EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 10,900	$ 11,800
Interest cost	2,100	1,400
Expected return on plan assets	(2,400)	(2,100)
Amortization of prior service cost and actuarial loss	100	100
Net periodic benefit cost	10,700	11,200
Post Retirement Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	200	300
Interest cost	200	100
Amortization of prior service cost and actuarial loss	100	200
Net periodic benefit cost	$ 500	$ 600