Consolidated Statements Of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	$ 0	$ 0
Net income	19,785	18,164
Other comprehensive income (loss):
Foreign currency translation adjustment	(790)	1,906
Derivative financial instruments adjustment	(353)	(285)
Amortization of prior service costs and net gains or losses	2,079	2,612
Other comprehensive income (loss)	936	4,233
Comprehensive income (loss)	20,721	22,397
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax	83	(144)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax	$ 592	$ 762

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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