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Other related-party transactions (Details) - Affiliated Entity - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Hawaii Medical Service Association (HMSA) | Gross costs |  |  |
Related Party Transaction [Line Items] |  |  |
Expenses from related party transactions | $ 28 | $ 28 | $ 30
Hawaii Medical Service Association (HMSA) | Gross costs | Hawaiian Electric Company, Inc. and Subsidiaries |  |  |
Related Party Transaction [Line Items] |  |  |
Expenses from related party transactions | 23 | 22 | 23
Hawaii Medical Service Association (HMSA) | Net expense |  |  |
Related Party Transaction [Line Items] |  |  |
Expenses from related party transactions | 19 | 20 | 21
Hawaii Medical Service Association (HMSA) | Net expense | Hawaiian Electric Company, Inc. and Subsidiaries |  |  |
Related Party Transaction [Line Items] |  |  |
Expenses from related party transactions | 14 | 14 | 14
Hawaii Dental Service (HDS) | Gross costs |  |  |
Related Party Transaction [Line Items] |  |  |
Expenses from related party transactions | 3 | 3 | 3
Hawaii Dental Service (HDS) | Gross costs | Hawaiian Electric Company, Inc. and Subsidiaries |  |  |
Related Party Transaction [Line Items] |  |  |
Expenses from related party transactions | 2 | 2 | 2
Hawaii Dental Service (HDS) | Net expense |  |  |
Related Party Transaction [Line Items] |  |  |
Expenses from related party transactions | 2 | 2 | 2
Hawaii Dental Service (HDS) | Net expense | Hawaiian Electric Company, Inc. and Subsidiaries |  |  |
Related Party Transaction [Line Items] |  |  |
Expenses from related party transactions | $ 1 | $ 1 | $ 1

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- Definition Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Details
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