Retirement Plans - Schedule Of Net Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
United States
Defined Benefit Plan Disclosure
Interest cost	$ 56	$ 162
Expected return on plan assets	(58)	(180)
Recognized net actuarial loss	13	31
Net periodic pension cost	11	13
United Kingdom
Defined Benefit Plan Disclosure
Interest cost	44	54
Expected return on plan assets	(59)	(62)
Amortization of prior service costs and transition amount	6	11
Recognized net actuarial loss	64	53
Net periodic pension cost	$ 55	$ 56