EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Other non-service components of net periodic benefit cost	$ 277	$ (101)	$ 555	$ (202)
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	11,836	10,144	23,672	20,287
Interest cost	1,449	1,084	2,896	2,168
Expected return on plan assets	(2,136)	(1,442)	(4,270)	(2,884)
Amortization of prior service cost	22	13	43	26
Amortization of actuarial loss	72	113	143	226
Net periodic benefit cost	11,243	9,912	22,484	19,823
Post Retirement Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	287	316	574	632
Interest cost	155	172	310	344
Amortization of prior service cost	161	161	323	322
Net periodic benefit cost	$ 603	$ 649	$ 1,207	$ 1,298