EMPLOYEE RETIREMENT PLANS - Components of Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Components of net periodic pension cost [Abstract]
Service cost	$ 1,301	$ 1,214
Interest cost	1,047	1,013
Supplemental Executive Retirement Plan [Member]
Components of net periodic pension cost [Abstract]
Service cost	1,301	1,214	$ 1,415
Interest cost	1,047	1,013	875
Amortization of prior service cost	1,683	1,667	1,660
Amortization of loss	435	457	15
Total net periodic benefit cost	$ 4,466	$ 4,351	$ 3,965