Guarantees Of Debt (Schedule Of Financial Statements Of Guarantors) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Operating Revenues	$ 2,786	$ 2,875
Operating Expenses	2,176	2,092
Operating Income (Loss)	610	783
Equity Earnings (Losses) of Subsidiaries	2	0
Other Income	61	44
Other Deductions	(29)	(16)
Other-Than-Temporary Impairments	(2)	(5)
Interest Expense	(102)	(101)
Income Tax Benefit (Expense)	(220)	(212)
Net Income	320	493
Net Cash Provided By (Used In) Operating Activities	877	1,088
Net Cash Provided By (Used In) Investing Activities	(733)	(706)
Net Cash Provided By (Used In) Financing Activities	(103)	(285)
Current Assets	3,656		3,869
Property, Plant and Equipment, net	20,125		19,736
Noncurrent Assets	7,931		8,120
Total Assets	31,712		31,725
Current Liabilities	3,406		3,777
Noncurrent Liabilities	10,350		10,480
Long-Term Debt	7,009		6,687
Member's Equity	10,947		10,781
TOTAL LIABILITIES AND CAPITALIZATION	31,712		31,725
Power [Member]
Operating Revenues	1,447	1,561
Operating Expenses	1,206	1,120
Operating Income (Loss)	241	441
Other Income	47	30
Other Deductions	(28)	(15)
Other-Than-Temporary Impairments	(2)	(5)
Interest Expense	(30)	(30)
Income Tax Benefit (Expense)	(91)	(168)
Net Income	137	253
Net Cash Provided By (Used In) Operating Activities	572	731
Net Cash Provided By (Used In) Investing Activities	(321)	(365)
Net Cash Provided By (Used In) Financing Activities	(252)	(373)
Current Assets	2,052		2,234
Property, Plant and Equipment, net	6,993		7,018
Noncurrent Assets	1,820		1,780
Total Assets	10,865		11,032
Current Liabilities	872		967
Noncurrent Liabilities	2,595		2,586
Long-Term Debt	2,040		2,040
Member's Equity	5,358		5,439
TOTAL LIABILITIES AND CAPITALIZATION	10,865		11,032
Power Senior Notes [Member] | Power Parent [Member]
Operating Revenues	0	0
Operating Expenses	2	(2)
Operating Income (Loss)	(2)	2
Equity Earnings (Losses) of Subsidiaries	149	260
Other Income	9	13
Other Deductions	(8)	(7)
Other-Than-Temporary Impairments	0	0
Interest Expense	(27)	(29)
Income Tax Benefit (Expense)	16	14
Net Income	137	253
Comprehensive Income (Loss)	169	297
Net Cash Provided By (Used In) Operating Activities	189	124
Net Cash Provided By (Used In) Investing Activities	61	242
Net Cash Provided By (Used In) Financing Activities	(250)	(366)
Current Assets	3,926		3,922
Property, Plant and Equipment, net	80		80
Investment in Subsidiaries	4,240		4,317
Noncurrent Assets	189		201
Total Assets	8,435		8,520
Current Liabilities	529		482
Noncurrent Liabilities	508		559
Long-Term Debt	2,040		2,040
Member's Equity	5,358		5,439
TOTAL LIABILITIES AND CAPITALIZATION	8,435		8,520
Power Senior Notes [Member] | Power [Member]
Operating Revenues	1,447	1,561
Operating Expenses	1,206	1,120
Operating Income (Loss)	241	441
Equity Earnings (Losses) of Subsidiaries	0	0
Other Income	47	30
Other Deductions	(28)	(15)
Other-Than-Temporary Impairments	(2)	(5)
Interest Expense	(30)	(30)
Income Tax Benefit (Expense)	(91)	(168)
Net Income	137	253
Comprehensive Income (Loss)	169	297
Net Cash Provided By (Used In) Operating Activities	572	731
Net Cash Provided By (Used In) Investing Activities	(321)	(365)
