Guarantees Of Debt (Schedule Of Financial Statements Of Guarantors) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Subsidiary or Equity Method Investee [Line Items]
Operating Revenues	$ 2,773	$ 2,641	$ 2,249	$ 3,223	$ 2,318	$ 2,554	$ 2,310	$ 2,786	$ 10,886	$ 9,968	$ 9,781
Operating Expenses									8,263	7,669	7,503
Operating Income (Loss)	807	746	365	705	365	712	612	610	2,623	2,299	2,278
Equity Earnings (Losses) of Subsidiaries									13	11	12
Other Income									290	213	260
Other Deductions									(61)	(54)	(98)
Other than Temporary Impairments									20	12	18
Interest Expense									(389)	(402)	(423)
Income Tax Benefit (Expense)									(938)	(812)	(736)
Net Income									1,518	1,243	1,275
Net Cash Provided By (Used In) Operating Activities									3,160	3,158	2,787
Net Cash Provided By (Used In) Investing Activities									(2,892)	(2,801)	(2,625)
Net Cash Provided By (Used In) Financing Activities									(359)	(243)	(617)
Current Assets	4,119				3,614				4,119	3,614
Property, Plant and Equipment, net	23,589				21,645				23,589	21,645
Noncurrent Assets	7,625				7,263				7,625	7,263
Total Assets	35,333				32,522				35,333	32,522
Current Liabilities	3,478				3,063				3,478	3,063
Noncurrent Liabilities	11,408				9,988				11,408	9,988
Total Long-Term Debt	8,261				7,862				8,261	7,862
Member's Equity	12,186				11,609				12,186	11,609	10,781	10,272
TOTAL LIABILITIES AND CAPITALIZATION	35,333				32,522				35,333	32,522
Power [Member]
Subsidiary or Equity Method Investee [Line Items]
Operating Revenues	1,610	1,138	986	1,700	1,245	1,174	1,193	1,451	5,434	5,063	4,873
Operating Expenses									4,225	3,993	3,750
Operating Income (Loss)	507	353	67	282	107	370	351	242	1,209	1,070	1,123
Equity Earnings (Losses) of Subsidiaries									14	16	15
Other Income									222	154	201
Other Deductions									(52)	(49)	(90)
Other than Temporary Impairments									20	12	18
Interest Expense									(122)	(116)	(132)
Income Tax Benefit (Expense)									(491)	(419)	(433)
Net Income									760	644	666
Net Cash Provided By (Used In) Operating Activities									1,425	1,347	1,453
Net Cash Provided By (Used In) Investing Activities									(524)	(861)	(472)
Net Cash Provided By (Used In) Financing Activities									(898)	(487)	(986)
Current Assets	2,359				2,476				2,359	2,476
Property, Plant and Equipment, net	7,515				7,367				7,515	7,367
Noncurrent Assets	2,172				2,159				2,172	2,159
Total Assets	12,046				12,002				12,046	12,002
Current Liabilities	1,184				800				1,184	800
Noncurrent Liabilities	3,061				2,847				3,061	2,847
Total Long-Term Debt	2,243				2,497				2,243	2,497
Member's Equity	5,558				5,858				5,558	5,858	5,630	5,566
TOTAL LIABILITIES AND CAPITALIZATION	12,046				12,002				12,046	12,002
Power Senior Notes [Member]
Subsidiary or Equity Method Investee [Line Items]
Operating Revenues									5,434	5,063	4,873
Operating Expenses									4,225	3,993	3,750
Operating Income (Loss)									1,209	1,070	1,123
Equity Earnings (Losses) of Subsidiaries									14	16	15
Other Income									222	154	201
Other Deductions									(52)	(49)	(90)
Other than Temporary Impairments									20	12	18
Interest Expense									(122)	(116)	(132)
Income Tax Benefit (Expense)									(491)	(419)	(433)
Net Income									760	644	666
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									595	909	614
Net Cash Provided By (Used In) Operating Activities									1,425	1,347	1,453
Net Cash Provided By (Used In) Investing Activities									(524)	(861)	(472)
Net Cash Provided By (Used In) Financing Activities									(898)	(487)	(986)
Current Assets	2,359				2,476				2,359	2,476
Property, Plant and Equipment, net	7,515				7,367				7,515	7,367
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0				0				0	0
Noncurrent Assets	2,172				2,159				2,172	2,159
Total Assets	12,046				12,002				12,046	12,002
Current Liabilities	1,184				800				1,184	800
Noncurrent Liabilities	3,061				2,847				3,061	2,847
Total Long-Term Debt	2,243				2,497				2,243	2,497
Member's Equity	5,558				5,858				5,558	5,858
TOTAL LIABILITIES AND CAPITALIZATION	12,046				12,002				12,046	12,002
Power Senior Notes [Member] | Guarantor Subsidiaries [Member]
