Business Combinations (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended
	Nov. 01, 2017	Mar. 31, 2018	Mar. 31, 2017
Business Acquisition [Line Items]
Threshold for average assets requiring CFPB examination		$ 10,000,000
Estimated pre-tax annual impact of no longer qualifying for the small issuer exemption from interchange fee cap		10,000
Pacific Continental [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		4,265	$ 1,364
Business Acquisition, Pro Forma Revenue			139,363
Business Combination, Consideration Transferred	$ 637,103
Business Acquisition, Effective Date of Acquisition	Nov. 01, 2017
Business Acquisition, Percentage of Voting Interests Acquired	100.00%
Business Combination, Purchase Price Allocation, Goodwill Amount	$ 383,080
Business Combination, Purchase Price Allocation, Amortizable Intangible Assets	46,875
Business Combination, Purchase Price Allocation, Other Assets	50,638
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	2,554,514
Business Combination, Purchase Price Allocation, Liabilities, Deposits	(2,118,982)
Business Combination, Purchase Price Allocation, Federal Home Loan bank advances	(101,127)
Business Combination, Purchase Price Allocation, Subordinated Debt	(35,678)
Business Combination, Purchase Price Allocation, Junior Subordinated Debentures	(14,434)
Business combination, purchase price allocation, securities sold under agreements to repurchase	(1,617)
Business Combination, Purchase Price Allocation, Other Liabilities	(28,653)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	(2,300,491)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	$ 254,023
business combinations, core deposit intangible percentage of core deposits	2.34%
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	$ 81,190
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Marketable Securities	449,291
Business Combination, Purchase Price Allocation, FHLB Stock	7,084
Business Combination, Acquired Receivable, Fair Value	1,873,987
Business Combination, Purchase Price Allocation, Accrued Interest Receivable	7,827
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	27,343
Business Combination, Purchase Price Allocation, Other Real Estate Owned	$ 10,279
Business Acquisition, Pro Forma Net Income (Loss)			$ 37,147
Business Acquisition, Pro Forma Earnings Per Share, Basic			$ 0.52
Business Acquisition, Pro Forma Earnings Per Share, Diluted			$ 0.52
Pacific Continental [Member] | Compensation and employee benefits [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		1,556	$ 0
Pacific Continental [Member] | Other noninterest expenses [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		332	46
Pacific Continental [Member] | Legal and professional fees [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		574	1,311
Pacific Continental [Member] | Data processing [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		287	0
Pacific Continental [Member] | Advertising and promotion [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		512	6
Pacific Continental [Member] | Occupancy [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		$ 1,004	$ 1