Business Segments (Schedule of Revenue, By Products and Services) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Operating revenues	$ 5,322	$ 6,483	$ 5,589	$ 6,065	$ 5,559	$ 6,395	$ 5,708	$ 6,263	$ 23,459	$ 23,925	$ 22,756
Regulated Utilities [Member]
Segment Reporting Information [Line Items]
Operating revenues									22,024	22,228	20,871
International Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues									1,088	1,417	1,546
Commercial Power [Member]
Segment Reporting Information [Line Items]
Operating revenues									301	255	254
Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues									23,413	23,900	22,671
Retail Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues									18,695	19,007	17,837
Retail Electric [Member] | Regulated Utilities [Member]
Segment Reporting Information [Line Items]
Operating revenues									18,695	19,007	17,837
Wholesale Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues									3,299	3,460	3,427
Wholesale Electric [Member] | Regulated Utilities [Member]
Segment Reporting Information [Line Items]
Operating revenues									2,014	1,879	1,720
Wholesale Electric [Member] | International Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues									1,025	1,326	1,447
Wholesale Electric [Member] | Commercial Power [Member]
Segment Reporting Information [Line Items]
Operating revenues									260	255	260
Retail Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues									546	571	506
Retail Gas [Member] | Regulated Utilities [Member]
Segment Reporting Information [Line Items]
Operating revenues									546	571	506
Wholesale Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues									63	91	99
Wholesale Gas [Member] | International Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues									63	91	99
Other Revenues [Member]
Segment Reporting Information [Line Items]
Operating revenues									848	814	847
Other Revenues [Member] | Regulated Utilities [Member]
Segment Reporting Information [Line Items]
Operating revenues									807	814	847
Other Revenues [Member] | Commercial Power [Member]
Segment Reporting Information [Line Items]
Operating revenues									41
Operating Segments [Member] | Regulated Utilities [Member]
Segment Reporting Information [Line Items]
Operating revenues									22,062	22,271	20,910
Operating Segments [Member] | International Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues									1,088	1,417	1,546
Operating Segments [Member] | Commercial Power [Member]
Segment Reporting Information [Line Items]
Operating revenues									301	255	260
Operating Segments [Member] | Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues									$ 23,451	$ 23,943	$ 22,716