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Summary of Significant Accounting Policies (Details) customer in Thousands | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2016 USD ($) customer registrant | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) | Oct. 31, 2016 USD ($) | Sep. 30, 2016 USD ($) | Oct. 27, 2015 USD ($)
Summary of significant accounting policies |  |  |  |  |  |
Deferred Finance Costs, Net | $ 4,271,000 | $ 4,641,000 |  |  |  |
Related Party Transaction, Amounts of Transaction | $ 3,900,000 | 2,600,000 | $ 2,700,000 |  |  |
Basis of Presentation: |  |  |  |  |  |
Number of registrants filing combined report | registrant | 2 |  |  |  |  |
Impairment of Long-Lived Assets |  |  |  |  |  |
Impairment of long-lived assets | $ 0 | 0 | 0 |  |  |
Goodwill |  |  |  |  |  |
Goodwill arose from acquisition of subcontractor's business | 1,100,000 | 1,100,000 |  |  |  |
Sales and Use Taxes: |  |  |  |  |  |
Non-income tax assessments accounted on a gross basis | $ 16,801,000 | 16,636,000 | $ 16,722,000 |  |  |
Military Utility Privatization Subsidiaries |  |  |  |  |  |
Summary of significant accounting policies |  |  |  |  |  |
Period of Fixed Price Contracts to Maintain Water Systems at Various Military Bases | 50 years |  |  |  |  |
GSWC |  |  |  |  |  |
Summary of significant accounting policies |  |  |  |  |  |
Deferred Finance Costs, Net | $ 4,271,000 | $ 4,641,000 |  |  |  |
Property and Depreciation |  |  |  |  |  |
Aggregate composite rate for depreciation (as a percent) | 2.90% | 3.20% | 3.20% |  |  |
Depreciation on transportation equipment | $ 259,000 | $ 641,000 | $ 678,000 |  |  |
Estimated useful lives of utility plant, as authorized by the CPUC |  |  |  |  |  |
Generation | 40 years |  |  |  |  |
Interest |  |  |  |  |  |
Amount recorded in AFUDC | $ 101,000 | 694,000 | 24,000 |  |  |
Alternative-Revenue Programs |  |  |  |  |  |
Number of months within which expected additional revenue collection is recorded | 24 months |  |  |  |  |
Advances for Construction and Contributions in aid of Constructions |  |  |  |  |  |
Period for refund of advances for construction | 40 years |  |  |  |  |
Fair Value of Financial Instruments |  |  |  |  |  |
Long-term debt-GSWC | $ 423,124,000 |  |  |  |  |
Sales and Use Taxes: |  |  |  |  |  |
Franchise fees billed to customers and recorded as operating revenue | 3,500,000 | 3,800,000 | 3,700,000 |  |  |
Non-income tax assessments accounted on a gross basis | 15,444,000 | 15,244,000 | 15,221,000 |  |  |
GSWC | Level 1 |  |  |  |  |  |
Fair Value of Financial Instruments |  |  |  |  |  |
Long-term debt-GSWC | 0 |  |  |  |  |
GSWC | Level 3 |  |  |  |  |  |
Fair Value of Financial Instruments |  |  |  |  |  |
Long-term debt-GSWC | 0 |  |  |  |  |
GSWC | Carrying Amount |  |  |  |  |  |
Fair Value of Financial Instruments |  |  |  |  |  |
Long-term debt-GSWC | 325,582,000 | 325,853,000 |  |  |  |
GSWC | Fair Value |  |  |  |  |  |
Fair Value of Financial Instruments |  |  |  |  |  |
Long-term debt-GSWC |  | 403,844,000 |  |  |  |
GSWC | Fair Value | Level 2 |  |  |  |  |  |
Fair Value of Financial Instruments |  |  |  |  |  |
Long-term debt-GSWC | $ 423,124,000 |  |  |  |  |
GSWC | Minimum [Member] |  |  |  |  |  |
Estimated useful lives of utility plant, as authorized by the CPUC |  |  |  |  |  |
Source of water supply | 30 years |  |  |  |  |
Pumping | 25 years |  |  |  |  |
Water treatment | 20 years |  |  |  |  |
Transmission and distribution | 25 years |  |  |  |  |
Other plant | 7 years |  |  |  |  |
GSWC | Maximum [Member] |  |  |  |  |  |
Estimated useful lives of utility plant, as authorized by the CPUC |  |  |  |  |  |
Source of water supply | 50 years |  |  |  |  |
Pumping | 40 years |  |  |  |  |
Water treatment | 35 years |  |  |  |  |
Transmission and distribution | 55 years |  |  |  |  |
Other plant | 40 years |  |  |  |  |
GSWC | Notes Payable, Other Payables [Member] |  |  |  |  |  |
Related Party Transactions |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  | $ 40,000,000
Debt Instrument, Maximum Borrowing Capacity |  |  |  |  |  | 40,000,000
GSWC | Purchase, production, distribution and sale of water |  |  |  |  |  |
Nature of Operations: |  |  |  |  |  |
Number of customers served | customer | 261 |  |  |  |  |
Interest |  |  |  |  |  |
Weighted cost of capital (as a percent) | 8.34% |  |  |  |  |
GSWC | Electric |  |  |  |  |  |
Nature of Operations: |  |  |  |  |  |
Number of customers served | customer | 24 |  |  |  |  |
Sales and Use Taxes: |  |  |  |  |  |
Cost Of Debt Percent | 6.96% |  |  |  |  |
American States Utility Services [Member] |  |  |  |  |  |
Sales and Use Taxes: |  |  |  |  |  |
Non-income tax assessments accounted on a gross basis | $ 309,000 | 367,000 | $ 490,000 |  |  |
American States Utility Services [Member] | Notes Payable, Other Payables [Member] |  |  |  |  |  |
Related Party Transactions |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  | 10,000,000
Debt Instrument, Maximum Borrowing Capacity |  |  |  |  |  | $ 10,000,000
American States Utility Services [Member] | Military Utility Privatization Subsidiaries |  |  |  |  |  |
Nature of Operations: |  |  |  |  |  |
Period of fixed price contracts to operate and maintain the water and/or wastewater systems at various military bases | 50 years |  |  |  |  |
AWR |  |  |  |  |  |
Related Party Transactions |  |  |  |  |  |
Maximum borrowing capacity on line of credit |  |  |  | $ 150,000,000 | $ 100,000,000.0 |
Notes Receivable | GSWC | Notes Payable, Other Payables [Member] |  |  |  |  |  |
Related Party Transactions |  |  |  |  |  |
Notes Receivable, Related Parties, Current | $ 0 |  |  |  |  |
Notes Receivable | AWR | Notes Payable, Other Payables [Member] |  |  |  |  |  |
Related Party Transactions |  |  |  |  |  |
Notes Receivable, Related Parties, Current |  | $ 0 |  |  | $ 0 |
Sales [Member] | GSWC | Purchase, production, distribution and sale of water |  |  |  |  |  |
Nature of Operations: |  |  |  |  |  |
Percentage of total revenues | 90.00% | 90.00% | 90.00% |  |  |
Syndicated revolving credit facility | AWR | Syndicated revolving credit facility |  |  |  |  |  |
Related Party Transactions |  |  |  |  |  |
Maximum borrowing capacity on line of credit | $ 150,000,000 |  |  |  |  |

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- Definition All taxes not related to income of the entity or excise or sales taxes levied on the revenue of the entity that are not reported elsewhere. These taxes could include production, real estate, personal property, and pump tax. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.9) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 + Details
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