Derivatives And Risk Management (Energy Commodity Derivatives) (Details)	3 Months Ended
	Mar. 31, 2012
Purchases [Member] | Physical [Member] | Electric Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2012	976,000
2013	537,000
2014	366,000
2015	379,000
2016	367,000
Thereafter	949,000
Purchases [Member] | Physical [Member] | Gas Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2012	28,466,000
2013	11,895,000
2014	5,939,000
2015	3,013,000
2016	1,137,000
Purchases [Member] | Financial [Member] | Electric Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2012	845,000
2013	245,000
2014	0
Purchases [Member] | Financial [Member] | Gas Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2012	7,577,000
2013	10,270,000
2014	5,586,000
2015	980,000
2016	455,000
Sales [Member] | Physical [Member] | Electric Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2012	638,000
2013	310,000
2014	286,000
2015	285,000
2016	287,000
Thereafter	730,000
Sales [Member] | Physical [Member] | Gas Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2012	6,819,000
2013	1,533,000
2014	1,050,000
Sales [Member] | Financial [Member] | Electric Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2012	433,000
2013	491,000
2014	246,000
Sales [Member] | Financial [Member] | Gas Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2012	4,634,000
2013	1,727,000
2014	225,000