Base Residual Auction Results Adjustments

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- Definition

Discontinued Operation, Continuing Cash Flows after Disposal, Number of Annual Installments

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- Definition

Emission credit allowances

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Future Revenue Rights

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The generation capacity of the entity's power generation facilities as of the balance sheet date, expressed in megawatts.

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Amount of direct costs of the business combination including legal, accounting, and other costs incurred to consummate the business acquisition.

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- Definition

Amount of cash inflow (outflow) from (to) the discontinued operation after the disposal transaction.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 4B
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Amount of currency on hand, demand deposits with banks or financial institutions, and other kinds of accounts that have the general characteristics of demand deposits, held by a disposal group.

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- Definition

The designation of funds furnished by a borrower to a lender to assure future payments of the borrower's real estate taxes and insurance obligations with respect to a mortgaged property. Escrow deposits may be made for a variety of other purposes such as earnest money and contingent payments. This element excludes replacement reserves which are an escrow separately provided for within the US GAAP taxonomy.

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- Definition

Amount of gain (loss) on sale or disposal of intangible assets.

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Amount of gain (loss) on sale or disposal of property, plant and equipment assets, including oil and gas property and timber property.

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Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

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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.

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The minimum amount the entity agreed to spend under the long-term purchase commitment.

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The cash inflow from disposal of asset without physical form usually arising from contractual or other legal rights, excluding goodwill.

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The cash inflow from the sale of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale.

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Dispositions (GenOn and GenOn Americas Generation) (Details) allowance in Millions, $ in Millions								3 Months Ended			9 Months Ended
	Sep. 26, 2016 USD ($)	Jul. 12, 2016 USD ($)	May 12, 2016 USD ($) MW	Mar. 01, 2016 USD ($)	Feb. 02, 2016 USD ($) installment	Nov. 24, 2015 USD ($) MW	Nov. 09, 2015 USD ($) MW	Mar. 31, 2017 USD ($) allowance	Sep. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Sep. 30, 2017 USD ($) MW	Sep. 30, 2016 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of emission allowances											$ 0.0	$ 36.0
Proceeds from disposition											$ 0.0	563.0
Generation capacity (in MW) \| MW											15,395
Potrero LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from disposition	$ 86.0
Closing costs	8.0
Escrow	4.0
Potrero LLC \| Cash
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from disposition	$ 74.0
Aurora Generating Station
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from disposition		$ 369.0	$ 365.0
Gain on disposition									$ 188.0
Generation capacity (in MW) \| MW			878
Adjustments primarily for base residual auction results and estimated working capital		$ 4.0
Aurora Generating Station \| RA Generation
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cap on guaranty payment			$ 365.0
Aurora Generating Station \| RA Generation \| 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cap on guaranty payment											$ 183.0
Aurora Generating Station \| RA Generation \| 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cap on guaranty payment											91.0
Seward Generating Station
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from disposition					$ 75.0	$ 75.0					1.0
Generation capacity (in MW) \| MW						525
Cash on hand transferred to buyer					3.0
Amount of payments after disposal					$ 5.0
Number of annual installments \| installment					5
Seward Generating Station \| Robindale Energy Services, Inc
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Commitment of future inventory purchases					$ 13.0
Seward Generating Station \| Environmental Testing
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Amount of payments after disposal					2.5
Seward Generating Station \| Annual
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Amount of payments after disposal					$ 1.0
Shelby County Energy Center, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from disposition				$ 46.0			$ 46.0
Gain on disposition										$ 29.0
Generation capacity (in MW) \| MW							352
Future revenue rights										$ 10.0
GenOn Americas Generation
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from disposition											$ 0.0	$ 76.0
Generation capacity (in MW) \| MW											6,878
GenOn Americas Generation \| Potrero LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on disposition									$ 74.0
NRG Power Marketing LLC \| GenOn Energy Management
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Emission credit allowances \| allowance								1.3
Proceeds from sale of emission allowances								$ 18.0
Gain on sale of emission allowances								$ 1.0