Military Privatization (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Military Privatization
Contract liabilities (Note 2)	$ 11,167				$ 7,530				$ 11,167	$ 7,530
Receivables from the U.S. government:
Less: allowance for doubtful accounts	(916)				(951)				(916)	(951)	$ (1,041)	$ (764)
Pretax income
Increase in pretax operating income	$ 24,724	$ 42,724	$ 39,430	$ 20,195	$ 22,749	$ 33,975	$ 25,568	$ 18,691	$ 127,073	100,983	127,095
Contracted services:
Military Privatization
Period of fixed price contracts to maintain water systems at various military bases									50 years
Number of Operating Segments									8
American States Utility Services [Member] | Contracted services:
Pretax income
Increase in pretax operating income									$ 21,990	$ 20,414	21,320
Reportable Legal Entities [Member] | American States Utility Services [Member] | Contracted services:
Military Privatization
Revenue Recognition, Retrospective Rate-Setting Systems, Amount											$ 1,000