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Summary of Significant Accounting Policies (Details) | 6 Months Ended | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Dec. 31, 2020 USD ($) | Dec. 31, 2021 USD ($) customer registrant shares | Dec. 31, 2020 USD ($) shares | Dec. 31, 2019 USD ($) shares | Feb. 02, 2022 USD ($) | Jan. 26, 2022 USD ($) | Jul. 12, 2021 USD ($)
Nature of Operations: |  |  |  |  |  |  |
Number of customers served | customer |  | 1,000,000 |  |  |  |  |
Number of States in which Entity Operates |  | 9 |  |  |  |  |
Number of registrants filing combined report | registrant |  | 2 |  |  |  |  |
Related Party Transactions |  |  |  |  |  |  |
Related Party Transaction, Amounts of Transaction |  | $ 5,300,000 | $ 4,900,000 | $ 4,700,000 |  |  |
Exercise of stock options and other issuance of Common Shares |  | 0 | 30,000 | 519,000 |  |  |
Line of credit facility, current borrowing capacity |  | 200,000,000 |  |  |  |  |
Impairment of Long-Lived Assets |  |  |  |  |  |  |
Asset Retirement Obligation, Legally Restricted Assets, Fair Value |  | 0 |  |  |  |  |
Impairment of long-lived assets |  | 0 | 0 | 0 |  |  |
Goodwill |  |  |  |  |  |  |
Goodwill arose from acquisition of subcontractor's business |  | $ 1,100,000 | 1,100,000 |  |  |  |
Advances for Construction and Contributions in aid of Constructions |  |  |  |  |  |  |
Period for refund of advances for construction |  | 40 years |  |  |  |  |
Common Stock [Member] |  |  |  |  |  |  |
Related Party Transactions |  |  |  |  |  |  |
Exercise of stock options and other issuance of Common Shares |  | $ 0 | $ 30,000 | $ 519,000 |  |  |
Stock Issued During Period, Shares, New Issues | shares |  | 47,000 | 42,000 | 89,000 |  |  |
GSWC |  |  |  |  |  |  |
Related Party Transactions |  |  |  |  |  |  |
Exercise of stock options and other issuance of Common Shares |  | $ 60,000,000 | $ 60,000,000 |  |  |  |
Regulatory Asset CEMA |  | $ 1,700,000 |  |  |  |  |
Property and Depreciation |  |  |  |  |  |  |
Aggregate composite rate for depreciation (as a percent) |  | 2.20% | 2.20% | 2.20% |  |  |
Depreciation |  | $ 35,500,000 | $ 32,900,000 | $ 31,700,000 |  |  |
Depreciation on transportation equipment |  | $ 379,000 | 353,000 | $ 316,000 |  |  |
Estimated useful lives of utility plant, as authorized by the CPUC |  |  |  |  |  |  |
Generation |  | 40 years |  |  |  |  |
Fair Value of Financial Instruments |  |  |  |  |  |  |
Long-term debt-GSWC |  | $ 490,852,000 |  |  |  |  |
Short-term Debt, Terms |  | 24 |  |  |  |  |
Approval amount for the relief funding |  | $ 9,500,000 |  |  |  |  |
Intercompany payables | $ 0 | 49,280,000 | 0 |  |  |  |
Water Utility Relief Funding For Overdue Water Bills Per Budget Act Of 2021 |  |  |  |  |  |  | $ 1,000,000,000
GSWC | Subsequent Event |  |  |  |  |  |  |
Fair Value of Financial Instruments |  |  |  |  |  |  |
Relief funding |  |  |  |  |  | $ 9,500,000 |
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 | 444,271,000 | 415,788,000 | 444,271,000 |  |  |  |
GSWC | Fair Value |  |  |  |  |  |  |
Fair Value of Financial Instruments |  |  |  |  |  |  |
Long-term debt-GSWC | 559,752,000 |  | $ 559,752,000 |  |  |  |
GSWC | Fair Value | Level 2 |  |  |  |  |  |  |
Fair Value of Financial Instruments |  |  |  |  |  |  |
Long-term debt-GSWC |  | $ 490,852,000 |  |  |  |  |
GSWC | Minimum |  |  |  |  |  |  |
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 |  |  |  |  |  |  |
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 | Common Stock [Member] |  |  |  |  |  |  |
Related Party Transactions |  |  |  |  |  |  |
Exercise of stock options and other issuance of Common Shares |  | $ 60,000,000 |  |  |  |  |
Stock Issued During Period, Shares, New Issues | shares |  | 0 | 5 |  |  |  |
Bear Valley Electric Service, Inc. |  |  |  |  |  |  |
Related Party Transactions |  |  |  |  |  |  |
Related Party Transaction, Amounts of Transaction | 1,300,000 | $ 2,800,000 |  |  |  |  |
Regulatory Asset CEMA |  | 302,000 |  |  |  |  |
Interest |  |  |  |  |  |  |
Public Utilities, Allowance for Funds Used During Construction, Additions |  | 216,000 | $ 200,000 |  |  |  |
Fair Value of Financial Instruments |  |  |  |  |  |  |
Notes Payable |  | 31,000,000 |  |  |  |  |
Notes Payable |  | 31,000,000 |  |  |  |  |
Bear Valley Electric Service, Inc. | Subsequent Event |  |  |  |  |  |  |
Fair Value of Financial Instruments |  |  |  |  |  |  |
Relief funding |  |  |  |  | $ 321,000 |  |
Parent |  |  |  |  |  |  |
Related Party Transactions |  |  |  |  |  |  |
Line of credit facility, current borrowing capacity |  | 30,000,000 |  |  |  |  |
Notes receivable, related parties | $ 6,000,000 | 26,000,000 | $ 6,000,000 |  |  |  |
Notes payable, related parties |  | $ 0 |  |  |  |  |
Water: | GSWC |  |  |  |  |  |  |
Nature of Operations: |  |  |  |  |  |  |
Number of customers served | customer |  | 262,800 |  |  |  |  |
Electric: | Bear Valley Electric Service, Inc. |  |  |  |  |  |  |
Nature of Operations: |  |  |  |  |  |  |
Number of customers served | customer |  | 24,700 |  |  |  |  |
Contracted services: | American States Utility Services |  |  |  |  |  |  |
Nature of Operations: |  |  |  |  |  |  |
Period of fixed price contracts to operate and maintain the water and/or wastewater systems at various military bases |  | 50 years |  |  |  |  |

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