Derivative Instruments (Schedule Of Derivative Instruments) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Realized gain (loss) on derivative instruments, net	$ 9,887	$ 4,904	$ 21,020	$ 14,910
Unrealized gain (loss) on derivative instruments, net	28,360	7,161	20,265	(3,032)
Gain (loss) on derivative instruments, net	$ 38,247	$ 12,065	$ 41,285	$ 11,878