Guarantees Of Debt (Schedule Of Financial Statements Of Guarantors) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Debt Instrument [Line Items]
Operating Revenues	$ 1,905	$ 2,314	$ 4,521	$ 5,449
Operating Expenses	1,558	1,746	3,347	3,833
Operating Income (Loss)	347	568	1,174	1,616
Equity Earnings (Losses) of Subsidiaries	4	4	6	7
Other Income	44	76	92	124
Other Deductions	(10)	(10)	(31)	(22)
Other-Than-Temporary Impairments	(10)	(10)	(20)	(15)
Interest Expense	(97)	(97)	(189)	(195)
Income Tax Expense	(91)	(186)	(374)	(584)
Net Income	187	345	658	931
Net Cash Provided By (Used In) Operating Activities			1,722	2,234
Net Cash Provided By (Used In) Investing Activities			(2,004)	(1,773)
Net Cash Provided By (Used In) Financing Activities			536	(266)
Current Assets	3,489		3,489		$ 3,494
Property, Plant and Equipment, net	28,014		28,014		26,539
Noncurrent Assets	7,542		7,542		7,502
Total Assets	39,045		39,045		37,535
Current Liabilities	3,120		3,120		3,575
Noncurrent Liabilities	12,333		12,333		12,059
Long-Term Debt	10,273		10,273		8,834
Member's Equity	13,319		13,319		13,067
TOTAL LIABILITIES AND CAPITALIZATION	39,045		39,045		37,535
Power Senior Notes [Member]
Debt Instrument [Line Items]
Operating Revenues	714	1,025	2,027	2,750
Operating Expenses	726	797	1,696	1,938
Operating Income (Loss)	(12)	228	331	812
Equity Earnings (Losses) of Subsidiaries	4	5	6	8
Other Income	25	55	51	84
Other Deductions	(9)	(7)	(27)	(18)
Other-Than-Temporary Impairments	(10)	(10)	(20)	(15)
Interest Expense	(20)	(33)	(42)	(64)
Income Tax Expense	11	(72)	(118)	(306)
Net Income	(11)	166	181	501
Comprehensive Income (Loss)	5	159	220	506
Net Cash Provided By (Used In) Operating Activities			917	1,292
Net Cash Provided By (Used In) Investing Activities			(1,607)	(887)
Net Cash Provided By (Used In) Financing Activities			694	(402)
Current Assets	2,548		2,548		1,949
Property, Plant and Equipment, net	8,478		8,478		8,127
Investment in Subsidiaries	0		0		0
Noncurrent Assets	2,252		2,252		2,174
Total Assets	13,278		13,278		12,250
Current Liabilities	1,263		1,263		1,226
Noncurrent Liabilities	3,413		3,413		3,338
Long-Term Debt	2,380		2,380		1,684
Member's Equity	6,222		6,222		6,002
TOTAL LIABILITIES AND CAPITALIZATION	13,278		13,278		12,250
Power Senior Notes [Member] | Consolidating Adjustments [Member]
Debt Instrument [Line Items]
Operating Revenues	(32)	(26)	(63)	(84)
Operating Expenses	(32)	(26)	(63)	(84)
Operating Income (Loss)	0	0	0	0
Equity Earnings (Losses) of Subsidiaries	0	(185)	(204)	(533)
Other Income	(22)	(12)	(45)	(24)
Other Deductions	0	0	0	0
Other-Than-Temporary Impairments	0	0	0	0
Interest Expense	22	12	45	24
Income Tax Expense	0	0	0	0
Net Income	0	(185)	(204)	(533)
Comprehensive Income (Loss)	(9)	(171)	(229)	(524)
Net Cash Provided By (Used In) Operating Activities			(356)	(687)
Net Cash Provided By (Used In) Investing Activities			579	766
Net Cash Provided By (Used In) Financing Activities			(223)	(79)
Current Assets	(4,828)		(4,828)		(4,828)
Property, Plant and Equipment, net	0		0		0
Investment in Subsidiaries	(4,764)		(4,764)		(4,847)
Noncurrent Assets	(51)		(51)		(76)
Total Assets	(9,643)		(9,643)		(9,751)
Current Liabilities	(4,828)		(4,828)		(4,828)
Noncurrent Liabilities	(51)		(51)		(76)
Long-Term Debt	0		0		0
