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Consolidated Statements of Comprehensive Income - Parenthetical - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Reclassification adjustment for loss on derivative instruments included in net income, tax | $ (140) | $ 429 | $ 224
Postretirement liability gains (losses) arising during the period, tax | (2,012) | 1,471 | (1,162)
Amortization of postretirement liability losses included in net periodic benefit cost, tax | 476 | 721 | 645
Reclassification of postretirement liability adjustment from regulatory asset, tax | 0 | 0 | (876)
Foreign currency translation adjustment recognized during the period, tax | 0 | (14) | (3)
Reclassification adjustment for foreign currency translation adjustment included in net income, tax | 0 | 75 | 0
Net unrealized gain (loss) on available-for-sale investments arising during the period, tax | 35 | (38) | (75)
Reclassification adjustment for loss on available-for-sale investments included in net income, tax | $ 10 | $ 35 | $ 65

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- Definition Amount of tax expense (benefit), before reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118930883&loc=SL7669646-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 45 -Paragraph 20 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=118261656&loc=d3e32211-110900 Reference 3: 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=118930883&loc=d3e640-108580 + Details
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