Commitments and Contingencies (Guarantees and Indemnities) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended
Feb. 20, 2003	Jun. 30, 2013 cases
Indemnities Under International Asset Sale Agreements
Guarantees and Indemnities
Liability under indemnities		$ 19
Midwest Generation LLC \| Environmental Indemnities under Acquisition Agreement
Guarantees and Indemnities
Percentage reimbursement obligation for asbestos claims (as a percent)	50.00%
Term of asbestos supplemental agreement (in years)	5 years
Term of asbestos supplemental agreement, automatic renewal period (in years)	1 year
Number of cases not settled and dismissed creating potential liability (in cases)		260
Liability under indemnities		$ 53

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The percentage of asbestos claims and related expenses for which the entity is responsible under the terms of the reimbursement agreement.

+ References

No definition available.

+ Details

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- Definition

The disclosure pertaining to asbestos supplemental agreement term.

+ References

No definition available.

+ Details

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- Definition

Term of Asbestos Supplemental Agreement, Renewnal Period

+ References

No definition available.

+ Details

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- Definition

The carrying amount as of the balance sheet date of the combined total of loss contingency liabilities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6952336&loc=d3e14326-108349

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 9, 10, 11, 12

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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- Definition

The total amount of pending claims pertaining to a loss contingency accrual as of the balance sheet date.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 9, 10, 11, 12

-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.

+ Details

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