Business Combinations narrative (Details) - Intermountain Community Bancorp [Member] - USD ($) $ in Thousands		12 Months Ended
	Nov. 01, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Business Combination, Purchase Price Allocation, Goodwill Amount	$ 38,810
Business Acquisition, Effective Date of Acquisition	Nov. 01, 2014
Business Combination, Cost of Acquired Entity, Purchase Price, Total	$ 131,935
Business Combination, Acquired Receivables, Fair Value	502,595
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	93,125
Business Combination, Purchase Price Allocation, Amortizable Intangible Assets	$ 10,900
business combinations, core deposit intangible percentage of core deposits	1.75%
Business Combination, Acquisition Related Costs		$ 2,436	$ 10,845	$ 4,896
Business Combination, Purchase Price Allocation, Other Assets	$ 35,128
Business Acquisition, Purchase Price Allocation, Liabilities, Deposits	$ 736,795
Business Acquisition, Percentage of Voting Interests Acquired	100.00%