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

No definition available.

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 159

-Paragraph 18

-Subparagraph f

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-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 20

-Subparagraph a (1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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-Paragraph 3

-Subparagraph (a)(1)

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- Definition

The amount of the cost of sales reported by an equity method investment of the entity.

+ References

No definition available.

+ Details

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- Definition

The amount of current assets reported by an equity method investment of the entity.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(g))

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-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

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-Subparagraph d

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

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-Publisher FASB

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-Topic 323

-SubTopic 10

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-Subparagraph (c)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 4

-Section 08

-Paragraph g

-Subparagraph 1, 2

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph w

-Article 1

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 28

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14064-108612

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- Definition

The amount of current liabilities reported by an equity method investment of the entity.

+ References

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- Definition

The amount of income (loss) from continuing operations before extraordinary items reported by an equity method investment of the entity.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph w

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 4

-Section 08

-Paragraph g

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-Paragraph 18

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-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 20

-Subparagraph d

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

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-Article 1

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- Definition

The amount of net income (loss) reported by an equity method investment of the entity.

+ References

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- Definition

The amount of noncurrent assets reported by an equity method investment of the entity.

+ References

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- Definition

The amount of noncurrent liabilities reported by an equity method investment of the entity.

+ References

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- Definition

The amount of revenue from sale of goods and services reduced by sales returns, allowances, and discounts reported by an equity method investment of the entity.

+ References

No definition available.

+ Details

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- Definition

This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

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-Paragraph 1

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-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 19

-Subparagraph c

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-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 6

-Subparagraph b

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 11

-Article 7

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 5

-Section 03

-Paragraph 9

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.12)

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Investments (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended				2 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Nov. 06, 2011	Dec. 31, 2009 CENG	Dec. 31, 2011 CENG	Dec. 31, 2010 CENG	Dec. 31, 2009 CENG	Nov. 06, 2009 CENG
Equity in earnings of investments accounted for under the equity method of accounting
Percent of membership interest in CENG sold			49.99%	49.99%					49.99%
Percentage of ownership interest in CENG			50.01%			50.01%			50.01%
Equity investment earnings	$ 19.8	$ 25.0	$ (6.1)		$ 4.3	$ (4.3)	$ 23.6	$ 4.3
Summarized balance sheet information
Current assets						415.6	507.4
Noncurrent assets						4,710.6	4,583.0
Current liabilities						273.1	630.9
Noncurrent liabilities						1,459.1	1,338.7
Summarized income statement information
Revenues						1,516.3	1,575.3	217.6
Expenses						1,248.9	1,174.5	153.0
Income from operations						267.4	400.8	64.6
Net income						$ 299.8	$ 441.6	$ 68.5