Employee Benefits (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Pension Plan
Net periodic benefit cost
Service cost	$ 954,000	$ 1,120,000	$ 2,863,000	$ 3,361,000
Interest cost	2,526,000	1,933,000	7,579,000	5,798,000
Expected return on plan assets	(3,756,000)	(4,723,000)	(11,269,000)	(14,168,000)
Amortization of prior service credit	(820,000)	(820,000)	(2,460,000)	(2,460,000)
Amortization of net loss	52,000	194,000	155,000	583,000
Net periodic benefit cost	(1,044,000)	(2,296,000)	(3,131,000)	(6,887,000)
Postretirement Benefit Plan
Net periodic benefit cost
Service cost	0	0	0	0
Interest cost	0	1,000	0	2,000
Expected return on plan assets	0	0	0	0
Amortization of prior service credit	0	(3,771,000)	0	(11,314,000)
Amortization of net loss	0	706,000	0	2,118,000
Net periodic benefit cost	$ 0	$ (3,064,000)	$ 0	$ (9,194,000)
Benefit obligation					$ 0