Guarantees Of Debt (Schedule Of Financial Statements Of Guarantors) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Debt Instrument [Line Items]
Operating Revenues	$ 2,688	$ 2,641	$ 8,137	$ 8,113
Operating Expenses	1,874	1,895	5,707	6,297
Operating Income (Loss)	814	746	2,430	1,816
Equity Earnings (Losses) of Subsidiaries	3	3	10	10
Other Income	47	75	171	185
Other Deductions	(14)	(9)	(36)	(31)
Other-Than Temporary Impairments	30	10	45	14
Interest Expense	(96)	(100)	(291)	(291)
Income Tax Expense	(285)	(261)	(869)	(633)
Net Income	439	444	1,370	1,042
Net Cash Provided By (Used In) Operating Activities			3,228	2,536
Net Cash Provided By (Used In) Investing Activities			(2,841)	(1,988)
Net Cash Provided By (Used In) Financing Activities			(518)	(338)
Current Assets	3,204		3,204		$ 4,119
Property, Plant and Equipment, net	25,605		25,605		23,589
Noncurrent Assets	7,615		7,615		7,625
Total Assets	36,424		36,424		35,333
Current Liabilities	3,604		3,604		3,478
Noncurrent Liabilities	11,754		11,754		11,408
Long-Term Debt	8,132		8,132		8,261
Member's Equity	12,934		12,934		12,186
TOTAL LIABILITIES AND CAPITALIZATION	36,424		36,424		35,333
Power Senior Notes [Member]
Debt Instrument [Line Items]
Operating Revenues	1,096	1,138	3,846	3,824
Operating Expenses	705	785	2,643	3,122
Operating Income (Loss)	391	353	1,203	702
Equity Earnings (Losses) of Subsidiaries	3	4	11	11
Other Income	25	56	109	135
Other Deductions	(14)	(6)	(32)	(25)
Other-Than Temporary Impairments	30	10	45	14
Interest Expense	(30)	(31)	(94)	(92)
Income Tax Expense	(139)	(144)	(445)	(277)
Net Income	206	222	707	440
Comprehensive Income (Loss)	184	195	690	432
Net Cash Provided By (Used In) Operating Activities			1,558	1,110
Net Cash Provided By (Used In) Investing Activities			(1,150)	(326)
Net Cash Provided By (Used In) Financing Activities			(402)	(778)
Current Assets	2,224		2,224		2,359
Property, Plant and Equipment, net	7,907		7,907		7,515
Investment in Subsidiaries	0		0		0
Noncurrent Assets	2,183		2,183		2,172
Total Assets	12,314		12,314		12,046
Current Liabilities	1,574		1,574		1,184
Noncurrent Liabilities	3,200		3,200		3,061
Long-Term Debt	1,691		1,691		2,243
Member's Equity	5,849		5,849		5,558
TOTAL LIABILITIES AND CAPITALIZATION	12,314		12,314		12,046
Power Senior Notes [Member] | Power Parent [Member]
Debt Instrument [Line Items]
Operating Revenues	0	0	0	0
Operating Expenses	3	3	7	12
Operating Income (Loss)	(3)	(3)	(7)	(12)
Equity Earnings (Losses) of Subsidiaries	220	225	755	459
Other Income	10	9	33	25
Other Deductions	0	(3)	(1)	(7)
Other-Than Temporary Impairments	0	0	0	0
Interest Expense	(28)	(24)	(90)	(79)
Income Tax Expense	7	18	17	54
Net Income	206	222	707	440
Comprehensive Income (Loss)	184	195	690	432
Net Cash Provided By (Used In) Operating Activities			435	471
Net Cash Provided By (Used In) Investing Activities			(656)	187
Net Cash Provided By (Used In) Financing Activities			221	(652)
Current Assets	4,678		4,678		4,263
Property, Plant and Equipment, net	82		82		81
Investment in Subsidiaries	4,555		4,555		4,516
Noncurrent Assets	264		264		278
Total Assets	9,579		9,579		9,138
Current Liabilities	1,581		1,581		883
Noncurrent Liabilities	458		458		454
Long-Term Debt	1,691		1,691		2,243
Member's Equity	5,849		5,849		5,558
TOTAL LIABILITIES AND CAPITALIZATION	9,579		9,579		9,138
