Consolidated Statements Of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 14,477	$ 14,722	$ 34,261	$ 32,887
Other comprehensive income (loss):
Foreign currency translation adjustment	507	(10,811)	(283)	(8,905)
Derivative financial instruments adjustment	621	(905)	268	(1,190)
Amortization of prior service costs and net gains or losses	2,079	2,611	4,158	5,223
Other comprehensive income (loss)	3,207	(9,105)	4,143	(4,872)
Comprehensive income (loss)	$ 17,684	$ 5,617	$ 38,404	$ 28,015