Utility Plant and Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	$ 1,620,325	$ 1,527,537
Less - accumulated depreciation	(532,753)	(529,698)
Construction work in progress	(63,354)	(62,955)
Net utility plant	1,150,926	1,060,794	$ 1,003,520
American States Utility Services [Member] | Intangible Assets [Member]
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	571	571
Water
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	1,526,316	1,439,056
Water | Land
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	15,393	15,299
Water | Intangible Assets [Member]
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	36,291	34,848
Water | Source of water supply
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	86,775	86,914
Water | Pumping
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	169,983	161,668
Water | Water treatment
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	74,980	72,238
Water | Transmission and distribution
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	1,014,925	941,651
Water | General
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	127,969	126,438
Electric
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	94,009	88,481
Electric | Intangible Assets [Member]
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	1,200	1,200
Electric | Transmission and distribution
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	71,112	66,121
Electric | Generation
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	12,583	12,563
Electric | General
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	10,314	9,797
GSWC
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	1,608,428	1,516,505
Less - accumulated depreciation	(524,927)	(522,749)
Construction work in progress	(61,810)	(62,360)
Net utility plant	1,145,311	1,056,116
GSWC | Water
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	1,514,419	1,428,024
Net utility plant	1,089,031	1,005,114	953,678
GSWC | Water | Land
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	15,393	15,299
GSWC | Water | Intangible Assets [Member]
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	36,273	34,830
GSWC | Water | Source of water supply
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	86,775	86,914
GSWC | Water | Pumping
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	169,983	161,668
GSWC | Water | Water treatment
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	74,980	72,238
GSWC | Water | Transmission and distribution
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	1,014,925	941,651
GSWC | Water | General
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	116,090	115,424
GSWC | Electric
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	94,009	88,481
Net utility plant	56,280	51,002	$ 45,202
GSWC | Electric | Transmission and distribution
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	71,112	66,121
GSWC | Electric | Generation
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	12,583	12,563
GSWC | Electric | General
Utility plant utilized in continuing operations by major asset class
Total utility plant, at cost	$ 10,314	$ 9,797