DEPOSITS AND CUSTOMER REPURCHASE AGREEMENTS (Geographic Concentration of Deposits) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Deposit Liabilities [Line Items]
Total deposits	$ 3,535,285	$ 3,557,804	$ 3,486,372
Percent of total deposits	100.00%	100.00%	100.00%
Washington [Member]
Deposit Liabilities [Line Items]
Total deposits	2,679,104
Percent of total deposits	75.80%
Oregon [Member]
Deposit Liabilities [Line Items]
Total deposits	610,205
Percent of total deposits	17.30%
Idaho [Member]
Deposit Liabilities [Line Items]
Total deposits	$ 245,976
Percent of total deposits	6.90%