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Business Segments (Details) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Details of reportable segment |  |  |  |  |  |
Operating revenues | $ 465,791 us-gaap_SalesRevenueNet |  | $ 472,077 us-gaap_SalesRevenueNet |  | $ 466,908 us-gaap_SalesRevenueNet |
Operating income (loss) | 119,045 us-gaap_OperatingIncomeLoss |  | 119,072 us-gaap_OperatingIncomeLoss |  | 111,094 us-gaap_OperatingIncomeLoss |
Interest expense, net | (20,690)us-gaap_InterestIncomeExpenseNonoperatingNet |  | (21,708)us-gaap_InterestIncomeExpenseNonoperatingNet |  | (21,432)us-gaap_InterestIncomeExpenseNonoperatingNet |
Utility Plant | 1,003,520 us-gaap_PropertyPlantAndEquipmentNet |  | 981,477 us-gaap_PropertyPlantAndEquipmentNet |  | 917,791 us-gaap_PropertyPlantAndEquipmentNet |
Depreciation and amortization expense | 41,073 us-gaap_DepreciationDepletionAndAmortization | [1] | 40,090 us-gaap_DepreciationDepletionAndAmortization | [1] | 41,385 us-gaap_DepreciationDepletionAndAmortization | [1]
Income tax expense/(benefit) | 38,048 us-gaap_IncomeTaxExpenseBenefit |  | 35,783 us-gaap_IncomeTaxExpenseBenefit |  | 35,945 us-gaap_IncomeTaxExpenseBenefit |
Capital additions | 72,553 us-gaap_PropertyPlantAndEquipmentAdditions |  | 97,379 us-gaap_PropertyPlantAndEquipmentAdditions |  | 68,104 us-gaap_PropertyPlantAndEquipmentAdditions |
GSWC |  |  |  |  |  |
Details of reportable segment |  |  |  |  |  |
Number of reportable segments | 2 us-gaap_NumberOfReportableSegments / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember |  |  |  |  |
Operating revenues | 361,059 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember |  | 358,540 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember |  | 342,931 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember |
Operating income (loss) | 99,742 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember |  | 102,343 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember |  | 86,605 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember |
Utility Plant | 998,880 us-gaap_PropertyPlantAndEquipmentNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember |  | 977,294 us-gaap_PropertyPlantAndEquipmentNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember |  |  |
Depreciation and amortization expense | 39,854 us-gaap_DepreciationDepletionAndAmortization / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember |  | 38,952 us-gaap_DepreciationDepletionAndAmortization / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember |  | 40,197 us-gaap_DepreciationDepletionAndAmortization / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember |
Income tax expense/(benefit) | 32,006 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember |  | 33,134 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember |  | 26,500 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember |
GSWC | Water |  |  |  |  |  |
Details of reportable segment |  |  |  |  |  |
Operating revenues | 326,672 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember |  | 320,131 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember |  | 305,898 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember |
Operating income (loss) | 94,014 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember |  | 95,932 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember |  | 78,104 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember |
Interest expense, net | (19,370)us-gaap_InterestIncomeExpenseNonoperatingNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember |  | (20,236)us-gaap_InterestIncomeExpenseNonoperatingNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember |  | (19,783)us-gaap_InterestIncomeExpenseNonoperatingNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember |
Utility Plant | 953,678 us-gaap_PropertyPlantAndEquipmentNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember |  | 936,386 us-gaap_PropertyPlantAndEquipmentNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember |  | 871,756 us-gaap_PropertyPlantAndEquipmentNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember |
Depreciation and amortization expense | 38,388 us-gaap_DepreciationDepletionAndAmortization / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember | [1] | 36,636 us-gaap_DepreciationDepletionAndAmortization / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember | [1] | 37,905 us-gaap_DepreciationDepletionAndAmortization / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember | [1]
Income tax expense/(benefit) | 30,410 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember |  | 30,679 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember |  | 24,231 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember |
Capital additions | 66,304 us-gaap_PropertyPlantAndEquipmentAdditions / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember |  | 94,581 us-gaap_PropertyPlantAndEquipmentAdditions / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember |  | 62,500 us-gaap_PropertyPlantAndEquipmentAdditions / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_WaterServiceUtilityOperationsMember |
GSWC | Electric |  |  |  |  |  |
Details of reportable segment |  |  |  |  |  |
Operating revenues | 34,387 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember |  | 38,409 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember |  | 37,033 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember |
Operating income (loss) | 5,728 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember |  | 6,411 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember |  | 8,501 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember |
Interest expense, net | (1,260)us-gaap_InterestIncomeExpenseNonoperatingNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember |  | (1,436)us-gaap_InterestIncomeExpenseNonoperatingNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember |  | (1,533)us-gaap_InterestIncomeExpenseNonoperatingNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember |
