EMPLOYEE BENEFITS - POSTRETIREMENT - Schedule of Net Periodic Benefit Costs Charged to Operating Expenses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Service cost	$ 1,897	$ 2,059
Interest cost	2,149	2,464
Expected return on assets	(2,857)	(2,528)
Amortization of unrecognized losses	(655)	32
Amortization of prior service credits	(1,622)	(1,672)
Net periodic benefit costs	$ (1,088)	$ 355