EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Other non-service component of net periodic benefit costs	$ 278	$ (101)
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	11,836	10,143
Interest cost	1,447	1,084
Expected return on plan assets	(2,134)	(1,442)
Amortization of prior service cost	21	13
Amortization of actuarial loss	71	113
Net periodic benefit cost	11,241	9,911
Post Retirement Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	287	316
Interest cost	155	172
Amortization of prior service cost	162	161
Net periodic benefit cost	$ 604	$ 649