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Years Subject to Examination (Details) | 12 Months Ended
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Dec. 31, 2014
Federal |
Income Tax Examination |
Income tax return jurisdictions and years that remain subject to examination | 2008, 2009, 2010, 2011, 2012 and 2013
Montana |
Income Tax Examination |
Income tax return jurisdictions and years that remain subject to examination | 2011, 2012 and 2013
Idaho |
Income Tax Examination |
Income tax return jurisdictions and years that remain subject to examination | 2009, 2010, 2011, 2012 and 2013
Colorado |
Income Tax Examination |
Income tax return jurisdictions and years that remain subject to examination | 2008, 2009, 2010, 2011, 2012 and 2013
Utah |
Income Tax Examination |
Income tax return jurisdictions and years that remain subject to examination | 2011, 2012 and 2013

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