CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Revenues	$ 7,751,952	$ 7,639,129	$ 7,954,827
Operating Expenses:
Purchased Power, Fuel and Transmission	2,535,271	2,500,828	3,086,905
Operations and Maintenance	1,277,147	1,323,549	1,329,289
Depreciation	773,802	715,466	665,856
Amortization of Regulatory Assets, Net	89,986	71,696	22,339
Energy Efficiency Programs	480,835	533,659	495,701
Taxes Other Than Income Taxes	676,757	634,072	590,573
Total Operating Expenses	5,833,798	5,779,270	6,190,663
Operating Income	1,918,154	1,859,859	1,764,164
Interest Expense	421,755	400,961	372,420
Other Income, Net	78,008	45,920	34,227
Income Before Income Tax Expense	1,574,407	1,504,818	1,425,971
Income Tax Expense	578,892	554,997	539,967
Net Income	995,515	949,821	886,004
Net Income Attributable to Noncontrolling Interests	7,519	7,519	7,519
Net Income Attributable to Common Shareholders	$ 987,996	$ 942,302	$ 878,485
Basic Earnings Per Common Share (in dollars per share)	$ 3.11	$ 2.97	$ 2.77
Diluted Earnings Per Common Share (in dollars per share)	$ 3.11	$ 2.96	$ 2.76
Weighted Average Common Shares Outstanding:
Basic (in shares)	317,411,097	317,650,180	317,336,881
Diluted (in shares)	318,031,580	318,454,239	318,432,687
The Connecticut Light And Power Company
Operating Revenues	$ 2,887,359	$ 2,805,955	$ 2,802,675
Operating Expenses:
Purchased Power, Fuel and Transmission	930,780	919,723	1,054,313
Operations and Maintenance	500,358	490,069	487,281
Depreciation	249,352	230,489	215,289
Amortization of Regulatory Assets, Net	83,166	38,765	12,318
Energy Efficiency Programs	114,713	154,015	153,725
Taxes Other Than Income Taxes	323,887	299,719	268,688
Total Operating Expenses	2,202,256	2,132,780	2,191,614
Operating Income	685,103	673,175	611,061
Interest Expense	142,973	144,110	145,795
Other Income, Net	21,242	13,497	11,490
Income Before Income Tax Expense	563,372	542,562	476,756
Income Tax Expense	186,646	208,308	177,396
Net Income	376,726	334,254	299,360
NSTAR Electric Company
Operating Revenues	2,980,629	3,041,588	3,198,887
Operating Expenses:
Purchased Power, Fuel and Transmission	1,025,414	1,084,324	1,366,779
Operations and Maintenance	463,737	489,882	392,888
Depreciation	274,008	259,262	240,132
Amortization of Regulatory (Liabilities)/Assets, Net	33,831	34,332	1,556
Energy Efficiency Programs	294,053	321,787	267,622
Taxes Other Than Income Taxes	181,959	177,837	171,563
Total Operating Expenses	2,273,002	2,367,424	2,440,540
Operating Income	707,627	674,164	758,347
Interest Expense	105,729	108,428	100,139
Other Income, Net	14,913	10,830	7,854
Income Before Income Tax Expense	616,811	576,566	666,062
Income Tax Expense	242,085	225,789	265,014
Net Income	374,726	350,777	401,048
Public Service Company Of New Hampshire
Operating Revenues	981,624	959,482	972,203
Operating Expenses:
Purchased Power, Fuel and Transmission	237,478	210,786	247,721
Operations and Maintenance	257,185	260,779	276,554
Depreciation	128,192	116,519	105,372
Amortization of Regulatory (Liabilities)/Assets, Net	(16,577)	11,170	16,276
Energy Efficiency Programs	13,788	14,204	14,324
Taxes Other Than Income Taxes	89,760	82,964	81,779
Total Operating Expenses	709,826	696,422	742,026
Operating Income	271,798	263,060	230,177
Interest Expense	51,007	50,040	45,990
Other Income, Net	3,880	1,329	3,315
Income Before Income Tax Expense	224,671	214,349	187,502
Income Tax Expense	88,675	82,364	73,060
Net Income	$ 135,996	$ 131,985	$ 114,442