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 Income/(Loss)	NSTAR Electric	NSTAR Electric Common Stock	NSTAR Electric Capital Surplus, Paid In	NSTAR Electric Retained Earnings	NSTAR Electric Accumulated Other Comprehensive Income/(Loss)
Beginning balance (in shares) at Dec. 31, 2022		348,443,855					200
Balance as of Beginning of Period 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 (Loss)/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 Loss						(16)				(16)
Ending balance (in shares) at Mar. 31, 2023		348,808,082					200
Balance as of End of Period 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
Balance as of Beginning of Period 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 (Loss)/Income						433,267
Other Comprehensive Loss	15,400					(73)
Ending balance (in shares) at Sep. 30, 2023		349,275,775					200
Balance as of End of Period at Sep. 30, 2023	15,685,941	$ 1,799,920	8,443,820	5,666,861	(24,022)	5,928,594	$ 0	2,902,542	3,025,841	211
Beginning balance (in shares) at Mar. 31, 2023		348,808,082					200
Balance as of Beginning of Period 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 (Loss)/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 Loss						(27)				(27)
Ending balance (in shares) at Jun. 30, 2023		349,021,936					200
Balance as of End of Period 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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (Loss)/Income						164,711			164,711
Dividends on Preferred Stock	(1,880)			(1,880)		(490)			(490)
Dividends on Common Stock	(235,691)			(235,691)
Capital Contributions from Eversource Parent						11,300		11,300
Other Comprehensive Loss						(30)				(30)
Ending balance (in shares) at Sep. 30, 2023		349,275,775					200
Balance as of End of Period at Sep. 30, 2023	$ 15,685,941	$ 1,799,920	8,443,820	5,666,861	(24,022)	5,928,594	$ 0	2,902,542	3,025,841	211
Beginning balance (in shares) at Dec. 31, 2023	349,540,266	349,540,266					200
Balance as of Beginning of Period 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 (Loss)/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 Loss						(16)				(16)
Ending balance (in shares) at Mar. 31, 2024		351,379,414					200
Balance as of End of Period 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
Balance as of Beginning of Period 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 (Loss)/Income						502,129
Other Comprehensive Loss	$ 5,500					(52)
Ending balance (in shares) at Sep. 30, 2024	363,891,973	363,891,973					200
Balance as of End of Period at Sep. 30, 2024	$ 15,044,424	$ 1,866,385	9,263,434	4,118,654	(28,205)	6,382,205	$ 0	3,388,842	2,993,371	(8)
Beginning balance (in shares) at Mar. 31, 2024		351,379,414					200
Balance as of Beginning of Period 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 (Loss)/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 Loss						(18)				(18)
Ending balance (in shares) at Jun. 30, 2024		354,566,071					200
Balance as of End of Period 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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (Loss)/Income						184,549			184,549
Dividends on Preferred Stock	(1,880)			(1,880)		(490)			(490)
Dividends on Common Stock	$ (260,119)			(260,119)		(250,000)			(250,000)
Capital Contributions from Eversource Parent						75,000		75,000
Other Comprehensive Loss						(18)				(18)
Ending balance (in shares) at Sep. 30, 2024	363,891,973	363,891,973					200
Balance as of End of Period at Sep. 30, 2024	$ 15,044,424	$ 1,866,385	$ 9,263,434	$ 4,118,654	$ (28,205)	$ 6,382,205	$ 0	$ 3,388,842	$ 2,993,371	$ (8)