Derivatives And Risk Management (Energy Commodity Derivatives) (Details) frequency in Thousands, Volt in Thousands	12 Months Ended
	Dec. 31, 2015 Volt frequency
Sales [Member] | Electric Derivative [Member] | Physical [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
2016	280
2017	255
2018	286
2019	158
2020	0
Thereafter	0
Sales [Member] | Electric Derivative [Member] | Financial [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
2016	2,656
2017	483
2018	0
2019	0
2020	0
Thereafter	0
Sales [Member] | Gas Derivative [Member] | Physical [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
2016 | Volt	3,182
2017 | Volt	1,360
2018 | Volt	1,360
2019	1,345
2020	1,430
Thereafter | Volt	1,060
Sales [Member] | Gas Derivative [Member] | Financial [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
2016 | Volt	112,233
2017 | Volt	26,965
2018 | Volt	2,738
2019 | Volt	0
2020	0
Thereafter | Volt	0
Purchase [Member] | Electric Derivative [Member] | Physical [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
2016	407
2017	397
2018	397
2019	235
2020	0
Thereafter	0
Purchase [Member] | Electric Derivative [Member] | Financial [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
2016	1,954
2017	97
2018	0
2019	0
2020	0
Thereafter	0
Purchase [Member] | Gas Derivative [Member] | Physical [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
2016 | Volt	17,252
2017 | Volt	675
2018 | Volt	0
2019 | Volt	305
2020 | Volt	455
Thereafter | Volt	0
Purchase [Member] | Gas Derivative [Member] | Financial [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
2016 | Volt	142,693
2017 | Volt	49,200
2018 | Volt	15,118
2019 | Volt	6,935
2020 | Volt	905
Thereafter | Volt	0