EMPLOYEE BENEFIT PLANS - NRECA Executive Benefit Restoration Plan - Obligations (Details) - Executive Benefit Restoration Plan $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Postretirement medical benefit obligation at beginning of period	$ 10,158
Service cost	81
Interest cost	110
Total postretirement and postemployment medical obligations at end of period	10,349
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of period	10,298
Actual return on plan assets	64
Fair value of plan assets at end of period	10,362
Net liability recognized at end of period	$ (13)
Threshold of unrecognized amount of actuarial gains and losses as a proportion of projected benefit obligation (as a percent)	10.00%