PSNH GENERATION ASSET SALE - Narrative (Details) - Electricity Generation Plant, Non-Nuclear [Member] - Public Service Company Of New Hampshire [Member] $ in Millions		9 Months Ended
Jun. 10, 2015 USD ($) senator	Sep. 30, 2015 USD ($)
Regulatory Assets [Line Items]
Number of state senators \| senator	2
Payments for restructuring \| $	$ 5	$ 5

Amount of cash payments made as the result of exit or disposal activities. Excludes payments associated with a discontinued operation or an asset retirement obligation.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

Name:	us-gaap_PaymentsForRestructuring
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration