Boardwalk Pipeline Partners (BWP) 10-K 19 Feb 16 2015 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Feb. 19, 2016	Jun. 30, 2015
Entity Information [Line Items]
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
Document Type	10-K
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		250,296,782
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 1,807,744,283

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Current Assets:
Cash and cash equivalents	$ 3.1	$ 6.6
Receivables:
Trade, net	117.2	102.6
Other	12.3	8.3
Gas transportation receivables	5.6	9.1
Gas and liquids stored underground	10.7	4.1
Prepayments	16.9	14.5
Other current assets	4	4.4
Total current assets	169.8	149.6
Property, Plant and Equipment:
Natural gas transmission and other plant	9,504.7	9,250.1
Construction work in progress	201.9	105.5
Property, plant and equipment, gross	9,706.6	9,355.6
Less—accumulated depreciation and amortization	2,052.2	1,766.4
Property, plant and equipment, net	7,654.4	7,589.2
Other Assets:
Goodwill	237.4	237.4
Gas stored underground	97.6	86.4
Other	141.1	131.7
Total other assets	476.1	455.5
Total Assets	8,300.3	8,194.3
Payables:
Trade, net	99.1	51.7
Affiliates	1.3	1.5
Other	19.5	10.4
Gas payables	4.7	8.5
Accrued taxes, other	47.3	47.1
Accrued interest	39.7	47.4
Accrued payroll and employee benefits	33.2	26.3
Deferred income	6.9	1.9
Customer rate refunds	16.3	0
Other current liabilities	46.4	25.4
Total current liabilities	314.4	220.2
Long–term debt and capital lease obligation	3,459.3	3,677.2
Other Liabilities and Deferred Credits:
Pension liability	24.3	19.2
Asset retirement obligation	38.1	39.9
Provision for other asset retirement	57.2	60.5
Payable to affiliate	16	16
Other	64.3	59
Total other liabilities and deferred credits	$ 199.9	$ 194.6
Commitments and Contingencies
Partners’ Capital:
Common units – 250.3 million and 243.3 million units issued and outstanding as of December 31, 2015 and 2014	$ 4,326.2	$ 4,095.1
General partner	84.8	80
Accumulated other comprehensive loss	(84.3)	(72.8)
Total partners’ capital	4,326.7	4,102.3
Total Liabilities and Partners' Capital	$ 8,300.3	$ 8,194.3

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - shares shares in Millions	Dec. 31, 2015	Dec. 31, 2014
Common Units Issued	250.3	243.3
Common Units Outstanding	250.3	243.3

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Revenues:
Transportation	$ 1,091.1	$ 1,065.1	$ 1,028
Parking and lending	11.4	23.3	23.9
Storage	81.3	89.5	110.9
Other	65.4	55.9	42.8
Total operating revenues	1,249.2	1,233.8	1,205.6
Operating Costs and Expenses:
Fuel and transportation	99.3	124.7	97.2
Operation and maintenance	209.5	194.8	182.7
Administrative and general	130.4	125	117.4
Depreciation and amortization	323.7	288.7	271.6
Asset impairment	0.4	10.1	4.1
Goodwill impairment	0	0	51.5
Net gain on sale of operating assets	(0.5)	(1.1)	(29.5)
Taxes other than income taxes	90.6	93.5	96.1
Total operating costs and expenses	853.4	835.7	791.1
Operating income	395.8	398.1	414.5
Other Deductions (Income):
Interest expense	176.4	165.5	163.4
Interest income	(0.4)	(0.6)	(0.5)
Equity losses in unconsolidated affiliates	0	86.5	1.2
Miscellaneous other income	(2.7)	(0.5)	(0.3)
Total other deductions	173.3	250.9	163.8
Income before income taxes	222.5	147.2	250.7
Income taxes	0.5	0.4	0.5
Net Income	222	146.8	250.2
Net loss attributable to noncontrolling interests	0	(86.8)	(3.5)
Net income attributable to controlling interests	$ 222	$ 233.6	$ 253.7

CONSOLIDATED STATEMENTS OF INC5

CONSOLIDATED STATEMENTS OF INCOME Net Income Per Unit - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Common units
Basic net income per unit:
Basic net income per unit	$ 0.87	$ 0.94	$ 1
Weighted-average number of units outstanding - basic
Weighted-average number of units outstanding - basic	248.8	243.3	220.5
Diluted net income per unit:
Diluted net income per unit	$ 0	$ 0.94	$ 0.96
Weighted-average number of units outstanding - diluted
Weighted-average number of units outstanding - diluted	0	243.3	226.8
Distribution Made to Limited Partner, Distributions Paid, Per Unit	$ 0.40	$ 0.40	$ 2.13
Class B units
Basic net income per unit:
Basic net income per unit	$ 0	$ 0	$ 0.05
Weighted-average number of units outstanding - basic
Weighted-average number of units outstanding - basic	0	0	17.6
Diluted net income per unit:
Diluted net income per unit	$ 0	$ 0	$ 0.48
Weighted-average number of units outstanding - diluted
Weighted-average number of units outstanding - diluted	0	0	11.3
Distribution Made to Limited Partner, Distributions Paid, Per Unit	$ 0	$ 0	$ 0.90

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net income	$ 65.6	$ 38.3	$ 40.4	$ 77.7	$ 36.9	$ 28.4	$ 55.9	$ 25.6	$ 222	$ 146.8	$ 250.2
Other comprehensive income (loss):
(Loss) gain on cash flow hedges									0	(0.7)	1.6
Reclassification adjustment transferred to Net income from cash flow hedges									2.4	2.6	1.2
Pension and other postretirement benefit costs									(13.9)	(10.9)	0.7
Total Comprehensive Income									210.5	137.8	253.7
Comprehensive loss attributable to noncontrolling interests									0	(86.8)	(3.5)
Comprehensive income attributable to controlling interests									$ 210.5	$ 224.6	$ 257.2

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
OPERATING ACTIVITIES:
Net income	$ 222	$ 146.8	$ 250.2
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	323.7	288.7	271.6
Amortization of deferred costs	7.7	5.7	5.5
Asset impairment	0.4	10.1	4.1
Goodwill impairment	0	0	51.5
Net gain on sale of operating assets	(0.5)	(1.1)	(29.5)
Equity losses in unconsolidated affiliates	0	86.5	1.2
Changes in operating assets and liabilities:
Trade and other receivables	(18.6)	8.3	(10)
Other receivables, affiliates	0	1	0.5
Gas receivables and storage assets	(14.3)	(11.5)	18
Costs recoverable from customers	(0.3)	0.5	2.6
Other assets	(3.2)	5.8	(10.7)
Trade and other payables	39.4	(7.3)	(16.8)
Other payables, affiliates	(0.7)	0.2	0.7
Gas payables	(3.7)	(8.8)	0.5
Accrued liabilities	0.3	3.9	8.6
Other liabilities	24.2	(15.2)	(13.7)
Net cash provided by operating activities	576.4	513.6	534.3
INVESTING ACTIVITIES:
Capital expenditures	(374.5)	(404.4)	(294.8)
Proceeds from sale of operating assets	0.8	2.9	60.7
Proceeds from insurance and other recoveries	6.2	6.3	1.4
Advances to affiliates	0	0.1	0
Investment in unconsolidated affiliates	0	(20.5)	(76.7)
Distributions from unconsolidated affiliates	0	11.1	0
Acquisition of businesses, net of cash acquired	0	(294.7)	0
Net cash used in investing activities	(367.5)	(699.2)	(309.4)
FINANCING ACTIVITIES:
Proceeds from long-term debt, net of issuance cost	247.1	342.9	0
Repayment of borrowings from long-term debt and term loan	(725)	(25)	0
Proceeds from borrowings on revolving credit agreement	1,125	665	1,128
Repayment of borrowings on revolving credit agreement, including financing fees	(873.6)	(720)	(1,255)
Principal payment of capital lease obligation	(0.4)	(0.4)	(0.2)
Advances from affiliates	0.6	0.1	(2.8)
Distributions paid	(101.5)	(99.2)	(533.9)
Capital contributions from noncontrolling interests	0	8.2	87.1
Proceeds from sale of common units	113.1	0	368.7
Capital contributions from general partner	2.3	0	7.8
Distributions paid to noncontrolling interests	0	(7.9)	0
Net cash (used in) provided by financing activities	(212.4)	163.7	(200.3)
(Decrease) increase in cash and cash equivalents	(3.5)	(21.9)	24.6
Cash and cash equivalents at beginning of period	6.6	28.5	3.9
Cash and cash equivalents at end of period	$ 3.1	$ 6.6	$ 28.5

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Millions	Total	Accumulated Other Comp Income (Loss)	Non-controlling Interest	Limited PartnerCommon Units	Limited PartnerClass B Units	General Partner
Beginning Balance at Dec. 31, 2012	$ 3,877.1	$ (67.3)		$ 3,190.3	$ 678.3	$ 75.8
Add (deduct):
Net income (loss)	250.2		$ (3.5)	194.5	20.2	39
Distributions paid	(533.9)			(468)	(20.6)	(45.3)
Sale of common units, net of related transaction costs	368.7			368.7
Capital contribution from general partner	7.8					7.8
Conversion of class B units to common units	0			677.9	(677.9)
Capital contributions from noncontrolling interests	90		90
Other comprehensive income (loss), net of tax	3.5	3.5
Ending Balance at Dec. 31, 2013	4,063.4	(63.8)	86.5	3,963.4	0	77.3
Add (deduct):
Net income (loss)	146.8		(86.8)	228.9		4.7
Distributions paid	(99.2)			(97.2)		(2)
Capital contributions from noncontrolling interests	8.2		8.2
Distributions paid to noncontrolling interests	(7.9)		(7.9)
Other comprehensive income (loss), net of tax	(9)	(9)
Ending Balance at Dec. 31, 2014	4,102.3	(72.8)	0	4,095.1	0	80
Add (deduct):
Net income (loss)	222			217.5		4.5
Distributions paid	(101.5)			(99.5)		(2)
Sale of common units, net of related transaction costs	113.1			113.1
Capital contribution from general partner	2.3					2.3
Other comprehensive income (loss), net of tax	(11.5)	(11.5)
Ending Balance at Dec. 31, 2015	$ 4,326.7	$ (84.3)	$ 0	$ 4,326.2	$ 0	$ 84.8

Corporate Structure

Corporate Structure	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Corporate Structure [Text Block]	Corporate Structure 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, Gulf South Pipeline Company, LP (Gulf South), Texas Gas Transmission, LLC (Texas Gas), Gulf Crossing Pipeline Company LLC (Gulf Crossing), Boardwalk Louisiana Midstream, LLC (Louisiana Midstream), Boardwalk Petrochemical Pipeline, LLC (Boardwalk Petrochemical) and Boardwalk Field Services, LLC (together, the operating subsidiaries), and consists of integrated natural gas, and natural gas liquids and other hydrocarbons (herein referred to together as NGLs) pipeline and storage systems and natural gas gathering and processing. Petal Gas Storage, LLC (Petal) was merged into Gulf South effective January 1, 2015. All of the Partnership’s operations are conducted by its operating subsidiaries. As of February 19, 2016 , 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). As of February 19, 2016 , 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 Class B limited partner interests converted to common units on a one-for-one basis on October 9, 2013. The Partnership’s common units are traded under the symbol “BWP” on the New York Stock Exchange (NYSE).

Accounting Policies

Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Basis of Presentation and Accounting Policies [Text Block]	Basis of Presentation and Accounting Policies Basis of Presentation The accompanying consolidated financial statements of the Partnership were prepared in accordance with accounting principles generally accepted in the United States of America (GAAP). In 2015, the Partnership began reporting certain operating costs associated with storage activities at its Louisiana Midstream subsidiary in Fuel and transportation expense, whereas those costs were previously reported in Operation and maintenance expense. The change was made to provide better information to users of the financial statements regarding costs that vary based on the utilization of the Partnership’s services. Amounts reported within Total operating costs and expenses in the consolidated Statements of Income for the 2014 and 2013 periods have been adjusted to conform to the current presentation. The effect of the adjustment increased Fuel and transportation expense and decreased Operation and maintenance expense by $4.0 million and $3.8 million for the years ended December 31, 2014 and 2013, with no impact on Total operating costs and expenses , Operating income, Net Income or cash flows from operations . As of December 31, 2015, the Partnership began applying the provisions of Accounting Standards Update 2015-03, Interest-Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs (ASU 2015-03), issued by the Financial Accounting Standards Board (FASB) in April 2015. ASU 2015-03 requires that debt issuance costs be presented on the balance sheet as a deduction from the recognized debt liability rather than as a deferred asset. In accordance with the transition requirements of ASU 2015-03, which require retrospective implementation, the Partnership adjusted the prior year amounts reported on the balance sheet to conform to the current presentation, resulting in a $12.5 million decrease in Other assets and a corresponding decrease in Long-term debt and capital lease obligation as of December 31, 2014. Principles of Consolidation The consolidated financial statements include the Partnership’s accounts and those of its wholly-owned subsidiaries after elimination of intercompany transactions. The Partnership also consolidates variable interest entities (VIEs) in which the Partnership is the primary beneficiary. Third party or affiliate ownership interests in the Partnership's subsidiaries and consolidated VIEs are presented as noncontrolling interests. The Partnership applies the equity method of accounting for investments in unconsolidated affiliates in which it owns 20 percent to 50 percent of the voting interests or otherwise exercises significant influence, but not control, over operating and financial policies of the investee. Under this method, the carrying amounts of the Partnership's equity investments are increased by a proportionate share of the investee's net income and contributions made and decreased by a proportionate share of the investee's net losses and distributions received. As of December 31, 2015 and 2014, the Partnership had no equity method investments recorded on its Consolidated Balance Sheets. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, expenses and disclosure of contingent assets and liabilities and the fair values of certain items. The Partnership bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, which form the basis for making judgments about the carrying amounts of assets and liabilities that are not readily apparent from other sources. Actual results could differ from such estimates. Segment Information The Partnership operates in one reportable segment - the operation of interstate natural gas and NGLs pipeline systems including integrated storage facilities. This segment consists of interstate natural gas pipeline systems which originate in the Gulf Coast region, Oklahoma and Arkansas and extend north and east through the Midwestern states of Tennessee, Kentucky, Illinois, Indiana and Ohio and NGLs pipelines and storage facilities in Louisiana and Texas. Regulatory Accounting Most of the Partnership's natural gas pipeline subsidiaries are regulated by the Federal Energy Regulatory Commission (FERC). When certain criteria are met, GAAP requires that certain rate-regulated entities account for and report assets and liabilities consistent with the economic effect of the manner in which independent third-party regulators establish rates (regulatory accounting). This basis of accounting is applicable to operations of the Partnership’s Texas Gas subsidiary which records certain costs and benefits as regulatory assets and liabilities in order to provide for recovery from or refund to customers in future periods, but is not applicable to operations associated with the Fayetteville and Greenville Laterals due to rates charged under negotiated rate agreements and a portion of the storage capacity due to the regulatory treatment associated with the rates charged for that capacity. Regulatory accounting is not applicable to the Partnership’s other FERC-regulated entities. The Partnership monitors the regulatory and competitive environment in which it operates to determine that its regulatory assets continue to be probable of recovery. If the Partnership were to determine that all or a portion of its regulatory assets no longer met the criteria for recognition as regulatory assets, that portion which was not recoverable would be written off, net of any regulatory liabilities. Note 9 contains more information regarding the Partnership’s regulatory assets and liabilities. Fair Value Measurements Fair value refers to an exit price that would be received to sell an asset or paid to transfer a liability in an orderly transaction in the principal market in which the reporting entity transacts based on the assumptions market participants would use when pricing the asset or liability assuming its highest and best use. A fair value hierarchy has been established that prioritizes the information used to develop those assumptions giving priority, from highest to lowest, to quoted prices in active markets for identical assets and liabilities (Level 1); observable inputs not included in Level 1, for example, quoted prices for similar assets and liabilities (Level 2); and unobservable data (Level 3), for example, a reporting entity’s own internal data based on the best information available in the circumstances. The Partnership uses fair value measurements to record derivatives, asset retirement obligations and impairments. Fair value measurements are also used to perform goodwill impairment testing and report fair values for certain items contained in this Report. The Partnership considers any transfers between levels within the fair value hierarchy to have occurred at the beginning of a quarterly reporting period. The Partnership did not recognize any transfers between Level 1 and Level 2 of the fair value hierarchy and did not change its valuation techniques or inputs during the year ended December 31, 2015 . Notes 5 and 11 contain more information regarding fair value measurements. Cash and Cash Equivalents Cash equivalents are highly liquid investments with an original maturity of three months or less and are stated at cost plus accrued interest, which approximates fair value. The Partnership had no restricted cash at December 31, 2015 and 2014 . Cash Management The operating subsidiaries participate in an intercompany cash management program with those that are FERC-regulated participating to the extent they are permitted under FERC regulations. Under the cash management program, depending on whether a participating subsidiary has short-term cash surpluses or cash requirements, Boardwalk Pipelines either provides cash to them or they provide cash to Boardwalk Pipelines. The transactions are represented by demand notes and are stated at historical carrying amounts. Interest income and expense are recognized on an accrual basis when collection is reasonably assured. The interest rate on intercompany demand notes is London Interbank Offered Rate (LIBOR) plus one percent and is adjusted every three months. Trade and Other Receivables Trade and other receivables are stated at their historical carrying amount, net of allowances for doubtful accounts. The Partnership establishes an allowance for doubtful accounts on a case-by-case basis when it believes the required payment of specific amounts owed is unlikely to occur. Uncollectible receivables are written off when a settlement is reached for an amount that is less than the outstanding historical balance or a receivable amount is deemed otherwise unrealizable. Gas Stored Underground and Gas Receivables and Payables Certain of the Partnership's operating subsidiaries have underground gas in storage which is utilized for system management and operational balancing, as well as for services including firm and interruptible storage associated with certain no-notice (NNS) and parking and lending (PAL) services. Gas stored underground includes the historical cost of natural gas volumes owned by the operating subsidiaries, at times reduced by certain operational encroachments upon that gas. Current gas stored underground represents net retained fuel remaining after providing transportation and storage services which is available for resale and is valued at the lower of weighted-average cost or market. The operating subsidiaries provide storage services whereby they store natural gas or NGLs on behalf of customers and also periodically hold customer gas under PAL services. Since the customers retain title to the gas held by the Partnership in providing these services, the Partnership does not record the related gas on its balance sheet. Certain of the Partnership's operating subsidiaries also periodically lend gas and NGLs to customers. In the course of providing transportation and storage services to customers, the operating subsidiaries may receive different quantities of gas from shippers and operators than the quantities delivered on behalf of those shippers and operators. This results in transportation and exchange gas receivables and payables, commonly known as imbalances, which are primarily settled in cash or the receipt or delivery of gas in the future. Settlement of imbalances requires agreement between the pipelines and shippers or operators as to allocations of volumes to specific transportation contracts and timing of delivery of gas based on operational conditions. The receivables and payables are valued at market price for operations where regulatory accounting is not applicable and are valued at the historical value of gas in storage for operations where regulatory accounting is applicable. Materials and Supplies Materials and supplies are carried at average cost and are included in Other Assets on the Consolidated Balance Sheets. The Partnership expects its materials and supplies to be used for capital projects related to its property, plant and equipment and for future growth projects. At December 31, 2015 and 2014 , the Partnership held approximately $22.2 million and $15.3 million of materials and supplies which were reflected in Other Assets on the Consolidated Balance Sheets. Property, Plant and Equipment (PPE) and Repair and Maintenance Costs PPE is recorded at its original cost of construction or fair value of assets purchased. Construction costs and expenditures for major renewals and improvements which extend the lives of the respective assets are capitalized. Construction work in progress is included in the financial statements as a component of PPE. All repair and maintenance costs are expensed as incurred. Depreciation of PPE related to operations for which regulatory accounting does not apply is provided for using the straight-line method of depreciation over the estimated useful lives of the assets, which range from 3 to 35 years. The ordinary sale or retirement of PPE for these assets could result in a gain or loss. Depreciation of PPE related to operations for which regulatory accounting is applicable is provided for primarily on the straight-line method at FERC-prescribed rates over estimated useful lives of 5 to 62 years. Reflecting the application of composite depreciation, gains and losses from the ordinary sale or retirement of PPE for these assets are not recognized in earnings and generally do not impact PPE, net. Note 6 contains more information regarding the Partnership’s PPE. Goodwill and Intangible Assets Goodwill represents the excess of the cost of an acquisition over the fair value of the net identifiable assets acquired and liabilities assumed. Goodwill is tested for impairment at the reporting unit level at least annually, as of November 30, or more frequently when events occur and circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount. Accounting requirements provide that a reporting entity may perform an optional qualitative assessment on an annual basis to determine whether events occurred or circumstances changed that would more likely than not reduce the fair value of a reporting unit below its carrying amount. If an initial qualitative assessment identifies that it is more likely than not that the fair value of a reporting unit is less than its carrying amount, or the optional qualitative assessment is not performed, a quantitative analysis is performed under a two-step impairment test to measure whether the fair value of the reporting unit is less than its carrying amount. If based upon a quantitative analysis the fair value of the reporting unit is less than its carrying amount, including goodwill, the Partnership performs an analysis of the fair value of all the assets and liabilities of the reporting unit. If the implied fair value of the reporting unit's goodwill is determined to be less than its carrying amount, an impairment loss is recognized for the difference. Intangible assets are those assets which provide future economic benefit but have no physical substance. The Partnership recorded intangible assets for customer relationships obtained through its acquisitions. The customer relationships, which are included in Other Assets on the Consolidated Balance Sheets, have a finite life and are being amortized in a systematic and rational manner over their estimated useful lives. Note 7 contains additional information regarding the Partnership's goodwill and intangible assets. Impairment of Long-lived Assets (including Tangible and Definite-lived Intangible Assets) The Partnership evaluates its long-lived and intangible assets for impairment when, in management’s judgment, events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. When such a determination has been made, management’s estimate of undiscounted future cash flows attributable to the remaining economic useful life of the asset is compared to the carrying amount of the asset to determine whether an impairment has occurred. If an impairment of the carrying amount has occurred, the amount of impairment recognized in the financial statements is determined by estimating the fair value of the assets and recording a loss to the extent that the carrying amount exceeds the estimated fair value. Capitalized Interest and Allowance for Funds Used During Construction (AFUDC) The Partnership records capitalized interest, which represents the cost of borrowed funds used to finance construction activities for operations where regulatory accounting is not applicable. The Partnership records AFUDC, which represents the cost of funds, including equity funds, applicable to regulated natural gas transmission plant under construction as permitted by FERC regulatory practices, in connection with the Partnership’s operations where regulatory accounting is applicable. Capitalized interest and the allowance for borrowed funds used during construction are recognized as a reduction to Interest expense and the allowance for equity funds used during construction is included in Miscellaneous other income, net within the Consolidated Statements of Income. The following table summarizes capitalized interest and the allowance for borrowed funds and allowance for equity funds used during construction (in millions): For the Year Ended 2015 2014 2013 Capitalized interest and allowance for borrowed funds used during construction $ 3.4 $ 6.8 $ 6.4 Allowance for equity funds used during construction 2.7 0.5 0.2 Income Taxes The Partnership is not a taxable entity for federal income tax purposes. As such, it does not directly pay federal income tax. The Partnership’s taxable income or loss, which may vary substantially from the net income or loss reported in the Consolidated Statements of Income, is includable in the federal income tax returns of each partner. The aggregate difference in the basis of the Partnership’s net assets for financial and income tax purposes cannot be readily determined as the Partnership does not have access to the information about each partner’s tax attributes related to the Partnership. The subsidiaries of the Partnership directly incur some income-based state taxes which are presented in Income taxes on the Consolidated Statements of Income. Note 13 contains more information regarding the Partnership’s income taxes. Revenue Recognition The maximum rates that may be charged by the majority of the Partnership's operating subsidiaries for their services are established through FERC’s cost-based rate-making process; however, rates charged by those operating subsidiaries may be less than those allowed by FERC. Revenues from transportation and storage services are recognized in the period the service is provided based on contractual terms and the related volumes transported or stored. In connection with some PAL and interruptible storage service agreements, cash is received at inception of the service period resulting in the recording of deferred revenues which are recognized in revenues over the period the services are provided. At December 31, 2015 and 2014 , the Partnership had deferred revenues of $10.0 million and $7.2 million , which are expected to be recognized through 2018. Retained fuel is recognized in revenues at market prices in the month of retention for operations where regulatory accounting is not applicable. The related fuel consumed in providing transportation services is recorded in Fuel and transportation expenses at market prices in the month consumed. In some cases, customers may elect to pay cash for the cost of fuel used in providing transportation services instead of having fuel retained in-kind. Retained fuel included in Transportation on the Consolidated Statements of Income for the years ended December 31, 2015 , 2014 and 2013 , was $53.2 million , $90.3 million and $76.9 million . The Partnership has contractual retainage provisions in some of its ethylene storage contracts that provide for the Partnership to retain ownership of 0.5% of customer inventory volumes injected into storage wells. The Partnership may sell the retainage volumes if commercially marketable volumes are on hand. The Partnership recognizes revenue for ethylene retainage volumes upon the physical sale of such volumes. Under FERC regulations, certain revenues that the operating subsidiaries collect may be subject to possible refunds to customers. Accordingly, during a rate case, estimated refund liabilities are recorded considering regulatory proceedings, advice of counsel and estimated risk-adjusted total exposure, as well as other factors. At December 31, 2015 , the Partnership had a $16.3 million refund liability related to the settled Gulf South rate case recorded on the Consolidated Balance Sheets. Refer to Note 4 for further information on the Gulf South rate case. There were no liabilities recorded as of December 31, 2014 , for any open rate case. Asset Retirement Obligations The accounting requirements for existing legal obligations associated with the future retirement of long-lived assets require entities to record the fair value of a liability for an asset retirement obligation in the period during which the liability is incurred. The liability is initially recognized at fair value and is increased with the passage of time as accretion expense is recorded, until the liability is ultimately settled. The accretion expense is included within Operation and maintenance costs within the Consolidated Statements of Income. An amount corresponding to the amount of the initial liability is capitalized as part of the carrying amount of the related long-lived asset and depreciated over the useful life of that asset. Note 8 contains more information regarding the Partnership’s asset retirement obligations. Environmental Liabilities The Partnership records environmental liabilities based on management’s estimates of the undiscounted future obligation for probable costs associated with environmental assessment and remediation of operating sites. These estimates are based on evaluations and discussions with counsel and operating personnel and the current facts and circumstances related to these environmental matters. Note 4 contains more information regarding the Partnership’s environmental liabilities. Defined Benefit Plans The Partnership maintains certain postretirement benefit plans for certain employees. The Partnership funds these plans through periodic contributions which are invested until the benefits are paid out to the participants. The net benefit cost of the plan is recorded in the Consolidated Statements of Income. The Partnership records an asset or liability based on the overfunded or underfunded status of the plan. Any deferred amounts related to unrecognized gains and losses or changes in actuarial assumptions are recorded as either a regulatory asset or liability or recorded as a component of accumulated other comprehensive income (AOCI) until those gains or losses are recognized in the Consolidated Statements of Income. Note 11 contains more information regarding the Partnership’s pension and postretirement benefit obligations. Unit-Based and Other Long-Term Compensation The Partnership provides awards of phantom common units (Phantom Common Units) to certain employees under its Long-Term Incentive Plan (LTIP). The Partnership also provides to certain employees awards of unit appreciation rights (UARs) and long-term cash bonuses (Long-Term Cash Bonuses) under the Boardwalk Pipeline Partners Unit Appreciation Rights and Cash Bonus Plan. In 2014, the Partnership entered into retention payment agreements with certain key employees. The Partnership measures the cost of an award issued in exchange for employee services based on the grant-date fair value of the award, or the stated amount in the case of the Long-Term Cash Bonuses and amounts under retention payment agreements. All outstanding awards are required to be settled in cash and are classified as a liability until settlement. The unit-based compensation awards are remeasured each reporting period until the final amount of awards is determined. The related compensation expense, less applicable estimates of forfeitures, is recognized over the period that employees are required to provide services in exchange for the awards, usually the vesting period. Note 11 contains additional information regarding the Partnership’s unit-based and other long-term compensation. Partner Capital Accounts For purposes of maintaining capital accounts, items of income and loss of the Partnership are allocated among the partners each year, or portion thereof, in accordance with the partnership agreement. Generally, net income for each period is allocated among the partners based on their respective ownership interests after deducting any priority allocations in the form of cash distributions paid to the general partner as the holder of IDRs. Derivative Financial Instruments The Partnership occasionally uses futures, swaps and option contracts (collectively, derivatives) to hedge exposure to various risks, including natural gas commodity and interest rate risk. The effective portion of the related unrealized gains and losses resulting from changes in fair values of the derivatives contracts designated as cash flow hedges are deferred as a component of AOCI. The deferred gains and losses are recognized in earnings when the hedged anticipated transactions affect earnings. Changes in fair value of derivatives that are not designated as cash flow hedges are recognized in earnings in the periods that those changes in fair value occur. Note 5 contains more information regarding the Partnership’s derivative financial instruments. Recently Issued Accounting Pronouncements In May 2014, the Financial Accounting Standards Board issued Accounting Standards Update 2014-09 (ASU 2014-09), Revenue from Contracts with Customers (Topic 606), 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. T he Partnership has initiated a project to evaluate the impact, if any, that ASU 2014-09 will have on its financial statements. However, no conclusions have been reached, including with regard to the application methodology.

