DEPOSITS AND CUSTOMER REPURCHASE AGREEMENTS (Geographic Concentration of Deposits) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Deposit Liabilities [Line Items]
Total deposits	$ 3,486,372	$ 3,475,654	$ 3,537,434
Washington [Member]
Deposit Liabilities [Line Items]
Total deposits	2,660,783
Oregon [Member]
Deposit Liabilities [Line Items]
Total deposits	597,826
Idaho [Member]
Deposit Liabilities [Line Items]
Total deposits	$ 227,763