Derivative Instruments (Tables)

3 Months Ended

Mar. 31, 2013

Derivative Instruments [Abstract]

Schedule of Derivatives Instruments Statements of Financial Performance and Financial Position, Location [Table Text Block]

The following tables present the fair values of our net derivative instruments recorded on our Consolidated Condensed Balance Sheets by location and hedge type at March 31, 2013 and December 31, 2012 (in millions):

	March 31, 2013
	Commodity Instruments			Interest Rate Swaps			Total Derivative Instruments
Balance Sheet Presentation
Current derivative assets	$	514		$	—		$	514
Long-term derivative assets	144			5			149
Total derivative assets	$	658		$	5		$	663
Current derivative liabilities	$	551		$	44		$	595
Long-term derivative liabilities	145			144			289
Total derivative liabilities	$	696		$	188		$	884
Net derivative liabilities	$	(38	)	$	(183	)	$	(221	)

	December 31, 2012
	Commodity Instruments			Interest Rate Swaps			Total Derivative Instruments
Balance Sheet Presentation
Current derivative assets	$	339		$	—		$	339
Long-term derivative assets	94			4			98
Total derivative assets	$	433		$	4		$	437
Current derivative liabilities	$	317		$	40		$	357
Long-term derivative liabilities	133			160			293
Total derivative liabilities	$	450		$	200		$	650
Net derivative liabilities	$	(17	)	$	(196	)	$	(213	)

Schedule of Notional Amounts of Outstanding Derivative Positions

As of March 31, 2013 and December 31, 2012, the net forward notional buy (sell) position of our outstanding commodity and interest rate swap contracts that did not qualify under the normal purchase normal sale exemption were as follows (in millions):

Derivative Instruments	Notional Amounts
	March 31, 2013			December 31, 2012
Power (MWh)	(16		)	(16		)
Natural gas (MMBtu)	162			66
Interest rate swaps	$	1,599		$	1,602

Schedule of Derivative Instruments in Statement of Financial Position, Fair Value

	March 31, 2013				December 31, 2012
	Fair Value of Derivative Assets		Fair Value of Derivative Liabilities		Fair Value of Derivative Assets		Fair Value of Derivative Liabilities
Derivatives designated as cash flow hedging instruments:
Interest rate swaps	$	5	$	174	$	4	$	184
Total derivatives designated as cash flow hedging instruments	$	5	$	174	$	4	$	184
Derivatives not designated as hedging instruments:
Commodity instruments	$	658	$	696	$	433	$	450
Interest rate swaps	—		14		—		16
Total derivatives not designated as hedging instruments	$	658	$	710	$	433	$	466
Total derivatives	$	663	$	884	$	437	$	650

Derivative Instruments Subject to Master Netting Arrangements [Table Text Block]

The tables below set forth our net exposure to derivative instruments after offsetting amounts subject to a master netting arrangement with the same counterparty at March 31, 2013 and December 31, 2012 (in millions):

	March 31, 2013
				Gross Amounts Not Offset on the Consolidated Condensed Balance Sheets
	Gross Amounts Presented on our Consolidated Condensed Balance Sheets			Derivative Asset (Liability) not Offset on the Consolidated Condensed Balance Sheets			Margin/Cash (Received) Posted (1)			Net Amount
Derivative assets:
Commodity exchange traded futures and swaps contracts	$	594		$	(593	)	$	(1	)	$	—
Commodity forward contracts	64			(29		)	—			35
Interest rate swaps	5			—			—			5
Total derivative assets	$	663		$	(622	)	$	(1	)	$	40
Derivative (liabilities):
Commodity exchange traded futures and swaps contracts	$	(655	)	$	593		$	62		$	—
Commodity forward contracts	(41		)	29			1			(11		)
Interest rate swaps	(188		)	—			—			(188		)
Total derivative (liabilities)	$	(884	)	$	622		$	63		$	(199	)
Net derivative assets (liabilities)	$	(221	)	$	—		$	62		$	(159	)

