NSTAR ELECTRIC COMPANY AND SUBSIDIARY 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, 2020		342,954,023					200
Beginning balance at Dec. 31, 2020	$ 14,063,566	$ 1,789,092	$ 8,015,663	$ 4,613,201	$ (76,411)	$ 4,521,418	$ 0	$ 1,993,942	$ 2,527,167	$ 309
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (Loss)/Income	1,228,000					476,569			476,569
Dividends on Preferred Stock	(7,519)			(7,519)		(1,960)			(1,960)
Dividends on Common Stock	(828,337)			(828,337)		(283,200)			(283,200)
Capital Contributions from Eversource Parent						260,000		260,000
Other Comprehensive (Loss)/Income, Net of Tax						192				192
Ending balance (in shares) at Dec. 31, 2021		344,403,196					200
Ending balance at Dec. 31, 2021	14,599,844	$ 1,789,092	8,098,514	5,005,391	(42,275)	4,973,019	$ 0	2,253,942	2,718,576	501
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (Loss)/Income	1,412,400					492,428			492,428
Dividends on Preferred Stock	(7,519)			(7,519)		(1,960)			(1,960)
Dividends on Common Stock	(883,113)			(883,113)		(287,600)			(287,600)
Capital Contributions from Eversource Parent	210,000					525,000		525,000
Other Comprehensive (Loss)/Income, Net of Tax	$ 2,900					(217)				(217)
Ending balance (in shares) at Dec. 31, 2022	348,443,855	348,443,855					200
Ending 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 (Loss)/Income	(434,700)					544,528			544,528
Dividends on Preferred Stock	(7,519)			(7,519)		(1,960)			(1,960)
Dividends on Common Stock	(942,398)			(942,398)		(327,400)			(327,400)
Capital Contributions from Eversource Parent						234,900		234,900
Other Comprehensive (Loss)/Income, Net of Tax	$ 5,700					(240)				(240)
Ending balance (in shares) at Dec. 31, 2023	349,540,266	349,540,266					200
Ending 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