Consolidated Statements Of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	$ 0	$ 173	$ 0	$ 230
Net income	14,722	44,204	32,887	47,906
Other comprehensive income (loss):
Foreign currency translation adjustment	(10,811)	(1,958)	(8,905)	2,674
Derivative financial instruments adjustment	(905)	(412)	(1,190)	(38)
Amortization of prior service costs and net gains or losses	2,611	1,950	5,223	3,900
Other comprehensive income (loss)	(9,105)	(420)	(4,872)	6,536
Comprehensive income (loss)	5,617	43,784	28,015	54,442
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax	164	(248)	20	(24)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax	$ 761	$ 1,111	$ 1,523	$ 2,222