Securities (Carrying Value of Securities Pledged as Collateral) (Details) $ in Thousands	Sep. 30, 2018 USD ($)
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Restricted	$ 427,902
Washington and Oregon State Public Deposits [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Restricted	256,078
Federal Reserve Bank Advances [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Restricted	51,843
Other Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Restricted	$ 119,981