Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Segment Financial Information
External revenues									$ 15,049		$ 14,892		$ 15,253
Total revenues									15,049	[1]	14,892	[1]	15,255	[1]
Depreciation	316	308	302	294	293	316	300	293	1,220		1,202		1,119
Amortization of regulatory asset, net									12		539		(68)
Investment income									72		33		77
Interest expense									1,073		1,016		1,001
Income taxes (benefits)	(268)	152	26	48	66	77	(62)	114	(42)		195		545
Income (loss) from continuing operations	(306)	333	64	122	142	209	(168)	192	213		375		755
Discontinued operations (net of income taxes of $69, $9 and $8, respectively) (Note 19)	0	0	0	86	0	9	4	4	86		17		16
NET INCOME (LOSS)	(306)	333	64	208	142	218	(164)	196	299		392		771
Total assets	52,166				50,424				52,166		50,424		50,494
Total goodwill	6,418				6,418				6,418		6,418		6,447
Property additions									3,312		2,638		2,678
Intersegment Eliminations
Segment Financial Information
External revenues									0		0		2
Regulated Distribution
Segment Financial Information
External revenues									9,102		8,720		9,047
Total revenues									9,102		8,720		9,047
Depreciation									658		606		558
Amortization of regulatory asset, net									1		529		(65)
Investment income									56		57		84
Interest expense									589		543		540
Income taxes (benefits)									227		301		295
Income (loss) from continuing operations									465		501		540
Discontinued operations (net of income taxes of $69, $9 and $8, respectively) (Note 19)									0		0		0
NET INCOME (LOSS)									465		501		540
Total assets	28,232				27,683				28,232		27,683		27,150
Total goodwill	5,092				5,092				5,092		5,092		5,025
Property additions									972		1,272		1,074
Regulated Distribution | Intersegment Eliminations
Segment Financial Information
External revenues									0		0		0
Regulated Transmission
Segment Financial Information
External revenues									769		731		735
Total revenues									769		731		735
Depreciation									127		114		114
Amortization of regulatory asset, net									11		10		(3)
Investment income									0		0		1
Interest expense									131		93		92
Income taxes (benefits)									121		129		133
Income (loss) from continuing operations									223		214		226
Discontinued operations (net of income taxes of $69, $9 and $8, respectively) (Note 19)									0		0		0
NET INCOME (LOSS)									223		214		226
Total assets	6,352				5,247				6,352		5,247		4,865
Total goodwill	526				526				526		526		526
Property additions									1,329		461		507
Regulated Transmission | Intersegment Eliminations
Segment Financial Information
External revenues									0		0		0
Competitive Energy Services
Segment Financial Information
External revenues									5,470		5,728		5,778
Total revenues									6,289		6,498		6,644
Depreciation									387		439		409
Amortization of regulatory asset, net									0		0		0
Investment income									45		11		66
Interest expense									189		222		284
Income taxes (benefits)									(226)		(141)		83
Income (loss) from continuing operations									(423)		(237)		199
Discontinued operations (net of income taxes of $69, $9 and $8, respectively) (Note 19)									86		17		16
NET INCOME (LOSS)									(337)		(220)		215
Total assets	16,743				16,782				16,743		16,782		18,087
Total goodwill	800				800				800		800		896
Property additions									939		827		1,014
Competitive Energy Services | Intersegment Eliminations
Segment Financial Information
External revenues									819		770		866
Reconciling Adjustments
Segment Financial Information
External revenues									(146)		(166)		(188)
Total revenues									(965)		(936)		(1,052)
Depreciation									0		0		0
Amortization of regulatory asset, net									0		0		0
Investment income									(40)		(44)		(69)
Interest expense									(4)		10		0
Income taxes (benefits)									11		10		68
Income (loss) from continuing operations									0		0		(55)
Discontinued operations (net of income taxes of $69, $9 and $8, respectively) (Note 19)									0		0		0
NET INCOME (LOSS)									0		0		(55)
Total assets	0				0				0		0		0
Total goodwill	0				0				0		0		0
Property additions									0		0		0
Reconciling Adjustments | Intersegment Eliminations
Segment Financial Information
External revenues									(819)		(770)		(864)
Other/Corporate
Segment Financial Information
External revenues									(146)		(121)		(119)
Total revenues									(146)		(121)		(119)
Depreciation									48		43		38
Amortization of regulatory asset, net									0		0		0
Investment income									11		9		(5)
Interest expense									168		148		85
Income taxes (benefits)									(175)		(104)		(34)
Income (loss) from continuing operations									(52)		(103)		(155)
Discontinued operations (net of income taxes of $69, $9 and $8, respectively) (Note 19)									0		0		0
NET INCOME (LOSS)									(52)		(103)		(155)
Total assets	839				712				839		712		392
Total goodwill	0				0				0		0		0
Property additions									72		78		83
Other/Corporate | Intersegment Eliminations
Segment Financial Information
External revenues									$ 0		$ 0		$ 0

[1] Includes excise tax collections of $420 million, $458 million and $484 million in 2014, 2013 and 2012, respectively.