Securities (Carrying Value of Securities Pledged as Collateral) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Carrying amount of securities pledged as collateral	$ 533,399	$ 526,643
To Washington and Oregon State To Secure Public Deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Carrying amount of securities pledged as collateral	341,079	328,400
To Federal Reserve Bank To Secure Borrowings [Member]
Schedule of Available-for-sale Securities [Line Items]
Carrying amount of securities pledged as collateral	48,714	41,146
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Carrying amount of securities pledged as collateral	$ 143,606	$ 157,097