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Income Taxes Income taxes (Details) - USD ($) $ in Millions | Dec. 31, 2016 | Dec. 31, 2015
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Operating Loss Carryforwards [Line Items] |  |
Tax Credit Carryforward, Federal | $ 56 |
Deferred Tax Assets, Valuation Allowance | 0 | $ 0
Unrecognized Tax Benefits | $ 0 | $ 0

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- Definition The amount of the federal tax credit carryforward, berfore tax effects, available to reduce future taxable income under enacted tax laws. + 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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32537-109319 + Details
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- Definition Amount of unrecognized tax benefits. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=65882285&loc=SL6600010-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Unrecognized Tax Benefit -URI http://asc.fasb.org/extlink&oid=6527854 + Details
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