Accumulated Other Comprehensive Loss (Components of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period			$ 933,900
Other comprehensive income (loss)	$ 6,390	$ 1,467	(1,754)	$ (3,122)
Balance, end of period	962,582	897,514	962,582	897,514
AOCI, pension and other postretirement benefit plans, tax benefits (expense)	2,172	9,893	2,172	9,893	$ 2,368	$ 9,984
AOCI, cumulative changes in net gain (loss) from cash flow hedges, tax benefit (expense)	598	278	598	278	$ 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			(1,265)	(2,075)
Amounts reclassified from accumulated other comprehensive loss			0	0
Other comprehensive income (loss)			(1,265)	(2,075)
Balance, end of period	(36,743)	(32,563)	(36,743)	(32,563)
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			626	0
Amounts reclassified from accumulated other comprehensive loss			85	313
Other comprehensive income (loss)			711	313
Balance, end of period	(9,744)	(48,387)	(9,744)	(48,387)
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			(866)	(1,204)
Amounts reclassified from accumulated other comprehensive loss			(334)	(156)
Other comprehensive income (loss)			(1,200)	(1,360)
Balance, end of period	(2,172)	(1,006)	(2,172)	(1,006)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	(55,049)	(83,423)	(46,905)	(78,834)
Other comprehensive loss before reclassifications			(1,505)	(3,279)
Amounts reclassified from accumulated other comprehensive loss			(249)	157
Other comprehensive income (loss)	6,390	1,467	(1,754)	(3,122)
Balance, end of period	$ (48,659)	$ (81,956)	$ (48,659)	$ (81,956)