Guarantees Of Debt (Schedule Of Financial Statements Of Guarantors) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating Revenues	$ 2,406	$ 2,402	$ 2,098	$ 2,875	$ 2,636	$ 2,620	$ 2,469	$ 3,354	$ 9,781	$ 11,079	$ 11,793
Operating Expenses									7,503	8,337	8,856
Operating Income (Loss)	468	594	433	783	709	556	621	856	2,278	2,742	2,937
Equity Earnings (Losses) of Subsidiaries									12	4	4
Other Income									260	220	221
Other Deductions									(98)	(85)	(63)
Other-Than-Temporary Impairments									(18)	(22)	(11)
Interest Expense									(423)	(475)	(472)
Income Tax Benefit (Expense)									(736)	(977)	(1,059)
Income (Loss) on Discontinued Operations, net of tax	0	0	0	0	0	29	3	64	0	96	7
Net Income	224	347	211	493	360	294	323	526	1,275	1,503	1,564
Net Cash Provided By (Used In) Operating Activities									2,787	3,557	2,164
Net Cash Provided By (Used In) Investing Activities									(2,625)	(1,269)	(1,669)
Net Cash Provided By (Used In) Financing Activities									(617)	(1,734)	(565)
Current Assets	3,869				3,911				3,869	3,911
Property, Plant and Equipment, net	19,736				17,849				19,736	17,849
Noncurrent Assets	8,120				8,061				8,120	8,061
Total Assets	31,725				29,821				31,725	29,821
Current Liabilities	3,777				2,957				3,777	2,957
Noncurrent Liabilities	10,480				9,131				10,480	9,131
Long-Term Debt	6,687				7,461				6,687	7,461
Member's Equity	10,781				10,272				10,781	10,272	9,641	8,798
TOTAL LIABILITIES AND CAPITALIZATION	31,725				29,821				31,725	29,821
Power [Member]
Operating Revenues	1,281	1,038	985	1,561	1,493	1,398	1,285	1,967	4,865	6,143	6,558
Operating Expenses									3,742	4,372	4,595
Operating Income (Loss)	219	267	196	441	432	483	355	501	1,123	1,771	1,963
Other Income									199	190	170
Other Deductions									(90)	(79)	(53)
Other-Than-Temporary Impairments									(18)	(20)	(9)
Interest Expense									(134)	(175)	(157)
Income Tax Benefit (Expense)									(433)	(685)	(778)
Income (Loss) on Discontinued Operations, net of tax	0	0	0	0	0	29	3	64	0	96	7
Net Income	109	181	104	253	226	302	208	362	647	1,098	1,143
Net Cash Provided By (Used In) Operating Activities									1,379	1,812	1,566
Net Cash Provided By (Used In) Investing Activities									(348)	(578)	(1,205)
Net Cash Provided By (Used In) Financing Activities									(1,036)	(1,233)	(414)
Current Assets	2,234				2,687				2,234	2,687
Property, Plant and Equipment, net	7,018				6,731				7,018	6,731
Noncurrent Assets	1,780				1,669				1,780	1,669
Total Assets	11,032				11,087				11,032	11,087
Current Liabilities	967				902				967	902
Noncurrent Liabilities	2,586				2,056				2,586	2,056
Long-Term Debt	2,040				2,685				2,040	2,685
Member's Equity	5,439				5,444				5,439	5,444	5,027	4,467
TOTAL LIABILITIES AND CAPITALIZATION	11,032				11,087				11,032	11,087
Power Senior Notes [Member]
Operating Revenues									4,865	6,143	6,558
Operating Expenses									3,742	4,372	4,595
Operating Income (Loss)									1,123	1,771	1,963
Equity Earnings (Losses) of Subsidiaries									0	0	0
Other Income									199	190	170
Other Deductions									(90)	(79)	(53)
Other-Than-Temporary Impairments									(18)	(20)	(9)
Interest Expense									(134)	(175)	(157)
Income Tax Benefit (Expense)									(433)	(685)	(778)
Income (Loss) on Discontinued Operations, net of tax										96	7
Net Income									647	1,098	1,143
Comprehensive Income (Loss)									595	917	1,109
Net Cash Provided By (Used In) Operating Activities									1,379	1,812	1,566
Net Cash Provided By (Used In) Investing Activities									(348)	(578)	(1,205)
Net Cash Provided By (Used In) Financing Activities									(1,036)	(1,233)	(414)
Current Assets	2,234				2,687				2,234	2,687
Property, Plant and Equipment, net	7,018				6,731				7,018	6,731
Investment in Subsidiaries	0				0				0	0
Noncurrent Assets	1,780				1,669				1,780	1,669
Total Assets	11,032				11,087				11,032	11,087
Current Liabilities	967				902				967	902
Noncurrent Liabilities	2,586				2,056				2,586	2,056
Long-Term Debt	2,040				2,685				2,040	2,685
Member's Equity	5,439				5,444				5,439	5,444
TOTAL LIABILITIES AND CAPITALIZATION	11,032				11,087				11,032	11,087
Power Senior Notes [Member] | Guarantor Subsidiaries [Member]
Operating Revenues									6,238	7,452	7,746
Operating Expenses									5,118	5,673	5,760
Operating Income (Loss)									1,120	1,779	1,986
Equity Earnings (Losses) of Subsidiaries									(10)	92	(15)
Other Income									206	195	170
Other Deductions									(59)	(51)	(49)
Other-Than-Temporary Impairments									(18)	(19)	(9)
Interest Expense									(51)	(56)	(67)
Income Tax Benefit (Expense)									(501)	(762)	(834)
Income (Loss) on Discontinued Operations, net of tax										0	0
Net Income									687	1,178	1,182
