RETIREMENT PLANS (Details) - USD ($) $ in Thousands		3 Months Ended
	Apr. 12, 2017	Mar. 31, 2017	Mar. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Pension plan defined benefit plan cost increase limit percentage		4.00%
Subsequent Event [Member]
Components of net periodic benefit cost [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
Pension Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost		$ 4,327	$ 3,220
Interest cost		3,680	3,412
Expected return on plan assets		(4,437)	(4,153)
Amortization of actuarial (gain) loss		1,369	1,218
Net periodic benefit cost		4,939	3,697
SERP [Member]
Components of net periodic benefit cost [Abstract]
Service cost		0	0
Interest cost		14	16
Expected return on plan assets		0	0
Amortization of actuarial (gain) loss		7	7
Net periodic benefit cost		21	23
Other Postretirement Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost		0	0
Interest cost		7	12
Amortization of actuarial (gain) loss		(167)	(188)
Net periodic benefit cost		$ (160)	$ (176)