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