Derivatives (Fair Value Of Derivative Instruments And Locations In Balance Sheets) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Current derivative assets	$ 16,552	$ 31,938
Non-current derivative assets	0	4,514
Total derivatives assets	16,552	36,452
Current portion of derivative liabilities	1,948	2,657
Non-current derivative liabilities	562	0
Total derivative liabilities	2,510	2,657
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Current derivative assets	13,674	31,938
Non-current derivative assets	0	4,514
Total derivatives assets	13,674	36,452
Current portion of derivative liabilities	1,005	2,657
Non-current derivative liabilities	0	0
Total derivative liabilities	1,005	2,657
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Current derivative assets	2,878	0
Non-current derivative assets	0	0
Total derivatives assets	2,878	0
Current portion of derivative liabilities	943	0
Non-current derivative liabilities	562	0
Total derivative liabilities	$ 1,505	$ 0