Guarantees Of Debt (Schedule Of Financial Statements Of Guarantors) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Debt Instrument [Line Items]
Operating Revenues	$ 2,616	$ 3,135
Operating Expenses	1,789	2,087
Operating Income (Loss)	827	1,048
Equity Earnings (Losses) of Subsidiaries	2	3
Other Income	48	48
Other Deductions	(21)	(12)
Other-Than-Temporary Impairments	(10)	(5)
Interest Expense	(92)	(98)
Income Tax Expense	(283)	(398)
Net Income	471	586
Net Cash Provided By (Used In) Operating Activities	1,214	1,679
Net Cash Provided By (Used In) Investing Activities	(1,081)	(779)
Net Cash Provided By (Used In) Financing Activities	65	(294)
Current Assets	3,263		$ 3,494
Property, Plant and Equipment, net	27,274		26,539
Noncurrent Assets	7,589		7,502
Total Assets	38,126		37,535
Current Liabilities	2,942		3,575
Noncurrent Liabilities	12,189		12,059
Long-Term Debt	9,676		8,834
Member's Equity	13,319		13,067
TOTAL LIABILITIES AND CAPITALIZATION	38,126		37,535
Power Senior Notes [Member]
Debt Instrument [Line Items]
Operating Revenues	1,313	1,725
Operating Expenses	970	1,141
Operating Income (Loss)	343	584
Equity Earnings (Losses) of Subsidiaries	2	3
Other Income	26	29
Other Deductions	(18)	(11)
Other-Than-Temporary Impairments	(10)	(5)
Interest Expense	(22)	(31)
Income Tax Expense	(129)	(234)
Net Income	192	335
Comprehensive Income (Loss)	215	347
Net Cash Provided By (Used In) Operating Activities	663	850
Net Cash Provided By (Used In) Investing Activities	(659)	(635)
Net Cash Provided By (Used In) Financing Activities	0	(200)
Current Assets	2,031		1,949
Property, Plant and Equipment, net	8,326		8,127
Investment in Subsidiaries	0		0
Noncurrent Assets	2,260		2,174
Total Assets	12,617		12,250
Current Liabilities	1,312		1,226
Noncurrent Liabilities	3,403		3,338
Long-Term Debt	1,685		1,684
Member's Equity	6,217		6,002
TOTAL LIABILITIES AND CAPITALIZATION	12,617		12,250
Power Senior Notes [Member] | Power Parent [Member]
Debt Instrument [Line Items]
Operating Revenues	0	0
Operating Expenses	10	5
Operating Income (Loss)	(10)	(5)
Equity Earnings (Losses) of Subsidiaries	205	349
Other Income	17	11
Other Deductions	0	0
Other-Than-Temporary Impairments	0	0
Interest Expense	(30)	(29)
Income Tax Expense	10	9
Net Income	192	335
Comprehensive Income (Loss)	215	347
Net Cash Provided By (Used In) Operating Activities	271	327
Net Cash Provided By (Used In) Investing Activities	(598)	(537)
Net Cash Provided By (Used In) Financing Activities	326	210
Current Assets	4,819		4,501
Property, Plant and Equipment, net	88		83
Investment in Subsidiaries	4,615		4,501
Noncurrent Assets	138		155
Total Assets	9,660		9,240
Current Liabilities	1,316		1,112
Noncurrent Liabilities	441		442
Long-Term Debt	1,685		1,684
Member's Equity	6,218		6,002
TOTAL LIABILITIES AND CAPITALIZATION	9,660		9,240
Power Senior Notes [Member] | Guarantor Subsidiaries [Member]
Debt Instrument [Line Items]
Operating Revenues	1,302	1,715
Operating Expenses	952	1,131
Operating Income (Loss)	350	584
Equity Earnings (Losses) of Subsidiaries	(1)	(1)
Other Income	32	30
Other Deductions	(18)	(11)
Other-Than-Temporary Impairments	(10)	(5)
Interest Expense	(10)	(9)
Income Tax Expense	(140)	(242)
Net Income	203	346
Comprehensive Income (Loss)	219	351
Net Cash Provided By (Used In) Operating Activities	480	772
Net Cash Provided By (Used In) Investing Activities	(428)	(515)
Net Cash Provided By (Used In) Financing Activities	(51)	(242)
Current Assets	1,934		1,912
Property, Plant and Equipment, net	6,465		6,502
Investment in Subsidiaries	345		346
Noncurrent Assets	2,046		1,959
Total Assets	10,790		10,719
Current Liabilities	3,809		3,866
Noncurrent Liabilities	2,637		2,597
Long-Term Debt	0		0
Member's Equity	4,344		4,256
TOTAL LIABILITIES AND CAPITALIZATION	10,790		10,719
Power Senior Notes [Member] | Non-Guarantor Subsidiaries [Member]
Debt Instrument [Line Items]
Operating Revenues	42	68
Operating Expenses	39	63
Operating Income (Loss)	3	5
Equity Earnings (Losses) of Subsidiaries	2	3
Other Income	0	0
Other Deductions	0	0
Other-Than-Temporary Impairments	0	0
Interest Expense	(5)	(5)
Income Tax Expense	1	(1)
Net Income	1	2
Comprehensive Income (Loss)	1	2
Net Cash Provided By (Used In) Operating Activities	47	11
Net Cash Provided By (Used In) Investing Activities	(246)	(13)
Net Cash Provided By (Used In) Financing Activities	203	2
Current Assets	283		364
Property, Plant and Equipment, net	1,773		1,542
Investment in Subsidiaries	0		0
Noncurrent Assets	133		136
Total Assets	2,189		2,042
Current Liabilities	1,192		1,076
Noncurrent Liabilities	382		375
Long-Term Debt	0		0
Member's Equity	615		591
TOTAL LIABILITIES AND CAPITALIZATION	2,189		2,042
Power Senior Notes [Member] | Consolidating Adjustments [Member]
Debt Instrument [Line Items]
Operating Revenues	(31)	(58)
Operating Expenses	(31)	(58)
Operating Income (Loss)	0	0
Equity Earnings (Losses) of Subsidiaries	(204)	(348)
Other Income	(23)	(12)
Other Deductions	0	0
Other-Than-Temporary Impairments	0	0
Interest Expense	23	12
Income Tax Expense	0	0
Net Income	(204)	(348)
Comprehensive Income (Loss)	(220)	(353)
Net Cash Provided By (Used In) Operating Activities	(135)	(260)
Net Cash Provided By (Used In) Investing Activities	613	430
Net Cash Provided By (Used In) Financing Activities	(478)	$ (170)
Current Assets	(5,005)		(4,828)
Property, Plant and Equipment, net	0		0
Investment in Subsidiaries	(4,960)		(4,847)
Noncurrent Assets	(57)		(76)
Total Assets	(10,022)		(9,751)
Current Liabilities	(5,005)		(4,828)
Noncurrent Liabilities	(57)		(76)
Long-Term Debt	0		0
Member's Equity	(4,960)		(4,847)
TOTAL LIABILITIES AND CAPITALIZATION	$ (10,022)		$ (9,751)