Derivatives (Fair Value Of Derivative Instruments And Locations In Balance Sheets) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Current derivative asset	$ 9,895	$ 16,552
Non-current derivative asset	4,887	0
Total derivatives assets	14,782	16,552
Current derivative liabilities	879	1,948
Non-current derivative liabilities	0	562
Total derivative liabilities	879	2,510
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Current derivative asset	4,215	13,674
Non-current derivative asset	0	0
Total derivatives designated as hedging instruments, assets	4,215	13,674
Current derivative liabilities	879	1,005
Non-current derivative liabilities	0	0
Total derivatives designated as hedging instruments, liabilities	879	1,005
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Current derivative asset	5,680	2,878
Non-current derivative asset	4,887	0
Total derivatives designated as hedging instruments, assets	10,567	2,878
Current derivative liabilities	0	943
Non-current derivative liabilities	0	562
Total derivatives designated as hedging instruments, liabilities	$ 0	$ 1,505