EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 7,340	$ 5,790
Interest cost	776	709
Expected return on plan assets	(1,106)	(829)
Amortization of prior service costs	13	13
Amortization of loss	194	311
Net periodic benefit cost	7,217	5,994
Post Retirement Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	220	244
Interest cost	134	134
Amortization of prior service costs	109	76
Amortization of loss	0	0
Net periodic benefit cost	$ 463	$ 454