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Property, Plant And Equipment (Tables) | 12 Months Ended
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Dec. 31, 2020
Property Plant And Equipment [Abstract] |
Schedule of Net Utility Property | Net utility property consisted of the following as of December 31 (dollars in thousands):
|  | 2020 |  |  | 2019 |
Utility plant in service |  | $ | 6,809,797 |  |  | $ | 6,462,993 |
Construction work in progress |  |  | 175,767 |  |  |  | 164,941 |
Total |  |  | 6,985,564 |  |  |  | 6,627,934 |
Less: Accumulated depreciation and amortization |  |  | 1,993,952 |  |  |  | 1,830,927 |
Total net utility property |  | $ | 4,991,612 |  |  | $ | 4,797,007 |
Summary of Ratio of Depreciation to Average Depreciable Property and Average Service Lives for Utility Plan in Service | For utility operations, the ratio of depreciation provisions to average depreciable property was as follows for the years ended December 31:
|  | 2020 |  |  | 2019 |  |  | 2018 |
Avista Utilities |  |  |  |  |  |  |  |  |  |  |  |
Ratio of depreciation to average depreciable property |  |  | 3.43 | % |  |  | 3.28 | % |  |  | 3.17 | %
Alaska Electric Light and Power Company |  |  |  |  |  |  |  |  |  |  |  |
Ratio of depreciation to average depreciable property |  |  | 2.77 | % |  |  | 2.48 | % |  |  | 2.46 | %
The average service lives for the following broad categories of utility plant in service are (in years):
|  | Avista Utilities |  |  | Alaska Electric Light and Power Company |
Electric thermal/other production |  |  | 27 |  |  |  | 42 |
Hydroelectric production |  |  | 81 |  |  |  | 42 |
Electric transmission |  |  | 49 |  |  |  | 43 |
Electric distribution |  |  | 39 |  |  |  | 40 |
Natural gas distribution property |  |  | 44 |  |  | N/A |
Other shorter-lived general plant |  |  | 8 |  |  |  | 18 |
The gross balances of the major classifications of property, plant and equipment are detailed in the following table as of December 31 (dollars in thousands):
|  | 2020 |  |  | 2019 |
Avista Utilities: |  |  |  |  |  |  |  |
Electric production |  | $ | 1,457,497 |  |  | $ | 1,445,017 |
Electric transmission |  |  | 862,987 |  |  |  | 802,546 |
Electric distribution |  |  | 1,978,868 |  |  |  | 1,847,273 |
Electric construction work-in-progress (CWIP) and other |  |  | 384,372 |  |  |  | 350,331 |
Electric total |  |  | 4,683,724 |  |  |  | 4,445,167 |
Natural gas underground storage |  |  | 53,351 |  |  |  | 51,017 |
Natural gas distribution |  |  | 1,282,563 |  |  |  | 1,203,186 |
Natural gas CWIP and other |  |  | 83,644 |  |  |  | 81,245 |
Natural gas total |  |  | 1,419,558 |  |  |  | 1,335,448 |
Common plant (including CWIP) |  |  | 712,609 |  |  |  | 681,711 |
Total Avista Utilities |  |  | 6,815,891 |  |  |  | 6,462,326 |
AEL&P: |  |  |  |  |  |  |  |
Electric production |  |  | 105,076 |  |  |  | 100,448 |
Electric transmission |  |  | 22,419 |  |  |  | 22,000 |
Electric distribution |  |  | 25,814 |  |  |  | 24,096 |
Electric CWIP and other |  |  | 6,677 |  |  |  | 9,539 |
Electric total |  |  | 159,986 |  |  |  | 156,083 |
Common plant |  |  | 9,687 |  |  |  | 9,525 |
Total AEL&P |  |  | 169,673 |  |  |  | 165,608 |
Total gross utility property |  |  | 6,985,564 |  |  |  | 6,627,934 |
Other (1) |  |  | 16,394 |  |  |  | 28,195 |
Total |  | $ | 7,001,958 |  |  | $ | 6,656,129 |
(1) | Included in other property and investments-net and other non-current assets on the Consolidated Balance Sheets. Accumulated depreciation was $2.2 million as of December 31, 2020 and $5.4 million as of December 31, 2019 for the other businesses.

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- Definition Tabular disclosure of public utility physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, balances by class of assets, deprecation expense and method used, including composite depreciation, and accumulated deprecation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=84167750&loc=d3e42232-110370 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.13(b)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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