Investments and Acquisitions

Investments and Acquisitions	12 Months Ended
	Dec. 31, 2015
Investments [Abstract]
Investments and Acquisitions [Text Block]	Investments and Acquisitions Bluegrass Project In 2013, the Partnership and the Williams Companies, Inc. (Williams) formed joint ventures for the development of the Bluegrass Project, a project between the Partnership, BPHC and Williams (Bluegrass Project). In 2014, due to cost escalations, construction delays and lack of customer commitments, among other things, the assets related to the joint ventures were determined to be impaired and were measured at fair value on a non-recurring basis. As a result, in the first quarter 2014, the Bluegrass Project entities, which were dissolved in December 2014, expensed the previously capitalized project costs, resulting in a $92.9 million charge, which was reflected in Equity losses in unconsolidated affiliates and Asset impairment on the income statement. Net of noncontrolling interests of $82.9 million , these expenses reduced the Partnership’s Net income attributable to controlling interests by $10.0 million . Acquisition of Boardwalk Petrochemical On October 8, 2014 , the Partnership completed the acquisition of Boardwalk Petrochemical, formerly known as Chevron Petrochemical Pipeline, LLC, which owns and operates the Evangeline ethylene pipeline system, from Chevron Pipe Line Company for $294.7 million in cash, subject to customary adjustments. This acquisition was made as part of the Partnership's long-term growth and diversification strategy and to complement the Partnership's existing NGLs and ethylene midstream assets. The purchase price was funded through borrowings under the Partnership's revolving credit facility.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies [Text Block]	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. Southeast Louisiana Flood Protection Litigation The Partnership and its subsidiary, 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 United States (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 has appealed the dismissal of the case to the U.S. Court of Appeals for the Fifth Circuit. In February 2015, Gulf South, along with other energy companies, was named a defendant in a petition for damages and injunctive relief filed by Joseph Bernstein (Case No. 744-226) and the Defelice Land Company, L.L.C. (Case No. 61-926). These cases are similar in nature to the Flood Protection Authority case discussed above. Both cases were originally filed in the Louisiana state court and were moved to federal court. In the second quarter 2015, the cases were remanded to Louisiana state court. Regulatory Matters In October 2014, Gulf South filed a rate case with FERC pursuant to Section 4 of the Natural Gas Act (Docket No. RP15-65), requesting, among other things, a reconfiguration of the transportation rate zones on its system and, in general, an increase in its tariff rates for those customers whose agreements are at maximum tariff rates. On May 1, 2015, Gulf South moved the filed tariff rates into effect, subject to refund. In September 2015, an uncontested settlement was reached with Gulf South’s customers and filed with FERC. The settlement provides for, among other things, (a) a system-wide rate design across the majority of the pipeline system; (b) a fuel tracker for determining future fuel rates; (c) a moratorium which prevents Gulf South or its customers from modifying the settlement rates until May 1, 2023, with certain exceptions; and (d) an extension of all NNS contracts to the end of the moratorium period at maximum rates, subject to each customer’s right to reduce capacity under those agreements from current levels by up to 6% on April 1, 2016, and by up to another 6% of their remaining contract capacity by April 1, 2020. The settled rates were moved into effect on an interim basis on November 1, 2015, and FERC approved the settlement in December 2015. The settlement will become final and effective on March 1, 2016. The Partnership has a $16.3 million refund liability recorded on its Consolidated Balance Sheet, which must be paid to customers by May 1, 2016. For the year ended December 31, 2015 , the Partnership recognized $20.4 million of additional operating revenues as a result of the rate case. Insurance Proceeds For the years ended December 31, 2015 and 2014, the Partnership received $8.8 million and $1.2 million in insurance proceeds from a business interruption claim related to Louisiana Midstream, which was recorded in Transportation revenues. No additional amounts are expected to be received. 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 December 31, 2015 and 2014 , the Partnership had an accrued liability of approximately $5.6 million and $6.1 million related to assessment and/or remediation costs associated with the historical use of polychlorinated biphenyls, petroleum hydrocarbons and mercury, groundwater protection measures and other costs. 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 seven years. As of December 31, 2015 and 2014 , approximately $1.7 million and $1.5 million were recorded in Other current liabilities and approximately $3.9 million and $4.6 million were recorded in Other Liabilities and Deferred Credits . Clean Air Act The Partnership’s pipelines are subject to the Clean Air Act, as amended, (CAA) and the CAA Amendments of 1990, as amended, (Amendments) which added significant provisions to the CAA. The Amendments require the Environmental Protection Agency (EPA) to promulgate new regulations pertaining to mobile sources, air toxics, areas of ozone non-attainment, greenhouse gases (GHG) and regulations affecting reciprocating engines subject to Maximum Achievable Control Technology. The operating subsidiaries presently operate two facilities in areas affected by non-attainment requirements for the current ozone standard (8-hour ozone standard). If the EPA designates additional new non-attainment areas or promulgates new air regulations where the Partnership operates, the cost of additions to PPE is expected to increase. The Partnership has assessed the impact of the CAA on its facilities and does not believe compliance with these regulations will have a material impact on its financial condition, results of operations or cash flows. On October 1, 2015, the EPA promulgated new air regulations lowering the 8-hour ozone standard relevant to non-attainment areas. The EPA lowered the ozone standard to 70 parts per billion for both the 8-hour primary and secondary standards that are protective of public health and public welfare. The EPA anticipates designating new non-attainment areas by October 1, 2017, and requiring states to revise implementation plans by October 1, 2020, with compliance dates anticipated between 2021 and 2037 determined by the degree of non-attainment. States could be required to implement new more stringent regulations, which could apply to the Partnership's and its exploration and production customers’ operations. In particular, compliance with these or other new regulations could, among other things, require installation of new emission controls on some of the Partnership's equipment, result in longer permitting timelines and significantly increase its capital expenditures and operating costs, which could adversely impact its business. Since non-attainment area designations will likely be based on 2014-2016 air quality monitoring data and because states will likely pursue various means to achieve the necessary reductions, additional facility impacts cannot be determined at this time. The Partnership will continue to monitor the rulemaking process relative to potentially impacted facilities. The Partnership is required to file annual reports with the EPA regarding GHG emissions from its compressor stations, pursuant to final rules issued by the EPA regarding the reporting of GHG emissions from sources in the U.S. that annually emit 25,000 or more metric tons of GHG, including carbon dioxide, methane and others. Additionally, the Partnership is required to conduct periodic and various facility surveys across its entire system to comply with the EPA's GHG emission calculations and reporting regulations. On October 22, 2015, the EPA finalized the new GHG reporting rule that expands the petroleum and natural gas system sources for which annual GHG emissions reporting is currently required to include GHG emissions reporting beginning in the 2016 reporting year for certain onshore gathering and boosting systems consisting primarily of gathering pipelines, compressors and process equipment used to perform natural gas compression, dehydration and acid gas removal. In addition, on August 18, 2015, the EPA issued a proposed rulemaking that will set methane emission standards for new and modified oil and gas production and natural gas processing and transmission facilities as part of an effort to reduce methane emissions from the oil and gas sector by up to 45 percent from 2012 levels by 2025. Some states have also adopted laws regulating GHG emissions, although none of the states in which the Partnership operates have adopted such laws. The federal rules and determinations regarding GHG emissions have not had, and are not expected to have, a material effect on the Partnership's financial condition, results of operations or cash flows. Lease Commitments The Partnership has various operating lease commitments extending through the year 2028 generally covering office space and equipment rentals. Total lease expense for the years ended December 31, 2015 , 2014 and 2013 , was approximately $12.2 million , $10.7 million and $8.6 million . The following table summarizes minimum future commitments related to these items at December 31, 2015 (in millions): 2016 $ 4.6 2017 4.2 2018 3.7 2019 3.2 2020 3.1 Thereafter 11.5 Total $ 30.3 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 December 31, 2015 , were approximately $185.9 million , all of which are expected to be settled within the next twelve months. Pipeline Capacity Agreements The Partnership’s operating subsidiaries have entered into pipeline capacity agreements with third-party pipelines that allow the operating subsidiaries to transport gas to off-system markets on behalf of customers. The Partnership incurred expenses of $6.9 million , $10.1 million and $9.8 million related to pipeline capacity agreements for the years ended December 31, 2015 , 2014 and 2013 . The future commitments related to pipeline capacity agreements as of December 31, 2015 , were (in millions): 2016 $ 6.4 2017 6.2 2018 2.0 2019 — 2020 — Thereafter — Total $ 14.6 Capital Lease The Partnership entered into an agreement to lease an office building in Owensboro, Kentucky. The construction of the building was completed and the Partnership took possession of the building in the third quarter 2013, at which time the Partnership recorded a capital lease asset and obligation of $10.5 million . The office building lease has a term of fifteen years with two twenty-year renewal options. Future commitments under this capital lease are as follows (in millions): 2016 $ 1.0 2017 1.0 2018 1.0 2019 1.1 2020 1.1 Thereafter 8.5 Total minimum lease payments 13.7 Less amounts representing interest (4.1 ) Present value of obligation under capital lease 9.6 Less: current portion of obligations under capital lease (recorded in Other current liabilities ) (0.5 ) Long-term obligations under capital lease $ 9.1 Amortization of the office building under the capital lease for the years ended December 31, 2015 and 2014 , was $0.7 million for each year and was included in Depreciation and amortization . As of December 31, 2015 and 2014 , assets recorded in Natural gas transmission and other plant under the capital lease were $10.5 million for each year and the accumulated amortization was $1.7 million and $1.0 million .

Other Comprehensive Income (OCI

Other Comprehensive Income (OCI) and Fair Value Measurements	12 Months Ended
	Dec. 31, 2015
Disclosure Text Block [Abstract]
Other Comprehensive Income [Text Block]	Other Comprehensive Income (OCI) and Fair Value Measurements Other Comprehensive Income (OCI) The Partnership estimates that approximately $3.9 million of net losses reported in AOCI as of December 31, 2015 , are expected to be reclassified into earnings within the next twelve months. This amount is comprised of a $1.5 million decrease to earnings related to net periodic benefit cost and a $2.4 million decrease to earnings related to cash flow hedges. The amount related to cash flow hedges are from treasury rate locks used in hedging interest payments associated with debt offerings that were settled in previous periods and are being amortized to earnings over the terms of the related interest payments, generally the terms of the related debt. The following table shows the components and reclassifications to net income of Accumulated other comprehensive loss which is included in Partners' Capital on the Consolidated Balance Sheets for the years ended December 31, 2013 through 2015 (in millions): Cash Flow Hedges Pension and Other Postretirement Costs Total Beginning balance, January 1, 2013 $ (15.5 ) $ (51.8 ) $ (67.3 ) Gain recorded in accumulated other comprehensive loss 1.6 — 1.6 Reclassifications: Transportation operating revenues 0.1 — 0.1 Other operating revenues (0.1 ) — (0.1 ) Disposal of operating assets (1.2 ) — (1.2 ) Interest expense (1) 2.4 — 2.4 Pension and other postretirement benefit costs — 0.7 0.7 Ending balance, December 31, 2013 $ (12.7 ) $ (51.1 ) $ (63.8 ) Loss recorded in accumulated other comprehensive loss (0.7 ) — (0.7 ) Reclassifications: Other operating revenues 0.2 — 0.2 Interest expense (1) 2.4 — 2.4 Pension and other postretirement benefit costs — (10.9 ) (10.9 ) Ending balance, December 31, 2014 $ (10.8 ) $ (62.0 ) $ (72.8 ) Reclassifications: Interest expense (1) 2.4 — 2.4 Pension and other postretirement benefit costs — (13.9 ) (13.9 ) Ending balance, December 31, 2015 $ (8.4 ) $ (75.9 ) $ (84.3 ) (1) Related to amounts deferred in AOCI from the treasury rate locks described above.
Fair Value Measurements [Text Block]	Financial Assets and Liabilities As of December 31, 2015 and 2014 , the Partnership had no assets and liabilities which were recorded at fair value on a recurring basis. The following methods and assumptions were used in estimating the fair value amounts included in the disclosures for financial assets and liabilities: Cash and Cash Equivalents: For cash and short-term financial assets, the carrying amount is a reasonable estimate of fair value due to the short maturity of those instruments. Long-Term Debt: The estimated fair value of the Partnership's publicly traded debt is based on quoted market prices at December 31, 2015 and 2014 . The fair market value of the debt that is not publicly traded is based on market prices of similar debt at December 31, 2015 and 2014 . The carrying amount of the Partnership's variable-rate debt approximates fair value because the instruments bear a floating market-based interest rate. The carrying amount and estimated fair values of the Partnership's financial assets and liabilities which were not recorded at fair value on the Consolidated Balance Sheets as of December 31, 2015 and 2014 , were as follows (in millions): As of December 31, 2015 Estimated Fair Value Financial Assets Carrying Amount Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 3.1 $ 3.1 $ — $ — $ 3.1 Financial Liabilities Long-term debt $ 3,460.6 (1) $ — $ 3,299.7 $ — $ 3,299.7 (1) The carrying amount of long-term debt excludes a $9.1 million long-term capital lease obligation and $10.4 million of unamortized debt issuance costs. As of December 31, 2014 Estimated Fair Value Financial Assets Carrying Amount Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 6.6 $ 6.6 $ — $ — $ 6.6 Financial Liabilities Long-term debt $ 3,680.1 (1) $ — $ 3,787.4 $ — $ 3,787.4 (1) The carrying amount of long-term debt excludes a $9.6 million long-term capital lease obligation and $12.5 million of unamortized debt issuance costs.

Property, Plant and Equipment (

Property, Plant and Equipment (PPE)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment (PPE) [Text Block]	Property, Plant and Equipment (PPE) The following table presents the Partnership’s PPE as of December 31, 2015 and 2014 (in millions): Category 2015 Weighted-Average Useful Lives (Years) 2014 Weighted-Average Useful Lives (Years) Depreciable plant: Transmission $ 7,930.3 37 $ 7,719.8 37 Storage 769.5 38 758.5 38 Gathering 347.6 27 336.7 27 General 182.8 13 170.0 14 Rights of way and other 122.5 37 114.9 36 Total utility depreciable plant 9,352.7 37 9,099.9 37 Non-depreciable: Construction work in progress 201.9 105.5 Storage 105.5 105.5 Land 30.2 28.4 Other 16.3 16.3 Total non-depreciable assets 353.9 255.7 Total PPE 9,706.6 9,355.6 Less: accumulated depreciation 2,052.2 1,766.4 Total PPE, net $ 7,654.4 $ 7,589.2 The non-depreciable assets were not included in the calculation of the weighted-average useful lives. The Partnership holds undivided interests in certain assets, including the Bistineau storage facility of which the Partnership owns 92% , the Mobile Bay Pipeline of which the Partnership owns 64% and offshore and other assets, comprised of pipeline and gathering assets in which the Partnership holds various ownership interests. In addition, the Partnership owns 83% of two ethylene wells and supporting surface facilities in Choctaw, Louisiana, and certain ethylene and propylene pipelines connecting Louisiana Midstream’s storage facilities in Choctaw to chemical manufacturing plants in Geismar, Louisiana. The proportionate share of investment associated with these interests has been recorded as PPE on the balance sheets. The Partnership records its portion of direct operating expenses associated with the assets in Operation and maintenance expense . The following table presents the gross PPE investment and related accumulated depreciation for the Partnership’s undivided interests as of December 31, 2015 and 2014 (in millions): 2015 2014 Gross PPE Investment Accumulated Depreciation Gross PPE Investment Accumulated Depreciation Bistineau storage $ 68.9 $ 19.5 $ 64.3 $ 17.5 Mobile Bay Pipeline 13.2 5.1 13.0 3.6 NGL pipelines and facilities 34.8 3.2 34.8 2.2 Offshore and other assets 17.1 12.8 18.8 13.7 Total $ 134.0 $ 40.6 $ 130.9 $ 37.0 Asset Impairment Charges The Partnership recognized $0.4 million , $10.1 million and $4.1 million of asset impairment charges for the years ended December 31, 2015 , 2014 and 2013 . The asset impairment charges recorded in 2015 and 2013 were primarily due to an increase in the estimate of asset retirement obligations related to retired assets. The asset impairment charges recorded in 2014 primarily related to the Bluegrass Project. Gas Sales In 2013, the Partnership recognized a gain of $29.9 million from the sale of approximately 14.9 billion cubic feet of natural gas stored underground with a carrying amount of $26.0 million . The gas was sold to provide capacity for additional parks of customer gas under PAL services as well as a result of a change in the storage gas needed to support operations and NNS. The gains related to these gas sales were recorded in Net gain on sale of operating assets .

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets [Text Block]	Goodwill and Intangible Assets Goodwill As of December 31, 2015 and 2014 , the Partnership had recorded in its Consolidated Balance Sheets $237.4 million of goodwill. The Partnership performed its annual goodwill impairment test for its reporting units as of November 30, 2015 . The results of the quantitative goodwill impairment test indicated that the fair value of the Partnership’s reporting units significantly exceeded their carrying amounts. No impairment charge related to goodwill was recorded for any of the Partnership’s reporting units during 2015 or 2014. In 2013, the Partnership recognized a goodwill impairment charge of $51.5 million related to the goodwill associated with the Petal acquisition. Intangible Assets The following table contains information regarding the Partnership's intangible assets, which includes customer relationships acquired as part of its acquisitions (in millions): December 31, 2015 2014 Gross carrying amount $ 59.4 $ 59.4 Accumulated amortization (5.5 ) (3.5 ) Net carrying amount $ 53.9 $ 55.9 For the years ended December 31, 2015 , 2014 and 2013 , amortization expense for intangible assets totaled $2.0 million , $1.4 million and $1.3 million and was recorded in Depreciation and amortization on the Consolidated Statements of Income. Amortization expense for the next five years and in total thereafter as of December 31, 2015 , is expected to be as follows (in millions): 2016 $ 2.0 2017 2.0 2018 2.0 2019 2.0 2020 1.9 Thereafter 44.0 $ 53.9 The weighted-average remaining useful life of the Partnership's intangible assets as of December 31, 2015 , was 28 years.

Asset Retirement Obligations (A

Asset Retirement Obligations (ARO)	12 Months Ended
	Dec. 31, 2015
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligations (ARO) [Text Block]	Asset Retirement Obligations (ARO) The Partnership has identified and recorded legal obligations associated with the abandonment of certain pipeline and storage assets, brine ponds, offshore facilities and the abatement of asbestos consisting of removal, transportation and disposal when removed from certain compressor stations and meter station buildings. Legal obligations exist for the main pipeline and certain other Partnership assets; however, the fair value of the obligations cannot be determined because the lives of the assets are indefinite and therefore cash flows associated with retirement of the assets cannot be estimated with the degree of accuracy necessary to establish a liability for the obligations. The following table summarizes the aggregate carrying amount of the Partnership’s ARO (in millions): 2015 2014 Balance at beginning of year $ 46.3 $ 47.1 Liabilities recorded 9.7 4.3 Liabilities settled (5.1 ) (6.9 ) Accretion expense 1.7 1.8 Balance at end of year 52.6 46.3 Less: Current portion of ARO (14.5 ) (6.4 ) Long-term ARO $ 38.1 $ 39.9 For the Partnership’s operations where regulatory accounting is applicable, depreciation rates for PPE are comprised of two components. One component is based on economic service life (capital recovery) and the other is based on estimated costs of removal (as a component of negative salvage) which is collected in rates and does not represent an existing legal obligation. The Partnership has reflected $57.2 million and $60.5 million as of December 31, 2015 and 2014 , in the accompanying Consolidated Balance Sheets as Provision for other asset retirement related to the estimated cost of removal collected in rates.

Regulatory Assets and Liabiliti

Regulatory Assets and Liabilities	12 Months Ended
	Dec. 31, 2015
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Assets and Liabilities [Text Block]	Regulatory Assets and Liabilities The amounts recorded as regulatory assets and liabilities in the Consolidated Balance Sheets as of December 31, 2015 and 2014 , are summarized in the table below. The table also includes amounts related to unamortized debt expense and unamortized discount on long-term debt. While these amounts are not regulatory assets and liabilities, they are a critical component of the embedded cost of debt financing utilized in the Texas Gas rate proceedings. The tax effect of the equity component of AFUDC represents amounts recoverable from rate payers for the tax recorded in regulatory accounting. Certain amounts in the table are reflected as a negative, or a reduction, to be consistent with the regulatory books of account. The period of recovery for the regulatory assets included in rates varies from one to eighteen years. The remaining period of recovery for regulatory assets not yet included in rates would be determined in future rate proceedings. None of the regulatory assets shown below were earning a return as of December 31, 2015 and 2014 (in millions): 2015 2014 Regulatory Assets: Pension $ 10.6 $ 10.6 Tax effect of AFUDC equity 3.1 3.5 Fuel tracker — 0.2 Total regulatory assets $ 13.7 $ 14.3 Regulatory Liabilities: Cashout and fuel tracker $ 6.0 $ 0.9 Provision for other asset retirement 57.2 60.5 Unamortized debt expense and premium on reacquired debt (1) (8.0 ) (9.6 ) Unamortized discount on long-term debt (1.2 ) (1.5 ) Postretirement benefits other than pension 39.9 34.2 Total regulatory liabilities $ 93.9 $ 84.5 (1) The 2014 balance of unamortized debt expense and premium on reacquired debt was moved to the Regulatory Liabilities section due to the implementation of ASU 2015-03. Refer to Note 2 for more information regarding the implementation of ASU 2015-03.

Financing

Financing	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Financing [Text Block]	Financing Long-Term Debt The following table presents all long-term debt issues outstanding as of December 31, 2015 and 2014 (in millions): 2015 2014 Notes and Debentures: Boardwalk Pipelines 5.875% Notes due 2016 $ 250.0 $ 250.0 5.50% Notes due 2017 300.0 300.0 5.20% Notes due 2018 185.0 185.0 5.75% Notes due 2019 350.0 350.0 3.375% Notes due 2023 300.0 300.0 4.95% Notes due 2024 (Boardwalk Pipelines 2024 Notes) 600.0 350.0 Gulf South 5.05% Notes due 2015 (Gulf South 2015 Notes) — 275.0 6.30% Notes due 2017 275.0 275.0 4.00% Notes due 2022 300.0 300.0 Texas Gas 4.60% Notes due 2015 (Texas Gas 2015 Notes) — 250.0 4.50% Notes due 2021 440.0 440.0 7.25% Debentures due 2027 100.0 100.0 Total notes and debentures 3,100.0 3,375.0 Term Loan — 200.0 Revolving Credit Facility: Gulf Crossing 375.0 120.0 Capital lease obligation 9.1 9.6 3,484.1 3,704.6 Less: Unamortized debt discount (14.4 ) (14.9 ) Unamortized debt issuance costs (10.4 ) (12.5 ) Total Long-Term Debt and Capital Lease Obligation $ 3,459.3 $ 3,677.2 Maturities of the Partnership’s long-term debt for the next five years and in total thereafter are as follows (in millions): 2016 $ 250.0 2017 575.0 2018 185.0 2019 350.0 2020 375.0 Thereafter 1,740.0 Total long-term debt $ 3,475.0 The Partnership has included $250.0 million of debt which matures in less than one year as long-term debt on its balance sheet as of December 31, 2015. The Partnership intends to refinance the Boardwalk Pipelines Note due November 15, 2016, on a long-term basis and has adequate available capacity under the revolving credit facility to extend the amount that would otherwise come due in less than a year. Notes and Debentures As of December 31, 2015 and 2014 , the weighted-average interest rate of the Partnership's notes and debentures was 5.32% and 5.31% . For the years ended December 31, 2015 , 2014 and 2013 , 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 March 2015 Boardwalk Pipelines $ 250.0 $ 2.9 $ 247.1 (1) 4.95 % December 15, 2024 June 15 and December 15 November 2014 Boardwalk Pipelines $ 350.0 $ 7.1 $ 342.9 (2) 4.95 % December 15, 2024 June 15 and December 15 (1) The net proceeds of this offering were used to retire a portion of the outstanding $250.0 million aggregate principal amount of the Texas Gas 2015 Notes. Initially, the Partnership used the net proceeds to reduce outstanding borrowings under its revolving credit facility. Subsequently, on June 1, 2015, the Partnership retired the Texas Gas 2015 Notes with borrowings under its revolving credit facility. (2) The net proceeds of this offering were used to retire all of the outstanding Gulf South 2015 Notes and the remainder of the net proceeds were used to reduce outstanding borrowings under the Partnership's revolving credit facility. The Partnership’s notes and debentures are redeemable, in whole or in part, at the Partnership’s option at any time, at a redemption price equal to the greater of 100% of the principal amount of the notes to be redeemed or a “make whole” redemption price based on the remaining scheduled payments of principal and interest discounted to the date of redemption at a rate equal to the Treasury rate plus 20 to 50 basis points depending upon the particular issue of notes, plus accrued and unpaid interest, if any. Other customary covenants apply, including those concerning events of default. The indentures governing the notes and debentures have restrictive covenants which provide that, with certain exceptions, neither the 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 December 31, 2015 , Boardwalk Pipelines and its operating subsidiaries were in compliance with their debt covenants. Revolving Credit Facility In May 2015, the Partnership entered into a Third Amended and Restated Revolving Credit Agreement (Amended Credit Agreement) with Wells Fargo Bank, N.A., as administrative agent, having aggregate lending commitments of $1.5 billion , a maturity date of May 26, 2020 , and including Boardwalk Pipelines, Texas Gas, Gulf South and Gulf Crossing as borrowers (Borrowers). Interest is determined, at the Partnership's election, by reference to (a) the base rate which is the highest of (1) the prime rate , (2) the federal funds rate plus 0.50% and (3) the one month Eurodollar Rate plus 1.00% , plus an applicable margin, or (b) the LIBOR plus an applicable margin. The applicable margin ranges from 0.00% to 0.75% for loans bearing interest based on the base rate and ranges from 1.00% to 1.75% for loans bearing interest based on the LIBOR rate, in each case determined based on the individual Borrower's credit rating from time to time. The Amended Credit Agreement also provides for a quarterly commitment fee charged on the average daily unused amount of the revolving credit facility ranging from 0.10% to 0.275% and determined based on the individual Borrower's credit rating from time to time. The credit facility contains various restrictive covenants and other usual and customary terms and conditions, including restrictions regarding the incurrence of additional debt, the sale of assets and sale-leaseback transactions. The financial covenants under the credit facility require the Partnership and its subsidiaries to maintain, among other things, a ratio of total consolidated debt to consolidated EBITDA (as defined in the Amended Credit Agreement) measured for the previous twelve months of not more than 5.0 to 1.0 , or up to 5.5 to 1.0 for the three quarters following an acquisition. The Partnership and its subsidiaries were in compliance with all covenant requirements under the credit facility as of December 31, 2015 . Outstanding borrowings under the Partnership's revolving credit facility as of December 31, 2015 and 2014 , were $375.0 million and $120.0 million with a weighted-average borrowing rate of 1.67% and 1.54% . As of February 17, 2016 , the Partnership had $470.0 million outstanding borrowings under its credit facility, resulting in an available borrowing capacity of over $1.0 billion . Term Loan The Partnership had a variable-rate term loan due October 1, 2017 (Term Loan). At December 31, 2014 , outstanding borrowings under the Term Loan were $200.0 million , with a weighted-average borrowing interest rate of 1.91% . The Partnership repaid all outstanding borrowings and terminated all related commitments in 2015. Subordinated Debt Agreement with Affiliate The Partnership entered into a Subordinated Loan Agreement with BPHC under which the Partnership could borrow up to $300.0 million (Subordinated Loan) through December 31, 2016. The Subordinated Loan bears interest at increasing rates, ranging from 5.75% to 9.75% , payable semi-annually in June and December, and matures in July 2024 . The Subordinated Loan must be prepaid with the net cash proceeds from the issuance of additional equity securities by the Partnership or the incurrence of certain indebtedness by the Partnership or its subsidiaries, although BPHC may waive such prepayment. The Subordinated Loan is subordinated in right of payment to the Partnership’s obligations under its revolving credit facility pursuant to the terms of a Subordination Agreement between BPHC and Wells Fargo, N.A., as representative of the lenders under the revolving credit facility. Through the filing date of this Report, the Partnership has not borrowed any amounts under the Subordinated Loan. Issuances of Common Units The Partnership had no common unit issuances for the year ended December 31, 2014 . For the years ended December 31, 2015 and 2013 , the Partnership completed the following issuances and sales of common units (in millions, except the issuance price): Month of Offering Number of Common Units Issuance Price Less Underwriting Discounts and Expenses Net Proceeds (including General Partner Contribution) Common Units Outstanding After Offering Common Units Held by the Public After Offering February 2015 - April 2015 7.0 $ 16.19 (1) $ 1.1 $ 115.4 250.3 (2) 124.6 May 2013 12.7 $ 30.12 $ 12.3 $ 376.5 220.3 117.6 (1) The issuance price represents the average issuance price for the common units issued under an equity distribution agreement described further below. (2) On October 9, 2013, all of the 22.9 million class B units were converted into common units on a one-for-one basis, pursuant to the terms of the partnership agreement. The proceeds of the May 2013 offering were used to reduce borrowings under the Partnership’s revolving credit facility. In addition to funds received from the issuance and sale of common units, the general partner concurrently contributed amounts to maintain its 2% interest in the Partnership. The Partnership has an effective registration statement on file with the Securities and Exchange Commission, which expires in May 2016, for the issuance of up to $500.0 million of the Partnership's common units. Under the registration statement, pursuant to an equity distribution agreement between the Partnership and certain broker-dealers the Partnership may sell its common units from time to time through the broker-dealers as the Partnership’s sales agents. Sales of common units can be made by means of ordinary brokers’ transactions on the NYSE or as otherwise agreed by the Partnership and one or more of the broker-dealers. For the year ended December 31, 2015 , the Partnership sold 7.0 million common units under its equity distribution agreement and received net proceeds of $115.4 million , including a $2.3 million contribution received from its general partner to maintain its 2% general partner interest. Summary of Changes in Outstanding Units The following table summarizes changes in the Partnership’s common and class B units since January 1, 2013 (in millions): Common Units Class B Units (1) Balance, January 1, 2013 207.7 22.9 Common units issued in connection with underwritten offerings 12.7 — Conversion of class B units 22.9 (22.9 ) Balance, December 31, 2013 and 2014 243.3 — Common units issued under an equity distribution agreement 7.0 — Balance, December 31, 2015 250.3 — (1) On October 9, 2013, all of the 22.9 million class B units were converted into common units on a one-for-one basis, pursuant to the terms of the partnership agreement. Registration Rights Agreement The Partnership entered into an Amended and Restated Registration Rights Agreement with BPHC under which the Partnership agreed to register the resale by BPHC of up to 27.9 million common units and to reimburse BPHC up to a maximum amount of $0.914 per common unit for underwriting discounts and commissions. As of December 31, 2015 and 2014 , the Partnership had an accrued liability of approximately $16.0 million for future underwriting discounts and commissions that would be reimbursed to BPHC and other registration and offering costs that are expected to be incurred by the Partnership.

