EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 10,144	$ 7,339	$ 20,287	$ 14,679
Interest cost	1,084	775	2,168	1,551
Expected return on plan assets	(1,442)	(1,107)	(2,884)	(2,213)
Amortization of prior service cost	13	13	26	26
Amortization of actuarial loss (gain)	113	194	226	388
Net periodic benefit cost	9,912	7,214	19,823	14,431
Post Retirement Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	316	219	632	439
Interest cost	172	133	344	267
Amortization of prior service cost	161	109	322	218
Amortization of actuarial loss (gain)	0	0	0	0
Net periodic benefit cost	$ 649	$ 461	$ 1,298	$ 924