Business Combinations (Details) - Intermountain Community Bancorp [Member] - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Nov. 01, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Business Combination, Cost of Acquired Entity, Purchase Price, Total	$ 131,935
Business Combination, Acquisition Related Costs		$ 2,436	$ 10,845	$ 4,896
Business Acquisition, Effective Date of Acquisition	Nov. 01, 2014
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	$ 47,283
Business Acquisition, Purchase Price Allocation, Current Assets, Marketable Securities	299,458
Business Acquisition, Purchase Price Allocation, FHLB Stock	2,124
Business Combination, Acquired Receivables, Fair Value	502,595
Business Acquisition, Purchase Price Allocation, Accrued Interest Receivable	4,656
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	20,696
Business Acquisition, Purchase Price Allocation, Other Real Estate Owned	2,752
Business Combination, Purchase Price Allocation, Amortizable Intangible Assets	10,900
Business Combination, Purchase Price Allocation, Other Assets	35,128
Business Acquisition, Purchase Price Allocation, Liabilities, Deposits	(736,795)
Business Acquisition, Purchase Price Allocation, Junior Subordinated Debentures	(22,904)
Business combination, purchase price allocation, securities sold under agreements to repurchase	(59,043)
Business Acquisition, Purchase Price Allocation, Other Noncurrent Liabilities	(13,725)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	93,125
Business Combination, Purchase Price Allocation, Goodwill Amount	$ 38,810
Business Acquisition, Pro Forma Revenue				397,152
Business Acquisition, Pro Forma Net Income (Loss)				$ 85,939
Business Acquisition, Pro Forma Earnings Per Share, Basic				$ 1.56
Business Acquisition, Pro Forma Earnings Per Share, Diluted				$ 1.55
Compensation and employee benefits [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		35	3,828	$ 2,077
Occupancy [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		2,383	2,357	44
Advertising and promotion [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		0	448	464
Data processing and communications [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		18	2,005	0
Legal and professional fees [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		0	1,247	2,114
Other noninterest expenses [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		$ 0	$ 960	$ 197