EMPLOYEE BENEFITS (Obligation and Funded Status) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits
Reconciliation of benefit obligation
Benefit obligation at beginning of year	$ 208,349	$ 171,876
Service cost	8,701	6,857	$ 6,490
Interest cost	7,500	7,060	6,654
Actuarial loss	(17,535)	26,963
Adjustment for plan amendment	0	0
Benefit payments	(4,859)	(4,407)
Benefit obligation at end of year	202,156	208,349	171,876
Reconciliation of fair value of plan assets
Fair value of plan assets at beginning of year	157,644	128,430
Actual return on plan assets	(4,366)	22,225
Employer contributions	16,400	11,396
Benefit payments	(4,859)	(4,407)
Fair value of plan assets at end of year	164,819	157,644	128,430
Funded status at end of year	(37,337)	(50,705)
Accumulated pension benefit obligation	183,317	184,436
Post-retirement Benefits
Reconciliation of benefit obligation
Benefit obligation at beginning of year	55,728	46,785
Service cost	2,998	2,021	3,728
Interest cost	2,009	1,927	3,015
Actuarial loss	(12,094)	6,326
Adjustment for plan amendment	(16,159)	0
Benefit payments	(1,509)	(1,331)
Benefit obligation at end of year	30,973	55,728	46,785
Reconciliation of fair value of plan assets
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	1,509	1,331
Benefit payments	(1,509)	(1,331)
Fair value of plan assets at end of year	0	0	$ 0
Funded status at end of year	$ (30,973)	$ (55,728)