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Condensed Consolidated Statements of Comprehensive Income (unaudited) (Parenthetical) - USD ($) $ in Thousands | 3 Months Ended
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Mar. 31, 2021 | Mar. 31, 2020
Net unrealized gains on available-for-sale investment securities: |  |
Net unrealized gains (losses) on available-for-sale investment securities arising during the period, tax | $ (16,616) | $ 7,120
Reclassification adjustment for net realized gains included in net income, tax | (142) | 0
Derivatives qualifying as cash flow hedges: |  |
Unrealized interest rate hedging arising during the period, tax | 542 | (619)
Retirement benefit plans: |  |
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, tax | 2,084 | 1,986
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, tax | (2,015) | (1,789)
Hawaiian Electric Company, Inc. and Subsidiaries |  |
Retirement benefit plans: |  |
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, tax | 2,027 | 1,798
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, tax | $ (2,015) | $ (1,789)

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- Definition The amount of income taxes on the reclassification adjustments on pension and post retirement benefits for the accounting impact of the decisions issued by the Public Utilities Commission. + References No definition available. + Details
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- Definition Amount, before reclassification, of tax expense (benefit) for gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=121641772&loc=d3e640-108580 + Details
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- Definition Amount, before adjustment, of tax expense (benefit) for unrealized holding gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). Excludes tax expense (benefit) for unrealized gain (loss) on investment in debt security measured at amortized cost (held-to-maturity) from transfer to available-for-sale. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=121641772&loc=d3e640-108580 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669646-108580 + Details
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