Utility Plant | 45,202 us-gaap_PropertyPlantAndEquipmentNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember |  | 40,908 us-gaap_PropertyPlantAndEquipmentNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember |  | 41,381 us-gaap_PropertyPlantAndEquipmentNet / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember |
Depreciation and amortization expense | 1,466 us-gaap_DepreciationDepletionAndAmortization / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember | [1] | 2,316 us-gaap_DepreciationDepletionAndAmortization / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember | [1] | 2,292 us-gaap_DepreciationDepletionAndAmortization / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember | [1]
Income tax expense/(benefit) | 1,596 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember |  | 2,455 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember |  | 2,269 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember |
Capital additions | 4,584 us-gaap_PropertyPlantAndEquipmentAdditions / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember |  | 2,124 us-gaap_PropertyPlantAndEquipmentAdditions / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember |  | 4,331 us-gaap_PropertyPlantAndEquipmentAdditions / dei_LegalEntityAxis = awr_GoldenStateWaterCompanyMember / us-gaap_StatementBusinessSegmentsAxis = awr_ElectricServiceUtilityOperationsMember |
American States Utility Services [Member] | Military Utility Privatization Subsidiaries |  |  |  |  |  |
Details of reportable segment |  |  |  |  |  |
Operating revenues | 104,732 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember |  | 113,537 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember |  | 123,977 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember |
Operating income (loss) | 19,351 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember |  | 16,737 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember |  | 24,608 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember |
Interest expense, net | (142)us-gaap_InterestIncomeExpenseNonoperatingNet / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember |  | (264)us-gaap_InterestIncomeExpenseNonoperatingNet / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember |  | (179)us-gaap_InterestIncomeExpenseNonoperatingNet / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember |
Utility Plant | 4,640 us-gaap_PropertyPlantAndEquipmentNet / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember |  | 4,183 us-gaap_PropertyPlantAndEquipmentNet / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember |  | 4,654 us-gaap_PropertyPlantAndEquipmentNet / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember |
Depreciation and amortization expense | 1,219 us-gaap_DepreciationDepletionAndAmortization / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember | [1] | 1,138 us-gaap_DepreciationDepletionAndAmortization / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember | [1] | 1,188 us-gaap_DepreciationDepletionAndAmortization / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember | [1]
Income tax expense/(benefit) | 7,038 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember |  | 4,911 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember |  | 9,437 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember |
Capital additions | 1,665 us-gaap_PropertyPlantAndEquipmentAdditions / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember |  | 674 us-gaap_PropertyPlantAndEquipmentAdditions / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember |  | 1,273 us-gaap_PropertyPlantAndEquipmentAdditions / dei_LegalEntityAxis = awr_AmericanStatesUtilityServicesMember / us-gaap_StatementBusinessSegmentsAxis = awr_ContractedServicesMember |
AWR Parent |  |  |  |  |  |
Details of reportable segment |  |  |  |  |  |
Number of reportable segments | 3 us-gaap_NumberOfReportableSegments / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |  |  |  |
Operating revenues | 0 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 0 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 0 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |
Operating income (loss) | (48)us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | (8)us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | (119)us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |
Interest expense, net | 82 us-gaap_InterestIncomeExpenseNonoperatingNet / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 228 us-gaap_InterestIncomeExpenseNonoperatingNet / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 63 us-gaap_InterestIncomeExpenseNonoperatingNet / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |
Utility Plant | 0 us-gaap_PropertyPlantAndEquipmentNet / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 0 us-gaap_PropertyPlantAndEquipmentNet / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 0 us-gaap_PropertyPlantAndEquipmentNet / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |
Depreciation and amortization expense | 0 us-gaap_DepreciationDepletionAndAmortization / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | [1] | 0 us-gaap_DepreciationDepletionAndAmortization / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | [1] | 0 us-gaap_DepreciationDepletionAndAmortization / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | [1]
Income tax expense/(benefit) | (996)us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | (2,262)us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 8 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |
Capital additions | $ 0 us-gaap_PropertyPlantAndEquipmentAdditions / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | $ 0 us-gaap_PropertyPlantAndEquipmentAdditions / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | $ 0 us-gaap_PropertyPlantAndEquipmentAdditions / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |
[1] | Depreciation computed on GSWC’s transportation equipment is recorded in other operating expenses and totaled $678,000, $877,000 and $1.8 million for the years ended December 31, 2014, 2013 and 2012, respectively.

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