Securities (Carrying Value of Securities Pledged as Collateral) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Carrying amount of securities pledged as collateral	$ 398,889	$ 533,399
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	232,714	341,079
To Federal Reserve Bank To Secure Borrowings [Member]
Schedule of Available-for-sale Securities [Line Items]
Carrying amount of securities pledged as collateral	33,825	48,714
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Carrying amount of securities pledged as collateral	$ 132,350	$ 143,606