EMPLOYEE BENEFIT PLANS - Changes in Plan Assets, Benefit Obligations, and Funded Status (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Change in plan assets:
Other adjustments	$ (20,215)	$ (14,476)	$ (9,903)
Pension Benefits
Change in projected benefit obligation:
Beginning of year	685,254	887,477
Service cost	22,159	34,847	35,055
Interest cost	34,190	25,596	21,667
Actuarial (gain) loss	(8,532)	(243,769)
Benefits paid, net of retiree premiums	(22,302)	(18,897)
End of year	710,769	685,254	887,477
Change in plan assets:
Fair value of plan assets at beginning of year	637,330	810,469
Actual return on plan assets	95,280	(171,517)
Employer contributions	5,965	17,275
Retiree contributions and Medicare part D subsidies	0	0
Benefits paid	(22,302)	(18,897)
Other adjustments	0	0
Fair value of plan assets at end of year	716,273	637,330	810,469
Reconciliation of funded status
Funded status	5,504	(47,924)
Unrecognized actuarial gain	(66,073)	(19,512)
Unrecognized prior service cost	2,680	3,205
Net amount recognized	(57,889)	(64,231)
Short-term portion of the pension benefits	2,800	2,600
Other Benefits
Change in projected benefit obligation:
Beginning of year	101,752	142,470
Service cost	4,489	6,830	6,072
Interest cost	5,219	4,009	3,217
Actuarial (gain) loss	27,208	(49,462)
Benefits paid, net of retiree premiums	(3,935)	(2,095)
End of year	134,733	101,752	142,470
Change in plan assets:
Fair value of plan assets at beginning of year	144,686	169,436
Actual return on plan assets	22,133	(23,326)
Employer contributions	189	671
Retiree contributions and Medicare part D subsidies	2,449	2,176
Benefits paid	(6,557)	(4,421)
Other adjustments	467	150
Fair value of plan assets at end of year	163,367	144,686	$ 169,436
Reconciliation of funded status
Funded status	28,634	42,934
Unrecognized actuarial gain	(26,764)	(44,555)
Unrecognized prior service cost	1,428	1,583
Net amount recognized	$ 3,298	$ (38)