Securities (Carrying Value of Securities Pledged as Collateral) (Details) $ in Thousands	Sep. 30, 2015 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Carrying amount of securities pledged as collateral	$ 533,086
Washington and Oregon State Public Deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Carrying amount of securities pledged as collateral	328,476
Federal Reserve Bank Advances [Member]
Schedule of Available-for-sale Securities [Line Items]
Carrying amount of securities pledged as collateral	55,578
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Carrying amount of securities pledged as collateral	$ 149,032