Guarantees Of Debt (Schedule Of Financial Statements Of Guarantors) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Debt Instrument [Line Items]
Operating Revenues	$ 2,314	$ 2,249	$ 5,449	$ 5,472
Operating Expenses	1,746	1,884	3,833	4,402
Operating Income (Loss)	568	365	1,616	1,070
Equity Earnings (Losses) of Subsidiaries	4	3	7	7
Other Income	76	62	124	110
Other Deductions	(10)	(10)	(22)	(22)
Other-Than Temporary Impairments	10	2	15	4
Interest Expense	(97)	(94)	(195)	(191)
Income Tax Expense	(186)	(112)	(584)	(372)
Net Income	345	212	931	598
Net Cash Provided By (Used In) Operating Activities			2,234	1,448
Net Cash Provided By (Used In) Investing Activities			(1,773)	(1,282)
Net Cash Provided By (Used In) Financing Activities			(266)	(89)
Current Assets	3,627		3,627		$ 4,119
Property, Plant and Equipment, net	24,807		24,807		23,589
Noncurrent Assets	7,778		7,778		7,625
Total Assets	36,212		36,212		35,333
Current Liabilities	3,107		3,107		3,478
Noncurrent Liabilities	11,708		11,708		11,408
Long-Term Debt	8,689		8,689		8,261
Member's Equity	12,708		12,708		12,186
TOTAL LIABILITIES AND CAPITALIZATION	36,212		36,212		35,333
Power Senior Notes [Member]
Debt Instrument [Line Items]
Operating Revenues	1,025	986	2,750	2,686
Operating Expenses	797	919	1,938	2,337
Operating Income (Loss)	228	67	812	349
Equity Earnings (Losses) of Subsidiaries	5	3	8	7
Other Income	55	46	84	79
Other Deductions	(7)	(9)	(18)	(19)
Other-Than Temporary Impairments	10	2	15	4
Interest Expense	(33)	(29)	(64)	(61)
Income Tax Expense	(72)	(22)	(306)	(133)
Net Income	166	54	501	218
Comprehensive Income (Loss)	159	67	506	237
Net Cash Provided By (Used In) Operating Activities			1,292	814
Net Cash Provided By (Used In) Investing Activities			(887)	(236)
Net Cash Provided By (Used In) Financing Activities			(402)	(578)
Current Assets	2,211		2,211		2,359
Property, Plant and Equipment, net	7,707		7,707		7,515
Investment in Subsidiaries	0		0		0
Noncurrent Assets	2,248		2,248		2,172
Total Assets	12,166		12,166		12,046
Current Liabilities	1,077		1,077		1,184
Noncurrent Liabilities	3,181		3,181		3,061
Long-Term Debt	2,244		2,244		2,243
Member's Equity	5,664		5,664		5,558
TOTAL LIABILITIES AND CAPITALIZATION	12,166		12,166		12,046
Power Senior Notes [Member] | Power Parent [Member]
Debt Instrument [Line Items]
Operating Revenues	0	0	0	0
Operating Expenses	(1)	5	4	9
Operating Income (Loss)	1	(5)	(4)	(9)
Equity Earnings (Losses) of Subsidiaries	186	57	535	234
Other Income	12	8	23	16
Other Deductions	(1)	0	(1)	(4)
Other-Than Temporary Impairments	0	0	0	0
Interest Expense	(33)	(27)	(62)	(55)
Income Tax Expense	1	21	10	36
Net Income	166	54	501	218
Comprehensive Income (Loss)	159	67	506	237
Net Cash Provided By (Used In) Operating Activities			410	292
Net Cash Provided By (Used In) Investing Activities			(480)	138
Net Cash Provided By (Used In) Financing Activities			70	(430)
Current Assets	4,613		4,613		4,263
Property, Plant and Equipment, net	80		80		81
Investment in Subsidiaries	4,409		4,409		4,516
Noncurrent Assets	258		258		278
Total Assets	9,360		9,360		9,138
Current Liabilities	987		987		883
Noncurrent Liabilities	465		465		454
Long-Term Debt	2,244		2,244		2,243
Member's Equity	5,664		5,664		5,558
TOTAL LIABILITIES AND CAPITALIZATION	9,360		9,360		9,138