Employee Benefits

Employee Benefits	12 Months Ended
	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Employee Benefits [Text Block]	Employee Benefits Retirement Plans Defined Benefit Retirement Plans Texas Gas employees hired prior to November 1, 2006, are covered under a non-contributory, defined benefit pension plan (Pension Plan). The Texas Gas Supplemental Retirement Plan (SRP) provides pension benefits for the portion of an eligible employee’s pension benefit under the Pension Plan that becomes subject to compensation limitations under the Internal Revenue Code. Collectively, the Partnership refers to the Pension Plan and the SRP as Retirement Plans. The Partnership uses a measurement date of December 31 for its Retirement Plans. As a result of the Texas Gas rate case settlement in 2006, the Partnership is required to fund the amount of annual net periodic pension cost associated with the Pension Plan, including a minimum of $3.0 million which is the amount included in rates. In each of 2015 and 2014 , the Partnership funded $3.0 million to the Pension Plan and expects to fund approximately $3.0 million to the plan in 2016 . The Partnership does not anticipate that any Pension Plan assets will be returned to the Partnership during 2015. In 2015 and 2014 , there were no payments made under the SRP. The Partnership does not expect to fund the SRP until such time as benefits are paid. The Partnership recognizes in expense each year the actuarially determined amount of net periodic pension cost associated with its Retirement Plans, including a minimum amount of $3.0 million related to its Pension Plan, in accordance with the 2006 rate case settlement. Texas Gas is permitted to seek future rate recovery for amounts of annual Pension Plan costs in excess of $6.0 million and is precluded from seeking future recovery of annual Pension Plan costs between $3.0 million and $6.0 million . As a result, the Partnership would recognize a regulatory asset for amounts of annual Pension Plan costs in excess of $6.0 million and would reduce its regulatory asset to the extent that annual Pension Plan costs are less than $3.0 million . Annual Pension Plan costs between $3.0 million and $6.0 million will be charged to expense. Postretirement Benefits Other Than Pension (PBOP) Texas Gas provides postretirement medical benefits and life insurance to retired employees who were employed full time, hired prior to January 1, 1996, and have met certain other requirements. In each of 2015 and 2014 , the Partnership contributed $0.1 million to the PBOP plan. The PBOP plan is currently in an overfunded status; therefore, the Partnership does not expect to make any contributions to the plan in 2016 . The Partnership does not anticipate that any plan assets will be returned to the Partnership during 2016 . The Partnership uses a measurement date of December 31 for its PBOP plan. Projected Benefit Obligation, Fair Value of Assets and Funded Status The projected benefit obligation, fair value of assets, funded status and the amounts not yet recognized as components of net periodic pension and postretirement benefits cost for the Retirement Plans and PBOP at December 31, 2015 and 2014 , were as follows (in millions): Retirement Plans PBOP For the Year Ended For the Year Ended 2015 2014 2015 2014 Change in benefit obligation: Benefit obligation at beginning of period $ 149.9 $ 148.5 $ 55.1 $ 50.0 Service cost 3.8 3.9 0.3 0.4 Interest cost 4.9 5.8 2.0 2.2 Plan participants’ contributions — — 1.1 0.9 Actuarial (gain) loss (1.9 ) 3.6 (5.6 ) 5.2 Benefits paid (0.5 ) (0.5 ) (4.5 ) (3.6 ) Settlement (12.4 ) (11.4 ) — — Benefit obligation at end of period $ 143.8 $ 149.9 $ 48.4 $ 55.1 Change in plan assets: Fair value of plan assets at beginning of period $ 130.7 $ 131.4 $ 87.3 $ 80.8 Actual return on plan assets (1.3 ) 8.2 2.4 9.1 Benefits paid (0.5 ) (0.5 ) (4.5 ) (3.6 ) Settlement (12.4 ) (11.4 ) — — Company contributions 3.0 3.0 0.1 0.1 Plan participants’ contributions — — 1.1 0.9 Fair value of plan assets at end of period $ 119.5 $ 130.7 $ 86.4 $ 87.3 Funded status $ (24.3 ) $ (19.2 ) $ 38.0 $ 32.2 Items not recognized as components of net periodic cost: Prior service cost (credit) $ — $ — $ (0.9 ) $ (8.6 ) Net actuarial loss 29.9 26.0 7.2 10.7 Total $ 29.9 $ 26.0 $ 6.3 $ 2.1 At December 31, 2015 and 2014 , the following aggregate information relates only to the underfunded plans (in millions): Retirement Plans For the Year Ended 2015 2014 Projected benefit obligation $ 143.8 $ 149.9 Accumulated benefit obligation 134.1 139.7 Fair value of plan assets 119.5 130.7 Components of Net Periodic Benefit Cost Components of net periodic benefit cost for both the Retirement Plans and PBOP for the years ended December 31, 2015 , 2014 and 2013 , were as follows (in millions): Retirement Plans PBOP For the Year Ended For the Year Ended 2015 2014 2013 2015 2014 2013 Service cost $ 3.8 $ 3.9 $ 3.9 $ 0.3 $ 0.4 $ 0.5 Interest cost 4.9 5.8 5.0 2.0 2.2 2.1 Expected return on plan assets (9.1 ) (9.5 ) (9.1 ) (4.6 ) (4.2 ) (4.5 ) Amortization of prior service credit — — — (7.7 ) (7.8 ) (7.8 ) Amortization of unrecognized net loss 2.0 1.4 2.1 — 0.3 — Settlement charge 2.5 1.9 1.7 — — — Net periodic benefit cost $ 4.1 $ 3.5 $ 3.6 $ (10.0 ) $ (9.1 ) $ (9.7 ) Due to the Texas Gas rate case settlement in 2006, Texas Gas is permitted to seek future rate recovery for amounts of annual Pension Plan costs in excess of $6.0 million . Estimated Future Benefit Payments The following table shows benefit payments, which reflect expected future service, as appropriate, which are expected to be paid for both the Retirement Plans and PBOP (in millions): Retirement Plans PBOP 2016 $ 18.9 $ 2.9 2017 13.4 3.0 2018 13.7 3.2 2019 14.8 3.2 2020 13.7 3.2 2021-2025 64.3 15.5 Weighted–Average Assumptions Weighted-average assumptions used to determine benefit obligations for the years ended December 31, 2015 and 2014 , were as follows: Retirement Plans PBOP For the Year Ended For the Year Ended 2015 2014 2015 2014 Pension SRP Pension SRP Discount rate 3.60 % 4.00 % 3.35 % 3.75 % 4.25 % 3.90 % Expected return on plan assets 7.50 % 7.50 % 7.50 % 7.50 % 5.30 % 5.30 % Rate of compensation increase 3.50 % 3.50 % 3.50 % 3.50 % — % — % Weighted-average assumptions used to determine net periodic benefit cost for the periods indicated were as follows: Retirement Plans PBOP For the Year Ended For the Year Ended 2015 2014 2013 2015 2014 2013 Pension SRP Pension SRP Pension SRP Discount rate 3.35%/ 3.60% (1) 3.75 % 4.00% 4.25 % 3.25%/ 4.10% (2) 3.50 % 3.90 % 4.50 % 3.90 % Expected return on plan assets 7.50 % 7.50 % 7.50% 7.50 % 7.50 % 7.50 % 5.30 % 5.30 % 5.30 % Rate of compensation increase 3.50 % 3.50 % 3.50% 3.50 % 3.50 % 3.50 % — % — % — % (1) Pension expense was remeasured at August 31, 2015, to reflect a settlement. (2) Pension expense was remeasured at September 30, 2013, to reflect a settlement. The long-term rate of return for plan assets was determined based on widely-accepted capital market principles, long-term return analysis for global fixed income and equity markets as well as the active total return oriented portfolio management style. Long-term trends are evaluated relative to market factors such as inflation, interest rates and fiscal and monetary policies, in order to assess the capital market assumptions as applied to the plan. Consideration of diversification needs and rebalancing is maintained. PBOP Assumed Health Care Cost Trends Assumed health care cost trend rates have a significant effect on the amounts reported for PBOP. A one-percentage-point change in assumed trend rates for health care costs would have had the following effects on amounts reported for the year ended December 31, 2015 (in millions): Effect of 1% Increase: 2015 Benefit obligation at end of year $ 2.0 Total of service and interest costs for year 0.1 Effect of 1% Decrease: Benefit obligation at end of year $ (1.8 ) Total of service and interest costs for year (0.1 ) For measurement purposes, for December 31, 2015 , health care cost trend rates for the plans were assumed to remain at 7.5% for 2016-2017, grading down to 5.0% by 2021 , assuming 0.5% annual increments for all participants. For December 31, 2014 , health care cost trend rates for the plans were assumed to remain at 8.0% for 2015-2016, grading down to 5.0% by 2022 , assuming 0.5% annual increments for all participants. Pension Plan and PBOP Asset Allocation and Investment Strategy Pension Plan The Pension Plan investments are held in a trust account and consist of an undivided interest in an investment account of the Loews Corporation Employees Retirement Trust (Master Trust), established by Loews and its participating subsidiaries. Use of the Master Trust permits the commingling of trust assets of the Pension Plan with the assets of the Loews Corporation Cash Balance Retirement Plan for investment and administrative purposes. Although assets of all plans are commingled in the Master Trust, the custodian maintains supporting records for the purpose of allocating the net gain or loss of the investment account to the participating plans. The net investment income of the investment assets is allocated by the custodian to each participating plan based on the relationship of the interest of each plan to the total of the interests of the participating plans. The Master Trust assets are measured at fair value. The fair value of the interest in the assets of the Master Trust associated with the Pension Plan as of December 31, 2015 and 2014 , was $119.5 million (or 51.0% ) and $130.7 million (or 51.0% ), of the total Master Trust assets. Equity securities are publicly traded securities which are valued using quoted market prices and are considered a Level 1 investment under the fair value hierarchy. Short-term investments that are actively traded or have quoted prices, such as money market funds, are considered Level 1 investments. Fixed income mutual funds are actively traded and valued using quoted market prices and are considered a Level 1 investment. Corporate and other taxable bonds and asset-backed securities are valued using pricing for similar securities, recently executed transactions, cash flow models with yield curves, broker/dealer quotes and other pricing models utilizing observable inputs and are considered Level 2 investments. The limited partnership and other invested assets consist primarily of hedge funds, whose fair value represents the Master Trust’s share of the net asset value of each company, as determined by the general partner. Level 2 limited partnership and other invested assets include investments which can be redeemed at net asset value in 90 days or less. The limited partnership investments that contain withdrawal provisions greater than 90 days or at the termination of the partnership are considered Level 3 investments. The following table sets forth, by level within the fair value hierarchy, a summary of the Master Trust’s investments measured at fair value on a recurring basis at December 31, 2015 (in millions): Master Trust Assets Level 1 Level 2 Level 3 Total Equity securities $ 36.1 $ — $ — $ 36.1 Short-term investments 6.6 — — 6.6 Fixed income mutual funds 94.8 — — 94.8 Asset-backed securities — 6.4 — 6.4 Limited partnerships : Hedge funds — 49.7 31.0 80.7 Private equity — — 9.7 9.7 Total investments $ 137.5 $ 56.1 $ 40.7 $ 234.3 The following table sets forth, by level within the fair value hierarchy, a summary of the Master Trust’s investments measured at fair value on a recurring basis at December 31, 2014 (in millions): Master Trust Assets Level 1 Level 2 Level 3 Total Equity securities $ 42.3 $ — $ — $ 42.3 Short-term investments 11.8 — — 11.8 Other assets 1.1 — — 1.1 Fixed income mutual funds 98.7 — — 98.7 Asset-backed securities — 6.0 — 6.0 Limited partnerships: Hedge funds — 56.7 29.5 86.2 Private equity — — 10.1 10.1 Total investments $ 153.9 $ 62.7 $ 39.6 $ 256.2 The following table presents a reconciliation of the beginning and ending balances of the fair value measurements using significant unobservable inputs (Level 3) for the Master Trust (in millions): Limited Partnerships: Hedge Funds Limited Partnerships: Private Equity Balance January 1, 2014 $ 29.7 $ 11.7 Actual return on assets still held 2.1 0.2 Actual return on assets sold 0.1 0.8 Purchases, sales and settlements (2.4 ) (2.6 ) Balance December 31, 2014 29.5 10.1 Actual return on assets still held 1.0 0.6 Actual return on assets sold 0.2 0.1 Purchases, sales and settlements (0.3 ) (1.1 ) Net transfers into Level 3 0.6 — Balance December 31, 2015 $ 31.0 $ 9.7 PBOP The PBOP plan assets are held in a trust and are measured at fair value. Short-term investments that are actively traded or have quoted prices, such as money market or mutual funds, are considered Level 1 investments. Fixed income mutual funds are actively traded and valued using quoted market prices and are considered Level 1 investments. Tax exempt securities, consisting of municipal securities, corporate and other taxable bonds and asset-backed securities are valued using pricing for similar securities, recently executed transactions, cash flow models with yield curves, broker/dealer quotes and other pricing models utilizing observable inputs and are considered Level 2 investments. The following table sets forth, by level within the fair value hierarchy, a summary of the PBOP trust investments measured at fair value on a recurring basis at December 31, 2015 (in millions): PBOP Trust Assets Level 1 Level 2 Level 3 Total Short-term investments $ 3.0 $ — $ — $ 3.0 Fixed income mutual funds 4.7 — — 4.7 Asset-backed securities — 18.8 — 18.8 Corporate bonds — 17.0 — 17.0 Tax exempt securities — 42.9 — 42.9 Total investments $ 7.7 $ 78.7 $ — $ 86.4 The following table sets forth, by level within the fair value hierarchy, a summary of the PBOP trust investments measured at fair value on a recurring basis at December 31, 2014 (in millions): PBOP Trust Assets Level 1 Level 2 Level 3 Total Short-term investments $ 3.2 $ — $ — $ 3.2 Fixed income mutual funds 3.0 — — 3.0 Asset-backed securities — 20.4 — 20.4 Corporate bonds — 17.8 — 17.8 Tax exempt securities — 42.9 — 42.9 Total investments $ 6.2 $ 81.1 $ — $ 87.3 Investment strategy Pension Plan: The Partnership employs a total-return approach using a mix of equities and fixed income investments to maximize the long-term return on plan assets for a prudent level of risk and generate cash flows adequate to meet plan requirements. The intent of this strategy is to minimize plan expenses by outperforming plan liabilities over the long run. Risk tolerance is established through careful consideration of the plan liabilities, plan funded status and corporate financial conditions. The investment strategy has been to allocate between 40% and 60% of the investment portfolio to equity and alternative investments, including limited partnerships, with consideration given to market conditions and target asset returns. The investment portfolio contains a diversified blend of fixed income, equity and short-term securities. Alternative investments, including limited partnerships, have been used to enhance risk adjusted long-term returns while improving portfolio diversification. At December 31, 2015 , the pension trust had committed $7.3 million to future capital calls from various third party limited partnership investments in exchange for an ownership interest in the related partnerships. Investment risk is measured and monitored on an ongoing basis through annual liability measurements, periodic asset and liability studies and quarterly investment portfolio reviews. PBOP: The investment strategy for the PBOP assets is to reduce the volatility of plan investments while protecting the initial investment given the overfunded status of the plan. At December 31, 2015 and 2014 , all of the PBOP investments were in fixed income securities. Defined Contribution Plans Texas Gas employees hired on or after November 1, 2006, and 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 their employees. Costs related to the Partnership’s defined contribution plans were $9.8 million , $9.0 million and $8.6 million for the years ended December 31, 2015 , 2014 and 2013 . Long-Term Incentive Compensation Plans The Partnership grants to selected employees long-term compensation awards under the LTIP and the UAR and Cash Bonus Plan. These awards are intended to align the interests of the employees with those of the Partnership’s unitholders, encourage superior performance, attract and retain employees who are essential for the Partnership’s growth and profitability and to encourage employees to devote their best efforts to advancing the Partnership’s business over both long and short-term time horizons. The Partnership also makes annual grants of common units to certain of its directors under the LTIP. LTIP The Partnership reserved 3,525,000 common units for grants of units, restricted units, unit options and UARs to officers and directors of the Partnership’s general partner and for selected employees under the LTIP. The Partnership has outstanding Phantom Common Units which were granted under the plan. Each such grant includes a tandem grant of Distribution Equivalent Rights (DERs); vests on the third anniversary of the grant date; and will be payable to the grantee in cash, but may be settled in common units at the discretion of the Partnership’s Board of Directors, upon vesting in an amount equal to the sum of the fair market value of the units (as defined in the plan) that vest on the vesting date, less applicable taxes. The vested amount then credited to the grantee’s DERs account is payable only in cash, less applicable taxes. The economic value of the Phantom Common Units is directly tied to the value of the Partnership’s common units, but these awards do not confer any rights of ownership to the grantee. The fair value of the awards will be recognized ratably over the vesting period and remeasured each quarter until settlement based on the market price of the Partnership’s common units and amounts credited under the DERs. The Partnership has not made any grants of units, restricted units, unit options or UARs under the plan. A summary of the status of the Phantom Common Units granted under the Partnership’s LTIP as of December 31, 2015 and 2014 , and changes during the years ended December 31, 2015 and 2014 , is presented below: Phantom Common Units Total Fair Value (in millions) Weighted-Average Vesting Period (in years) Outstanding at January 1, 2014 (1) 380,048 $ 10.9 1.5 Paid (171,411 ) (3.5 ) — Forfeited (8,968 ) — — Outstanding at December 31, 2014 (1) 199,669 4.1 0.9 Granted 647,256 10.1 2.4 Paid (196,748 ) (2.9 ) — Forfeited (4,209 ) — — Outstanding at December 31, 2015 (1) 645,968 $ 8.7 1.5 (1) Represents fair value and remaining weighted-average vesting period of outstanding awards at the end of the period. The fair value of the awards at the date of grant was based on the closing market price of the Partnership’s common units on or directly preceding the date of grant. The fair value of the awards at December 31, 2015 and 2014 , was based on the closing market price of the common unit on those dates of $12.98 and $17.77 plus the accumulated value of the DERs. The fair value of the awards will be recognized ratably over the vesting period and remeasured each quarter until settlement in accordance with the treatment of awards classified as liabilities. The Partnership recorded $3.6 million , $1.2 million and $3.2 million in Administrative and general expenses during 2015 , 2014 and 2013 for the ratable recognition of the fair value of the Phantom Common Unit awards. The total estimated remaining unrecognized compensation expense related to the Phantom Common Units outstanding at December 31, 2015 and 2014 , was $5.5 million and $1.6 million . In 2015 and 2014 , the general partner purchased 12,180 and 16,064 of the Partnership’s common units in the open market at a price of $16.57 and $12.51 per unit. These units were granted under the LTIP to the independent directors as part of their director compensation. At December 31, 2015 , 3,477,980 units were available for grants under the LTIP. UAR and Cash Bonus Plan The UAR and Cash Bonus Plan provides for grants of UARs and Long-Term Cash Bonuses to selected employees of the Partnership. In 2014, the Partnership granted to certain employees $9.2 million of Long-Term Cash Bonuses under the UAR and Cash Bonus Plan. Each Long-Term Cash Bonus will become vested and payable to the holder in cash equal to the amount of the grant after the vesting date. Except in limited circumstances, upon termination of employment during the vesting period, any outstanding and unvested awards of Long-Term Cash Bonuses would be cancelled unpaid. The Partnership recorded compensation expense of $2.8 million , $2.6 million and $0.5 million for the years ended December 31, 2015 , 2014 and 2013 , related to the Long-Term Cash Bonuses. As of December 31, 2015 , there was $3.6 million of total unrecognized compensation cost related to the Long-Term Cash Bonuses. In 2014, the Partnership’s common unit price decreased significantly primarily due to a reduction in the quarterly cash distribution. As a result, the UARs had no value at December 31, 2014, and continued to have no value until they expired in December 2015. The Partnership recognized no compensation expense related to the UARs for the year ended December 31, 2015 . Due to the significant decrease in the Partnership’s common unit price in 2014 , the Partnership reversed $0.7 million of the previously recognized compensation expense for the year ended December 31, 2014. The Partnership recorded compensation expense of $0.9 million for the year ended December 31, 2013 , related to the UARs. Retention Payment Agreements In light of challenging market conditions, the need to execute on certain key initiatives and a highly competitive market for talent in the energy industry, in 2014, the Partnership entered into retention payment agreements with certain key employees. The total amount of cash payable under the program would be approximately $12.0 million , subject to the employees remaining employed by the Partnership over a period of three years and other conditions. Each retention payment agreement will vest and become payable in cash as follows: 25% vested and became payable on February 28, 2015 , 25% vesting and coming payable on February 29, 2016 , and the remaining 50% vesting and coming payable on February 28, 2017 . Except in limited circumstances, upon termination of employment during the vesting period, any outstanding and unvested retention payments would be cancelled unpaid. Retention payments of $2.9 million were made on March 6, 2015. The Partnership recorded compensation expense of $3.8 million and $4.8 million for the years ended December 31, 2015 and 2014, and as of December 31, 2015, there was $3.1 million of total unrecognized compensation expense related to the retention payment agreements.

Cash Distributions and Net Inco

Cash Distributions and Net Income per Unit	12 Months Ended
	Dec. 31, 2015
Partners' Capital Notes [Abstract]
Cash Distributions and Net Income per Unit [Text Block]	Cash Distributions and Net Income per Unit Cash Distributions The Partnership’s cash distribution policy requires that the Partnership distribute to its various ownership interests on a quarterly basis all of its available cash, as defined in its partnership agreement. IDRs, which represent a limited partner ownership interest and are currently held by the Partnership’s general partner, represent the contractual right to receive an increasing percentage of quarterly distributions of available cash as follows: Total Quarterly Distributions Marginal Percentage Interest in Distributions Target Amount Limited Partner Unitholders General Partner and IDRs First Target Distribution up to $0.4025 98% 2% Second Target Distribution above $0.4025 up to $0.4375 85% 15% Third Target Distribution above $0.4375 up to $0.5250 75% 25% Thereafter above $0.5250 50% 50% The Partnership has declared quarterly distributions per unit to unitholders of record, including holders of common and class B units (through October 9, 2013), and the 2% general partner interest and IDRs held by its general partner as follows (in millions, except distribution per unit): Payment Date Distribution per Unit Amount Paid to Common Unitholders Amount Paid to Class B Unitholder Amount Paid to General Partner (Including IDRs) (1) November 19, 2015 $ 0.1000 $ 25.0 $ — $ 0.5 August 20, 2015 0.1000 25.1 — 0.5 May 21, 2015 0.1000 25.1 — 0.5 February 26, 2015 0.1000 24.3 — 0.5 November 20, 2014 0.1000 24.3 — 0.5 August 21, 2014 0.1000 24.3 — 0.5 May 15, 2014 0.1000 24.3 — 0.5 February 27, 2014 0.1000 24.3 — 0.5 November 14, 2013 0.5325 129.5 — (2) 12.4 August 15, 2013 0.5325 117.3 6.9 11.4 May 16, 2013 0.5325 110.6 6.8 10.7 February 28, 2013 0.5325 110.6 6.9 10.8 (1) In February 2014, the Partnership decreased its distribution rate to $0.10 per common unit. As a result of the reduced distribution rate, the quarterly target distribution levels for IDR payout were not met and the Partnership paid no amounts with respect to the IDRs in 2015 and 2014 . In 2013 , the Partnership paid $34.6 million in distributions on behalf of IDRs. (2) On October 9, 2013, all of the 22.9 million Class B units were converted into common units on a one-for-one basis, pursuant to the terms of the partnership agreement. In February 2016, 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. 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. Under the Partnership’s partnership agreement, for any quarterly period, the IDRs participate in net income only to the extent of the amount of cash distributions actually declared, thereby excluding the IDRs from participating in undistributed net income or losses. Accordingly, undistributed net income is assumed to be allocated to the other ownership interests on a pro rata basis, except that the class B units’ participation in net income was limited to $0.30 per unit per quarter. The Class B units were converted to common units on a one-for-one basis in October 2013. 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. Unless noted otherwise, basic and diluted net income per unit are the same. 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 year ended December 31, 2015 (in millions, except per unit data): Total Common Units General Partner and IDRs Net income $ 222.0 Less: Net loss attributable to noncontrolling interests — Net income attributable to controlling interests 222.0 Declared distribution 102.2 $ 100.2 $ 2.0 Assumed allocation of undistributed net income 119.8 117.3 2.5 Assumed allocation of net income attributable to limited partner unitholders and general partner $ 222.0 $ 217.5 $ 4.5 Weighted-average units outstanding 248.8 Net income per unit $ 0.87 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 year ended December 31, 2014 (in millions, except per unit data): Total Common Units General Partner and IDRs Net income $ 146.8 Less: Net loss attributable to noncontrolling interests (86.8 ) Net income attributable to controlling interests 233.6 Declared distribution 99.2 $ 97.2 $ 2.0 Assumed allocation of undistributed net income 134.4 131.7 2.7 Assumed allocation of net income attributable to limited partner unitholders and general partner $ 233.6 $ 228.9 $ 4.7 Weighted-average units outstanding 243.3 Net income per unit $ 0.94 The following table provides a reconciliation of net income and the assumed allocation of net income to the common and class B units for purposes of computing net income per unit for the year ended December 31, 2013 . Basic net income per unit is calculated based on the weighted-average number of units outstanding for the period. Diluted net income per unit is calculated assuming that the class B units converted on the date that they became convertible, or July 1, 2013 (in millions, except per unit data): Total Common Units Class B Units General Partner and IDRs Net income $ 250.2 Less: Net loss attributable to noncontrolling interests (3.5 ) Net income attributable to controlling interests 253.7 Declared distribution 430.5 $ 381.8 $ 13.7 $ 35.0 Assumed allocation of undistributed net loss (basic) (176.8 ) (160.5 ) (12.8 ) (3.5 ) Assumed allocation of net income attributable to limited partner unitholders and general partner — basic 253.7 221.3 0.9 31.5 Allocation for diluted earnings per unit — (4.6 ) 4.6 — Assumed allocation of net income attributable to limited $ 253.7 $ 216.7 $ 5.5 $ 31.5 Weighted-average units outstanding — basic 220.5 17.6 Weighted-average units outstanding — diluted 226.8 11.3 Net income per unit — basic $ 1.00 $ 0.05 Net income per unit — diluted $ 0.96 $ 0.48

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes [Text Block]	Income Taxes The Partnership is not a taxable entity for federal income tax purposes. As such, it does not directly pay federal income tax. The Partnership’s taxable income or loss, which may vary substantially from the net income or loss reported in the Consolidated Statements of Income, is includable in the federal income tax returns of each partner. The aggregate difference in the basis of the Partnership’s net assets for financial and income tax purposes cannot be readily determined as the Partnership does not have access to the information about each partner’s tax attributes. The subsidiaries of the Partnership directly incur some income-based state taxes which are presented in Income taxes on the Consolidated Statements of Income. Following is a summary of the provision for income taxes for the periods ended December 31, 2015 , 2014 and 2013 (in millions): For the Year Ended December 31, 2015 2014 2013 Current expense: State $ 0.4 $ 0.3 $ 0.4 Total 0.4 0.3 0.4 Deferred provision: State 0.1 0.1 0.1 Total 0.1 0.1 0.1 Income taxes $ 0.5 $ 0.4 $ 0.5 The Partnership’s tax years 2012 through 2015 remain subject to examination by the Internal Revenue Service and the states in which it operates. There were no differences between the provision at the statutory rate to the income tax provision at December 31, 2015 , 2014 and 2013 . As of December 31, 2015 and 2014 , there were no significant deferred income tax assets or liabilities.

Credit Risk

Credit Risk	12 Months Ended
	Dec. 31, 2015
Risks and Uncertainties [Abstract]
Credit Risk [Text Block]	Credit Risk Major Customers For the year ended December 31, 2015, no customer comprised more than 10% of the Partnership’s operating revenues. For the years ended December 31, 2014 and 2013, the Partnership earned $120.5 million and $127.1 million of operating revenues from Devon Gas Services, LP, which represented 10% and 11% of total operating revenues. Natural gas producers comprise a significant portion of the Partnership’s revenues and support several of the Partnership’s growth projects. For example, in 2015, approximately 50% of revenues were generated from contracts with natural gas producers. During 2015, the prices of oil and natural gas declined significantly from an increase in supplies mainly from shale production areas in the U.S. Should the prices of natural gas and oil remain at current levels for a sustained period of time, or decline further, the Partnership could be exposed to increased credit risk associated with its producer customer group. The Partnership continues to monitor credit risk carefully, especially as it relates to customers that may be affected by the current oil and natural gas markets. Gas Loaned to Customers Natural gas price volatility can cause changes in credit risk related to gas and NGLs loaned to customers. As of December 31, 2015 , the amount of gas owed to the operating subsidiaries due to gas imbalances and gas loaned under PAL agreements was approximately 7.7 trillion British thermal units (TBtu). Assuming an average market price during December 2015 of $1.86 per million British thermal units (MMBtu), the market value of that gas was approximately $14.3 million . As of December 31, 2015 , the amount of NGLs owed to the operating subsidiaries due to imbalances was less than 0.1 million barrels (MMBbls), which had a market value of approximately $0.2 million . As of December 31, 2014 , the amount of gas owed to the operating subsidiaries due to gas imbalances and gas loaned under PAL agreements was approximately 10.0 TBtu. Assuming an average market price during December 2014 of $3.36 per MMBtu, the market value of that gas at December 31, 2014 , would have been approximately $33.6 million . As of December 31, 2014 , the amount of NGLs owed to the operating subsidiaries due to imbalances was less than 0.1 MMBbls, which had a market value of approximately $0.6 million . If any significant customer should have credit or financial problems resulting in a delay or failure to repay the gas owed to the operating subsidiaries, it could have a material adverse effect on the Partnership’s financial condition, results of operations or cash flows.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2015
Related Party Transactions [Abstract]
Related Party Transactions [Text Block]	Related Party Transactions Loews provides a variety of corporate services to the Partnership under services agreements, including but not limited to, information technology, tax, risk management, internal audit and corporate development services, plus allocated overheads. The Partnership incurred charges related to these services of $8.8 million , $8.8 million and $8.3 million for the years ended December 31, 2015 , 2014 and 2013 . Distributions paid related to limited partner units held by BPHC and the 2% general partner interest and IDRs held by Boardwalk GP were $52.2 million , $52.0 million and $296.8 million for the years ended December 31, 2015 , 2014 and 2013 . In 2014, the Partnership and BPHC entered into a Subordinated Loan agreement whereby the Partnership can borrow up to $300.0 million . Note 10 contains more information related to the affiliated long-term debt. In 2013, the Partnership entered into agreements with BPHC to form two entities for the purpose of investing in the Bluegrass Project. For the years ended December 31, 2014 and 2013 , the Partnership contributed $0.8 million and $11.9 million and BPHC contributed $8.2 million and $90.0 million of cash and other assets to these entities. In 2014 , the Partnership and BPHC dissolved these entities, resulting in the Partnership receiving $2.2 million in distributions and BPHC receiving $7.9 million in distributions. Refer to Note 3 for further information on the Bluegrass Project.

Supplemental Disclosure of Cash

Supplemental Disclosure of Cash Flow Information	12 Months Ended
	Dec. 31, 2015
Supplemental Cash Flow Elements [Abstract]
Supplemental Disclosure of Cash Flow Information [Text Block]	Supplemental Disclosure of Cash Flow Information (in millions): For the Year Ended December 31, 2015 2014 2013 Cash paid during the period for: Interest (net of amount capitalized) $ 170.6 $ 153.0 $ 151.0 Income taxes, net 0.3 0.1 0.3 Non-cash adjustments: Accounts payable and PPE 54.7 36.9 38.1 Capital lease obligations incurred — — 10.5

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Data [Abstract]
Selected Quarterly Financial Data (Unaudited) [Text Block]	Selected Quarterly Financial Data (Unaudited) The following tables summarize selected quarterly financial data for 2015 and 2014 for the Partnership (in millions, except for earnings per unit): 2015 For the Quarter Ended: December 31 September 30 June 30 March 31 Operating revenues $ 326.8 $ 294.1 $ 298.6 $ 329.7 Operating expenses 220.4 213.4 212.7 206.9 Operating income 106.4 80.7 85.9 122.8 Interest expense, net 42.1 43.0 45.8 45.1 Other income (1.4 ) (0.7 ) (0.4 ) (0.2 ) Income before income taxes 65.7 38.4 40.5 77.9 Income taxes 0.1 0.1 0.1 0.2 Net income 65.6 38.3 40.4 77.7 Net earnings (loss) attributable to noncontrolling interests — — — — Net income attributable to controlling interests $ 65.6 $ 38.3 $ 40.4 $ 77.7 Net income per unit: $ 0.26 $ 0.15 $ 0.16 $ 0.31 2014 For the Quarter Ended: December 31 September 30 June 30 March 31 Operating revenues $ 304.6 $ 278.9 $ 293.4 $ 356.9 Operating expenses 224.1 210.4 196.9 204.3 Operating income 80.5 68.5 96.5 152.6 Interest expense, net 44.2 39.9 40.0 40.8 Other (income) expense (0.6 ) 0.1 0.5 86.0 Income before income taxes 36.9 28.5 56.0 25.8 Income taxes — 0.1 0.1 0.2 Net income 36.9 28.4 55.9 25.6 Net earnings (loss) attributable to 0.1 (0.8 ) (1.5 ) (84.6 ) Net income attributable to $ 36.8 $ 29.2 $ 57.4 $ 110.2 Net income per unit: $ 0.15 $ 0.12 $ 0.23 $ 0.44

