Consolidated Statements of Comprehensive Income - Parenthetical - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Reclassification adjustment for loss on derivative instruments included in net income, tax	$ (249)	$ 56
Amortization of postretirement liability losses included in net periodic benefit cost (credit), tax	100	155
Foreign currency translation adjustments recognized during the period, tax	0	(1)
Net unrealized gain (loss) on available-for-sale investments arising during the period, tax	10	(28)
Reclassification adjustment for loss on available-for-sale investments included in net income, tax	$ 7	$ 7

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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