Fair Value (Tables)

12 Months Ended

Dec. 31, 2012

Fair Value Disclosures [Abstract]

Assets and liabilities measured and recorded at fair value on a recurring basis

The following table presents assets and liabilities measured and recorded at fair value on a recurring basis as of December 31, 2012 and 2011:

	December 31, 2012															December 31, 2011
	Level 1			Level 2			Level 3			Netting (a)			Net Balance			Level 1			Level 2			Level 3			Netting (a)			Net Balance
	(In millions)
Assets:
Cash equivalents (b)	$	—		$	123		$	—		$	—		$	123		$	—		$	140		$	—		$	—		$	140
Nuclear decommissioning trusts	694			343			—			—			1,037			577			360			—			—			937
Other investments (c) (d)	66			44			—			—			110			57			38			—			—			95
Derivative assets:
Foreign currency exchange contracts	—			—			—			—			—			—			3			—			(3		)	—
Commodity Contracts:
Natural Gas	555			66			24			(605		)	40			1,926			78			20			(1,991		)	33
Electricity	—			226			134			(258		)	102			—			523			224			(490		)	257
Other	6			3			2			(6		)	5			23			2			6			(25		)	6
Total derivative assets	561			295			160			(869		)	147			1,949			606			250			(2,509		)	296
Total	$	1,321		$	805		$	160		$	(869	)	$	1,417		$	2,583		$	1,144		$	250		$	(2,509	)	$	1,468
Liabilities:
Derivative liabilities:
Foreign currency exchange contracts	$	—		$	—		$	—		$	—		$	—		$	—		$	(5	)	$	—		$	3		$	(2	)
Interest rate contracts	—			(1		)	—			—			(1		)	—			(1		)	—			—			(1		)
Commodity Contracts:
Natural Gas	(526		)	(73		)	(62		)	605			(56		)	(1,940		)	(126		)	(14		)	1,976			(104		)
Electricity	—			(240		)	(111		)	258			(93		)	—			(513		)	(192		)	565			(140		)
Other	(6		)	(1		)	—			6			(1		)	(19		)	(1		)	—			20			—
Total derivative liabilities	(532		)	(315		)	(173		)	869			(151		)	(1,959		)	(646		)	(206		)	2,564			(247		)
Total	$	(532	)	$	(315	)	$	(173	)	$	869		$	(151	)	$	(1,959	)	$	(646	)	$	(206	)	$	2,564		$	(247	)
Net Assets at the end of the period	$	789		$	490		$	(13	)	$	—		$	1,266		$	624		$	498		$	44		$	55		$	1,221
Assets:
Current	$	493		$	372		$	120		$	(754	)	$	231		$	1,571		$	660		$	181		$	(2,050	)	$	362
Noncurrent (e)	828			433			40			(115		)	1,186			1,012			484			69			(459		)	1,106
Total Assets	$	1,321		$	805		$	160		$	(869	)	$	1,417		$	2,583		$	1,144		$	250		$	(2,509	)	$	1,468
Liabilities:
Current	$	(466	)	$	(269	)	$	(144	)	$	754		$	(125	)	$	(1,603	)	$	(527	)	$	(152	)	$	2,124		$	(158	)
Noncurrent	(66		)	(46		)	(29		)	115			(26		)	(356		)	(119		)	(54		)	440			(89		)
Total Liabilities	$	(532	)	$	(315	)	$	(173	)	$	869		$	(151	)	$	(1,959	)	$	(646	)	$	(206	)	$	2,564		$	(247	)
Net Assets at the end of the period	$	789		$	490		$	(13	)	$	—		$	1,266		$	624		$	498		$	44		$	55		$	1,221

Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]

The following tables present the fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis for the years ended December 31, 2012 and 2011:

