Fair-Value Measurements (Schedule of Fair Value of Financial Assets and Liabilities) (Details) - USD ($) $ in Thousands		Sep. 30, 2017		Dec. 31, 2016
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		18,246		8,468
Common stock of unaffiliated foreign public company	[1]	880		762
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
Liabilities:
Interest rate swaps		5,293	[2]	5,784	[3]
Interest Rate Current Swap [Member]
Derivative asset:
Liability for fixed rate leg		12,900		15,600
Receivable for floating rate leg		$ 18,200		$ 21,400

[1] Original cost basis $0.5 million

[2] Net of $18.2 million receivable floating leg and $12.9 million liability fixed leg

[3] Net of $21.4 million receivable floating leg and $15.6 million liability fixed leg