DEPOSITS AND CUSTOMER REPURCHASE AGREEMENTS (Geographic Concentration of Deposits) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Deposit Liabilities [Line Items]
Total deposits	$ 3,460,324	$ 3,557,804	$ 3,425,749
Total deposits, percent of total	100.00%	100.00%	100.00%
Washington [Member]
Deposit Liabilities [Line Items]
Total deposits	2,616,808
Total deposits, percent of total	75.60%
Oregon [Member]
Deposit Liabilities [Line Items]
Total deposits	604,341
Total deposits, percent of total	17.50%
Idaho [Member]
Deposit Liabilities [Line Items]
Total deposits	$ 239,175
Total deposits, percent of total	6.90%