Fair Value of Financial Instruments (Details 3) (USD $) In Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Reconciliation of the beginning and ending balances for financial instruments that are recognized at fair value in the consolidated financial statements
Balance at the beginning of the period	$ 24		$ (34)		$ 20		$ 33
Total gains and losses (realized/unrealized):
Included in earnings	0		21		19		(10)
Included in OCI	(1)		(1)		0		0
Included in nuclear decommissioning obligations	(8)		5		(7)		0
Purchases	(2)		(10)		7		(1)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales			(5)				(5)
Transfer into Level 3	13	[1]	31	[1]	(17)	[1]	(16)	[1]
Transfer out of Level 3	8	[1]	(8)	[1]	12	[1]	(2)	[1]
Balance at the end of the period	34		(1)		34		(1)
The amount of the total gains for the period included in earnings attributable to the change in unrealized gains relating to assets still held at the end of the period	(1)		12		6		(24)
Debt Securities
Reconciliation of the beginning and ending balances for financial instruments that are recognized at fair value in the consolidated financial statements
Balance at the beginning of the period	9		10		8		9
Total gains and losses (realized/unrealized):
Included in earnings	0		3		0		3
Included in OCI	(1)		(1)		0		0
Included in nuclear decommissioning obligations	0		0		0		0
Purchases	0		0		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales			(5)				(5)
Transfer into Level 3	0		0		0		0
Transfer out of Level 3	0		0		0		0
Balance at the end of the period	8		7		8		7
The amount of the total gains for the period included in earnings attributable to the change in unrealized gains relating to assets still held at the end of the period	0		0		0		0
Trust Fund Investment [Member]
Reconciliation of the beginning and ending balances for financial instruments that are recognized at fair value in the consolidated financial statements
Balance at the beginning of the period	41		32		39		37
Total gains and losses (realized/unrealized):
Included in earnings	0		0		0		0
Included in OCI	0		0		0		0
Included in nuclear decommissioning obligations	(8)		5		(7)		0
Purchases	0		0		1		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales			0				0
Transfer into Level 3	0		0		0		0
Transfer out of Level 3	0		0		0		0
Balance at the end of the period	33		37		33		37
The amount of the total gains for the period included in earnings attributable to the change in unrealized gains relating to assets still held at the end of the period	0		0		0		0
Derivatives
Reconciliation of the beginning and ending balances for financial instruments that are recognized at fair value in the consolidated financial statements
Balance at the beginning of the period	(26)		(76)		(27)		(13)
Total gains and losses (realized/unrealized):
Included in earnings	0		18		19		(13)
Included in OCI	0		0		0		0
Included in nuclear decommissioning obligations	0		0		0		0
Purchases	(2)		(10)		6		(1)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales			0				0
Transfer into Level 3	13	[1]	31	[1]	(17)	[1]	(16)	[1]
Transfer out of Level 3	8	[1]	(8)	[1]	12	[1]	(2)	[1]
Balance at the end of the period	(7)	[2]	(45)	[2]	(7)	[2]	(45)	[2]
The amount of the total gains for the period included in earnings attributable to the change in unrealized gains relating to assets still held at the end of the period	$ (1)		$ 12		$ 6		$ (24)

[1] Transfers into/out of Level 3 are related to the availability of external broker quotes, and are valued as of the end of the reporting period. All transfers into/out are with Level 2.

[2] Consists of derivative assets and liabilities, net.