EQUITY ROLL FORWARD (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Common Stock, Dividends, Per Share, Cash Paid	$ 0.1450	$ 0.1200	$ 0.4350	$ 0.3475
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance			$ 735,827
Net income	$ 34,075	$ 29,932	76,014	$ 81,186
Equity, ending balance	777,056		777,056
Temporary equity, beginning balance	(210)	764	518	1,502
Net income	(31)	(216)	(314)	(1,018)
Purchase of redeemable noncontrolling shares	(2)	0	(487)	0
Temporary Equity, Foreign Currency Translation Adjustments	14	68	54	132
Temporary equity, ending balance	(229)	616	(229)	616
Common Stock
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	4,632	4,654	4,632	4,663
Stock Issued During Period, Value, New Issues	5	29	12	38
Stock Repurchased and Retired During Period, Value	(1)	(2)	(22)	(29)
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	0	1	14	10
Equity, ending balance	4,636	4,682	4,636	4,682
Additional Paid in Capital
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	264,533	246,682	257,535	240,136
Stock Issued During Period, Value, New Issues	831	6,923	2,319	8,709
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	1,935	1,857	7,445	6,617
Equity, ending balance	267,299	255,462	267,299	255,462
Retained Earnings
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	673,493	634,992	654,724	604,905
Net income	33,907	30,006	75,708	81,677
Dividends, Common Stock, Cash	(6,767)	(5,641)	(20,277)	(16,299)
Stock Repurchased and Retired During Period, Value	(757)	(1,125)	(10,279)	(12,051)
Equity, ending balance	699,876	658,232	699,876	658,232
Minimum Pension Liability
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	(47,568)	(48,165)	(48,585)	(49,364)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	475	598	1,492	1,797
Equity, ending balance	(47,093)	(47,567)	(47,093)	(47,567)
Cumulative Translation Adjustment
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	(135,902)	(125,465)	(134,434)	(99,683)
Currency translation adjustment	(13,622)	(10,794)	(15,090)	(36,576)
Equity, ending balance	(149,524)	(136,259)	(149,524)	(136,259)
Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	1,714	2,326	1,955	1,964
Net income	199	142	620	527
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	0	(661)	(642)	(661)
Currency translation adjustment	(51)	(12)	(71)	(35)
Equity, ending balance	1,862	1,795	1,862	1,795
Total Equity
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	760,902	715,024	735,827	702,621
Net income	34,106	30,148	76,328	82,204
Dividends, Common Stock, Cash	(6,767)	(5,641)	(20,277)	(16,299)
Stock Issued During Period, Value, New Issues	836	6,952	2,331	8,747
Stock Repurchased and Retired During Period, Value	(758)	(1,127)	(10,301)	(12,080)
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	1,935	1,858	7,459	6,627
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	0	(661)	(642)	(661)
Currency translation adjustment	(13,673)	(10,806)	(15,161)	(36,611)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	475	598	1,492	1,797
Equity, ending balance	$ 777,056	$ 736,345	$ 777,056	$ 736,345