — — 199.5 — 199.5 Total other liabilities and deferred credits 16.0 2,455.8 1,085.9 (3,342.2 ) 215.5 Total partners' capital 4,668.2 2,602.8 6,665.8 (9,268.6 ) 4,668.2 Total Liabilities and Partners' Capital $ 4,686.0 $ 7,572.1 $ 9,146.9 $ (12,642.9 ) $ 8,762.1 Condensed Consolidating Balance Sheets as of December 31, 2016 (Millions) Assets Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Cash and cash equivalents $ 0.6 $ 1.8 $ 2.2 $ — $ 4.6 Receivables — — 139.8 — 139.8 Receivables - affiliate — — 7.0 (7.0 ) — Gas and liquids stored underground — — 1.3 — 1.3 Prepayments 0.4 — 17.3 — 17.7 Advances to affiliates — 72.9 102.7 (175.6 ) — Other current assets — — 13.9 (3.1 ) 10.8 Total current assets 1.0 74.7 284.2 (185.7 ) 174.2 Investment in consolidated subsidiaries 2,423.2 6,653.6 — (9,076.8 ) — Property, plant and equipment, gross 0.6 — 10,326.7 — 10,327.3 Less–accumulated depreciation and amortization 0.6 — 2,333.2 — 2,333.8 Property, plant and equipment, net — — 7,993.5 — 7,993.5 Advances to affiliates – noncurrent 2,125.0 435.0 229.3 (2,789.3 ) — Other noncurrent assets — 3.3 466.8 — 470.1 Total other assets 2,125.0 438.3 696.1 (2,789.3 ) 470.1 Total Assets $ 4,549.2 $ 7,166.6 $ 8,973.8 $ (12,051.8 ) $ 8,637.8 Liabilities and Partners' Capital Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Payables $ 0.9 $ 0.2 $ 136.4 $ — $ 137.5 Payable to affiliates 1.4 — 7.0 (7.0 ) 1.4 Advances from affiliates — 102.7 72.9 (175.6 ) — Other current liabilities — 21.8 175.3 (3.1 ) 194.0 Total current liabilities 2.3 124.7 391.6 (185.7 ) 332.9 Long-term debt and capital lease obligation — 2,264.4 1,293.6 — 3,558.0 Payable to affiliate - noncurrent 16.0 — — — 16.0 Advances from affiliates - noncurrent — 2,354.3 435.0 (2,789.3 ) — Other noncurrent liabilities — — 200.0 — 200.0 Total other liabilities and deferred credits 16.0 2,354.3 635.0 (2,789.3 ) 216.0 Total partners' capital 4,530.9 2,423.2 6,653.6 (9,076.8 ) 4,530.9 Total Liabilities and Partners' Capital $ 4,549.2 $ 7,166.6 $ 8,973.8 $ (12,051.8 ) $ 8,637.8 Condensed Consolidating Statements of Income for the Three Months Ended September 30, 2017 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Operating Revenues: Transportation $ — $ — $ 295.4 $ (22.5 ) $ 272.9 Parking and lending — — 4.3 — 4.3 Storage — — 18.9 — 18.9 Other — — 4.4 — 4.4 Total operating revenues — — 323.0 (22.5 ) 300.5 Operating Costs and Expenses: Fuel and transportation — — 31.5 (22.5 ) 9.0 Operation and maintenance — — 49.0 — 49.0 Administrative and general (0.3 ) — 26.6 — 26.3 Other operating costs and expenses 0.4 — 105.0 — 105.4 Total operating costs and expenses 0.1 — 212.1 (22.5 ) 189.7 Operating (loss) income (0.1 ) — 110.9 — 110.8 Other Deductions (Income): Interest expense — 32.2 8.8 — 41.0 Interest (income) expense - affiliates, net (12.4 ) 11.0 1.4 — — Equity in earnings of subsidiaries (57.5 ) (100.7 ) — 158.2 — Miscellaneous other income, net — — (0.3 ) — (0.3 ) Total other (income) deductions (69.9 ) (57.5 ) 9.9 158.2 40.7 Income (loss) before income taxes 69.8 57.5 101.0 (158.2 ) 70.1 Income taxes — — 0.3 — 0.3 Net income (loss) $ 69.8 $ 57.5 $ 100.7 $ (158.2 ) $ 69.8 Condensed Consolidating Statements of Income for the Three Months Ended September 30, 2016 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Operating Revenues: Transportation $ — $ — $ 281.9 $ (22.3 ) $ 259.6 Parking and lending — — 5.1 (0.2 ) 4.9 Storage — — 23.4 — 23.4 Other — — 15.4 — 15.4 Total operating revenues — — 325.8 (22.5 ) 303.3 Operating Costs and Expenses: Fuel and transportation — — 41.6 (22.5 ) 19.1 Operation and maintenance — — 52.1 — 52.1 Administrative and general — — 34.4 — 34.4 Other operating costs and expenses 0.1 — 103.9 — 104.0 Total operating costs and expenses 0.1 — 232.0 (22.5 ) 209.6 Operating (loss) income (0.1 ) — 93.8 — 93.7 Other Deductions (Income): Interest expense — 34.6 13.8 — 48.4 Interest (income) expense - affiliates, net (9.7 ) 11.7 (2.0 ) — — Interest income — — (0.1 ) — (0.1 ) Equity in earnings of subsidiaries (37.7 ) (84.0 ) — 121.7 — Miscellaneous other income, net — — (1.9 ) — (1.9 ) Total other (income) deductions (47.4 ) (37.7 ) 9.8 121.7 46.4 Income (loss) before income taxes 47.3 37.7 84.0 (121.7 ) 47.3 Income taxes — — — — — Net income (loss) $ 47.3 $ 37.7 $ 84.0 $ (121.7 ) $ 47.3 Condensed Consolidating Statements of Income for the Nine Months Ended September 30, 2017 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Operating Revenues: Transportation $ — $ — $ 936.5 $ (66.3 ) $ 870.2 Parking and lending — — 17.8 (0.2 ) 17.6 Storage — — 62.2 — 62.2 Other — — 35.1 — 35.1 Total operating revenues — — 1,051.6 (66.5 ) 985.1 Operating Costs and Expenses: Fuel and transportation — — 109.2 (66.5 ) 42.7 Operation and maintenance — — 141.0 — 141.0 Administrative and general (0.3 ) — 95.4 — 95.1 Other operating costs and expenses 0.5 — 363.0 — 363.5 Total operating costs and expenses 0.2 — 708.6 (66.5 ) 642.3 Operating (loss) income (0.2 ) — 343.0 — 342.8 Other Deductions (Income): Interest expense — 97.6 33.5 — 131.1 Interest (income) expense - affiliates, net (34.6 ) 30.1 4.5 — — Interest income — (0.2 ) (0.1 ) — (0.3 ) Equity in earnings of subsidiaries (178.4 ) (305.9 ) — 484.3 — Miscellaneous other income, net — — (1.7 ) — (1.7 ) Total other (income) deductions (213.0 ) (178.4 ) 36.2 484.3 129.1 Income (loss) before income taxes 212.8 178.4 306.8 (484.3 ) 213.7 Income taxes — — 0.9 — 0.9 Net income (loss) $ 212.8 $ 178.4 $ 305.9 $ (484.3 ) $ 212.8 Condensed Consolidating Statements of Income for the Nine Months Ended September 30, 2016 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Operating Revenues: Transportation $ — $ — $ 901.0 $ (65.7 ) $ 835.3 Parking and lending — — 14.6 (1.2 ) 13.4 Storage — — 68.0 — 68.0 Other — — 37.9 — 37.9 Total operating revenues — — 1,021.5 (66.9 ) 954.6 Operating Costs and Expenses: Fuel and transportation — — 117.9 (66.9 ) 51.0 Operation and maintenance — — 143.8 — 143.8 Administrative and general 0.1 — 104.5 — 104.6 Other operating costs and expenses 0.3 — 310.3 — 310.6 Total operating costs and expenses 0.4 — 676.5 (66.9 ) 610.0 Operating (loss) income (0.4 ) — 345.0 — 344.6 Other Deductions (Income): Interest expense — 91.1 45.3 — 136.4 Interest (income) expense - affiliates, net (27.6 ) 35.2 (7.6 ) — — Interest income — — (0.3 ) — (0.3 ) Equity in earnings of subsidiaries (187.0 ) (313.3 ) — 500.3 — Miscellaneous other deductions (income), net 0.2 — (6.1 ) — (5.9 ) Total other (income) deductions (214.4 ) (187.0 ) 31.3 500.3 130.2 Income (loss) before income taxes 214.0 187.0 313.7 (500.3 ) 214.4 Income taxes — — 0.4 — 0.4 Net income (loss) $ 214.0 $ 187.0 $ 313.3 $ (500.3 ) $ 214.0 Condensed Consolidating Statements of Comprehensive Income for the Three Months Ended September 30, 2017 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net income (loss) $ 69.8 $ 57.5 $ 100.7 $ (158.2 ) $ 69.8 Other comprehensive income (loss): Reclassification adjustment transferred to Net income from cash flow hedges 0.6 0.6 0.2 (0.8 ) 0.6 Pension and other postretirement benefit costs 0.1 0.1 0.1 (0.2 ) 0.1 Total Comprehensive Income (Loss) $ 70.5 $ 58.2 $ 101.0 $ (159.2 ) $ 70.5 Condensed Consolidating Statements of Comprehensive Income for the Three Months Ended September 30, 2016 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net income (loss) $ 47.3 $ 37.7 $ 84.0 $ (121.7 ) $ 47.3 Other comprehensive income (loss): Reclassification adjustment transferred to Net income from cash flow hedges 0.6 0.6 0.2 (0.8 ) 0.6 Pension and other postretirement benefit costs 0.6 0.6 0.6 (1.2 ) 0.6 Total Comprehensive Income (Loss) $ 48.5 $ 38.9 $ 84.8 $ (123.7 ) $ 48.5 Condensed Consolidating Statements of Comprehensive Income for the Nine Months Ended September 30, 2017 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net income (loss) $ 212.8 $ 178.4 $ 305.9 $ (484.3 ) $ 212.8 Other comprehensive income (loss): Loss on cash flow hedge (1.5 ) (1.5 ) — 1.5 (1.5 ) Reclassification adjustment transferred to Net income from cash flow hedges 1.9 1.9 0.5 (2.4 ) 1.9 Pension and other postretirement benefit costs 0.8 0.8 0.8 (1.6 ) 0.8 Total Comprehensive Income (Loss) $ 214.0 $ 179.6 $ 307.2 $ (486.8 ) $ 214.0 Condensed Consolidating Statements of Comprehensive Income for the Nine Months Ended September 30, 2016 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net income (loss) $ 214.0 $ 187.0 $ 313.3 $ (500.3 ) $ 214.0 Other comprehensive income (loss): Reclassification adjustment transferred to Net income from cash flow hedges 1.8 1.8 0.6 (2.4 ) 1.8 Pension and other postretirement benefit costs 2.3 2.3 2.3 (4.6 ) 2.3 Total Comprehensive Income (Loss) $ 218.1 $ 191.1 $ 316.2 $ (507.3 ) $ 218.1 Condensed Consolidating Statements of Cash Flow for the Nine Months Ended September 30, 2017 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net cash provided by (used in) operating activities $ 33.8 $ (117.0 ) $ 586.4 $ — $ 503.2 INVESTING ACTIVITIES: Capital expenditures — — (496.0 ) — (496.0 ) Proceeds from sale of operating assets — — 63.7 — 63.7 Advances to affiliates, net 42.6 (398.5 ) (377.4 ) 733.3 — Net cash provided by (used in) investing activities 42.6 (398.5 ) (809.7 ) 733.3 (432.3 ) FINANCING ACTIVITIES: Proceeds from long-term debt, net of issuance cost — 494.0 — — 494.0 Repayment of borrowings from long-term debt — (300.0 ) (275.0 ) — (575.0 ) Proceeds from borrowings on revolving credit agreement — — 505.0 — 505.0 Repayment of borrowings on revolving credit agreement — — (400.0 ) — (400.0 ) Principal payment of capital lease obligation — — (0.3 ) — (0.3 ) Advances from affiliates, net 0.1 334.8 398.5 (733.3 ) 0.1 Distributions paid (76.7 ) — — — (76.7 ) Net cash (used in) provided by financing activities (76.6 ) 528.8 228.2 (733.3 ) (52.9 ) (Decrease) increase in cash and cash equivalents (0.2 ) 13.3 4.9 — 18.0 Cash and cash equivalents at beginning of period 0.6 1.8 2.2 — 4.6 Cash and cash equivalents at end of period $ 0.4 $ 15.1 $ 7.1 $ — $ 22.6 Condensed Consolidating Statements of Cash Flow for the Nine Months Ended September 30, 2016 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net cash provided by (used in) operating activities $ 27.3 $ (108.3 ) $ 535.2 $ — $ 454.2 INVESTING ACTIVITIES: Capital expenditures — — (432.4 ) — (432.4 ) Proceeds from sale of operating assets — — 0.2 — 0.2 Advances to affiliates, net 49.7 (16.8 ) 256.5 (289.4 ) — Net cash provided by (used in) investing activities 49.7 (16.8 ) (175.7 ) (289.4 ) (432.2 ) FINANCING ACTIVITIES: Proceeds from long-term debt, net of issuance cost — 539.1 — — 539.1 Proceeds from borrowings on revolving credit agreement — — 255.0 — 255.0 Repayment of borrowings on revolving credit agreement, including financing fees — (0.8 ) (630.0 ) — (630.8 ) Principal payment of capital lease obligation — — (0.3 ) — (0.3 ) Advances from affiliates, net — (306.2 ) 16.8 289.4 — Distributions paid (76.7 ) — — — (76.7 ) Net cash (used in) provided by financing activities (76.7 ) 232.1 (358.5 ) 289.4 86.3 Increase in cash and cash equivalents 0.3 107.0 1.0 — 108.3 Cash and cash equivalents at beginning of period — 0.3 2.8 — 3.1 Cash and cash equivalents at end of period $ 0.3 $ 107.3 $ 3.8 $ — $ 111.4

