Guarantees Of Debt (Schedule Of Financial Statements Of Guarantors) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Operating Revenues	$ 2,310	$ 2,098	$ 5,096	$ 4,973
Operating Expenses	1,698	1,665	3,874	3,757
Operating Income (Loss)	612	433	1,222	1,216
Equity Earnings (Losses) of Subsidiaries	3	2	5	2
Other Income	52	51	113	95
Other Deductions	(13)	(19)	(42)	(35)
Other-Than-Temporary Impairments	(2)	(7)	(4)	(12)
Interest Expense	(101)	(103)	(203)	(204)
Income Tax Expense	(218)	(146)	(438)	(358)
Net Income	333	211	653	704
Net Cash Provided By (Used In) Operating Activities			1,343	1,378
Net Cash Provided By (Used In) Investing Activities			(1,379)	(1,339)
Net Cash Provided By (Used In) Financing Activities			(179)	(108)
Current Assets	3,615		3,615		3,869
Property, Plant and Equipment, net	20,561		20,561		19,736
Noncurrent Assets	7,883		7,883		8,120
Total Assets	32,059		32,059		31,725
Current Liabilities	3,058		3,058		3,777
Noncurrent Liabilities	10,462		10,462		10,480
Long-Term Debt	7,442		7,442		6,687
Member's Equity	11,097		11,097		10,781
TOTAL LIABILITIES AND CAPITALIZATION	32,059		32,059		31,725
Power [Member]
Operating Revenues	1,190	985	2,637	2,546
Operating Expenses	841	789	2,047	1,909
Operating Income (Loss)	349	196	590	637
Other Income	35	37	82	67
Other Deductions	(10)	(17)	(38)	(32)
Other-Than-Temporary Impairments	(2)	(7)	(4)	(12)
Interest Expense	(29)	(32)	(59)	(62)
Income Tax Expense	(139)	(73)	(230)	(241)
Net Income	204	104	341	357
Net Cash Provided By (Used In) Operating Activities			854	852
Net Cash Provided By (Used In) Investing Activities			(55)	(189)
Net Cash Provided By (Used In) Financing Activities			(802)	(673)
Current Assets	1,746		1,746		2,234
Property, Plant and Equipment, net	6,954		6,954		7,018
Noncurrent Assets	1,870		1,870		1,780
Total Assets	10,570		10,570		11,032
Current Liabilities	551		551		967
Noncurrent Liabilities	2,673		2,673		2,586
Long-Term Debt	2,041		2,041		2,040
Member's Equity	5,305		5,305		5,439
TOTAL LIABILITIES AND CAPITALIZATION	10,570		10,570		11,032
Power Senior Notes [Member] | Power Parent [Member]
Operating Revenues	0	0	0	0
Operating Expenses	2	2	4	0
Operating Income (Loss)	(2)	(2)	(4)	0
Equity Earnings (Losses) of Subsidiaries	213	116	362	376
Other Income	10	11	19	24
Other Deductions	(2)	0	(10)	(7)
Other-Than-Temporary Impairments	0	0	0	0
Interest Expense	(26)	(31)	(53)	(60)
Income Tax Expense	11	10	27	24
Net Income	204	104	341	357
Comprehensive Income (Loss)	197	86	366	383
Net Cash Provided By (Used In) Operating Activities			386	301
Net Cash Provided By (Used In) Investing Activities			152	365
Net Cash Provided By (Used In) Financing Activities			(538)	(666)
Current Assets	3,981		3,981		3,922
Property, Plant and Equipment, net	80		80		80
Investment in Subsidiaries	4,188		4,188		4,317
Noncurrent Assets	189		189		201
Total Assets	8,438		8,438		8,520
Current Liabilities	583		583		482
Noncurrent Liabilities	509		509		559
Long-Term Debt	2,041		2,041		2,040
Member's Equity	5,305		5,305		5,439
TOTAL LIABILITIES AND CAPITALIZATION	8,438		8,438		8,520
Power Senior Notes [Member] | Power [Member]
Operating Revenues	1,190	985	2,637	2,546
Operating Expenses	841	789	2,047	1,909
Operating Income (Loss)	349	196	590	637
Equity Earnings (Losses) of Subsidiaries	0	0	0	0
Other Income	35	37	82	67
Other Deductions	(10)	(17)	(38)	(32)
Other-Than-Temporary Impairments	(2)	(7)	(4)	(12)
Interest Expense	(29)	(32)	(59)	(62)
Income Tax Expense	(139)	(73)	(230)	(241)
Net Income	204	104	341	357
Comprehensive Income (Loss)	197	86	366	383
Net Cash Provided By (Used In) Operating Activities			854	852
Net Cash Provided By (Used In) Investing Activities			(55)	(189)
