EMPLOYEE BENEFITS (Obligation and Funded Status) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits
Reconciliation of benefit obligation
Benefit obligation at beginning of year	$ 202,156	$ 208,349
Service cost	7,989	8,701	$ 6,857
Interest cost	8,320	7,500	7,060
Actuarial loss (gain)	39,598	(17,535)
Adjustment for plan amendment	0	0
Benefit payments	(5,689)	(4,859)
Benefit obligation at end of year	252,374	202,156	208,349
Reconciliation of fair value of plan assets
Fair value of plan assets at beginning of year	164,819	157,644
Actual return on plan assets	36,336	(4,366)
Employer contributions	4,000	16,400
Benefit payments	(5,689)	(4,859)
Fair value of plan assets at end of year	199,466	164,819	157,644
Funded status at end of year	(52,908)	(37,337)
Accumulated pension benefit obligation	226,196	183,317
Post-retirement Benefits
Reconciliation of benefit obligation
Benefit obligation at beginning of year	30,973	55,728
Service cost	1,823	2,998	2,021
Interest cost	1,274	2,009	1,927
Actuarial loss (gain)	(1,806)	(12,094)
Adjustment for plan amendment	0	(16,159)
Benefit payments	(1,263)	(1,509)
Benefit obligation at end of year	31,001	30,973	55,728
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	1,263	1,509
Benefit payments	(1,263)	(1,509)
Fair value of plan assets at end of year	0	0	$ 0
Funded status at end of year	$ (31,001)	$ (30,973)