Retirement Plans - Schedule Of Net Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
United States
Defined Benefit Plan Disclosure
Interest cost	$ 43	$ 56
Expected return on plan assets	(62)	(58)
Recognized net actuarial loss	25	13
Net periodic pension cost	6	11
United Kingdom
Defined Benefit Plan Disclosure
Interest cost	28	44
Expected return on plan assets	(65)	(59)
Amortization of prior service costs and transition amount	7	6
Recognized net actuarial loss	83	64
Net periodic pension cost	$ 53	$ 55