Retirement Plans (Schedule of Costs of Retirement Plans) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Defined Contribution Plan Disclosure
Expenses associated with contributions made	$ 788	$ 903	$ 2,317	$ 2,499
United States
Defined Contribution Plan Disclosure
Expenses associated with contributions made	656	766	1,887	2,080
Canada
Defined Contribution Plan Disclosure
Expenses associated with contributions made	29	23	102	91
United Kingdom
Defined Contribution Plan Disclosure
Expenses associated with contributions made	$ 103	$ 114	$ 328	$ 328