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Income Taxes Operating Loss Carryforwards (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Operating Loss Carryforwards [Line Items] |  |
Interest carryforwards |  | $ 196
U.K. |  |
Operating Loss Carryforwards [Line Items] |  |
Operating loss carryforwards | $ 541 | 675
Interest carryforwards | 400 | 415
Interest carryforwards | 53 | 0
U.S. Federal |  |
Operating Loss Carryforwards [Line Items] |  |
Operating loss carryforwards | 2 | 36
Interest carryforwards | 367 | 0
Interest carryforwards | 424 | 0
U.S. State |  |
Operating Loss Carryforwards [Line Items] |  |
Operating loss carryforwards | 315 | 412
Interest carryforwards | 221 | 0
Interest carryforwards | 227 | 0
Other |  |
Operating Loss Carryforwards [Line Items] |  |
Operating loss carryforwards | 369 | 392
Interest carryforwards | 30 | 36
Interest carryforwards | $ 186 | $ 196

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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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