BENEFIT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Pension Plans [Abstract]
Contribution made to defined benefit pension plan by employer			$ 3,900
Pension Benefits [Member]
Pension Plans [Abstract]
Contribution made to defined benefit pension plan by employer		$ 2,900
Net periodic benefit cost [Abstract]
Service cost	$ 1,480		1,438	$ 4,440	$ 4,313
Interest cost	1,259		1,356	3,777	4,068
Expected return on plan assets	(4,696)		(3,932)	(14,087)	(11,796)
Amortization of unrecognized net loss	900		810	2,700	2,430
Amortization of prior service cost	95		60	284	180
Net periodic benefit	(962)		(268)	(2,886)	(805)
Post-retirement Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost	0		0	0	0
Interest cost	11		15	33	43
Expected return on plan assets	0		0	0	0
Amortization of unrecognized net loss	11		10	33	30
Amortization of prior service cost	(45)		(45)	(134)	(134)
Net periodic benefit	$ (23)		$ (20)	$ (68)	$ (61)