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Related Party Transactions - Service Agreement and Transition Services Agreement with GenOn (Details) - USD ($) $ in Millions |  | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Jun. 12, 2017 | Dec. 31, 2017 | Mar. 31, 2018 | Mar. 31, 2017 | Dec. 31, 2017
Related Party Transaction [Line Items] |  |  |  |  |
Notice of termination, period |  | 60 days |  |  |
Other income - affiliate |  |  | $ 0 | $ 48 |
Services Agreement | Restructuring Support Agreement |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |
Shared services, annualized rate |  | $ 84 |  |  | $ 84
Credit applied |  |  |  |  | 28
GenOn | Services Agreement |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |
Service fees |  |  | 193 |  |
Shared services, annualized rate |  | $ 84 |  |  | $ 84
Credit applied | $ 28 |  |  |  |
GenOn | Transition Services Agreement | Restructuring Support Agreement |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |
Selling, general and administrative expenses |  |  | $ 21 |  |

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- Definition Restructuring and Related Cost, Annualized Services + References No definition available. + Details
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- Definition Restructuring and Related Cost, Credit Applied + References No definition available. + Details
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- Definition Service Agreement, Notice Of Termination, Period + References No definition available. + Details
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- Definition Revenue, comprised of base and incentive revenue derived from the management of joint ventures, managing third-party properties, or another entity's operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1(d)) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 + Details
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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. + References No definition available. + Details
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- Definition Reflects the sum of all other revenue and income realized from sales and other transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party during the period. + References No definition available. + Details
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Balance Type: | credit
Period Type: | duration

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- Definition Amount of selling, general and administrative expenses resulting from transactions, excluding transactions that are eliminated in consolidated or combined financial statements, with related party. + References No definition available. + Details
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- Details
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- Details
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- Details
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- Details
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Period Type: |