EQUITY ROLL FORWARD (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Common Stock, Dividends, Per Share, Cash Paid	$ 0.1450	$ 0.1200	$ 0.2900	$ 0.2275
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance			$ 735,827
Net income	$ 32,812	$ 30,039	41,939	$ 51,254
Equity, ending balance	760,902		760,902
Temporary equity, beginning balance	408	1,360	518	1,502
Net income	(180)	(648)	(283)	(802)
Currency translation adjustment	(485)	0	(485)	0
Temporary Equity, Foreign Currency Translation Adjustments	47	52	40	64
Temporary equity, ending balance	(210)	764	(210)	764
Common Stock
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	4,637	4,652	4,632	4,663
Stock Issued During Period, Value, New Issues	1	6	7	9
Stock Repurchased and Retired During Period, Value	(12)	(7)	(21)	(27)
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	6	3	14	9
Equity, ending balance	4,632	4,654	4,632	4,654
Additional Paid in Capital
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	262,002	244,095	257,535	240,136
Stock Issued During Period, Value, New Issues	243	1,147	1,488	1,786
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	2,288	1,440	5,510	4,760
Equity, ending balance	264,533	246,682	264,533	246,682
Retained Earnings
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	652,737	613,113	654,724	604,905
Net income	32,745	30,497	41,801	51,671
Dividends, Common Stock, Cash	(6,787)	(5,621)	(13,510)	(10,658)
Stock Repurchased and Retired During Period, Value	(5,202)	(2,997)	(9,522)	(10,926)
Equity, ending balance	673,493	634,992	673,493	634,992
Minimum Pension Liability
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	(48,076)	(48,763)	(48,585)	(49,364)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	508	598	1,017	1,199
Equity, ending balance	(47,568)	(48,165)	(47,568)	(48,165)
Cumulative Translation Adjustment
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	(137,205)	(92,740)	(134,434)	(99,683)
Currency translation adjustment	1,303	(32,725)	(1,468)	(25,782)
Equity, ending balance	(135,902)	(125,465)	(135,902)	(125,465)
Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	2,097	2,199	1,955	1,964
Net income	247	190	421	385
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	(642)	0	(642)	0
Currency translation adjustment	12	(63)	(20)	(23)
Equity, ending balance	1,714	2,326	1,714	2,326
Total Equity
Increase (Decrease) in Stockholders' Equity
Equity, beginning balance	736,192	722,556	735,827	702,621
Net income	32,992	30,687	42,222	52,056
Dividends, Common Stock, Cash	(6,787)	(5,621)	(13,510)	(10,658)
Stock Issued During Period, Value, New Issues	244	1,153	1,495	1,795
Stock Repurchased and Retired During Period, Value	(5,214)	(3,004)	(9,543)	(10,953)
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	2,294	1,443	5,524	4,769
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	(642)	0	(642)	0
Currency translation adjustment	1,315	(32,788)	(1,488)	(25,805)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	508	598	1,017	1,199
Equity, ending balance	$ 760,902	$ 715,024	$ 760,902	$ 715,024