Member's Equity	(4,764)		(4,764)		(4,847)
TOTAL LIABILITIES AND CAPITALIZATION	(9,643)		(9,643)		(9,751)
Power Senior Notes [Member] | Power Parent [Member]
Debt Instrument [Line Items]
Operating Revenues	0	0	0	0
Operating Expenses	2	(1)	12	4
Operating Income (Loss)	(2)	1	(12)	(4)
Equity Earnings (Losses) of Subsidiaries	(1)	186	204	535
Other Income	17	12	34	23
Other Deductions	0	(1)	0	(1)
Other-Than-Temporary Impairments	0	0	0	0
Interest Expense	(31)	(33)	(61)	(62)
Income Tax Expense	6	1	16	10
Net Income	(11)	166	181	501
Comprehensive Income (Loss)	5	159	220	506
Net Cash Provided By (Used In) Operating Activities			337	410
Net Cash Provided By (Used In) Investing Activities			(1,287)	(480)
Net Cash Provided By (Used In) Financing Activities			951	70
Current Assets	5,490		5,490		4,501
Property, Plant and Equipment, net	58		58		83
Investment in Subsidiaries	4,419		4,419		4,501
Noncurrent Assets	134		134		155
Total Assets	10,101		10,101		9,240
Current Liabilities	1,079		1,079		1,112
Noncurrent Liabilities	420		420		442
Long-Term Debt	2,380		2,380		1,684
Member's Equity	6,222		6,222		6,002
TOTAL LIABILITIES AND CAPITALIZATION	10,101		10,101		9,240
Power Senior Notes [Member] | Guarantor Subsidiaries [Member]
Debt Instrument [Line Items]
Operating Revenues	700	1,012	2,002	2,727
Operating Expenses	716	787	1,668	1,918
Operating Income (Loss)	(16)	225	334	809
Equity Earnings (Losses) of Subsidiaries	1	(1)	0	(2)
Other Income	30	55	62	85
Other Deductions	(9)	(6)	(27)	(17)
Other-Than-Temporary Impairments	(10)	(10)	(20)	(15)
Interest Expense	(7)	(7)	(17)	(16)
Income Tax Expense	3	(73)	(137)	(315)
Net Income	(8)	183	195	529
Comprehensive Income (Loss)	1	169	220	520
Net Cash Provided By (Used In) Operating Activities			777	1,508
Net Cash Provided By (Used In) Investing Activities			(504)	(963)
Net Cash Provided By (Used In) Financing Activities			(273)	(543)
Current Assets	1,655		1,655		1,912
Property, Plant and Equipment, net	6,476		6,476		6,502
Investment in Subsidiaries	345		345		346
Noncurrent Assets	2,041		2,041		1,959
Total Assets	10,517		10,517		10,719
Current Liabilities	3,719		3,719		3,866
Noncurrent Liabilities	2,652		2,652		2,597
Long-Term Debt	0		0		0
Member's Equity	4,146		4,146		4,256
TOTAL LIABILITIES AND CAPITALIZATION	10,517		10,517		10,719
Power Senior Notes [Member] | Non-Guarantor Subsidiaries [Member]
Debt Instrument [Line Items]
Operating Revenues	46	39	88	107
Operating Expenses	40	37	79	100
Operating Income (Loss)	6	2	9	7
Equity Earnings (Losses) of Subsidiaries	4	5	6	8
Other Income	0	0	0	0
Other Deductions	0	0	0	0
Other-Than-Temporary Impairments	0	0	0	0
Interest Expense	(4)	(5)	(9)	(10)
Income Tax Expense	2	0	3	(1)
Net Income	8	2	9	4
Comprehensive Income (Loss)	8	$ 2	9	4
Net Cash Provided By (Used In) Operating Activities			159	61
Net Cash Provided By (Used In) Investing Activities			(395)	(210)
Net Cash Provided By (Used In) Financing Activities			239	$ 150
Current Assets	231		231		364
Property, Plant and Equipment, net	1,944		1,944		1,542
Investment in Subsidiaries	0		0		0
Noncurrent Assets	128		128		136
Total Assets	2,303		2,303		2,042
Current Liabilities	1,293		1,293		1,076
Noncurrent Liabilities	392		392		375
Long-Term Debt	0		0		0
Member's Equity	618		618		591
TOTAL LIABILITIES AND CAPITALIZATION	$ 2,303		$ 2,303		$ 2,042