Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes AWR's effective income tax rate (“ETR”) was 25.4% and 25.1% for the three months ended September 30, 2020 and 2019, respectively, and was 24.3% and 23.3% for the nine months ended September 30, 2020 and 2019, respectively. GSWC's ETR was 26.7% and 26.4% for the three months ended September 30, 2020 and 2019, respectively, and was 25.5% and 24.1% for the nine months ended September 30, 2020 and 2019, respectively. The AWR and GSWC effective tax rates differ from the federal statutory tax rate primarily due to (i) state taxes; (ii) permanent differences, including the excess tax benefits from share-based payments, which were reflected in the income statements and resulted in a reduction to income tax expense during the three and nine months ended September 30, 2020 and 2019; (iii) the continuing amortization of the excess deferred income tax liability that commenced upon the lowering of the federal tax rate; and (iv) differences between book and taxable income that are treated as flow-through adjustments in accordance with regulatory requirements (principally from plant, rate-case, and compensation expenses). As a regulated utility, GSWC treats certain temporary differences as flow-through in computing its income tax expense consistent with the income tax method used in its CPUC-jurisdiction ratemaking. Flow-through items either increase or decrease tax expense and thus impact the ETR.

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.