Pension Plan and Employee Benefits - Components of Periodic Benefit Costs and Weighted-Average Assumptions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
PENSION BENEFITS
Components of periodic benefit costs
Service cost	$ 8,589	$ 10,516	$ 9,820
Interest cost	19,841	18,668	20,816
Expected return on plan assets	(24,706)	(22,801)	(24,974)
Amortizations
Prior service credit	0	0	(60)
Net loss	12,332	20,738	16,292
Net periodic benefit cost	16,056	27,121	21,894
Special/contractual termination benefits	0	3,270	0
Total benefit cost	$ 16,056	$ 30,391	$ 21,894
Weighted-average assumptions used to determine the benefit obligation
Discount rate	5.44%	2.98%
Rate of compensation increase	2.76%	2.73%
Weighted-average assumptions used to determine the net benefit cost
Discount rate	2.98%	2.74%	3.43%
Expected return on plan assets	5.25%	5.00%	5.91%
Rate of compensation increase	2.73%	2.71%	2.75%
OTHER BENEFITS
Components of periodic benefit costs
Service cost	$ 2,204	$ 2,425	$ 2,153
Interest cost	1,484	1,283	1,651
Expected return on plan assets	0	0	0
Amortizations
Prior service credit	0	0	0
Net loss	1,210	1,523	1,389
Net periodic benefit cost	4,898	5,231	5,193
Special/contractual termination benefits	0	0	0
Total benefit cost	$ 4,898	$ 5,231	$ 5,193
Weighted-average assumptions used to determine the benefit obligation
Discount rate	5.61%	2.82%
Weighted-average assumptions used to determine the net benefit cost
Discount rate	2.82%	2.39%	3.25%
SERP BENEFITS
Components of periodic benefit costs
Service cost	$ 227	$ 232	$ 399
Interest cost	2,679	2,538	2,932
Amortizations
Prior service credit	(215)	(215)	(215)
Net loss	1,049	1,228	3,186
Total benefit cost	$ 3,740	$ 3,783	$ 6,302
Weighted-average assumptions used to determine the benefit obligation
Discount rate	5.46%	2.95%
Weighted-average assumptions used to determine the net benefit cost
Discount rate	2.95%	2.64%	3.37%