RETIREMENT BENEFITS - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 8,573	$ 12,603	$ 14,265
Interest cost	34,725	20,579	17,697
Expected return on plan assets	(40,781)	(69,132)	(79,453)
Amortization of prior service cost (credit)	97	222	243
Amortization of actuarial losses (gains)	11,638	4,635	12,479
Special termination benefits	577	0	0
Curtailment gain	0	0	0
Net periodic benefit cost (credit)	14,829	(31,093)	(34,769)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	50	78	107
Interest cost	745	413	363
Expected return on plan assets	0	0	0
Amortization of prior service cost (credit)	(948)	(1,668)	(1,830)
Amortization of actuarial losses (gains)	(617)	(298)	(311)
Special termination benefits	0	0	0
Curtailment gain	(1,103)	0	0
Net periodic benefit cost (credit)	$ (1,873)	$ (1,475)	$ (1,671)