Retirement Benefit Plans (Obligation and Funded Status) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Amounts recognized in the balance sheets consist of:
Non-current liabilities	$ (6,605)	$ (8,838)
Pension Plan
Change in benefit obligation
Projected benefit obligation at beginning of year	44,600	41,854
Interest cost	1,002	1,285
Actuarial (gain) loss	(1,367)	3,996
Benefits paid	(2,572)	(2,535)
Projected benefit obligation at end of year	41,663	44,600
Accumulated benefit obligation at end of year	41,663	44,600
Change in plan assets
Fair value of plan assets at beginning of year	41,099	37,364
Actual return on plan assets	4,995	5,763
Employer contributions	487	507
Benefits paid	(2,572)	(2,535)
Fair value of plan assets at end of year	44,009	41,099
Funded status at end of year	2,346	(3,501)
Amounts recognized in the balance sheets consist of:
Non-current assets	7,806	4,070
Current liabilities	(542)	(549)
Non-current liabilities	(4,918)	(7,022)
Amount recognized in the balance sheets	2,346	(3,501)
Components of accumulated other comprehensive loss consist of:
Actuarial loss	9,510	14,022
Prior service cost	703	761
Deferred taxes	(2,254)	(3,316)
Accumulated other comprehensive (loss) income	7,959	11,467
Other Postretirement Benefits Plan
Change in benefit obligation
Projected benefit obligation at beginning of year	2,054	2,049
Service cost	13	21
Interest cost	27	52
Plan amendments	0	49
Actuarial (gain) loss	(48)	145
Benefits paid	(169)	(262)
Projected benefit obligation at end of year	1,877	2,054
Change in plan assets
Funded status at end of year	(1,877)	(2,054)
Amounts recognized in the balance sheets consist of:
Current liabilities	(190)	(238)
Non-current liabilities	(1,687)	(1,816)
Amount recognized in the balance sheets	(1,877)	(2,054)
Components of accumulated other comprehensive loss consist of:
Actuarial loss	520	466
Prior service cost	(108)	(167)
Deferred taxes	(195)	(167)
Accumulated other comprehensive (loss) income	$ 217	$ 132