NSTAR ELECTRIC COMPANY AND SUBSIDIARY CONDENSED CONSOLIDATED STATEMENTS OF COMMON STOCKHOLDER'S EQUITY - USD ($) $ in Thousands	Total	Common Stock	Capital Surplus, Paid In	Retained Earnings	Accumulated Other Comprehensive Loss	NSTAR Electric	NSTAR Electric Common Stock	NSTAR Electric Capital Surplus, Paid In	NSTAR Electric Retained Earnings	NSTAR Electric Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Dec. 31, 2022		348,443,855					200
Beginning balance at Dec. 31, 2022	$ 15,473,158	$ 1,799,920	$ 8,401,731	$ 5,527,153	$ (39,421)	$ 5,700,670	$ 0	$ 2,778,942	$ 2,921,444	$ 284
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income						133,813			133,813
Dividends on Preferred Stock	(1,880)			(1,880)		(490)			(490)
Dividends on Common Stock	(235,354)			(235,354)		(327,400)			(327,400)
Capital Contributions from Eversource Parent						31,300		31,300
Other Comprehensive Income (Loss)						(16)				(16)
Ending balance (in shares) at Mar. 31, 2023		348,808,082					200
Ending balance at Mar. 31, 2023	15,749,371	$ 1,799,920	8,412,085	5,782,958	(36,191)	5,537,877	$ 0	2,810,242	2,727,367	268
Beginning balance (in shares) at Dec. 31, 2022		348,443,855					200
Beginning balance at Dec. 31, 2022	15,473,158	$ 1,799,920	8,401,731	5,527,153	(39,421)	5,700,670	$ 0	2,778,942	2,921,444	284
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income						268,556
Other Comprehensive Income (Loss)						(43)
Ending balance (in shares) at Jun. 30, 2023		349,021,936					200
Ending balance at Jun. 30, 2023	15,554,098	$ 1,799,920	8,428,786	5,562,889	(32,103)	5,753,103	$ 0	2,891,242	2,861,620	241
Beginning balance (in shares) at Mar. 31, 2023		348,808,082					200
Beginning balance at Mar. 31, 2023	15,749,371	$ 1,799,920	8,412,085	5,782,958	(36,191)	5,537,877	$ 0	2,810,242	2,727,367	268
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income						134,743			134,743
Dividends on Preferred Stock	(1,880)			(1,880)		(490)			(490)
Dividends on Common Stock	(235,491)			(235,491)
Capital Contributions from Eversource Parent						81,000		81,000
Other Comprehensive Income (Loss)						(27)				(27)
Ending balance (in shares) at Jun. 30, 2023		349,021,936					200
Ending balance at Jun. 30, 2023	$ 15,554,098	$ 1,799,920	8,428,786	5,562,889	(32,103)	5,753,103	$ 0	2,891,242	2,861,620	241
Beginning balance (in shares) at Dec. 31, 2023	349,540,266	349,540,266					200
Beginning balance at Dec. 31, 2023	$ 14,173,892	$ 1,799,920	8,460,876	4,142,515	(33,737)	6,150,498	$ 0	3,013,842	3,136,612	44
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income						159,977			159,977
Dividends on Preferred Stock	(1,880)			(1,880)		(490)			(490)
Dividends on Common Stock	(250,770)			(250,770)		(96,700)			(96,700)
Capital Contributions from Eversource Parent						300,000		300,000
Other Comprehensive Income (Loss)						(16)				(16)
Ending balance (in shares) at Mar. 31, 2024		351,379,414					200
Ending balance at Mar. 31, 2024	$ 14,543,588	$ 1,806,385	8,537,591	4,413,593	(28,534)	6,513,269	$ 0	3,313,842	3,199,399	28
Beginning balance (in shares) at Dec. 31, 2023	349,540,266	349,540,266					200
Beginning balance at Dec. 31, 2023	$ 14,173,892	$ 1,799,920	8,460,876	4,142,515	(33,737)	6,150,498	$ 0	3,013,842	3,136,612	44
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income						317,580
Other Comprehensive Income (Loss)						(34)
Ending balance (in shares) at Jun. 30, 2024	354,566,071	354,566,071					200
Ending balance at Jun. 30, 2024	$ 14,818,713	$ 1,820,954	8,710,844	4,496,830	(29,581)	6,373,164	$ 0	3,313,842	3,059,312	10
Beginning balance (in shares) at Mar. 31, 2024		351,379,414					200
Beginning balance at Mar. 31, 2024	14,543,588	$ 1,806,385	8,537,591	4,413,593	(28,534)	6,513,269	$ 0	3,313,842	3,199,399	28
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income						157,603			157,603
Dividends on Preferred Stock	(1,880)			(1,880)		(490)			(490)
Dividends on Common Stock	$ (252,104)			(252,104)		(297,200)			(297,200)
Other Comprehensive Income (Loss)						(18)				(18)
Ending balance (in shares) at Jun. 30, 2024	354,566,071	354,566,071					200
Ending balance at Jun. 30, 2024	$ 14,818,713	$ 1,820,954	$ 8,710,844	$ 4,496,830	$ (29,581)	$ 6,373,164	$ 0	$ 3,313,842	$ 3,059,312	$ 10