Basis of Presentation (Policies

Basis of Presentation (Policies)	9 Months Ended
Basis of Presentation (Policies)	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Accounting, Policy	The accompanying unaudited condensed consolidated financial statements of the Partnership were prepared pursuant to the rules and regulations of the Securities and Exchange Commission. Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America (U.S.) (GAAP) have been condensed or omitted pursuant to such rules and regulations. In the opinion of management, the accompanying unaudited condensed consolidated financial statements reflect all adjustments (consisting of only normal recurring accruals) necessary to present fairly the Partnership's financial position as of September 30, 2017 , and December 31, 2016 , and its results of operations and comprehensive income for the three and nine months ended September 30, 2017 and 2016 , and changes in cash flows and changes in partners' capital for the nine months ended September 30, 2017 and 2016 . Reference is made to the Notes to Consolidated Financial Statements in the Partnership's Annual Report on Form 10-K for the year ended December 31, 2016 ( 2016 Annual Report on Form 10-K ), which should be read in conjunction with these unaudited condensed consolidated financial statements. The accounting policies described in Note 2 to the Consolidated Financial Statements included in the 2016 Annual Report on Form 10-K

Gas and Liquids Stored Underg21

Gas and Liquids Stored Underground and Gas and NGLs Receivables and Payables (Policies)	9 Months Ended
	Sep. 30, 2017
Gas Balancing Arrangements [Abstract]
Gas and Liquids Stored Underground and Gas and NGLs Receivables and Payables, Policy	The operating subsidiaries of the Partnership provide storage services whereby they store natural gas or NGLs on behalf of customers and also periodically hold customer gas under parking and lending (PAL) services. Since the customers retain title to the gas held by the Partnership in providing these services, the Partnership does not record the related gas on its balance sheet.

Other Comprehensive Income (O22

Other Comprehensive Income (OCI) and Fair Value Measurements (Policies)	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments, Policy	Financial Assets and Liabilities The following methods and assumptions were used in estimating the fair value amounts included in the disclosures for financial assets and liabilities, which are consistent with those disclosed in the 2016 Annual Report on Form 10-K : 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 Partnership's publicly traded debt is based on quoted market prices at September 30, 2017 , and December 31, 2016 . The fair market value of the debt that is not publicly traded is based on market prices of similar debt at September 30, 2017 , and December 31, 2016 . The carrying amount of the Partnership's variable-rate debt at September 30, 2017 , and December 31, 2016

Commitments and Contingencies (

Commitments and Contingencies (Policies)	9 Months Ended
Commitments and Contingencies (Policies)	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Environmental Costs, Policy	The liability represents management’s estimate of the undiscounted future obligations based on evaluations and discussions with counsel and operating personnel and the current facts and circumstances related to these matters.

Cash Distributions and Net In24

Cash Distributions and Net Income per Unit (Policies)	9 Months Ended
Cash Distributions and Net Income per Unit (Policies)	Sep. 30, 2017
Partners' Capital Notes [Abstract]
Net Income Per Unit, Policy	Net Income per Unit

Recently Issued Accounting Pr25

Recently Issued Accounting Pronouncements (Policies)	9 Months Ended
Recently Issued Accounting Pronouncements (Policies)	Sep. 30, 2017
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
New Accounting Pronouncements, Policy	Recently Issued Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update 2014-09, Revenue from Contracts with Customers (Topic 606), (ASU 2014-09) which will require entities to recognize revenue in an amount that reflects the transfer of promised goods or services to a customer in an amount based on the consideration the entity expects to be entitled to in exchange for those goods or services. ASU 2014-09 also requires disclosures regarding the nature, amount, timing and uncertainty of revenues and cash flows from contracts with customers. The amendments may be applied retrospectively to each prior period presented, or retrospectively with the cumulative effect recognized as of the date of initial application. ASU 2014-09 is effective for interim and annual reporting periods beginning after December 15, 2017. The Partnership has substantially completed a review of its contracts with customers in relation to the requirements of ASU 2014-09, and has tentatively concluded that the implementation of ASU 2014-09 will not have a material impact on the timing or amount of revenue recognized for most of its contracts. The Partnership intends to apply ASU 2014-09 to its financial statements retrospectively with the cumulative effect of implementation recognized as of January 1, 2018. In February 2016, the FASB issued Accounting Standards Update 2016-02, Leases (Topic 842)

Other Comprehensive Income (O26

Other Comprehensive Income (OCI) and Fair Value Measurements OCI (Tables)	9 Months Ended
	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following table shows the components and reclassifications to net income of AOCI which is included in Partners' Capital on the Condensed Consolidated Balance Sheets for the three months ended September 30, 2017 (in millions): Cash Flow Hedges Pension and Other Postretirement Costs Total Beginning balance, July 1, 2017 $ (6.2 ) $ (73.4 ) $ (79.6 ) Reclassifications: Interest expense 0.6 — 0.6 Pension and other postretirement benefit costs — 0.1 0.1 Ending balance, September 30, 2017 $ (5.6 ) $ (73.3 ) $ (78.9 ) The following table shows the components and reclassifications to net income of AOCI which is included in Partners' Capital on the Condensed Consolidated Balance Sheets for the three months ended September 30, 2016 (in millions): Cash Flow Hedges Pension and Other Postretirement Costs Total Beginning balance, July 1, 2016 $ (7.2 ) $ (74.2 ) $ (81.4 ) Reclassifications: Interest expense 0.6 — 0.6 Pension and other postretirement benefit costs — 0.6 0.6 Ending balance, September 30, 2016 $ (6.6 ) $ (73.6 ) $ (80.2 ) The following table shows the components and reclassifications to net income of AOCI which is included in Partners' Capital on the Condensed Consolidated Balance Sheets for the nine months ended September 30, 2017 (in millions): Cash Flow Hedges Pension and Other Postretirement Costs Total Beginning balance, January 1, 2017 $ (6.0 ) $ (74.1 ) $ (80.1 ) Loss recorded in AOCI (1.5 ) — (1.5 ) Reclassifications: Interest expense 1.9 — 1.9 Pension and other postretirement benefit costs — 0.8 0.8 Ending balance, September 30, 2017 $ (5.6 ) $ (73.3 ) $ (78.9 ) The following table shows the components and reclassifications to net income of AOCI which is included in Partners' Capital on the Condensed Consolidated Balance Sheets for the nine months ended September 30, 2016 (in millions): Cash Flow Hedges Pension and Other Postretirement Costs Total Beginning balance, January 1, 2016 $ (8.4 ) $ (75.9 ) $ (84.3 ) Reclassifications: Interest expense 1.8 — 1.8 Pension and other postretirement benefit costs — 2.3 2.3 Ending balance, September 30, 2016 $ (6.6 ) $ (73.6 ) $ (80.2 )

