Fair Value Measurements (Schedule Of Quantitative Information About Unobservable Inputs) (Details) (Level 3 [Member], Collar [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Derivative assets, Fair Value	$ (2,536)	[1]
Derivatives assets, Valuation Technique(s)	Discounted cash flow
Unobservable Input	Forward commodity price curve
Minimum [Member]
Forward commodity price curve	0.00
Maximum [Member]
Forward commodity price curve	8.52

[1] The commodity contracts detailed in this category include non-exchange-traded natural gas and crude oil collars that are valued based on NYMEX. The forward pricing range represents the low and high price expected to be received within the settlement period.