Revenues - Schedule of Disaggregation of Revenues (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Net asset optimization expense	$ (7,326)	$ (2,322)	$ (4,243)
Total revenues	435,192	460,493	393,485
Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	439,360	462,815	397,728
Other revenue
Disaggregation of Revenue [Line Items]
Revenues	3,158	0	0
POR | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	241,794	275,336	235,661
Non-POR | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	197,566	187,479	162,067
Unbilled revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	(8,764)	5,904	(6,589)
Commercial | Billed revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	100,467	95,943	74,769
Residential | Billed revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	347,657	360,968	329,548
New England | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	124,066	121,616	110,221
Mid-Atlantic | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	151,459	164,620	135,377
Midwest | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	49,931	62,094	62,576
Southwest | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	113,904	114,485	89,554
Retail Electricity | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	328,466	352,750	322,594
Retail Electricity | POR | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	191,355	212,374	195,120
Retail Electricity | Non-POR | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	137,111	140,376	127,474
Retail Electricity | Unbilled revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	(372)	808	(6,630)
Retail Electricity | Commercial | Billed revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	40,356	42,439	49,159
Retail Electricity | Residential | Billed revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	288,482	309,503	280,065
Retail Electricity | New England | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	115,129	111,332	100,819
Retail Electricity | Mid-Atlantic | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	111,599	114,994	107,307
Retail Electricity | Midwest | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	31,353	39,658	41,974
Retail Electricity | Southwest | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	70,385	86,766	72,494
Retail Natural Gas | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	110,894	110,065	75,134
Retail Natural Gas | POR | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	50,439	62,962	40,541
Retail Natural Gas | Non-POR | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	60,455	47,103	34,593
Retail Natural Gas | Unbilled revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	(8,392)	5,096	41
Retail Natural Gas | Commercial | Billed revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	60,111	53,504	25,610
Retail Natural Gas | Residential | Billed revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	59,175	51,465	49,483
Retail Natural Gas | New England | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	8,937	10,284	9,402
Retail Natural Gas | Mid-Atlantic | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	39,860	49,626	28,070
Retail Natural Gas | Midwest | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	18,578	22,436	20,602
Retail Natural Gas | Southwest | Retail revenues
Disaggregation of Revenue [Line Items]
Revenues	$ 43,519	$ 27,719	$ 17,060