Power Senior Notes [Member] | Guarantor Subsidiaries [Member]
Debt Instrument [Line Items]
Operating Revenues	1,084	1,125	3,811	3,781
Operating Expenses	692	772	2,610	3,079
Operating Income (Loss)	392	353	1,201	702
Equity Earnings (Losses) of Subsidiaries	(2)	(1)	(4)	(4)
Other Income	26	55	111	135
Other Deductions	(14)	(4)	(31)	(18)
Other-Than Temporary Impairments	30	10	45	14
Interest Expense	(8)	(10)	(24)	(23)
Income Tax Expense	(148)	(161)	(463)	(329)
Net Income	216	222	745	449
Comprehensive Income (Loss)	187	191	707	433
Net Cash Provided By (Used In) Operating Activities			1,826	1,252
Net Cash Provided By (Used In) Investing Activities			(1,382)	(559)
Net Cash Provided By (Used In) Financing Activities			(446)	(693)
Current Assets	1,786		1,786		2,037
Property, Plant and Equipment, net	6,390		6,390		6,265
Investment in Subsidiaries	349		349		120
Noncurrent Assets	1,962		1,962		1,952
Total Assets	10,487		10,487		10,374
Current Liabilities	3,595		3,595		3,606
Noncurrent Liabilities	2,563		2,563		2,442
Long-Term Debt	0		0		0
Member's Equity	4,329		4,329		4,326
TOTAL LIABILITIES AND CAPITALIZATION	10,487		10,487		10,374
Power Senior Notes [Member] | Non-Guarantor Subsidiaries [Member]
Debt Instrument [Line Items]
Operating Revenues	37	36	144	118
Operating Expenses	35	32	135	106
Operating Income (Loss)	2	4	9	12
Equity Earnings (Losses) of Subsidiaries	3	4	11	11
Other Income	0	0	0	0
Other Deductions	0	0	0	0
Other-Than Temporary Impairments	0	0	0	0
Interest Expense	(5)	(4)	(15)	(14)
Income Tax Expense	2	(1)	1	(2)
Net Income	2	3	6	7
Comprehensive Income (Loss)	2	3	6	7
Net Cash Provided By (Used In) Operating Activities			66	53
Net Cash Provided By (Used In) Investing Activities			(303)	(24)
Net Cash Provided By (Used In) Financing Activities			245	(29)
Current Assets	134		134		150
Property, Plant and Equipment, net	1,435		1,435		1,169
Investment in Subsidiaries	0		0		0
Noncurrent Assets	133		133		137
Total Assets	1,702		1,702		1,456
Current Liabilities	772		772		786
Noncurrent Liabilities	355		355		360
Long-Term Debt	0		0		0
Member's Equity	575		575		310
TOTAL LIABILITIES AND CAPITALIZATION	1,702		1,702		1,456
Power Senior Notes [Member] | Consolidating Adjustments [Member]
Debt Instrument [Line Items]
Operating Revenues	(25)	(23)	(109)	(75)
Operating Expenses	(25)	(22)	(109)	(75)
Operating Income (Loss)	0	(1)	0	0
Equity Earnings (Losses) of Subsidiaries	(218)	(224)	(751)	(455)
Other Income	(11)	(8)	(35)	(25)
Other Deductions	0	1	0	0
Other-Than Temporary Impairments	0	0	0	0
Interest Expense	11	7	35	24
Income Tax Expense	0	0	0	0
Net Income	(218)	(225)	(751)	(456)
Comprehensive Income (Loss)	(189)	$ (194)	(713)	(440)
Net Cash Provided By (Used In) Operating Activities			(769)	(666)
Net Cash Provided By (Used In) Investing Activities			1,191	70
Net Cash Provided By (Used In) Financing Activities			(422)	$ 596
Current Assets	(4,374)		(4,374)		(4,091)
Property, Plant and Equipment, net	0		0		0
Investment in Subsidiaries	(4,904)		(4,904)		(4,636)
Noncurrent Assets	(176)		(176)		(195)
Total Assets	(9,454)		(9,454)		(8,922)
Current Liabilities	(4,374)		(4,374)		(4,091)
Noncurrent Liabilities	(176)		(176)		(195)
Long-Term Debt	0		0		0
Member's Equity	(4,904)		(4,904)		(4,636)
TOTAL LIABILITIES AND CAPITALIZATION	$ (9,454)		$ (9,454)		$ (8,922)