Condensed Consolidated Statements of Changes in Retained Earnings, Accumulated Other Comprehensive Loss and Noncontrolling Interests - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			$ 801,898
Net income	$ 18,823	$ 28,034	80,362	$ 107,763
Pension and post-retirement plan adjustments, net of tax	3,701	3,058	11,070	9,250
Income attributable to noncontrolling interests	0	(200)	(448)	(668)
Preferred dividends	(10)	(10)	(30)	(30)
Ending balance	824,177		824,177
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	1,093,261	1,058,955	1,065,789	1,012,266
Net income	18,823	28,234	80,810	108,431
Income attributable to noncontrolling interests		(200)	(448)	(668)
Distributions to noncontrolling interests (Note 19)	(5,632)		(5,632)
Common dividends	(17,245)	(16,761)	(51,292)	(49,781)
Preferred dividends	(10)	(10)	(30)	(30)
Ending balance	1,089,197	1,070,218	1,089,197	1,070,218
Accumulated Other Comprehensive (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(179,145)	(225,210)	(182,397)	(214,003)
Foreign currency translation adjustments	(13,868)	15,520	(18,073)	(2,758)
Pension and post-retirement plan adjustments, net of tax	3,701	3,058	11,070	9,250
Unrealized net gains (losses) on available-for-sale securities	(11)	(74)	(15)	(12)
Reclassification from accumulated other comprehensive (loss) into net income (Note 6)				720
Income attributable to noncontrolling interests		(294)	92	(197)
Ending balance	(189,323)	(207,000)	(189,323)	(207,000)
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	8,349	7,144	7,993	6,773
Income attributable to noncontrolling interests		494	356	865
Acquisition of noncontrolling interest in consolidated subsidiaries (Note 19)	(8,349)		(8,349)
Ending balance	$ 0	$ 7,638	$ 0	$ 7,638