Fair-Value Measurements (Schedule of Fair Value of Financial Assets and Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Derivative Asset [Abstract]
Equity securities, cost basis	$ 500	$ 500
Fair Value, Recurring | (Level 1)
Assets:
Cash equivalents	14,390	17,508
Common stock of unaffiliated foreign public company	762	748
Liabilities:
Interest rate swaps	0	0
Fair Value, Recurring | (Level 2)
Assets:
Cash equivalents	0	0
Common stock of unaffiliated foreign public company	0	0
Liabilities:
Interest rate swaps	$ (10,918)	$ (12,714)