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Segment and Non-Tariffed Businesses Reporting (Details) $ in Thousands | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Dec. 31, 2020 USD ($) | Sep. 30, 2020 USD ($) | Jun. 30, 2020 USD ($) | Mar. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Sep. 30, 2019 USD ($) | Jun. 30, 2019 USD ($) | Mar. 31, 2019 USD ($) | Dec. 31, 2020 USD ($) reportable_segment subsidiary | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Number of subsidiaries | subsidiary |  |  |  |  |  |  |  |  | 4 |  |  |
Number of reportable segments | reportable_segment |  |  |  |  |  |  |  |  | 2 |  |  |
Operating revenue | $ 135,700 | $ 165,863 | $ 147,209 | $ 115,754 | $ 125,838 | $ 113,997 | $ 102,965 | $ 77,682 | $ 564,526 | $ 420,482 | $ 397,699 |
Operating expense |  |  |  |  |  |  |  |  | 446,856 | 363,003 | 324,259 |
Operating income (loss) | 24,290 | 41,883 | 36,070 | 15,427 | 6,016 | 17,084 | 21,971 | 12,408 | 117,670 | 57,479 | 73,440 |
Net income (loss) | 13,284 | $ 26,093 | $ 19,721 | $ 2,417 | (5,486) | $ 9,478 | $ 13,538 | $ 5,873 | 61,515 | 23,403 | 38,767 |
Depreciation and amortization |  |  |  |  |  |  |  |  | 89,279 | 65,592 | 54,601 |
Senior note and other interest expense |  |  |  |  |  |  |  |  | 54,255 | 31,796 | 24,332 |
Provision for income taxes |  |  |  |  |  |  |  |  | 8,380 | 8,454 | 10,065 |
Assets | 3,311,465 |  |  |  | 3,132,470 |  |  |  | 3,311,465 | 3,132,470 |  | $ 1,956,389
Regulated | Water Utility Services |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Operating revenue |  |  |  |  |  |  |  |  | 548,013 | 407,116 | 384,639 |
Operating expense |  |  |  |  |  |  |  |  | 431,375 | 329,520 | 294,536 |
Operating income (loss) |  |  |  |  |  |  |  |  | 116,638 | 77,596 | 90,103 |
Net income (loss) |  |  |  |  |  |  |  |  | 69,245 | 42,691 | 53,181 |
Depreciation and amortization |  |  |  |  |  |  |  |  | 86,758 | 63,775 | 53,067 |
Senior note and other interest expense |  |  |  |  |  |  |  |  | 33,877 | 25,073 | 22,157 |
Provision for income taxes |  |  |  |  |  |  |  |  | 16,563 | 8,382 | 14,826 |
Assets | 3,197,626 |  |  |  | 3,016,846 |  |  |  | 3,197,626 | 3,016,846 |  | 1,492,954
Regulated | SJW Corp. |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Operating revenue |  |  |  |  |  |  |  |  | 548,013 | 407,116 | 384,639 |
Operating expense |  |  |  |  |  |  |  |  | 431,375 | 329,520 | 294,536 |
Operating income (loss) |  |  |  |  |  |  |  |  | 116,638 | 77,596 | 90,103 |
Net income (loss) |  |  |  |  |  |  |  |  | 69,245 | 42,691 | 53,181 |
Depreciation and amortization |  |  |  |  |  |  |  |  | 86,758 | 63,775 | 53,067 |
Senior note and other interest expense |  |  |  |  |  |  |  |  | 33,877 | 25,073 | 22,157 |
Provision for income taxes |  |  |  |  |  |  |  |  | 16,563 | 8,382 | 14,826 |
Assets | 3,197,626 |  |  |  | 3,016,846 |  |  |  | 3,197,626 | 3,016,846 |  | 1,492,954
Non- tariffed | Water Utility Services |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Operating revenue |  |  |  |  |  |  |  |  | 10,981 | 7,969 | 7,578 |
Operating expense |  |  |  |  |  |  |  |  | 6,943 | 5,443 | 5,012 |
Operating income (loss) |  |  |  |  |  |  |  |  | 4,038 | 2,526 | 2,566 |
Net income (loss) |  |  |  |  |  |  |  |  | 4,099 | 2,019 | 1,848 |
Depreciation and amortization |  |  |  |  |  |  |  |  | 442 | 420 | 338 |
Senior note and other interest expense |  |  |  |  |  |  |  |  | 0 | 0 | 0 |
Provision for income taxes |  |  |  |  |  |  |  |  | 998 | 708 | 719 |
Assets | 8,869 |  |  |  | 5,507 |  |  |  | 8,869 | 5,507 |  | 4,489
Non- tariffed | Real Estate Services |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Operating revenue |  |  |  |  |  |  |  |  | 5,532 | 5,397 | 5,482 |
Operating expense |  |  |  |  |  |  |  |  | 3,510 | 3,751 | 3,539 |
Operating income (loss) |  |  |  |  |  |  |  |  | 2,022 | 1,646 | 1,943 |
Net income (loss) |  |  |  |  |  |  |  |  | 1,455 | 1,623 | 885 |
Depreciation and amortization |  |  |  |  |  |  |  |  | 1,186 | 1,196 | 1,196 |
Senior note and other interest expense |  |  |  |  |  |  |  |  | 0 | 0 | 0 |
Provision for income taxes |  |  |  |  |  |  |  |  | 467 | 486 | 903 |
Assets | 44,405 |  |  |  | 46,778 |  |  |  | 44,405 | 46,778 |  | 46,517
Non- tariffed | All Other |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Operating revenue |  |  |  |  |  |  |  |  | 0 | 0 | 0 |
Operating expense |  |  |  |  |  |  |  |  | 5,028 | 24,289 | 21,172 |
Operating income (loss) |  |  |  |  |  |  |  |  | (5,028) | (24,289) | (21,172) |
Net income (loss) |  |  |  |  |  |  |  |  | (13,284) | (22,930) | (17,147) |
Depreciation and amortization |  |  |  |  |  |  |  |  | 893 | 201 | 0 |
Senior note and other interest expense |  |  |  |  |  |  |  |  | 20,378 | 6,723 | 2,175 |
Provision for income taxes |  |  |  |  |  |  |  |  | (9,648) | (1,122) | (6,383) |
Assets | 60,565 |  |  |  | 63,339 |  |  |  | 60,565 | 63,339 |  | 412,429
Non- tariffed | SJW Corp. |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Operating revenue |  |  |  |  |  |  |  |  | 16,513 | 13,366 | 13,060 |
Operating expense |  |  |  |  |  |  |  |  | 15,481 | 33,483 | 29,723 |
Operating income (loss) |  |  |  |  |  |  |  |  | 1,032 | (20,117) | (16,663) |
Net income (loss) |  |  |  |  |  |  |  |  | (7,730) | (19,288) | (14,414) |
Depreciation and amortization |  |  |  |  |  |  |  |  | 2,521 | 1,817 | 1,534 |
Senior note and other interest expense |  |  |  |  |  |  |  |  | 20,378 | 6,723 | 2,175 |
Provision for income taxes |  |  |  |  |  |  |  |  | (8,183) | 72 | $ (4,761) |
Assets | $ 113,839 |  |  |  | $ 115,624 |  |  |  | $ 113,839 | $ 115,624 |  | $ 463,435

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