Other Comprehensive Income (O27

Other Comprehensive Income (OCI) and Fair Value Measurements Financial Assets and Liabilities (Tables)	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value, by Balance Sheet Grouping	The carrying amounts and estimated fair values of the Partnership's financial assets and liabilities which were not recorded at fair value on the Condensed Consolidated Balance Sheets as of September 30, 2017 , and December 31, 2016 , were as follows (in millions): As of September 30, 2017 Estimated Fair Value Financial Assets Carrying Amount Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 22.6 $ 22.6 $ — $ — $ 22.6 Financial Liabilities Long-term debt $ 3,586.7 (1) $ — $ 3,792.1 $ — $ 3,792.1 (1) The carrying amount of long-term debt excludes an $8.2 million long-term capital lease obligation and $9.2 million of unamortized debt issuance costs. As of December 31, 2016 Estimated Fair Value Financial Assets Carrying Amount Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 4.6 $ 4.6 $ — $ — $ 4.6 Financial Liabilities Long-term debt $ 3,558.9 (1) $ — $ 3,709.2 $ — $ 3,709.2 (1) The carrying amount of long-term debt excludes an $8.6 million long-term capital lease obligation and $9.5 million

Cash Distributions and Net In28

Cash Distributions and Net Income per Unit (Tables)	9 Months Ended
Cash Distributions and Net Income per Unit (Tables)	Sep. 30, 2017
Partners' Capital Notes [Abstract]
Distributions Made to Limited Partner, by Distribution	The following table provides a reconciliation of net income and the assumed allocation of net income to the common units for purposes of computing net income per unit for the three months ended September 30, 2017 (in millions, except per unit data): Total Common Units General Partner and IDRs Net income $ 69.8 Declared distribution 25.5 $ 25.0 $ 0.5 Assumed allocation of undistributed net loss 44.3 43.4 0.9 Assumed allocation of net income attributable to limited $ 69.8 $ 68.4 $ 1.4 Weighted-average units outstanding 250.3 Net income per unit $ 0.27 The following table provides a reconciliation of net income and the assumed allocation of net income to the common units for purposes of computing net income per unit for the three months ended September 30, 2016 (in millions, except per unit data): Total Common Units General Partner and IDRs Net income $ 47.3 Declared distribution 25.5 $ 25.0 $ 0.5 Assumed allocation of undistributed net income 21.8 21.4 0.4 Assumed allocation of net income attributable to limited $ 47.3 $ 46.4 $ 0.9 Weighted-average units outstanding 250.3 Net income per unit $ 0.19 The following table provides a reconciliation of net income and the assumed allocation of net income to the common units for purposes of computing net income per unit for the nine months ended September 30, 2017 (in millions, except per unit data): Total Common Units General Partner and IDRs Net income $ 212.8 Declared distribution 76.6 $ 75.1 $ 1.5 Assumed allocation of undistributed net income 136.2 133.5 2.7 Assumed allocation of net income attributable to limited $ 212.8 $ 208.6 $ 4.2 Weighted-average units outstanding 250.3 Net income per unit $ 0.83 The following table provides a reconciliation of net income and the assumed allocation of net income to the common units for purposes of computing net income per unit for the nine months ended September 30, 2016 (in millions, except per unit data): Total Common Units General Partner and IDRs Net income $ 214.0 Declared distribution 76.6 $ 75.1 $ 1.5 Assumed allocation of undistributed net income 137.4 134.7 2.7 Assumed allocation of net income attributable to limited $ 214.0 $ 209.8 $ 4.2 Weighted-average units outstanding 250.3 Net income per unit $ 0.84

Financing (Tables)

Financing (Tables)	9 Months Ended
Financing (Tables)	Sep. 30, 2017
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	For the nine months ended September 30, 2017 and 2016 , the Partnership completed the following debt issuances (in millions, except interest rates): Date of Issuance Issuing Subsidiary Amount of Issuance Purchaser Discounts and Expenses Net Proceeds Interest Rate Maturity Date Interest Payable January 2017 Boardwalk Pipelines $ 500.0 $ 6.0 $ 494.0 (1) 4.45% July 15, 2027 January 15 and July 15 May 2016 Boardwalk Pipelines $ 550.0 $ 10.9 $ 539.1 (2) 5.95% June 1, 2026 June 1 and December 1 (1) The net proceeds of this offering were used to retire the outstanding $275.0 million aggregate principal amount of Gulf South's 6.30% notes due 2017 (Gulf South 2017 Notes) and to fund growth capital expenditures. (2) The net proceeds of this offering were used to retire the outstanding $250.0 million aggregate principal amount of Boardwalk Pipelines 5.875% notes due 2016 and the outstanding $300.0 million aggregate principal amount of Boardwalk Pipelines 5.50%

Employee Benefits (Tables)

Employee Benefits (Tables)	9 Months Ended
Employee Benefits (Tables)	Sep. 30, 2017
Retirement Benefits [Abstract]
Schedule of Net Benefit Costs	Components of net periodic benefit cost for both the Retirement Plans and PBOP for the three months ended September 30, 2017 and 2016 , were as follows (in millions): Retirement Plans PBOP For the For the 2017 2016 2017 2016 Service cost $ 0.8 $ 0.9 $ — $ 0.1 Interest cost 1.2 1.2 0.4 0.5 Expected return on plan assets (2.0 ) (2.0 ) (1.1 ) (1.2 ) Amortization of prior service credit — — — (0.2 ) Amortization of unrecognized net loss 0.4 0.6 — — Settlement charge 0.4 0.7 — — Net periodic benefit cost $ 0.8 $ 1.4 $ (0.7 ) $ (0.8 ) Components of net periodic benefit cost for both the Retirement Plans and PBOP for the nine months ended September 30, 2017 and 2016 , were as follows (in millions): Retirement Plans PBOP For the For the 2017 2016 2017 2016 Service cost $ 2.6 $ 2.7 $ 0.1 $ 0.3 Interest cost 3.5 3.6 1.2 1.5 Expected return on plan assets (5.9 ) (6.0 ) (3.3 ) (3.6 ) Amortization of prior service credit — — — (0.7 ) Amortization of unrecognized net loss 1.3 1.8 — — Settlement charge 1.5 2.7 — — Net periodic benefit cost $ 3.0 $ 4.8 $ (2.0 ) $ (2.5 )

Supplemental Disclosure of Ca31

Supplemental Disclosure of Cash Flow Information (Tables)	9 Months Ended
Supplemental Disclosure of Cash Flow Information (Tables)	Sep. 30, 2017
Supplemental Cash Flow Elements [Abstract]
Schedule of Cash Flow, Supplemental Disclosures	Supplemental Disclosure of Cash Flow Information (in millions): For the 2017 2016 Cash paid during the period for: Interest (net of amount capitalized) $ 125.8 $ 122.3 Non-cash adjustments: Accounts payable and property, plant and equipment 66.6 81.0

