EMPLOYEE RETIREMENT PLANS - Schedule of change in benefit obligation and plan assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	$ 463	$ 569
Interest cost	2,460	2,204
Expected return on plan assets	(2,502)	(2,711)
Net amortization and deferral	626	634
Net periodic pension cost	1,047	696
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Long-term pension liability	27,523	23,112
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax [Abstract]
Net amount recognized	17,503	14,671
Plan Assets [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of year	37,353
Fair value of plan assets, end of year	41,036	37,353
Defined Benefit Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	463	360
Interest cost	1,801	1,608
Actuarial loss (gain)	5,660	(4,039)
Benefits paid	(2,382)	(2,294)
Projected benefit obligation, end of year	50,552	45,010
Projected benefit obligation, beginning of year	45,010	49,375
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Actual return on plan assets	6,528	(1,362)
Administrative expenses	(463)	(360)
Contributions		3,000
Benefits paid	(2,382)	(2,294)
Funded status of plan	(9,516)	(7,657)
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Long-term pension liability	9,516	7,657
Accrued liabilities - other		0
Net amount recognized	(9,516)	(7,657)
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax [Abstract]
Accumulated loss, net of income tax benefit of $4,478, $4,082, $1,684 and $1,102, respectively	12,745	11,616
Prior service cost, net of income tax liability of $0, $0, ($12) and ($28), respectively		0
Net amount recognized	12,745	11,616
Defined Benefit Pension Plan [Member] | Plan Assets [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of year	37,353	38,369
Fair value of plan assets, end of year	41,036	37,353
Supplemental Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	0	209
Interest cost	659	595
Actuarial loss (gain)	2,355	(1,601)
Benefits paid	(445)	(488)
Projected benefit obligation, end of year	18,460	15,891
Projected benefit obligation, beginning of year	15,891	17,176
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Actual return on plan assets	0	0
Administrative expenses	0	0
Contributions	445	488
Benefits paid	(445)	(488)
Funded status of plan	(18,460)	(15,891)
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Long-term pension liability	18,007	15,455
Accrued liabilities - other	(453)	(436)
Net amount recognized	(18,460)	(15,891)
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax [Abstract]
Accumulated loss, net of income tax benefit of $4,478, $4,082, $1,684 and $1,102, respectively	4,792	3,136
Prior service cost, net of income tax liability of $0, $0, ($12) and ($28), respectively	(34)	(81)
Net amount recognized	4,758	3,055
Supplemental Pension Plan [Member] | Plan Assets [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning of year	0	0
Fair value of plan assets, end of year	$ 0	$ 0