EMPLOYEE BENEFITS (Obligation and Funded Status) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits
Reconciliation of benefit obligation
Benefit obligation at beginning of year	$ 160,390	$ 157,600
Service cost	6,490	6,675	$ 5,210
Interest cost	6,654	5,999	5,874
Actuarial (gain) loss	2,215	(5,678)
Adjustment for plan amendment	0	0
Benefit payments	(3,873)	(4,206)
Benefit obligation at end of year	171,876	160,390	157,600
Reconciliation of fair value of plan assets
Fair value of plan assets at beginning of year	106,600	102,800
Actual return on plan assets	9,320	1,654
Employer contributions	16,383	6,352
Benefit payments and adjustments	(3,873)	(4,206)
Fair value of plan assets at end of year	128,430	106,600	102,800
Funded status at end of year	(43,446)	(53,790)
Accumulated pension benefit obligation	152,620	141,550
Post-retirement Benefits
Reconciliation of benefit obligation
Benefit obligation at beginning of year	72,175	74,552
Service cost	3,728	5,220	3,696
Interest cost	3,015	2,856	2,342
Actuarial (gain) loss	1,468	(9,253)
Adjustment for plan amendment	(32,289)	0
Benefit payments	(1,312)	(1,200)
Benefit obligation at end of year	46,785	72,175	74,552
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	1,311	1,200
Benefit payments and adjustments	(1,311)	(1,200)
Fair value of plan assets at end of year	0	0	$ 0
Funded status at end of year	$ (46,785)	$ (72,175)