Guarantee of Securities of Su32

Guarantee of Securities of Subsidiaries (Tables)	9 Months Ended
Guarantee of Securities of Subsidiaries (Tables)	Sep. 30, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed Consolidating Balance Sheet	The Partnership has provided the following condensed consolidating financial information in accordance with Regulation S-X Rule 3-10, Financial Statements of Guarantors and Issuers of Guaranteed Securities Registered or Being Registered . Condensed Consolidating Balance Sheets as of September 30, 2017 (Millions) Assets Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Cash and cash equivalents $ 0.4 $ 15.1 $ 7.1 $ — $ 22.6 Receivables — — 108.2 — 108.2 Receivables - affiliate — — 6.9 (6.9 ) — Gas and liquids stored underground — — 5.6 — 5.6 Prepayments 0.4 — 19.4 — 19.8 Advances to affiliates — 1.4 22.4 (23.8 ) — Other current assets — — 8.2 (1.2 ) 7.0 Total current assets 0.8 16.5 177.8 (31.9 ) 163.2 Investment in consolidated subsidiaries 2,602.8 6,665.8 — (9,268.6 ) — Property, plant and equipment, gross 0.6 — 10,674.1 — 10,674.7 Less–accumulated depreciation and amortization 0.6 — 2,542.5 — 2,543.1 Property, plant and equipment, net — — 8,131.6 — 8,131.6 Advances to affiliates – noncurrent 2,082.4 886.4 373.4 (3,342.2 ) — Other noncurrent assets — 3.4 464.1 (0.2 ) 467.3 Total other assets 2,082.4 889.8 837.5 (3,342.4 ) 467.3 Total Assets $ 4,686.0 $ 7,572.1 $ 9,146.9 $ (12,642.9 ) $ 8,762.1 Liabilities and Partners' Capital Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Payables $ 0.1 $ 0.2 $ 87.6 $ — $ 87.9 Payable to affiliates 1.5 — 6.9 (6.9 ) 1.5 Advances from affiliates — 22.4 1.4 (23.8 ) — Other current liabilities 0.2 29.9 174.6 (1.4 ) 203.3 Total current liabilities 1.8 52.5 270.5 (32.1 ) 292.7 Long-term debt and capital lease obligation — 2,461.0 1,124.7 — 3,585.7 Payable to affiliate - noncurrent 16.0 — — — 16.0 Advances from affiliates - noncurrent — 2,455.8 886.4 (3,342.2 ) — Other noncurrent liabilities — — 199.5 — 199.5 Total other liabilities and deferred credits 16.0 2,455.8 1,085.9 (3,342.2 ) 215.5 Total partners' capital 4,668.2 2,602.8 6,665.8 (9,268.6 ) 4,668.2 Total Liabilities and Partners' Capital $ 4,686.0 $ 7,572.1 $ 9,146.9 $ (12,642.9 ) $ 8,762.1 Condensed Consolidating Balance Sheets as of December 31, 2016 (Millions) Assets Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Cash and cash equivalents $ 0.6 $ 1.8 $ 2.2 $ — $ 4.6 Receivables — — 139.8 — 139.8 Receivables - affiliate — — 7.0 (7.0 ) — Gas and liquids stored underground — — 1.3 — 1.3 Prepayments 0.4 — 17.3 — 17.7 Advances to affiliates — 72.9 102.7 (175.6 ) — Other current assets — — 13.9 (3.1 ) 10.8 Total current assets 1.0 74.7 284.2 (185.7 ) 174.2 Investment in consolidated subsidiaries 2,423.2 6,653.6 — (9,076.8 ) — Property, plant and equipment, gross 0.6 — 10,326.7 — 10,327.3 Less–accumulated depreciation and amortization 0.6 — 2,333.2 — 2,333.8 Property, plant and equipment, net — — 7,993.5 — 7,993.5 Advances to affiliates – noncurrent 2,125.0 435.0 229.3 (2,789.3 ) — Other noncurrent assets — 3.3 466.8 — 470.1 Total other assets 2,125.0 438.3 696.1 (2,789.3 ) 470.1 Total Assets $ 4,549.2 $ 7,166.6 $ 8,973.8 $ (12,051.8 ) $ 8,637.8 Liabilities and Partners' Capital Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Payables $ 0.9 $ 0.2 $ 136.4 $ — $ 137.5 Payable to affiliates 1.4 — 7.0 (7.0 ) 1.4 Advances from affiliates — 102.7 72.9 (175.6 ) — Other current liabilities — 21.8 175.3 (3.1 ) 194.0 Total current liabilities 2.3 124.7 391.6 (185.7 ) 332.9 Long-term debt and capital lease obligation — 2,264.4 1,293.6 — 3,558.0 Payable to affiliate - noncurrent 16.0 — — — 16.0 Advances from affiliates - noncurrent — 2,354.3 435.0 (2,789.3 ) — Other noncurrent liabilities — — 200.0 — 200.0 Total other liabilities and deferred credits 16.0 2,354.3 635.0 (2,789.3 ) 216.0 Total partners' capital 4,530.9 2,423.2 6,653.6 (9,076.8 ) 4,530.9 Total Liabilities and Partners' Capital $ 4,549.2 $ 7,166.6 $ 8,973.8 $ (12,051.8 ) $ 8,637.8
Condensed Consolidating Statements of Income	Condensed Consolidating Statements of Income for the Three Months Ended September 30, 2017 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Operating Revenues: Transportation $ — $ — $ 295.4 $ (22.5 ) $ 272.9 Parking and lending — — 4.3 — 4.3 Storage — — 18.9 — 18.9 Other — — 4.4 — 4.4 Total operating revenues — — 323.0 (22.5 ) 300.5 Operating Costs and Expenses: Fuel and transportation — — 31.5 (22.5 ) 9.0 Operation and maintenance — — 49.0 — 49.0 Administrative and general (0.3 ) — 26.6 — 26.3 Other operating costs and expenses 0.4 — 105.0 — 105.4 Total operating costs and expenses 0.1 — 212.1 (22.5 ) 189.7 Operating (loss) income (0.1 ) — 110.9 — 110.8 Other Deductions (Income): Interest expense — 32.2 8.8 — 41.0 Interest (income) expense - affiliates, net (12.4 ) 11.0 1.4 — — Equity in earnings of subsidiaries (57.5 ) (100.7 ) — 158.2 — Miscellaneous other income, net — — (0.3 ) — (0.3 ) Total other (income) deductions (69.9 ) (57.5 ) 9.9 158.2 40.7 Income (loss) before income taxes 69.8 57.5 101.0 (158.2 ) 70.1 Income taxes — — 0.3 — 0.3 Net income (loss) $ 69.8 $ 57.5 $ 100.7 $ (158.2 ) $ 69.8 Condensed Consolidating Statements of Income for the Three Months Ended September 30, 2016 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Operating Revenues: Transportation $ — $ — $ 281.9 $ (22.3 ) $ 259.6 Parking and lending — — 5.1 (0.2 ) 4.9 Storage — — 23.4 — 23.4 Other — — 15.4 — 15.4 Total operating revenues — — 325.8 (22.5 ) 303.3 Operating Costs and Expenses: Fuel and transportation — — 41.6 (22.5 ) 19.1 Operation and maintenance — — 52.1 — 52.1 Administrative and general — — 34.4 — 34.4 Other operating costs and expenses 0.1 — 103.9 — 104.0 Total operating costs and expenses 0.1 — 232.0 (22.5 ) 209.6 Operating (loss) income (0.1 ) — 93.8 — 93.7 Other Deductions (Income): Interest expense — 34.6 13.8 — 48.4 Interest (income) expense - affiliates, net (9.7 ) 11.7 (2.0 ) — — Interest income — — (0.1 ) — (0.1 ) Equity in earnings of subsidiaries (37.7 ) (84.0 ) — 121.7 — Miscellaneous other income, net — — (1.9 ) — (1.9 ) Total other (income) deductions (47.4 ) (37.7 ) 9.8 121.7 46.4 Income (loss) before income taxes 47.3 37.7 84.0 (121.7 ) 47.3 Income taxes — — — — — Net income (loss) $ 47.3 $ 37.7 $ 84.0 $ (121.7 ) $ 47.3 Condensed Consolidating Statements of Income for the Nine Months Ended September 30, 2017 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Operating Revenues: Transportation $ — $ — $ 936.5 $ (66.3 ) $ 870.2 Parking and lending — — 17.8 (0.2 ) 17.6 Storage — — 62.2 — 62.2 Other — — 35.1 — 35.1 Total operating revenues — — 1,051.6 (66.5 ) 985.1 Operating Costs and Expenses: Fuel and transportation — — 109.2 (66.5 ) 42.7 Operation and maintenance — — 141.0 — 141.0 Administrative and general (0.3 ) — 95.4 — 95.1 Other operating costs and expenses 0.5 — 363.0 — 363.5 Total operating costs and expenses 0.2 — 708.6 (66.5 ) 642.3 Operating (loss) income (0.2 ) — 343.0 — 342.8 Other Deductions (Income): Interest expense — 97.6 33.5 — 131.1 Interest (income) expense - affiliates, net (34.6 ) 30.1 4.5 — — Interest income — (0.2 ) (0.1 ) — (0.3 ) Equity in earnings of subsidiaries (178.4 ) (305.9 ) — 484.3 — Miscellaneous other income, net — — (1.7 ) — (1.7 ) Total other (income) deductions (213.0 ) (178.4 ) 36.2 484.3 129.1 Income (loss) before income taxes 212.8 178.4 306.8 (484.3 ) 213.7 Income taxes — — 0.9 — 0.9 Net income (loss) $ 212.8 $ 178.4 $ 305.9 $ (484.3 ) $ 212.8 Condensed Consolidating Statements of Income for the Nine Months Ended September 30, 2016 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Operating Revenues: Transportation $ — $ — $ 901.0 $ (65.7 ) $ 835.3 Parking and lending — — 14.6 (1.2 ) 13.4 Storage — — 68.0 — 68.0 Other — — 37.9 — 37.9 Total operating revenues — — 1,021.5 (66.9 ) 954.6 Operating Costs and Expenses: Fuel and transportation — — 117.9 (66.9 ) 51.0 Operation and maintenance — — 143.8 — 143.8 Administrative and general 0.1 — 104.5 — 104.6 Other operating costs and expenses 0.3 — 310.3 — 310.6 Total operating costs and expenses 0.4 — 676.5 (66.9 ) 610.0 Operating (loss) income (0.4 ) — 345.0 — 344.6 Other Deductions (Income): Interest expense — 91.1 45.3 — 136.4 Interest (income) expense - affiliates, net (27.6 ) 35.2 (7.6 ) — — Interest income — — (0.3 ) — (0.3 ) Equity in earnings of subsidiaries (187.0 ) (313.3 ) — 500.3 — Miscellaneous other deductions (income), net 0.2 — (6.1 ) — (5.9 ) Total other (income) deductions (214.4 ) (187.0 ) 31.3 500.3 130.2 Income (loss) before income taxes 214.0 187.0 313.7 (500.3 ) 214.4 Income taxes — — 0.4 — 0.4 Net income (loss) $ 214.0 $ 187.0 $ 313.3 $ (500.3 ) $ 214.0
Condensed Consolidating Statements Of Comprehensive Income	Condensed Consolidating Statements of Comprehensive Income for the Three Months Ended September 30, 2017 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net income (loss) $ 69.8 $ 57.5 $ 100.7 $ (158.2 ) $ 69.8 Other comprehensive income (loss): Reclassification adjustment transferred to Net income from cash flow hedges 0.6 0.6 0.2 (0.8 ) 0.6 Pension and other postretirement benefit costs 0.1 0.1 0.1 (0.2 ) 0.1 Total Comprehensive Income (Loss) $ 70.5 $ 58.2 $ 101.0 $ (159.2 ) $ 70.5 Condensed Consolidating Statements of Comprehensive Income for the Three Months Ended September 30, 2016 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net income (loss) $ 47.3 $ 37.7 $ 84.0 $ (121.7 ) $ 47.3 Other comprehensive income (loss): Reclassification adjustment transferred to Net income from cash flow hedges 0.6 0.6 0.2 (0.8 ) 0.6 Pension and other postretirement benefit costs 0.6 0.6 0.6 (1.2 ) 0.6 Total Comprehensive Income (Loss) $ 48.5 $ 38.9 $ 84.8 $ (123.7 ) $ 48.5 Condensed Consolidating Statements of Comprehensive Income for the Nine Months Ended September 30, 2017 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net income (loss) $ 212.8 $ 178.4 $ 305.9 $ (484.3 ) $ 212.8 Other comprehensive income (loss): Loss on cash flow hedge (1.5 ) (1.5 ) — 1.5 (1.5 ) Reclassification adjustment transferred to Net income from cash flow hedges 1.9 1.9 0.5 (2.4 ) 1.9 Pension and other postretirement benefit costs 0.8 0.8 0.8 (1.6 ) 0.8 Total Comprehensive Income (Loss) $ 214.0 $ 179.6 $ 307.2 $ (486.8 ) $ 214.0 Condensed Consolidating Statements of Comprehensive Income for the Nine Months Ended September 30, 2016 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net income (loss) $ 214.0 $ 187.0 $ 313.3 $ (500.3 ) $ 214.0 Other comprehensive income (loss): Reclassification adjustment transferred to Net income from cash flow hedges 1.8 1.8 0.6 (2.4 ) 1.8 Pension and other postretirement benefit costs 2.3 2.3 2.3 (4.6 ) 2.3 Total Comprehensive Income (Loss) $ 218.1 $ 191.1 $ 316.2 $ (507.3 ) $ 218.1
Condensed Consolidating Statements of Cash Flows	Condensed Consolidating Statements of Cash Flow for the Nine Months Ended September 30, 2017 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net cash provided by (used in) operating activities $ 33.8 $ (117.0 ) $ 586.4 $ — $ 503.2 INVESTING ACTIVITIES: Capital expenditures — — (496.0 ) — (496.0 ) Proceeds from sale of operating assets — — 63.7 — 63.7 Advances to affiliates, net 42.6 (398.5 ) (377.4 ) 733.3 — Net cash provided by (used in) investing activities 42.6 (398.5 ) (809.7 ) 733.3 (432.3 ) FINANCING ACTIVITIES: Proceeds from long-term debt, net of issuance cost — 494.0 — — 494.0 Repayment of borrowings from long-term debt — (300.0 ) (275.0 ) — (575.0 ) Proceeds from borrowings on revolving credit agreement — — 505.0 — 505.0 Repayment of borrowings on revolving credit agreement — — (400.0 ) — (400.0 ) Principal payment of capital lease obligation — — (0.3 ) — (0.3 ) Advances from affiliates, net 0.1 334.8 398.5 (733.3 ) 0.1 Distributions paid (76.7 ) — — — (76.7 ) Net cash (used in) provided by financing activities (76.6 ) 528.8 228.2 (733.3 ) (52.9 ) (Decrease) increase in cash and cash equivalents (0.2 ) 13.3 4.9 — 18.0 Cash and cash equivalents at beginning of period 0.6 1.8 2.2 — 4.6 Cash and cash equivalents at end of period $ 0.4 $ 15.1 $ 7.1 $ — $ 22.6 Condensed Consolidating Statements of Cash Flow for the Nine Months Ended September 30, 2016 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net cash provided by (used in) operating activities $ 27.3 $ (108.3 ) $ 535.2 $ — $ 454.2 INVESTING ACTIVITIES: Capital expenditures — — (432.4 ) — (432.4 ) Proceeds from sale of operating assets — — 0.2 — 0.2 Advances to affiliates, net 49.7 (16.8 ) 256.5 (289.4 ) — Net cash provided by (used in) investing activities 49.7 (16.8 ) (175.7 ) (289.4 ) (432.2 ) FINANCING ACTIVITIES: Proceeds from long-term debt, net of issuance cost — 539.1 — — 539.1 Proceeds from borrowings on revolving credit agreement — — 255.0 — 255.0 Repayment of borrowings on revolving credit agreement, including financing fees — (0.8 ) (630.0 ) — (630.8 ) Principal payment of capital lease obligation — — (0.3 ) — (0.3 ) Advances from affiliates, net — (306.2 ) 16.8 289.4 — Distributions paid (76.7 ) — — — (76.7 ) Net cash (used in) provided by financing activities (76.7 ) 232.1 (358.5 ) 289.4 86.3 Increase in cash and cash equivalents 0.3 107.0 1.0 — 108.3 Cash and cash equivalents at beginning of period — 0.3 2.8 — 3.1 Cash and cash equivalents at end of period $ 0.3 $ 107.3 $ 3.8 $ — $ 111.4

