Investments (Narrative) (Details)	6 Months Ended
	Jun. 30, 2015 USD ($) item	Dec. 31, 2014 USD ($) item
Investments [Abstract]
Number of securities with unrealized losses | item	193	134
Schedule of Available-for-sale Securities [Line Items]
Investment securities available for sale	$ 506,919,000	$ 511,883,000
Low Income Housing Tax Credit Fund Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amount of investments in housing fund	5,300,000
Tax credit amount from housing fund investments	386,000
Pass through operating loss	483,000
States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities available for sale	99,100,000
Columbia River People's Utility District [Member] | States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities available for sale	$ 1,100,000