Property, Plant and Equipment (Average Estimated Useful Life of Each Major Class) (Details)	12 Months Ended
	Dec. 31, 2014
Electric [Member]
Public Utility Property, Plant and Equipment [Line Items]
Useful Life - Generation	40 years
Useful Life - Distribution	41 years
Gas [Member]
Public Utility Property, Plant and Equipment [Line Items]
Useful Life - Distribution	50 years
Useful Life - Storage	53 years