Business Combinations (Details) (USD $)	0 Months Ended	12 Months Ended		0 Months Ended	12 Months Ended
	Nov. 01, 2014	Dec. 31, 2014	Dec. 31, 2013	Apr. 02, 2013	Dec. 31, 2012
Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		$ 4,896,000
Business Acquisition, Pro Forma Revenue		397,152,000	360,655,000
Business Acquisition, Effective Date of Acquisition	Nov. 01, 2014
Business Acquisition, Purchase Price Allocation, Current Assets, Marketable Securities	299,458,000
Business Acquisition, Purchase Price Allocation, Accrued Interest Receivable	4,656,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	20,696,000
Business Combination, Purchase Price Allocation, Amortizable Intangible Assets	10,900,000
Business Combination, Purchase Price Allocation, Other Assets	35,353,000
Business Acquisition, Purchase Price Allocation, Liabilities, Deposits	(736,795,000)
Business Acquisition, Purchase Price Allocation, Other Noncurrent Liabilities	(13,725,000)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	93,350,000
Business Acquisition, Purchase Price Allocation, FHLB Stock	2,124,000
business combinations, purchase price allocation, loans	502,595,000
Business Combination, Purchase Price Allocation, Goodwill Amount	38,585,000
Business Combination, Cost of Acquired Entity, Purchase Price, Total	131,935,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	47,283,000
Business Acquisition, Purchase Price Allocation, Other Real Estate Owned	2,752,000
Business Acquisition, Purchase Price Allocation, Junior Subordinated Debentures	(22,904,000)
Business combination, purchase price allocation, securities sold under agreements to repurchase	(59,043,000)
Business Acquisition, Pro Forma Net Income (Loss)		85,939,000	72,587,000
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, Acquisition Related Costs		4,536,000	25,488,000		1,780,000
Business Acquisition, Pro Forma Revenue			337,712,000		420,167,000
Business Acquisition, Effective Date of Acquisition				Apr. 01, 2013
Business Combination, Acquired Receivables, Fair Value				1,410,000,000
Business Combination, Purchase Price Allocation, Amortizable Intangible Assets				15,300,000
Business Acquisition, Purchase Price Allocation, Liabilities, Deposits				(1,880,000,000)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net				312,400,000
Business Combination, Purchase Price Allocation, Goodwill Amount				228,400,000
Business Acquisition, Pro Forma Net Income (Loss)			76,496,000		91,261,000
Business Acquisition, Pro Forma Earnings Per Share, Basic			$ 1.50		$ 1.79
Business Acquisition, Pro Forma Earnings Per Share, Diluted			$ 1.46		$ 1.74
Compensation and employee benefits [Member] | Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		2,077,000
Compensation and employee benefits [Member] | West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		798,000	8,440,000		0
Occupancy [Member] | Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		44,000
Occupancy [Member] | West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		696,000	4,684,000		0
Advertising and promotion [Member] | Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		464,000
Advertising and promotion [Member] | West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		0	877,000		2,000
Data processing and communications [Member] | Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		0
Data processing and communications [Member] | West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		684,000	767,000		0
Legal and professional fees [Member] | Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		2,114,000
Legal and professional fees [Member] | West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		383,000	4,766,000		1,760,000
Other noninterest expenses [Member] | Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		197,000
Other noninterest expenses [Member] | West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		$ 1,975,000	$ 5,954,000		$ 18,000