Summary of Significant Accounting Policies	3 Months Ended
Mar. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies [Text Block]	Summary of Significant Accounting Policies Nature of Operations: American States Water Company (“AWR”) is the parent company of Golden State Water Company (“GSWC”) and American States Utility Services, Inc. (“ASUS”) (and its 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.” AWR, through its wholly owned subsidiaries, serves over one million people in nine states. GSWC is a public utility engaged principally in the purchase, production, distribution and sale of water in California serving approximately 260,000 customer connections. GSWC also distributes electricity in several San Bernardino County mountain communities in California serving approximately 24,000 customer connections through its Bear Valley Electric Service (“BVES”) division. The California Public Utilities Commission (“CPUC”) regulates GSWC’s water and electric businesses in matters including properties, rates, services, facilities and transactions by GSWC with its affiliates. In December 2018, GSWC filed an application with the CPUC to transfer the assets and liabilities of the BVES division of GSWC to Bear Valley Electric Service, Inc., a newly created separate legal entity and stand-alone subsidiary of AWR. This reorganization plan is subject to CPUC approval and, if approved, is not expected to result in a substantive change to AWR's operations and business segments. 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 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 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, all of which are wholly owned. 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, 2018 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 those 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, 2018 filed with the SEC. Related Party Transactions: GSWC and ASUS provide and/or receive various support services to and from their parent, AWR, and among themselves. GSWC also allocates certain corporate office administrative and general costs to its affiliate, ASUS, using allocation factors approved by the CPUC. GSWC allocated corporate office administrative and general costs to ASUS of approximately $1.1 million and $1.0 million during the three months ended March 31, 2019 and 2018, respectively. AWR borrows under a credit facility, which expires in May 2023, and provides funds to its subsidiaries, GSWC and ASUS, in support of their operations. In March 2019, AWR amended this credit facility to increase its borrowing capacity from $150.0 million to $200.0 million. As of March 31, 2019, there was $151.5 million outstanding under this facility. The interest rate charged to GSWC and ASUS is sufficient to cover AWR’s interest expense under the credit facility. GSWC Long-Term Debt: In March 2019, GSWC repaid $40 million of its 6.70% senior note, which matured in that month. GSWC increased its intercompany borrowings from AWR parent to fund the repayment of this note. Recently Issued Accounting Pronouncements: In February 2016, the Financial Accounting Standards Board ("FASB") issued a new lease accounting standard, Leases (Accounting Standards Codification ("ASC") 842), which replaces the prior lease guidance, (ASC 840). Under the new standard, lessees will recognize a right-of-use asset and a lease liability for virtually all leases (other than leases that meet the definition of a short-term lease). For income statement purposes, leases will be classified as either operating or finance. Operating leases will result in straight-line expense while finance leases will result in a front-loaded expense pattern. Registrant adopted the new lease accounting standard as of January 1, 2019 and did not adjust comparative periods for it. There was no cumulative-effect impact to the opening balance of retained earnings as a result of this adoption. Registrant elected the practical expedient under ASU 2018-01 Land Easement Practical Expedient for Transition to Topic 842 and did not review existing easements entered into prior to January 1, 2019. Leases with terms of twelve months or less were not recorded on the balance sheet. The adoption of the new lease guidance did not have a material impact on Registrant's results of operations or liquidity, but resulted in the recognition of operating lease liabilities and operating lease right-of-use assets on its balance sheets. As of March 31, 2019, Registrant has $6.3 million of right-of-use assets and $6.5 million in operating lease liabilities reflected on its balance sheet (see Note 10). In August 2018, the FASB issued Accounting Standards Update ("ASU") 2018-15-Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. Under this ASU, entities that enter into cloud computing service arrangements will apply existing internal-use software guidance to determine which implementation costs are eligible for capitalization. Under that guidance, implementation costs are capitalized or expensed depending on the nature of the costs and the project stage during which they are incurred. The new guidance is effective for fiscal years beginning after December 15, 2020. Early adoption is permitted. Registrant adopted this guidance effective January 1, 2019. This accounting change did not have a significant impact on Registrant's financial statements. In August 2018, the FASB issued ASU 2018-14-Compensation-Retirement Benefits-Defined Benefit Plans-General (Subtopic 715-20): Disclosure Framework-Changes to the Disclosure Requirements for Defined Benefit Plans. This ASU removes disclosures to pension plans and other post-retirement benefit plans that no longer are considered cost beneficial, clarifies the specific disclosure requirements and adds disclosure requirements deemed relevant. This ASU is effective for fiscal years ending after December 15, 2020 and will be applied by Registrant on a retrospective basis to all periods presented. Registrant is still evaluating the ASU and has not yet determined the effect of it on the Company's ongoing financial reporting.