Guarantee of Securities of Subs

Guarantee of Securities of Subsidiaries	12 Months Ended
	Dec. 31, 2015
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Guarantee of Securities of Subsidiaries [Text Block]	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 have no significant restrictions on their ability to pay distributions or make loans to the Partnership except as noted in the debt covenants and have no restricted assets at December 31, 2015 and 2014 . Note 10 contains additional information regarding the Partnership's debt and related covenants. Condensed Consolidating Balance Sheets as of December 31, 2015 (Millions) Assets Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Cash and cash equivalents $ — $ 0.3 $ 2.8 $ — $ 3.1 Receivables — — 129.5 — 129.5 Receivables - affiliate — — 7.0 (7.0 ) — Gas and liquids stored underground — — 10.7 — 10.7 Prepayments 0.2 — 16.7 — 16.9 Advances to affiliates — 21.0 107.7 (128.7 ) — Other current assets — — 12.8 (3.2 ) 9.6 Total current assets 0.2 21.3 287.2 (138.9 ) 169.8 Investment in consolidated subsidiaries 2,153.5 7,067.6 — (9,221.1 ) — Property, plant and equipment, gross 0.6 — 9,706.0 — 9,706.6 Less–accumulated depreciation and amortization 0.6 — 2,051.6 — 2,052.2 Property, plant and equipment, net — — 7,654.4 — 7,654.4 Other noncurrent assets 0.4 3.0 472.7 — 476.1 Advances to affiliates – noncurrent 2,190.2 466.3 1,113.4 (3,769.9 ) — Total other assets 2,190.6 469.3 1,586.1 (3,769.9 ) 476.1 Total Assets $ 4,344.3 $ 7,558.2 $ 9,527.7 $ (13,129.9 ) $ 8,300.3 Liabilities and Partners' Capital Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Payables $ 0.3 $ 0.1 $ 118.2 $ — $ 118.6 Payable to affiliates 1.3 — 7.0 (7.0 ) 1.3 Advances from affiliates — 107.7 21.0 (128.7 ) — Other current liabilities — 20.9 176.8 (3.2 ) 194.5 Total current liabilities 1.6 128.7 323.0 (138.9 ) 314.4 Long-term debt and capital lease obligation — 1,972.4 1,486.9 — 3,459.3 Payable to affiliate - noncurrent 16.0 — — — 16.0 Advances from affiliates - noncurrent — 3,303.6 466.3 (3,769.9 ) — Other noncurrent liabilities — — 183.9 — 183.9 Total other liabilities and deferred credits 16.0 3,303.6 650.2 (3,769.9 ) 199.9 Total partners’ capital 4,326.7 2,153.5 7,067.6 (9,221.1 ) 4,326.7 Total Liabilities and Partners' Capital $ 4,344.3 $ 7,558.2 $ 9,527.7 $ (13,129.9 ) $ 8,300.3 Condensed Consolidating Balance Sheets as of December 31, 2014 (Millions) Assets Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Cash and cash equivalents $ 0.5 $ 1.8 $ 4.3 $ — $ 6.6 Receivables — — 110.9 — 110.9 Receivables - affiliate — — 9.0 (9.0 ) — Gas and liquids stored underground — — 4.1 — 4.1 Prepayments 0.1 — 14.4 — 14.5 Advances to affiliates — 6.3 106.2 (112.5 ) — Other current assets 0.5 — 19.2 (6.2 ) 13.5 Total current assets 1.1 8.1 268.1 (127.7 ) 149.6 Investment in consolidated subsidiaries 1,970.6 6,744.1 — (8,714.7 ) — Property, plant and equipment, gross 0.6 — 9,355.0 — 9,355.6 Less–accumulated depreciation and amortization 0.6 — 1,765.8 — 1,766.4 Property, plant and equipment, net — — 7,589.2 — 7,589.2 Other noncurrent assets — 1.7 454.4 (0.6 ) 455.5 Advances to affiliates – noncurrent 2,148.3 212.0 996.5 (3,356.8 ) — Total other assets 2,148.3 213.7 1,450.9 (3,357.4 ) 455.5 Total Assets $ 4,120.0 $ 6,965.9 $ 9,308.2 $ (12,199.8 ) $ 8,194.3 Liabilities and Partners' Capital Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Payables $ 0.2 $ 0.1 $ 61.8 $ — $ 62.1 Payable to affiliates 1.5 — 9.0 (9.0 ) 1.5 Advances from affiliates — 106.2 6.3 (112.5 ) — Other current liabilities — 21.4 141.7 (6.5 ) 156.6 Total current liabilities 1.7 127.7 218.8 (128.0 ) 220.2 Long-term debt and capital lease obligation — 1,722.8 1,954.4 — 3,677.2 Payable to affiliate - noncurrent 16.0 — — — 16.0 Advances from affiliates - noncurrent — 3,144.8 212.0 (3,356.8 ) — Other noncurrent liabilities — — 178.9 (0.3 ) 178.6 Total other liabilities and deferred credits 16.0 3,144.8 390.9 (3,357.1 ) 194.6 Total partners’ capital 4,102.3 1,970.6 6,744.1 (8,714.7 ) 4,102.3 Total Liabilities and Partners' Capital $ 4,120.0 $ 6,965.9 $ 9,308.2 $ (12,199.8 ) $ 8,194.3 Condensed Consolidating Statements of Income for the Year Ended December 31, 2015 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Operating Revenues: Transportation $ — $ — $ 1,178.5 $ (87.4 ) $ 1,091.1 Parking and lending — — 11.6 (0.2 ) 11.4 Storage — — 81.3 — 81.3 Other — — 65.4 — 65.4 Total operating revenues — — 1,336.8 (87.6 ) 1,249.2 Operating Costs and Expenses: Fuel and transportation — — 186.9 (87.6 ) 99.3 Operation and maintenance — — 209.5 — 209.5 Administrative and general — — 130.4 — 130.4 Other operating costs and expenses 0.3 — 413.9 — 414.2 Total operating costs and expenses 0.3 — 940.7 (87.6 ) 853.4 Operating (loss) income (0.3 ) — 396.1 — 395.8 Other Deductions (Income): Interest expense — 104.0 72.4 — 176.4 Interest (income) expense-affiliates, net (28.8 ) 38.2 (9.4 ) — — Interest income — — (0.4 ) — (0.4 ) Equity in earnings of subsidiaries (193.5 ) (335.7 ) — 529.2 — Miscellaneous other income, net — — (2.7 ) — (2.7 ) Total other (income) deductions (222.3 ) (193.5 ) 59.9 529.2 173.3 Income (loss) before income taxes 222.0 193.5 336.2 (529.2 ) 222.5 Income taxes — — 0.5 — 0.5 Net income (loss) $ 222.0 $ 193.5 $ 335.7 $ (529.2 ) $ 222.0 Condensed Consolidating Statements of Income for the Year Ended December 31, 2014 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Operating Revenues: Transportation $ — $ — $ 1,157.9 $ (92.8 ) $ 1,065.1 Parking and lending — — 23.3 — 23.3 Storage — — 90.4 (0.9 ) 89.5 Other — — 55.9 — 55.9 Total operating revenues — — 1,327.5 (93.7 ) 1,233.8 Operating Costs and Expenses: Fuel and transportation — — 218.4 (93.7 ) 124.7 Operation and maintenance — — 194.8 — 194.8 Administrative and general 0.2 — 124.8 — 125.0 Other operating costs and expenses 0.2 — 391.0 — 391.2 Total operating costs and expenses 0.4 — 929.0 (93.7 ) 835.7 Operating (loss) income (0.4 ) — 398.5 — 398.1 Other Deductions (Income): Interest expense — 76.5 89.0 — 165.5 Interest (income) expense - affiliates, net (30.0 ) 41.2 (11.2 ) — — Interest income — — (0.6 ) — (0.6 ) Equity in earnings of subsidiaries (204.0 ) (321.7 ) — 525.7 — Equity losses in unconsolidated affiliates — — 86.5 — 86.5 Miscellaneous other income, net — — (0.5 ) — (0.5 ) Total other (income) deductions (234.0 ) (204.0 ) 163.2 525.7 250.9 Income (loss) before income taxes 233.6 204.0 235.3 (525.7 ) 147.2 Income taxes — — 0.4 — 0.4 Net income (loss) 233.6 204.0 234.9 (525.7 ) 146.8 Net loss attributable to noncontrolling interests — — (86.8 ) — (86.8 ) Net income (loss) attributable to controlling $ 233.6 $ 204.0 $ 321.7 $ (525.7 ) $ 233.6 Condensed Consolidating Statements of Income for the Year Ended December 31, 2013 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Operating Revenues: Transportation $ — $ — $ 1,116.4 $ (88.4 ) $ 1,028.0 Parking and lending — — 24.0 (0.1 ) 23.9 Storage — — 111.0 (0.1 ) 110.9 Other — — 42.8 — 42.8 Total operating revenues — — 1,294.2 (88.6 ) 1,205.6 Operating Costs and Expenses: Fuel and transportation — — 185.8 (88.6 ) 97.2 Operation and maintenance — 0.3 182.4 — 182.7 Administrative and general (0.1 ) 0.8 116.7 — 117.4 Other operating costs and expenses 0.3 0.1 393.4 — 393.8 Total operating costs and expenses 0.2 1.2 878.3 (88.6 ) 791.1 Operating (loss) income (0.2 ) (1.2 ) 415.9 — 414.5 Other Deductions (Income): Interest expense — 72.7 90.7 — 163.4 Interest (income) expense - affiliates, net (33.6 ) 41.3 (7.7 ) — — Interest income — — (0.5 ) — (0.5 ) Equity in earnings of subsidiaries (220.3 ) (335.5 ) — 555.8 — Equity losses in unconsolidated affiliates — — 1.2 — 1.2 Miscellaneous other income, net — — (0.3 ) — (0.3 ) Total other (income) deductions (253.9 ) (221.5 ) 83.4 555.8 163.8 Income (loss) before income taxes 253.7 220.3 332.5 (555.8 ) 250.7 Income taxes — — 0.5 — 0.5 Net income (loss) 253.7 220.3 332.0 (555.8 ) 250.2 Net loss attributable to noncontrolling interests — — (3.5 ) — (3.5 ) Net income (loss) attributable to controlling $ 253.7 $ 220.3 $ 335.5 $ (555.8 ) $ 253.7 Condensed Consolidating Statements of Comprehensive Income for the Year Ended December 31, 2015 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net income (loss) $ 222.0 $ 193.5 $ 335.7 $ (529.2 ) $ 222.0 Other comprehensive income (loss): Reclassification adjustment transferred to Net income from cash flow hedges 2.4 2.4 0.7 (3.1 ) 2.4 Pension and other postretirement benefit costs (13.9 ) (13.9 ) (13.9 ) 27.8 (13.9 ) Total Comprehensive Income (Loss) 210.5 182.0 322.5 (504.5 ) 210.5 Comprehensive loss attributable to noncontrolling interests — — — — — Comprehensive income (loss) attributable to controlling interests $ 210.5 $ 182.0 $ 322.5 $ (504.5 ) $ 210.5 Condensed Consolidating Statements of Comprehensive Income for the Year Ended December 31, 2014 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net income (loss) $ 233.6 $ 204.0 $ 234.9 $ (525.7 ) $ 146.8 Other comprehensive (loss) income: (Loss) gain on cash flow hedges (0.7 ) (0.7 ) (0.7 ) 1.4 (0.7 ) Reclassification adjustment transferred to Net income from cash flow hedges 2.6 2.6 0.9 (3.5 ) 2.6 Pension and other postretirement benefit costs (10.9 ) (10.9 ) (10.9 ) 21.8 (10.9 ) Total Comprehensive Income (Loss) 224.6 195.0 224.2 (506.0 ) 137.8 Comprehensive loss attributable to noncontrolling interests — — (86.8 ) — (86.8 ) Comprehensive income (loss) attributable to controlling interests $ 224.6 $ 195.0 $ 311.0 $ (506.0 ) $ 224.6 Condensed Consolidating Statements of Comprehensive Income for the Year Ended December 31, 2013 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net income (loss) $ 253.7 $ 220.3 $ 332.0 $ (555.8 ) $ 250.2 Other comprehensive income (loss): Gain (loss) on cash flow hedges 1.6 1.6 1.6 (3.2 ) 1.6 Reclassification adjustment transferred to Net Income from cash flow hedges 1.2 1.2 (0.5 ) (0.7 ) 1.2 Pension and other postretirement benefit costs 0.7 0.7 0.7 (1.4 ) 0.7 Total Comprehensive Income (Loss) 257.2 223.8 333.8 (561.1 ) 253.7 Comprehensive loss attributable to noncontrolling interests — — (3.5 ) — (3.5 ) Comprehensive income (loss) attributable to controlling interests $ 257.2 $ 223.8 $ 337.3 $ (561.1 ) $ 257.2 Condensed Consolidating Statements of Cash Flow for the Year Ended December 31, 2015 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net cash provided by (used in) operating activities $ 27.9 $ (136.3 ) $ 684.8 $ — $ 576.4 INVESTING ACTIVITIES: Capital expenditures (1.0 ) — (373.5 ) — (374.5 ) Proceeds from sale of operating assets — — 0.8 — 0.8 Proceeds from other recoveries — — 6.2 — 6.2 Advances to affiliates, net (41.9 ) (269.0 ) (118.4 ) 429.3 — Net cash (used in) provided by investing activities (42.9 ) (269.0 ) (484.9 ) 429.3 (367.5 ) FINANCING ACTIVITIES: Proceeds from long-term debt, net of — 247.1 — — 247.1 Repayment of borrowings from long-term — — (725.0 ) — (725.0 ) Proceeds from borrowings on revolving credit agreement — — 1,125.0 — 1,125.0 Repayment of borrowings on revolving credit agreement, including financing fees — (3.6 ) (870.0 ) — (873.6 ) Principal payment of capital lease obligation — — (0.4 ) — (0.4 ) Advances from affiliates, net 0.6 160.3 269.0 (429.3 ) 0.6 Distributions paid (101.5 ) — — — (101.5 ) Proceeds from sale of common units 113.1 — — — 113.1 Capital contributions from general partner 2.3 — — — 2.3 Net cash provided by (used in) financing activities 14.5 403.8 (201.4 ) (429.3 ) (212.4 ) Decrease in cash and cash equivalents (0.5 ) (1.5 ) (1.5 ) — (3.5 ) Cash and cash equivalents at beginning of period 0.5 1.8 4.3 — 6.6 Cash and cash equivalents at end of period $ — $ 0.3 $ 2.8 $ — $ 3.1 Condensed Consolidating Statements of Cash Flow for the Year Ended December 31, 2014 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net cash provided by (used in) operating activities $ 30.2 $ (112.1 ) $ 595.5 $ — $ 513.6 INVESTING ACTIVITIES: Capital expenditures — — (404.4 ) — (404.4 ) Proceeds from sale of operating assets — — 2.9 — 2.9 Proceeds from insurance and other recoveries — — 6.3 — 6.3 Advances to affiliates, net 363.9 (49.6 ) (175.2 ) (139.0 ) 0.1 Investment in unconsolidated affiliates — — (20.5 ) — (20.5 ) Distributions from unconsolidated affiliates — — 11.1 — 11.1 Acquisition of businesses, net of cash acquired (294.7 ) — — — (294.7 ) Net cash provided by (used in) investing activities 69.2 (49.6 ) (579.8 ) (139.0 ) (699.2 ) FINANCING ACTIVITIES: Proceeds from long-term debt, net of issuance cost — 342.9 — — 342.9 Repayment of borrowings from term loan — — (25.0 ) — (25.0 ) Proceeds from borrowings on revolving credit agreement — — 665.0 — 665.0 Repayment of borrowings on revolving credit agreement — — (720.0 ) — (720.0 ) Principal payment of capital lease obligation — — (0.4 ) — (0.4 ) Advances from affiliates, net 0.1 (188.6 ) 49.6 139.0 0.1 Distributions paid (99.2 ) — — — (99.2 ) Capital contributions from noncontrolling interests — — 8.2 — 8.2 Distributions paid to noncontrolling interests — — (7.9 ) — (7.9 ) Net cash (used in) provided by financing activities (99.1 ) 154.3 (30.5 ) 139.0 163.7 Increase (decrease) in cash and cash equivalents 0.3 (7.4 ) (14.8 ) — (21.9 ) Cash and cash equivalents at beginning of period 0.2 9.2 19.1 — 28.5 Cash and cash equivalents at end of period $ 0.5 $ 1.8 $ 4.3 $ — $ 6.6 Condensed Consolidating Statements of Cash Flow for the Year Ended December 31, 2013 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net cash provided by (used in) operating activities $ 33.9 $ (108.8 ) $ 609.2 $ — $ 534.3 INVESTING ACTIVITIES: Capital expenditures — — (294.8 ) — (294.8 ) Proceeds from sale of operating assets — — 60.7 — 60.7 Proceeds from insurance and other recoveries — — 1.4 — 1.4 Advances to affiliates, net 126.4 (84.3 ) (342.8 ) 300.7 — Investment in consolidated affiliates — (15.1 ) — 15.1 — Investment in unconsolidated affiliates — — (76.7 ) — (76.7 ) Net cash provided by (used in) investing activities 126.4 (99.4 ) (652.2 ) 315.8 (309.4 ) FINANCING ACTIVITIES: Proceeds from borrowings on revolving credit agreement — — 1,128.0 — 1,128.0 Repayment of borrowings on revolving credit agreement — — (1,255.0 ) — (1,255.0 ) Contribution from parent — — 15.1 (15.1 ) — Principal payment of capital lease obligation — — (0.2 ) — (0.2 ) Advances from affiliates, net (2.8 ) 216.4 84.3 (300.7 ) (2.8 ) Distributions paid (533.9 ) — — — (533.9 ) Capital contributions from noncontrolling interests — — 87.1 — 87.1 Proceeds from sale of common units 368.7 — — — 368.7 Capital contributions from general partner 7.8 — — — 7.8 Net cash (used in) provided by financing activities (160.2 ) 216.4 59.3 (315.8 ) (200.3 ) Increase in cash and cash equivalents 0.1 8.2 16.3 — 24.6 Cash and cash equivalents at beginning of period 0.1 1.0 2.8 — 3.9 Cash and cash equivalents at end of period $ 0.2 $ 9.2 $ 19.1 $ — $ 28.5

Accounting Policies (Policies)

Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Basis of Presentation [Policy Text Block]	Basis of Presentation The accompanying consolidated financial statements of the Partnership were prepared in accordance with accounting principles generally accepted in the United States of America (GAAP). In 2015, the Partnership began reporting certain operating costs associated with storage activities at its Louisiana Midstream subsidiary in Fuel and transportation expense, whereas those costs were previously reported in Operation and maintenance expense. The change was made to provide better information to users of the financial statements regarding costs that vary based on the utilization of the Partnership’s services. Amounts reported within Total operating costs and expenses in the consolidated Statements of Income for the 2014 and 2013 periods have been adjusted to conform to the current presentation. The effect of the adjustment increased Fuel and transportation expense and decreased Operation and maintenance expense by $4.0 million and $3.8 million for the years ended December 31, 2014 and 2013, with no impact on Total operating costs and expenses , Operating income, Net Income or cash flows from operations . As of December 31, 2015, the Partnership began applying the provisions of Accounting Standards Update 2015-03, Interest-Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs (ASU 2015-03), issued by the Financial Accounting Standards Board (FASB) in April 2015. ASU 2015-03 requires that debt issuance costs be presented on the balance sheet as a deduction from the recognized debt liability rather than as a deferred asset. In accordance with the transition requirements of ASU 2015-03, which require retrospective implementation, the Partnership adjusted the prior year amounts reported on the balance sheet to conform to the current presentation, resulting in a $12.5 million decrease in Other assets and a corresponding decrease in Long-term debt and capital lease obligation as of December 31, 2014.
Principles of Consolidation [Policy Text Block]	Principles of Consolidation The consolidated financial statements include the Partnership’s accounts and those of its wholly-owned subsidiaries after elimination of intercompany transactions. The Partnership also consolidates variable interest entities (VIEs) in which the Partnership is the primary beneficiary. Third party or affiliate ownership interests in the Partnership's subsidiaries and consolidated VIEs are presented as noncontrolling interests. The Partnership applies the equity method of accounting for investments in unconsolidated affiliates in which it owns 20 percent to 50 percent of the voting interests or otherwise exercises significant influence, but not control, over operating and financial policies of the investee. Under this method, the carrying amounts of the Partnership's equity investments are increased by a proportionate share of the investee's net income and contributions made and decreased by a proportionate share of the investee's net losses and distributions received. As of December 31, 2015 and 2014, the Partnership had no equity method investments recorded on its Consolidated Balance Sheets.
Use of Estimates [Policy Text Block]	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, expenses and disclosure of contingent assets and liabilities and the fair values of certain items. The Partnership bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, which form the basis for making judgments about the carrying amounts of assets and liabilities that are not readily apparent from other sources. Actual results could differ from such estimates.
Segment Information [Policy Text Block]	Segment Information The Partnership operates in one reportable segment - the operation of interstate natural gas and NGLs pipeline systems including integrated storage facilities. This segment consists of interstate natural gas pipeline systems which originate in the Gulf Coast region, Oklahoma and Arkansas and extend north and east through the Midwestern states of Tennessee, Kentucky, Illinois, Indiana and Ohio and NGLs pipelines and storage facilities in Louisiana and Texas.
Regulatory Accounting [Policy Text Block]	Regulatory Accounting Most of the Partnership's natural gas pipeline subsidiaries are regulated by the Federal Energy Regulatory Commission (FERC). When certain criteria are met, GAAP requires that certain rate-regulated entities account for and report assets and liabilities consistent with the economic effect of the manner in which independent third-party regulators establish rates (regulatory accounting). This basis of accounting is applicable to operations of the Partnership’s Texas Gas subsidiary which records certain costs and benefits as regulatory assets and liabilities in order to provide for recovery from or refund to customers in future periods, but is not applicable to operations associated with the Fayetteville and Greenville Laterals due to rates charged under negotiated rate agreements and a portion of the storage capacity due to the regulatory treatment associated with the rates charged for that capacity. Regulatory accounting is not applicable to the Partnership’s other FERC-regulated entities. The Partnership monitors the regulatory and competitive environment in which it operates to determine that its regulatory assets continue to be probable of recovery. If the Partnership were to determine that all or a portion of its regulatory assets no longer met the criteria for recognition as regulatory assets, that portion which was not recoverable would be written off, net of any regulatory liabilities. Note 9 contains more information regarding the Partnership’s regulatory assets and liabilities.
Fair Value Measurements [Policy Text Block]	Fair Value Measurements Fair value refers to an exit price that would be received to sell an asset or paid to transfer a liability in an orderly transaction in the principal market in which the reporting entity transacts based on the assumptions market participants would use when pricing the asset or liability assuming its highest and best use. A fair value hierarchy has been established that prioritizes the information used to develop those assumptions giving priority, from highest to lowest, to quoted prices in active markets for identical assets and liabilities (Level 1); observable inputs not included in Level 1, for example, quoted prices for similar assets and liabilities (Level 2); and unobservable data (Level 3), for example, a reporting entity’s own internal data based on the best information available in the circumstances. The Partnership uses fair value measurements to record derivatives, asset retirement obligations and impairments. Fair value measurements are also used to perform goodwill impairment testing and report fair values for certain items contained in this Report. The Partnership considers any transfers between levels within the fair value hierarchy to have occurred at the beginning of a quarterly reporting period. The Partnership did not recognize any transfers between Level 1 and Level 2 of the fair value hierarchy and did not change its valuation techniques or inputs during the year ended December 31, 2015 . Notes 5 and 11 contain more information regarding fair value measurements.
Cash and Cash Equivalents [Policy Text Block]	Cash and Cash Equivalents Cash equivalents are highly liquid investments with an original maturity of three months or less and are stated at cost plus accrued interest, which approximates fair value. The Partnership had no restricted cash at December 31, 2015 and 2014 .
Cash Management [Policy Text Block]	Cash Management The operating subsidiaries participate in an intercompany cash management program with those that are FERC-regulated participating to the extent they are permitted under FERC regulations. Under the cash management program, depending on whether a participating subsidiary has short-term cash surpluses or cash requirements, Boardwalk Pipelines either provides cash to them or they provide cash to Boardwalk Pipelines. The transactions are represented by demand notes and are stated at historical carrying amounts. Interest income and expense are recognized on an accrual basis when collection is reasonably assured. The interest rate on intercompany demand notes is London Interbank Offered Rate (LIBOR) plus one percent and is adjusted every three months.
Trade and Other Receivables [Policy Text Block]	Trade and Other Receivables Trade and other receivables are stated at their historical carrying amount, net of allowances for doubtful accounts. The Partnership establishes an allowance for doubtful accounts on a case-by-case basis when it believes the required payment of specific amounts owed is unlikely to occur. Uncollectible receivables are written off when a settlement is reached for an amount that is less than the outstanding historical balance or a receivable amount is deemed otherwise unrealizable.
Gas Stored Underground and Gas Receivables and Payables [Policy Text Block]	Gas Stored Underground and Gas Receivables and Payables Certain of the Partnership's operating subsidiaries have underground gas in storage which is utilized for system management and operational balancing, as well as for services including firm and interruptible storage associated with certain no-notice (NNS) and parking and lending (PAL) services. Gas stored underground includes the historical cost of natural gas volumes owned by the operating subsidiaries, at times reduced by certain operational encroachments upon that gas. Current gas stored underground represents net retained fuel remaining after providing transportation and storage services which is available for resale and is valued at the lower of weighted-average cost or market. The operating subsidiaries provide storage services whereby they store natural gas or NGLs on behalf of customers and also periodically hold customer gas under PAL services. Since the customers retain title to the gas held by the Partnership in providing these services, the Partnership does not record the related gas on its balance sheet. Certain of the Partnership's operating subsidiaries also periodically lend gas and NGLs to customers. In the course of providing transportation and storage services to customers, the operating subsidiaries may receive different quantities of gas from shippers and operators than the quantities delivered on behalf of those shippers and operators. This results in transportation and exchange gas receivables and payables, commonly known as imbalances, which are primarily settled in cash or the receipt or delivery of gas in the future. Settlement of imbalances requires agreement between the pipelines and shippers or operators as to allocations of volumes to specific transportation contracts and timing of delivery of gas based on operational conditions. The receivables and payables are valued at market price for operations where regulatory accounting is not applicable and are valued at the historical value of gas in storage for operations where regulatory accounting is applicable.
Materials and Supplies [Policy Text Block]	Materials and Supplies Materials and supplies are carried at average cost and are included in Other Assets on the Consolidated Balance Sheets. The Partnership expects its materials and supplies to be used for capital projects related to its property, plant and equipment and for future growth projects. At December 31, 2015 and 2014 , the Partnership held approximately $22.2 million and $15.3 million of materials and supplies which were reflected in Other Assets on the Consolidated Balance Sheets.
Property, Plant and Equipment (PPE) and Repair and Maintenance Costs [Policy Text Block]	Property, Plant and Equipment (PPE) and Repair and Maintenance Costs PPE is recorded at its original cost of construction or fair value of assets purchased. Construction costs and expenditures for major renewals and improvements which extend the lives of the respective assets are capitalized. Construction work in progress is included in the financial statements as a component of PPE. All repair and maintenance costs are expensed as incurred. Depreciation of PPE related to operations for which regulatory accounting does not apply is provided for using the straight-line method of depreciation over the estimated useful lives of the assets, which range from 3 to 35 years. The ordinary sale or retirement of PPE for these assets could result in a gain or loss. Depreciation of PPE related to operations for which regulatory accounting is applicable is provided for primarily on the straight-line method at FERC-prescribed rates over estimated useful lives of 5 to 62 years. Reflecting the application of composite depreciation, gains and losses from the ordinary sale or retirement of PPE for these assets are not recognized in earnings and generally do not impact PPE, net. Note 6 contains more information regarding the Partnership’s PPE.
Goodwill and Intangible Assets [Policy Text Block]	Goodwill and Intangible Assets Goodwill represents the excess of the cost of an acquisition over the fair value of the net identifiable assets acquired and liabilities assumed. Goodwill is tested for impairment at the reporting unit level at least annually, as of November 30, or more frequently when events occur and circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount. Accounting requirements provide that a reporting entity may perform an optional qualitative assessment on an annual basis to determine whether events occurred or circumstances changed that would more likely than not reduce the fair value of a reporting unit below its carrying amount. If an initial qualitative assessment identifies that it is more likely than not that the fair value of a reporting unit is less than its carrying amount, or the optional qualitative assessment is not performed, a quantitative analysis is performed under a two-step impairment test to measure whether the fair value of the reporting unit is less than its carrying amount. If based upon a quantitative analysis the fair value of the reporting unit is less than its carrying amount, including goodwill, the Partnership performs an analysis of the fair value of all the assets and liabilities of the reporting unit. If the implied fair value of the reporting unit's goodwill is determined to be less than its carrying amount, an impairment loss is recognized for the difference. Intangible assets are those assets which provide future economic benefit but have no physical substance. The Partnership recorded intangible assets for customer relationships obtained through its acquisitions. The customer relationships, which are included in Other Assets on the Consolidated Balance Sheets, have a finite life and are being amortized in a systematic and rational manner over their estimated useful lives. Note 7 contains additional information regarding the Partnership's goodwill and intangible assets.
Impairment of Long-Lived Assets (including Tangible and Definite-lived Intangible Assets) [Policy Text Block]	Impairment of Long-lived Assets (including Tangible and Definite-lived Intangible Assets) The Partnership evaluates its long-lived and intangible assets for impairment when, in management’s judgment, events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. When such a determination has been made, management’s estimate of undiscounted future cash flows attributable to the remaining economic useful life of the asset is compared to the carrying amount of the asset to determine whether an impairment has occurred. If an impairment of the carrying amount has occurred, the amount of impairment recognized in the financial statements is determined by estimating the fair value of the assets and recording a loss to the extent that the carrying amount exceeds the estimated fair value.
Capitalized Interest and Allowance for Funds Used During Construction (AFUDC) [Policy Text Block]	Capitalized Interest and Allowance for Funds Used During Construction (AFUDC) The Partnership records capitalized interest, which represents the cost of borrowed funds used to finance construction activities for operations where regulatory accounting is not applicable. The Partnership records AFUDC, which represents the cost of funds, including equity funds, applicable to regulated natural gas transmission plant under construction as permitted by FERC regulatory practices, in connection with the Partnership’s operations where regulatory accounting is applicable. Capitalized interest and the allowance for borrowed funds used during construction are recognized as a reduction to Interest expense and the allowance for equity funds used during construction is included in Miscellaneous other income, net within the Consolidated Statements of Income. The following table summarizes capitalized interest and the allowance for borrowed funds and allowance for equity funds used during construction (in millions): For the Year Ended 2015 2014 2013 Capitalized interest and allowance for borrowed funds used during construction $ 3.4 $ 6.8 $ 6.4 Allowance for equity funds used during construction 2.7 0.5 0.2
Income Taxes [Policy Text Block]	Income Taxes The Partnership is not a taxable entity for federal income tax purposes. As such, it does not directly pay federal income tax. The Partnership’s taxable income or loss, which may vary substantially from the net income or loss reported in the Consolidated Statements of Income, is includable in the federal income tax returns of each partner. The aggregate difference in the basis of the Partnership’s net assets for financial and income tax purposes cannot be readily determined as the Partnership does not have access to the information about each partner’s tax attributes related to the Partnership. The subsidiaries of the Partnership directly incur some income-based state taxes which are presented in Income taxes on the Consolidated Statements of Income. Note 13 contains more information regarding the Partnership’s income taxes.
Revenue Recognition [Policy Text Block]	Revenue Recognition The maximum rates that may be charged by the majority of the Partnership's operating subsidiaries for their services are established through FERC’s cost-based rate-making process; however, rates charged by those operating subsidiaries may be less than those allowed by FERC. Revenues from transportation and storage services are recognized in the period the service is provided based on contractual terms and the related volumes transported or stored. In connection with some PAL and interruptible storage service agreements, cash is received at inception of the service period resulting in the recording of deferred revenues which are recognized in revenues over the period the services are provided. At December 31, 2015 and 2014 , the Partnership had deferred revenues of $10.0 million and $7.2 million , which are expected to be recognized through 2018. Retained fuel is recognized in revenues at market prices in the month of retention for operations where regulatory accounting is not applicable. The related fuel consumed in providing transportation services is recorded in Fuel and transportation expenses at market prices in the month consumed. In some cases, customers may elect to pay cash for the cost of fuel used in providing transportation services instead of having fuel retained in-kind. Retained fuel included in Transportation on the Consolidated Statements of Income for the years ended December 31, 2015 , 2014 and 2013 , was $53.2 million , $90.3 million and $76.9 million . The Partnership has contractual retainage provisions in some of its ethylene storage contracts that provide for the Partnership to retain ownership of 0.5% of customer inventory volumes injected into storage wells. The Partnership may sell the retainage volumes if commercially marketable volumes are on hand. The Partnership recognizes revenue for ethylene retainage volumes upon the physical sale of such volumes. Under FERC regulations, certain revenues that the operating subsidiaries collect may be subject to possible refunds to customers. Accordingly, during a rate case, estimated refund liabilities are recorded considering regulatory proceedings, advice of counsel and estimated risk-adjusted total exposure, as well as other factors. At December 31, 2015 , the Partnership had a $16.3 million refund liability related to the settled Gulf South rate case recorded on the Consolidated Balance Sheets. Refer to Note 4 for further information on the Gulf South rate case. There were no liabilities recorded as of December 31, 2014 , for any open rate case.
Asset Retirement Obligations [Policy Text Block]	Asset Retirement Obligations The accounting requirements for existing legal obligations associated with the future retirement of long-lived assets require entities to record the fair value of a liability for an asset retirement obligation in the period during which the liability is incurred. The liability is initially recognized at fair value and is increased with the passage of time as accretion expense is recorded, until the liability is ultimately settled. The accretion expense is included within Operation and maintenance costs within the Consolidated Statements of Income. An amount corresponding to the amount of the initial liability is capitalized as part of the carrying amount of the related long-lived asset and depreciated over the useful life of that asset. Note 8 contains more information regarding the Partnership’s asset retirement obligations.
Environmental Liabilities [Policy Text Block]	Environmental Liabilities The Partnership records environmental liabilities based on management’s estimates of the undiscounted future obligation for probable costs associated with environmental assessment and remediation of operating sites. These estimates are based on evaluations and discussions with counsel and operating personnel and the current facts and circumstances related to these environmental matters. Note 4 contains more information regarding the Partnership’s environmental liabilities.
Defined Benefit Plans [Policy Text Block]	Defined Benefit Plans The Partnership maintains certain postretirement benefit plans for certain employees. The Partnership funds these plans through periodic contributions which are invested until the benefits are paid out to the participants. The net benefit cost of the plan is recorded in the Consolidated Statements of Income. The Partnership records an asset or liability based on the overfunded or underfunded status of the plan. Any deferred amounts related to unrecognized gains and losses or changes in actuarial assumptions are recorded as either a regulatory asset or liability or recorded as a component of accumulated other comprehensive income (AOCI) until those gains or losses are recognized in the Consolidated Statements of Income. Note 11 contains more information regarding the Partnership’s pension and postretirement benefit obligations.
Unit-Based and Other Long-Term Compensation [Policy Text Block]	Unit-Based and Other Long-Term Compensation The Partnership provides awards of phantom common units (Phantom Common Units) to certain employees under its Long-Term Incentive Plan (LTIP). The Partnership also provides to certain employees awards of unit appreciation rights (UARs) and long-term cash bonuses (Long-Term Cash Bonuses) under the Boardwalk Pipeline Partners Unit Appreciation Rights and Cash Bonus Plan. In 2014, the Partnership entered into retention payment agreements with certain key employees. The Partnership measures the cost of an award issued in exchange for employee services based on the grant-date fair value of the award, or the stated amount in the case of the Long-Term Cash Bonuses and amounts under retention payment agreements. All outstanding awards are required to be settled in cash and are classified as a liability until settlement. The unit-based compensation awards are remeasured each reporting period until the final amount of awards is determined. The related compensation expense, less applicable estimates of forfeitures, is recognized over the period that employees are required to provide services in exchange for the awards, usually the vesting period. Note 11 contains additional information regarding the Partnership’s unit-based and other long-term compensation.
Partner Capital Accounts [Policy Text Block]	Partner Capital Accounts For purposes of maintaining capital accounts, items of income and loss of the Partnership are allocated among the partners each year, or portion thereof, in accordance with the partnership agreement. Generally, net income for each period is allocated among the partners based on their respective ownership interests after deducting any priority allocations in the form of cash distributions paid to the general partner as the holder of IDRs.
Derivative Financial Instruments [Policy Text Block]	Derivative Financial Instruments The Partnership occasionally uses futures, swaps and option contracts (collectively, derivatives) to hedge exposure to various risks, including natural gas commodity and interest rate risk. The effective portion of the related unrealized gains and losses resulting from changes in fair values of the derivatives contracts designated as cash flow hedges are deferred as a component of AOCI. The deferred gains and losses are recognized in earnings when the hedged anticipated transactions affect earnings. Changes in fair value of derivatives that are not designated as cash flow hedges are recognized in earnings in the periods that those changes in fair value occur. Note 5 contains more information regarding the Partnership’s derivative financial instruments.
Recently Issued Accounting Pronouncements [Policy Text Block]	Recently Issued Accounting Pronouncements In May 2014, the Financial Accounting Standards Board issued Accounting Standards Update 2014-09 (ASU 2014-09), Revenue from Contracts with Customers (Topic 606), 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. T he Partnership has initiated a project to evaluate the impact, if any, that ASU 2014-09 will have on its financial statements. However, no conclusions have been reached, including with regard to the application methodology.

