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Income Taxes Operating Loss Carryforwards (Details) - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
U.K. |  |
Operating Loss Carryforwards [Line Items] |  |
Operating loss carryforwards | $ 438 | $ 541
Interest carryforwards | 411 | 400
Interest carryforwards | 203 | 53
U.S. Federal |  |
Operating Loss Carryforwards [Line Items] |  |
Operating loss carryforwards | 1 | 2
Interest carryforwards | 112 | 367
Interest carryforwards | 355 | 424
U.S. State |  |
Operating Loss Carryforwards [Line Items] |  |
Operating loss carryforwards | 376 | 315
Interest carryforwards | 123 | 221
Interest carryforwards | 172 | 227
Other |  |
Operating Loss Carryforwards [Line Items] |  |
Operating loss carryforwards | 308 | 369
Interest carryforwards | 29 | 30
Interest carryforwards | $ 159 | $ 186

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- Definition Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319 + Details
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