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	NSTAR Electric	NSTAR Electric Common Stock	NSTAR Electric Capital Surplus, Paid In	NSTAR Electric Retained Earnings	NSTAR Electric Accumulated Other Comprehensive Income
Beginning balance (in shares) at Dec. 31, 2024		366,608,052					200
Beginning balance at Dec. 31, 2024	$ 15,039,387	$ 1,878,622	$ 9,428,905	$ 3,929,141	$ (26,472)	$ 6,915,806	$ 0	$ 3,788,842	$ 3,127,105	$ (141)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income						167,175			167,175
Dividends on Preferred Stock	(1,880)			(1,880)		(490)			(490)
Dividends on Common Stock	(276,229)			(276,229)		(436,000)			(436,000)
Capital Contributions from Eversource Parent						100,000		100,000
Other Comprehensive Loss						(2)				(2)
Ending balance (in shares) at Mar. 31, 2025		367,307,083					200
Ending balance at Mar. 31, 2025	$ 15,341,257	$ 1,878,622	9,440,596	4,203,700	(23,949)	6,746,489	$ 0	3,888,842	2,857,790	(143)
Beginning balance (in shares) at Dec. 31, 2025	375,416,880	375,416,880					200
Beginning balance at Dec. 31, 2025	$ 16,197,271	$ 1,914,273	9,937,878	4,504,983	(20,507)	7,558,835	$ 0	4,238,842	3,319,768	225
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income						165,950			165,950
Dividends on Preferred Stock	(1,880)			(1,880)		(490)			(490)
Dividends on Common Stock	$ (295,978)			(295,978)
Capital Contributions from Eversource Parent						258,000		258,000
Other Comprehensive Loss						(27)				(27)
Ending balance (in shares) at Mar. 31, 2026	375,974,644	375,974,644					200
Ending balance at Mar. 31, 2026	$ 16,530,950	$ 1,914,273	$ 9,950,113	$ 4,815,846	$ (20,377)	$ 7,982,268	$ 0	$ 4,496,842	$ 3,485,228	$ 198