EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended	3 Months Ended	9 Months Ended
Apr. 09, 2012	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Earnings Per Share Basic And Diluted [Line Items]
Net Income Attributable to Controlling Interests		$ 207,628	$ 89,961	$ 351,229	$ 281,394
Basic		314,806,441	177,497,862	264,636,636	177,344,481
Weighted Average Number Diluted Shares Outstanding Adjustment		999,355	337,486	716,741	303,213
Diluted		315,805,796	177,835,348	265,353,377	177,647,694
Earnings Per Share, Basic and Diluted [Abstract]
Basic Earnings Per Common Share		$ 0.66	$ 0.51	$ 1.33	$ 1.59
Diluted Earnings Per Common Share		$ 0.66	$ 0.51	$ 1.32	$ 1.58
Common Stock Issuance, Merger with NSTAR [Abstract]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares	136,049,000
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount				5,688

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period).

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