Basis of Presentation (Details)

Basis of Presentation (Details) - shares shares in Millions	Oct. 27, 2017	Sep. 30, 2017	Sep. 30, 2016
Percent of General Partner Interest Owned by Holding Company (in hundredths)		2.00%	2.00%
Subsequent Event
Number of the Partnership's common units owned by holding company (in units)	125.6
Percent of General Partner Interest Owned by Holding Company (in hundredths)	2.00%
Percentage of Partnership's Equity Interests Owned by Holding Company (in hundredths)	51.00%

Asset Disposition and Impairm34

Asset Disposition and Impairments (Details) - USD ($) $ in Millions	May 09, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Property, Plant and Equipment Assets Held-for-sale Disclosure [Abstract]
Proceeds from Sale of Property, Plant, and Equipment	$ 63.6
Loss on Sale of Assets and Asset Impairment Charges	$ 47.1	$ 0	$ (0.1)	$ 47.1	$ (0.1)

Gas and Liquids Stored Underg35

Gas and Liquids Stored Underground and Gas and NGLs Receivables and Payables (Details) MMBbls in Millions, MMBTU in Millions, $ in Millions	Sep. 30, 2017USD ($)$ / MMBTUMMBTUMMBbls	Dec. 31, 2016MMBTUMMBbls
Gas Balancing Arrangements [Abstract]
Gas Balancing Volume Amount (in MMBtu) \| MMBTU	8.8	13.6
Average Market Price of Gas Assumed \| $ / MMBTU	2.86
Gas Imbalance to Subsidiaries Asset Liability \| $	$ 25.1
Natural Gas Liquids Balancing Volume (in MMBbls) (Less than) \| MMBbls	0	0.1

Other Comprehensive Income (O36

Other Comprehensive Income (OCI) and Fair Value Measurements OCI (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Assets, Fair Value Disclosure, Recurring	$ 0		$ 0		$ 0
Liabilities, Fair Value Disclosure, Recurring	0		0		$ 0
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss) (beginning)			(80.1)
Loss recorded in accumulated other comprehensive loss	0	$ 0	(1.5)	$ 0
Interest expense	41	48.4	131.1	136.4
Pension and other postretirement benefit costs	0.1	0.6	0.8	2.3
Accumulated other comprehensive income (loss) (ending)	(78.9)		(78.9)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest expense	0.6	0.6	1.9	1.8
Accumulated Net Gain (Loss) from Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cash Flow Hedge Loss to be Reclassified within Twelve Months			(1.5)
Accumulated other comprehensive income (loss) (beginning)	(6.2)	(7.2)	(6)	(8.4)
Accumulated other comprehensive income (loss) (ending)	(5.6)	(6.6)	(5.6)	(6.6)
Accumulated Net Gain (Loss) from Cash Flow Hedges \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest expense	0.6	0.6	1.9	1.8
Accumulated Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss) (beginning)	(73.4)	(74.2)	(74.1)	(75.9)
Pension and other postretirement benefit costs	0.1	0.6	0.8	2.3
Accumulated other comprehensive income (loss) (ending)	(73.3)	(73.6)	(73.3)	(73.6)
Accumulated Other Comp Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss) (beginning)	(79.6)	(81.4)	(80.1)	(84.3)
Pension and other postretirement benefit costs	0.1	0.6	0.8	2.3
Accumulated other comprehensive income (loss) (ending)	$ (78.9)	$ (80.2)	$ (78.9)	$ (80.2)

Other Comprehensive Income (O37

Other Comprehensive Income (OCI) and Fair Value Measurements Financial Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2017		Dec. 31, 2016
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and Cash Equivalents - Fair Value	$ 22.6		$ 4.6
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Debt Instrument, Fair Value Disclosure	3,792.1		3,709.2
Capital Lease Obligations, Noncurrent	8.2		8.6
Unamortized Debt Issuance Expense	9.2		9.5
Carrying Amount
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and Cash Equivalents - Fair Value	22.6		4.6
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Debt Instrument, Fair Value Disclosure	3,586.7	[1]	3,558.9	[2]
Fair Value \| Fair Value, Inputs, Level 1
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and Cash Equivalents - Fair Value	22.6		4.6
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Debt Instrument, Fair Value Disclosure	0		0
Fair Value \| Fair Value, Inputs, Level 2
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and Cash Equivalents - Fair Value	0		0
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Debt Instrument, Fair Value Disclosure	3,792.1		3,709.2
Fair Value \| Fair Value, Inputs, Level 3
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and Cash Equivalents - Fair Value	0		0
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Debt Instrument, Fair Value Disclosure	0		0
Line of Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Line of Credit	$ 285		$ 180

[1]	The carrying amount of long-term debt excludes an $8.2 million long-term capital lease obligation and $9.2 million
[2]	The carrying amount of long-term debt excludes an $8.6 million long-term capital lease obligation and $9.5 million

