EQUITY ROLL FORWARD (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Common Stock, Dividends, Per Share, Cash Paid	$ 0.155	$ 0.145	$ 0.465	$ 0.435
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance			$ 798,669
Net income	$ 38,575	$ 34,075	74,169	$ 76,014
Equity, ending balance	812,442		812,442
Temporary equity, beginning balance	(262)	(210)	(236)	518
Net income	25	(31)	(31)	(314)
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	0	(2)	0	(487)
Temporary Equity, Foreign Currency Translation Adjustments	(14)	14	16	54
Temporary equity, ending balance	(251)	(229)	(251)	(229)
Common Stock
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	4,618	4,632	4,639	4,632
Stock Issued During Period, Value, New Issues	6	5	10	12
Stock Repurchased and Retired During Period, Value	(3)	(1)	(40)	(22)
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	(1)	0	11	14
Equity, ending balance	4,620	4,636	4,620	4,636
Additional Paid in Capital
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	278,175	264,533	269,656	257,535
Stock Issued During Period, Value, New Issues	1,488	831	3,004	2,319
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	1,298	1,935	8,301	7,445
Equity, ending balance	280,961	267,299	280,961	267,299
Retained Earnings
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	715,621	673,493	712,460	654,724
Net income	38,372	33,907	73,666	75,708
Dividends, Common Stock, Cash	(7,195)	(6,767)	(21,641)	(20,277)
Stock Repurchased and Retired During Period, Value	(1,364)	(757)	(19,051)	(10,279)
Equity, ending balance	745,434	699,876	745,434	699,876
Minimum Pension Liability
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	(48,657)	(47,568)	(50,089)	(48,585)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	774	475	2,206	1,492
Equity, ending balance	(47,883)	(47,093)	(47,883)	(47,093)
Cumulative Translation Adjustment
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	(175,893)	(135,902)	(140,121)	(134,434)
Currency translation adjustment	3,330	(13,622)	(32,442)	(15,090)
Equity, ending balance	(172,563)	(149,524)	(172,563)	(149,524)
Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	1,647	1,714	2,124	1,955
Net income	178	199	534	620
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	0	0	(830)	(642)
Currency translation adjustment	48	(51)	45	(71)
Equity, ending balance	1,873	1,862	1,873	1,862
Total Equity
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	775,511	760,902	798,669	735,827
Net income	38,550	34,106	74,200	76,328
Dividends, Common Stock, Cash	(7,195)	(6,767)	(21,641)	(20,277)
Stock Issued During Period, Value, New Issues	1,494	836	3,014	2,331
Stock Repurchased and Retired During Period, Value	(1,367)	(758)	(19,091)	(10,301)
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	1,297	1,935	8,312	7,459
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	0	0	(830)	(642)
Currency translation adjustment	3,378	(13,673)	(32,397)	(15,161)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	774	475	2,206	1,492
Equity, ending balance	$ 812,442	$ 777,056	$ 812,442	$ 777,056