Intangible Assets (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Intangible assets not subject to amortization	$ 51,864	$ 62,589
Cost of additions reduced by recognition of tax credits	2,639	1,022	$ 1,606
Capitalized cost of software under development	$ 299	$ 402	$ 460
Interest costs, weighted average rate	3.04%	4.01%	4.09%
Weighted average amortization period	9 years 1 month 6 days	7 years 9 months 18 days	8 years 2 months 12 days