Commitments and Contingencies L

Commitments and Contingencies Legal Proceedings and Settlements (Details) $ in Millions	9 Months Ended
	Sep. 30, 2017defendant	Sep. 30, 2016USD ($)
Loss Contingencies [Line Items]
Litigation Settlement, Amount Awarded from Other Party \| $		$ 12.7
Southeast Louisiana Flood Protection Litigation
Loss Contingencies [Line Items]
Loss Contingency, Approximate Number of Defendants (in ones) \| defendant	100

Environmental and Safety Matter

Environmental and Safety Matters (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Accrual for Environmental Loss Contingencies	$ 5.1	$ 5
Number of years the related expenditures are expected to cover assessment and remediation costs (in years)	5 years
Accrued Environmental Loss Contingencies, Current	$ 1.1	1.7
Accrued Environmental Loss Contingencies, Noncurrent	$ 4	$ 3.3

Commitments and Contingencies C

Commitments and Contingencies Commitments for Construction (Details) $ in Millions	Sep. 30, 2017USD ($)
Commitments and Contingencies Disclosure [Abstract]
Purchase Commitment, Remaining Minimum Amount Committed	$ 248.1

Cash Distributions and Net In41

Cash Distributions and Net Income per Unit (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Oct. 30, 2017	Oct. 27, 2017
Reconciliation And Allocation of Net Income By Class of Stock [Line Items]
Cash distribution declared and paid to common units per common unit (in dollars per unit)	$ 0.10	$ 0.10	$ 0.30	$ 0.30
Percent of General Partner Interest Owned by Holding Company (in hundredths)	2.00%	2.00%	2.00%	2.00%
Net income	$ 69.8	$ 47.3	$ 212.8	$ 214
Declared distribution	25.5	25.5	76.6	76.6
Assumed allocation of undistributed net income	44.3	21.8	136.2	137.4
Assumed allocation of net income attributable to limited partner unitholders and general partner	$ 69.8	$ 47.3	$ 212.8	$ 214
Weighted-average units outstanding (in units)	250.3	250.3	250.3	250.3
Net income per unit (in dollars per unit)	$ 0.27	$ 0.19	$ 0.83	$ 0.84
Common Units
Reconciliation And Allocation of Net Income By Class of Stock [Line Items]
Declared distribution	$ 25	$ 25	$ 75.1	$ 75.1
Assumed allocation of undistributed net income	43.4	21.4	133.5	134.7
Assumed allocation of net income attributable to limited partner unitholders and general partner	$ 68.4	$ 46.4	$ 208.6	$ 209.8
Weighted-average units outstanding (in units)	250.3	250.3	250.3	250.3
Net income per unit (in dollars per unit)	$ 0.27	$ 0.19	$ 0.83	$ 0.84
General Partner and IDRs
Reconciliation And Allocation of Net Income By Class of Stock [Line Items]
Declared distribution	$ 0.5	$ 0.5	$ 1.5	$ 1.5
Assumed allocation of undistributed net income	0.9	0.4	2.7	2.7
Assumed allocation of net income attributable to limited partner unitholders and general partner	$ 1.4	$ 0.9	$ 4.2	$ 4.2
Subsequent Event
Reconciliation And Allocation of Net Income By Class of Stock [Line Items]
Percent of General Partner Interest Owned by Holding Company (in hundredths)						2.00%
Dividends Payable, Amount Per Share					$ 0.10

Financing - Debt (Details)

Financing - Debt (Details) - USD ($) $ in Millions		Feb. 01, 2017	Nov. 15, 2016	Aug. 31, 2017	Jan. 31, 2017	May 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Oct. 30, 2017	Dec. 31, 2016
Debt Instruments [Abstract]
Repayments of Unsecured Debt							$ 575	$ 0
Unsecured Debt
Debt Instruments [Abstract]
Long-term Debt, Gross							$ 3,300			$ 3,400
Debt, Weighted-Average Interest Rate							5.18%			5.46%
Short-term Debt, Refinanced, Amount							$ 185
Debt Instrument, Covenant Compliance							At September 30, 2017, Boardwalk Pipelines and its operating subsidiaries were in compliance with their debt covenants.
Unsecured Debt \| Boardwalk Pipelines 4.45% Notes Due 2027
Debt Instruments [Abstract]
Debt Instrument, Issuance Date					Jan. 31, 2017
Debt Instrument, Face Amount					$ 500
Payments of Debt Issuance Costs					6
Proceeds from Debt, Net of Issuance Costs	[1]				$ 494
Debt Instrument, Interest Rate, Stated Percentage					4.45%
Debt Instrument, Maturity Date					Jul. 15, 2027
Unsecured Debt \| Boardwalk Pipelines 5.95% Notes Due 2026
Debt Instruments [Abstract]
Debt Instrument, Issuance Date						May 31, 2016
Debt Instrument, Face Amount						$ 550
Payments of Debt Issuance Costs						10.9
Proceeds from Debt, Net of Issuance Costs	[2]					$ 539.1
Debt Instrument, Interest Rate, Stated Percentage						5.95%
Debt Instrument, Maturity Date						Jun. 1, 2026
Unsecured Debt \| Gulf South 6.30% Notes Due 2017
Debt Instruments [Abstract]
Debt Instrument, Interest Rate, Stated Percentage				6.30%
Repayments of Unsecured Debt				$ 275
Unsecured Debt \| Boardwalk Pipelines 5.875% Notes Due 2016
Debt Instruments [Abstract]
Debt Instrument, Interest Rate, Stated Percentage			5.875%
Repayments of Unsecured Debt			$ 250
Unsecured Debt \| Boardwalk Pipelines 5.50% Notes Due 2017
Debt Instruments [Abstract]
Debt Instrument, Interest Rate, Stated Percentage		5.50%
Repayments of Unsecured Debt		$ 300
Line of Credit
Debt Instruments [Abstract]
Debt, Weighted-Average Interest Rate							2.49%			1.96%
Line of Credit Facility [Abstract]
Long-term Line of Credit							$ 285			$ 180
Line of Credit Facility, Covenant Compliance							The Partnership and its subsidiaries were in compliance with all covenant requirements under the revolving credit facility as of September 30, 2017.
Line of Credit \| Amendment No. 1 Credit Agreement - 2016
Line of Credit Facility [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity							$ 1,500
Line of Credit \| Amendment No. 2 Credit Agreement - 2017
Line of Credit Facility [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity							$ 1,475
Subordinated Debt
Debt Instruments [Abstract]
Debt Instrument, Maturity Date							Dec. 31, 2018
Subordinated Loan Agreement Maximum Borrowing Capacity							$ 300
Subsequent Event \| Subordinated Debt
Debt Instruments [Abstract]
Subordinated Debt									$ 0

[1]	The net proceeds of this offering were used to retire the outstanding $275.0 million aggregate principal amount of Gulf South's 6.30%
[2]	The net proceeds of this offering were used to retire the outstanding $250.0 million aggregate principal amount of Boardwalk Pipelines 5.875% notes due 2016 and the outstanding $300.0 million aggregate principal amount of Boardwalk Pipelines 5.50% notes due 2017 at their maturity.

Employee Benefits (Details)

Employee Benefits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Employee Benefits (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 3
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Defined Contribution Plan, Cost	2.7	$ 2.7	$ 8.1	$ 7.8
Retirement Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	0.8	0.9	2.6	2.7
Interest cost	1.2	1.2	3.5	3.6
Expected return on plan assets	(2)	(2)	(5.9)	(6)
Amortization of prior service credit	0	0	0	0
Amortization of unrecognized net loss	0.4	0.6	1.3	1.8
Settlement charge	0.4	0.7	1.5	2.7
Net periodic benefit cost	0.8	1.4	3	4.8
PBOP
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	0	0.1	0.1	0.3
Interest cost	0.4	0.5	1.2	1.5
Expected return on plan assets	(1.1)	(1.2)	(3.3)	(3.6)
Amortization of prior service credit	0	(0.2)	0	(0.7)
Amortization of unrecognized net loss	0	0	0	0
Settlement charge	0	0	0	0
Net periodic benefit cost	$ (0.7)	$ (0.8)	$ (2)	$ (2.5)

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	$ 1.7	$ 1.8	$ 5	$ 5.3
Percent of General Partner Interest Owned by Holding Company (in hundredths)	2.00%	2.00%	2.00%	2.00%
Boardwalk GP, LP
Related Party Transaction [Line Items]
Cash dividends paid to parent company	$ 13.1	$ 13.2	$ 39.2	$ 39.5

Supplemental Disclosure of Ca45

Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash paid during the period for:
Interest (net of amount capitalized)	$ 125.8	$ 122.3
Non-cash adjustments:
Accounts payable and property, plant and equipment	$ 66.6	$ 81

