Segment Information (Details Textuals)	3 Months Ended
	Mar. 31, 2013 Customers Companies sqmi
Regulated Distribution
Segment Reporting Information [Line Items]
Number of existing utility operating companies	10
Number of customers served by utility operating companies	6,000,000
Number of square miles in service area	65,000
Competitive Energy Services
Segment Reporting Information [Line Items]
Megawatts of net demonstrated capacity of competitive segment	18,000
Competitive Energy Services | Unregulated Plants Expected to be Closed by 9/1/2012
Segment Reporting Information [Line Items]
Megawatt capacity of plants expected to be closed	885