EMPLOYEE BENEFIT PLANS - Changes in obligations and assets (Details) - Defined Benefit Pension Items [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CHANGE IN BENEFIT OBLIGATION:
Benefit obligation at beginning of year	$ 41,094	$ 41,013
Service cost	1,470	1,482	$ 1,516
Interest cost	1,569	1,273	1,292
Actuarial loss	7,758	823
Special/contractual termination benefits	0	63	0
Benefits paid	(2,330)	(3,560)
Benefit obligation at end of year	49,561	41,094	41,013
CHANGE IN PLAN ASSETS:
Fair value of plan assets at beginning of year	38,478	37,100
Actual return on plan assets	5,483	(1,062)
Employer contributions	3,200	6,000
Benefits paid	(2,330)	(3,560)
Fair value of plan assets at end of year	44,831	38,478	$ 37,100
Funded status of the plan	$ (4,730)	$ (2,616)