Estimate of possible loss for each 10 basis point change to base ROE

No definition available.

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- Definition

Loss Contingency, Percentage of Base ROE Challenged by Complainants

+ References

No definition available.

+ Details

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- Definition

Loss Contingency, Basis Spread

+ References

No definition available.

+ Details

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- Definition

Loss Contingency, Maximum percentage of ROE for incentive projects

+ References

No definition available.

+ Details

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- Definition

Loss Contingency, Period of Complaint

+ References

No definition available.

+ Details

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- Definition

Percentage of Base ROE of Complaint Period

+ References

No definition available.

+ Details

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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.

+ Details

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Period Type:	duration

- Definition

Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349

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- Details

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COMMITMENTS AND CONTINGENCIES - FERC ROE Complaints (Details) - USD ($) $ in Millions			3 Months Ended	15 Months Ended
	Apr. 14, 2017	Apr. 29, 2016	Mar. 31, 2017	Mar. 26, 2014
FERC ROE First, Second and Third Complaints [Member]
Loss Contingencies [Line Items]
Base ROE percentage challenged by complainants			11.14%
FERC ROE Complaints [Member]
Loss Contingencies [Line Items]
Period of complaint			15 months
Basis point change			10.00%
Estimate of possible loss for each 10 basis point change to base ROE			$ 3.0
FERC ROE Fourth Complaint [Member]
Loss Contingencies [Line Items]
Base ROE percentage of complaint period		10.57%
Maximum percentage cap of ROE for incentive projects		11.74%
Loss contingency, estimate of possible earnings impact			0.0
FERC ROE First Complaint [Member]
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact			0.0
FERC ROE Second Complaint [Member]
Loss Contingencies [Line Items]
Base ROE percentage of complaint period				10.57%
Loss contingency, estimate of possible earnings impact			39.1
The Connecticut Light And Power Company [Member] \| FERC ROE Second Complaint [Member]
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact			21.4
NSTAR Electric Company [Member] \| FERC ROE Second Complaint [Member]
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact			8.5
Public Service Company Of New Hampshire [Member] \| FERC ROE Second Complaint [Member]
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact			3.1
Western Massachusetts Electric Company [Member] \| FERC ROE Second Complaint [Member]
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact			$ 6.1
Subsequent Event [Member] \| FERC ROE First Complaint [Member]
Loss Contingencies [Line Items]
Base ROE percentage challenged by complainants	11.14%