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Income Taxes (Narrative) (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2019 | Jun. 30, 2019 | Jun. 30, 2018 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Income Taxes [Abstract] |  |  |  |  |  |
Federal statutory tax rate |  |  |  | 21.00% | 21.00% | 21.00%
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability |  | $ (21) | $ (31) |  |  |
Total accrued liabilities for interest and penalties |  |  |  | $ 8 | $ 3 |
Total interest and penalties recognized as part of income tax expense | $ 11 |  |  | $ 5 | $ (4) | $ (1)
Tax expense recognized as a part of income tax examination | 10 |  |  |  |  |
Interest expense recognized as a part of income tax examination | $ 1 |  |  |  |  |
Income tax examination refund |  |  | $ 19 |  |  |

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- Definition Percentage of domestic federal statutory tax rate applicable to pretax income (loss). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 6.I.Fact.4) -URI http://asc.fasb.org/extlink&oid=116825942&loc=d3e330036-122817 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 + Details
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- Definition The amount of estimated interest recognized in the period arising from income tax examinations. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319 + Details
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- Definition The amount of estimated penalties and interest accrued as of the balance sheet date arising from income tax examinations. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319 + Details
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