Business Combinations (Narrative) (Details) (USD $)	3 Months Ended	12 Months Ended			0 Months Ended
	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012 Acquisitions	May 01, 2014		Jul. 15, 2013	Jan. 09, 2013	Sep. 14, 2012 Branch	Apr. 30, 2014	Jul. 14, 2013 Branch	Jan. 08, 2013
Business Acquisition [Line Items]
Number of acquisitions completed				0
Goodwill, other changes	$ 118,000	$ 722,000
Adjustment to goodwill related to bank owned life insurance obligation	265,000
Adjustment to goodwill related to loan discount correction		489,000
Adjustment to goodwill related to FDIC indemnification update		233,000
Adjustment to goodwill related to FDIC receivable update		252,000
Adjustment to goodwill related to deferred tax impact of other adjustments	342,000	252,000
Adjustment to goodwill related to correction in stock issuance costs	489,000
Stock issuance costs in connection with business combinations		489,000	0	0
Goodwill		119,029,000	29,365,000
Bargain purchase gain on bank acquisition		0	399,000	0
Whidbey Island Bank
Business Acquisition [Line Items]
Number of acquired branches to operate under legacy name					6
Washington Banking
Business Acquisition [Line Items]
Common stock, shares outstanding of acquired entity										15,587,154
Washington Banking
Business Acquisition [Line Items]
Number of shares of common stock issued					0.89000
Share price paid in cash (in usd per share)					$ 2.75
Closing price per share (in usd per share)										16.16
Total consideration paid					269,619,000
Business acquisition, number of shares issued					14,000,178
Capitalized stock issuance costs					489,000
Stock issuance costs in connection with business combinations		9,100,000	890,000
Cash paid					42,895,000	[1]
Goodwill					89,664,000
Valley Acquisition
Business Acquisition [Line Items]
Number of shares of common stock issued							1.3611
Business acquisition, number of shares issued							1,533,267
Capitalized stock issuance costs							157,000
Stock issuance costs in connection with business combinations		443,000	2,100,000
Number of branches operating											8
Business acquisition, price per share (in usd per share)							$ 19.50
Cash paid							22,000,000
Common stock issued, fair value							24,200,000
Goodwill							16,400,000
Valley Acquisition | To be Maintained
Business Acquisition [Line Items]
Number of branches operating											4
Valley Acquisition | To be Disposed
Business Acquisition [Line Items]
Number of branches operating											4
Valley Acquisition | To be Terminated
Business Acquisition [Line Items]
Number of branches operating											3
Valley Acquisition | Held-for-sale
Business Acquisition [Line Items]
Number of branches operating											1
Northwest Commercial Bank
Business Acquisition [Line Items]
Total consideration paid								2,967,000
Stock issuance costs in connection with business combinations		0	794,000	616,000
Goodwill								(399,000)
Number of branches acquired									2
Redemption of preferred stock												2,000,000
Business acquisition, share price (in usd per share)								$ 5.50
Business acquisition, contingent cash consideration settled								491,000
Bargain purchase gain on bank acquisition								$ 399,000

[1] Includes $3,000 of cash paid due to fractional shares and $27,000 of cash paid from dissenters.