Accounting Policies (Tables)

Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Summary of Capitalized Interest and Allowance for borrowed Funds [Table Text Block]	The following table summarizes capitalized interest and the allowance for borrowed funds and allowance for equity funds used during construction (in millions): For the Year Ended 2015 2014 2013 Capitalized interest and allowance for borrowed funds used during construction $ 3.4 $ 6.8 $ 6.4 Allowance for equity funds used during construction 2.7 0.5 0.2

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Operating Leases of Lessee Disclosure [Table Text Block]	The following table summarizes minimum future commitments related to these items at December 31, 2015 (in millions): 2016 $ 4.6 2017 4.2 2018 3.7 2019 3.2 2020 3.1 Thereafter 11.5 Total $ 30.3
Pipeline Capacity Agreements [Table Text Block]	The future commitments related to pipeline capacity agreements as of December 31, 2015 , were (in millions): 2016 $ 6.4 2017 6.2 2018 2.0 2019 — 2020 — Thereafter — Total $ 14.6
Capital Lease [Table Text Block]	Future commitments under this capital lease are as follows (in millions): 2016 $ 1.0 2017 1.0 2018 1.0 2019 1.1 2020 1.1 Thereafter 8.5 Total minimum lease payments 13.7 Less amounts representing interest (4.1 ) Present value of obligation under capital lease 9.6 Less: current portion of obligations under capital lease (recorded in Other current liabilities ) (0.5 ) Long-term obligations under capital lease $ 9.1

Other Comprehensive Income (O30

Other Comprehensive Income (OCI) and Fair Value Measurements Accumulated Other Comprehensive Income (Loss) Net of Tax (Tables)	12 Months Ended
	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	The following table shows the components and reclassifications to net income of Accumulated other comprehensive loss which is included in Partners' Capital on the Consolidated Balance Sheets for the years ended December 31, 2013 through 2015 (in millions): Cash Flow Hedges Pension and Other Postretirement Costs Total Beginning balance, January 1, 2013 $ (15.5 ) $ (51.8 ) $ (67.3 ) Gain recorded in accumulated other comprehensive loss 1.6 — 1.6 Reclassifications: Transportation operating revenues 0.1 — 0.1 Other operating revenues (0.1 ) — (0.1 ) Disposal of operating assets (1.2 ) — (1.2 ) Interest expense (1) 2.4 — 2.4 Pension and other postretirement benefit costs — 0.7 0.7 Ending balance, December 31, 2013 $ (12.7 ) $ (51.1 ) $ (63.8 ) Loss recorded in accumulated other comprehensive loss (0.7 ) — (0.7 ) Reclassifications: Other operating revenues 0.2 — 0.2 Interest expense (1) 2.4 — 2.4 Pension and other postretirement benefit costs — (10.9 ) (10.9 ) Ending balance, December 31, 2014 $ (10.8 ) $ (62.0 ) $ (72.8 ) Reclassifications: Interest expense (1) 2.4 — 2.4 Pension and other postretirement benefit costs — (13.9 ) (13.9 ) Ending balance, December 31, 2015 $ (8.4 ) $ (75.9 ) $ (84.3 ) (1) Related to amounts deferred in AOCI from the treasury rate locks described above.

Other Comprehensive Income (O31

Other Comprehensive Income (OCI) and Fair Value Measurements Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value, by Balance Sheet Grouping [Table Text Block]	The carrying amount and estimated fair values of the Partnership's financial assets and liabilities which were not recorded at fair value on the Consolidated Balance Sheets as of December 31, 2015 and 2014 , were as follows (in millions): As of December 31, 2015 Estimated Fair Value Financial Assets Carrying Amount Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 3.1 $ 3.1 $ — $ — $ 3.1 Financial Liabilities Long-term debt $ 3,460.6 (1) $ — $ 3,299.7 $ — $ 3,299.7 (1) The carrying amount of long-term debt excludes a $9.1 million long-term capital lease obligation and $10.4 million of unamortized debt issuance costs. As of December 31, 2014 Estimated Fair Value Financial Assets Carrying Amount Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 6.6 $ 6.6 $ — $ — $ 6.6 Financial Liabilities Long-term debt $ 3,680.1 (1) $ — $ 3,787.4 $ — $ 3,787.4 (1) The carrying amount of long-term debt excludes a $9.6 million long-term capital lease obligation and $12.5 million of unamortized debt issuance costs.

Property, Plant and Equipment32

Property, Plant and Equipment (PPE) (Tables)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment [Table Text Block]	The following table presents the Partnership’s PPE as of December 31, 2015 and 2014 (in millions): Category 2015 Weighted-Average Useful Lives (Years) 2014 Weighted-Average Useful Lives (Years) Depreciable plant: Transmission $ 7,930.3 37 $ 7,719.8 37 Storage 769.5 38 758.5 38 Gathering 347.6 27 336.7 27 General 182.8 13 170.0 14 Rights of way and other 122.5 37 114.9 36 Total utility depreciable plant 9,352.7 37 9,099.9 37 Non-depreciable: Construction work in progress 201.9 105.5 Storage 105.5 105.5 Land 30.2 28.4 Other 16.3 16.3 Total non-depreciable assets 353.9 255.7 Total PPE 9,706.6 9,355.6 Less: accumulated depreciation 2,052.2 1,766.4 Total PPE, net $ 7,654.4 $ 7,589.2
Gross PPE Investments and Related Accumulated Depreciation [Table Text Block]	The following table presents the gross PPE investment and related accumulated depreciation for the Partnership’s undivided interests as of December 31, 2015 and 2014 (in millions): 2015 2014 Gross PPE Investment Accumulated Depreciation Gross PPE Investment Accumulated Depreciation Bistineau storage $ 68.9 $ 19.5 $ 64.3 $ 17.5 Mobile Bay Pipeline 13.2 5.1 13.0 3.6 NGL pipelines and facilities 34.8 3.2 34.8 2.2 Offshore and other assets 17.1 12.8 18.8 13.7 Total $ 134.0 $ 40.6 $ 130.9 $ 37.0

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Finite-Lived Intangible Assets [Table Text Block]	The following table contains information regarding the Partnership's intangible assets, which includes customer relationships acquired as part of its acquisitions (in millions): December 31, 2015 2014 Gross carrying amount $ 59.4 $ 59.4 Accumulated amortization (5.5 ) (3.5 ) Net carrying amount $ 53.9 $ 55.9
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]	Amortization expense for the next five years and in total thereafter as of December 31, 2015 , is expected to be as follows (in millions): 2016 $ 2.0 2017 2.0 2018 2.0 2019 2.0 2020 1.9 Thereafter 44.0 $ 53.9

Asset Retirement Obligations 34

Asset Retirement Obligations (ARO) (Tables)	12 Months Ended
	Dec. 31, 2015
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligation [Table Text Block]	The following table summarizes the aggregate carrying amount of the Partnership’s ARO (in millions): 2015 2014 Balance at beginning of year $ 46.3 $ 47.1 Liabilities recorded 9.7 4.3 Liabilities settled (5.1 ) (6.9 ) Accretion expense 1.7 1.8 Balance at end of year 52.6 46.3 Less: Current portion of ARO (14.5 ) (6.4 ) Long-term ARO $ 38.1 $ 39.9

Regulatory Assets and Liabili35

Regulatory Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2015
Regulatory Assets and Liabilities Disclosure [Abstract]
Schedule of Regulatory Assets and Liabilities [Table Text Block]	None of the regulatory assets shown below were earning a return as of December 31, 2015 and 2014 (in millions): 2015 2014 Regulatory Assets: Pension $ 10.6 $ 10.6 Tax effect of AFUDC equity 3.1 3.5 Fuel tracker — 0.2 Total regulatory assets $ 13.7 $ 14.3 Regulatory Liabilities: Cashout and fuel tracker $ 6.0 $ 0.9 Provision for other asset retirement 57.2 60.5 Unamortized debt expense and premium on reacquired debt (1) (8.0 ) (9.6 ) Unamortized discount on long-term debt (1.2 ) (1.5 ) Postretirement benefits other than pension 39.9 34.2 Total regulatory liabilities $ 93.9 $ 84.5 (1) The 2014 balance of unamortized debt expense and premium on reacquired debt was moved to the Regulatory Liabilities section due to the implementation of ASU 2015-03. Refer to Note 2 for more information regarding the implementation of ASU 2015-03.

Financing (Tables)

Financing (Tables)	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments [Table Text Block]	The following table presents all long-term debt issues outstanding as of December 31, 2015 and 2014 (in millions): 2015 2014 Notes and Debentures: Boardwalk Pipelines 5.875% Notes due 2016 $ 250.0 $ 250.0 5.50% Notes due 2017 300.0 300.0 5.20% Notes due 2018 185.0 185.0 5.75% Notes due 2019 350.0 350.0 3.375% Notes due 2023 300.0 300.0 4.95% Notes due 2024 (Boardwalk Pipelines 2024 Notes) 600.0 350.0 Gulf South 5.05% Notes due 2015 (Gulf South 2015 Notes) — 275.0 6.30% Notes due 2017 275.0 275.0 4.00% Notes due 2022 300.0 300.0 Texas Gas 4.60% Notes due 2015 (Texas Gas 2015 Notes) — 250.0 4.50% Notes due 2021 440.0 440.0 7.25% Debentures due 2027 100.0 100.0 Total notes and debentures 3,100.0 3,375.0 Term Loan — 200.0 Revolving Credit Facility: Gulf Crossing 375.0 120.0 Capital lease obligation 9.1 9.6 3,484.1 3,704.6 Less: Unamortized debt discount (14.4 ) (14.9 ) Unamortized debt issuance costs (10.4 ) (12.5 ) Total Long-Term Debt and Capital Lease Obligation $ 3,459.3 $ 3,677.2
Schedule of Maturities of Long-term Debt [Table Text Block]	Maturities of the Partnership’s long-term debt for the next five years and in total thereafter are as follows (in millions): 2016 $ 250.0 2017 575.0 2018 185.0 2019 350.0 2020 375.0 Thereafter 1,740.0 Total long-term debt $ 3,475.0
Debt Issuances [Table Text Block]	For the years ended December 31, 2015 , 2014 and 2013 , 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 March 2015 Boardwalk Pipelines $ 250.0 $ 2.9 $ 247.1 (1) 4.95 % December 15, 2024 June 15 and December 15 November 2014 Boardwalk Pipelines $ 350.0 $ 7.1 $ 342.9 (2) 4.95 % December 15, 2024 June 15 and December 15 (1) The net proceeds of this offering were used to retire a portion of the outstanding $250.0 million aggregate principal amount of the Texas Gas 2015 Notes. Initially, the Partnership used the net proceeds to reduce outstanding borrowings under its revolving credit facility. Subsequently, on June 1, 2015, the Partnership retired the Texas Gas 2015 Notes with borrowings under its revolving credit facility. (2) The net proceeds of this offering were used to retire all of the outstanding Gulf South 2015 Notes and the remainder of the net proceeds were used to reduce outstanding borrowings under the Partnership's revolving credit facility.
Equity Issuance [Table Text Block]	For the years ended December 31, 2015 and 2013 , the Partnership completed the following issuances and sales of common units (in millions, except the issuance price): Month of Offering Number of Common Units Issuance Price Less Underwriting Discounts and Expenses Net Proceeds (including General Partner Contribution) Common Units Outstanding After Offering Common Units Held by the Public After Offering February 2015 - April 2015 7.0 $ 16.19 (1) $ 1.1 $ 115.4 250.3 (2) 124.6 May 2013 12.7 $ 30.12 $ 12.3 $ 376.5 220.3 117.6 (1) The issuance price represents the average issuance price for the common units issued under an equity distribution agreement described further below. (2) On October 9, 2013, all of the 22.9 million class B units were converted into common units on a one-for-one basis, pursuant to the terms of the partnership agreement.
Summary of Changes in Partnership Capital [Table Text Block]	The following table summarizes changes in the Partnership’s common and class B units since January 1, 2013 (in millions): Common Units Class B Units (1) Balance, January 1, 2013 207.7 22.9 Common units issued in connection with underwritten offerings 12.7 — Conversion of class B units 22.9 (22.9 ) Balance, December 31, 2013 and 2014 243.3 — Common units issued under an equity distribution agreement 7.0 — Balance, December 31, 2015 250.3 — (1) On October 9, 2013, all of the 22.9 million class B units were converted into common units on a one-for-one basis, pursuant to the terms of the partnership agreement.

Employee Benefits (Tables)

Employee Benefits (Tables)	12 Months Ended
	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Projected Benefit Obligation, Fair Value of Assets, Funded Status and the Amounts Not Yet Recognized As Components of Net Periodic Pension and Postretirement Benefits Cost [Table Text Block]	Projected Benefit Obligation, Fair Value of Assets and Funded Status The projected benefit obligation, fair value of assets, funded status and the amounts not yet recognized as components of net periodic pension and postretirement benefits cost for the Retirement Plans and PBOP at December 31, 2015 and 2014 , were as follows (in millions): Retirement Plans PBOP For the Year Ended For the Year Ended 2015 2014 2015 2014 Change in benefit obligation: Benefit obligation at beginning of period $ 149.9 $ 148.5 $ 55.1 $ 50.0 Service cost 3.8 3.9 0.3 0.4 Interest cost 4.9 5.8 2.0 2.2 Plan participants’ contributions — — 1.1 0.9 Actuarial (gain) loss (1.9 ) 3.6 (5.6 ) 5.2 Benefits paid (0.5 ) (0.5 ) (4.5 ) (3.6 ) Settlement (12.4 ) (11.4 ) — — Benefit obligation at end of period $ 143.8 $ 149.9 $ 48.4 $ 55.1 Change in plan assets: Fair value of plan assets at beginning of period $ 130.7 $ 131.4 $ 87.3 $ 80.8 Actual return on plan assets (1.3 ) 8.2 2.4 9.1 Benefits paid (0.5 ) (0.5 ) (4.5 ) (3.6 ) Settlement (12.4 ) (11.4 ) — — Company contributions 3.0 3.0 0.1 0.1 Plan participants’ contributions — — 1.1 0.9 Fair value of plan assets at end of period $ 119.5 $ 130.7 $ 86.4 $ 87.3 Funded status $ (24.3 ) $ (19.2 ) $ 38.0 $ 32.2 Items not recognized as components of net periodic cost: Prior service cost (credit) $ — $ — $ (0.9 ) $ (8.6 ) Net actuarial loss 29.9 26.0 7.2 10.7 Total $ 29.9 $ 26.0 $ 6.3 $ 2.1
Schedule of Accumulated Benefit Obligations in Excess of Fair Value of Plan Assets [Table Text Block]	At December 31, 2015 and 2014 , the following aggregate information relates only to the underfunded plans (in millions): Retirement Plans For the Year Ended 2015 2014 Projected benefit obligation $ 143.8 $ 149.9 Accumulated benefit obligation 134.1 139.7 Fair value of plan assets 119.5 130.7
Schedule of Net Benefit Costs [Table Text Block]	Components of Net Periodic Benefit Cost Components of net periodic benefit cost for both the Retirement Plans and PBOP for the years ended December 31, 2015 , 2014 and 2013 , were as follows (in millions): Retirement Plans PBOP For the Year Ended For the Year Ended 2015 2014 2013 2015 2014 2013 Service cost $ 3.8 $ 3.9 $ 3.9 $ 0.3 $ 0.4 $ 0.5 Interest cost 4.9 5.8 5.0 2.0 2.2 2.1 Expected return on plan assets (9.1 ) (9.5 ) (9.1 ) (4.6 ) (4.2 ) (4.5 ) Amortization of prior service credit — — — (7.7 ) (7.8 ) (7.8 ) Amortization of unrecognized net loss 2.0 1.4 2.1 — 0.3 — Settlement charge 2.5 1.9 1.7 — — — Net periodic benefit cost $ 4.1 $ 3.5 $ 3.6 $ (10.0 ) $ (9.1 ) $ (9.7 )
Schedule of Expected Benefit Payments [Table Text Block]	Estimated Future Benefit Payments The following table shows benefit payments, which reflect expected future service, as appropriate, which are expected to be paid for both the Retirement Plans and PBOP (in millions): Retirement Plans PBOP 2016 $ 18.9 $ 2.9 2017 13.4 3.0 2018 13.7 3.2 2019 14.8 3.2 2020 13.7 3.2 2021-2025 64.3 15.5
Weighted-Average Assumptions Used to Determine Benefit Obligations [Table Text Block]	Weighted–Average Assumptions Weighted-average assumptions used to determine benefit obligations for the years ended December 31, 2015 and 2014 , were as follows: Retirement Plans PBOP For the Year Ended For the Year Ended 2015 2014 2015 2014 Pension SRP Pension SRP Discount rate 3.60 % 4.00 % 3.35 % 3.75 % 4.25 % 3.90 % Expected return on plan assets 7.50 % 7.50 % 7.50 % 7.50 % 5.30 % 5.30 % Rate of compensation increase 3.50 % 3.50 % 3.50 % 3.50 % — % — %
Weighted-Average Assumptions Used to Determine Net Periodic Benefit Cost [Table Text Block]	Weighted-average assumptions used to determine net periodic benefit cost for the periods indicated were as follows: Retirement Plans PBOP For the Year Ended For the Year Ended 2015 2014 2013 2015 2014 2013 Pension SRP Pension SRP Pension SRP Discount rate 3.35%/ 3.60% (1) 3.75 % 4.00% 4.25 % 3.25%/ 4.10% (2) 3.50 % 3.90 % 4.50 % 3.90 % Expected return on plan assets 7.50 % 7.50 % 7.50% 7.50 % 7.50 % 7.50 % 5.30 % 5.30 % 5.30 % Rate of compensation increase 3.50 % 3.50 % 3.50% 3.50 % 3.50 % 3.50 % — % — % — % (1) Pension expense was remeasured at August 31, 2015, to reflect a settlement. (2) Pension expense was remeasured at September 30, 2013, to reflect a settlement.
Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates [Table Text Block]	PBOP Assumed Health Care Cost Trends Assumed health care cost trend rates have a significant effect on the amounts reported for PBOP. A one-percentage-point change in assumed trend rates for health care costs would have had the following effects on amounts reported for the year ended December 31, 2015 (in millions): Effect of 1% Increase: 2015 Benefit obligation at end of year $ 2.0 Total of service and interest costs for year 0.1 Effect of 1% Decrease: Benefit obligation at end of year $ (1.8 ) Total of service and interest costs for year (0.1 )
Fair Values of Pension Plan Assets By Asset Class Master Trust [Table Text Block]	The following table sets forth, by level within the fair value hierarchy, a summary of the Master Trust’s investments measured at fair value on a recurring basis at December 31, 2015 (in millions): Master Trust Assets Level 1 Level 2 Level 3 Total Equity securities $ 36.1 $ — $ — $ 36.1 Short-term investments 6.6 — — 6.6 Fixed income mutual funds 94.8 — — 94.8 Asset-backed securities — 6.4 — 6.4 Limited partnerships : Hedge funds — 49.7 31.0 80.7 Private equity — — 9.7 9.7 Total investments $ 137.5 $ 56.1 $ 40.7 $ 234.3 The following table sets forth, by level within the fair value hierarchy, a summary of the Master Trust’s investments measured at fair value on a recurring basis at December 31, 2014 (in millions): Master Trust Assets Level 1 Level 2 Level 3 Total Equity securities $ 42.3 $ — $ — $ 42.3 Short-term investments 11.8 — — 11.8 Other assets 1.1 — — 1.1 Fixed income mutual funds 98.7 — — 98.7 Asset-backed securities — 6.0 — 6.0 Limited partnerships: Hedge funds — 56.7 29.5 86.2 Private equity — — 10.1 10.1 Total investments $ 153.9 $ 62.7 $ 39.6 $ 256.2
Fair Value Measurement Using Significant Unobservable Inputs Master Trust [Table Text Block]	The following table presents a reconciliation of the beginning and ending balances of the fair value measurements using significant unobservable inputs (Level 3) for the Master Trust (in millions): Limited Partnerships: Hedge Funds Limited Partnerships: Private Equity Balance January 1, 2014 $ 29.7 $ 11.7 Actual return on assets still held 2.1 0.2 Actual return on assets sold 0.1 0.8 Purchases, sales and settlements (2.4 ) (2.6 ) Balance December 31, 2014 29.5 10.1 Actual return on assets still held 1.0 0.6 Actual return on assets sold 0.2 0.1 Purchases, sales and settlements (0.3 ) (1.1 ) Net transfers into Level 3 0.6 — Balance December 31, 2015 $ 31.0 $ 9.7
Fair Values of Pension Plan Assets By Asset Class [Table Text Block]	The following table sets forth, by level within the fair value hierarchy, a summary of the PBOP trust investments measured at fair value on a recurring basis at December 31, 2015 (in millions): PBOP Trust Assets Level 1 Level 2 Level 3 Total Short-term investments $ 3.0 $ — $ — $ 3.0 Fixed income mutual funds 4.7 — — 4.7 Asset-backed securities — 18.8 — 18.8 Corporate bonds — 17.0 — 17.0 Tax exempt securities — 42.9 — 42.9 Total investments $ 7.7 $ 78.7 $ — $ 86.4 The following table sets forth, by level within the fair value hierarchy, a summary of the PBOP trust investments measured at fair value on a recurring basis at December 31, 2014 (in millions): PBOP Trust Assets Level 1 Level 2 Level 3 Total Short-term investments $ 3.2 $ — $ — $ 3.2 Fixed income mutual funds 3.0 — — 3.0 Asset-backed securities — 20.4 — 20.4 Corporate bonds — 17.8 — 17.8 Tax exempt securities — 42.9 — 42.9 Total investments $ 6.2 $ 81.1 $ — $ 87.3
Disclosure of Share Based Compensation Arrangements by Share Based Payment Award LTIP [Table Text Block]	A summary of the status of the Phantom Common Units granted under the Partnership’s LTIP as of December 31, 2015 and 2014 , and changes during the years ended December 31, 2015 and 2014 , is presented below: Phantom Common Units Total Fair Value (in millions) Weighted-Average Vesting Period (in years) Outstanding at January 1, 2014 (1) 380,048 $ 10.9 1.5 Paid (171,411 ) (3.5 ) — Forfeited (8,968 ) — — Outstanding at December 31, 2014 (1) 199,669 4.1 0.9 Granted 647,256 10.1 2.4 Paid (196,748 ) (2.9 ) — Forfeited (4,209 ) — — Outstanding at December 31, 2015 (1) 645,968 $ 8.7 1.5 (1) Represents fair value and remaining weighted-average vesting period of outstanding awards at the end of the period.

Cash Distributions and Net In38

Cash Distributions and Net Income per Unit (Tables)	12 Months Ended
	Dec. 31, 2015
Partners' Capital Notes [Abstract]
Schedule of partnership quarterly distribution allocation [Table Text Block]	IDRs, which represent a limited partner ownership interest and are currently held by the Partnership’s general partner, represent the contractual right to receive an increasing percentage of quarterly distributions of available cash as follows: Total Quarterly Distributions Marginal Percentage Interest in Distributions Target Amount Limited Partner Unitholders General Partner and IDRs First Target Distribution up to $0.4025 98% 2% Second Target Distribution above $0.4025 up to $0.4375 85% 15% Third Target Distribution above $0.4375 up to $0.5250 75% 25% Thereafter above $0.5250 50% 50%
Dividends Declared [Table Text Block]	The Partnership has declared quarterly distributions per unit to unitholders of record, including holders of common and class B units (through October 9, 2013), and the 2% general partner interest and IDRs held by its general partner as follows (in millions, except distribution per unit): Payment Date Distribution per Unit Amount Paid to Common Unitholders Amount Paid to Class B Unitholder Amount Paid to General Partner (Including IDRs) (1) November 19, 2015 $ 0.1000 $ 25.0 $ — $ 0.5 August 20, 2015 0.1000 25.1 — 0.5 May 21, 2015 0.1000 25.1 — 0.5 February 26, 2015 0.1000 24.3 — 0.5 November 20, 2014 0.1000 24.3 — 0.5 August 21, 2014 0.1000 24.3 — 0.5 May 15, 2014 0.1000 24.3 — 0.5 February 27, 2014 0.1000 24.3 — 0.5 November 14, 2013 0.5325 129.5 — (2) 12.4 August 15, 2013 0.5325 117.3 6.9 11.4 May 16, 2013 0.5325 110.6 6.8 10.7 February 28, 2013 0.5325 110.6 6.9 10.8 (1) In February 2014, the Partnership decreased its distribution rate to $0.10 per common unit. As a result of the reduced distribution rate, the quarterly target distribution levels for IDR payout were not met and the Partnership paid no amounts with respect to the IDRs in 2015 and 2014 . In 2013 , the Partnership paid $34.6 million in distributions on behalf of IDRs. (2) On October 9, 2013, all of the 22.9 million Class B units were converted into common units on a one-for-one basis, pursuant to the terms of the partnership agreement.
Distributions Made to Limited Partner, by Distribution [Table Text Block]	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 year ended December 31, 2015 (in millions, except per unit data): Total Common Units General Partner and IDRs Net income $ 222.0 Less: Net loss attributable to noncontrolling interests — Net income attributable to controlling interests 222.0 Declared distribution 102.2 $ 100.2 $ 2.0 Assumed allocation of undistributed net income 119.8 117.3 2.5 Assumed allocation of net income attributable to limited partner unitholders and general partner $ 222.0 $ 217.5 $ 4.5 Weighted-average units outstanding 248.8 Net income per unit $ 0.87 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 year ended December 31, 2014 (in millions, except per unit data): Total Common Units General Partner and IDRs Net income $ 146.8 Less: Net loss attributable to noncontrolling interests (86.8 ) Net income attributable to controlling interests 233.6 Declared distribution 99.2 $ 97.2 $ 2.0 Assumed allocation of undistributed net income 134.4 131.7 2.7 Assumed allocation of net income attributable to limited partner unitholders and general partner $ 233.6 $ 228.9 $ 4.7 Weighted-average units outstanding 243.3 Net income per unit $ 0.94 The following table provides a reconciliation of net income and the assumed allocation of net income to the common and class B units for purposes of computing net income per unit for the year ended December 31, 2013 . Basic net income per unit is calculated based on the weighted-average number of units outstanding for the period. Diluted net income per unit is calculated assuming that the class B units converted on the date that they became convertible, or July 1, 2013 (in millions, except per unit data): Total Common Units Class B Units General Partner and IDRs Net income $ 250.2 Less: Net loss attributable to noncontrolling interests (3.5 ) Net income attributable to controlling interests 253.7 Declared distribution 430.5 $ 381.8 $ 13.7 $ 35.0 Assumed allocation of undistributed net loss (basic) (176.8 ) (160.5 ) (12.8 ) (3.5 ) Assumed allocation of net income attributable to limited partner unitholders and general partner — basic 253.7 221.3 0.9 31.5 Allocation for diluted earnings per unit — (4.6 ) 4.6 — Assumed allocation of net income attributable to limited $ 253.7 $ 216.7 $ 5.5 $ 31.5 Weighted-average units outstanding — basic 220.5 17.6 Weighted-average units outstanding — diluted 226.8 11.3 Net income per unit — basic $ 1.00 $ 0.05 Net income per unit — diluted $ 0.96 $ 0.48

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]	Following is a summary of the provision for income taxes for the periods ended December 31, 2015 , 2014 and 2013 (in millions): For the Year Ended December 31, 2015 2014 2013 Current expense: State $ 0.4 $ 0.3 $ 0.4 Total 0.4 0.3 0.4 Deferred provision: State 0.1 0.1 0.1 Total 0.1 0.1 0.1 Income taxes $ 0.5 $ 0.4 $ 0.5

Supplemental Disclosure of Ca40

Supplemental Disclosure of Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2015
Supplemental Cash Flow Elements [Abstract]
Schedule of Cash Flow, Supplemental Disclosures [Table Text Block]	Supplemental Disclosure of Cash Flow Information (in millions): For the Year Ended December 31, 2015 2014 2013 Cash paid during the period for: Interest (net of amount capitalized) $ 170.6 $ 153.0 $ 151.0 Income taxes, net 0.3 0.1 0.3 Non-cash adjustments: Accounts payable and PPE 54.7 36.9 38.1 Capital lease obligations incurred — — 10.5

Selected Quarterly Financial 41

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Data [Abstract]
Schedule of Quarterly Financial Information [Table Text Block]	The following tables summarize selected quarterly financial data for 2015 and 2014 for the Partnership (in millions, except for earnings per unit): 2015 For the Quarter Ended: December 31 September 30 June 30 March 31 Operating revenues $ 326.8 $ 294.1 $ 298.6 $ 329.7 Operating expenses 220.4 213.4 212.7 206.9 Operating income 106.4 80.7 85.9 122.8 Interest expense, net 42.1 43.0 45.8 45.1 Other income (1.4 ) (0.7 ) (0.4 ) (0.2 ) Income before income taxes 65.7 38.4 40.5 77.9 Income taxes 0.1 0.1 0.1 0.2 Net income 65.6 38.3 40.4 77.7 Net earnings (loss) attributable to noncontrolling interests — — — — Net income attributable to controlling interests $ 65.6 $ 38.3 $ 40.4 $ 77.7 Net income per unit: $ 0.26 $ 0.15 $ 0.16 $ 0.31 2014 For the Quarter Ended: December 31 September 30 June 30 March 31 Operating revenues $ 304.6 $ 278.9 $ 293.4 $ 356.9 Operating expenses 224.1 210.4 196.9 204.3 Operating income 80.5 68.5 96.5 152.6 Interest expense, net 44.2 39.9 40.0 40.8 Other (income) expense (0.6 ) 0.1 0.5 86.0 Income before income taxes 36.9 28.5 56.0 25.8 Income taxes — 0.1 0.1 0.2 Net income 36.9 28.4 55.9 25.6 Net earnings (loss) attributable to 0.1 (0.8 ) (1.5 ) (84.6 ) Net income attributable to $ 36.8 $ 29.2 $ 57.4 $ 110.2 Net income per unit: $ 0.15 $ 0.12 $ 0.23 $ 0.44

