Segment Reporting - Financial Data for Business Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Total Revenues	$ 393,485	$ 554,890	$ 813,725
Retail cost of revenues	323,219	344,592	615,225
Less:
Net asset optimization revenue	(4,243)	(657)	2,771
Net, gain on non-trading derivative instruments	21,200	(23,386)	(67,749)
Current period settlements on non-trading derivatives	(15,692)	37,729	42,820
Retail gross margin	132,534	196,473	220,740
Total Assets	355,276	366,667	422,968
Goodwill	120,343	120,343	120,343	$ 120,343
Unusual or Infrequent Item, or Both, Net (Gain) Loss	(64,403)	0	0
Non-trading
Less:
Net, gain on non-trading derivative instruments	22,130	(23,439)	(67,955)
Current period settlements on non-trading derivatives	(15,752)	37,921	42,944
Operating Segments | Retail Electricity
Segment Reporting Information [Line Items]
Total Revenues	322,594	461,393	688,451
Retail cost of revenues	284,794	306,012	552,250
Less:
Net asset optimization revenue	0	0	0
Retail gross margin	96,009	143,233	160,540
Total Assets	1,527,456	2,906,139	2,524,884
Goodwill	117,813,000	117,813	117,813
Unusual or Infrequent Item, or Both, Net (Gain) Loss	(64,403)
Operating Segments | Retail Electricity | Non-trading
Less:
Net, gain on non-trading derivative instruments	19,070	(23,242)	(66,180)
Current period settlements on non-trading derivatives	(12,876)	35,390	41,841
Operating Segments | Retail Natural Gas
Segment Reporting Information [Line Items]
Total Revenues	75,134	94,154	122,503
Retail cost of revenues	38,425	38,580	62,975
Less:
Net asset optimization revenue	0	0	0
Retail gross margin	36,525	53,240	60,200
Total Assets	7,320	941,569	820,601
Goodwill	2,530	2,530	2,530
Unusual or Infrequent Item, or Both, Net (Gain) Loss	0
Operating Segments | Retail Natural Gas | Non-trading
Less:
Net, gain on non-trading derivative instruments	3,060	(197)	(1,775)
Current period settlements on non-trading derivatives	(2,876)	2,531	1,103
Corporate and Other
Segment Reporting Information [Line Items]
Total Revenues	(4,243)	(657)	2,771
Retail cost of revenues	0	0	0
Less:
Net asset optimization revenue	(4,243)	(657)	2,771
Retail gross margin	0	0	0
Total Assets	311,556	318,865	341,411
Goodwill	0	0	0
Unusual or Infrequent Item, or Both, Net (Gain) Loss	0
Corporate and Other | Non-trading
Less:
Net, gain on non-trading derivative instruments	0	0	0
Current period settlements on non-trading derivatives	0	0	0
Eliminations
Segment Reporting Information [Line Items]
Total Revenues	0	0	0
Retail cost of revenues	0	0	0
Less:
Net asset optimization revenue	0	0	0
Retail gross margin	0	0	0
Total Assets	(1,491,056)	(3,799,906)	(3,263,928)
Goodwill	0	0	0
Unusual or Infrequent Item, or Both, Net (Gain) Loss	0
Eliminations | Non-trading
Less:
Net, gain on non-trading derivative instruments	0	0	0
Current period settlements on non-trading derivatives	$ 0	$ 0	$ 0