Supplemental Guarantor Condensed Financial Information (Condensed Consolidating Balance Sheets) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 1,262	$ 1,175	$ 309	$ 120
Advances to affiliates	0	0
Accounts receivable	796	710
Notes receivable from parent	0	698
Income taxes receivable	7	0
Accounts receivable from affiliates	0	0
Inventories	400	393
Commodity and other derivative contractual assets	973	1,463
Accumulated deferred income taxes	0	0
Margin deposits related to commodity positions	21	71
Other current assets	34	120
Total current assets	3,493	4,630
Restricted cash	947	947
Investments	787	710
Property, plant and equipment	17,961	18,556
Advances to affiliates	0	0
Goodwill	4,952	4,952
Identifiable intangible assets – net	1,736	1,781
Commodity and other derivative contractual assets	159	586
Accumulated deferred income taxes	0	0
Other noncurrent assets, principally unamortized amendment/issuance costs	859	811
Total assets	30,894	32,973
Current liabilities:
Short-term borrowings	2,226	2,136
Notes/advances from affiliates	0	0
Long-term debt due currently	32	96
Trade accounts payable	354	389
Trade accounts and other payables to affiliates	205	139
Notes payable to parent/affiliate	92	81
Commodity and other derivative contractual liabilities	594	894
Margin deposits related to commodity positions	353	600
Accumulated deferred income taxes	36	49
Accrued income taxes payable to parent	0	31
Accrued taxes other than income	95	17
Accrued interest	532	407
Other current liabilities	219	255
Total current liabilities	4,738	5,094
Accumulated deferred income taxes	3,347	3,759
Commodity and other derivative contractual liabilities	782	1,556
Notes or other liabilities due affiliates	2	5
Long-term debt held by affiliates	382	382
Long-term debt, less amounts due currently	29,770	29,928
Affiliate tax sharing liability	723	0
Other noncurrent liabilities and deferred credits	1,793	2,643
Total liabilities	41,537	43,367
EFCH shareholder's equity	0	(10,506)
EFCH membership interests	(10,748)	0
Noncontrolling interests in subsidiaries	105	112
Total membership interests/equity	(10,643)	(10,394)	(8,965)	(7,716)
Total liabilities and membership interests/equity	30,894	32,973
Parent/ Guarantor [Member]
Current assets:
Cash and cash equivalents	0	0	0	0
Advances to affiliates	0	0
Accounts receivable	0	0
Notes receivable from parent		0
Income taxes receivable	7	0
Accounts receivable from affiliates	0	0
Inventories	0	0
Commodity and other derivative contractual assets	0	0
Accumulated deferred income taxes	3	3
Margin deposits related to commodity positions	0	0
Other current assets	0	0
Total current assets	10	3
Restricted cash	0	0
Investments	(10,467)	(9,794)
Property, plant and equipment	0	0
Advances to affiliates	0	0
Goodwill	0	0
Identifiable intangible assets – net	0	0
Commodity and other derivative contractual assets	0	0
Accumulated deferred income taxes	0	0
Other noncurrent assets, principally unamortized amendment/issuance costs	0	4
Total assets	(10,457)	(9,787)
Current liabilities:
Short-term borrowings	0	0
Notes/advances from affiliates	1	0
Long-term debt due currently	11	11
Trade accounts payable	0	0
Trade accounts and other payables to affiliates	0	0
Notes payable to parent/affiliate	92	80
Commodity and other derivative contractual liabilities	0	0
Margin deposits related to commodity positions	0	0
Accumulated deferred income taxes	0	0
Accrued income taxes payable to parent	0	2
Accrued taxes other than income	0	0
Accrued interest	3	18
Other current liabilities	0	1
Total current liabilities	107	112
Accumulated deferred income taxes	84	79
Commodity and other derivative contractual liabilities	0	0
Notes or other liabilities due affiliates	0	0
Long-term debt held by affiliates	0	0
Long-term debt, less amounts due currently	92	515
Affiliate tax sharing liability	0
Other noncurrent liabilities and deferred credits	8	13
Total liabilities	291	719
EFCH shareholder's equity		(10,506)
EFCH membership interests	(10,748)
Noncontrolling interests in subsidiaries	0	0
Total membership interests/equity	(10,748)	(10,506)
