RELATED PARTY TRANSACTIONS (Other Agreements with MEP) (Details) - USD ($)	3 Months Ended
Mar. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Letters of Credit Outstanding, Amount	$ 199,800,000
Omnibus Agreement [Member] \| Minimum [Member]
Related Party Transaction [Line Items]
Other Commitment, Total	500,000	$ 500,000
Omnibus Agreement [Member] \| Maximum [Member]
Related Party Transaction [Line Items]
Other Commitment, Total	15,000,000
Omnibus Agreement [Member] \| Midcoast Energy Partners, L.P. [Member]
Related Party Transaction [Line Items]
Legal Fees	12,200,000
Financial Support Agreement [Member] \| Midcoast Energy Partners, L.P. [Member]
Related Party Transaction [Line Items]
Letters of Credit Outstanding, Amount	4,900,000	7,500,000
Guarantor Obligations, Current Carrying Value	$ 23,300,000	$ 21,700,000

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ Details

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- Definition

The amount of expense provided in the period for legal costs incurred on or before the balance sheet date pertaining to resolved, pending or threatened litigation, including arbitration and mediation proceedings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.3)
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

+ Details

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- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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- Definition

Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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