Retirement Plans - Schedule Of Net Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
United States
Defined Benefit Plan Disclosure
Interest cost	$ 43	$ 56	$ 86	$ 112
Expected return on plan assets	(62)	(58)	(124)	(115)
Recognized net actuarial loss	25	13	49	27
Net periodic pension cost	6	11	11	24
United Kingdom
Defined Benefit Plan Disclosure
Interest cost	28	43	56	86
Expected return on plan assets	(65)	(58)	(130)	(116)
Amortization of prior service costs and transition amount	7	6	14	12
Recognized net actuarial loss	83	63	166	126
Net periodic pension cost	$ 53	$ 54	$ 106	$ 108