Guarantee of Securities of Su42

Guarantee of Securities of Subsidiaries (Tables)	12 Months Ended
	Dec. 31, 2015
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed Consolidated Balance Sheet [Table Text Block]	Condensed Consolidating Balance Sheets as of December 31, 2015 (Millions) Assets Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Cash and cash equivalents $ — $ 0.3 $ 2.8 $ — $ 3.1 Receivables — — 129.5 — 129.5 Receivables - affiliate — — 7.0 (7.0 ) — Gas and liquids stored underground — — 10.7 — 10.7 Prepayments 0.2 — 16.7 — 16.9 Advances to affiliates — 21.0 107.7 (128.7 ) — Other current assets — — 12.8 (3.2 ) 9.6 Total current assets 0.2 21.3 287.2 (138.9 ) 169.8 Investment in consolidated subsidiaries 2,153.5 7,067.6 — (9,221.1 ) — Property, plant and equipment, gross 0.6 — 9,706.0 — 9,706.6 Less–accumulated depreciation and amortization 0.6 — 2,051.6 — 2,052.2 Property, plant and equipment, net — — 7,654.4 — 7,654.4 Other noncurrent assets 0.4 3.0 472.7 — 476.1 Advances to affiliates – noncurrent 2,190.2 466.3 1,113.4 (3,769.9 ) — Total other assets 2,190.6 469.3 1,586.1 (3,769.9 ) 476.1 Total Assets $ 4,344.3 $ 7,558.2 $ 9,527.7 $ (13,129.9 ) $ 8,300.3 Liabilities and Partners' Capital Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Payables $ 0.3 $ 0.1 $ 118.2 $ — $ 118.6 Payable to affiliates 1.3 — 7.0 (7.0 ) 1.3 Advances from affiliates — 107.7 21.0 (128.7 ) — Other current liabilities — 20.9 176.8 (3.2 ) 194.5 Total current liabilities 1.6 128.7 323.0 (138.9 ) 314.4 Long-term debt and capital lease obligation — 1,972.4 1,486.9 — 3,459.3 Payable to affiliate - noncurrent 16.0 — — — 16.0 Advances from affiliates - noncurrent — 3,303.6 466.3 (3,769.9 ) — Other noncurrent liabilities — — 183.9 — 183.9 Total other liabilities and deferred credits 16.0 3,303.6 650.2 (3,769.9 ) 199.9 Total partners’ capital 4,326.7 2,153.5 7,067.6 (9,221.1 ) 4,326.7 Total Liabilities and Partners' Capital $ 4,344.3 $ 7,558.2 $ 9,527.7 $ (13,129.9 ) $ 8,300.3 Condensed Consolidating Balance Sheets as of December 31, 2014 (Millions) Assets Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Cash and cash equivalents $ 0.5 $ 1.8 $ 4.3 $ — $ 6.6 Receivables — — 110.9 — 110.9 Receivables - affiliate — — 9.0 (9.0 ) — Gas and liquids stored underground — — 4.1 — 4.1 Prepayments 0.1 — 14.4 — 14.5 Advances to affiliates — 6.3 106.2 (112.5 ) — Other current assets 0.5 — 19.2 (6.2 ) 13.5 Total current assets 1.1 8.1 268.1 (127.7 ) 149.6 Investment in consolidated subsidiaries 1,970.6 6,744.1 — (8,714.7 ) — Property, plant and equipment, gross 0.6 — 9,355.0 — 9,355.6 Less–accumulated depreciation and amortization 0.6 — 1,765.8 — 1,766.4 Property, plant and equipment, net — — 7,589.2 — 7,589.2 Other noncurrent assets — 1.7 454.4 (0.6 ) 455.5 Advances to affiliates – noncurrent 2,148.3 212.0 996.5 (3,356.8 ) — Total other assets 2,148.3 213.7 1,450.9 (3,357.4 ) 455.5 Total Assets $ 4,120.0 $ 6,965.9 $ 9,308.2 $ (12,199.8 ) $ 8,194.3 Liabilities and Partners' Capital Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Payables $ 0.2 $ 0.1 $ 61.8 $ — $ 62.1 Payable to affiliates 1.5 — 9.0 (9.0 ) 1.5 Advances from affiliates — 106.2 6.3 (112.5 ) — Other current liabilities — 21.4 141.7 (6.5 ) 156.6 Total current liabilities 1.7 127.7 218.8 (128.0 ) 220.2 Long-term debt and capital lease obligation — 1,722.8 1,954.4 — 3,677.2 Payable to affiliate - noncurrent 16.0 — — — 16.0 Advances from affiliates - noncurrent — 3,144.8 212.0 (3,356.8 ) — Other noncurrent liabilities — — 178.9 (0.3 ) 178.6 Total other liabilities and deferred credits 16.0 3,144.8 390.9 (3,357.1 ) 194.6 Total partners’ capital 4,102.3 1,970.6 6,744.1 (8,714.7 ) 4,102.3 Total Liabilities and Partners' Capital $ 4,120.0 $ 6,965.9 $ 9,308.2 $ (12,199.8 ) $ 8,194.3
Condensed Consolidating Statements of Income [Table Text Block]	Condensed Consolidating Statements of Income for the Year Ended December 31, 2015 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Operating Revenues: Transportation $ — $ — $ 1,178.5 $ (87.4 ) $ 1,091.1 Parking and lending — — 11.6 (0.2 ) 11.4 Storage — — 81.3 — 81.3 Other — — 65.4 — 65.4 Total operating revenues — — 1,336.8 (87.6 ) 1,249.2 Operating Costs and Expenses: Fuel and transportation — — 186.9 (87.6 ) 99.3 Operation and maintenance — — 209.5 — 209.5 Administrative and general — — 130.4 — 130.4 Other operating costs and expenses 0.3 — 413.9 — 414.2 Total operating costs and expenses 0.3 — 940.7 (87.6 ) 853.4 Operating (loss) income (0.3 ) — 396.1 — 395.8 Other Deductions (Income): Interest expense — 104.0 72.4 — 176.4 Interest (income) expense-affiliates, net (28.8 ) 38.2 (9.4 ) — — Interest income — — (0.4 ) — (0.4 ) Equity in earnings of subsidiaries (193.5 ) (335.7 ) — 529.2 — Miscellaneous other income, net — — (2.7 ) — (2.7 ) Total other (income) deductions (222.3 ) (193.5 ) 59.9 529.2 173.3 Income (loss) before income taxes 222.0 193.5 336.2 (529.2 ) 222.5 Income taxes — — 0.5 — 0.5 Net income (loss) $ 222.0 $ 193.5 $ 335.7 $ (529.2 ) $ 222.0 Condensed Consolidating Statements of Income for the Year Ended December 31, 2014 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Operating Revenues: Transportation $ — $ — $ 1,157.9 $ (92.8 ) $ 1,065.1 Parking and lending — — 23.3 — 23.3 Storage — — 90.4 (0.9 ) 89.5 Other — — 55.9 — 55.9 Total operating revenues — — 1,327.5 (93.7 ) 1,233.8 Operating Costs and Expenses: Fuel and transportation — — 218.4 (93.7 ) 124.7 Operation and maintenance — — 194.8 — 194.8 Administrative and general 0.2 — 124.8 — 125.0 Other operating costs and expenses 0.2 — 391.0 — 391.2 Total operating costs and expenses 0.4 — 929.0 (93.7 ) 835.7 Operating (loss) income (0.4 ) — 398.5 — 398.1 Other Deductions (Income): Interest expense — 76.5 89.0 — 165.5 Interest (income) expense - affiliates, net (30.0 ) 41.2 (11.2 ) — — Interest income — — (0.6 ) — (0.6 ) Equity in earnings of subsidiaries (204.0 ) (321.7 ) — 525.7 — Equity losses in unconsolidated affiliates — — 86.5 — 86.5 Miscellaneous other income, net — — (0.5 ) — (0.5 ) Total other (income) deductions (234.0 ) (204.0 ) 163.2 525.7 250.9 Income (loss) before income taxes 233.6 204.0 235.3 (525.7 ) 147.2 Income taxes — — 0.4 — 0.4 Net income (loss) 233.6 204.0 234.9 (525.7 ) 146.8 Net loss attributable to noncontrolling interests — — (86.8 ) — (86.8 ) Net income (loss) attributable to controlling $ 233.6 $ 204.0 $ 321.7 $ (525.7 ) $ 233.6 Condensed Consolidating Statements of Income for the Year Ended December 31, 2013 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Operating Revenues: Transportation $ — $ — $ 1,116.4 $ (88.4 ) $ 1,028.0 Parking and lending — — 24.0 (0.1 ) 23.9 Storage — — 111.0 (0.1 ) 110.9 Other — — 42.8 — 42.8 Total operating revenues — — 1,294.2 (88.6 ) 1,205.6 Operating Costs and Expenses: Fuel and transportation — — 185.8 (88.6 ) 97.2 Operation and maintenance — 0.3 182.4 — 182.7 Administrative and general (0.1 ) 0.8 116.7 — 117.4 Other operating costs and expenses 0.3 0.1 393.4 — 393.8 Total operating costs and expenses 0.2 1.2 878.3 (88.6 ) 791.1 Operating (loss) income (0.2 ) (1.2 ) 415.9 — 414.5 Other Deductions (Income): Interest expense — 72.7 90.7 — 163.4 Interest (income) expense - affiliates, net (33.6 ) 41.3 (7.7 ) — — Interest income — — (0.5 ) — (0.5 ) Equity in earnings of subsidiaries (220.3 ) (335.5 ) — 555.8 — Equity losses in unconsolidated affiliates — — 1.2 — 1.2 Miscellaneous other income, net — — (0.3 ) — (0.3 ) Total other (income) deductions (253.9 ) (221.5 ) 83.4 555.8 163.8 Income (loss) before income taxes 253.7 220.3 332.5 (555.8 ) 250.7 Income taxes — — 0.5 — 0.5 Net income (loss) 253.7 220.3 332.0 (555.8 ) 250.2 Net loss attributable to noncontrolling interests — — (3.5 ) — (3.5 ) Net income (loss) attributable to controlling $ 253.7 $ 220.3 $ 335.5 $ (555.8 ) $ 253.7
Condensed Consolidating Statements of Comprehensive Income [Table Text Block]	Condensed Consolidating Statements of Comprehensive Income for the Year Ended December 31, 2015 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net income (loss) $ 222.0 $ 193.5 $ 335.7 $ (529.2 ) $ 222.0 Other comprehensive income (loss): Reclassification adjustment transferred to Net income from cash flow hedges 2.4 2.4 0.7 (3.1 ) 2.4 Pension and other postretirement benefit costs (13.9 ) (13.9 ) (13.9 ) 27.8 (13.9 ) Total Comprehensive Income (Loss) 210.5 182.0 322.5 (504.5 ) 210.5 Comprehensive loss attributable to noncontrolling interests — — — — — Comprehensive income (loss) attributable to controlling interests $ 210.5 $ 182.0 $ 322.5 $ (504.5 ) $ 210.5 Condensed Consolidating Statements of Comprehensive Income for the Year Ended December 31, 2014 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net income (loss) $ 233.6 $ 204.0 $ 234.9 $ (525.7 ) $ 146.8 Other comprehensive (loss) income: (Loss) gain on cash flow hedges (0.7 ) (0.7 ) (0.7 ) 1.4 (0.7 ) Reclassification adjustment transferred to Net income from cash flow hedges 2.6 2.6 0.9 (3.5 ) 2.6 Pension and other postretirement benefit costs (10.9 ) (10.9 ) (10.9 ) 21.8 (10.9 ) Total Comprehensive Income (Loss) 224.6 195.0 224.2 (506.0 ) 137.8 Comprehensive loss attributable to noncontrolling interests — — (86.8 ) — (86.8 ) Comprehensive income (loss) attributable to controlling interests $ 224.6 $ 195.0 $ 311.0 $ (506.0 ) $ 224.6 Condensed Consolidating Statements of Comprehensive Income for the Year Ended December 31, 2013 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net income (loss) $ 253.7 $ 220.3 $ 332.0 $ (555.8 ) $ 250.2 Other comprehensive income (loss): Gain (loss) on cash flow hedges 1.6 1.6 1.6 (3.2 ) 1.6 Reclassification adjustment transferred to Net Income from cash flow hedges 1.2 1.2 (0.5 ) (0.7 ) 1.2 Pension and other postretirement benefit costs 0.7 0.7 0.7 (1.4 ) 0.7 Total Comprehensive Income (Loss) 257.2 223.8 333.8 (561.1 ) 253.7 Comprehensive loss attributable to noncontrolling interests — — (3.5 ) — (3.5 ) Comprehensive income (loss) attributable to controlling interests $ 257.2 $ 223.8 $ 337.3 $ (561.1 ) $ 257.2
Condensed Consolidating Statements of Cash Flows [Table Text Block]	Condensed Consolidating Statements of Cash Flow for the Year Ended December 31, 2015 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net cash provided by (used in) operating activities $ 27.9 $ (136.3 ) $ 684.8 $ — $ 576.4 INVESTING ACTIVITIES: Capital expenditures (1.0 ) — (373.5 ) — (374.5 ) Proceeds from sale of operating assets — — 0.8 — 0.8 Proceeds from other recoveries — — 6.2 — 6.2 Advances to affiliates, net (41.9 ) (269.0 ) (118.4 ) 429.3 — Net cash (used in) provided by investing activities (42.9 ) (269.0 ) (484.9 ) 429.3 (367.5 ) FINANCING ACTIVITIES: Proceeds from long-term debt, net of — 247.1 — — 247.1 Repayment of borrowings from long-term — — (725.0 ) — (725.0 ) Proceeds from borrowings on revolving credit agreement — — 1,125.0 — 1,125.0 Repayment of borrowings on revolving credit agreement, including financing fees — (3.6 ) (870.0 ) — (873.6 ) Principal payment of capital lease obligation — — (0.4 ) — (0.4 ) Advances from affiliates, net 0.6 160.3 269.0 (429.3 ) 0.6 Distributions paid (101.5 ) — — — (101.5 ) Proceeds from sale of common units 113.1 — — — 113.1 Capital contributions from general partner 2.3 — — — 2.3 Net cash provided by (used in) financing activities 14.5 403.8 (201.4 ) (429.3 ) (212.4 ) Decrease in cash and cash equivalents (0.5 ) (1.5 ) (1.5 ) — (3.5 ) Cash and cash equivalents at beginning of period 0.5 1.8 4.3 — 6.6 Cash and cash equivalents at end of period $ — $ 0.3 $ 2.8 $ — $ 3.1 Condensed Consolidating Statements of Cash Flow for the Year Ended December 31, 2014 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net cash provided by (used in) operating activities $ 30.2 $ (112.1 ) $ 595.5 $ — $ 513.6 INVESTING ACTIVITIES: Capital expenditures — — (404.4 ) — (404.4 ) Proceeds from sale of operating assets — — 2.9 — 2.9 Proceeds from insurance and other recoveries — — 6.3 — 6.3 Advances to affiliates, net 363.9 (49.6 ) (175.2 ) (139.0 ) 0.1 Investment in unconsolidated affiliates — — (20.5 ) — (20.5 ) Distributions from unconsolidated affiliates — — 11.1 — 11.1 Acquisition of businesses, net of cash acquired (294.7 ) — — — (294.7 ) Net cash provided by (used in) investing activities 69.2 (49.6 ) (579.8 ) (139.0 ) (699.2 ) FINANCING ACTIVITIES: Proceeds from long-term debt, net of issuance cost — 342.9 — — 342.9 Repayment of borrowings from term loan — — (25.0 ) — (25.0 ) Proceeds from borrowings on revolving credit agreement — — 665.0 — 665.0 Repayment of borrowings on revolving credit agreement — — (720.0 ) — (720.0 ) Principal payment of capital lease obligation — — (0.4 ) — (0.4 ) Advances from affiliates, net 0.1 (188.6 ) 49.6 139.0 0.1 Distributions paid (99.2 ) — — — (99.2 ) Capital contributions from noncontrolling interests — — 8.2 — 8.2 Distributions paid to noncontrolling interests — — (7.9 ) — (7.9 ) Net cash (used in) provided by financing activities (99.1 ) 154.3 (30.5 ) 139.0 163.7 Increase (decrease) in cash and cash equivalents 0.3 (7.4 ) (14.8 ) — (21.9 ) Cash and cash equivalents at beginning of period 0.2 9.2 19.1 — 28.5 Cash and cash equivalents at end of period $ 0.5 $ 1.8 $ 4.3 $ — $ 6.6 Condensed Consolidating Statements of Cash Flow for the Year Ended December 31, 2013 (Millions) Parent Guarantor Subsidiary Issuer Non-guarantor Subsidiaries Eliminations Consolidated Boardwalk Pipeline Partners, LP Net cash provided by (used in) operating activities $ 33.9 $ (108.8 ) $ 609.2 $ — $ 534.3 INVESTING ACTIVITIES: Capital expenditures — — (294.8 ) — (294.8 ) Proceeds from sale of operating assets — — 60.7 — 60.7 Proceeds from insurance and other recoveries — — 1.4 — 1.4 Advances to affiliates, net 126.4 (84.3 ) (342.8 ) 300.7 — Investment in consolidated affiliates — (15.1 ) — 15.1 — Investment in unconsolidated affiliates — — (76.7 ) — (76.7 ) Net cash provided by (used in) investing activities 126.4 (99.4 ) (652.2 ) 315.8 (309.4 ) FINANCING ACTIVITIES: Proceeds from borrowings on revolving credit agreement — — 1,128.0 — 1,128.0 Repayment of borrowings on revolving credit agreement — — (1,255.0 ) — (1,255.0 ) Contribution from parent — — 15.1 (15.1 ) — Principal payment of capital lease obligation — — (0.2 ) — (0.2 ) Advances from affiliates, net (2.8 ) 216.4 84.3 (300.7 ) (2.8 ) Distributions paid (533.9 ) — — — (533.9 ) Capital contributions from noncontrolling interests — — 87.1 — 87.1 Proceeds from sale of common units 368.7 — — — 368.7 Capital contributions from general partner 7.8 — — — 7.8 Net cash (used in) provided by financing activities (160.2 ) 216.4 59.3 (315.8 ) (200.3 ) Increase in cash and cash equivalents 0.1 8.2 16.3 — 24.6 Cash and cash equivalents at beginning of period 0.1 1.0 2.8 — 3.9 Cash and cash equivalents at end of period $ 0.2 $ 9.2 $ 19.1 $ — $ 28.5

Corporate Structure (Details)

Corporate Structure (Details) - shares shares in Millions	Feb. 19, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Percent of General Partner Interest Owned by Holding Company (in hundredths)		2.00%	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%

Accounting Policies (Details)

Accounting Policies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)segments	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	$ 0	$ 0
Number of Reportable Segments (in ones) | segments	1
Restricted Cash and Cash Equivalents	$ 0	0
Materials And Supplies Held In Other Assets	22.2	15.3
Capitalized interest and allowance for borrowed funds used during construction	3.4	6.8	$ 6.4
Allowance for equity funds used during construction	2.7	0.5	0.2
Deferred Revenue	10	7.2
Retained fuel included in Transportation	$ 53.2	90.3	76.9
Contractual Retainage Provision (Percentage)	0.50%
Customer Refund Liability, Current	$ 16.3	0
Adjustments for New Accounting Principle, Early Adoption [Member] | Other assets
Debt Issuance Cost		12.5
Adjustments for New Accounting Principle, Early Adoption [Member] | Long-Term Debt and Capital Lease Obligation
Debt Issuance Cost	$ 10.4	12.5
Cost of Domestic Regulated Gas Revenue
Prior Period Reclassification Adjustment		(4)	(3.8)
Operation and Maintenance Expenses
Prior Period Reclassification Adjustment		$ 4	$ 3.8

Basis of Presentation and Accou

Basis of Presentation and Accounting Policies Property, Plant and Equipment (PPE) and Repair and Maintenance Costs (Details)	12 Months Ended
	Dec. 31, 2015
Minimum [Member]
Property, Plant and Equipment [Line Items]
Depreciation range for PPE related to operations for which regulatory accounting does not apply (in years)	3 years
Depreciation range for PPE related to operations for which regulatory accounting is applicable (in years)	5 years
Maximum [Member]
Property, Plant and Equipment [Line Items]
Depreciation range for PPE related to operations for which regulatory accounting does not apply (in years)	35 years
Depreciation range for PPE related to operations for which regulatory accounting is applicable (in years)	62 years

Investments (Details)

Investments (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Variable Interest Entity [Line Items]
Income (Loss) from Equity Method Investments		$ 0	$ (86.5)	$ (1.2)
Boardwalk Bluegrass and Boardwalk Moss Lake, Bluegrass Pipeline, Moss Lake Fractionation and Moss Lake LPG [Member] | Boardwalk Pipeline Partners, LP
Variable Interest Entity [Line Items]
Total Project Related Impairment	$ 92.9
Income (Loss) from Impairment Attributable to Noncontrolling Interest	(82.9)
Income (Loss) from Equity Method Investments	$ (10)

Investments and Acquisitions Ac

Investments and Acquisitions Acquisition of Boardwalk Petrochemical (Details) - Boardwalk Petrochemical/Evangeline [Member] $ in Millions	Oct. 08, 2014USD ($)
Business Acquisition [Line Items]
Business Acquisition, Date of Acquisition Agreement	Oct. 8, 2014
Business Acquisition, Cost of Acquired Entity, Cash	$ 294.7

Commitments and Contingencies L

Commitments and Contingencies Legal Proceedings and Settlements (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)defendant	Dec. 31, 2014USD ($)
Regulatory Matters [Abstract]
Capacity Reduction by April 1, 2016 (up to) (in hundredths)	6.00%
Additional Capacity Reduction by April 1, 2020 (up to) (in hundredths)	6.00%
Customer Refund Liability, Current	$ 16.3	$ 0
Rate Case Incremental Revenues	20.4
Insurance Proceeds [Abstract]
Gain on Business Interruption Insurance Recovery	8.8	$ 1.2
Insurance Settlements Receivable	$ 0
Southeast Louisiana Flood Protection Litigation
Loss Contingencies [Line Items]
Loss Contingency, Number of Defendants (in ones) | defendant	100

Commitments and Contingencies49

Commitments and Contingencies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)facilities	Dec. 31, 2014USD ($)
Environmental and Safety Matters [Abstract]
Accrual for Environmental Loss Contingencies	$ 5.6	$ 6.1
Number of years the related expenditures are expected to cover assessment and remediation costs (in years)	7 years
Accrued Environmental Loss Contingencies, Current	$ 1.7	1.5
Accrued Environmental Loss Contingencies, Noncurrent	$ 3.9	$ 4.6
Number of facilities operated affected by non-attainment requirements | facilities	2
Commitments for Construction [Abstract]
Purchase Commitment, Remaining Minimum Amount Committed	$ 185.9

Commitments and Contingencies S

Commitments and Contingencies Schedule of Operating Leased Assets (Details) - Office Space and Equipment Rentals [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Leased Assets [Line Items]
Operating Leases, Rent Expense	$ 12.2	$ 10.7	$ 8.6
2,016	4.6
2,017	4.2
2,018	3.7
2,019	3.2
2,020	3.1
Thereafter	11.5
Total	$ 30.3

Commitments and Contingencies51

Commitments and Contingencies Schedule of Pipeline Capacity Agreements (Details) - Pipeline Capacity Agreements [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Recorded Unconditional Purchase Obligation [Line Items]
Expenses related to pipeline capacity agreements	$ 6.9	$ 10.1	$ 9.8
2,016	6.4
2,017	6.2
2,018	2
2,019	0
2,020	0
Thereafter	0
Total	$ 14.6

Commitments and Contingencies52

Commitments and Contingencies Schedule of Capital Leased Assets (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Capital Leased Assets [Line Items]
Capital Lease Obligations Incurred		$ 0	$ 0	$ 10.5
Long-term obligations under capital lease		$ 9.1	9.6
Office Building [Member]
Capital Leased Assets [Line Items]
Description of Lessee Leasing Arrangements, Capital Leases		The office building lease has a term of fifteen years with two twenty year renewal options.
Capital Lease Obligations Incurred	$ 10.5
2,016		$ 1
2,017		1
2,018		1
2,019		1.1
2,020		1.1
Thereafter		8.5
Total minimum lease payments		13.7
Less amounts representing interest		(4.1)
Present value of obligation under capital lease		9.6
Less: current portion of obligations under capital lease (recorded in Other current liabilities)		(0.5)
Long-term obligations under capital lease		9.1
Capital Leases, Income Statement, Amortization Expense		0.7	0.7
Capital Leased Assets, Gross		10.5	10.5
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Amortization		$ 1.7	$ 1

Other Comprehensive Income (O53

Other Comprehensive Income (OCI) and Fair Value Measurements Other Comprehensive Income (OCI) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months		$ 3.9
Accumulated other comprehensive income (loss) (beginning)		(72.8)	$ (63.8)	$ (67.3)
Gain (loss) recorded in accumulated other comprehensive income		0	(0.7)	1.6
Transportation operating revenues		(1,091.1)	(1,065.1)	(1,028)
Interest expense (1)		176.4	165.5	163.4
Pension and other postretirement benefit costs		(13.9)	(10.9)	0.7
Accumulated other comprehensive income (loss) (ending)		(84.3)	(72.8)	(63.8)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Transportation operating revenues				0.1
Other operating revenues			0.2	(0.1)
Disposal of operating assets				(1.2)
Interest expense (1)	[1]	2.4	2.4	2.4
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months		1.5
Accumulated other comprehensive income (loss) (beginning)		(62)	(51.1)	(51.8)
Gain (loss) recorded in accumulated other comprehensive income			0	0
Pension and other postretirement benefit costs		(13.9)	(10.9)	0.7
Accumulated other comprehensive income (loss) (ending)		(75.9)	(62)	(51.1)
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Transportation operating revenues				0
Other operating revenues			0	0
Disposal of operating assets				0
Interest expense (1)	[1]	0	0	0
Net gain on disposal of operating assets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months		2.4
Accumulated other comprehensive income (loss) (beginning)		(10.8)	(12.7)	(15.5)
Gain (loss) recorded in accumulated other comprehensive income			(0.7)	1.6
Pension and other postretirement benefit costs		0	0	0
Accumulated other comprehensive income (loss) (ending)		(8.4)	(10.8)	(12.7)
Net gain on disposal of operating assets | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Transportation operating revenues				0.1
Other operating revenues			0.2	(0.1)
Disposal of operating assets				(1.2)
Interest expense (1)	[1]	$ 2.4	$ 2.4	$ 2.4
[1]	Related to amounts deferred in AOCI from the treasury rate locks described above.

Other Comprehensive Income (O54

Other Comprehensive Income (OCI) and Fair Value Measurements Financial Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	$ 0		$ 0
Liabilities, Fair Value Disclosure, Recurring	0		0
Cash and cash equivalents	3.1		6.6		$ 28.5	$ 3.9
Capital Lease Obligations, Noncurrent	9.1		9.6
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and Cash Equivalents, Fair Value	3.1		6.6
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term Debt, Fair Value	3,299.7		3,787.4
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	3.1		6.6
Long-term debt	3,460.6	[1]	3,680.1	[2]
Fair Value | Fair Value, Inputs, Level 1
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and Cash Equivalents, Fair Value	3.1		6.6
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term Debt, Fair Value	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]
Long-term Debt, Fair Value	3,299.7		3,787.4
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]
Long-term Debt, Fair Value	0		0
Long-Term Debt and Capital Lease Obligation | Adjustments for New Accounting Principle, Early Adoption [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unamortized Debt Issuance Costs	$ 10.4		$ 12.5
[1]	The carrying amount of long-term debt excludes a $9.1 million long-term capital lease obligation and $10.4 million of unamortized debt issuance costs.
[2]	The carrying amount of long-term debt excludes a $9.6 million long-term capital lease obligation and $12.5 million of unamortized debt issuance costs.

Property, Plant and Equipment55

Property, Plant and Equipment (PPE) Property, Plant and Equipment Class and Useful Life (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Total PPE	$ 9,706.6	$ 9,355.6
Less—accumulated depreciation	2,052.2	1,766.4
Total PPE, net	7,654.4	7,589.2
Depreciable plant:
Property, Plant and Equipment [Line Items]
Total PPE	$ 9,352.7	$ 9,099.9
Weighted-Average Useful Lives (Years)	37 years	37 years
Depreciable plant: | Transmission
Property, Plant and Equipment [Line Items]
Total PPE	$ 7,930.3	$ 7,719.8
Weighted-Average Useful Lives (Years)	37 years	37 years
Depreciable plant: | Storage
Property, Plant and Equipment [Line Items]
Total PPE	$ 769.5	$ 758.5
Weighted-Average Useful Lives (Years)	38 years	38 years
Depreciable plant: | Gathering
Property, Plant and Equipment [Line Items]
Total PPE	$ 347.6	$ 336.7
Weighted-Average Useful Lives (Years)	27 years	27 years
Depreciable plant: | General
Property, Plant and Equipment [Line Items]
Total PPE	$ 182.8	$ 170
Weighted-Average Useful Lives (Years)	13 years	14 years
Depreciable plant: | Rights of way and other
Property, Plant and Equipment [Line Items]
Total PPE	$ 122.5	$ 114.9
Weighted-Average Useful Lives (Years)	37 years	36 years
Non-depreciable:
Property, Plant and Equipment [Line Items]
Total PPE	$ 353.9	$ 255.7
Non-depreciable: | Storage
Property, Plant and Equipment [Line Items]
Total PPE	105.5	105.5
Non-depreciable: | Construction work in progress
Property, Plant and Equipment [Line Items]
Total PPE	201.9	105.5
Non-depreciable: | Land
Property, Plant and Equipment [Line Items]
Total PPE	30.2	28.4
Non-depreciable: | Other
Property, Plant and Equipment [Line Items]
Total PPE	$ 16.3	$ 16.3

Property, Plant and Equipment56

Property, Plant and Equipment (PPE) Undivided Interests (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Undivided Interest Property [Line Items]
Gross PPE Investment	$ 134	$ 130.9
Accumulated Depreciation	$ 40.6	37
Bistineau storage
Undivided Interest Property [Line Items]
Undivided interests in storage facility	92.00%
Gross PPE Investment	$ 68.9	64.3
Accumulated Depreciation	$ 19.5	17.5
Mobile Bay Pipeline
Undivided Interest Property [Line Items]
Undivided interest in pipeline	64.00%
Gross PPE Investment	$ 13.2	13
Accumulated Depreciation	$ 5.1	3.6
NGL pipelines and facilities
Undivided Interest Property [Line Items]
Undivided interest in Ethylene Wells	83.00%
Gross PPE Investment	$ 34.8	34.8
Accumulated Depreciation	3.2	2.2
Offshore and other assets
Undivided Interest Property [Line Items]
Gross PPE Investment	17.1	18.8
Accumulated Depreciation	$ 12.8	$ 13.7

Property, Plant and Equipment57

Property, Plant and Equipment (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)MMcf
Asset Dispositions and Impairments [Abstract]
Asset impairment	$ 0.4	$ 10.1	$ 4.1
Gas Storage Sale
Gas Sales [Abstract]
Gain (Loss) on Disposition of Other Assets			$ 29.9
Volume Of Gas Sold (in MMcf) | MMcf			14,900
Carrying Value Before Sale or Impairment			$ 26

Goodwill and Intangible Asset58

Goodwill and Intangible Assets Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Goodwill [Line Items]
Goodwill	$ 237.4	$ 237.4
Goodwill, Impairment Loss	$ 0	$ 0	$ 51.5

Goodwill and Intangible Asset59

Goodwill and Intangible Assets Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 59.4	$ 59.4
Accumulated amortization	(5.5)	(3.5)
Net carrying amount	53.9	55.9
Amortization of Intangible Assets	2	$ 1.4	$ 1.3
2,016	2
2,017	2
2,018	2
2,019	2
2,020	1.9
Thereafter	$ 44
Finite-Lived Intangible Asset, Useful Life	28 years

Asset Retirement Obligations 60

Asset Retirement Obligations (ARO) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	$ 46.3	$ 47.1
Liabilities recorded	9.7	4.3
Liabilities settled	(5.1)	(6.9)
Accretion expense	1.7	1.8
Balance at end of year	52.6	46.3
Less: Current portion of ARO	(14.5)	(6.4)
Long-term ARO	38.1	39.9
Provision for other asset retirement	$ 57.2	$ 60.5

Regulatory Assets (Details)

Regulatory Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Regulatory Assets and Liabilities Disclosure [Abstract]
Period of recovery-minimum (in years)	1 year
Period of recovery-maximum (in years)	18 years
Regulatory Assets [Line Items]
Regulatory Assets	$ 13.7	$ 14.3
Pension
Regulatory Assets [Line Items]
Regulatory Assets	10.6	10.6
Tax effect of AFUDC equity
Regulatory Assets [Line Items]
Regulatory Assets	3.1	3.5
Fuel tracker
Regulatory Assets [Line Items]
Regulatory Assets	$ 0	$ 0.2

Regulatory Assets and Liabili62

Regulatory Assets and Liabilities Regulatory Liabilities (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Regulatory Liabilities [Line Items]
Regulatory Liabilities		$ 93.9	$ 84.5
Cashout and fuel tracker
Regulatory Liabilities [Line Items]
Regulatory Liabilities		6	0.9
Provision for other asset retirement
Regulatory Liabilities [Line Items]
Regulatory Liabilities		57.2	60.5
Loss on Reacquired Debt [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[1]	(8)	(9.6)
Unamortized discount on long-term debt
Regulatory Liabilities [Line Items]
Regulatory Liabilities		(1.2)	(1.5)
Postretirement benefits other than pension
Regulatory Liabilities [Line Items]
Regulatory Liabilities		$ 39.9	$ 34.2
[1]	The 2014 balance of unamortized debt expense and premium on reacquired debt was moved to the Regulatory Liabilities section due to the implementation of ASU 2015-03. Refer to Note 2 for more information regarding the implementation of ASU 2015-03.

