Income Taxes:	9 Months Ended
Sep. 30, 2016
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes: 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 effective tax rate (“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. GSWC's ETR was 38.2% and 42.7% for the three months ended September 30, 2016 and 2015, respectively, and 38.3% and 41.6% for the nine months ended September 30, 2016 and 2015, respectively. The GSWC ETRs deviated from the statutory rate primarily due to state taxes and differences between book and taxable income that are treated as flow-through adjustments in accordance with regulatory requirements (primarily plant-, rate-case- and compensation-related items). The ETR at the AWR consolidated level may also fluctuate as a result of certain permanent differences as well as state taxes recorded at AWR (parent) and at ASUS and the Military Utility Privatization Subsidiaries (where the amounts of state taxes vary among the jurisdictions in which they operate). Changes in Tax Law: In December 2015, the Protecting Americans From Tax Hikes Act of 2015 extended bonus depreciation for qualifying property through 2019. For 2015 through 2017, bonus depreciation was extended at a 50% rate. For 2018-2019, bonus depreciation will be phased down to 40% and 30%, respectively. Although the change in law reduces Registrant’s current taxes payable over these years, it does not reduce its total income tax expense or ETR.

Income Taxes:

9 Months Ended

Sep. 30, 2016

Income Taxes:

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 effective tax rate (“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. GSWC's ETR was 38.2% and 42.7% for the three months ended September 30, 2016 and 2015, respectively, and 38.3% and 41.6% for the nine months ended September 30, 2016 and 2015, respectively. The GSWC ETRs deviated from the statutory rate primarily due to state taxes and differences between book and taxable income that are treated as flow-through adjustments in accordance with regulatory requirements (primarily plant-, rate-case- and compensation-related items). The ETR at the AWR consolidated level may also fluctuate as a result of certain permanent differences as well as state taxes recorded at AWR (parent) and at ASUS and the Military Utility Privatization Subsidiaries (where the amounts of state taxes vary among the jurisdictions in which they operate).

Changes in Tax Law:

In December 2015, the Protecting Americans From Tax Hikes Act of 2015 extended bonus depreciation for qualifying property through 2019. For 2015 through 2017, bonus depreciation was extended at a 50% rate. For 2018-2019, bonus depreciation will be phased down to 40% and 30%, respectively. Although the change in law reduces Registrant’s current taxes payable over these years, it does not reduce its total income tax expense or ETR.