EMPLOYEE BENEFIT PLANS (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 5,790	$ 4,291
Interest cost	709	570
Expected return on plan assets	(829)	(524)
Amortization of prior service costs	13	3
Amortization of actuarial loss	311	222
Net periodic benefit cost	5,994	4,562
Post Retirement Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	244	178
Interest cost	134	93
Amortization of prior service costs	76	(20)
Amortization of actuarial loss	0	(5)
Net periodic benefit cost	$ 454	$ 246