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Summary of Significant Accounting Policies - Property, Plant and Equipment and Intangible Assets (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Major components of depreciable plant and equipment [Abstract] |  |  |
Source of supply | $ 207,537 | $ 191,082 |
Pumping plant | 284,308 | 269,246 |
Water treatment plant | 354,617 | 327,492 |
Transmission and distribution plant | 2,820,358 | 2,615,640 |
General plant | 301,091 | 257,825 |
Total depreciable plant and equipment | $ 3,967,911 | $ 3,661,285 |
Useful Lives |  |  |
Depreciation expense as percentage of beginning of year balance of depreciable plant | 2.90% | 3.30% | 3.20%
Capitalized interest costs | $ 2,900 | $ 4,703 | $ 4,422
Equity funds capitalized | 2,114 | 1,551 | 1,926
Water Plant |  |  |
Useful Lives |  |  |
Depreciation | $ 104,325 | $ 99,413 | $ 91,906
Minimum |  |  |
Useful Lives |  |  |
Source of supply | 20 years |  |
Pumping plant | 5 years |  |
Water treatment plant | 5 years |  |
Transmission and distribution plant | 10 years |  |
General plant | 4 years |  |
Useful life of intangible assets | 5 years |  |
Maximum |  |  |
Useful Lives |  |  |
Source of supply | 100 years |  |
Pumping plant | 70 years |  |
Water treatment plant | 50 years |  |
Transmission and distribution plant | 100 years |  |
General plant | 61 years |  |
Useful life of intangible assets | 70 years |  |

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