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Employee Benefit Plans Employee Benefit Plans 5 (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Pension Benefits |  |  |
Employee benefit plans |  |  |
Regulatory adjustment - over collection | $ (465) | $ (859) | $ (523)
GSWC | Pension Benefits |  |  |
Employee benefit plans |  |  |
Regulatory adjustment - over collection | (583) | $ (859) | $ (523)
Pension Costs and Other Postretirement Benefit Costs | GSWC |  |  |
Employee benefit plans |  |  |
Regulatory asset authorized under settlement | 34,700 |  |
Two-way pension balancing account | Pension Costs and Other Postretirement Benefit Costs | GSWC |  |  |
Employee benefit plans |  |  |
Regulatory asset authorized under settlement | $ 1,700 |  |

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- Definition The increase (decrease) during the reporting period in the value of other assets that are created when regulatory agencies permits public utilities to defer costs to the balance sheet. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585 + Details
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- Definition The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
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