Summary of Significant Accounting Policies

Nature of Operations: American States Water Company (“AWR”) is the parent company of Golden State Water Company (“GSWC”) and American States Utility Services, Inc. (“ASUS”) (and its 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.” AWR, through its wholly owned subsidiaries, serves over one million people in nine states.

GSWC is a public utility engaged principally in the purchase, production, distribution and sale of water in California serving approximately 260,000 customer connections. GSWC also distributes electricity in several San Bernardino County mountain communities in California serving approximately 24,000 customer connections through its Bear Valley Electric Service (“BVES”) division. The California Public Utilities Commission (“CPUC”) regulates GSWC’s water and electric businesses in matters including properties, rates, services, facilities and transactions by GSWC with its affiliates. In December 2018, GSWC filed an application with the CPUC to transfer the assets and liabilities of the BVES division of GSWC to Bear Valley Electric Service, Inc., a newly created separate legal entity and stand-alone subsidiary of AWR. This reorganization plan is subject to CPUC approval and, if approved, is not expected to result in a substantive change to AWR's operations and business segments.

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 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 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, all of which are wholly owned. 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, 2018 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 those 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, 2018 filed with the SEC.

Related Party Transactions: GSWC and ASUS provide and/or receive various support services to and from their parent, AWR, and among themselves. GSWC also allocates certain corporate office administrative and general costs to its affiliate, ASUS, using allocation factors approved by the CPUC. GSWC allocated corporate office administrative and general costs to ASUS of approximately $1.1 million and $1.0 million during the three months ended March 31, 2019 and 2018, respectively. AWR borrows under a credit facility, which expires in May 2023, and provides funds to its subsidiaries, GSWC and ASUS, in support of their operations. In March 2019, AWR amended this credit facility to increase its borrowing capacity from $150.0 million to $200.0 million. As of March 31, 2019, there was $151.5 million outstanding under this facility. The interest rate charged to GSWC and ASUS is sufficient to cover AWR’s interest expense under the credit facility.

GSWC Long-Term Debt: In March 2019, GSWC repaid $40 million of its 6.70% senior note, which matured in that month. GSWC increased its intercompany borrowings from AWR parent to fund the repayment of this note.

Recently Issued Accounting Pronouncements: In February 2016, the Financial Accounting Standards Board ("FASB") issued a new lease accounting standard, Leases (Accounting Standards Codification ("ASC") 842), which replaces the prior lease guidance, (ASC 840). Under the new standard, lessees will recognize a right-of-use asset and a lease liability for virtually all leases (other than leases that meet the definition of a short-term lease). For income statement purposes, leases will be classified as either operating or finance. Operating leases will result in straight-line expense while finance leases will result in a front-loaded expense pattern. Registrant adopted the new lease accounting standard as of January 1, 2019 and did not adjust comparative periods for it. There was no cumulative-effect impact to the opening balance of retained earnings as a result of this adoption. Registrant elected the practical expedient under ASU 2018-01 Land Easement Practical Expedient for Transition to Topic 842 and did not review existing easements entered into prior to January 1, 2019. Leases with terms of twelve months or less were not recorded on the balance sheet. The adoption of the new lease guidance did not have a material impact on Registrant's results of operations or liquidity, but resulted in the recognition of operating lease liabilities and operating lease right-of-use assets on its balance sheets. As of March 31, 2019, Registrant has $6.3 million of right-of-use assets and $6.5 million in operating lease liabilities reflected on its balance sheet (see Note 10).

In August 2018, the FASB issued Accounting Standards Update ("ASU") 2018-15-Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. Under this ASU, entities that enter into cloud computing service arrangements will apply existing internal-use software guidance to determine which implementation costs are eligible for capitalization. Under that guidance, implementation costs are capitalized or expensed depending on the nature of the costs and the project stage during which they are incurred. The new guidance is effective for fiscal years beginning after December 15, 2020. Early adoption is permitted. Registrant adopted this guidance effective January 1, 2019. This accounting change did not have a significant impact on Registrant's financial statements.

In August 2018, the FASB issued ASU 2018-14-Compensation-Retirement Benefits-Defined Benefit Plans-General (Subtopic 715-20): Disclosure Framework-Changes to the Disclosure Requirements for Defined Benefit Plans. This ASU removes disclosures to pension plans and other post-retirement benefit plans that no longer are considered cost beneficial, clarifies the specific disclosure requirements and adds disclosure requirements deemed relevant. This ASU is effective for fiscal years ending after December 15, 2020 and will be applied by Registrant on a retrospective basis to all periods presented. Registrant is still evaluating the ASU and has not yet determined the effect of it on the Company's ongoing financial reporting.