Income Taxes:	9 Months Ended
Sep. 30, 2015
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 42.7% and 40.7% for the three months ended September 30, 2015 and 2014, respectively, and 41.6% and 40.5% for the nine months ended September 30, 2015 and 2014, respectively. GSWC's 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 related to plant, rate-case and compensation items), as well as permanent items. AWR's consolidated ETR was 40.6% for the three months ended September 30, 2015 as compared to 38.9% for the three months ended September 30, 2014, and was 39.4% for the nine months ended September 30, 2015 as compared to 38.8% for the nine months ended September 30, 2014. The ETR at the AWR consolidated level also fluctuated as a result of ASUS's state income taxes, which vary among the jurisdictions in which it operates. Changes in Tax Law: During the fourth quarter of 2014, the Company reflected a change in its tax method of accounting for certain repair and maintenance expenditures pursuant to regulations issued by the U.S. Treasury Department in September 2013. In connection with filing its 2014 federal tax return during the third quarter of 2015, the Company filed an application for an automatic change in tax accounting method with the Internal Revenue Service ("IRS") for the 2014 tax year to implement the new method (effective January 1, 2014). The tax accounting method change included a cumulative adjustment for 2013 and prior years, and permits the expensing of certain utility asset replacement costs that were previously being capitalized and depreciated for book and tax purposes. As a result of the change, the Company will deduct a significant amount of asset costs, which consist primarily of water mains and connections. During the fourth quarter of 2014, GSWC recorded a cumulative adjustment for 2013 and prior years as well as the 2014 estimated deduction, and recognized a total deferred income tax liability of $30.8 million for federal and state repair-and-maintenance deductions as of December 31, 2014. Although this change reduces AWR’s current taxes payable, it does not reduce total income tax expense or the ETR.

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 42.7% and 40.7% for the three months ended September 30, 2015 and 2014, respectively, and 41.6% and 40.5% for the nine months ended September 30, 2015 and 2014, respectively. GSWC's 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 related to plant, rate-case and compensation items), as well as permanent items.

AWR's consolidated ETR was 40.6% for the three months ended September 30, 2015 as compared to 38.9% for the three months ended September 30, 2014, and was 39.4% for the nine months ended September 30, 2015 as compared to 38.8% for the nine months ended September 30, 2014. The ETR at the AWR consolidated level also fluctuated as a result of ASUS's state income taxes, which vary among the jurisdictions in which it operates.

Changes in Tax Law:

During the fourth quarter of 2014, the Company reflected a change in its tax method of accounting for certain repair and maintenance expenditures pursuant to regulations issued by the U.S. Treasury Department in September 2013. In connection with filing its 2014 federal tax return during the third quarter of 2015, the Company filed an application for an automatic change in tax accounting method with the Internal Revenue Service ("IRS") for the 2014 tax year to implement the new method (effective January 1, 2014). The tax accounting method change included a cumulative adjustment for 2013 and prior years, and permits the expensing of certain utility asset replacement costs that were previously being capitalized and depreciated for book and tax purposes. As a result of the change, the Company will deduct a significant amount of asset costs, which consist primarily of water mains and connections.

During the fourth quarter of 2014, GSWC recorded a cumulative adjustment for 2013 and prior years as well as the 2014 estimated deduction, and recognized a total deferred income tax liability of $30.8 million for federal and state repair-and-maintenance deductions as of December 31, 2014. Although this change reduces AWR’s current taxes payable, it does not reduce total income tax expense or the ETR.