Derivatives And Risk Management (Energy Commodity Derivatives) (Details)	9 Months Ended
	Sep. 30, 2011 MmBtu
Purchases [Member] | Physical [Member] | Gas Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2011	12,539,000
2012	17,802,000
2013	7,105,000
2014	2,933,000
2015	675,000
Thereafter
Purchases [Member] | Physical [Member] | Electric Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2011	609,000
2012	950,000
2013	398,000
2014	366,000
2015	379,000
Thereafter	1,315,000
Purchases [Member] | Financial [Member] | Gas Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2011	29,225,000
2012	61,266,000
2013	52,155,000
2014	8,513,000
2015	1,125,000
Thereafter
Purchases [Member] | Financial [Member] | Electric Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2011	343,000
2012	2,150,000
2013	1,751,000
2014
2015
Thereafter
Sales [Member] | Physical [Member] | Gas Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2011	5,407,000
2012	2,893,000
2013	1,533,000
2014	1,050,000
2015
Thereafter
Sales [Member] | Physical [Member] | Electric Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2011	184,000
2012	377,000
2013	254,000
2014	286,000
2015	286,000
Thereafter	1,017,000
Sales [Member] | Financial [Member] | Gas Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2011	26,983,000
2012	61,260,000
2013	49,428,000
2014	3,900,000
2015
Thereafter
Sales [Member] | Financial [Member] | Electric Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2011	113,000
2012	656,000
2013	1,013,000
2014	123,000
2015
Thereafter