Revenues - Disaggregation of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Disaggregation of Revenue [Line Items]
Net asset optimization expense	$ (1,597)	$ (3,273)
Total Revenues	114,056	131,852
Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	114,388	135,125
Other revenue
Disaggregation of Revenue [Line Items]
Retail revenues	1,265	0
POR | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	69,758	74,197
Non-POR | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	44,630	60,928
Unbilled revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	(7,280)	(12,359)
Commercial | Billed Revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	32,079	38,972
Residential | Billed Revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	89,589	108,512
New England | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	31,964	36,800
Mid-Atlantic | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	45,954	46,855
Midwest | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	14,680	17,944
Southwest | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	21,790	33,526
Retail Electricity | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	77,329	82,827
Retail Electricity | POR | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	50,289	49,143
Retail Electricity | Non-POR | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	27,040	33,684
Retail Electricity | Unbilled revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	(4,984)	(4,703)
Retail Electricity | Commercial | Billed Revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	11,365	10,293
Retail Electricity | Residential | Billed Revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	70,948	77,237
Retail Electricity | New England | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	27,339	32,887
Retail Electricity | Mid-Atlantic | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	30,699	27,509
Retail Electricity | Midwest | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	7,309	8,139
Retail Electricity | Southwest | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	11,982	14,292
Retail Natural Gas | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	37,059	52,298
Retail Natural Gas | POR | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	19,469	25,054
Retail Natural Gas | Non-POR | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	17,590	27,244
Retail Natural Gas | Unbilled revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	(2,296)	(7,656)
Retail Natural Gas | Commercial | Billed Revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	20,714	28,679
Retail Natural Gas | Residential | Billed Revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	18,641	31,275
Retail Natural Gas | New England | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	4,625	3,913
Retail Natural Gas | Mid-Atlantic | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	15,255	19,346
Retail Natural Gas | Midwest | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	7,371	9,805
Retail Natural Gas | Southwest | Retail revenues
Disaggregation of Revenue [Line Items]
Retail revenues	$ 9,808	$ 19,234