CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Foreign currency translation adjustments, tax	$ 0	$ 0	$ 0
Unrealized (losses) gains on marketable securities arising during period, net of tax	1,659	(722)	1,903
Reclassification adjustment for losses (gains) included in net income, net of tax	(192)	(21)	(297)
Amortization of prior service (credit) cost included in net periodic pension and post-retirement expense/income, net of tax	$ (43)	$ (71)	$ (154)

Amount of tax (expense) benefit of reclassification adjustment from accumulated other comprehensive (income) loss for prior service cost (credit) of defined benefit plan.

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Amount of tax expense (benefit), after 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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Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

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Amount of tax expense (benefit) before reclassification adjustments of unrealized holding gain (loss) on available-for-sale securities.

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