Guarantees Of Debt (Schedule Of Financial Statements Of Guarantors) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Operating Revenues	$ 2,554	$ 2,402	$ 7,650	$ 7,375
Operating Expenses	1,842	1,808	5,716	5,565
Operating Income (Loss)	712	594	1,934	1,810
Equity Earnings (Losses) of Subsidiaries	4	7	9	9
Other Income	59	121	172	216
Other Deductions	(12)	(26)	(54)	(61)
Other-Than-Temporary Impairments	(3)	(2)	(7)	(14)
Interest Expense	(100)	(106)	(303)	(310)
Income Tax Expense	(270)	(241)	(708)	(599)
Net Income	390	347	1,043	1,051
Net Cash Provided By (Used In) Operating Activities			2,435	2,311
Net Cash Provided By (Used In) Investing Activities			(2,088)	(2,051)
Net Cash Provided By (Used In) Financing Activities			(278)	(314)
Current Assets	3,741		3,741		3,869
Property, Plant and Equipment, net	21,079		21,079		19,736
Noncurrent Assets	7,790		7,790		8,120
Total Assets	32,610		32,610		31,725
Current Liabilities	3,235		3,235		3,777
Noncurrent Liabilities	10,560		10,560		10,480
Long-Term Debt	7,476		7,476		6,687
Member's Equity	11,339		11,339		10,781
TOTAL LIABILITIES AND CAPITALIZATION	32,610		32,610		31,725
Power [Member]
Operating Revenues	1,169	1,038	3,806	3,584
Operating Expenses	800	771	2,847	2,680
Operating Income (Loss)	369	267	959	904
Other Income	45	104	127	171
Other Deductions	(11)	(20)	(49)	(52)
Other-Than-Temporary Impairments	(3)	(2)	(7)	(14)
Interest Expense	(26)	(35)	(85)	(97)
Income Tax Expense	(153)	(133)	(383)	(374)
Net Income	221	181	562	538
Net Cash Provided By (Used In) Operating Activities			1,284	1,172
Net Cash Provided By (Used In) Investing Activities			(290)	(506)
Net Cash Provided By (Used In) Financing Activities			(992)	(673)
Current Assets	1,690		1,690		2,234
Property, Plant and Equipment, net	7,062		7,062		7,018
Noncurrent Assets	1,969		1,969		1,780
Total Assets	10,721		10,721		11,032
Current Liabilities	586		586		967
Noncurrent Liabilities	2,735		2,735		2,586
Long-Term Debt	2,041		2,041		2,040
Member's Equity	5,359		5,359		5,439
TOTAL LIABILITIES AND CAPITALIZATION	10,721		10,721		11,032
Power Senior Notes [Member] | Power Parent [Member]
Operating Revenues	0	0	0	0
Operating Expenses	2	(1)	6	(1)
Operating Income (Loss)	(2)	1	(6)	1
Equity Earnings (Losses) of Subsidiaries	226	191	588	567
Other Income	8	11	27	35
Other Deductions	1	0	(9)	(7)
Other-Than-Temporary Impairments	0	0	0	0
Interest Expense	(19)	(29)	(72)	(89)
Income Tax Expense	7	7	34	31
Net Income	221	181	562	538
Comprehensive Income (Loss)	245	166	611	549
Net Cash Provided By (Used In) Operating Activities			425	409
Net Cash Provided By (Used In) Investing Activities			569	257
Net Cash Provided By (Used In) Financing Activities			(990)	(666)
Current Assets	4,065		4,065		3,922
Property, Plant and Equipment, net	81		81		80
Investment in Subsidiaries	4,331		4,331		4,317
Noncurrent Assets	197		197		201
Total Assets	8,674		8,674		8,520
Current Liabilities	752		752		482
Noncurrent Liabilities	522		522		559
Long-Term Debt	2,041		2,041		2,040
Member's Equity	5,359		5,359		5,439
TOTAL LIABILITIES AND CAPITALIZATION	8,674		8,674		8,520
Power Senior Notes [Member] | Power [Member]
Operating Revenues	1,169	1,038	3,806	3,584
Operating Expenses	800	771	2,847	2,680
Operating Income (Loss)	369	267	959	904
Equity Earnings (Losses) of Subsidiaries	0	0	0	0
Other Income	45	104	127	171
Other Deductions	(11)	(20)	(49)	(52)
Other-Than-Temporary Impairments	(3)	(2)	(7)	(14)
Interest Expense	(26)	(35)	(85)	(97)
Income Tax Expense	(153)	(133)	(383)	(374)
Net Income	221	181	562	538
Comprehensive Income (Loss)	245	166	611	549
Net Cash Provided By (Used In) Operating Activities			1,284	1,172
