Pension Plan and Employee Benefits - Schedule of Net Periodic Pension and Other Benefits Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
PENSION BENEFITS
Components of periodic benefit costs
Service cost	$ 1,173	$ 2,043	$ 3,520	$ 6,130
Interest cost	6,606	4,960	19,817	14,881
Expected return on plan assets	(7,386)	(6,177)	(22,158)	(18,531)
Amortizations
Net loss (gain)	0	3,083	0	9,252
Net periodic benefit cost	393	3,909	1,179	11,732
OTHER BENEFITS
Components of periodic benefit costs
Service cost	365	546	1,094	1,639
Interest cost	566	368	1,698	1,103
Expected return on plan assets	0	0	0	0
Amortizations
Net loss (gain)	(13)	298	(39)	894
Net periodic benefit cost	918	1,212	2,753	3,636
SERP Benefits
Components of periodic benefit costs
Service cost	35	57	106	170
Interest cost	901	670	2,703	2,009
Amortizations
Prior period service credit	(54)	(54)	(161)	(161)
Net loss (gain)	(16)	262	(47)	787
Net periodic benefit cost	$ 866	$ 935	$ 2,601	$ 2,805