Financing - Debt (Details)

Financing - Debt (Details) - USD ($) $ in Millions	Jun. 01, 2015	Mar. 10, 2015		Feb. 02, 2015	Nov. 19, 2014		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Feb. 17, 2016
Debt Instruments [Abstract]
Capital Lease Obligations, Noncurrent							$ 9.1	$ 9.6
Debt and Capital Lease Obligations							3,484.1	3,704.6
Less: unamortized debt discount							(14.4)	(14.9)
Repayments of Unsecured Debt							725	25	$ 0
Long-term debt and capital lease obligation							3,459.3	3,677.2
Long-Term Debt and Capital Lease Obligation | Adjustments for New Accounting Principle, Early Adoption [Member]
Debt Instruments [Abstract]
Debt Issuance Cost							(10.4)	$ (12.5)
Unsecured Debt
Long-term Debt, Fiscal Year Maturity [Abstract]
2,016							250
2,017							575
2,018							185
2,019							350
2,020							375
Thereafter							1,740
Total long-term debt							$ 3,475
Debt Instruments [Abstract]
Debt, Weighted Average Interest Rate							5.32%	5.31%
Debt Instrument, Redemption Price, Percentage							100.00%
Debt Instrument, Redemption, Description							The Partnerships notes and debentures are redeemable, in whole or in part, at the Partnerships option at any time, at a redemption price equal to the greater of 100% of the principal amount of the notes to be redeemed or a make whole redemption price based on the remaining scheduled payments of principal and interest discounted to the date of redemption at a rate equal to the Treasury rate plus 20 to 50 basis points depending upon the particular issue of notes, plus accrued and unpaid interest, if any. Other customary covenants apply, including those concerning events of default.
Debt Instrument, Covenant Description							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.
Debt Instrument, Covenant Compliance							At December 31, 2015, Boardwalk Pipelines and its operating subsidiaries were in compliance with their debt covenants.
Unsecured Debt | Boardwalk Pipelines 5.875% Notes Due 2016
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term debt							$ 250	$ 250
Debt Instruments [Abstract]
Debt Instrument, Interest Rate, Stated Percentage							5.875%
Unsecured Debt | Boardwalk Pipelines 5.50% Notes Due 2017
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term debt							$ 300	300
Debt Instruments [Abstract]
Debt Instrument, Interest Rate, Stated Percentage							5.50%
Unsecured Debt | Boardwalk Pipelines 5.20% Notes Due 2018
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term debt							$ 185	185
Debt Instruments [Abstract]
Debt Instrument, Interest Rate, Stated Percentage							5.20%
Unsecured Debt | Boardwalk Pipelines 5.75% Notes Due 2019
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term debt							$ 350	350
Debt Instruments [Abstract]
Debt Instrument, Interest Rate, Stated Percentage							5.75%
Unsecured Debt | Boardwalk Pipelines 3.375% Notes Due 2023
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term debt							$ 300	300
Debt Instruments [Abstract]
Debt Instrument, Interest Rate, Stated Percentage							3.375%
Unsecured Debt | Boardwalk Pipelines 4.95% Notes Due 2024
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term debt							$ 600	350
Debt Instruments [Abstract]
Debt Instrument, Issuance Date		Mar. 10, 2015			Nov. 19, 2014
Debt Instrument, Face Amount		$ 250			$ 350
Payments of Debt Issuance Costs		2.9			7.1
Proceeds from Debt, Net of Issuance Costs		$ 247.1	[1]		$ 342.9	[2]
Debt Instrument, Interest Rate, Stated Percentage		4.95%			4.95%		4.95%
Debt Instrument, Maturity Date		Dec. 15, 2024			Dec. 15, 2024
Unsecured Debt | Gulf South 5.05% Notes Due 2015
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term debt							$ 0	275
Debt Instruments [Abstract]
Debt Instrument, Interest Rate, Stated Percentage				5.05%
Repayments of Unsecured Debt				$ 275
Unsecured Debt | Gulf South 6.30% Notes Due 2017
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term debt							$ 275	275
Debt Instruments [Abstract]
Debt Instrument, Interest Rate, Stated Percentage							6.30%
Unsecured Debt | Gulf South 4.00% Notes Due 2022
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term debt							$ 300	300
Debt Instruments [Abstract]
Debt Instrument, Interest Rate, Stated Percentage							4.00%
Unsecured Debt | Texas Gas 4.60% Notes Due 2015
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term debt							$ 0	250
Debt Instruments [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	4.60%
Repayments of Unsecured Debt	$ 250
Unsecured Debt | Texas Gas 4.50% Notes Due 2021
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term debt							$ 440	440
Debt Instruments [Abstract]
Debt Instrument, Interest Rate, Stated Percentage							4.50%
Unsecured Debt | Texas Gas 7.25% Debentures Due 2027
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term debt							$ 100	100
Debt Instruments [Abstract]
Debt Instrument, Interest Rate, Stated Percentage							7.25%
Unsecured Debt | Total Notes and Debentures
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term debt							$ 3,100	3,375
Unsecured Debt | Term Loan Boardwalk Acquisition Company
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term debt							$ 0	$ 200
Debt Instruments [Abstract]
Debt, Weighted Average Interest Rate								1.91%
Debt Instrument, Maturity Date							Oct. 1, 2017
Repayments of Unsecured Debt							$ 200
Line of Credit
Line of Credit Facility [Abstract]
Line of Credit Facility, Covenant Terms							The credit facility contains various restrictive covenants and other usual and customary terms and conditions, including restrictions regarding the incurrence of additional debt, the sale of assets and sale-leaseback transactions. The financial covenants under the credit facility require the Partnership and its subsidiaries to maintain, among other things, a ratio of total consolidated debt to consolidated EBITDA (as defined in the credit agreement) measured for the previous twelve months of not more than 5.0 to 1.0, or up to 5.5 to 1.0 for the three quarters following an acquisition.
Line of Credit Facility, Covenant Compliance							The Partnership and its subsidiaries were in compliance with all covenant requirements under the credit facility as of December 31, 2015.
Line of Credit | Gulf Crossing Revolving Credit Facility
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term debt							$ 375	$ 120
Line of Credit | Amended Credit Agreement 2015
Debt Instruments [Abstract]
Debt, Weighted Average Interest Rate							1.67%	1.54%
Line of Credit Facility [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity							$ 1,500
Line of Credit Facility, Expiration Date							May 26, 2020
Maximum Ratio of Debt to EBITDA							5.0 to 1.0
Maximum Ratio of Debt to EBITDA after Acquisition							5.5 to 1.0
Long-term Line of Credit							$ 375	$ 120
Line of Credit | Amended Credit Agreement 2015 | Subsequent Event
Line of Credit Facility [Abstract]
Long-term Line of Credit										$ 470
Line of Credit Facility, Remaining Borrowing Capacity										$ 1,000
Line of Credit | Amended Credit Agreement 2015 | Minimum [Member]
Line of Credit Facility [Abstract]
Line of Credit Facility, Commitment Fee Percentage							0.10%
Line of Credit | Amended Credit Agreement 2015 | Maximum [Member]
Line of Credit Facility [Abstract]
Line of Credit Facility, Commitment Fee Percentage							0.275%
Line of Credit | Amended Credit Agreement 2015 | Base Rate
Line of Credit Facility [Abstract]
Debt Instrument, Description of Variable Rate Basis							base rate
Line of Credit | Amended Credit Agreement 2015 | Base Rate | Minimum [Member]
Line of Credit Facility [Abstract]
Debt Instrument, Basis Spread on Variable Rate							0.00%
Line of Credit | Amended Credit Agreement 2015 | Base Rate | Maximum [Member]
Line of Credit Facility [Abstract]
Debt Instrument, Basis Spread on Variable Rate							0.75%
Line of Credit | Amended Credit Agreement 2015 | Prime Rate
Line of Credit Facility [Abstract]
Debt Instrument, Description of Variable Rate Basis							prime rate
Line of Credit | Amended Credit Agreement 2015 | Federal Funds Effective Swap Rate
Line of Credit Facility [Abstract]
Debt Instrument, Description of Variable Rate Basis							federal funds
Debt Instrument, Basis Spread on Variable Rate							0.50%
Line of Credit | Amended Credit Agreement 2015 | Eurodollar
Line of Credit Facility [Abstract]
Debt Instrument, Description of Variable Rate Basis							one month Eurodollar Rate
Debt Instrument, Basis Spread on Variable Rate							1.00%
Line of Credit | Amended Credit Agreement 2015 | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Abstract]
Debt Instrument, Description of Variable Rate Basis							LIBOR
Line of Credit | Amended Credit Agreement 2015 | London Interbank Offered Rate (LIBOR) | Minimum [Member]
Line of Credit Facility [Abstract]
Debt Instrument, Basis Spread on Variable Rate							1.00%
Line of Credit | Amended Credit Agreement 2015 | London Interbank Offered Rate (LIBOR) | Maximum [Member]
Line of Credit Facility [Abstract]
Debt Instrument, Basis Spread on Variable Rate							1.75%
Capital Lease Obligations
Debt Instruments [Abstract]
Capital Lease Obligations, Noncurrent							$ 9.1	$ 9.6
Subordinated Debt
Debt Instruments [Abstract]
Debt Instrument, Maturity Date							Jul. 31, 2024
Subordinated Loan Agreement Maximum Borrowing Capacity							$ 300
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum							5.75%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum							9.75%
[1]	The net proceeds of this offering were used to retire a portion of the outstanding $250.0 million aggregate principal amount of the Texas Gas 2015 Notes. Initially, the Partnership used the net proceeds to reduce outstanding borrowings under its revolving credit facility. Subsequently, on June 1, 2015, the Partnership retired the Texas Gas 2015 Notes with borrowings under its revolving credit facility.
[2]	The net proceeds of this offering were used to retire all of the outstanding Gulf South 2015 Notes and the remainder of the net proceeds were used to reduce outstanding borrowings under the Partnership's revolving credit facility.

Financing Financing - Equity (D

Financing Financing - Equity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		Oct. 09, 2013	May. 29, 2013	Apr. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Capital Unit [Line Items]
Conversion of Stock, Shares Converted (Class B)		22.9
Percent of General Partner Interest Owned by Holding Company (in hundredths)					2.00%	2.00%	2.00%
Common units
Capital Unit [Line Items]
Stock Issued During Period, Shares, New Issues						0
Common units | Equity Distribution Agreement
Capital Unit [Line Items]
Common units issued under an equity distribution agreement				7	7
Issuance Price (in dollars per share)	[1]			$ 16.19
Less Underwriting Discounts and Expenses				$ 1.1
Proceeds from Issuance or Sale of Equity				$ 115.4	$ 115.4
Common Units Outstanding After Offering	[2]			250.3
Common Units Held by the Public After Offering				124.6
Percent of General Partner Interest Owned by Holding Company (in hundredths)					2.00%
Limited Partners Capital Account Units Authorized Dollars					$ 500
General Partners' Contributed Capital					$ 2.3
Common units | Second Quarter 2013 Offering
Capital Unit [Line Items]
Stock Issued During Period, Shares, New Issues			12.7
Issuance Price (in dollars per share)			$ 30.12
Less Underwriting Discounts and Expenses			$ 12.3
Proceeds from Issuance or Sale of Equity			$ 376.5
Common Units Outstanding After Offering			220.3
Common Units Held by the Public After Offering			117.6
Percent of General Partner Interest Owned by Holding Company (in hundredths)			2.00%
Common units
Capital Unit [Line Items]
Common units issued under an equity distribution agreement					7
Conversion of Stock, Shares Converted (Class B)		22.9
[1]	The issuance price represents the average issuance price for the common units issued under an equity distribution agreement described further below.
[2]	On October 9, 2013, all of the 22.9 million class B units were converted into common units on a one-for-one basis, pursuant to the terms of the partnership agreement.

Financing Summary of Changes in

Financing Summary of Changes in Outstanding Units (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		Oct. 09, 2013	Dec. 31, 2015	Dec. 31, 2013	Dec. 31, 2014
Conversion of Stock, Shares Converted (Class B)		22.9
Number of common units registered for resale under Amended and Restated Registration Rights Agreement (in number of units)			27.9
Maximum amount Partnership must pay for reimbursement of underwriting discounts and commissions (in dollars per unit)			$ 0.914
Accrued liability for future underwriting discounts and commissions			$ 16		$ 16
Common units
Balance, Beginning (in units)			243.3	207.7
Common units issued in connection with underwritten offerings				12.7
Conversion of Stock, Shares Converted (Class B)		22.9
Common units issued under an equity distribution agreement			7
Balance, Ending (in units)			250.3	243.3
Class B units
Balance, Beginning (in units)	[1]		0	22.9
Common units issued in connection with underwritten offerings	[1]			0
Conversion of Stock, Shares Converted (Class B)	[1]	(22.9)
Common units issued under an equity distribution agreement	[1]		0
Balance, Ending (in units)	[1]		0	0
[1]	On October 9, 2013, all of the 22.9 million class B units were converted into common units on a one-for-one basis, pursuant to the terms of the partnership agreement.

Employee Benefits (Details)

Employee Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Contribution Plan, Cost Recognized	$ 9.8	$ 9	$ 8.6
Retirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contribution to defined benefit pension plan	$ 3	3
Future rate recovery	in excess of $6.0 million
PBOP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contribution to defined benefit pension plan	$ 0.1	0.1
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Required amount of funding of periodic pension cost	3
Contribution to defined benefit pension plan	3	3
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year	3
Minimum amount of recognize expense each year associated with retirement plan	3
Precluded future recovery of annual pension costs, lower range	3
Precluded future recovery of annual pension costs, upper range	$ 6
Recognition of regulatory assets	in excess of $6.0 million
Reduction of regulatory assets	less than $3.0 million
Pension plan costs charged to expense, lower range	$ 3
Pension plan costs charged to expense, upper range	6
SRP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contribution to defined benefit pension plan	$ 0	$ 0

Employee Benefits, Projected Be

Employee Benefits, Projected Benefit Obligation, Fair Value of Assets, Funded Status and the Amounts Not Yet Recognized As Components of Net Periodic Pension and Postretirement Benefits Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Change in Plan Assets [Roll Forward]
Fair value of plan assets at beginning of period	$ 256.2
Fair value of plan assets at end of period	234.3	$ 256.2
Retirement Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of period	149.9	148.5
Service cost	3.8	3.9	$ 3.9
Interest cost	4.9	5.8	5
Plan participants’ contributions	0	0
Actuarial (gain) loss	(1.9)	3.6
Benefits paid	(0.5)	(0.5)
Settlement	(12.4)	(11.4)
Benefit obligation at end of period	143.8	149.9	148.5
Change in Plan Assets [Roll Forward]
Fair value of plan assets at beginning of period	130.7	131.4
Actual return on plan assets	(1.3)	8.2
Benefits paid	(0.5)	(0.5)
Settlement	(12.4)	(11.4)
Company contributions	3	3
Plan participants’ contributions	0	0
Fair value of plan assets at end of period	119.5	130.7	131.4
Funded status	(24.3)	(19.2)
Items Not Recognized As Components Of Net Periodic Cost [Abstract]
Prior service cost (credit)	0	0
Net actuarial loss	29.9	26
Total	29.9	26
PBOP
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of period	55.1	50
Service cost	0.3	0.4	0.5
Interest cost	2	2.2	2.1
Plan participants’ contributions	1.1	0.9
Actuarial (gain) loss	(5.6)	5.2
Benefits paid	(4.5)	(3.6)
Settlement	0	0
Benefit obligation at end of period	48.4	55.1	50
Change in Plan Assets [Roll Forward]
Fair value of plan assets at beginning of period	87.3	80.8
Actual return on plan assets	2.4	9.1
Benefits paid	(4.5)	(3.6)
Settlement	0	0
Company contributions	0.1	0.1
Plan participants’ contributions	1.1	0.9
Fair value of plan assets at end of period	86.4	87.3	$ 80.8
Funded status	38	32.2
Items Not Recognized As Components Of Net Periodic Cost [Abstract]
Prior service cost (credit)	(0.9)	(8.6)
Net actuarial loss	7.2	10.7
Total	$ 6.3	$ 2.1

Employee Benefits, Aggregate In

Employee Benefits, Aggregate Information Related Only to the Underfunded Plans (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 143.8	$ 149.9
Accumulated benefit obligation	134.1	139.7
Fair value of plan assets	$ 119.5	$ 130.7

Employee Benefits, Components o

Employee Benefits, Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Retirement Plans
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 3.8	$ 3.9	$ 3.9
Interest cost	4.9	5.8	5
Expected return on plan assets	(9.1)	(9.5)	(9.1)
Amortization of prior service credit	0	0	0
Amortization of unrecognized net loss	2	1.4	2.1
Settlement charge	2.5	1.9	1.7
Net periodic benefit cost	$ 4.1	3.5	3.6
Future rate recovery	in excess of $6.0 million
PBOP
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 0.3	0.4	0.5
Interest cost	2	2.2	2.1
Expected return on plan assets	(4.6)	(4.2)	(4.5)
Amortization of prior service credit	(7.7)	(7.8)	(7.8)
Amortization of unrecognized net loss	0	0.3	0
Settlement charge	0	0	0
Net periodic benefit cost	$ (10)	$ (9.1)	$ (9.7)

Employee Benefits, Estimated Fu

Employee Benefits, Estimated Future Benefit Payments (Details) $ in Millions	Dec. 31, 2015USD ($)
Retirement Plans
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity [Abstract]
2,016	$ 18.9
2,017	13.4
2,018	13.7
2,019	14.8
2,020	13.7
2021-2025	64.3
PBOP
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity [Abstract]
2,016	2.9
2,017	3
2,018	3.2
2,019	3.2
2,020	3.2
2021-2025	$ 15.5

Employee Benefits, Weighted-Ave

Employee Benefits, Weighted-Average Assumptions Used to Determine Benefit Obligations (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Plan
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate (percent)	3.60%	3.35%
Expected return on plan assets (percent)	7.50%	7.50%	7.50%
Rate of compensation increase (percent)	3.50%	3.50%
SRP
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate (percent)	4.00%	3.75%
Expected return on plan assets (percent)	7.50%	7.50%	7.50%
Rate of compensation increase (percent)	3.50%	3.50%
PBOP
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate (percent)	4.25%	3.90%
Expected return on plan assets (percent)	5.30%	5.30%	5.30%
Rate of compensation increase (percent)	0.00%	0.00%

Employee Benefits, Weighted-A72

Employee Benefits, Weighted-Average Assumptions Used to Determine Net Periodic Benefit Cost (Details)	3 Months Ended		4 Months Ended		8 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2013	[1]	Dec. 31, 2015	[2]	Aug. 31, 2015	[2]	Sep. 30, 2013	[1]	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Plan
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate (percent)	4.10%		3.60%		3.35%		3.25%			4.00%
Expected return on plan assets (percent)									7.50%	7.50%	7.50%
Rate of compensation increase (percent)									3.50%	3.50%	3.50%
SRP
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate (percent)									3.75%	4.25%	3.50%
Expected return on plan assets (percent)									7.50%	7.50%	7.50%
Rate of compensation increase (percent)									3.50%	3.50%	3.50%
PBOP
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate (percent)									3.90%	4.50%	3.90%
Expected return on plan assets (percent)									5.30%	5.30%	5.30%
Rate of compensation increase (percent)									0.00%	0.00%	0.00%
[1]	Pension expense was remeasured at September 30, 2013, to reflect a settlement.
[2]	Pension expense was remeasured at August 31, 2015, to reflect a settlement

Employee Benefits, Effect of On

Employee Benefits, Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates (Details) - PBOP - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan, Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rates [Abstract]
Defined Benefit Plan, Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation	$ 2
Defined Benefit Plan, Effect of One Percentage Point Increase on Service and Interest Cost Components	0.1
Defined Benefit Plan, Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation	(1.8)
Defined Benefit Plan, Effect of One Percentage Point Decrease on Service and Interest Cost Components	$ (0.1)
Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Next Fiscal Year	7.50%	8.00%
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate	5.00%	5.00%
Defined Benefit Plan, Year that Rate Reaches Ultimate Trend Rate	2,021	2,022
Annual increments for change	0.50%	0.50%

Employee Benefits, Master Trust

Employee Benefits, Master Trust Pension and PBOP Fair Value Hierarchy (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	$ 234.3	$ 256.2
Pension Plan
Defined Contribution Plan Disclosure [Line Items]
Amount committed to future capital calls in exchange for an ownership interest	7.3
Pension Plan | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	137.5	153.9
Pension Plan | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	56.1	62.7
Pension Plan | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	40.7	39.6
Pension Plan | Equity securities
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	$ 36.1	42.3
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum	40.00%
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum	60.00%
Pension Plan | Equity securities | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	$ 36.1	42.3
Pension Plan | Equity securities | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plan | Equity securities | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plan | Short-term investments
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	6.6	11.8
Pension Plan | Short-term investments | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	6.6	11.8
Pension Plan | Short-term investments | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plan | Short-term investments | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plan | Other assets | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets		1.1
Pension Plan | Other assets | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets		1.1
Pension Plan | Other assets | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets		0
Pension Plan | Other assets | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets		0
Pension Plan | Fixed income mutual funds
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	94.8	98.7
Pension Plan | Fixed income mutual funds | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	94.8	98.7
Pension Plan | Fixed income mutual funds | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plan | Fixed income mutual funds | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plan | Asset-backed securities
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	6.4	6
Pension Plan | Asset-backed securities | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plan | Asset-backed securities | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	6.4	6
Pension Plan | Asset-backed securities | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plan | Hedge Funds
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	80.7	86.2
Pension Plan | Hedge Funds | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plan | Hedge Funds | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	49.7	56.7
Pension Plan | Hedge Funds | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	31	29.5
Pension Plan | Private Equity Funds
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	9.7	10.1
Pension Plan | Private Equity Funds | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plan | Private Equity Funds | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Pension Plan | Private Equity Funds | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	$ 9.7	10.1
Pension Plan | Alternative Investments [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum	40.00%
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum	60.00%
Retirement Plans
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	$ 119.5	$ 130.7	$ 131.4
Master Trust percentage of pension plan assets	51.00%	51.00%
PBOP
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	$ 86.4	$ 87.3	$ 80.8
Allocation to fixed income securities	100.00%	100.00%
PBOP | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	$ 7.7	$ 6.2
PBOP | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	78.7	81.1
PBOP | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
PBOP | Short-term investments
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	3	3.2
PBOP | Short-term investments | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	3	3.2
PBOP | Short-term investments | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
PBOP | Short-term investments | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
PBOP | Fixed income mutual funds
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	4.7	3
PBOP | Fixed income mutual funds | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	4.7	3
PBOP | Fixed income mutual funds | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
PBOP | Fixed income mutual funds | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
PBOP | Asset-backed securities
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	18.8	20.4
PBOP | Asset-backed securities | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
PBOP | Asset-backed securities | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	18.8	20.4
PBOP | Asset-backed securities | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
PBOP | Corporate Bond Securities [Member]
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	17	17.8
PBOP | Corporate Bond Securities [Member] | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
PBOP | Corporate Bond Securities [Member] | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	17	17.8
PBOP | Corporate Bond Securities [Member] | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
PBOP | Tax Exempt Securities [Member]
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	42.9	42.9
PBOP | Tax Exempt Securities [Member] | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	0	0
PBOP | Tax Exempt Securities [Member] | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	42.9	42.9
PBOP | Tax Exempt Securities [Member] | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Defined Contribution Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0

Employee Benefits, Fair Value M

Employee Benefits, Fair Value Measurement Using Significant Unobservable Inputs, Master Trust (Details) - Pension Plan - Fair Value, Inputs, Level 3 - Fair Value, Measurements, Recurring - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Limited Partnership: Hedge funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of period	$ 29.5	$ 29.7
Actual return on assets still held	1	2.1
Actual return on assets sold	0.2	0.1
Purchases, sales and settlements	(0.3)	(2.4)
Net transfers into Level 3	0.6
Fair value of plan assets at end of period	31	29.5
Limited Partnership: Private equity
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of period	10.1	11.7
Actual return on assets still held	0.6	0.2
Actual return on assets sold	0.1	0.8
Purchases, sales and settlements	(1.1)	(2.6)
Net transfers into Level 3	0
Fair value of plan assets at end of period	$ 9.7	$ 10.1

Employee Benefits, Summary of A

Employee Benefits, Summary of Activity in LTIP Incentive Compensation Plan (Details) - LTIP - Phantom Share Units (PSUs) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2015USD ($)yr$ / sharesshares	Dec. 31, 2014USD ($)yr$ / sharesshares	Dec. 31, 2013USD ($)yrshares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding balance, beginning (in units)		199,669	380,048
Granted (in units)		647,256
Paid (in units)		(196,748)	(171,411)
Forfeited (in units)		(4,209)	(8,968)
Outstanding balance, ending (in units)		645,968	199,669	380,048
Unit Appreciation Rights and All Unit-Based Incentive Compensation Plans, Units, Fair Value [Abstract]
Outstanding balance, beginning | $	[1]	$ 4.1	$ 10.9
Granted | $		10.1
Paid | $		(2.9)	(3.5)
Forfeited | $		0	0
Outstanding balance, ending | $	[1]	$ 8.7	$ 4.1	$ 10.9
Unit Appreciation Rights and All Unit-Based Incentive Compensation Plans, Units, Weighted-Average Vesting Period [Abstract]
Outstanding balance, beginning (in years) | yr	[1]	0.9	1.5
Granted (in years) | yr		2.4
Outstanding balance, ending (in years) | yr	[1]	1.5	0.9	1.5
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized		3,525,000
Closing market price of the common unit | $ / shares		$ 12.98	$ 17.77
Compensation expense | $		$ 3.6	$ 1.2	$ 3.2
Total estimated remaining unrecognized compensation expense related to the Phantom Common Units outstanding | $		$ 5.5	$ 1.6
Share-based Compensation Arrangement by Share-based Payment Award, Shares Purchased for Award		12,180	16,064
Share-based Compensation Arrangement by Share-based Payment Award, Per Share Weighted Average Price of Shares Purchased | $ / shares		$ 16.57	$ 12.51
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant		3,477,980
[1]	Represents fair value and remaining weighted-average vesting period of outstanding awards at the end of the period.

Employee Benefits, Valuation As

Employee Benefits, Valuation Assumptions Under Unit Appreciation Rights (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Long-Term Cash Bonus Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash Bonus Granted During Period		$ 9.2
Deferred Compensation Arrangement with Individual, Compensation Expense	$ 2.8	2.6	$ 0.5
Unrecognized compensation cost	3.6
Unit Appreciation Rights | Stock Appreciation Rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unit-based Compensation Arrangement by Unit-based Payment Award, Equity Instruments Other than Options, Outstanding Balance, Fair Value	0	0
Allocated Share-based Compensation Expense	$ 0	$ (0.7)	$ 0.9

Employee Benefits Employee Bene

Employee Benefits Employee Benefits, Retention Payment Agreements (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Mar. 06, 2015
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Deferred Compensation Arrangement with Individual, Requisite Service Period		3 years
Retention Payment Agreements
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Deferred Compensation Arrangement with Individual, Cash Award Granted, Amount		$ 12
25% Vested on February 28, 2015		25.00%
25% Vesting on February 29, 2016		25.00%
50% Vesting on February 28, 2017		50.00%
Deferred Compensation Arrangement with Individual, Distributions Paid			$ 2.9
Deferred Compensation Arrangement with Individual, Compensation Expense	$ 3.8	$ 4.8
Unrecognized Compensation Cost for Retention Payments	$ 3.1

Cash Distributions and Net In79

Cash Distributions and Net Income per Unit (Details)	12 Months Ended
	Dec. 31, 2015$ / shares
First Target Distribution Range [Member]
Cash Distribution [Abstract]
Maximum target distribution amount (in dollars per share)	$ 0.4025
Marginal Percentage Interest in Distributions - Limited Partner Unitholders	98.00%
Marginal Percentage Interest in Distributions - General Partner and IDRs Unitholders	2.00%
Second Target Distribution Range [Member] [Member]
Cash Distribution [Abstract]
Minimum target distribution amount (in dollars per share)	$ 0.4025
Maximum target distribution amount (in dollars per share)	$ 0.4375
Marginal Percentage Interest in Distributions - Limited Partner Unitholders	85.00%
Marginal Percentage Interest in Distributions - General Partner and IDRs Unitholders	15.00%
Third Target Distribution Range [Member]
Cash Distribution [Abstract]
Minimum target distribution amount (in dollars per share)	$ 0.4375
Maximum target distribution amount (in dollars per share)	$ 0.5250
Marginal Percentage Interest in Distributions - Limited Partner Unitholders	75.00%
Marginal Percentage Interest in Distributions - General Partner and IDRs Unitholders	25.00%
Thereafter Target Distribution Range [Member]
Cash Distribution [Abstract]
Minimum target distribution amount (in dollars per share)	$ 0.5250
Marginal Percentage Interest in Distributions - Limited Partner Unitholders	50.00%
Marginal Percentage Interest in Distributions - General Partner and IDRs Unitholders	50.00%

Cash Distributions and Net In80

Cash Distributions and Net Income per Unit Distributions Made to Members or Limited Partners (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		Oct. 09, 2013	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Distribution Made to Limited Partner [Line Items]
Payment Date			Nov. 19, 2015	Aug. 20, 2015	May 21, 2015	Feb. 26, 2015	Nov. 20, 2014	Aug. 21, 2014	May 15, 2014	Feb. 27, 2014	Nov. 14, 2013		Aug. 15, 2013	May 16, 2013	Feb. 28, 2013
Distribution per Unit			$ 0.1000	$ 0.1000	$ 0.1000	$ 0.1000	$ 0.1000	$ 0.1000	$ 0.1000	$ 0.1000	$ 0.5325		$ 0.5325	$ 0.5325	$ 0.5325	$ 0.1000	$ 0.1000	$ 0.5325
Amount Paid to Common Unitholders			$ 25	$ 25.1	$ 25.1	$ 24.3	$ 24.3	$ 24.3	$ 24.3	$ 24.3	$ 129.5		$ 117.3	$ 110.6	$ 110.6
Amount Paid to Class B Unitholder			0	0	0	0	0	0	0	0	0	[1]	6.9	6.8	6.9
Amount Paid to General Partner (Including IDRs)	[2]		$ 0.5	$ 0.5	$ 0.5	$ 0.5	$ 0.5	$ 0.5	$ 0.5	$ 0.5	$ 12.4		$ 11.4	$ 10.7	$ 10.8
General partner interest (percent)			2.00%				2.00%				2.00%					2.00%	2.00%	2.00%
Incentive Distribution, Distribution																$ 0	$ 0	$ 34.6
Conversion of Stock, Shares Converted (Class B)		22.9
[1]	On October 9, 2013, all of the 22.9 million Class B units were converted into common units on a one-for-one basis, pursuant to the terms of the partnership agreement.
[2]	In February 2014, the Partnership decreased its distribution rate to $0.10 per common unit. As a result of the reduced distribution rate, the quarterly target distribution levels for IDR payout were not met and the Partnership paid no amounts with respect to the IDRs in 2015 and 2014. In 2013, the Partnership paid $34.6 million in distributions on behalf of IDRs.

