Earnings Per Share / Capital Stock -Schedule of EPS (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Basic
Net Income		$ 130,442	$ 119,268	$ 124,921
Less: impact from participating securities		455	419	372
Total income available to common shareholders		$ 129,987	$ 118,849	$ 124,549
Weighted average Common Shares outstanding, basic (in shares)		38,550,000	37,464,000	36,976,000
Basic earnings per Common Share (in USD per share)		$ 3.37	$ 3.17	$ 3.37
Diluted
Total income available to common shareholders		$ 129,987	$ 118,849	$ 124,549
Undistributed earnings for dilutive stock-based awards		194	183	189
Total common shareholders earnings, diluted		$ 130,181	$ 119,032	$ 124,738
Weighted average Common Shares outstanding, basic (in shares)		38,550,000	37,464,000	36,976,000
Stock-based compensation (in shares)	[1]	123,000	119,000	101,000
Weighted Average Number of Diluted Shares (in shares)		38,673,000	37,583,000	37,077,000
Diluted earnings per common share (in USD per share)		$ 3.37	$ 3.17	$ 3.36
Restricted Stock Units
Diluted
Restricted stock units outstanding (in shares)		145,015	144,799	115,684

[1] (1)         In applying the treasury stock method of reflecting the dilutive effect of outstanding stock-based compensation in the calculation of diluted EPS, 145,015, 144,799 and 115,684 restricted stock units, including performance awards to officers of AWR, at December 31, 2025, 2024 and 2023, respectively, were deemed to be outstanding in accordance with accounting guidance on earnings per share.