Business Combinations (Details) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Nov. 01, 2014	Apr. 02, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Cost of Acquired Entity, Purchase Price, Total	$ 131,935
Business Combination, Acquisition Related Costs			$ 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	360,655
Business Acquisition, Pro Forma Net Income (Loss)			$ 85,939	$ 72,587
Business Acquisition, Pro Forma Earnings Per Share, Basic			$ 1.56	$ 1.32
Business Acquisition, Pro Forma Earnings Per Share, Diluted			$ 1.55	$ 1.31
West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Cost of Acquired Entity, Purchase Price, Total		$ 540,791
Business Combination, Acquisition Related Costs			$ 72	$ 4,536	$ 25,488
Business Acquisition, Effective Date of Acquisition		Apr. 01, 2013
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents		$ 110,440
Business Acquisition, Purchase Price Allocation, Current Assets, Marketable Securities		730,842
Business Acquisition, Purchase Price Allocation, FHLB Stock		11,824
Business Combination, Acquired Receivables, Fair Value		1,407,798
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment		35,884
Business Acquisition, Purchase Price Allocation, Other Real Estate Owned		14,708
Business Combination, Purchase Price Allocation, Amortizable Intangible Assets		15,257
Business Combination, Purchase Price Allocation, Other Assets		75,820
Business Acquisition, Purchase Price Allocation, Liabilities, Deposits		(1,883,407)
business combination, recognized identifiable assets acquired and liabilities assumed, Federal Home Loan Bank Advances		(128,885)
Business Acquisition, Purchase Price Allocation, Junior Subordinated Debentures		(51,000)
Business Acquisition, Purchase Price Allocation, Other Noncurrent Liabilities		(26,888)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net		312,393
Business Combination, Purchase Price Allocation, Goodwill Amount		$ 228,398
Business Acquisition, Pro Forma Revenue				337,712
Business Acquisition, Pro Forma Net Income (Loss)				$ 76,496
Business Acquisition, Pro Forma Earnings Per Share, Basic				$ 1.50
Business Acquisition, Pro Forma Earnings Per Share, Diluted				$ 1.46
Compensation and employee benefits [Member] | Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs			3,828	$ 2,077
Compensation and employee benefits [Member] | West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs			65	798	8,440
Occupancy [Member] | Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs			2,357	44
Occupancy [Member] | West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs			0	696	4,684
Advertising and promotion [Member] | Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs			448	464
Advertising and promotion [Member] | West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs			0	0	877
Data processing and communications [Member] | Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs			2,005	0
Data processing and communications [Member] | West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs			0	684	767
Legal and professional fees [Member] | Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs			1,247	2,114
Legal and professional fees [Member] | West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs			7	383	4,766
Other noninterest expenses [Member] | Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs			960	197
Other noninterest expenses [Member] | West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs			$ 0	$ 1,975	$ 5,954