Acquisitions Business Combinations (Details) $ / shares in Units, $ in Thousands			12 Months Ended			1080 Months Ended
	Jul. 24, 2015 USD ($)	Jul. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Oct. 17, 2104
Business Acquisition [Line Items]
Acquisition Expense			$ 795	$ 4,017	$ 0
Goodwill, Purchase Accounting Adjustments			$ 1,199
United Bank [Member]
Business Acquisition [Line Items]
Number of Subsidiary Banks	1
Number of Shared Markets	3
Estimate of Payments to Acquire Businesses, Gross	$ 7,234
Business Acquisition, Effective Date of Acquisition	Jul. 24, 2015
Mountain West Bank
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross		$ 38,479
Business Combination, Consideration Transferred		$ 74,451
Business Acquisition, Effective Date of Acquisition		Jul. 31, 2014
Business Acquisition, Date of Merger						Oct. 17, 2014
Mountain West Bank | Class A Common Stock
Business Acquisition [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares		1,378,230	1,378,230
Business Acquisition, Share Price | $ / shares		$ 26.10