Derivative Instruments (Schedule Of Derivative Instruments) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Realized gain (loss) on derivative instruments, net	$ 2,291	$ 9,962	$ 8,006	$ 21,095
Unrealized gain (loss) on derivative instruments, net	23,435	27,928	3,166	20,598
Gain (loss) on derivative instruments, net	$ 25,726	$ 37,890	$ 11,172	$ 41,693