Segment Information (Details Textuals) (USD $)	12 Months Ended
	Dec. 31, 2014 customer company sqmi	Oct. 09, 2013 MW
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
Megawatts of net demonstrated capacity of competitive segment		3,790
Competitive Energy Services
Segment Reporting Information [Line Items]
Megawatts of net demonstrated capacity of competitive segment	14,068
Competitive Energy Services | Minimum
Segment Reporting Information [Line Items]
Targeted sales portfolio	65,000,000
Competitive Energy Services | Maximum
Segment Reporting Information [Line Items]
Targeted sales portfolio	75,000,000
Competitive Energy Services | Governmental Aggregation | Minimum
Segment Reporting Information [Line Items]
Targeted sales portfolio	10,000,000
Competitive Energy Services | Governmental Aggregation | Maximum
Segment Reporting Information [Line Items]
Targeted sales portfolio	15,000,000
Competitive Energy Services | POLR Sales | Minimum
Segment Reporting Information [Line Items]
Targeted sales portfolio	0
Competitive Energy Services | POLR Sales | Maximum
Segment Reporting Information [Line Items]
Targeted sales portfolio	10,000,000
Competitive Energy Services | Large Commercial and Industrial Sales | Minimum
Segment Reporting Information [Line Items]
Targeted sales portfolio	0
Competitive Energy Services | Large Commercial and Industrial Sales | Maximum
Segment Reporting Information [Line Items]
Targeted sales portfolio	20,000,000
Competitive Energy Services | Block Wholesale Sales | Minimum
Segment Reporting Information [Line Items]
Targeted sales portfolio	10,000,000
Competitive Energy Services | Block Wholesale Sales | Maximum
Segment Reporting Information [Line Items]
Targeted sales portfolio	20,000,000
Competitive Energy Services | Spot Wholesale Sales | Minimum
Segment Reporting Information [Line Items]
Targeted sales portfolio	10,000,000
Competitive Energy Services | Spot Wholesale Sales | Maximum
Segment Reporting Information [Line Items]
Targeted sales portfolio	20,000,000
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
Other Business Operations [Member]
Segment Reporting Information [Line Items]
Long-term debt and other long-term obligations	4,200,000,000
Long-term Debt, Amount Subject to Variable Interest Rate, Percent	28.00%
Parent Company | Revolving Credit Facility | Other Business Operations [Member]
Segment Reporting Information [Line Items]
Long-term Line of Credit	1,700,000,000