Securities (Carrying Value of Securities Pledged as Collateral) (Details) $ in Thousands	Mar. 31, 2016 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Carrying amount of securities pledged as collateral	$ 544,854
Washington and Oregon State Public Deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Carrying amount of securities pledged as collateral	339,424
Federal Reserve Bank Advances [Member]
Schedule of Available-for-sale Securities [Line Items]
Carrying amount of securities pledged as collateral	48,879
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Carrying amount of securities pledged as collateral	$ 156,551