Total liabilities and membership interests/equity	(10,457)	(9,787)
Issuer [Member]
Current assets:
Cash and cash equivalents	1,200	1,115	260	87
Advances to affiliates	0	0
Accounts receivable	1	2
Notes receivable from parent		698
Income taxes receivable	0	0
Accounts receivable from affiliates	13	95
Inventories	0	0
Commodity and other derivative contractual assets	726	1,127
Accumulated deferred income taxes	0	0
Margin deposits related to commodity positions	0	0
Other current assets	2	0
Total current assets	1,942	3,037
Restricted cash	947	947
Investments	23,885	23,382
Property, plant and equipment	0	0
Advances to affiliates	0	0
Goodwill	4,952	4,952
Identifiable intangible assets – net	0	0
Commodity and other derivative contractual assets	147	575
Accumulated deferred income taxes	490	828
Other noncurrent assets, principally unamortized amendment/issuance costs	834	781
Total assets	33,197	34,502
Current liabilities:
Short-term borrowings	2,054	2,054
Notes/advances from affiliates	10,045	8,830
Long-term debt due currently	0	64
Trade accounts payable	5	2
Trade accounts and other payables to affiliates	0	0
Notes payable to parent/affiliate	0	0
Commodity and other derivative contractual liabilities	413	610
Margin deposits related to commodity positions	335	596
Accumulated deferred income taxes	3	3
Accrued income taxes payable to parent	70	433
Accrued taxes other than income	0	0
Accrued interest	528	389
Other current liabilities	0	4
Total current liabilities	13,453	12,985
Accumulated deferred income taxes	0	0
Commodity and other derivative contractual liabilities	779	1,539
Notes or other liabilities due affiliates	0	0
Long-term debt held by affiliates	382	382
Long-term debt, less amounts due currently	29,604	29,355
Affiliate tax sharing liability	(571)
Other noncurrent liabilities and deferred credits	17	36
Total liabilities	43,664	44,297
EFCH shareholder's equity		(9,795)
EFCH membership interests	(10,467)
Noncontrolling interests in subsidiaries	0	0
Total membership interests/equity	(10,467)	(9,795)
Total liabilities and membership interests/equity	33,197	34,502
Other Guarantors [Member]
Current assets:
Cash and cash equivalents	23	15	38	23
Advances to affiliates	74	36
Accounts receivable	315	360
Notes receivable from parent		0
Income taxes receivable	84	410
Accounts receivable from affiliates	0	0
Inventories	400	393
Commodity and other derivative contractual assets	247	336
Accumulated deferred income taxes	0	0
Margin deposits related to commodity positions	21	71
Other current assets	32	112
Total current assets	1,196	1,733
Restricted cash	0	0
Investments	867	747
Property, plant and equipment	17,760	18,422
Advances to affiliates	9,972	8,794
Goodwill	0	0
Identifiable intangible assets – net	1,736	1,781
Commodity and other derivative contractual assets	12	11
Accumulated deferred income taxes	0	0
Other noncurrent assets, principally unamortized amendment/issuance costs	849	806
Total assets	32,392	32,294
Current liabilities:
Short-term borrowings	2,054	2,054
Notes/advances from affiliates	0	0
Long-term debt due currently	10	21
Trade accounts payable	348	387
Trade accounts and other payables to affiliates	223	231
Notes payable to parent/affiliate	0	1
Commodity and other derivative contractual liabilities	181	284
Margin deposits related to commodity positions	18	4
Accumulated deferred income taxes	39	52
Accrued income taxes payable to parent	0	0
Accrued taxes other than income	95	17
Accrued interest	401	281
Other current liabilities	219	253
Total current liabilities	3,588	3,585
Accumulated deferred income taxes	2,782	3,569
Commodity and other derivative contractual liabilities	3	17
Notes or other liabilities due affiliates	2	5
Long-term debt held by affiliates	0	0
Long-term debt, less amounts due currently	28,704	28,486
Affiliate tax sharing liability	1,294
Other noncurrent liabilities and deferred credits	1,774	2,594
Total liabilities	38,147	38,256
EFCH shareholder's equity		(5,962)
EFCH membership interests	(5,755)
Noncontrolling interests in subsidiaries	0	0
Total membership interests/equity	(5,755)	(5,962)
