Pension Plan and Employee Benefits - Amounts Recognized in Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
PENSION BENEFITS
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain) occurring during period	$ 17,082	$ (58,124)
Net actuarial loss (gain) amortized during period	0	12,332
Net actuarial loss	64,399	47,317
OTHER BENEFITS
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain) occurring during period	5,110	(10,289)
Net actuarial loss (gain) amortized during period	(45)	1,207
Net actuarial loss	13,103	13,705
SERP BENEFITS
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain) occurring during period	(345)	(22,097)
Net actuarial loss (gain) amortized during period	(63)	1,049
Prior service credit amortized during period	(215)	(215)
Net actuarial loss	7,819	8,241
Prior service credit	$ (1,085)	$ (1,299)