Consolidated Statements of Comprehensive Income - Parenthetical - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Reclassification adjustment for loss on derivative instruments included in net income, tax	$ 36	$ 53	$ (213)	$ 109
Amortization of postretirement liability losses included in net periodic benefit cost, tax	89	145	189	300
Foreign currency translation adjustments recognized during the period, tax	0	(13)	0	(14)
Reclassification of foreign currency translation adjustment	0	75	0	75
Net unrealized gain (loss) on available-for-sale investments arising during the period, tax	21	(12)	31	(39)
Reclassification adjustment for loss on available-for-sale investments included in net income, tax	$ 3	$ 10	$ 10	$ 17

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.

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