Cash Distributions and Net In81

Cash Distributions and Net Income per Unit Reconciliation of Net Income and the Assumed Allocation of Net Income (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation And Allocation of Net Income By Class of Stock [Line Items]
Class B unitholders' maximum quarterly distribution per unit											$ 0.30
Net income per unit [Abstract]
Net income	$ 65.6	$ 38.3	$ 40.4	$ 77.7	$ 36.9	$ 28.4	$ 55.9	$ 25.6	$ 222	$ 146.8	$ 250.2
Net loss attributable to noncontrolling interests	0	0	0	0	0.1	(0.8)	(1.5)	(84.6)	0	(86.8)	(3.5)
Net income attributable to controlling interests	$ 65.6	$ 38.3	$ 40.4	$ 77.7	$ 36.8	$ 29.2	$ 57.4	$ 110.2	222	233.6	253.7
Declared distribution									102.2	99.2	430.5
Assumed allocation of undistributed net income (loss)									119.8	134.4	(176.8)
Assumed allocation of net income attributable to limited partner unitholders and general partner									222	233.6	253.7
Allocation for diluted earnings per unit											0
Assumed allocation of net income attributable to limited partner unitholders and general partner - diluted											253.7
Common units
Net income per unit [Abstract]
Declared distribution									100.2	97.2	381.8
Assumed allocation of undistributed net income (loss)									117.3	131.7	(160.5)
Assumed allocation of net income attributable to limited partner unitholders and general partner									$ 217.5	$ 228.9	221.3
Allocation for diluted earnings per unit											(4.6)
Assumed allocation of net income attributable to limited partner unitholders and general partner - diluted											$ 216.7
Weighted-average units outstanding									248.8	243.3	220.5
Weighted-average units outstanding - diluted									0	243.3	226.8
Net income per unit									$ 0.87	$ 0.94	$ 1
Diluted net income per unit:									$ 0	$ 0.94	$ 0.96
Class B units
Net income per unit [Abstract]
Declared distribution											$ 13.7
Assumed allocation of undistributed net income (loss)											(12.8)
Assumed allocation of net income attributable to limited partner unitholders and general partner											0.9
Allocation for diluted earnings per unit											4.6
Assumed allocation of net income attributable to limited partner unitholders and general partner - diluted											$ 5.5
Weighted-average units outstanding									0	0	17.6
Weighted-average units outstanding - diluted									0	0	11.3
Net income per unit									$ 0	$ 0	$ 0.05
Diluted net income per unit:									$ 0	$ 0	$ 0.48
General Partner And IDRs
Net income per unit [Abstract]
Declared distribution									$ 2	$ 2	$ 35
Assumed allocation of undistributed net income (loss)									2.5	2.7	(3.5)
Assumed allocation of net income attributable to limited partner unitholders and general partner									$ 4.5	$ 4.7	31.5
Allocation for diluted earnings per unit											0
Assumed allocation of net income attributable to limited partner unitholders and general partner - diluted											$ 31.5

Cash Distributions and Net In82

Cash Distributions and Net Income per Unit Subsequent Event (Details)	Feb. 19, 2016$ / shares
Subsequent Event
Subsequent Event [Line Items]
Dividends Payable, Amount Per Share	$ 0.10

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
State and Local Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current expense: State									$ 0.4	$ 0.3	$ 0.4
Total									0.4	0.3	0.4
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred provision: State									0.1	0.1	0.1
Total									0.1	0.1	0.1
Income taxes	$ 0.1	$ 0.1	$ 0.1	$ 0.2	$ 0	$ 0.1	$ 0.1	$ 0.2	0.5	0.4	0.5
Summary of the Provision for Income Taxes [Line Items]
Deferred Tax Assets, Net	$ 0				$ 0				0	0
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount									$ 0	$ 0	$ 0
Earliest Tax Year [Member]
Summary of the Provision for Income Taxes [Line Items]
Open Tax Year									2,012
Latest Tax Year [Member]
Summary of the Provision for Income Taxes [Line Items]
Open Tax Year									2,015

Credit Risk (Details)

Credit Risk (Details) MMBbls in Millions, MMBTU in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015USD ($)$ / MMBTUMMBTUMMBbls	Sep. 30, 2015USD ($)	Jun. 30, 2015USD ($)	Mar. 31, 2015USD ($)	Dec. 31, 2014USD ($)$ / MMBTUMMBTUMMBbls	Sep. 30, 2014USD ($)	Jun. 30, 2014USD ($)	Mar. 31, 2014USD ($)	Dec. 31, 2015USD ($)$ / MMBTUMMBTUMMBbls	Dec. 31, 2014USD ($)$ / MMBTUMMBTUMMBbls	Dec. 31, 2013USD ($)
Concentration Risk [Line Items]
Operating revenues	$ 326.8	$ 294.1	$ 298.6	$ 329.7	$ 304.6	$ 278.9	$ 293.4	$ 356.9	$ 1,249.2	$ 1,233.8	$ 1,205.6
Gas loaned to customers [Abstract]
Gas Balancing Volume Amount (in MMBtu) | MMBTU	7.7				10				7.7	10
Average Market Price Of Gas Assumed | $ / MMBTU	1.86				3.36				1.86	3.36
Gas Imbalance To Subsidiaries Asset Liability	$ 14.3				$ 33.6				$ 14.3	$ 33.6
Natural Gas Liquids Balancing Volume (in MMBbls) (Less than) | MMBbls	0.1				0.1				0.1	0.1
Natural Gas Liquids Imbalance to Subsidiaries Asset Liability	$ 0.2				$ 0.6				$ 0.2	$ 0.6
Customer Concentration Risk
Concentration Risk [Line Items]
Operating revenues										$ 120.5	$ 127.1
Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration Risk, Percentage										10.00%	11.00%
Revenue | Product Concentration Risk
Concentration Risk [Line Items]
Concentration Risk, Percentage									50.00%

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	$ 8.8	$ 8.8	$ 8.3
Percent of General Partner Interest Owned by Holding Company (in hundredths)	2.00%	2.00%	2.00%
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	$ 0	$ 0
Distributions from unconsolidated affiliates	0	11.1	$ 0
Distributions paid to noncontrolling interests	0	7.9	0
Boardwalk GP, LP
Related Party Transaction [Line Items]
Cash dividends paid to Parent Company	52.2	52	296.8
Boardwalk Pipeline Partners, LP | Boardwalk Bluegrass and Boardwalk Moss Lake
Related Party Transaction [Line Items]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		0.8	11.9
Distributions from unconsolidated affiliates		2.2
Boardwalk Pipelines Holding Company | Boardwalk Bluegrass and Boardwalk Moss Lake
Related Party Transaction [Line Items]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		8.2	$ 90
Distributions paid to noncontrolling interests		$ 7.9
Subordinated Debt
Related Party Transaction [Line Items]
Subordinated Loan Agreement Maximum Borrowing Capacity	$ 300

Supplemental Disclosure of Ca86

Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash paid during the period for:
Interest (net of amount capitalized)	$ 170.6	$ 153	$ 151
Income taxes, net	0.3	0.1	0.3
Non-cash adjustments:
Accounts payable and PPE	54.7	36.9	38.1
Capital lease obligations incurred	$ 0	$ 0	$ 10.5

Selected Quarterly Financial 87

Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating revenues	$ 326.8	$ 294.1	$ 298.6	$ 329.7	$ 304.6	$ 278.9	$ 293.4	$ 356.9	$ 1,249.2	$ 1,233.8	$ 1,205.6
Operating expenses	220.4	213.4	212.7	206.9	224.1	210.4	196.9	204.3	853.4	835.7	791.1
Operating income	106.4	80.7	85.9	122.8	80.5	68.5	96.5	152.6	395.8	398.1	414.5
Interest expense, net	42.1	43	45.8	45.1	44.2	39.9	40	40.8
Other Income	(1.4)	(0.7)	(0.4)	(0.2)	(0.6)
Other expense						0.1	0.5	86
Income before income taxes	65.7	38.4	40.5	77.9	36.9	28.5	56	25.8	222.5	147.2	250.7
Income taxes	0.1	0.1	0.1	0.2	0	0.1	0.1	0.2	0.5	0.4	0.5
Net Income	65.6	38.3	40.4	77.7	36.9	28.4	55.9	25.6	222	146.8	250.2
Net earnings (loss) attributable to noncontrolling interests	0	0	0	0	0.1	(0.8)	(1.5)	(84.6)	0	(86.8)	(3.5)
Net income attributable to controlling interests	$ 65.6	$ 38.3	$ 40.4	$ 77.7	$ 36.8	$ 29.2	$ 57.4	$ 110.2	$ 222	$ 233.6	$ 253.7
Common units
Basic net income per unit:
Basic net income per unit:	$ 0.26	$ 0.15	$ 0.16	$ 0.31	$ 0.15	$ 0.12	$ 0.23	$ 0.44

Guarantee of Securities of Su88

Guarantee of Securities of Subsidiaries Balance Sheets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Subsidiary or Equity Method Investee, 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 have no significant restrictions on their ability to pay distributions or make loans to the Partnership except as noted in the debt covenants and have no restricted assets at December 31, 2015 and 2014.
Assets
Cash and cash equivalents	$ 3.1	6.6	$ 28.5	$ 3.9
Receivables	129.5	110.9
Receivables - affiliate	0	0
Gas and liquids stored underground	10.7	4.1
Prepayments	16.9	14.5
Advances to affiliates	0	0
Other current assets	9.6	13.5
Total current assets	169.8	149.6
Investment in consolidated subsidiaries	0	0
Property, plant and equipment, gross	9,706.6	9,355.6
Less—accumulated depreciation and amortization	2,052.2	1,766.4
Property, plant and equipment, net	7,654.4	7,589.2
Other noncurrent assets	476.1	455.5
Advances to affiliates – noncurrent	0	0
Total other assets	476.1	455.5
Total Assets	8,300.3	8,194.3
Liabilities and Partners' Capital
Payables	118.6	62.1
Payable to affiliates	1.3	1.5
Advances from affiliates	0	0
Other current liabilities	194.5	156.6
Total current liabilities	314.4	220.2
Long-term debt and capital lease obligation	3,459.3	3,677.2
Payable to affiliate - noncurrent	16	16
Advances from affiliates - noncurrent	0	0
Other noncurrent liabilities	183.9	178.6
Total other liabilities and deferred credits	199.9	194.6
Total partners’ capital	4,326.7	4,102.3
Total Liabilities and Partners' Capital	8,300.3	8,194.3
Reportable Legal Entities | Parent Guarantor
Assets
Cash and cash equivalents	0	0.5	0.2	0.1
Receivables	0	0
Receivables - affiliate	0	0
Gas and liquids stored underground	0	0
Prepayments	0.2	0.1
Advances to affiliates	0	0
Other current assets	0	0.5
Total current assets	0.2	1.1
Investment in consolidated subsidiaries	2,153.5	1,970.6
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
Other noncurrent assets	0.4	0
Advances to affiliates – noncurrent	2,190.2	2,148.3
Total other assets	2,190.6	2,148.3
Total Assets	4,344.3	4,120
Liabilities and Partners' Capital
Payables	0.3	0.2
Payable to affiliates	1.3	1.5
Advances from affiliates	0	0
Other current liabilities	0	0
Total current liabilities	1.6	1.7
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	4,326.7	4,102.3
Total Liabilities and Partners' Capital	4,344.3	4,120
Reportable Legal Entities | Subsidiary Issuer
Assets
Cash and cash equivalents	0.3	1.8	9.2	1
Receivables	0	0
Receivables - affiliate	0	0
Gas and liquids stored underground	0	0
Prepayments	0	0
Advances to affiliates	21	6.3
Other current assets	0	0
Total current assets	21.3	8.1
Investment in consolidated subsidiaries	7,067.6	6,744.1
Property, plant and equipment, gross	0	0
Less—accumulated depreciation and amortization	0	0
Property, plant and equipment, net	0	0
Other noncurrent assets	3	1.7
Advances to affiliates – noncurrent	466.3	212
Total other assets	469.3	213.7
Total Assets	7,558.2	6,965.9
Liabilities and Partners' Capital
Payables	0.1	0.1
Payable to affiliates	0	0
Advances from affiliates	107.7	106.2
Other current liabilities	20.9	21.4
Total current liabilities	128.7	127.7
Long-term debt and capital lease obligation	1,972.4	1,722.8
Payable to affiliate - noncurrent	0	0
Advances from affiliates - noncurrent	3,303.6	3,144.8
Other noncurrent liabilities	0	0
Total other liabilities and deferred credits	3,303.6	3,144.8
Total partners’ capital	2,153.5	1,970.6
Total Liabilities and Partners' Capital	7,558.2	6,965.9
Reportable Legal Entities | Non-Guarantor Subsidiaries
Assets
Cash and cash equivalents	2.8	4.3	19.1	2.8
Receivables	129.5	110.9
Receivables - affiliate	7	9
Gas and liquids stored underground	10.7	4.1
Prepayments	16.7	14.4
Advances to affiliates	107.7	106.2
Other current assets	12.8	19.2
Total current assets	287.2	268.1
Investment in consolidated subsidiaries	0	0
Property, plant and equipment, gross	9,706	9,355
Less—accumulated depreciation and amortization	2,051.6	1,765.8
Property, plant and equipment, net	7,654.4	7,589.2
Other noncurrent assets	472.7	454.4
Advances to affiliates – noncurrent	1,113.4	996.5
Total other assets	1,586.1	1,450.9
Total Assets	9,527.7	9,308.2
Liabilities and Partners' Capital
Payables	118.2	61.8
Payable to affiliates	7	9
Advances from affiliates	21	6.3
Other current liabilities	176.8	141.7
Total current liabilities	323	218.8
Long-term debt and capital lease obligation	1,486.9	1,954.4
Payable to affiliate - noncurrent	0	0
Advances from affiliates - noncurrent	466.3	212
Other noncurrent liabilities	183.9	178.9
Total other liabilities and deferred credits	650.2	390.9
Total partners’ capital	7,067.6	6,744.1
Total Liabilities and Partners' Capital	9,527.7	9,308.2
Eliminations
Assets
Cash and cash equivalents	0	0	$ 0	$ 0
Receivables	0	0
Receivables - affiliate	(7)	(9)
Gas and liquids stored underground	0	0
Prepayments	0	0
Advances to affiliates	(128.7)	(112.5)
Other current assets	(3.2)	(6.2)
Total current assets	(138.9)	(127.7)
Investment in consolidated subsidiaries	(9,221.1)	(8,714.7)
Property, plant and equipment, gross	0	0
Less—accumulated depreciation and amortization	0	0
Property, plant and equipment, net	0	0
Other noncurrent assets	0	(0.6)
Advances to affiliates – noncurrent	(3,769.9)	(3,356.8)
Total other assets	(3,769.9)	(3,357.4)
Total Assets	(13,129.9)	(12,199.8)
Liabilities and Partners' Capital
Payables	0	0
Payable to affiliates	(7)	(9)
Advances from affiliates	(128.7)	(112.5)
Other current liabilities	(3.2)	(6.5)
Total current liabilities	(138.9)	(128)
Long-term debt and capital lease obligation	0	0
Payable to affiliate - noncurrent	0	0
Advances from affiliates - noncurrent	(3,769.9)	(3,356.8)
Other noncurrent liabilities	0	(0.3)
Total other liabilities and deferred credits	(3,769.9)	(3,357.1)
Total partners’ capital	(9,221.1)	(8,714.7)
Total Liabilities and Partners' Capital	$ (13,129.9)	$ (12,199.8)

Guarantee of Securities of Su89

Guarantee of Securities of Subsidiaries Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Revenues:
Transportation									$ 1,091.1	$ 1,065.1	$ 1,028
Parking and lending									11.4	23.3	23.9
Storage									81.3	89.5	110.9
Other									65.4	55.9	42.8
Total operating revenues	$ 326.8	$ 294.1	$ 298.6	$ 329.7	$ 304.6	$ 278.9	$ 293.4	$ 356.9	1,249.2	1,233.8	1,205.6
Operating Costs and Expenses:
Fuel and transportation									99.3	124.7	97.2
Operation and maintenance									209.5	194.8	182.7
Administrative and general									130.4	125	117.4
Other operating costs and expenses									414.2	391.2	393.8
Total operating costs and expenses	220.4	213.4	212.7	206.9	224.1	210.4	196.9	204.3	853.4	835.7	791.1
Operating (loss) income	106.4	80.7	85.9	122.8	80.5	68.5	96.5	152.6	395.8	398.1	414.5
Other Deductions (Income):
Interest expense									176.4	165.5	163.4
Interest expense - affiliates									0	0	0
Interest income									(0.4)	(0.6)	(0.5)
Equity in earnings of subsidiaries									0	0	0
Equity losses in unconsolidated affiliates									0	86.5	1.2
Miscellaneous other income									(2.7)	(0.5)	(0.3)
Total other deductions									173.3	250.9	163.8
Income (loss) before income taxes	65.7	38.4	40.5	77.9	36.9	28.5	56	25.8	222.5	147.2	250.7
Income taxes	0.1	0.1	0.1	0.2	0	0.1	0.1	0.2	0.5	0.4	0.5
Net income (loss)	65.6	38.3	40.4	77.7	36.9	28.4	55.9	25.6	222	146.8	250.2
Net loss attributable to noncontrolling interests	0	0	0	0	0.1	(0.8)	(1.5)	(84.6)	0	(86.8)	(3.5)
Net income (loss) attributable to controlling interests	$ 65.6	$ 38.3	$ 40.4	$ 77.7	$ 36.8	$ 29.2	$ 57.4	$ 110.2	222	233.6	253.7
Reportable Legal Entities | Parent Guarantor
Operating Revenues:
Transportation									0	0	0
Parking and lending									0	0	0
Storage									0	0	0
Other									0	0	0
Total operating revenues									0	0	0
Operating Costs and Expenses:
Fuel and transportation									0	0	0
Operation and maintenance									0	0	0
Administrative and general									0	0.2	(0.1)
Other operating costs and expenses									0.3	0.2	0.3
Total operating costs and expenses									0.3	0.4	0.2
Operating (loss) income									(0.3)	(0.4)	(0.2)
Other Deductions (Income):
Interest expense									0	0	0
Interest Income - affiliates									(28.8)	(30)	(33.6)
Interest income									0	0	0
Equity in earnings of subsidiaries									(193.5)	(204)	(220.3)
Equity losses in unconsolidated affiliates										0	0
Miscellaneous other income									0	0	0
Total other deductions									(222.3)	(234)	(253.9)
Income (loss) before income taxes									222	233.6	253.7
Income taxes									0	0	0
Net income (loss)									222	233.6	253.7
Net loss attributable to noncontrolling interests										0	0
Net income (loss) attributable to controlling interests									222	233.6	253.7
Reportable Legal Entities | Subsidiary Issuer
Operating Revenues:
Transportation									0	0	0
Parking and lending									0	0	0
Storage									0	0	0
Other									0	0	0
Total operating revenues									0	0	0
Operating Costs and Expenses:
Fuel and transportation									0	0	0
Operation and maintenance									0	0	0.3
Administrative and general									0	0	0.8
Other operating costs and expenses									0	0	0.1
Total operating costs and expenses									0	0	1.2
Operating (loss) income									0	0	(1.2)
Other Deductions (Income):
Interest expense									104	76.5	72.7
Interest expense - affiliates									38.2	41.2	41.3
Interest income									0	0	0
Equity in earnings of subsidiaries									(335.7)	(321.7)	(335.5)
Equity losses in unconsolidated affiliates										0	0
Miscellaneous other income									0	0	0
Total other deductions									(193.5)	(204)	(221.5)
Income (loss) before income taxes									193.5	204	220.3
Income taxes									0	0	0
Net income (loss)									193.5	204	220.3
Net loss attributable to noncontrolling interests										0	0
Net income (loss) attributable to controlling interests									193.5	204	220.3
Reportable Legal Entities | Non-Guarantor Subsidiaries
Operating Revenues:
Transportation									1,178.5	1,157.9	1,116.4
Parking and lending									11.6	23.3	24
Storage									81.3	90.4	111
Other									65.4	55.9	42.8
Total operating revenues									1,336.8	1,327.5	1,294.2
Operating Costs and Expenses:
Fuel and transportation									186.9	218.4	185.8
Operation and maintenance									209.5	194.8	182.4
Administrative and general									130.4	124.8	116.7
Other operating costs and expenses									413.9	391	393.4
Total operating costs and expenses									940.7	929	878.3
Operating (loss) income									396.1	398.5	415.9
Other Deductions (Income):
Interest expense									72.4	89	90.7
Interest Income - affiliates									(9.4)	(11.2)	(7.7)
Interest income									(0.4)	(0.6)	(0.5)
Equity in earnings of subsidiaries									0	0	0
Equity losses in unconsolidated affiliates										86.5	1.2
Miscellaneous other income									(2.7)	(0.5)	(0.3)
Total other deductions									59.9	163.2	83.4
Income (loss) before income taxes									336.2	235.3	332.5
Income taxes									0.5	0.4	0.5
Net income (loss)									335.7	234.9	332
Net loss attributable to noncontrolling interests										(86.8)	(3.5)
Net income (loss) attributable to controlling interests									335.7	321.7	335.5
Eliminations
Operating Revenues:
Transportation									(87.4)	(92.8)	(88.4)
Parking and lending									(0.2)	0	(0.1)
Storage									0	(0.9)	(0.1)
Other									0	0	0
Total operating revenues									(87.6)	(93.7)	(88.6)
Operating Costs and Expenses:
Fuel and transportation									(87.6)	(93.7)	(88.6)
Operation and maintenance									0	0	0
Administrative and general									0	0	0
Other operating costs and expenses									0	0	0
Total operating costs and expenses									(87.6)	(93.7)	(88.6)
Operating (loss) income									0	0	0
Other Deductions (Income):
Interest expense									0	0	0
Interest expense - affiliates									0	0	0
Interest income									0	0	0
Equity in earnings of subsidiaries									529.2	525.7	555.8
Equity losses in unconsolidated affiliates										0	0
Miscellaneous other income									0	0	0
Total other deductions									529.2	525.7	555.8
Income (loss) before income taxes									(529.2)	(525.7)	(555.8)
Income taxes									0	0	0
Net income (loss)									(529.2)	(525.7)	(555.8)
Net loss attributable to noncontrolling interests										0	0
Net income (loss) attributable to controlling interests									$ (529.2)	$ (525.7)	$ (555.8)

Guarantee of Securities of Su90

Guarantee of Securities of Subsidiaries Statements of Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	$ 65.6	$ 38.3	$ 40.4	$ 77.7	$ 36.9	$ 28.4	$ 55.9	$ 25.6	$ 222	$ 146.8	$ 250.2
Other comprehensive income (loss):
(Loss) gain on cash flow hedges									0	(0.7)	1.6
Reclassification adjustment transferred to Net income from cash flow hedges									2.4	2.6	1.2
Pension and other postretirement benefit costs									(13.9)	(10.9)	0.7
Total Comprehensive Income (Loss)									210.5	137.8	253.7
Comprehensive loss attributable to noncontrolling interests									0	(86.8)	(3.5)
Comprehensive income (loss) attributable to controlling interests									210.5	224.6	257.2
Reportable Legal Entities | Parent Guarantor
Condensed Financial Statements, Captions [Line Items]
Net income (loss)									222	233.6	253.7
Other comprehensive income (loss):
(Loss) gain on cash flow hedges										(0.7)	1.6
Reclassification adjustment transferred to Net income from cash flow hedges									2.4	2.6	1.2
Pension and other postretirement benefit costs									(13.9)	(10.9)	0.7
Total Comprehensive Income (Loss)									210.5	224.6	257.2
Comprehensive loss attributable to noncontrolling interests									0	0	0
Comprehensive income (loss) attributable to controlling interests									210.5	224.6	257.2
Reportable Legal Entities | Subsidiary Issuer
Condensed Financial Statements, Captions [Line Items]
Net income (loss)									193.5	204	220.3
Other comprehensive income (loss):
(Loss) gain on cash flow hedges										(0.7)	1.6
Reclassification adjustment transferred to Net income from cash flow hedges									2.4	2.6	1.2
Pension and other postretirement benefit costs									(13.9)	(10.9)	0.7
Total Comprehensive Income (Loss)									182	195	223.8
Comprehensive loss attributable to noncontrolling interests									0	0	0
Comprehensive income (loss) attributable to controlling interests									182	195	223.8
Reportable Legal Entities | Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income (loss)									335.7	234.9	332
Other comprehensive income (loss):
(Loss) gain on cash flow hedges										(0.7)	1.6
Reclassification adjustment transferred to Net income from cash flow hedges									0.7	0.9	(0.5)
Pension and other postretirement benefit costs									(13.9)	(10.9)	0.7
Total Comprehensive Income (Loss)									322.5	224.2	333.8
Comprehensive loss attributable to noncontrolling interests									0	(86.8)	(3.5)
Comprehensive income (loss) attributable to controlling interests									322.5	311	337.3
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net income (loss)									(529.2)	(525.7)	(555.8)
Other comprehensive income (loss):
(Loss) gain on cash flow hedges										1.4	(3.2)
Reclassification adjustment transferred to Net income from cash flow hedges									(3.1)	(3.5)	(0.7)
Pension and other postretirement benefit costs									27.8	21.8	(1.4)
Total Comprehensive Income (Loss)									(504.5)	(506)	(561.1)
Comprehensive loss attributable to noncontrolling interests									0	0	0
Comprehensive income (loss) attributable to controlling interests									$ (504.5)	$ (506)	$ (561.1)

Guarantee of Securities of Su91

Guarantee of Securities of Subsidiaries Statements of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	$ 576.4	$ 513.6	$ 534.3
INVESTING ACTIVITIES:
Capital expenditures	(374.5)	(404.4)	(294.8)
Proceeds from sale of operating assets	0.8	2.9	60.7
Proceeds from insurance and other recoveries	6.2	6.3	1.4
Advances to affiliates, net	0	0.1	0
Investment in consolidated affiliates			0
Investment in unconsolidated affiliates	0	(20.5)	(76.7)
Distributions from unconsolidated affiliates	0	11.1	0
Acquisition of businesses, net of cash acquired		(294.7)
Net cash used in investing activities	(367.5)	(699.2)	(309.4)
FINANCING ACTIVITIES:
Proceeds from long-term debt, net of issuance cost	247.1	342.9	0
Repayment of borrowings from long-term debt and term loan	(725)	(25)	0
Proceeds from borrowings on revolving credit agreement	1,125	665	1,128
Repayment of borrowings on revolving credit agreement, including financing fees	(873.6)	(720)	(1,255)
Contribution from parent			0
Principal payment of capital lease obligation	(0.4)	(0.4)	(0.2)
Advances from affiliates, net	0.6	0.1	(2.8)
Distributions paid	(101.5)	(99.2)	(533.9)
Capital contributions from noncontrolling interests	0	8.2	87.1
Proceeds from sale of common units	113.1	0	368.7
Capital contributions from general partner	2.3	0	7.8
Distributions paid to noncontrolling interests	0	(7.9)	0
Net cash (used in) provided by financing activities	(212.4)	163.7	(200.3)
(Decrease) increase in cash and cash equivalents	(3.5)	(21.9)	24.6
Cash and cash equivalents at beginning of period	6.6	28.5	3.9
Cash and cash equivalents at end of period	3.1	6.6	28.5
Reportable Legal Entities | Parent Guarantor
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	27.9	30.2	33.9
INVESTING ACTIVITIES:
Capital expenditures	(1)	0	0
Proceeds from sale of operating assets	0	0	0
Proceeds from insurance and other recoveries	0	0	0
Advances to affiliates, net	(41.9)	363.9	126.4
Investment in consolidated affiliates			0
Investment in unconsolidated affiliates		0	0
Distributions from unconsolidated affiliates		0
Acquisition of businesses, net of cash acquired		(294.7)
Net cash used in investing activities	(42.9)	69.2	126.4
FINANCING ACTIVITIES:
Proceeds from long-term debt, net of issuance cost	0	0
Repayment of borrowings from long-term debt and term loan	0	0
Proceeds from borrowings on revolving credit agreement	0	0	0
Repayment of borrowings on revolving credit agreement, including financing fees	0	0	0
Contribution from parent			0
Principal payment of capital lease obligation	0	0	0
Advances from affiliates, net	0.6	0.1	(2.8)
Distributions paid	(101.5)	(99.2)	(533.9)
Capital contributions from noncontrolling interests		0	0
Proceeds from sale of common units	113.1		368.7
Capital contributions from general partner	2.3		7.8
Distributions paid to noncontrolling interests		0
Net cash (used in) provided by financing activities	14.5	(99.1)	(160.2)
(Decrease) increase in cash and cash equivalents	(0.5)	0.3	0.1
Cash and cash equivalents at beginning of period	0.5	0.2	0.1
Cash and cash equivalents at end of period	0	0.5	0.2
Reportable Legal Entities | Subsidiary Issuer
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	(136.3)	(112.1)	(108.8)
INVESTING ACTIVITIES:
Capital expenditures	0	0	0
Proceeds from sale of operating assets	0	0	0
Proceeds from insurance and other recoveries	0	0	0
Advances to affiliates, net	(269)	(49.6)	(84.3)
Investment in consolidated affiliates			(15.1)
Investment in unconsolidated affiliates		0	0
Distributions from unconsolidated affiliates		0
Acquisition of businesses, net of cash acquired		0
Net cash used in investing activities	(269)	(49.6)	(99.4)
FINANCING ACTIVITIES:
Proceeds from long-term debt, net of issuance cost	247.1	342.9
Repayment of borrowings from long-term debt and term loan	0	0
Proceeds from borrowings on revolving credit agreement	0	0	0
Repayment of borrowings on revolving credit agreement, including financing fees	(3.6)	0	0
Contribution from parent			0
Principal payment of capital lease obligation	0	0	0
Advances from affiliates, net	160.3	(188.6)	216.4
Distributions paid	0	0	0
Capital contributions from noncontrolling interests		0	0
Proceeds from sale of common units	0		0
Capital contributions from general partner	0		0
Distributions paid to noncontrolling interests		0
Net cash (used in) provided by financing activities	403.8	154.3	216.4
(Decrease) increase in cash and cash equivalents	(1.5)	(7.4)	8.2
Cash and cash equivalents at beginning of period	1.8	9.2	1
Cash and cash equivalents at end of period	0.3	1.8	9.2
Reportable Legal Entities | Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	684.8	595.5	609.2
INVESTING ACTIVITIES:
Capital expenditures	(373.5)	(404.4)	(294.8)
Proceeds from sale of operating assets	0.8	2.9	60.7
Proceeds from insurance and other recoveries	6.2	6.3	1.4
Advances to affiliates, net	(118.4)	(175.2)	(342.8)
Investment in consolidated affiliates			0
Investment in unconsolidated affiliates		(20.5)	(76.7)
Distributions from unconsolidated affiliates		11.1
Acquisition of businesses, net of cash acquired		0
Net cash used in investing activities	(484.9)	(579.8)	(652.2)
FINANCING ACTIVITIES:
Proceeds from long-term debt, net of issuance cost	0	0
Repayment of borrowings from long-term debt and term loan	(725)	(25)
Proceeds from borrowings on revolving credit agreement	1,125	665	1,128
Repayment of borrowings on revolving credit agreement, including financing fees	(870)	(720)	(1,255)
Contribution from parent			15.1
Principal payment of capital lease obligation	(0.4)	(0.4)	(0.2)
Advances from affiliates, net	269	49.6	84.3
Distributions paid	0	0	0
Capital contributions from noncontrolling interests		8.2	87.1
Proceeds from sale of common units	0		0
Capital contributions from general partner	0		0
Distributions paid to noncontrolling interests		(7.9)
Net cash (used in) provided by financing activities	(201.4)	(30.5)	59.3
(Decrease) increase in cash and cash equivalents	(1.5)	(14.8)	16.3
Cash and cash equivalents at beginning of period	4.3	19.1	2.8
Cash and cash equivalents at end of period	2.8	4.3	19.1
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	0	0	0
INVESTING ACTIVITIES:
Capital expenditures	0	0	0
Proceeds from sale of operating assets	0	0	0
Proceeds from insurance and other recoveries	0	0	0
Advances to affiliates, net	429.3	(139)	300.7
Investment in consolidated affiliates			15.1
Investment in unconsolidated affiliates		0	0
Distributions from unconsolidated affiliates		0
Acquisition of businesses, net of cash acquired		0
Net cash used in investing activities	429.3	(139)	315.8
FINANCING ACTIVITIES:
Proceeds from long-term debt, net of issuance cost	0	0
Repayment of borrowings from long-term debt and term loan	0	0
Proceeds from borrowings on revolving credit agreement	0	0	0
Repayment of borrowings on revolving credit agreement, including financing fees	0	0	0
Contribution from parent			(15.1)
Principal payment of capital lease obligation	0	0	0
Advances from affiliates, net	(429.3)	139	(300.7)
Distributions paid	0	0	0
Capital contributions from noncontrolling interests		0	0
Proceeds from sale of common units	0		0
Capital contributions from general partner	0		0
Distributions paid to noncontrolling interests		0
Net cash (used in) provided by financing activities	(429.3)	139	(315.8)
(Decrease) increase in cash and cash equivalents	0	0	0
Cash and cash equivalents at beginning of period	0	0	0
Cash and cash equivalents at end of period	$ 0	$ 0	$ 0