Summary of Significant Accounting Policies	3 Months Ended
Summary of Significant Accounting Policies	Mar. 31, 2021
Accounting Policies [Abstract]
Significant Accounting Policies	Summary of Significant Accounting Policies Nature of Operations: American States Water Company (“AWR”) is the parent company of Golden State Water Company (“GSWC”), Bear Valley Electric Service, Inc. ("BVESI"), and American States Utility Services, Inc. (“ASUS”) (and its wholly owned subsidiaries: Fort Bliss Water Services Company (“FBWS”), Terrapin Utility Services, Inc. (“TUS”), Old Dominion Utility Services, Inc. (“ODUS”), Palmetto State Utility Services, Inc. (“PSUS”), Old North Utility Services, Inc. (“ONUS”), Emerald Coast Utility Services, Inc. ("ECUS"), and Fort Riley Utility Services, Inc. ("FRUS")). The subsidiaries of ASUS are collectively referred to as the “Military Utility Privatization Subsidiaries”. On July 1, 2020, GSWC completed the transfer of the electric utility assets and liabilities from its electric division to BVESI, a separate legal entity and wholly owned subsidiary of AWR (Note 11). This reorganization did not result in any substantive changes to AWR's operations and business segments. AWR, through its wholly owned subsidiaries, serves over one million people in nine states. GSWC and BVESI are both California public utilities. GSWC is engaged in the purchase, production, distribution and sale of water throughout California serving approximately 262,000 customer connections. BVESI distributes electricity in several San Bernardino County mountain communities in California serving approximately 24,500 customer connections. The California Public Utilities Commission (“CPUC”) regulates GSWC’s and BVESI's businesses in matters including properties, rates, services, facilities, and transactions between GSWC, BVESI, and their affiliates. ASUS, through its wholly owned subsidiaries, operates, maintains and performs construction activities (including renewal and replacement capital work) on water and/or wastewater systems at various U.S. military bases pursuant to initial 50-year firm fixed-price contracts. These contracts are subject to annual economic price adjustments and modifications for changes in circumstances, changes in laws and regulations, and additions to the contract value for new construction of facilities at the military bases. There is no direct regulatory oversight by the CPUC over AWR or the operations, rates or services provided by ASUS or any of its wholly owned subsidiaries. Basis of Presentation: The consolidated financial statements and notes thereto are presented in a combined report filed by two separate Registrants: AWR and GSWC. References in this report to “Registrant” are to AWR and GSWC, collectively, unless otherwise specified. AWR owns all of the outstanding common shares of GSWC, BVESI and ASUS. ASUS owns all of the outstanding common stock of the Military Utility Privatization Subsidiaries. The consolidated financial statements of AWR include the accounts of AWR and its subsidiaries. These financial statements are prepared in conformity with accounting principles generally accepted in the United States of America ("GAAP"). Intercompany transactions and balances have been eliminated in the AWR consolidated financial statements. The consolidated financial statements included herein have been prepared by Registrant, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). The December 31, 2020 condensed consolidated balance sheet data was derived from audited financial statements but does not include all disclosures required by GAAP. The preparation of the consolidated financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities, at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from these estimates. In the opinion of management, all adjustments consisting of normal, recurring items, and estimates necessary for a fair statement of the results for the interim periods have been made. It is suggested that these consolidated financial statements be read in conjunction with the consolidated financial statements and the notes thereto included in the Form 10-K for the year ended December 31, 2020 filed with the SEC. Related Party Transactions and Financing Activities: GSWC, BVESI and ASUS provide and/or receive various support services to and from their parent, AWR, and among themselves. GSWC has allocated certain corporate office administrative and general costs to its affiliates, BVESI and ASUS, using allocation factors approved by the CPUC. GSWC allocated corporate office administrative and general costs to BVESI of approximately $799,000 during the three months ended March 31, 2021. GSWC allocated corporate office administrative and general costs to ASUS of approximately $1.5 million and $1.4 million during the three months ended March 31, 2021 and 2020, respectively. AWR borrows under a $200.0 million credit facility, which expires in May 2023, and provides funds to GSWC and ASUS in support of their operations. The interest rate charged to GSWC and ASUS is sufficient to cover AWR’s interest expense under the credit facility. As of March 31, 2021, there was $107.0 million outstanding under this facility. BVESI has a separate $35 million revolving credit facility, which expires in July 2023. Under the terms of the credit agreement, BVESI has the option to request an increase in the facility by an additional $15 million. As of March 31, 2021, there was $22.0 million outstanding under this facility. The CPUC requires GSWC to completely pay down all intercompany borrowings from AWR within a 24-month period. The next 24-month period in which GSWC is required to completely pay down its intercompany borrowings is at the end of March 2023 since GSWC had zero borrowings from AWR as of March 31, 2021. In October 2020, AWR issued an interest bearing promissory note to GSWC, which expires in May 2023. Under the terms of the note, AWR may borrow from GSWC amounts up to $30 million for working capital purposes. AWR agrees to pay any unpaid principal amounts outstanding under this note, plus accrued interest. As of March 31, 2021, there was $12.0 million outstanding under this note reflected as a non-current asset on GSWC's balance sheet. COVID-19 Impact: GSWC, BVESI and ASUS have continued their operations given that their water, wastewater, and electric utility services are deemed essential. AWR's responses take into account orders issued by the CPUC, and the guidance provided by federal, state, and local health authorities and other government officials to the COVID-19 pandemic. Some of the actions taken by GSWC and BVESI continue to include: (i) suspending service disconnections for nonpayment pursuant to CPUC and state orders, and (ii) telecommuting by employees. In February 2021, the CPUC adopted a resolution that extended the existing emergency customer protections previously established by the CPUC through June 30, 2021, including the suspension of service disconnections for non-payment by electric utility customers in response to the on-going COVID-19 pandemic. For water utilities, the moratorium on service disconnections was implemented in response to an order by the governor of California, which we believe would require another action by the governor to cease the moratorium on service disconnections for our water customers. It is expected that the CPUC will work with the governor’s office to coordinate the lifting of the moratorium for water utility customers consistent with the electric customers. The CPUC's February resolution did extend the COVID-19-related memorandum accounts established by GSWC and by BVESI to track incremental costs associated with complying with the resolution. In addition, the resolution required utilities in California to file transition plans to address the eventual discontinuance of the emergency customer protections. The goal of the transition plan is to effectively ease customers through a transition off the emergency customer protections by proactively communicating with customers to enroll in programs to manage their utility bills and informing them of the changes to programs in which they are already enrolled. GSWC and BVESI filed their respective transition plans with the CPUC on April 1, 2021. Initially and throughout 2020, the pandemic caused significant volatility on financial markets resulting in fluctuations in the fair value of plan assets in GSWC's pension and other retirement plans. In addition, due to expected future credit losses on utility customer bills, GSWC and BVESI have increased their allowance for doubtful accounts. However, the CPUC has authorized GSWC and BVESI to track incremental costs, including bad debt expense in excess of what is included in their respective revenue requirements, incurred as a result of the pandemic in COVID-19-related memorandum accounts, such as a Catastrophic Event Memorandum Account ("CEMA"), to be filed with the CPUC for future recovery. GSWC and BVESI have recorded a total of approximately $5.7 million in these accounts as regulatory assets, as it is believed such amounts are probable of recovery. CEMA and other emergency-type memorandum accounts are established as a result of a state/federal declared emergency, and are therefore recognized as regulatory assets for future recovery. As a result, the amounts recorded in the COVID-19-related memorandum accounts have not impacted GSWC's and BVESI's earnings. GSWC's COVID-19 memorandum account is being addressed in its pending water general rate case, while BVESI intends to include the memorandum account for recovery in its next general rate case application expected to be filed in 2022. Thus far, the COVID-19 pandemic has not had a material impact on ASUS's operations. Accounting Pronouncements Adopted in 2021: In December 2019, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2019-12, Income Taxes (Topic 740)—Simplifying the Accounting for Income Taxes. The amendments in this update simplify the accounting for income taxes by removing certain exceptions and clarifying certain requirements regarding franchise taxes, goodwill, consolidated tax expenses, and annual effective tax rate calculations. The adoption of this guidance effective January 1, 2021 did not have a material impact on Registrant's financial statements.