Fair Value Measurements (Schedule Of Quantitative Information About Unobservable Inputs) (Details) - Level 3 [Member] $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($) $ / Unit	[1]
Oil [Member] | Three-way collar [Member]
Derivative fair value | $	$ (9)
Derivatives Valuation Technique(s)	Discounted cash flow
Unobservable Input	Forward commodity price curve
Oil [Member] | Three-way collar [Member] | Minimum [Member]
Forward commodity price curve	(3.65)
Oil [Member] | Three-way collar [Member] | Maximum [Member]
Forward commodity price curve	5.02
Natural Gas [Member] | Collar [Member]
Derivative fair value | $	$ 25
Derivatives Valuation Technique(s)	Discounted cash flow
Unobservable Input	Forward commodity price curve
Natural Gas [Member] | Collar [Member] | Minimum [Member]
Forward commodity price curve	(0.11)
Natural Gas [Member] | Collar [Member] | Maximum [Member]
Forward commodity price curve	0.06
Natural Gas [Member] | Three-way collar [Member]
Derivative fair value | $	$ 1,470
Derivatives Valuation Technique(s)	Discounted cash flow
Unobservable Input	Forward commodity price curve
Natural Gas [Member] | Three-way collar [Member] | Minimum [Member]
Forward commodity price curve	(0.34)
Natural Gas [Member] | Three-way collar [Member] | Maximum [Member]
Forward commodity price curve	0.54

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