Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2011

Fair Value Measurements

Fair value of assets and liabilities that are measured at fair value on a recurring basis

	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)			Significant Unobservable Inputs (a) (Level 3)			Other			Balance at September 30, 2011
Assets
Cash Equivalents	$	401	$	—		$	—		$	—		$	401
Risk management activities-derivative instruments:
Commodity contracts	—		59			54			(53		)(b)	60
Nuclear decommissioning trust:
U.S. commingled equity funds	—		154			—			—			154
Fixed income securities:
U.S. Treasury	80		—			—			—			80
Cash and cash equivalent funds	—		12			—			2		(c)	14
Corporate debt	—		64			—			—			64
Mortgage-backed securities	—		76			—			—			76
Municipality bonds	—		81			—			—			81
Other	—		20			—			—			20
Subtotal nuclear decommissioning trust	80		407			—			2			489
Total	$	481	$	466		$	54		$	(51	)	$	950
Liabilities
Risk management activities - derivative instruments:
Commodity contracts	$	—	$	(189	)	$	(92	)	$	162	(b)	$	(119	)

(a) Primarily consists of heat rate options and long-dated electricity contracts.

(b) Represents counterparty netting, margin and collateral (see Note 8).

(c) Represents nuclear decommissioning trust net pending securities sales and purchases.

	Quoted Prices in Active Markets for Identical Assets (Level 1)			Significant Other Observable Inputs (Level 2)			Significant Unobservable Inputs (a) (Level 3)			Other			Balance at December 31, 2010
Assets
Cash equivalents	$	35		$	—		$	—		$	—		$	35
Risk management activities-derivative instruments:
Commodity contracts	—			80			61			(28		)(b)	113
Nuclear decommissioning trust:
U.S. commingled equity funds	—			168			—			—			168
Fixed income securities:
U.S. Treasury	50			—			—			—			50
Cash and cash equivalent funds	—			22			—			—			22
Corporate debt	—			60			—			—			60
Mortgage-backed securities	—			81			—			—			81
Municipality bonds	—			79			—			—			79
Other	—			20			—			(10		)(c)	10
Subtotal nuclear decommissioning trust	50			430			—			(10		)	470
Total	$	85		$	510		$	61		$	(38	)	$	618
Liabilities
Risk management activities — derivative instruments:
Commodity contracts	$	(1	)	$	(280	)	$	(99	)	$	256	(b)	$	(124	)

(a) Primarily consists of heat rate options and long-dated electricity contracts.

(b) Represents counterparty netting, margin and collateral (see Note 8).

(c) Represents nuclear decommissioning trust net pending securities sales and purchases.

Changes in fair value for assets and liabilities that are measured at fair value on a recurring basis using Level 3 inputs

	Three Months Ended September 30,						Nine Months Ended September 30,
Commodity Contracts	2011			2010			2011			2010
Net derivative balance at beginning of period	$	(47	)	$	(42	)	$	(38	)	$	(10	)
Total net gains (losses) realized/unrealized:
Included in earnings	1			1			2			(1		)
Included in other comprehensive income (“OCI”)	2			(11		)	1			(20		)
Deferred as a regulatory asset or liability	2			(15		)	(4		)	(39		)
Settlements	6			12			10			15
Transfers into Level 3 from Level 2	—			(2		)	(4		)	6
Transfers from Level 3 into Level 2	(2		)	8			(5		)	—
Net derivative balance at end of period	$	(38	)	$	(49	)	$	(38	)	$	(49	)
Net unrealized gains included in earnings related to instruments still held at end of period	$	—		$	1		$	1		$	—