Business Segments 2 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting [Abstract]
Total utility plant	$ 1,204,992	$ 1,150,926	$ 1,060,794
Other assets	211,742	319,567
Total Assets	1,416,734	1,470,493
AWR Parent
Segment Reporting [Abstract]
Total utility plant	0	0	0
Total Assets	593,757	590,511
GSWC
Segment Reporting [Abstract]
Total utility plant	1,197,940	1,145,311
Total Assets	1,326,823	1,384,178
Segment Reporting Information [Line Items]
Depreciation on transportation equipment	242	259	641
American States Utility Services [Member] | American States Utility Services [Member]
Segment Reporting [Abstract]
Total utility plant	$ 7,052	$ 5,615	$ 4,678