Accumulated Other Comprehensive Loss (Components of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period			$ 1,020,755
Other comprehensive income (loss) before reclassifications			(10,501)	$ (1,505)
Amounts reclassified from accumulated other comprehensive loss			121	(249)
Other comprehensive income (loss)	$ 2,816	$ 6,390	(10,380)	(1,754)
Balance, end of period	1,076,662	962,582	1,076,662	962,582
AOCI, Pension and other postretirement benefit plans, tax	1,923	2,172	1,923	2,172	$ 1,951	$ 2,368
AOCI, cumulative changes in net gain (loss) from cash flow hedges, tax	0	598	0	598	$ 0	$ 282
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	(32,771)	(55,049)	(19,575)	(46,905)
Other comprehensive income (loss)	2,816	6,390	(10,380)	(1,754)
Balance, end of period	(29,955)	(48,659)	(29,955)	(48,659)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period			(10,571)	(35,478)
Other comprehensive income (loss) before reclassifications			(10,501)	(1,265)
Amounts reclassified from accumulated other comprehensive loss			0	0
Other comprehensive income (loss)			(10,501)	(1,265)
Balance, end of period	(21,072)	(36,743)	(21,072)	(36,743)
Pension and Other Postretirement Benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period			(9,004)	(10,455)
Other comprehensive income (loss) before reclassifications			0	626
Amounts reclassified from accumulated other comprehensive loss			121	85
Other comprehensive income (loss)			121	711
Balance, end of period	(8,883)	(9,744)	(8,883)	(9,744)
Derivative Instrument Designated as Cash Flow Hedge
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period			0	(972)
Other comprehensive income (loss) before reclassifications			0	(866)
Amounts reclassified from accumulated other comprehensive loss			0	(334)
Other comprehensive income (loss)			0	(1,200)
Balance, end of period	$ 0	$ (2,172)	$ 0	$ (2,172)