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Electric utility segment - Power Purchase Agreements (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Regulatory Projects and Legal Obligations [Line Items] |  |  |
Purchased power | $ 587 | $ 563 | $ 594
Kalaeloa Partners, L.P. (Kalaeloa) |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |
Purchased power | 180 | 152 | 187
AES Hawaii, Inc. (AES Hawaii) |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |
Purchased power | 140 | 149 | 134
HPOWER |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |
Purchased power | 67 | 71 | 66
Puna Geothermal Venture |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |
Purchased power | 38 | 28 | 29
Hamakua Energy Partners, L.P. (HEP) |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |
Purchased power | 35 | 29 | 44
Hawaiian Commercial & Sugar (HC&S) |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |
Purchased power | 0 | 1 | 8
Other IPPs |  |  |
Regulatory Projects and Legal Obligations [Line Items] |  |  |
Purchased power | $ 127 | $ 133 | $ 126

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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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