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Asset Retirement Obligation (Tables) | 12 Months Ended
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Dec. 31, 2020
Asset Retirement Obligation Disclosure [Abstract] |
Schedule of Asset Retirement Obligations [Table Text Block] | The following table presents amounts recognized related to asset retirement obligations for the periods indicated (in millions):
|  | 2020 |  | 2019
Balance at January 1 |  | $ | 428 |  |  | $ | 415 |
Additional liabilities incurred |  | 42 |  |  | 19 |
Liabilities settled |  | (20) |  |  | (12) |
Accretion expense |  | 22 |  |  | 21 |
Change in estimated cash flows |  | 3 |  |  | 58 |
Sale of plants |  | (13) |  |  | (71) |
Other |  | — |  |  | (2) |
Balance at December 31 |  | $ | 462 |  |  | $ | 428 |

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- Definition Tabular disclosure of the carrying amount of a liability for asset retirement obligations. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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