Investment Securities - Amortized Cost and Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Scheduled of amortized cost and fair value of securities pledged as collateral
Amortized Cost	$ 245,172	$ 247,872
Fair Value	246,547	248,087
Washington and Oregon state to secure public deposits
Scheduled of amortized cost and fair value of securities pledged as collateral
Amortized Cost	208,907	214,834
Fair Value	210,420	215,247
Repurchase agreements
Scheduled of amortized cost and fair value of securities pledged as collateral
Amortized Cost	32,731	29,481
Fair Value	32,591	29,294
Other securities pledged
Scheduled of amortized cost and fair value of securities pledged as collateral
Amortized Cost	3,534	3,557
Fair Value	$ 3,536	$ 3,546