Power Senior Notes [Member] | Guarantor Subsidiaries [Member]
Debt Instrument [Line Items]
Operating Revenues	1,012	972	2,727	2,656
Operating Expenses	787	903	1,918	2,307
Operating Income (Loss)	225	69	809	349
Equity Earnings (Losses) of Subsidiaries	(1)	(3)	(2)	(3)
Other Income	55	47	85	80
Other Deductions	(6)	(8)	(17)	(14)
Other-Than Temporary Impairments	10	2	15	4
Interest Expense	(7)	(6)	(16)	(13)
Income Tax Expense	(73)	(43)	(315)	(168)
Net Income	183	54	529	227
Comprehensive Income (Loss)	169	66	520	242
Net Cash Provided By (Used In) Operating Activities			1,508	950
Net Cash Provided By (Used In) Investing Activities			(963)	(415)
Net Cash Provided By (Used In) Financing Activities			(543)	(534)
Current Assets	1,678		1,678		2,037
Property, Plant and Equipment, net	6,290		6,290		6,265
Investment in Subsidiaries	289		289		120
Noncurrent Assets	2,026		2,026		1,952
Total Assets	10,283		10,283		10,374
Current Liabilities	3,532		3,532		3,606
Noncurrent Liabilities	2,534		2,534		2,442
Long-Term Debt	0		0		0
Member's Equity	4,217		4,217		4,326
TOTAL LIABILITIES AND CAPITALIZATION	10,283		10,283		10,374
Power Senior Notes [Member] | Non-Guarantor Subsidiaries [Member]
Debt Instrument [Line Items]
Operating Revenues	39	42	107	82
Operating Expenses	37	40	100	74
Operating Income (Loss)	2	2	7	8
Equity Earnings (Losses) of Subsidiaries	5	3	8	7
Other Income	0	0	0	0
Other Deductions	0	0	0	0
Other-Than Temporary Impairments	0	0	0	0
Interest Expense	(5)	(5)	(10)	(10)
Income Tax Expense	0	0	(1)	(1)
Net Income	2	0	4	4
Comprehensive Income (Loss)	2	0	4	4
Net Cash Provided By (Used In) Operating Activities			61	32
Net Cash Provided By (Used In) Investing Activities			(210)	(16)
Net Cash Provided By (Used In) Financing Activities			150	(17)
Current Assets	136		136		150
Property, Plant and Equipment, net	1,337		1,337		1,169
Investment in Subsidiaries	0		0		0
Noncurrent Assets	132		132		137
Total Assets	1,605		1,605		1,456
Current Liabilities	774		774		786
Noncurrent Liabilities	350		350		360
Long-Term Debt	0		0		0
Member's Equity	481		481		310
TOTAL LIABILITIES AND CAPITALIZATION	1,605		1,605		1,456
Power Senior Notes [Member] | Consolidating Adjustments [Member]
Debt Instrument [Line Items]
Operating Revenues	(26)	(28)	(84)	(52)
Operating Expenses	(26)	(29)	(84)	(53)
Operating Income (Loss)	0	1	0	1
Equity Earnings (Losses) of Subsidiaries	(185)	(54)	(533)	(231)
Other Income	(12)	(9)	(24)	(17)
Other Deductions	0	(1)	0	(1)
Other-Than Temporary Impairments	0	0	0	0
Interest Expense	12	9	24	17
Income Tax Expense	0	0	0	0
Net Income	(185)	(54)	(533)	(231)
Comprehensive Income (Loss)	(171)	$ (66)	(524)	(246)
Net Cash Provided By (Used In) Operating Activities			(687)	(460)
Net Cash Provided By (Used In) Investing Activities			766	57
Net Cash Provided By (Used In) Financing Activities			(79)	$ 403
Current Assets	(4,216)		(4,216)		(4,091)
Property, Plant and Equipment, net	0		0		0
Investment in Subsidiaries	(4,698)		(4,698)		(4,636)
Noncurrent Assets	(168)		(168)		(195)
Total Assets	(9,082)		(9,082)		(8,922)
Current Liabilities	(4,216)		(4,216)		(4,091)
Noncurrent Liabilities	(168)		(168)		(195)
Long-Term Debt	0		0		0
Member's Equity	(4,698)		(4,698)		(4,636)
TOTAL LIABILITIES AND CAPITALIZATION	$ (9,082)		$ (9,082)		$ (8,922)