OTHER COMPREHENSIVE INCOME (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Pension and postretirement benefits [Abstract]
Amortization of net actuarial loss, Gross Amount	[1]	$ 591	$ 908	$ 1,159	$ 2,117
Amortization of net actuarial loss, Income Tax (Provision) Benefit	[1]	(143)	(347)	(281)	(810)
Amortization of net actuarial loss, Net Amount	[1]	448	561	878	1,307
Actuarial gains (losses), Gross Amount	[1]	(609)	22,014	(609)	22,014
Actuarial gains (losses), Income Tax (Provision) Benefit	[1]	148	(8,435)	148	(8,435)
Actuarial gains (losses), Net Amount	[1]	(461)	13,579	(461)	13,579
Foreign currency translation, Gross Amount		(429)	0	(9)	0
Foreign currency translation, Income Tax (Provision) Benefit		0	0	0	0
Foreign currency translation, Net Amount		(429)	0	(9)	0
Total other comprehensive income (loss), Gross Amount		(447)	22,922	541	24,131
Total other comprehensive income (loss), Income Tax (Provision) Benefit		5	(8,782)	(8,058)	(9,245)
Total other comprehensive income (loss), net of taxes		$ (442)	$ 14,140	(7,517)	14,886
ASU 2018-02 [Member]
Pension and postretirement benefits [Abstract]
Adoption of ASU 2018-02 - reclassification to retained earnings, Gross Amount				0	0
Adoption of ASU 2018-02 - reclassification to retained earnings, Income Tax (Provision) Benefit				(7,925)	0
Adoption of ASU 2018-02 - reclassification to retained earnings, Net Amount				$ (7,925)	$ 0

[1] Actuarial gains/(losses) are amortized into other income (expense). (See Note 13 - Retirement Plans)