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Weighted average period in years for which unrecognized compensation cost is expected to be recognized.

No definition available.

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Shares remaining available for future issuance under the ESPP, a noncompensatory plan.

No definition available.

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The first discounted purchase price at which employees are permitted to purchase NU common shares at six month intervals.

No definition available.

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The second discounted purchase price at which employees are permitted to purchase NU common shares at six month intervals.

No definition available.

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The number of equity-based payment instruments, excluding options, that validly exist and are outstanding as of the balance sheet date.

No definition available.

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The weighted average grant-date fair value of the number of shares newly issued during the reporting period under the plan.

No definition available.

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NU converted NSTAR Performance Shares and NSTAR Deferred Shares into NU RSU's as of the merger closing.

No definition available.

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Related weighted average grant date fair value of NSTAR Performance Shares and Deferred Shares that were converted to NU RSU's upon the merger closing.

No definition available.

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Upon the merger with NSTAR, NU converted NSTAR Deferred Shares and NSTAR Performance Shares to NU RSU's.

No definition available.

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Value of converted NSTAR Deferred and Performance Shares upon closing of the merger.

No definition available.

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Upon the merger with NSTAR, NU converted NSTAR RSU Retention Awards to NU RSU retention awards.

No definition available.

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Value of converted NSTAR RSU Retention Awards upon the closing of the merger.

No definition available.

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The weighted average fair value of awards on equity-based plans excluding option plans for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

No definition available.

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As of the balance sheet date, the number of shares into which expected to vest awards outstanding can be converted under the option plan.

No definition available.

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Upon the merger with NSTAR, outstanding NSTAR stock options converted into NU stock options

No definition available.

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Value of converted NSTAR options, upon the merger closing.

No definition available.

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Weighted Average Exercise Price of NSTAR Options Converted to NU Options during the period

No definition available.

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451,358 performance shares under the 2011 and 2012 Long-Term incentive programs converted to RSU's upon closing of the merger.

No definition available.

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451,358 performance shares under the 2011 and 2012 Long-Term incentive programs converted to RSU's upon closing of the merger.

No definition available.

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No authoritative reference available.

No definition available.

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

-Topic 718

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-Subparagraph (SAB TOPIC 14.F)

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 14

-Section F

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Aggregate carrying value as of the balance sheet date of the liabilities for deferred compensation arrangements payable after one year (or the normal operating cycle, if longer). Represents currently earned compensation under cash arrangements (such as a profit-sharing plan, rabbi trust, and employee contract--excluding equity-based arrangements) that is not actually paid until a later date.

No definition available.

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Aggregate proceeds received by the entity during the annual period from exercises of stock or unit options and conversion of similar instruments granted under equity-based payment arrangements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Unrecognized cost of unvested share-based compensation awards.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

-Topic 718

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Disclosure of the aggregate tax benefit realized from the exercise of stock options and the conversion of similar instruments during the annual period.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

-Topic 718

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

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-Paragraph 2

-Subparagraph (c)(2)(iii)(2)

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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-Paragraph 2

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

-Topic 718

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

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Number of share instruments newly issued under a share-based compensation plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

No definition available.

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Number of shares issued during the period as a result of an employee stock purchase plan.

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Number of share options (or share units) exercised during the current period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 2: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

-Topic 505

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-Subparagraph (SX 210.3-04)

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-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30

-Article 5

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