Retirement Benefit Plans (Obligation and Funded Status) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Amounts recognized in the balance sheets consist of:
Non-current liabilities	$ (5,183)	$ (5,082)
Pension Plan
Change in benefit obligation
Projected benefit obligation at beginning of year	31,722	41,663
Interest cost	1,639	1,105
Actuarial loss (gain)	2,261	(8,396)
Benefits paid	(2,614)	(2,650)
Settlements	(4,651)	0
Projected benefit obligation at end of year	28,357	31,722
Accumulated benefit obligation at end of year	28,357	31,722
Change in plan assets
Fair value of plan assets at beginning of year	34,485	44,009
Actual return on plan assets	2,452	(7,405)
Employer contributions	456	531
Benefits paid	(2,614)	(2,650)
Settlements	(4,651)	0
Fair value of plan assets at end of year	30,128	34,485
Funded status at end of year	1,771	2,763
Amounts recognized in the balance sheets consist of:
Non-current assets	6,068	6,991
Current liabilities	(510)	(491)
Non-current liabilities	(3,787)	(3,737)
Amount recognized in the balance sheets	1,771	2,763
Components of accumulated other comprehensive loss consist of:
Actuarial loss	11,379	10,682
Prior service cost	586	645
Deferred taxes	(2,724)	(2,490)
Accumulated other comprehensive (loss) income	9,241	8,837
Other Postretirement Benefits Plan
Change in benefit obligation
Projected benefit obligation at beginning of year	1,551	1,877
Service cost	7	12
Interest cost	77	38
Actuarial loss (gain)	173	(44)
Benefits paid	(229)	(332)
Projected benefit obligation at end of year	1,579	1,551
Change in plan assets
Funded status at end of year	(1,579)	(1,551)
Amounts recognized in the balance sheets consist of:
Current liabilities	(183)	(206)
Non-current liabilities	(1,396)	(1,345)
Amount recognized in the balance sheets	(1,579)	(1,551)
Components of accumulated other comprehensive loss consist of:
Actuarial loss	542	412
Prior service cost	(6)	(56)
Deferred taxes	(123)	(180)
Accumulated other comprehensive (loss) income	$ 413	$ 176