Retirement Plans - Schedule Of Net Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
United States
Defined Benefit Plan Disclosure
Interest cost	$ 43	$ 56	$ 129	$ 168
Expected return on plan assets	(62)	(58)	(185)	(173)
Recognized net actuarial loss	25	13	74	40
Net periodic pension cost	6	11	18	35
United Kingdom
Defined Benefit Plan Disclosure
Interest cost	28	43	84	129
Expected return on plan assets	(65)	(59)	(195)	(177)
Amortization of prior service costs and transition amount	7	6	21	18
Recognized net actuarial loss	83	63	249	189
Net periodic pension cost	$ 53	$ 53	$ 159	$ 159