Derivatives (Fair Value Of Derivative Instruments And Locations In Balance Sheets) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Current derivative asset	$ 3,217	$ 16,552
Total derivatives assets	3,217	16,552
Current derivative liabilities	13,828	1,948
Non-current derivative liabilities	1,081	562
Total derivative liabilities	14,909	2,510
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Current derivative asset	3,217	13,674
Non-current derivative asset	0	0
Total derivatives designated as hedging instruments, assets	3,217	13,674
Current derivative liabilities	10,668	1,005
Non-current derivative liabilities	0	0
Total derivatives designated as hedging instruments, liabilities	10,668	1,005
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Current derivative asset	0	2,878
Non-current derivative asset	0	0
Total derivatives designated as hedging instruments, assets	0	2,878
Current derivative liabilities	3,160	943
Non-current derivative liabilities	1,081	562
Total derivatives designated as hedging instruments, liabilities	$ 4,241	$ 1,505