Fair Value Measurements (Schedule Of Quantitative Information About Unobservable Inputs) (Details) (Level 3 [Member], USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Commodity Contract [Member]
Derivative assets, Fair Value	$ 3,835	[1]
Derivatives assets, Valuation Technique(s)	Discounted cash flow
Unobservable Input	Forward commodity price curve
Commodity Contract [Member] | Minimum [Member]
Forward commodity price curve	2.76
Commodity Contract [Member] | Maximum [Member]
Forward commodity price curve	3.50
Collar [Member]
Derivative assets, Fair Value	$ (2,232)	[2]
Derivatives assets, Valuation Technique(s)	Discounted cash flow
Unobservable Input	Forward commodity price curve
Collar [Member] | Minimum [Member]
Forward commodity price curve	0.07
Collar [Member] | Maximum [Member]
Forward commodity price curve	0.72

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

[2] The commodity contracts detailed in this category include non-exchange-traded natural gas 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.