Derivatives And Fair Value Measurements (Amount Of Gain Or (Loss) Recognized In Income On Derivative) (Details) (Swaps Contracts [Member], Net Cost Of Gas Sold [Member], USD $) In Thousands	3 Months Ended				6 Months Ended				12 Months Ended
	Jun. 30, 2011		Jun. 30, 2010		Jun. 30, 2011		Jun. 30, 2010		Jun. 30, 2011		Jun. 30, 2010
Swaps Contracts [Member] | Net Cost Of Gas Sold [Member]
Amount of (loss) recognized in income on derivative	$ (2,258)		$ (1,626)		$ (1,969)		$ (17,968)		$ (11,691)		$ (15,076)
Amount of gain or (loss) recognized in income on derivative	2,258	[1]	1,626	[1]	1,969	[1]	17,968	[1]	11,691	[1]	15,076	[1]
Amount of gain or (loss) recognized in income on derivative, total

[1] Represents the impact of regulatory deferral accounting treatment under U.S. GAAP for rate-regulated entities.