Fair Value Measurements (Financial Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Construction Reserve Funds & Title XI Reserve Funds	$ 255,408	$ 278,022
Exchange Option Liability on Subsidiary Convertible Senior Notes	5,611	0
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	138,200	58,004
Derivative instruments (included in other receivables)	469	2,277
Construction Reserve Funds & Title XI Reserve Funds	255,408	278,022
Short sales of marketable securities	4,827	7,339
Derivative instruments (included in other current liabilities)	4,985	2,834
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	0
Derivative instruments (included in other receivables)	0	6,205
Construction Reserve Funds & Title XI Reserve Funds	0	0
Short sales of marketable securities	0	0
Derivative instruments (included in other current liabilities)	299	752
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	0
Derivative instruments (included in other receivables)	0	0
Construction Reserve Funds & Title XI Reserve Funds	0	0
Short sales of marketable securities	0	0
Derivative instruments (included in other current liabilities)	0	0
Exchange Option Liability on Subsidiary Convertible Senior Notes				$ 5,611
Marketable Security Positions Held By The Company As Of December 31, 2015 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable security gains (losses), net include losses	$ 1,500	300	$ (900)
Marketable Security Positions Held By The Company As Of December 31, 2014 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable security gains (losses), net include losses		$ 27,800	$ 6,500