Fair Value Measurements (Financial Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Construction Reserve Funds	$ 255,350		$ 255,408
Exchange Option Liability on Subsidiary Convertible Senior Notes	5,747		$ 5,611
Marketable security (losses), net	(24,500)	$ (200)
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	110,894
Derivative instruments (included in other receivables)	199
Construction Reserve Funds	255,350
Short sales of marketable securities	5,053
Derivative instruments (included in other current liabilities)	1,663
Exchange Option Liability on Subsidiary Convertible Senior Notes	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0
Derivative instruments (included in other receivables)	228
Construction Reserve Funds	0
Short sales of marketable securities	0
Derivative instruments (included in other current liabilities)	212
Exchange Option Liability on Subsidiary Convertible Senior Notes	0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0
Derivative instruments (included in other receivables)	0
Construction Reserve Funds	0
Short sales of marketable securities	0
Derivative instruments (included in other current liabilities)	0
Exchange Option Liability on Subsidiary Convertible Senior Notes	$ 5,747