BENEFIT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 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	$ 2,960	$ 2,875
Interest cost	1,259		1,356	2,518	2,712
Expected return on plan assets	(4,695)		(3,932)	(9,391)	(7,864)
Amortization of unrecognized net loss	900		810	1,800	1,620
Amortization of prior service cost	94		60	189	120
Net periodic benefit	(962)		(268)	(1,924)	(537)
Post-retirement Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost	0		0	0	0
Interest cost	11		14	22	28
Expected return on plan assets	0		0	0	0
Amortization of unrecognized net loss	11		10	22	20
Amortization of prior service cost	(44)		(44)	(89)	(89)
Net periodic benefit	$ (22)		$ (20)	$ (45)	$ (41)