RETIREMENT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
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				$ (3,692)
Pension contributions		$ 6,717
Expected additional contribution	$ 1,925			1,925
Pension Plan [Member]
Components of net periodic benefit cost [Abstract]
Service cost	1,867		$ 2,865	4,094	$ 7,192
Interest cost	3,974		3,409	7,605	7,089
Expected return on plan assets	(5,693)		(4,568)	(11,016)	(9,005)
Amortization of actuarial loss	740		1,069	1,445	2,438
Net periodic benefit cost	888		2,775	2,128	7,714
SERP [Member]
Components of net periodic benefit cost [Abstract]
Service cost	0		0	0	0
Interest cost	12		15	24	29
Expected return on plan assets	0		0	0	0
Amortization of actuarial loss	6		7	12	14
Net periodic benefit cost	18		22	36	43
Other Postretirement Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	0		0	0	0
Interest cost	6		7	12	14
Amortization of actuarial loss	(149)		(168)	(298)	(335)
Net periodic benefit cost	$ (143)		$ (161)	$ (286)	$ (321)