Completion of Electric Utility Reorganization Plan (Details) - USD ($) $ in Thousands		3 Months Ended						9 Months Ended
	Jul. 01, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Completion of Electric Utility Reorganization Plan[Line Items]
Gain (loss) on asset transfer	$ 0
Electric		$ 8,288			$ 11,996			$ 26,935	$ 30,033
Net income		$ 26,530	$ 25,612	$ 14,072	28,006	$ 26,784	$ 12,852	66,214	67,642
Net cash provided from operating activities								87,843	84,304
Net cash used in investing activities								(94,637)	(110,672)
Net cash provided from financing activities (2)								13,587	29,625
Revision of Prior Period, Adjustment [Member]
Completion of Electric Utility Reorganization Plan[Line Items]
Operating income					3,700
Bear Valley Electric Service, Inc.
Completion of Electric Utility Reorganization Plan[Line Items]
Net assets transferred	71,300
Bear Valley Electric Service, Inc.
Completion of Electric Utility Reorganization Plan[Line Items]
Debt instrument term		3 years
Maximum borrowing capacity on line of credit	35,000
Outstanding borrowings		$ 3,000						3,000
Incremental expansion of borrowing capacity	15,000
Taxes Payable	0
Bear Valley Electric Service, Inc. | Electric Service Utility Operations
Completion of Electric Utility Reorganization Plan[Line Items]
Electric		8,288
Operating expenses		6,423
Operating income		1,865
Net income		1,308
Net cash provided from operating activities		603
Net cash used in investing activities		(3,039)
Net cash provided from financing activities (2)		2,999
Net change in cash and cash equivalents		563
Cash and cash equivalents, end of period	$ 20	583						583
Golden State Water Company
Completion of Electric Utility Reorganization Plan[Line Items]
Electric		0			11,996			18,647	30,033
Net income		21,143	$ 20,919	$ 11,202	$ 23,362	$ 22,298	$ 9,022	53,264	54,682
Net cash provided from operating activities								75,093	68,956
Net cash used in investing activities								(87,529)	(104,429)
Net cash provided from financing activities (2)								$ 16,108	$ 35,739
Golden State Water Company | Electric Service Utility Operations
Completion of Electric Utility Reorganization Plan[Line Items]
Electric		11,996
Operating expenses		6,324
Operating income		5,672
Net income		$ 3,779