Accumulated Other Comprehensive Loss (Components of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	$ 933,900
Net current-period other comprehensive income (loss)	(8,144)	$ (4,589)
Balance, end of period	937,809	868,322
AOCI, pension and other postretirement benefit plans, tax benefits (expense)	2,349	9,938	$ 2,368	$ 9,984
AOCI, cumulative changes in net gain (loss) from cash flow hedges, tax benefit (expense)	656	37	$ 282	$ (106)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	(35,478)	(30,488)
Other comprehensive loss before reclassifications	(6,894)	(4,257)
Amounts reclassified from accumulated other comprehensive loss	0	0
Net current-period other comprehensive income (loss)	(6,894)	(4,257)
Balance, end of period	(42,372)	(34,745)
Pension and Other Postretirement Benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	(10,455)	(48,700)
Other comprehensive loss before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive loss	66	156
Net current-period other comprehensive income (loss)	66	156
Balance, end of period	(10,389)	(48,544)
Derivative Instrument Designated as Cash Flow Hedge
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	(972)	354
Other comprehensive loss before reclassifications	(1,249)	(394)
Amounts reclassified from accumulated other comprehensive loss	(67)	(94)
Net current-period other comprehensive income (loss)	(1,316)	(488)
Balance, end of period	(2,288)	(134)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	(46,905)	(78,834)
Other comprehensive loss before reclassifications	(8,143)	(4,651)
Amounts reclassified from accumulated other comprehensive loss	(1)	62
Net current-period other comprehensive income (loss)	(8,144)	(4,589)
Balance, end of period	$ (55,049)	$ (83,423)