Net Cash Provided By (Used In) Financing Activities			(802)	(673)
Current Assets	1,746		1,746		2,234
Property, Plant and Equipment, net	6,954		6,954		7,018
Investment in Subsidiaries	0		0		0
Noncurrent Assets	1,870		1,870		1,780
Total Assets	10,570		10,570		11,032
Current Liabilities	551		551		967
Noncurrent Liabilities	2,673		2,673		2,586
Long-Term Debt	2,041		2,041		2,040
Member's Equity	5,305		5,305		5,439
TOTAL LIABILITIES AND CAPITALIZATION	10,570		10,570		11,032
Power Senior Notes [Member] | Guarantor Subsidiaries [Member]
Operating Revenues	1,535	1,329	3,338	3,202
Operating Expenses	1,187	1,135	2,749	2,568
Operating Income (Loss)	348	194	589	634
Equity Earnings (Losses) of Subsidiaries	(2)	(1)	(2)	(4)
Other Income	35	39	83	70
Other Deductions	(9)	(17)	(29)	(25)
Other-Than-Temporary Impairments	(2)	(7)	(4)	(12)
Interest Expense	(6)	(10)	(16)	(20)
Income Tax Expense	(151)	(82)	(259)	(267)
Net Income	213	116	362	376
Comprehensive Income (Loss)	198	91	370	388
Net Cash Provided By (Used In) Operating Activities			884	902
Net Cash Provided By (Used In) Investing Activities			(411)	(601)
Net Cash Provided By (Used In) Financing Activities			(476)	(310)
Current Assets	8,288		8,288		8,084
Property, Plant and Equipment, net	5,944		5,944		5,988
Investment in Subsidiaries	731		731		733
Noncurrent Assets	1,750		1,750		1,660
Total Assets	16,713		16,713		16,465
Current Liabilities	10,443		10,443		10,187
Noncurrent Liabilities	2,081		2,081		1,960
Long-Term Debt	0		0		0
Member's Equity	4,189		4,189		4,318
TOTAL LIABILITIES AND CAPITALIZATION	16,713		16,713		16,465
Power Senior Notes [Member] | Consolidating Adjustments [Member]
Operating Revenues	(379)	(375)	(768)	(713)
Operating Expenses	(379)	(376)	(767)	(714)
Operating Income (Loss)	0	1	(1)	1
Equity Earnings (Losses) of Subsidiaries	(211)	(115)	(360)	(372)
Other Income	(10)	(13)	(20)	(27)
Other Deductions	1	0	1	0
Other-Than-Temporary Impairments	0	0	0	0
Interest Expense	9	13	20	26
Income Tax Expense	0	(1)	0	0
Net Income	(211)	(115)	(360)	(372)
Comprehensive Income (Loss)	(198)	(90)	(370)	(384)
Net Cash Provided By (Used In) Operating Activities			(419)	(354)
Net Cash Provided By (Used In) Investing Activities			204	70
Net Cash Provided By (Used In) Financing Activities			215	284
Current Assets	(11,367)		(11,367)		(10,712)
Property, Plant and Equipment, net	0		0		0
Investment in Subsidiaries	(4,919)		(4,919)		(5,050)
Noncurrent Assets	(125)		(125)		(141)
Total Assets	(16,411)		(16,411)		(15,903)
Current Liabilities	(11,366)		(11,366)		(10,712)
Noncurrent Liabilities	(124)		(124)		(140)
Long-Term Debt	0		0		0
Member's Equity	(4,921)		(4,921)		(5,051)
TOTAL LIABILITIES AND CAPITALIZATION	(16,411)		(16,411)		(15,903)
Power Senior Notes [Member] | Non-Guarantor Subsidiaries [Member]
Operating Revenues	34	31	67	57
Operating Expenses	31	28	61	55
Operating Income (Loss)	3	3	6	2
Equity Earnings (Losses) of Subsidiaries	0	0	0	0
Other Income	0	0	0	0
Other Deductions	0	0	0	0
Other-Than-Temporary Impairments	0	0	0	0
Interest Expense	(6)	(4)	(10)	(8)
Income Tax Expense	1	0	2	2
Net Income	(2)	(1)	(2)	(4)
Comprehensive Income (Loss)	0	(1)	0	(4)
Net Cash Provided By (Used In) Operating Activities			3	3
Net Cash Provided By (Used In) Investing Activities			0	(23)
Net Cash Provided By (Used In) Financing Activities			(3)	19
Current Assets	844		844		940
Property, Plant and Equipment, net	930		930		950
Investment in Subsidiaries	0		0		0
Noncurrent Assets	56		56		60
Total Assets	1,830		1,830		1,950
Current Liabilities	891		891		1,010
Noncurrent Liabilities	207		207		207
Long-Term Debt	0		0		0
Member's Equity	732		732		733
TOTAL LIABILITIES AND CAPITALIZATION	$ 1,830		$ 1,830		$ 1,950