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Goodwill and Other Intangibles - Narrative (Details) - USD ($) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2019 | Dec. 31, 2019 | Dec. 31, 2018
Goodwill and Other Intangibles |  |  |
Goodwill | $ 579,000,000 | $ 579,000,000 | $ 573,000,000
Impairment |  | 2,000,000 | 6,000,000
Emission allowances held-for-sale | 6,000,000 | 6,000,000 | 12,000,000
Emission Allowances |  |  |
Goodwill and Other Intangibles |  |  |
Impairment |  | 0 | 5,000,000
Impairment related to power purchase agreements |  |  | 0
BETM | Held-for-sale |  |  |
Goodwill and Other Intangibles |  |  |
Goodwill | 21,000,000 | 21,000,000 |
Goodwill, Impairment Loss | 90,000,000 |  |
Midwest Generation |  |  |
Goodwill and Other Intangibles |  |  |
Goodwill | 165,000,000 | 165,000,000 |
Midwest Generation | Lease Agreements |  |  |
Goodwill and Other Intangibles |  |  |
Out of market contracts |  |  | $ 121,000,000
Retail |  |  |
Goodwill and Other Intangibles |  |  |
Goodwill | $ 414,000,000 | $ 414,000,000 |

X
- Definition Impairment of Intangible Assets, Finite-Lived, Net Impairment of Intangible Assets, finite-lived less accumulated amortization. + References No definition available. + Details
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- Definition This element represents the emission allowances held-for-sale that are included in other noncurrent assets on the entity's balance sheet. + References No definition available. + Details
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- Definition Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266 + Details
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