Business Segments 2 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting [Abstract]
Total utility plant	$ 1,415,705	$ 1,296,310	$ 1,204,992
Other assets	225,626	205,123
Total Assets	1,641,331	1,501,433
Parent Company
Segment Reporting [Abstract]
Total utility plant	0	0	0
Total Assets	811,677	659,205
GSWC
Segment Reporting [Abstract]
Total utility plant	1,394,742	1,281,092
Total Assets	1,522,454	1,389,222
Segment Reporting Information [Line Items]
Depreciation on transportation equipment	316	238	242
Contracted services: | American States Utility Services [Member]
Segment Reporting [Abstract]
Total utility plant	$ 20,963	$ 15,218	$ 7,052