	December 31, 2012
				Gross Amounts Not Offset on the Consolidated Condensed Balance Sheets
	Gross Amounts Presented on our Consolidated Condensed Balance Sheets			Derivative Asset (Liability) not Offset on the Consolidated Condensed Balance Sheets			Margin/Cash (Received) Posted (1)			Net Amount
Derivative assets:
Commodity exchange traded futures and swaps contracts	$	385		$	(379	)	$	(6	)	$	—
Commodity forward contracts	48			(17		)	(1		)	30
Interest rate swaps	4			—			—			4
Total derivative assets	$	437		$	(396	)	$	(7	)	$	34
Derivative (liabilities):
Commodity exchange traded futures and swaps contracts	$	(424	)	$	379		$	45		$	—
Commodity forward contracts	(26		)	17			1			(8		)
Interest rate swaps	(200		)	—			—			(200		)
Total derivative (liabilities)	$	(650	)	$	396		$	46		$	(208	)
Net derivative assets (liabilities)	$	(213	)	$	—		$	39		$	(174	)

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(1) Negative balances represent margin deposits posted with us by our counterparties related to our derivative activities that are subject to a master netting arrangement. Positive balances reflect margin deposits and natural gas and power prepayments posted by us with our counterparties related to our derivative activities that are subject to a master netting arrangement. See Note 6 for a further discussion of our collateral.

Realized Unrealized Gain Loss by Instrument

The following tables detail the components of our total mark-to-market activity for both the net realized gain (loss) and the net unrealized gain (loss) recognized from our derivative instruments in earnings and where these components were recorded on our Consolidated Condensed Statements of Operations for the periods indicated (in millions):

	Three Months Ended March 31,
	2013			2012
Realized gain (loss)(1)
Commodity derivative instruments	$	28		$	118
Interest rate swaps	—			(157		)
Total realized gain (loss)	$	28		$	(39	)
Unrealized gain (loss)(2)
Commodity derivative instruments	$	(57	)	$	78
Interest rate swaps	2			146
Total unrealized gain (loss)	$	(55	)	$	224
Total mark-to-market activity, net	$	(27	)	$	185

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(1) Does not include the realized value associated with derivative instruments that settle through physical delivery.

(2) In addition to changes in market value on derivatives not designated as hedges, changes in unrealized gain (loss) also includes hedge ineffectiveness and adjustments to reflect changes in credit default risk exposure.

Schedule of Other Derivatives Not Designated as Hedging Instruments, Statements of Financial Performance and Financial Position, Location

	Three Months Ended March 31,
	2013			2012
Realized and unrealized gain (loss)
Derivatives contracts included in operating revenues	$	(74	)	$	92
Derivatives contracts included in fuel and purchased energy expense	45			104
Interest rate swaps included in interest expense	2			3
Loss on interest rate derivatives	—			(14		)
Total mark-to-market activity, net	$	(27	)	$	185

Derivatives Designated as Hedges

The following table details the effect of our net derivative instruments that qualified for hedge accounting treatment and are included in OCI and AOCI for the periods indicated (in millions):

	Three Months Ended March 31,					Three Months Ended March 31,
	Gain (Loss) Recognized  in OCI (Effective Portion)					Gain (Loss) Reclassified  from AOCI into Income (Effective Portion)(3)
	2013		2012			2013			2012			Affected Line Item on the Consolidated Condensed Statements of Operations
Commodity derivative instruments(1):
Power derivative instruments	$	—	$	(15	)	$	—		$	38		Commodity revenue
Natural gas derivative instruments	—		14			—			(21		)	Commodity expense
Interest rate swaps(2)	13		1			(9		)	(7		)	Interest expense
Total	$	13	$	—		$	(9	)	$	10

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(1) There were no commodity derivative instruments designated as cash flow hedges during the three months ended March 31, 2013. We recorded a gain on hedge ineffectiveness of $2 million related to our commodity derivative instruments designated as cash flow hedges during the three months ended March 31, 2012.

(2) We did not record any gain (loss) on hedge ineffectiveness related to our interest rate swaps designated as cash flow hedges during the three months ended March 31, 2013 and 2012.

(3) Cumulative cash flow hedge losses, net of tax, remaining in AOCI were $228 million and $242 million at March 31, 2013 and December 31, 2012, respectively.