RETIREMENT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Service period of participants not impacted by pension plan amendment	15 years
Age of plan participants not impacted by pension plan amendment	50 years
Service period of participants who are age fifty not impacted by pension plan amendment	10 years
Decrease in pension plan projected benefit obligation	$ (33,433)
Pension plan defined benefit plan cost increase limit percentage	4.00%
Higman [Member]
Defined Benefit Plan Disclosure [Line Items]
Decrease in pension plan projected benefit obligation	$ (3,692)
Pension contributions	6,717
Expected additional contribution	1,925
Pension Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	2,227	$ 4,327
Interest cost	3,631	3,680
Expected return on plan assets	(5,323)	(4,437)
Amortization of actuarial (gain) loss	705	1,369
Net periodic benefit cost	1,240	4,939
SERP [Member]
Components of net periodic benefit cost [Abstract]
Service cost	0	0
Interest cost	12	14
Expected return on plan assets	0	0
Amortization of actuarial (gain) loss	6	7
Net periodic benefit cost	18	21
Other Postretirement Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	0	0
Interest cost	6	7
Amortization of actuarial (gain) loss	(149)	(167)
Net periodic benefit cost	$ (143)	$ (160)