Federal and State Income Taxes - Years Subject to Examination (Details)	12 Months Ended
	Dec. 31, 2020
Federal
Income Tax Examination
Income tax return jurisdictions and years that remain subject to examination	2010, 2011, 2012, 2013, 2016, 2017, 2018 and 2019
Colorado
Income Tax Examination
Income tax return jurisdictions and years that remain subject to examination	2010, 2011, 2012, 2016, 2017, 2018, and 2019
Arizona & California
Income Tax Examination
Income tax return jurisdictions and years that remain subject to examination	2016, 2017, 2018 and 2019
Montana, Idaho, Utah, & North Dakota
Income Tax Examination
Income tax return jurisdictions and years that remain subject to examination	2017, 2018 and 2019
Alabama, Alaska, Arkansas, Connecticut, Florida, Georgia, Indiana, Kentucky, Louisiana, Massachusetts, Michigan, Minnesota, Missouri, New Jersey, New York, Pennsylvania, South Carolina, Tennessee, Texas, Virginia, & Wisconsin
Income Tax Examination
Income tax return jurisdictions and years that remain subject to examination	2019