Total liabilities and membership interests/equity	32,392	32,294
Non-guarantors [Member]
Current assets:
Cash and cash equivalents	39	45	11	10
Advances to affiliates	0	0
Accounts receivable	574	445
Notes receivable from parent		0
Income taxes receivable	0	0
Accounts receivable from affiliates	5	0
Inventories	0	0
Commodity and other derivative contractual assets	0	0
Accumulated deferred income taxes	3	3
Margin deposits related to commodity positions	0	0
Other current assets	0	8
Total current assets	621	501
Restricted cash	0	0
Investments	9	9
Property, plant and equipment	201	134
Advances to affiliates	0	0
Goodwill	0	0
Identifiable intangible assets – net	5	0
Commodity and other derivative contractual assets	0	0
Accumulated deferred income taxes	3	3
Other noncurrent assets, principally unamortized amendment/issuance costs	7	3
Total assets	846	650
Current liabilities:
Short-term borrowings	172	82
Notes/advances from affiliates	0	0
Long-term debt due currently	11	0
Trade accounts payable	95	97
Trade accounts and other payables to affiliates	0	3
Notes payable to parent/affiliate	0	0
Commodity and other derivative contractual liabilities	0	0
Margin deposits related to commodity positions	0	0
Accumulated deferred income taxes	0	0
Accrued income taxes payable to parent	14	6
Accrued taxes other than income	0	0
Accrued interest	1	0
Other current liabilities	0	0
Total current liabilities	293	188
Accumulated deferred income taxes	0	0
Commodity and other derivative contractual liabilities	0	0
Notes or other liabilities due affiliates	0	0
Long-term debt held by affiliates	0	0
Long-term debt, less amounts due currently	22	0
Affiliate tax sharing liability	0
Other noncurrent liabilities and deferred credits	0	0
Total liabilities	315	188
EFCH shareholder's equity		350
EFCH membership interests	426
Noncontrolling interests in subsidiaries	105	112
Total membership interests/equity	531	462
Total liabilities and membership interests/equity	846	650
Eliminations [Member]
Current assets:
Cash and cash equivalents	0	0	0	0
Advances to affiliates	(74)	(36)
Accounts receivable	(94)	(97)
Notes receivable from parent		0
Income taxes receivable	(84)	(410)
Accounts receivable from affiliates	(18)	(95)
Inventories	0	0
Commodity and other derivative contractual assets	0	0
Accumulated deferred income taxes	(6)	(6)
Margin deposits related to commodity positions	0	0
Other current assets	0	0
Total current assets	(276)	(644)
Restricted cash	0	0
Investments	(13,507)	(13,634)
Property, plant and equipment	0	0
Advances to affiliates	(9,972)	(8,794)
Goodwill	0	0
Identifiable intangible assets – net	(5)	0
Commodity and other derivative contractual assets	0	0
Accumulated deferred income taxes	(493)	(831)
Other noncurrent assets, principally unamortized amendment/issuance costs	(831)	(783)
Total assets	(25,084)	(24,686)
Current liabilities:
Short-term borrowings	(2,054)	(2,054)
Notes/advances from affiliates	(10,046)	(8,830)
Long-term debt due currently	0	0
Trade accounts payable	(94)	(97)
Trade accounts and other payables to affiliates	(18)	(95)
Notes payable to parent/affiliate	0	0
Commodity and other derivative contractual liabilities	0	0
Margin deposits related to commodity positions	0	0
Accumulated deferred income taxes	(6)	(6)
Accrued income taxes payable to parent	(84)	(410)
Accrued taxes other than income	0	0
Accrued interest	(401)	(281)
Other current liabilities	0	(3)
Total current liabilities	(12,703)	(11,776)
Accumulated deferred income taxes	481	111
Commodity and other derivative contractual liabilities	0	0
Notes or other liabilities due affiliates	0	0
Long-term debt held by affiliates	0	0
Long-term debt, less amounts due currently	(28,652)	(28,428)
Affiliate tax sharing liability	0
Other noncurrent liabilities and deferred credits	(6)	0
Total liabilities	(40,880)	(40,093)
EFCH shareholder's equity		15,407
EFCH membership interests	15,796
Noncontrolling interests in subsidiaries	0	0
Total membership interests/equity	15,796	15,407
Total liabilities and membership interests/equity	$ (25,084)	$ (24,686)