Securities (Carrying Value of Securities Pledged as Collateral) (Details) (USD $) In Thousands	Sep. 30, 2011
Carrying amount of securities pledged as collateral	$ 438,837
To Washington and Oregon State To Secure Public Deposits [Member]
Carrying amount of securities pledged as collateral	237,671
To Federal Home Loan Bank To Secure Advances [Member]
Carrying amount of securities pledged as collateral	95,139
To Federal Reserve Bank To Secure Borrowings [Member]
Carrying amount of securities pledged as collateral	55,947
Repurchase Agreement [Member]
Carrying amount of securities pledged as collateral	0
Interest Rate Contracts [Member]
Carrying amount of securities pledged as collateral	0
Other Securities Pledged [Member]
Carrying amount of securities pledged as collateral	$ 50,080