Pension Plan and Employee Benefits - Schedule of Net Periodic Pension and Other Benefits Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
PENSION BENEFITS
Components of periodic benefit costs
Service cost	$ 1,189	$ 1,173
Interest cost	6,535	6,606
Expected return on plan assets	(7,607)	(7,386)
Amortizations
Net loss (gain)	0	0
Net periodic benefit cost	117	393
OTHER BENEFITS
Components of periodic benefit costs
Service cost	479	365
Interest cost	583	566
Expected return on plan assets	0	0
Amortizations
Net loss (gain)	164	(13)
Net periodic benefit cost	1,226	918
SERP Benefits
Components of periodic benefit costs
Service cost	34	35
Interest cost	836	901
Amortizations
Prior period service credit	(54)	(54)
Net loss (gain)	(21)	(15)
Net periodic benefit cost	$ 795	$ 867