Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2012

Fair Value Measurements [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

The following table presents the Company's assets and liabilities recognized on the Consolidated Balance Sheets and measured at fair value on a recurring basis (in millions):

	Input Levels for Fair Value Measurements
	Level 1			Level 2			Level 3			Other(1)			Total
As of June 30, 2012
Assets:
Commodity derivatives	$	1		$	126		$	28		$	(116	)	$	39
Money market mutual funds(2)	1,045			—			—			—			1,045
Debt securities:
United States government obligations	95			—			—			—			95
International government obligations	—			1			—			—			1
Corporate obligations	—			30			—			—			30
Municipal obligations	—			8			—			—			8
Agency, asset and mortgage-backed obligations	—			7			—			—			7
Auction rate securities	—			—			36			—			36
Equity securities:
United States companies	180			—			—			—			180
International companies	426			—			—			—			426
Investment funds	67			—			—			—			67
	$	1,814		$	172		$	64		$	(116	)	$	1,934
Liabilities - commodity derivatives	$	(22	)	$	(528	)	$	(11	)	$	249		$	(312	)

	Input Levels for Fair Value Measurements
	Level 1			Level 2			Level 3			Other(1)			Total
As of December 31, 2011
Assets:
Commodity derivatives	$	1		$	166		$	27		$	(147	)	$	47
Money market mutual funds(2)	164			—			—			—			164
Debt securities:
United States government obligations	89			—			—			—			89
International government obligations	—			1			—			—			1
Corporate obligations	—			30			—			—			30
Municipal obligations	—			12			—			—			12
Agency, asset and mortgage-backed obligations	—			7			—			—			7
Auction rate securities	—			—			35			—			35
Equity securities:
United States companies	166			—			—			—			166
International companies	489			—			—			—			489
Investment funds	64			—			—			—			64
	$	973		$	216		$	62		$	(147	)	$	1,104
Liabilities - commodity derivatives	$	(37	)	$	(598	)	$	(4	)	$	303		$	(336	)

(1) Represents netting under master netting arrangements and a net cash collateral receivable of $133 million and $156 million as of June 30, 2012 and December 31, 2011, respectively.

(2) Amounts are included in cash and cash equivalents; current investments and restricted cash and investments; and noncurrent investments and restricted cash and investments on the Consolidated Balance Sheets. The fair value of these money market mutual funds approximates cost.

Fair Value Assets and Liabilities Net Measured On Recurring Basis Unobservable Input Reconciliation [Table Text Block]

The following table reconciles the beginning and ending balances of the Company's assets and liabilities measured at fair value on a recurring basis using significant Level 3 inputs (in millions):

	Three-Month Periods					Six-Month Periods
	Ended June 30,					Ended June 30,
				Auction					Auction
	Commodity			Rate		Commodity			Rate
	Derivatives			Securities		Derivatives			Securities
2012
Beginning balance	$	25		$	36	$	23		$	35
Changes included in earnings(1)	(1		)	—		9			—
Changes in fair value recognized in other comprehensive income	6			—		3			2
Changes in fair value recognized in net regulatory assets	(6		)	—		3			—
Sales	—			—		—			(1		)
Settlements	(7		)	—		(21		)	—
Ending balance	$	17		$	36	$	17		$	36

2011
Beginning balance	$	(341	)	$	39		$	(331	)	$	50
Changes included in earnings(1)	2			—			4			—
Changes in fair value recognized in other comprehensive income	—			—			—			2
Changes in fair value recognized in net regulatory assets	96			—			83			—
Sales	—			(2		)	—			(15		)
Settlements	10			—			11			—
Ending balance	$	(233	)	$	37		$	(233	)	$	37

(1) Changes included in earnings are reported as operating revenue on the Consolidated Statements of Operations. For commodity derivatives held as of June 30, 2012 and 2011, net unrealized (losses) gains included in earnings for the three-month periods endedJune 30, 2012 and 2011 totaled $(2) million and $2 million, respectively, and for the six-month periods endedJune 30, 2012 and 2011, totaled $5 million and $1 million, respectively.

Fair Value, by Balance Sheet Grouping [Table Text Block]

The Company's long-term debt is carried at cost on the Consolidated Financial Statements. The fair value of the Company's long-term debt is a Level 2 fair value measurement and has been estimated based upon quoted market prices, where available, or at the present value of future cash flows discounted at rates consistent with comparable maturities with similar credit risks. The carrying value of the Company's variable-rate long-term debt approximates fair value because of the frequent repricing of these instruments at market rates. The following table presents the carrying value and estimated fair value of the Company's long-term debt (in millions):

	As of June 30, 2012				As of December 31, 2011
	Carrying		Fair		Carrying		Fair
	Value		Value		Value		Value
Long-term debt	$	20,345	$	24,189	$	19,072	$	23,327