Fair Value Measurements (Summary Of Available-For-Sale Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Total included in cash and cash equivalents
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 0	$ 3
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	0	0
Fair Value	0	3
Total included in restricted cash and cash equivalents
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	26,210	51,142
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	0	0
Fair Value	26,210	51,142
Total other short-term available-for-sale securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	0	24
Gross Unrealized Gains	0	10
Gross Unrealized (Losses)	0	0
Fair Value	0	34
Long-term available-for-sale securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,766	1,766
Gross Unrealized Gains	501	2,089
Gross Unrealized (Losses)	0	0
Fair Value	2,267	3,855
Money market funds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	26,210	51,145
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	0	0
Fair Value	26,210	51,145
Equity securities | Total other short-term available-for-sale securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	0	24
Gross Unrealized Gains	0	10
Gross Unrealized (Losses)	0	0
Fair Value	0	34
Equity securities | Long-term available-for-sale securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,766	1,766
Gross Unrealized Gains	501	2,089
Gross Unrealized (Losses)	0	0
Fair Value	$ 2,267	$ 3,855