Net Cash Provided By (Used In) Investing Activities			(290)	(506)
Net Cash Provided By (Used In) Financing Activities			(992)	(673)
Current Assets	1,690		1,690		2,234
Property, Plant and Equipment, net	7,062		7,062		7,018
Investment in Subsidiaries	0		0		0
Noncurrent Assets	1,969		1,969		1,780
Total Assets	10,721		10,721		11,032
Current Liabilities	586		586		967
Noncurrent Liabilities	2,735		2,735		2,586
Long-Term Debt	2,041		2,041		2,040
Member's Equity	5,359		5,359		5,439
TOTAL LIABILITIES AND CAPITALIZATION	10,721		10,721		11,032
Power Senior Notes [Member] | Guarantor Subsidiaries [Member]
Operating Revenues	1,511	1,358	4,849	4,560
Operating Expenses	1,145	1,095	3,894	3,663
Operating Income (Loss)	366	263	955	897
Equity Earnings (Losses) of Subsidiaries	(1)	0	(3)	(4)
Other Income	47	106	130	176
Other Deductions	(11)	(20)	(40)	(45)
Other-Than-Temporary Impairments	(3)	(2)	(7)	(14)
Interest Expense	(13)	(15)	(29)	(35)
Income Tax Expense	(160)	(142)	(419)	(409)
Net Income	225	190	587	566
Comprehensive Income (Loss)	242	168	612	556
Net Cash Provided By (Used In) Operating Activities			1,360	1,259
Net Cash Provided By (Used In) Investing Activities			(869)	(897)
Net Cash Provided By (Used In) Financing Activities			(492)	(368)
Current Assets	8,609		8,609		8,084
Property, Plant and Equipment, net	6,059		6,059		5,988
Investment in Subsidiaries	730		730		733
Noncurrent Assets	1,842		1,842		1,660
Total Assets	17,240		17,240		16,465
Current Liabilities	10,778		10,778		10,187
Noncurrent Liabilities	2,130		2,130		1,960
Long-Term Debt	0		0		0
Member's Equity	4,332		4,332		4,318
TOTAL LIABILITIES AND CAPITALIZATION	17,240		17,240		16,465
Power Senior Notes [Member] | Consolidating Adjustments [Member]
Operating Revenues	(408)	(356)	(1,176)	(1,069)
Operating Expenses	(409)	(355)	(1,176)	(1,069)
Operating Income (Loss)	1	(1)	0	0
Equity Earnings (Losses) of Subsidiaries	(225)	(191)	(585)	(563)
Other Income	(10)	(13)	(30)	(40)
Other Deductions	(1)	0	0	0
Other-Than-Temporary Impairments	0	0	0	0
Interest Expense	10	14	30	40
Income Tax Expense	0	1	0	1
Net Income	(225)	(190)	(585)	(562)
Comprehensive Income (Loss)	(242)	(168)	(610)	(552)
Net Cash Provided By (Used In) Operating Activities			(506)	(493)
Net Cash Provided By (Used In) Investing Activities			11	158
Net Cash Provided By (Used In) Financing Activities			494	335
Current Assets	(11,941)		(11,941)		(10,712)
Property, Plant and Equipment, net	0		0		0
Investment in Subsidiaries	(5,061)		(5,061)		(5,050)
Noncurrent Assets	(126)		(126)		(141)
Total Assets	(17,128)		(17,128)		(15,903)
Current Liabilities	(11,941)		(11,941)		(10,712)
Noncurrent Liabilities	(125)		(125)		(140)
Long-Term Debt	0		0		0
Member's Equity	(5,062)		(5,062)		(5,051)
TOTAL LIABILITIES AND CAPITALIZATION	(17,128)		(17,128)		(15,903)
Power Senior Notes [Member] | Non-Guarantor Subsidiaries [Member]
Operating Revenues	66	36	133	93
Operating Expenses	62	32	123	87
Operating Income (Loss)	4	4	10	6
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	(4)	(5)	(14)	(13)
Income Tax Expense	0	1	2	3
Net Income	0	0	(2)	(4)
Comprehensive Income (Loss)	0	0	(2)	(4)
Net Cash Provided By (Used In) Operating Activities			5	(3)
Net Cash Provided By (Used In) Investing Activities			(1)	(24)
Net Cash Provided By (Used In) Financing Activities			(4)	26
Current Assets	957		957		940
Property, Plant and Equipment, net	922		922		950
Investment in Subsidiaries	0		0		0
Noncurrent Assets	56		56		60
Total Assets	1,935		1,935		1,950
Current Liabilities	997		997		1,010
Noncurrent Liabilities	208		208		207
Long-Term Debt	0		0		0
Member's Equity	730		730		733
TOTAL LIABILITIES AND CAPITALIZATION	$ 1,935		$ 1,935		$ 1,950