PENSION PLAN AND OTHER BENEFIT PLANS - Changes in Projected Benefit Obligation and Plan Assets, and Funded Status (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plan
Changes in projected benefit obligation [Roll Forward]
Benefit obligation at beginning of year	$ 39,791	$ 43,797
Service cost	0	1,047	$ 1,231
Interest cost	1,646	1,883	1,806
Actuarial (gain) loss	2,634	913
Curtailments	0	(6,161)
Benefits paid	(1,831)	(1,688)
Benefit obligation at end of year	42,240	39,791	43,797
Changes in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	41,560	39,951
Actual return on plan assets	6,943	3,297
Employer contributions	0	0
Benefits paid	(1,831)	(1,688)
Fair value of plan assets at end of year	46,672	41,560	39,951
Funded status of plan	4,432	1,769
Defined Benefit Health Care Plan
Changes in projected benefit obligation [Roll Forward]
Benefit obligation at beginning of year	423	1,664
Service cost	0	43	46
Interest cost	20	66	70
Participant contributions	76	87
Amendments	0	(1,101)
Actuarial (gain) loss	98	138
Benefits paid	(176)	(474)
Benefit obligation at end of year	441	423	1,664
Changes in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	0	0
Employer contributions	100	387
Participant contributions	76	87
Benefits paid	(176)	(474)
Fair value of plan assets at end of year	0	0	0
Funded status of plan	(441)	(423)
Executive Supplemental Pension Plan
Changes in projected benefit obligation [Roll Forward]
Benefit obligation at beginning of year	1,248	1,210
Service cost	0	43	44
Interest cost	50	51	49
Actuarial (gain) loss	66	19
Benefits paid	(75)	(75)
Benefit obligation at end of year	1,289	1,248	1,210
Changes in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	0	0
Employer contributions	75	75
Benefits paid	(75)	(75)
Fair value of plan assets at end of year	0	0	$ 0
Funded status of plan	$ (1,289)	$ (1,248)