	Year Ended December 31, 2012												Year Ended December 31, 2011
	Natural Gas			Electricity			Other			Total			Natural Gas			Electricity			Other			Total
	(In millions)
Net Assets as of January 1	$	6		$	32		$	6		$	44		$	1		$	54		$	4		$	59
Transfers into Level 3	1			—			—			1			—			4			—			4
Transfers out of Level 3	—			—			—			—			1			(25		)	—			(24		)
Total gains (losses):
Included in earnings	(41		)	101			—			60			7			77			3			87
Recorded in regulatory assets/liabilities	—			—			15			15			—			—			2			2
Purchases, issuances and settlements:
Purchases	—			2			—			2			—			3			—			3
Settlements	(4		)	(112		)	(19		)	(135		)	(3		)	(81		)	(3		)	(87		)
Net Assets (Liabilities) as of December 31	$	(38	)	$	23		$	2		$	(13	)	$	6		$	32		$	6		$	44
The amount of total gains (losses) included in net income attributed to the change in unrealized gains (losses) related to assets and liabilities held at December 31, 2012 and 2011and reflected in Operating revenues and Fuel, purchased power and gas in the Consolidated Statements of Operations	$	(33	)	$	91		$	—		$	58		$	8		$	65		$	2		$	75

Transfers Between Level 1 Level 2 and Level 3 [Table Text Block]

The following table shows transfers between the levels of the fair value hierarchy for the years ended December 31, 2012 and 2011:

	Year Ended December 31, 2012						Year Ended December 31, 2011
	Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
	(In millions)
Transfers into Level 1 from	N/A		$	—	$	—	N/A		$	—	$	—
Transfers into Level 2 from	$	—	N/A		—		$	—	N/A		24
Transfers into Level 3 from	—		1		N/A		—		4		N/A

Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Table Text Block]

The following table presents the unobservable inputs related to Level 3 assets and liabilities as of December 31, 2012:

	December 31, 2012
Commodity Contracts	Derivative Assets		Derivative Liabilities			Valuation Techniques	Unobservable Input	Range							Weighted Average
(In millions)
Natural Gas	$	24	$	(62	)	Discounted Cash Flow	Forward basis price (per MMBtu)	$	(0.63	)	—	$	1.95	/MMBtu	$	0.03	/MMBtu
Electricity	134		(111		)	Discounted Cash Flow	Forward basis price (per MWh)	$	(2	)	—	$	16	/MWh	$	3	/MWh

Fair Value of Financial Instruments [Table Text Block]

The following table presents the carrying amount and fair value of financial instruments as of December 31, 2012 and 2011:

	December 31, 2012								December 31, 2011
	Carrying		Fair Value						Carrying		Fair
	Amount		Level 1		Level 2		Level 3		Amount		Value
	(In millions)
Notes receivable, excluding capital leases	$	39	$	—	$	—	$	39	$	48	$	48
Dividends payable	107		107		—		—		99		99
Short-term borrowings	240		—		240		—		419		419
Long-term debt	7,813		507		7,453		933		7,682		8,757

Fair Value of Nuclear Decommissioning Trust Fund Assets Text Block [Table]

	December 31 2012		December 31 2011
	(In millions)
Fermi 2	$	1,021	$	915
Fermi 1	3		3
Low level radioactive waste	13		19
Total	$	1,037	$	937

Schedule of Realized Gain (Loss) [Table Text Block]

	Year Ended December 31
	2012			2011			2010
	(In millions)
Realized gains	$	37		$	46		$	192
Realized losses	$	(31	)	$	(38	)	$	(83	)
Proceeds from sales of securities	$	97		$	80		$	377

Fair Value and Unrealized Gains for Nuclear Decommissioning Trust Fund Table [Table] [Table Text Block]

	December 31, 2012				December 31, 2011
	Fair Value		Unrealized Gains		Fair Value		Unrealized Gains
	(In millions)
Equity securities	$	631	$	122	$	533	$	80
Debt securities	399		27		385		22
Cash and cash equivalents	7		—		19		—
	$	1,037	$	149	$	937	$	102