Income Taxes:	3 Months Ended
Mar. 31, 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. The GSWC ETR was 41.1% and 37.9% for the three months ended March 31, 2015 and 2014, 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 related to plant, rate-case and compensation items), as well as permanent items. The ETR at the AWR consolidated level also fluctuates as a result of ASUS's state income taxes, which vary among the jurisdictions in which it operates, and certain permanent differences. 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 the 2014 tax returns on or before September 15, 2015, the Company will file 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 will also include a cumulative adjustment for 2013 and prior years, and will permit 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 did not reduce total income tax expense or 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. The GSWC ETR was 41.1% and 37.9% for the three months ended March 31, 2015 and 2014, 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 related to plant, rate-case and compensation items), as well as permanent items. The ETR at the AWR consolidated level also fluctuates as a result of ASUS's state income taxes, which vary among the jurisdictions in which it operates, and certain permanent differences.

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 the 2014 tax returns on or before September 15, 2015, the Company will file 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 will also include a cumulative adjustment for 2013 and prior years, and will permit 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 did not reduce total income tax expense or ETR.