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Electric utility segment - Power purchase agreements (Details) - USD ($) $ in Thousands | 3 Months Ended
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Mar. 31, 2018 | Mar. 31, 2017
Regulatory Projects and Legal Obligations [Line Items] |  |
Purchased power | $ 140,000 | $ 127,000
Hawaiian Electric Company |  |
Regulatory Projects and Legal Obligations [Line Items] |  |
Purchased power | 107,370 | 100,147
Hawaiian Electric Company | Kalaeloa Partners, L.P. (Kalaeloa) |  |
Regulatory Projects and Legal Obligations [Line Items] |  |
Purchased power | 40,000 | 40,000
Hawaiian Electric Company | AES Hawaii |  |
Regulatory Projects and Legal Obligations [Line Items] |  |
Purchased power | 37,000 | 29,000
Hawaiian Electric Company | HPOWER |  |
Regulatory Projects and Legal Obligations [Line Items] |  |
Purchased power | 15,000 | 17,000
Hawaiian Electric Company | Puna Geothermal Venture |  |
Regulatory Projects and Legal Obligations [Line Items] |  |
Purchased power | 11,000 | 8,000
Hawaiian Electric Company | Hamakua Energy Partners, L.P. (HEP) |  |
Regulatory Projects and Legal Obligations [Line Items] |  |
Purchased power | 7,000 | 7,000
Hawaiian Electric Company | Other IPPs |  |
Regulatory Projects and Legal Obligations [Line Items] |  |
Purchased power | $ 30,000 | $ 26,000

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- Definition Amount of operating expense for purchased power of regulated operation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.2(b)) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 + Details
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