Subsidiary or Equity Method Investee [Line Items]
Operating Revenues									5,390	5,022	4,850
Operating Expenses									4,175	3,945	3,730
Operating Income (Loss)									1,215	1,077	1,120
Equity Earnings (Losses) of Subsidiaries									(5)	(5)	(10)
Other Income									222	157	206
Other Deductions									(32)	(35)	(59)
Other than Temporary Impairments									20	12	18
Interest Expense									(35)	(42)	(51)
Income Tax Benefit (Expense)									(558)	(474)	(501)
Net Income									787	666	687
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									768	713	681
Net Cash Provided By (Used In) Operating Activities									1,674	1,503	1,562
Net Cash Provided By (Used In) Investing Activities									(856)	(1,092)	(1,206)
Net Cash Provided By (Used In) Financing Activities									(818)	(412)	(361)
Current Assets	2,037				2,076				2,037	2,076
Property, Plant and Equipment, net	6,265				6,108				6,265	6,108
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	120				124				120	124
Noncurrent Assets	1,952				1,847				1,952	1,847
Total Assets	10,374				10,155				10,374	10,155
Current Liabilities	3,606				3,474				3,606	3,474
Noncurrent Liabilities	2,442				2,247				2,442	2,247
Total Long-Term Debt	0				0				0	0
Member's Equity	4,326				4,434				4,326	4,434
TOTAL LIABILITIES AND CAPITALIZATION	10,374				10,155				10,374	10,155
Power Senior Notes [Member] | Non-Guarantor Subsidiaries [Member]
Subsidiary or Equity Method Investee [Line Items]
Operating Revenues									153	190	135
Operating Expenses									143	174	125
Operating Income (Loss)									10	16	10
Equity Earnings (Losses) of Subsidiaries									14	16	15
Other Income									0	0	2
Other Deductions									0	0	0
Other than Temporary Impairments									0	0	0
Interest Expense									(19)	(19)	(16)
Income Tax Benefit (Expense)									2	0	(2)
Net Income									7	13	9
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									7	11	9
Net Cash Provided By (Used In) Operating Activities									76	82	67
Net Cash Provided By (Used In) Investing Activities									(42)	(71)	(151)
Net Cash Provided By (Used In) Financing Activities									(32)	(11)	83
Current Assets	150				102				150	102
Property, Plant and Equipment, net	1,169				1,178				1,169	1,178
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0				0				0	0
Noncurrent Assets	137				138				137	138
Total Assets	1,456				1,418				1,456	1,418
Current Liabilities	786				745				786	745
Noncurrent Liabilities	360				338				360	338
Total Long-Term Debt	0				0				0	0
Member's Equity	310				335				310	335
TOTAL LIABILITIES AND CAPITALIZATION	1,456				1,418				1,456	1,418
Power Senior Notes [Member] | Consolidation, Eliminations [Member]
Subsidiary or Equity Method Investee [Line Items]
Operating Revenues									(109)	(149)	(112)
Operating Expenses									(109)	(149)	(112)
Operating Income (Loss)									0	0	0
Equity Earnings (Losses) of Subsidiaries									(794)	(679)	(697)
Other Income									(34)	(38)	(52)
Other Deductions									0	0	0
Other than Temporary Impairments									0	0	0
Interest Expense									34	38	53
Income Tax Benefit (Expense)									0	0	0
Net Income									(794)	(679)	(696)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									(775)	(724)	(690)
Net Cash Provided By (Used In) Operating Activities									(902)	(526)	(474)
Net Cash Provided By (Used In) Investing Activities									226	697	899
Net Cash Provided By (Used In) Financing Activities									676	(171)	(424)
Current Assets	(4,091)				(4,115)				(4,091)	(4,115)
Property, Plant and Equipment, net	0				0				0	0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	(4,636)				(4,769)				(4,636)	(4,769)
Noncurrent Assets	(195)				(48)				(195)	(48)
Total Assets	(8,922)				(8,932)				(8,922)	(8,932)
Current Liabilities	(4,091)				(4,116)				(4,091)	(4,116)
Noncurrent Liabilities	(195)				(47)				(195)	(47)
Total Long-Term Debt	0				0				0	0
Member's Equity	(4,636)				(4,769)				(4,636)	(4,769)
TOTAL LIABILITIES AND CAPITALIZATION	(8,922)				(8,932)				(8,922)	(8,932)
Power Senior Notes [Member] | Power Parent [Member]
Subsidiary or Equity Method Investee [Line Items]
Operating Revenues									0	0	0
Operating Expenses									16	23	7
