Maximum Ratio of Debt to EBITDA permitted under covenants for the previous twelve months.

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Maximum ratio of debt to EBITDA permitted under the covenants for the three quarters following an acquisition.

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No definition available.

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Maximum borrowing capacity under the Subordinated Loan Agreement without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the agreement.

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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No definition available.

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Amount of long-term debt before deduction of unamortized discount or premium. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, with initial maturities beyond one year or the normal operating cycle, if longer.

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States whether the entity was in compliance with the debt covenants throughout the reporting period, and describes facts and circumstances of any compliance failure.

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-SubTopic 470

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-Paragraph 3

-Subparagraph (g)

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The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

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No definition available.

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Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Maximum contractual interest rate for funds borrowed, under the debt agreement.

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Minimum contractual interest rate for funds borrowed, under the debt agreement.

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Date the debt instrument was issued, in CCYY-MM-DD format.

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Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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No definition available.

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Weighted average interest rate of debt outstanding.

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No definition available.

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

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No definition available.

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Identification of whether the entity has been in compliance with any credit facility debt covenants during the period.

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Description of the conditions for borrowing under the credit facility including the nature of any restrictions.

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Date the credit facility terminates, in CCYY-MM-DD format.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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- Definition

The cash outflow paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt.

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-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (e)

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The cash inflow from additional borrowings, net of cash paid to third parties in connection with debt origination.

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No definition available.

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The cash outflow to repay long-term debt that is not secured by collateral. Excludes repayments of tax exempt unsecured debt.

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-Glossary Financing Activities

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Terms and conditions of borrowings under subordinated debt agreements that qualify as available in computing net capital under SEC's uniform net capital rule, including restrictive covenants, collateral, and disclosure of the amount for which six months' notice has been given of intent to withdraw.

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No definition available.

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Financing - Debt (Details) - USD ($) $ in Millions					9 Months Ended
Financing - Debt (Details) - USD ($) $ in Millions	Jun. 01, 2015	Mar. 10, 2015	Feb. 02, 2015	Nov. 19, 2014	Sep. 30, 2015	Sep. 30, 2014	Nov. 02, 2015	Dec. 31, 2014
Debt Instruments [Abstract]
Repayments of Unsecured Debt					$ 725.0	$ 25.0
Unsecured Debt
Debt Instruments [Abstract]
Long-term Debt, Gross					$ 3,100.0			$ 3,400.0
Debt, Weighted Average Interest Rate					5.32%			5.31%
Debt Instrument, Covenant Compliance					The Partnership and its subsidiaries were in compliance with their debt covenants.
Subordinated Debt
Debt Instruments [Abstract]
Debt Instrument, Maturity Date					Jul. 31, 2024
Subordinated Loan Agreement Maximum Borrowing Capacity					$ 300.0
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum					5.75%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum					9.75%
Subordinated Borrowing Terms and Conditions					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.
Line of Credit
Debt Instruments [Abstract]
Debt, Weighted Average Interest Rate					1.44%			1.54%
Line of Credit Facility [Abstract]
Long-term Line of Credit					$ 365.0			$ 120.0
Covenant terms					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 the quarter of an acquisition.
Line of Credit Facility, Covenant Compliance					The Partnership and its subsidiaries were in compliance with all covenant requirements under the credit facility.
Maximum Ratio of Debt to EBITDA					5.0 to 1.0
Maximum Ratio of Debt to EBITDA after an Acquisition					5.5 to 1.0
Line of Credit \| Subsequent Event
Line of Credit Facility [Abstract]
Long-term Line of Credit							$ 350.0
Line of Credit Facility, Remaining Borrowing Capacity							$ 1,200.0
Boardwalk Pipelines 4.95% Notes Due 2024 \| Unsecured Debt
Debt Instruments [Abstract]
Debt Instrument, Issuance Date		Mar. 10, 2015		Nov. 19, 2014
Debt Instrument, Face Amount		$ 250.0		$ 350.0
Payments of Debt Issuance Costs		2.9
Proceeds from Debt, Net of Issuance Costs		$ 247.1
Debt Instrument, Interest Rate, Stated Percentage		4.95%		4.95%
Debt Instrument, Maturity Date		Dec. 15, 2024
Gulf South Notes Due 2015 \| Unsecured Debt
Debt Instruments [Abstract]
Debt Instrument, Interest Rate, Stated Percentage			5.05%
Repayments of Unsecured Debt			$ 275.0
Texas Gas Notes Due 2015 \| Unsecured Debt
Debt Instruments [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	4.60%
Repayments of Unsecured Debt	$ 250.0
Term Loan Boardwalk Acquisition Company \| Unsecured Debt
Debt Instruments [Abstract]
Long-term Debt, Gross					$ 0.0			$ 200.0
Debt, Weighted Average Interest Rate								1.91%
Debt Instrument, Maturity Date					Oct. 01, 2017
Amended Credit Agreement 2015 \| Base Rate
Line of Credit Facility [Abstract]
Debt Instrument, Description of Variable Rate Basis					base rate
Amended Credit Agreement 2015 \| Prime Rate
Line of Credit Facility [Abstract]
Debt Instrument, Description of Variable Rate Basis					prime rate
Amended Credit Agreement 2015 \| Federal Funds Effective Swap Rate
Line of Credit Facility [Abstract]
Debt Instrument, Description of Variable Rate Basis					federal funds
Amended Credit Agreement 2015 \| Eurodollar
Line of Credit Facility [Abstract]
Debt Instrument, Description of Variable Rate Basis					one month Eurodollar Rate
Amended Credit Agreement 2015 \| London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Abstract]
Debt Instrument, Description of Variable Rate Basis					LIBOR
Amended Credit Agreement 2015 \| Line of Credit
Line of Credit Facility [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity					$ 1,500.0
Line of Credit Facility, Expiration Date					May 26, 2020
Amended Credit Agreement 2015 \| Line of Credit \| Federal Funds Effective Swap Rate
Line of Credit Facility [Abstract]
Debt Instrument, Basis Spread on Variable Rate					0.50%
Amended Credit Agreement 2015 \| Line of Credit \| Eurodollar
Line of Credit Facility [Abstract]
Debt Instrument, Basis Spread on Variable Rate					1.00%
Amended Credit Agreement 2015 \| Line of Credit \| Minimum
Line of Credit Facility [Abstract]
Line of Credit Facility, Commitment Fee Percentage					0.10%
Amended Credit Agreement 2015 \| Line of Credit \| Minimum \| Base Rate
Line of Credit Facility [Abstract]
Debt Instrument, Basis Spread on Variable Rate					0.00%
Amended Credit Agreement 2015 \| Line of Credit \| Minimum \| London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Abstract]
Debt Instrument, Basis Spread on Variable Rate					1.00%
Amended Credit Agreement 2015 \| Line of Credit \| Maximum
Line of Credit Facility [Abstract]
Line of Credit Facility, Commitment Fee Percentage					0.275%
Amended Credit Agreement 2015 \| Line of Credit \| Maximum \| Base Rate
Line of Credit Facility [Abstract]
Debt Instrument, Basis Spread on Variable Rate					0.75%
Amended Credit Agreement 2015 \| Line of Credit \| Maximum \| London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Abstract]
Debt Instrument, Basis Spread on Variable Rate					1.75%