Gain on U.S. Department of Energy Settlement (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended		1 Months Ended	3 Months Ended
Sep. 30, 2011	Dec. 31, 2009	Jun. 30, 2011 CENG	Sep. 30, 2011 CENG
Related Party Transactions:
Pre-tax gain on U. S. Department of Energy settlement	$ 35.5		$ 35.5
Proceeds from U.S. Department of Energy settlement				$ 35.5
Percent of membership interest in CENG sold (as a percent)		49.99%

The percentage of ownership interest in a subsidiary that was sold during the period.

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- Definition

Gain (loss) on entity's disposition of equity in securities of subsidiaries or 50 percent or less owned persons. Reflects the difference in the parent company's carrying amount of the equity interest in the subsidiary (or equity method investee) immediately before and after all stock transactions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 9

-Section 04

-Paragraph 13

-Subparagraph g

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.13(g))

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

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- Definition

Cash received for the settlement of litigation during the current period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 27

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 25

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3536-108585

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ Details

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