CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Revenues	$ 8,904,430	$ 8,526,470	$ 8,448,201
Operating Expenses:
Purchased Power and Transmission	2,987,840	3,040,160	3,138,969
Operations and Maintenance	1,480,252	1,363,113	1,335,213
Depreciation	981,380	885,278	819,930
Amortization of Regulatory Assets, Net	177,679	195,380	252,026
Energy Efficiency Programs	535,760	501,369	472,380
Taxes Other Than Income Taxes	752,785	711,035	729,753
Impairment of Northern Pass Transmission	0	239,644	0
Total Operating Expenses	6,915,696	6,935,979	6,748,271
Operating Income	1,988,734	1,590,491	1,699,930
Interest Expense	538,452	533,197	498,805
Other Income, Net	108,590	132,777	128,366
Income Before Income Tax Expense	1,558,872	1,190,071	1,329,491
Income Tax Expense	346,186	273,499	288,972
Net Income	1,212,686	916,572	1,040,519
Net Income Attributable to Noncontrolling Interests	7,519	7,519	7,519
Net Income Attributable to Common Shareholders	$ 1,205,167	$ 909,053	$ 1,033,000
Basic Earnings Per Common Share (in dollars per share)	$ 3.56	$ 2.83	$ 3.25
Diluted Earnings Per Common Share (in dollars per share)	$ 3.55	$ 2.81	$ 3.25
Weighted Average Common Shares Outstanding:
Basic (in shares)	338,836,147	321,416,086	317,370,369
Diluted (in shares)	339,847,062	322,941,636	317,993,934
The Connecticut Light and Power Company
Operating Revenues	$ 3,547,527	$ 3,232,551	$ 3,096,174
Operating Expenses:
Purchased Power and Transmission	1,369,196	1,188,202	1,095,187
Operations and Maintenance	572,897	549,167	506,448
Depreciation	320,709	301,188	278,557
Amortization of Regulatory Assets, Net	58,412	51,621	129,021
Energy Efficiency Programs	141,453	118,235	93,977
Taxes Other Than Income Taxes	344,451	342,489	357,147
Total Operating Expenses	2,807,118	2,550,902	2,460,337
Operating Income	740,409	681,649	635,837
Interest Expense	153,547	151,357	151,727
Other Income, Net	20,774	17,531	22,663
Income Before Income Tax Expense	607,636	547,823	506,773
Income Tax Expense	149,702	136,971	129,056
Net Income	457,934	410,852	377,717
NSTAR Electric Company
Operating Revenues	2,941,148	3,044,642	3,112,926
Operating Expenses:
Purchased Power and Transmission	879,244	1,064,289	1,257,073
Operations and Maintenance	534,118	468,436	462,100
Depreciation	319,468	296,500	276,372
Amortization of Regulatory Assets, Net	83,248	103,735	46,654
Energy Efficiency Programs	263,986	289,206	292,288
Taxes Other Than Income Taxes	206,764	195,586	194,316
Total Operating Expenses	2,286,828	2,417,752	2,528,803
Operating Income	654,320	626,890	584,123
Interest Expense	130,508	114,198	105,193
Other Income, Net	52,017	44,577	53,066
Income Before Income Tax Expense	575,829	557,269	531,996
Income Tax Expense	130,828	125,313	148,906
Net Income	445,001	431,956	383,090
Public Service Company of New Hampshire
Operating Revenues	1,079,095	1,065,936	1,047,619
Operating Expenses:
Purchased Power and Transmission	364,067	398,449	370,246
Operations and Maintenance	219,325	210,995	210,541
Depreciation	100,372	93,737	92,055
Amortization of Regulatory Assets, Net	52,804	57,732	80,978
Energy Efficiency Programs	37,583	25,982	20,105
Taxes Other Than Income Taxes	81,611	62,574	77,280
Total Operating Expenses	855,762	849,469	851,205
Operating Income	223,333	216,467	196,414
Interest Expense	58,127	60,666	60,634
Other Income, Net	13,786	19,222	27,672
Income Before Income Tax Expense	178,992	175,023	163,452
Income Tax Expense	31,680	40,975	47,576
Net Income	$ 147,312	$ 134,048	$ 115,876