Fair-Value Measurements (Schedule of Fair Value of Financial Assets and Liabilities) (Details) - USD ($) $ in Thousands		Mar. 31, 2020		Dec. 31, 2019
Derivative asset:
Common stock of foreign public company, original cost		$ 500		$ 500
Quoted Prices in Active Markets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Cash equivalents		13,039		16,375
Common stock of unaffiliated foreign public company	[1]	765		839
Liabilities:
Interest rate swaps
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Cash equivalents
Common stock of unaffiliated foreign public company	[1]
Liabilities:
Interest rate swaps		(15,761)	[2]	(5,518)
Interest Rate Current Swap [Member]
Derivative liability:
Liability for fixed rate leg		19,200		20,700
Receivable for floating rate leg		$ 3,500		$ 15,200

[1] Original cost basis $0.5 million.

[2] Net of $3.5 million receivable floating leg and $19.2 million liability fixed leg.