Fair Value of Financial Instruments (Other Investments - Telecommunications Entities) (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Equity method investments, net investment	$ 220,000	$ 196,000
Equity method investments, equity in earnings (losses)	29,738	27,367	$ 23,855
Equity Investee [Member] | Subcontracting Arrangements [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Payments, related party	11,500	$ 7,000
Payables, related party	200
FM Tech [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Equity method investments, net investment	16,000
Telecommunications Equity Method Investees
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Equity method investments, equity in earnings (losses)	$ (1,500)