Guarantee of Securities of Su46

Guarantee of Securities of Subsidiaries Balance Sheets (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Subsidiary, Cumulative Percentage Ownership after All Transactions	100.00%
Equity Restrictions	$ 0	$ 0
Other Restricted Assets	$ 0	0
Restriction to Transfer Funds	Boardwalk Pipelines (Subsidiary Issuer) has issued securities which have been fully and unconditionally guaranteed by the Partnership (Parent Guarantor). The Subsidiary Issuer is 100% owned by the Parent Guarantor. The Partnership's subsidiaries had no significant restrictions on their ability to pay distributions or make loans to the Partnership except as noted in the debt covenants and had no restricted assets at September 30, 2017, and December 31, 2016.
Assets
Cash and cash equivalents	$ 22.6	4.6	$ 111.4	$ 3.1
Receivables	108.2	139.8
Receivables - affiliate	0	0
Gas and liquids stored underground	5.6	1.3
Prepayments	19.8	17.7
Advances to affiliates	0	0
Other current assets	7	10.8
Total current assets	163.2	174.2
Investment in consolidated subsidiaries	0	0
Property, plant and equipment, gross	10,674.7	10,327.3
Less—accumulated depreciation and amortization	2,543.1	2,333.8
Property, plant and equipment, net	8,131.6	7,993.5
Advances to affiliates - noncurrent	0	0
Other noncurrent assets	467.3	470.1
Total other assets	467.3	470.1
Total Assets	8,762.1	8,637.8
Liabilities and Partners' Capital
Payables	87.9	137.5
Payable to affiliates	1.5	1.4
Advances from affiliates	0	0
Other current liabilities	203.3	194
Total current liabilities	292.7	332.9
Long-term debt and capital lease obligation	3,585.7	3,558
Payable to affiliate - noncurrent	16	16
Advances from affiliates - noncurrent	0	0
Other noncurrent liabilities	199.5	200
Total other liabilities and deferred credits	215.5	216
Total partners' capital	4,668.2	4,530.9
Total Liabilities and Partners' Capital	8,762.1	8,637.8
Reportable Legal Entities \| Parent Guarantor
Assets
Cash and cash equivalents	0.4	0.6	0.3	0
Receivables	0	0
Receivables - affiliate	0	0
Gas and liquids stored underground	0	0
Prepayments	0.4	0.4
Advances to affiliates	0	0
Other current assets	0	0
Total current assets	0.8	1
Investment in consolidated subsidiaries	2,602.8	2,423.2
Property, plant and equipment, gross	0.6	0.6
Less—accumulated depreciation and amortization	0.6	0.6
Property, plant and equipment, net	0	0
Advances to affiliates - noncurrent	2,082.4	2,125
Other noncurrent assets	0	0
Total other assets	2,082.4	2,125
Total Assets	4,686	4,549.2
Liabilities and Partners' Capital
Payables	0.1	0.9
Payable to affiliates	1.5	1.4
Advances from affiliates	0	0
Other current liabilities	0.2	0
Total current liabilities	1.8	2.3
Long-term debt and capital lease obligation	0	0
Payable to affiliate - noncurrent	16	16
Advances from affiliates - noncurrent	0	0
Other noncurrent liabilities	0	0
Total other liabilities and deferred credits	16	16
Total partners' capital	4,668.2	4,530.9
Total Liabilities and Partners' Capital	4,686	4,549.2
Reportable Legal Entities \| Subsidiary Issuer
Assets
Cash and cash equivalents	15.1	1.8	107.3	0.3
Receivables	0	0
Receivables - affiliate	0	0
Gas and liquids stored underground	0	0
Prepayments	0	0
Advances to affiliates	1.4	72.9
Other current assets	0	0
Total current assets	16.5	74.7
Investment in consolidated subsidiaries	6,665.8	6,653.6
Property, plant and equipment, gross	0	0
Less—accumulated depreciation and amortization	0	0
Property, plant and equipment, net	0	0
Advances to affiliates - noncurrent	886.4	435
Other noncurrent assets	3.4	3.3
Total other assets	889.8	438.3
Total Assets	7,572.1	7,166.6
Liabilities and Partners' Capital
Payables	0.2	0.2
Payable to affiliates	0	0
Advances from affiliates	22.4	102.7
Other current liabilities	29.9	21.8
Total current liabilities	52.5	124.7
Long-term debt and capital lease obligation	2,461	2,264.4
Payable to affiliate - noncurrent	0	0
Advances from affiliates - noncurrent	2,455.8	2,354.3
Other noncurrent liabilities	0	0
Total other liabilities and deferred credits	2,455.8	2,354.3
Total partners' capital	2,602.8	2,423.2
Total Liabilities and Partners' Capital	7,572.1	7,166.6
Reportable Legal Entities \| Non-Guarantor Subsidiaries
Assets
Cash and cash equivalents	7.1	2.2	3.8	2.8
Receivables	108.2	139.8
Receivables - affiliate	6.9	7
Gas and liquids stored underground	5.6	1.3
Prepayments	19.4	17.3
Advances to affiliates	22.4	102.7
Other current assets	8.2	13.9
Total current assets	177.8	284.2
Investment in consolidated subsidiaries	0	0
Property, plant and equipment, gross	10,674.1	10,326.7
Less—accumulated depreciation and amortization	2,542.5	2,333.2
Property, plant and equipment, net	8,131.6	7,993.5
Advances to affiliates - noncurrent	373.4	229.3
Other noncurrent assets	464.1	466.8
Total other assets	837.5	696.1
Total Assets	9,146.9	8,973.8
Liabilities and Partners' Capital
Payables	87.6	136.4
Payable to affiliates	6.9	7
Advances from affiliates	1.4	72.9
Other current liabilities	174.6	175.3
Total current liabilities	270.5	391.6
Long-term debt and capital lease obligation	1,124.7	1,293.6
Payable to affiliate - noncurrent	0	0
Advances from affiliates - noncurrent	886.4	435
Other noncurrent liabilities	199.5	200
Total other liabilities and deferred credits	1,085.9	635
Total partners' capital	6,665.8	6,653.6
Total Liabilities and Partners' Capital	9,146.9	8,973.8
Eliminations
Assets
Cash and cash equivalents	0	0	$ 0	$ 0
Receivables	0	0
Receivables - affiliate	(6.9)	(7)
Gas and liquids stored underground	0	0
Prepayments	0	0
Advances to affiliates	(23.8)	(175.6)
Other current assets	(1.2)	(3.1)
Total current assets	(31.9)	(185.7)
Investment in consolidated subsidiaries	(9,268.6)	(9,076.8)
Property, plant and equipment, gross	0	0
Less—accumulated depreciation and amortization	0	0
Property, plant and equipment, net	0	0
Advances to affiliates - noncurrent	(3,342.2)	(2,789.3)
Other noncurrent assets	(0.2)	0
Total other assets	(3,342.4)	(2,789.3)
Total Assets	(12,642.9)	(12,051.8)
Liabilities and Partners' Capital
Payables	0	0
Payable to affiliates	(6.9)	(7)
Advances from affiliates	(23.8)	(175.6)
Other current liabilities	(1.4)	(3.1)
Total current liabilities	(32.1)	(185.7)
Long-term debt and capital lease obligation	0	0
Payable to affiliate - noncurrent	0	0
Advances from affiliates - noncurrent	(3,342.2)	(2,789.3)
Other noncurrent liabilities	0	0
Total other liabilities and deferred credits	(3,342.2)	(2,789.3)
Total partners' capital	(9,268.6)	(9,076.8)
Total Liabilities and Partners' Capital	$ (12,642.9)	$ (12,051.8)

Guarantee of Securities of Su47

Guarantee of Securities of Subsidiaries Guarantee of Securities of Subsidiaries Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Operating Revenues:
Transportation	$ 272.9	$ 259.6	$ 870.2	$ 835.3
Parking and lending	4.3	4.9	17.6	13.4
Storage	18.9	23.4	62.2	68
Other	4.4	15.4	35.1	37.9
Total operating revenues	300.5	303.3	985.1	954.6
Operating Costs and Expenses:
Fuel and transportation	9	19.1	42.7	51
Operation and maintenance	49	52.1	141	143.8
Administrative and general	26.3	34.4	95.1	104.6
Other operating costs and expenses	105.4	104	363.5	310.6
Total operating costs and expenses	189.7	209.6	642.3	610
Operating (loss) income	110.8	93.7	342.8	344.6
Other Deductions (Income):
Interest expense	41	48.4	131.1	136.4
Interest expense - affiliates, net	0	0	0	0
Interest income	0	(0.1)	(0.3)	(0.3)
Equity in earnings of subsidiaries	0	0	0	0
Miscellaneous other deductions (income), net	(0.3)	(1.9)	(1.7)	(5.9)
Total other (income) deductions	40.7	46.4	129.1	130.2
Income (loss) before income taxes	70.1	47.3	213.7	214.4
Income taxes	0.3	0	0.9	0.4
Net income (loss)	69.8	47.3	212.8	214
Reportable Legal Entities \| Parent Guarantor
Operating Revenues:
Transportation	0	0	0	0
Parking and lending	0	0	0	0
Storage	0	0	0	0
Other	0	0	0	0
Total operating revenues	0	0	0	0
Operating Costs and Expenses:
Fuel and transportation	0	0	0	0
Operation and maintenance	0	0	0	0
Administrative and general	(0.3)	0	(0.3)	0.1
Other operating costs and expenses	0.4	0.1	0.5	0.3
Total operating costs and expenses	0.1	0.1	0.2	0.4
Operating (loss) income	(0.1)	(0.1)	(0.2)	(0.4)
Other Deductions (Income):
Interest expense	0	0	0	0
Interest income - affiliates, net	(12.4)	(9.7)	(34.6)	(27.6)
Interest income		0	0	0
Equity in earnings of subsidiaries	(57.5)	(37.7)	(178.4)	(187)
Miscellaneous other deductions (income), net	0	0	0	0.2
Total other (income) deductions	(69.9)	(47.4)	(213)	(214.4)
Income (loss) before income taxes	69.8	47.3	212.8	214
Income taxes	0	0	0	0
Net income (loss)	69.8	47.3	212.8	214
Reportable Legal Entities \| Subsidiary Issuer
Operating Revenues:
Transportation	0	0	0	0
Parking and lending	0	0	0	0
Storage	0	0	0	0
Other	0	0	0	0
Total operating revenues	0	0	0	0
Operating Costs and Expenses:
Fuel and transportation	0	0	0	0
Operation and maintenance	0	0	0	0
Administrative and general	0	0	0	0
Other operating costs and expenses	0	0	0	0
Total operating costs and expenses	0	0	0	0
Operating (loss) income	0	0	0	0
Other Deductions (Income):
Interest expense	32.2	34.6	97.6	91.1
Interest expense - affiliates, net	11	11.7	30.1	35.2
Interest income		0	(0.2)	0
Equity in earnings of subsidiaries	(100.7)	(84)	(305.9)	(313.3)
Miscellaneous other deductions (income), net	0	0	0	0
Total other (income) deductions	(57.5)	(37.7)	(178.4)	(187)
Income (loss) before income taxes	57.5	37.7	178.4	187
Income taxes	0	0	0	0
Net income (loss)	57.5	37.7	178.4	187
Reportable Legal Entities \| Non-Guarantor Subsidiaries
Operating Revenues:
Transportation	295.4	281.9	936.5	901
Parking and lending	4.3	5.1	17.8	14.6
Storage	18.9	23.4	62.2	68
Other	4.4	15.4	35.1	37.9
Total operating revenues	323	325.8	1,051.6	1,021.5
Operating Costs and Expenses:
Fuel and transportation	31.5	41.6	109.2	117.9
Operation and maintenance	49	52.1	141	143.8
Administrative and general	26.6	34.4	95.4	104.5
Other operating costs and expenses	105	103.9	363	310.3
Total operating costs and expenses	212.1	232	708.6	676.5
Operating (loss) income	110.9	93.8	343	345
Other Deductions (Income):
Interest expense	8.8	13.8	33.5	45.3
Interest income - affiliates, net		(2)		(7.6)
Interest expense - affiliates, net	1.4		4.5
Interest income		(0.1)	(0.1)	(0.3)
Equity in earnings of subsidiaries	0	0	0	0
Miscellaneous other deductions (income), net	(0.3)	(1.9)	(1.7)	(6.1)
Total other (income) deductions	9.9	9.8	36.2	31.3
Income (loss) before income taxes	101	84	306.8	313.7
Income taxes	0.3	0	0.9	0.4
Net income (loss)	100.7	84	305.9	313.3
Eliminations
Operating Revenues:
Transportation	(22.5)	(22.3)	(66.3)	(65.7)
Parking and lending	0	(0.2)	(0.2)	(1.2)
Storage	0	0	0	0
Other	0	0	0	0
Total operating revenues	(22.5)	(22.5)	(66.5)	(66.9)
Operating Costs and Expenses:
Fuel and transportation	(22.5)	(22.5)	(66.5)	(66.9)
Operation and maintenance	0	0	0	0
Administrative and general	0	0	0	0
Other operating costs and expenses	0	0	0	0
Total operating costs and expenses	(22.5)	(22.5)	(66.5)	(66.9)
Operating (loss) income	0	0	0	0
Other Deductions (Income):
Interest expense	0	0	0	0
Interest expense - affiliates, net	0	0	0	0
Interest income		0	0	0
Equity in earnings of subsidiaries	158.2	121.7	484.3	500.3
Miscellaneous other deductions (income), net	0	0	0	0
Total other (income) deductions	158.2	121.7	484.3	500.3
Income (loss) before income taxes	(158.2)	(121.7)	(484.3)	(500.3)
Income taxes	0	0	0	0
Net income (loss)	$ (158.2)	$ (121.7)	$ (484.3)	$ (500.3)

