Accumulated Other Comprehensive Loss (Components of Accumulated Other Comprehensive Income or Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ 848,324	$ 766,573
Other comprehensive income (loss) before reclassifications	(12,240)	(13,664)
Amounts reclassified to earnings	44,169	(15)
Net other comprehensive income (loss) for period	31,929	(13,679)
Ending Balance	933,900	848,324
AOCI, Pension and other postretirement benefit plans, tax	2,368	9,984
AOCI, cumulative changes in net gain (loss) from cash flow hedges, tax	282	(106)	$ (15)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(30,488)	(17,983)
Other comprehensive income (loss) before reclassifications	(4,990)	(12,505)
Amounts reclassified to earnings	0	0
Net other comprehensive income (loss) for period	(4,990)	(12,505)
Ending Balance	(35,478)	(30,488)
Pension and Other Postretirement Benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(48,700)	(47,198)
Other comprehensive income (loss) before reclassifications	(6,079)	(1,678)
Amounts reclassified to earnings	44,324	176
Net other comprehensive income (loss) for period	38,245	(1,502)
Ending Balance	(10,455)	(48,700)
Derivative Instrument Designated as Cash Flow Hedge
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance		26
Other comprehensive income (loss) before reclassifications		519
Amounts reclassified to earnings		(191)
Net other comprehensive income (loss) for period		328
Derivative Instrument Designated as Cash Flow Hedge
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	354
Other comprehensive income (loss) before reclassifications	(1,171)
Amounts reclassified to earnings	(155)
Net other comprehensive income (loss) for period	(1,326)
Ending Balance	(972)	354
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(78,834)	(65,155)
Ending Balance	$ (46,905)	$ (78,834)