Financial Instruments, Derivatives, Guarantees and Concentration of Credit Risk (Details 2) (USD $) In Millions	Dec. 31, 2010	Dec. 31, 2009
Fair value of energy commodity derivatives
Designated as hedging instruments, assets	$ 288	$ 352
Designated as hedging instruments, liabilities	22	174
Not designated as hedging instruments, assets	285	742
Not designated as hedging instruments, liabilities	267	832
Total derivatives, assets	573	1,094
Total derivatives, liabilities	289	1,006
Legacy Natural Gas Contracts From Former Power Business [Member]
Fair value of energy commodity derivatives
Not designated as hedging instruments, assets	186	505
Not designated as hedging instruments, liabilities	187	526
Other Contract [Member]
Fair value of energy commodity derivatives
Not designated as hedging instruments, assets	99	237
Not designated as hedging instruments, liabilities	$ 80	$ 306

Fair value of a derivative asset (or nonderivative instrument) that is designated and qualifies as a hedging instrument, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 205G

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 44C
-Subparagraph a
-Clause 1

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Fair value of energy commodity derivatives.

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