Securities (Carrying Value of Securities Pledged as Collateral) (Details) $ in Thousands	Mar. 31, 2019 USD ($)
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Restricted	$ 473,287
Washington and Oregon State Public Deposits [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Restricted	277,815
Federal Reserve Bank Advances [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Restricted	54,717
Other Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Restricted	$ 140,755