EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 10,143	$ 7,340
Interest cost	1,084	776
Expected return on plan assets	(1,442)	(1,106)
Amortization of prior service cost	13	13
Amortization of actuarial loss (gain)	113	194
Net periodic benefit cost	9,911	7,217
Post Retirement Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	316	220
Interest cost	172	134
Amortization of prior service cost	161	109
Amortization of actuarial loss (gain)	0	0
Net periodic benefit cost	$ 649	$ 463