Net Cash Provided By (Used In) Financing Activities	(252)	(373)
Current Assets	2,052		2,234
Property, Plant and Equipment, net	6,993		7,018
Investment in Subsidiaries	0		0
Noncurrent Assets	1,820		1,780
Total Assets	10,865		11,032
Current Liabilities	872		967
Noncurrent Liabilities	2,595		2,586
Long-Term Debt	2,040		2,040
Member's Equity	5,358		5,439
TOTAL LIABILITIES AND CAPITALIZATION	10,865		11,032
Power Senior Notes [Member] | Guarantor Subsidiaries [Member]
Operating Revenues	1,803	1,873
Operating Expenses	1,562	1,433
Operating Income (Loss)	241	440
Equity Earnings (Losses) of Subsidiaries	0	(3)
Other Income	48	31
Other Deductions	(20)	(8)
Other-Than-Temporary Impairments	(2)	(5)
Interest Expense	(10)	(10)
Income Tax Benefit (Expense)	(108)	(185)
Net Income	149	260
Comprehensive Income (Loss)	172	297
Net Cash Provided By (Used In) Operating Activities	574	723
Net Cash Provided By (Used In) Investing Activities	(353)	(656)
Net Cash Provided By (Used In) Financing Activities	(221)	(73)
Current Assets	8,180		8,084
Property, Plant and Equipment, net	5,972		5,988
Investment in Subsidiaries	733		733
Noncurrent Assets	1,722		1,660
Total Assets	16,607		16,465
Current Liabilities	10,334		10,187
Noncurrent Liabilities	2,032		1,960
Long-Term Debt	0		0
Member's Equity	4,241		4,318
TOTAL LIABILITIES AND CAPITALIZATION	16,607		16,465
Power Senior Notes [Member] | Other Subsidiaries [Member]
Operating Revenues	33	26
Operating Expenses	30	27
Operating Income (Loss)	3	(1)
Equity Earnings (Losses) of Subsidiaries	0	0
Other Income	0	0
Other Deductions	0	0
Other-Than-Temporary Impairments	0	0
Interest Expense	(4)	(4)
Income Tax Benefit (Expense)	1	2
Net Income	0	(3)
Comprehensive Income (Loss)	0	(3)
Net Cash Provided By (Used In) Operating Activities	(2)	2
Net Cash Provided By (Used In) Investing Activities	0	(13)
Net Cash Provided By (Used In) Financing Activities	2	10
Current Assets	942		940
Property, Plant and Equipment, net	941		950
Investment in Subsidiaries	0		0
Noncurrent Assets	59		60
Total Assets	1,942		1,950
Current Liabilities	1,001		1,010
Noncurrent Liabilities	208		207
Long-Term Debt	0		0
Member's Equity	733		733
TOTAL LIABILITIES AND CAPITALIZATION	1,942		1,950
Power Senior Notes [Member] | Consolidating Adjustments [Member]
Operating Revenues	(389)	(338)
Operating Expenses	(388)	(338)
Operating Income (Loss)	(1)	0
Equity Earnings (Losses) of Subsidiaries	(149)	(257)
Other Income	(10)	(14)
Other Deductions	0	0
Other-Than-Temporary Impairments	0	0
Interest Expense	11	13
Income Tax Benefit (Expense)	0	1
Net Income	(149)	(257)
Comprehensive Income (Loss)	(172)	(294)
Net Cash Provided By (Used In) Operating Activities	(189)	(118)
Net Cash Provided By (Used In) Investing Activities	(29)	62
Net Cash Provided By (Used In) Financing Activities	217	56
Current Assets	(10,996)		(10,712)
Property, Plant and Equipment, net	0		0
Investment in Subsidiaries	(4,973)		(5,050)
Noncurrent Assets	(150)		(141)
Total Assets	(16,119)		(15,903)
Current Liabilities	(10,992)		(10,712)
Noncurrent Liabilities	(153)		(140)
Long-Term Debt	0		0
Member's Equity	(4,974)		(5,051)
TOTAL LIABILITIES AND CAPITALIZATION	$ (16,119)		$ (15,903)