Securitized regulatory assets, noncurrent. The net book balance of the Fermi 2 nuclear plan was written off in 1998 and an equivalent regulatory asset was established. In 2001 the Fermi 2 regulatory asset and certain other regulatory assets were securitized pursuant to PA 142 and an MPSC order. A non bypassable securitization bond surcharge recovers the securitized regulatory asset over a fourteen year period ending in 2015.

No definition available.

Organization and Basis of Presentation (Consolidated Variable Interest Entities) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
ASSETS
Cash and cash equivalents	$ 99	$ 48	$ 98	$ 52
Restricted cash	24	120
Accounts receivable	1,534us-gaap_AccountsReceivableNetCurrent	1,504us-gaap_AccountsReceivableNetCurrent
Property, plant and equipment, net	17,235us-gaap_PropertyPlantAndEquipmentNet	16,820us-gaap_PropertyPlantAndEquipmentNet
Securitized regulatory assets	0	34
Total Assets	28,068us-gaap_Assets	27,974us-gaap_Assets
Liabilities [Abstract]
Current portion long-term debt, including capital leases	166	274
Current regulatory liabilities	79us-gaap_RegulatoryLiabilityCurrent	153us-gaap_RegulatoryLiabilityCurrent
Mortgage bonds, notes and other	8,348us-gaap_LongTermDebtNoncurrent	7,860us-gaap_LongTermDebtNoncurrent
Capital lease obligations	10	3
Variable Interest Entity, Primary Beneficiary [Member]
ASSETS
Cash and cash equivalents	12	7
Restricted cash	9	104
Accounts receivable	12	41
Inventories	34	67
Property, plant and equipment, net	77	81
Securitized regulatory assets	0	34
Other current and long-term assets	6	7
Total Assets	150	341
Liabilities [Abstract]
Accounts payable and accrued current liabilities	11	11
Current portion long-term debt, including capital leases	8	115
Current regulatory liabilities	0	32
Mortgage bonds, notes and other	14	15
Capital lease obligations	1	3
Other current and long-term liabilities	6	15
Total Liabilities	40	191
Variable Interest Entity, Primary Beneficiary Securitization [Member]
ASSETS
Cash and cash equivalents		0
Restricted cash		96
Accounts receivable		26
Inventories		0
Property, plant and equipment, net		0
Securitized regulatory assets		34
Other current and long-term assets		1
Total Assets		157
Liabilities [Abstract]
Accounts payable and accrued current liabilities		3
Current portion long-term debt, including capital leases		105
Current regulatory liabilities		32
Mortgage bonds, notes and other		0
Capital lease obligations		0
Other current and long-term liabilities		9
Total Liabilities		149
Variable Interest Entity, Primary Beneficiary Other [Member]
ASSETS
Cash and cash equivalents		7
Restricted cash		8
Accounts receivable		15
Inventories		67
Property, plant and equipment, net		81
Securitized regulatory assets		0
Other current and long-term assets		6
Total Assets		184
Liabilities [Abstract]
Accounts payable and accrued current liabilities		8
Current portion long-term debt, including capital leases		10
Current regulatory liabilities		0
Mortgage bonds, notes and other		15
Capital lease obligations		3
Other current and long-term liabilities		6
Total Liabilities		$ 42