CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Revenues	$ 8,526,470	$ 8,448,201	$ 7,751,952
Operating Expenses:
Purchased Power, Fuel and Transmission	3,040,160	3,138,969	2,535,271
Operations and Maintenance	1,363,113	1,335,213	1,307,052
Depreciation	885,278	819,930	773,802
Amortization of Regulatory Assets/(Liabilities), Net	195,380	252,026	89,986
Energy Efficiency Programs	501,369	472,380	480,835
Taxes Other Than Income Taxes	711,035	729,753	676,757
Impairment of Northern Pass Transmission	239,644	0	0
Total Operating Expenses	6,935,979	6,748,271	5,863,703
Operating Income	1,590,491	1,699,930	1,888,249
Interest Expense	533,197	498,805	421,755
Other Income, Net	132,777	128,366	107,913
Income Before Income Tax Expense	1,190,071	1,329,491	1,574,407
Income Tax Expense	273,499	288,972	578,892
Net Income	916,572	1,040,519	995,515
Net Income Attributable to Noncontrolling Interests	7,519	7,519	7,519
Net Income Attributable to Common Shareholders	$ 909,053	$ 1,033,000	$ 987,996
Basic Earnings Per Common Share (in dollars per share)	$ 2.83	$ 3.25	$ 3.11
Diluted Earnings Per Common Share (in dollars per share)	$ 2.81	$ 3.25	$ 3.11
Weighted Average Common Shares Outstanding:
Basic (in shares)	321,416,086	317,370,369	317,411,097
Diluted (in shares)	322,941,636	317,993,934	318,031,580
The Connecticut Light and Power Company
Operating Revenues	$ 3,232,551	$ 3,096,174	$ 2,887,359
Operating Expenses:
Purchased Power, Fuel and Transmission	1,188,202	1,095,187	930,780
Operations and Maintenance	549,167	506,448	502,107
Depreciation	301,188	278,557	249,352
Amortization of Regulatory Assets/(Liabilities), Net	51,621	129,021	83,166
Energy Efficiency Programs	118,235	93,977	114,713
Taxes Other Than Income Taxes	342,489	357,147	323,887
Total Operating Expenses	2,550,902	2,460,337	2,204,005
Operating Income	681,649	635,837	683,354
Interest Expense	151,357	151,727	142,973
Other Income, Net	17,531	22,663	22,991
Income Before Income Tax Expense	547,823	506,773	563,372
Income Tax Expense	136,971	129,056	186,646
Net Income	410,852	377,717	376,726
NSTAR Electric Company
Operating Revenues	3,044,642	3,112,926	2,980,629
Operating Expenses:
Purchased Power, Fuel and Transmission	1,064,289	1,257,073	1,025,414
Operations and Maintenance	468,436	462,100	482,924
Depreciation	296,500	276,372	274,008
Amortization of Regulatory Assets/(Liabilities), Net	103,735	46,654	33,831
Energy Efficiency Programs	289,206	292,288	294,053
Taxes Other Than Income Taxes	195,586	194,316	181,959
Total Operating Expenses	2,417,752	2,528,803	2,292,189
Operating Income	626,890	584,123	688,440
Interest Expense	114,198	105,193	105,729
Other Income, Net	44,577	53,066	34,100
Income Before Income Tax Expense	557,269	531,996	616,811
Income Tax Expense	125,313	148,906	242,085
Net Income	431,956	383,090	374,726
Public Service Company of New Hampshire
Operating Revenues	1,065,936	1,047,619	981,624
Operating Expenses:
Purchased Power, Fuel and Transmission	398,449	370,246	237,478
Operations and Maintenance	210,995	210,541	263,110
Depreciation	93,737	92,055	128,192
Amortization of Regulatory Assets/(Liabilities), Net	57,732	80,978	(16,577)
Energy Efficiency Programs	25,982	20,105	13,788
Taxes Other Than Income Taxes	62,574	77,280	89,760
Total Operating Expenses	849,469	851,205	715,751
Operating Income	216,467	196,414	265,873
Interest Expense	60,666	60,634	51,007
Other Income, Net	19,222	27,672	9,805
Income Before Income Tax Expense	175,023	163,452	224,671
Income Tax Expense	40,975	47,576	88,675
Net Income	$ 134,048	$ 115,876	$ 135,996