Business Segments (Business Segment Data) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Operating revenues	$ 5,484	$ 5,589	$ 11,106	$ 11,654
Segment income	510	600	1,201	1,373
Add back noncontrolling interests	3	4	8	7
(Loss) Income From Discontinued Operations, net of tax	(1)	(57)	2	34
Net income (loss)	512	547	1,211	1,414
Segment assets	122,654		122,654		$ 121,156
Loss Contingency, Loss in Period		46		53
Regulated Utilities [Member]
Segment Reporting Information [Line Items]
Operating revenues	5,090	5,211	10,340	10,924
International Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	270	287	516	560
Asset Impairment Charges, net of tax	145		145
Commercial Portfolio [Member]
Segment Reporting Information [Line Items]
Operating revenues	112	75	227	148
Current State and Local Tax Expense (Benefit)		41		41
Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	12	16	23	22
Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	5,472	5,573	11,083	11,632
Operating Segments [Member] | Regulated Utilities [Member]
Segment Reporting Information [Line Items]
Operating revenues	5,099	5,220	10,358	10,943
Segment income	718	632	1,413	1,406
Segment assets	112,754		112,754
Operating Segments [Member] | International Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	270	287	516	560
Segment income	(102)	52	21	88
Segment assets	3,131		3,131
Operating Segments [Member] | Commercial Portfolio [Member]
Segment Reporting Information [Line Items]
Operating revenues	112	75	227	148
Segment income	14	(30)	41	(23)
Segment assets	4,329		4,329
Operating Segments [Member] | Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	5,481	5,582	11,092	11,651
Segment income	630	654	1,475	1,471
Segment assets	120,214		120,214
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues	(26)	(27)	(53)	(58)
Segment income		(3)		(4)
Segment assets	180		180
Intersegment Eliminations [Member] | Regulated Utilities [Member]
Segment Reporting Information [Line Items]
Operating revenues	(9)	(9)	(18)	(19)
Intersegment Eliminations [Member] | Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	(17)	(18)	(35)	(39)
Intersegment Eliminations [Member] | Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	(9)	(9)	(9)	(19)
Corporate, Non-Segment [Member] | Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	29	34	58	61
Segment income	(120)	(51)	(274)	(94)
Segment assets	2,260		2,260
Costs to achieve merger	69	$ 14	143	$ 27
Cost Savings Initiative, Net of tax	$ 15		$ 27