Retirement Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Weighted-average expected long-term rate of return	6.00%		6.00%		5.50%
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	2,164	1,441	6,586	4,198
Expected return on plan assets	(3,435)	(3,669)	(8,833)	(11,006)
Amortization of actuarial loss (gain)	1,153	821	3,585	1,667
Net periodic benefit cost (income)	(118)	(1,407)	1,338	(5,141)
SERP
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	0	0
Interest cost	48	17	162	49
Expected return on plan assets	0	0	0	0
Amortization of actuarial loss (gain)	2	7	5	20
Net periodic benefit cost (income)	50	24	167	69
OPEB
Defined Benefit Plan Disclosure [Line Items]
Service cost	6	9	20	24
Interest cost	263	194	906	551
Expected return on plan assets	0	0	0	0
Amortization of actuarial loss (gain)	(676)	7	(2,028)	(30)
Net periodic benefit cost (income)	$ (407)	$ 210	$ (1,102)	$ 545