Comprehensive Income (Loss)									681	1,055	1,130
Net Cash Provided By (Used In) Operating Activities									1,562	2,427	2,249
Net Cash Provided By (Used In) Investing Activities									(1,206)	(1,171)	(1,567)
Net Cash Provided By (Used In) Financing Activities									(361)	(1,256)	(687)
Current Assets	8,084				7,248				8,084	7,248
Property, Plant and Equipment, net	5,988				5,715				5,988	5,715
Investment in Subsidiaries	733				804				733	804
Noncurrent Assets	1,660				1,557				1,660	1,557
Total Assets	16,465				15,324				16,465	15,324
Current Liabilities	10,187				9,549				10,187	9,549
Noncurrent Liabilities	1,960				1,589				1,960	1,589
Long-Term Debt	0				0				0	0
Member's Equity	4,318				4,186				4,318	4,186
TOTAL LIABILITIES AND CAPITALIZATION	16,465				15,324				16,465	15,324
Power Senior Notes [Member] | Other Subsidiaries [Member]
Operating Revenues									125	146	125
Operating Expenses									115	150	139
Operating Income (Loss)									10	(4)	(14)
Equity Earnings (Losses) of Subsidiaries									0	0	0
Other Income									0	0	0
Other Deductions									0	0	0
Other-Than-Temporary Impairments									0	0	0
Interest Expense									(18)	(18)	(22)
Income Tax Benefit (Expense)									(2)	14	14
Income (Loss) on Discontinued Operations, net of tax										97	7
Net Income									(10)	89	(15)
Comprehensive Income (Loss)									(10)	89	(15)
Net Cash Provided By (Used In) Operating Activities									(7)	(284)	28
Net Cash Provided By (Used In) Investing Activities									(27)	594	(34)
Net Cash Provided By (Used In) Financing Activities									33	(309)	(40)
Current Assets	940				951				940	951
Property, Plant and Equipment, net	950				950				950	950
Investment in Subsidiaries	0				0				0	0
Noncurrent Assets	60				51				60	51
Total Assets	1,950				1,952				1,950	1,952
Current Liabilities	1,010				1,003				1,010	1,003
Noncurrent Liabilities	207				145				207	145
Long-Term Debt	0				0				0	0
Member's Equity	733				804				733	804
TOTAL LIABILITIES AND CAPITALIZATION	1,950				1,952				1,950	1,952
Power Senior Notes [Member] | Consolidating Adjustments [Member]
Operating Revenues									(1,498)	(1,455)	(1,313)
Operating Expenses									(1,498)	(1,456)	(1,313)
Operating Income (Loss)									0	1	0
Equity Earnings (Losses) of Subsidiaries									(678)	(1,267)	(1,167)
Other Income									(52)	(45)	(45)
Other Deductions									0	0	0
Other-Than-Temporary Impairments									0	0	0
Interest Expense									53	45	45
Income Tax Benefit (Expense)									0	0	0
Income (Loss) on Discontinued Operations, net of tax										(1)	0
Net Income									(677)	(1,267)	(1,167)
Comprehensive Income (Loss)									(671)	(1,144)	(1,115)
Net Cash Provided By (Used In) Operating Activities									(474)	(940)	(1,178)
Net Cash Provided By (Used In) Investing Activities									170	(597)	648
Net Cash Provided By (Used In) Financing Activities									305	1,537	529
Current Assets	(10,712)				(9,823)				(10,712)	(9,823)
Property, Plant and Equipment, net	0				0				0	0
Investment in Subsidiaries	(5,050)				(4,989)				(5,050)	(4,989)
Noncurrent Assets	(141)				(118)				(141)	(118)
Total Assets	(15,903)				(14,930)				(15,903)	(14,930)
Current Liabilities	(10,712)				(9,822)				(10,712)	(9,822)
Noncurrent Liabilities	(140)				(118)				(140)	(118)
Long-Term Debt	0				0				0	0
Member's Equity	(5,051)				(4,990)				(5,051)	(4,990)
TOTAL LIABILITIES AND CAPITALIZATION	(15,903)				(14,930)				(15,903)	(14,930)
Power Parent [Member] | Power Senior Notes [Member] | Power [Member]
Operating Revenues									0	0	0
Operating Expenses									7	5	9
Operating Income (Loss)									(7)	(5)	(9)
Equity Earnings (Losses) of Subsidiaries									688	1,175	1,182
Other Income									45	40	45
Other Deductions									(31)	(28)	(4)
Other-Than-Temporary Impairments									0	(1)	0
Interest Expense									(118)	(146)	(113)
Income Tax Benefit (Expense)									70	63	42
Income (Loss) on Discontinued Operations, net of tax											0
Net Income									647	1,098	1,143
Comprehensive Income (Loss)									595	917	1,109
Net Cash Provided By (Used In) Operating Activities									298	609	467
Net Cash Provided By (Used In) Investing Activities									715	596	(252)
Net Cash Provided By (Used In) Financing Activities									(1,013)	(1,205)	(216)
Current Assets	3,922				4,311				3,922	4,311
Property, Plant and Equipment, net	80				66				80	66
Investment in Subsidiaries	4,317				4,185				4,317	4,185
Noncurrent Assets	201				179				201	179
Total Assets	8,520				8,741				8,520	8,741
Current Liabilities	482				172				482	172
Noncurrent Liabilities	559				440				559	440
Long-Term Debt	2,040				2,685				2,040	2,685
Member's Equity	5,439				5,444				5,439	5,444
TOTAL LIABILITIES AND CAPITALIZATION	$ 8,520				$ 8,741				$ 8,520	$ 8,741