RETIREMENT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Retirement Plans [Abstract]
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]
Retirement Plans [Abstract]
Decrease in pension plan projected benefit obligation	$ (3,081)
Pension contributions	1,615
Expected additional contribution	1,449
Pension Plan [Member]
Components of net periodic benefit cost [Abstract]
Service cost	1,768	$ 2,227
Interest cost	4,207	3,631
Expected return on plan assets	(5,224)	(5,323)
Amortization of actuarial loss	678	705
Net periodic benefit cost	1,429	1,240
SERP [Member]
Components of net periodic benefit cost [Abstract]
Service cost	0	0
Interest cost	13	12
Expected return on plan assets	0	0
Amortization of actuarial loss	7	6
Net periodic benefit cost	20	18
Other Postretirement Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	0	0
Interest cost	8	6
Amortization of actuarial loss	(135)	(149)
Net periodic benefit cost	$ (127)	$ (143)