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Shareholders' equity - Reclassification out of AOCI (Details) - USD ($) $ in Thousands | 3 Months Ended
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Mar. 31, 2018 | Mar. 31, 2017
Reclassifications out of accumulated other comprehensive income/(loss) |  |
Total reclassifications | $ 524 | $ 762
Hawaiian Electric Company, Inc. and Subsidiaries |  |
Reclassifications out of accumulated other comprehensive income/(loss) |  |
Total reclassifications | 31 | 459
Amortization of prior service credit and net losses recognized during the period in net periodic benefit cost |  |
Reclassifications out of accumulated other comprehensive income/(loss) |  |
Total reclassifications | 5,146 | 3,921
Amortization of prior service credit and net losses recognized during the period in net periodic benefit cost | Hawaiian Electric Company, Inc. and Subsidiaries |  |
Reclassifications out of accumulated other comprehensive income/(loss) |  |
Total reclassifications | 4,653 | 3,618
Impact of D&Os of the PUC included in regulatory assets |  |
Reclassifications out of accumulated other comprehensive income/(loss) |  |
Total reclassifications | (4,622) | (3,613)
Impact of D&Os of the PUC included in regulatory assets | Hawaiian Electric Company, Inc. and Subsidiaries |  |
Reclassifications out of accumulated other comprehensive income/(loss) |  |
Total reclassifications | (4,622) | (3,613)
Reclassification out of Accumulated Other Comprehensive Income | Unrealized gains (losses) on derivatives | Forward commitments | Hawaiian Electric Company, Inc. and Subsidiaries |  |
Reclassifications out of accumulated other comprehensive income/(loss) |  |
Total reclassifications | 0 | 454
Reclassification out of Accumulated Other Comprehensive Income | Unrealized gains (losses) on derivatives | Electric utility | Forward commitments |  |
Reclassifications out of accumulated other comprehensive income/(loss) |  |
Total reclassifications | $ 0 | $ 454

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- Definition Amount after tax of reclassification adjustments of other comprehensive income (loss). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=66004124&loc=SL7669686-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 55 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=66004921&loc=d3e1436-108581 + Details
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