Income Taxes:	6 Months Ended
Jun. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes: AWR's consolidated effective tax rate (“ETR”) was 38.6% and 37.5% for the three months ended June 30, 2017 and 2016, respectively, and was 37.4% and 37.1% for the six months ended June 30, 2017 and 2016, respectively. AWR’s ETR increased during the three and six months ended June 30, 2017 primarily due to the increase in GSWC's ETR. GSWC's ETR was 39.8% and 39.0% for the three months ended June 30, 2017 and 2016, respectively, and was 38.8% and 38.5% for the six months ended June 30, 2017 and 2016, respectively. GSWC's ETR increased and also deviated from the statutory rate due to state tax and differences between book and taxable income that are treated as flow-through adjustments in accordance with regulatory requirements (principally plant-, rate-case- and compensation-related items). As a regulated utility, GSWC treats certain temporary differences as flow-through adjustments in computing its income tax provision consistent with the income tax approach approved by the CPUC for ratemaking purposes. Flow-through adjustments increase or decrease tax expense in one period, with an offsetting decrease or increase occurring in another period. Giving effect to these temporary differences as flow-through adjustments typically results in a greater variance between the ETR and the statutory federal income tax rate in any given period than would otherwise exist if GSWC were not required to account for its income taxes as a regulated enterprise. Change in Accounting Guidance: Effective January 1, 2017, Registrant adopted the new accounting standard addressing share-based payments (see Note 1). Under the new guidance, the tax effects related to share-based payments are required to be recorded through the income statement. Previously, tax benefits in excess of compensation cost ("windfalls") were recorded directly to equity and tax deficiencies ("shortfalls") were recorded to equity to the extent of any pool of windfall tax benefits from prior awards, with the remainder recognized in income tax expense. AWR and GSWC adopted the guidance effective January 1, 2017 and, therefore, all excess tax benefits resulting from share-based payments during the three and six months ended June 30, 2017 were reflected in the income statements. For the three months ended June 30, 2017, this reduced income tax expense by approximately $328,000 and $327,000 for AWR and GSWC, respectively. For the six months ended June 30, 2017, the reduction to income tax expense was approximately $740,000 and $701,000 for AWR and GSWC, respectively.

Income Taxes:

AWR's consolidated effective tax rate (“ETR”) was 38.6% and 37.5% for the three months ended June 30, 2017 and 2016, respectively, and was 37.4% and 37.1% for the six months ended June 30, 2017 and 2016, respectively. AWR’s ETR increased during the three and six months ended June 30, 2017 primarily due to the increase in GSWC's ETR. GSWC's ETR was 39.8% and 39.0% for the three months ended June 30, 2017 and 2016, respectively, and was 38.8% and 38.5% for the six months ended June 30, 2017 and 2016, respectively. GSWC's ETR increased and also deviated from the statutory rate due to state tax and differences between book and taxable income that are treated as flow-through adjustments in accordance with regulatory requirements (principally plant-, rate-case- and compensation-related items).

As a regulated utility, GSWC treats certain temporary differences as flow-through adjustments in computing its income tax provision consistent with the income tax approach approved by the CPUC for ratemaking purposes. Flow-through adjustments increase or decrease tax expense in one period, with an offsetting decrease or increase occurring in another period. Giving effect to these temporary differences as flow-through adjustments typically results in a greater variance between the ETR and the statutory federal income tax rate in any given period than would otherwise exist if GSWC were not required to account for its income taxes as a regulated enterprise.

Change in Accounting Guidance:

Effective January 1, 2017, Registrant adopted the new accounting standard addressing share-based payments (see Note 1). Under the new guidance, the tax effects related to share-based payments are required to be recorded through the income statement. Previously, tax benefits in excess of compensation cost ("windfalls") were recorded directly to equity and tax deficiencies ("shortfalls") were recorded to equity to the extent of any pool of windfall tax benefits from prior awards, with the remainder recognized in income tax expense. AWR and GSWC adopted the guidance effective January 1, 2017 and, therefore, all excess tax benefits resulting from share-based payments during the three and six months ended June 30, 2017 were reflected in the income statements. For the three months ended June 30, 2017, this reduced income tax expense by approximately $328,000 and $327,000 for AWR and GSWC, respectively. For the six months ended June 30, 2017, the reduction to income tax expense was approximately $740,000 and $701,000 for AWR and GSWC, respectively.