EQUITY ROLL FORWARD (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Common Stock, Dividends, Per Share, Cash Paid	$ 0.155	$ 0.145	$ 0.310	$ 0.290
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance			$ 798,669
Net income	$ 24,802	$ 32,812	35,594	$ 41,939
Equity, ending balance	775,511		775,511
Temporary equity, beginning balance	(245)	408	(236)	518
Net income	(18)	(180)	(56)	(283)
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	0	(485)	0	(485)
Temporary Equity, Foreign Currency Translation Adjustments	1	47	30	40
Temporary equity, ending balance	(262)	(210)	(262)	(210)
Common Stock
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	4,614	4,637	4,639	4,632
Stock Issued During Period, Value, New Issues	2	1	4	7
Stock Repurchased and Retired During Period, Value	(2)	(12)	(37)	(21)
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	4	6	12	14
Equity, ending balance	4,618	4,632	4,618	4,632
Additional Paid in Capital
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	274,869	262,002	269,656	257,535
Stock Issued During Period, Value, New Issues	647	243	1,516	1,488
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	2,659	2,288	7,003	5,510
Equity, ending balance	278,175	264,533	278,175	264,533
Retained Earnings
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	698,917	652,737	712,460	654,724
Net income	24,651	32,745	35,294	41,801
Dividends, Common Stock, Cash	(7,206)	(6,787)	(14,446)	(13,510)
Stock Repurchased and Retired During Period, Value	(741)	(5,202)	(17,687)	(9,522)
Equity, ending balance	715,621	673,493	715,621	673,493
Minimum Pension Liability
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	(49,373)	(48,076)	(50,089)	(48,585)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	716	508	1,432	1,017
Equity, ending balance	(48,657)	(47,568)	(48,657)	(47,568)
Cumulative Translation Adjustment
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	(177,848)	(137,205)	(140,121)	(134,434)
Currency translation adjustment	1,955	1,303	(35,772)	(1,468)
Equity, ending balance	(175,893)	(135,902)	(175,893)	(135,902)
Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	2,287	2,097	2,124	1,955
Net income	169	247	356	421
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	(830)	(642)	(830)	(642)
Currency translation adjustment	21	12	(3)	(20)
Equity, ending balance	1,647	1,714	1,647	1,714
Total Equity
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	753,466	736,192	798,669	735,827
Net income	24,820	32,992	35,650	42,222
Dividends, Common Stock, Cash	(7,206)	(6,787)	(14,446)	(13,510)
Stock Issued During Period, Value, New Issues	649	244	1,520	1,495
Stock Repurchased and Retired During Period, Value	(743)	(5,214)	(17,724)	(9,543)
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	2,663	2,294	7,015	5,524
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	(830)	(642)	(830)	(642)
Currency translation adjustment	1,976	1,315	(35,775)	(1,488)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	716	508	1,432	1,017
Equity, ending balance	$ 775,511	$ 760,902	$ 775,511	$ 760,902