Discontinued Operations - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019
Disposal Group, Including Discontinued Operation, Classified Balance Sheet Disclosures [Abstract]
Discontinued operations - total assets	$ 16,900	$ 14,600	$ 16,900	$ 14,600		$ 15,100
Discontinued Operation, Income Statement Disclosures [Abstract]
Loss from discontinued operations, net of tax	$ 765	$ (795)	$ 267	$ (1,968)
Loss from discontinued operations per share of common stock
Basic (in dollars per share)	$ 0.02	$ (0.02)	$ 0.01	$ (0.07)
Diluted (in dollars per share)	$ 0.02	$ (0.02)	$ 0.01	$ (0.07)
Gill Ranch [Member] | Discontinued Operations, Held-for-sale or Disposed of by Sale [Member]
Disposal Group, Including Discontinued Operation, Classified Balance Sheet Disclosures [Abstract]
Accounts receivable	$ 1,106	$ 907	$ 1,106	$ 907		333
Inventories	730	712	730	712		695
Other current assets	64	45	64	45		457
Property, plant, and equipment	14,663	12,583	14,663	12,583		13,284
Operating lease right of use asset	118	118	118	118		118
Other non-current assets	247	247	247	247		247
Discontinued operations - total assets	16,928	14,612	16,928	14,612		15,134
Accounts payable	1,747	1,375	1,747	1,375		1,250
Other current liabilities	796	342	796	342		848
Operating lease liabilities	113	114	113	114		116
Other non-current liabilities	11,266	11,568	11,266	11,568		11,495
Total discontinued operations liabilities	13,922	13,399	13,922	13,399		$ 13,709
Gill Ranch [Member] | Discontinued Operations, Held-for-sale [Member]
Discontinued Operation, Income Statement Disclosures [Abstract]
Revenues	3,584	1,410	7,866	4,879
Operations and maintenance	2,148	2,113	6,332	6,377
General taxes	61	40	161	159
Depreciation and amortization	105	105	317	317
Other expenses and interest	229	233	688	699
Total expenses	2,543	2,491	7,498	7,552
Loss from discontinued operations before income tax	1,041	(1,081)	368	(2,673)
Income tax benefit	276	(286)	101	(705)
Loss from discontinued operations, net of tax	$ 765	$ (795)	$ 267	$ (1,968)
Loss from discontinued operations per share of common stock
Basic (in dollars per share)	$ 0.02	$ (0.02)	$ 0.01	$ (0.07)
Diluted (in dollars per share)	$ 0.02	$ (0.02)	$ 0.01	$ (0.07)
Gill Ranch [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percent ownership	75.00%		75.00%
Pacific Gas and Electric Company [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percent ownership	25.00%		25.00%
Forecast [Member] | Minimum [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses					$ 25,000
Forecast [Member] | Maximum [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses					$ 26,500