Fair Value Measurements (Financial Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) (USD $)	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Jun. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Construction Reserve Funds & Title XI Reserve Funds			$ 150,375,000	$ 195,629,000
Marketable security gains (losses), net include losses	6,500,000	(2,000,000)	10,500,000
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities			27,264,000
Derivative instruments (included in other receivables)			820,000
Construction Reserve Funds & Title XI Reserve Funds			150,375,000
Short sales of marketable securities			7,809,000
Derivative instruments (included in other current liabilities)			703,000
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)			5,961,000
Construction reserve funds and Title XI reserve funds			0
Short sales of marketable securities			0
Derivative instruments (included in other current liabilities)			4,770,000
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 and Title XI reserve funds			0
Short sales of marketable securities			0
Derivative instruments (included in other current liabilities)			$ 0