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OTHER ITEMS AND CHARGES - Narrative (Detail) - USD ($) $ in Thousands	8 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Apr. 30, 2014
Unusual or Infrequent Item [Line Items]
Environmental remediation charge	$ 950	$ 900	$ 0	$ 400
Legal costs for the acquisition	0	0	0	144
Development project charge	0	0	0	1,394
Severance and reorganization charge	$ 0	$ 0	$ 0	586
Maine Energy Facility
Unusual or Infrequent Item [Line Items]
Development project charge				$ 1,394
Tompkins
Unusual or Infrequent Item [Line Items]
Equity method investment membership interest				50.00%

X

- Definition

The aggregate amount of significant divestiture and acquisition expenses, along with certain financing costs, recognized during an accounting period that are not disclosed separately. Generally, these items are either unusual or infrequent, but not both.

+ References

No definition available.

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- Definition

Percentage of voting equity interests acquired at the acquisition date in the business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
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- Definition

The charge against earnings in the period for known or estimated future costs arising from requirements to perform environmental remediation activities.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 30
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- Definition

The expense charged against earnings to eliminate the capitalized costs of projects that have been terminated during the reporting period, which is added back to net income when calculating cash provided by (used in) operations using the indirect method.

+ References

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- Definition

Amount of expenses for special or contractual termination benefits provided to current employees involuntarily terminated under a benefit arrangement associated exit or disposal activities pursuant to an authorized plan. Excludes expenses related to one-time termination benefits, a discontinued operation or an asset retirement obligation.

+ References

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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

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