Operating Income (Loss)									(16)	(23)	(7)
Equity Earnings (Losses) of Subsidiaries									799	684	707
Other Income									34	35	45
Other Deductions									(20)	(14)	(31)
Other than Temporary Impairments									0	0	0
Interest Expense									(102)	(93)	(118)
Income Tax Benefit (Expense)									65	55	70
Net Income									760	644	666
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									595	909	614
Net Cash Provided By (Used In) Operating Activities									577	288	298
Net Cash Provided By (Used In) Investing Activities									148	(395)	(14)
Net Cash Provided By (Used In) Financing Activities									(724)	107	(284)
Current Assets	4,263				4,413				4,263	4,413
Property, Plant and Equipment, net	81				81				81	81
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	4,516				4,645				4,516	4,645
Noncurrent Assets	278				222				278	222
Total Assets	9,138				9,361				9,138	9,361
Current Liabilities	883				697				883	697
Noncurrent Liabilities	454				309				454	309
Total Long-Term Debt	2,243				2,497				2,243	2,497
Member's Equity	5,558				5,858				5,558	5,858
TOTAL LIABILITIES AND CAPITALIZATION	9,138				9,361				9,138	9,361
Restatement Adjustment [Member] | Power Senior Notes [Member]
Subsidiary or Equity Method Investee [Line Items]
Operating Revenues										0	0
Operating Expenses										0	0
Net Cash Provided By (Used In) Investing Activities										0	0
Net Cash Provided By (Used In) Financing Activities										0	0
Current Assets					0					0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures					0					0
Total Assets					0					0
Current Liabilities					0					0
Member's Equity					0					0
TOTAL LIABILITIES AND CAPITALIZATION					0					0
Restatement Adjustment [Member] | Power Senior Notes [Member] | Guarantor Subsidiaries [Member]
Subsidiary or Equity Method Investee [Line Items]
Operating Revenues										(1,468)	(1,388)
Operating Expenses										(1,468)	(1,388)
Net Cash Provided By (Used In) Investing Activities										0	0
Net Cash Provided By (Used In) Financing Activities										0	0
Current Assets					(6,840)					(6,840)
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures					(605)					(605)
Total Assets					(7,445)					(7,445)
Current Liabilities					(7,445)					(7,445)
Member's Equity					0					0
TOTAL LIABILITIES AND CAPITALIZATION					(7,445)					(7,445)
Restatement Adjustment [Member] | Power Senior Notes [Member] | Non-Guarantor Subsidiaries [Member]
Subsidiary or Equity Method Investee [Line Items]
Operating Revenues										0	0
Operating Expenses										0	0
Net Cash Provided By (Used In) Investing Activities										0	0
Net Cash Provided By (Used In) Financing Activities										0	0
Current Assets					(842)					(842)
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures					0					0
Total Assets					(842)					(842)
Current Liabilities					(237)					(237)
Member's Equity					(605)					(605)
TOTAL LIABILITIES AND CAPITALIZATION					(842)					(842)
Restatement Adjustment [Member] | Power Senior Notes [Member] | Consolidation, Eliminations [Member]
Subsidiary or Equity Method Investee [Line Items]
Operating Revenues										1,468	1,388
Operating Expenses										1,468	1,388
Net Cash Provided By (Used In) Investing Activities										588	729
Net Cash Provided By (Used In) Financing Activities										(588)	(679)
Current Assets					7,429					7,429
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures					605					605
Total Assets					8,034					8,034
Current Liabilities					7,429					7,429
Member's Equity					605					605
TOTAL LIABILITIES AND CAPITALIZATION					8,034					8,034
Restatement Adjustment [Member] | Power Senior Notes [Member] | Power Parent [Member]
Subsidiary or Equity Method Investee [Line Items]
Operating Revenues										0	0
Operating Expenses										0	0
Net Cash Provided By (Used In) Investing Activities										(588)	(729)
Net Cash Provided By (Used In) Financing Activities										588	679
Current Assets					253					253
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures					0					0
Total Assets					253					253
Current Liabilities					253					253
Member's Equity					0					0
TOTAL LIABILITIES AND CAPITALIZATION					$ 253					$ 253