EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 10,142	$ 10,064	$ 30,429	$ 24,743
Interest cost	1,084	772	3,252	2,323
Expected return on plan assets	(1,441)	(1,234)	(4,325)	(3,447)
Amortization of prior service cost	13	13	39	39
Amortization of actuarial loss (gain)	113	328	339	716
Net periodic benefit cost	9,911	9,943	29,734	24,374
Post Retirement Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	316	304	948	743
Interest cost	172	131	516	398
Amortization of prior service cost	162	161	484	379
Amortization of actuarial loss (gain)	0	0	0	0
Net periodic benefit cost	$ 650	$ 596	$ 1,948	$ 1,520