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Income Taxes - Schedule of Changes in Valuation Allowance (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Income Tax Disclosure [Abstract] |  |  |
Balance at beginning of year | $ 2,121 | $ 2,357 | $ 2,459
Increase to allowance | 136 | 19 | 119
Release of allowance | (50) | (211) | (144)
Acquisitions and divestitures | 0 | (2) | 0
Tax apportionment, tax rate and tax law changes | (23) | (13) | (14)
Foreign currency translation | 123 | (29) | (63)
Balance at end of year | $ 2,307 | $ 2,121 | $ 2,357

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- Definition Change in valuation allowance related to deferred state income taxes. + References No definition available. + Details
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- Definition Deferred tax assets valuation acquisitions divestitures. + References No definition available. + Details
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- Definition Deferred tax assets valuation foreign currency translation. + References No definition available. + Details
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- Definition Deferred tax assets valuation release of allowance. + References No definition available. + Details
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- Definition Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319 + Details
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- Definition Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319 + Details
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