EMPLOYEE BENEFITS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance at beginning of year	$ 180,749
Exchange Rate Impact	3	$ 0
Balance at end of year	202,348	180,749
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Pension and postretirement liabilities	(49,122)	(58,840)
Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	235,826	234,350
Service cost	1,949	2,178	$ 1,953
Interest cost	6,019	6,624	6,676
Plan participants' contributions	1,581	1,516
Plan participants' contributions	1,581	1,516
Actuarial loss (gain)	5,769	7,117
Foreign currency impact	6,437	(4,686)
Benefits and administrative expenses paid	(9,514)	(8,579)
Settlements	(921)	(2,694)
Benefit obligation at end of year	247,146	235,826	234,350
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance at beginning of year	180,748	180,007
Actual return on plan assets	20,099	10,347
Employer contributions	4,618	4,214
Exchange Rate Impact	5,737	(4,063)
Benefits and administrative expenses paid	(9,514)	(8,579)
Settlements	(921)	(2,694)
Balance at end of year	202,348	180,748	180,007
Funded status of plans	(44,798)	(55,078)
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Non-current assets	2,956	2,387
Current liabilities	(264)	(260)
Pension and postretirement liabilities	(47,490)	(57,205)
Net amount recognized	(44,798)	(55,078)
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax [Abstract]
Net actuarial (loss) gain	(72,842)	(80,837)
Prior service credit	1,228	1,474
Accumulated other comprehensive (loss) income	(71,614)	(79,363)
Accumulated contributions in excess of net periodic benefit cost	26,816	24,285
Net amount recognized	(44,798)	(55,078)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	1,729	1,683
Service cost	12	11	12
Interest cost	73	76	74
Plan participants' contributions	283	292
Plan participants' contributions	283	292
Actuarial loss (gain)	(15)	67
Foreign currency impact	0	0
Benefits and administrative expenses paid	(381)	(400)
Settlements	0	0
Benefit obligation at end of year	1,701	1,729	1,683
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	98	108
Exchange Rate Impact	0	0
Benefits and administrative expenses paid	(381)	(400)
Settlements	0	0
Balance at end of year	0	0	$ 0
Funded status of plans	(1,701)	(1,729)
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Non-current assets	0	0
Current liabilities	(105)	(126)
Pension and postretirement liabilities	(1,596)	(1,603)
Net amount recognized	(1,701)	(1,729)
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax [Abstract]
Net actuarial (loss) gain	552	581
Prior service credit	0	0
Accumulated other comprehensive (loss) income	552	581
Accumulated contributions in excess of net periodic benefit cost	(2,253)	(2,310)
Net amount recognized	$ (1,701)	$ (1,729)