Guarantee of Securities of Su48

Guarantee of Securities of Subsidiaries Guarantee of Securities of Subsidiaries Statements of Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	$ 69.8	$ 47.3	$ 212.8	$ 214
Other comprehensive income (loss):
Loss on cash flow hedge	0	0	(1.5)	0
Reclassification adjustment transferred to Net income from cash flow hedges	0.6	0.6	1.9	1.8
Pension and other postretirement benefit costs	0.1	0.6	0.8	2.3
Total Comprehensive Income (Loss)	70.5	48.5	214	218.1
Reportable Legal Entities \| Parent Guarantor
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	69.8	47.3	212.8	214
Other comprehensive income (loss):
Loss on cash flow hedge			(1.5)
Reclassification adjustment transferred to Net income from cash flow hedges	0.6	0.6	1.9	1.8
Pension and other postretirement benefit costs	0.1	0.6	0.8	2.3
Total Comprehensive Income (Loss)	70.5	48.5	214	218.1
Reportable Legal Entities \| Subsidiary Issuer
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	57.5	37.7	178.4	187
Other comprehensive income (loss):
Loss on cash flow hedge			(1.5)
Reclassification adjustment transferred to Net income from cash flow hedges	0.6	0.6	1.9	1.8
Pension and other postretirement benefit costs	0.1	0.6	0.8	2.3
Total Comprehensive Income (Loss)	58.2	38.9	179.6	191.1
Reportable Legal Entities \| Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	100.7	84	305.9	313.3
Other comprehensive income (loss):
Loss on cash flow hedge			0
Reclassification adjustment transferred to Net income from cash flow hedges	0.2	0.2	0.5	0.6
Pension and other postretirement benefit costs	0.1	0.6	0.8	2.3
Total Comprehensive Income (Loss)	101	84.8	307.2	316.2
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	(158.2)	(121.7)	(484.3)	(500.3)
Other comprehensive income (loss):
Loss on cash flow hedge			1.5
Reclassification adjustment transferred to Net income from cash flow hedges	(0.8)	(0.8)	(2.4)	(2.4)
Pension and other postretirement benefit costs	(0.2)	(1.2)	(1.6)	(4.6)
Total Comprehensive Income (Loss)	$ (159.2)	$ (123.7)	$ (486.8)	$ (507.3)

Guarantee of Securities of Su49

Guarantee of Securities of Subsidiaries Guarantee of Securities of Subsidiaries Statements of Cash Flows (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Statement of Cash Flows
Net cash provided by (used in) operating activities	$ 503.2	$ 454.2
Investing Activities:
Capital expenditures	(496)	(432.4)
Proceeds from sale of operating assets	63.7	0.2
Advances to affiliates, net	0	0
Net cash used in investing activities	(432.3)	(432.2)
Financing Activities:
Proceeds from long-term debt, net of issuance cost	494	539.1
Repayment of borrowings from long-term debt	(575)	0
Proceeds from borrowings on revolving credit agreement	505	255
Repayment of borrowings on revolving credit agreement, including financing fees	(400)	(630.8)
Principal payment of capital lease obligation	(0.3)	(0.3)
Advances from affiliates, net	0.1	0
Distributions paid	(76.7)	(76.7)
Net cash (used in) provided by financing activities	(52.9)	86.3
(Decrease) increase in cash and cash equivalents	18	108.3
Cash and cash equivalents at beginning of period	4.6	3.1
Cash and cash equivalents at end of period	22.6	111.4
Reportable Legal Entities \| Parent Guarantor
Statement of Cash Flows
Net cash provided by (used in) operating activities	33.8	27.3
Investing Activities:
Capital expenditures	0	0
Proceeds from sale of operating assets	0	0
Advances to affiliates, net	42.6	49.7
Net cash used in investing activities	42.6	49.7
Financing Activities:
Proceeds from long-term debt, net of issuance cost	0	0
Repayment of borrowings from long-term debt	0
Proceeds from borrowings on revolving credit agreement	0	0
Repayment of borrowings on revolving credit agreement, including financing fees	0	0
Principal payment of capital lease obligation	0	0
Advances from affiliates, net	0.1	0
Distributions paid	(76.7)	(76.7)
Net cash (used in) provided by financing activities	(76.6)	(76.7)
(Decrease) increase in cash and cash equivalents	(0.2)	0.3
Cash and cash equivalents at beginning of period	0.6	0
Cash and cash equivalents at end of period	0.4	0.3
Reportable Legal Entities \| Subsidiary Issuer
Statement of Cash Flows
Net cash provided by (used in) operating activities	(117)	(108.3)
Investing Activities:
Capital expenditures	0	0
Proceeds from sale of operating assets	0	0
Advances to affiliates, net	(398.5)	(16.8)
Net cash used in investing activities	(398.5)	(16.8)
Financing Activities:
Proceeds from long-term debt, net of issuance cost	494	539.1
Repayment of borrowings from long-term debt	(300)
Proceeds from borrowings on revolving credit agreement	0	0
Repayment of borrowings on revolving credit agreement, including financing fees	0	(0.8)
Principal payment of capital lease obligation	0	0
Advances from affiliates, net	334.8	(306.2)
Distributions paid	0	0
Net cash (used in) provided by financing activities	528.8	232.1
(Decrease) increase in cash and cash equivalents	13.3	107
Cash and cash equivalents at beginning of period	1.8	0.3
Cash and cash equivalents at end of period	15.1	107.3
Reportable Legal Entities \| Non-Guarantor Subsidiaries
Statement of Cash Flows
Net cash provided by (used in) operating activities	586.4	535.2
Investing Activities:
Capital expenditures	(496)	(432.4)
Proceeds from sale of operating assets	63.7	0.2
Advances to affiliates, net	(377.4)	256.5
Net cash used in investing activities	(809.7)	(175.7)
Financing Activities:
Proceeds from long-term debt, net of issuance cost	0	0
Repayment of borrowings from long-term debt	(275)
Proceeds from borrowings on revolving credit agreement	505	255
Repayment of borrowings on revolving credit agreement, including financing fees	(400)	(630)
Principal payment of capital lease obligation	(0.3)	(0.3)
Advances from affiliates, net	398.5	16.8
Distributions paid	0	0
Net cash (used in) provided by financing activities	228.2	(358.5)
(Decrease) increase in cash and cash equivalents	4.9	1
Cash and cash equivalents at beginning of period	2.2	2.8
Cash and cash equivalents at end of period	7.1	3.8
Eliminations
Statement of Cash Flows
Net cash provided by (used in) operating activities	0	0
Investing Activities:
Capital expenditures	0	0
Proceeds from sale of operating assets	0	0
Advances to affiliates, net	733.3	(289.4)
Net cash used in investing activities	733.3	(289.4)
Financing Activities:
Proceeds from long-term debt, net of issuance cost	0	0
Repayment of borrowings from long-term debt	0
Proceeds from borrowings on revolving credit agreement	0	0
Repayment of borrowings on revolving credit agreement, including financing fees	0	0
Principal payment of capital lease obligation	0	0
Advances from affiliates, net	(733.3)	289.4
Distributions paid	0	0
Net cash (used in) provided by financing activities	(733.3)	289.4
(Decrease) increase in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	$ 0	$ 0