LOANS RECEIVABLE AND THE ALLOWANCE FOR LOAN LOSSES (Land and Land Development by State) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 3,213,523	$ 3,296,338	$ 3,225,246
Percent of total loans	100.00%	100.00%	100.00%
Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,161,333
Percent of total loans	67.30%
Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	671,391
Percent of total loans	20.90%
Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	283,917
Percent of total loans	8.80%
Land and land development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	94,174
Percent of total loans	100.00%
Land and land development [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	48,386
Percent of total loans	51.40%
Land and land development [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	41,888
Percent of total loans	44.50%
Land and land development [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,900
Percent of total loans	4.10%
Land and land development - residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	79,932	97,491	96,875
Percent of total loans	2.50%	3.00%	3.00%
Land and land development - residential [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	39,181
Land and land development - residential [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	38,781
Land and land development - residential [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,970
Land and land development - residential [Member] | Acquisition and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	23,759
Land and land development - residential [Member] | Acquisition and Development [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	6,229
Land and land development - residential [Member] | Acquisition and Development [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	15,820
Land and land development - residential [Member] | Acquisition and Development [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,710
Land and land development - residential [Member] | Improved Land and Lots [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	43,260
Land and land development - residential [Member] | Improved Land and Lots [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	22,727
Land and land development - residential [Member] | Improved Land and Lots [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	20,273
Land and land development - residential [Member] | Improved Land and Lots [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	260
Land and land development - residential [Member] | Unimproved Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	12,913
Land and land development - residential [Member] | Unimproved Land [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	10,225
Land and land development - residential [Member] | Unimproved Land [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,688
Land and land development - residential [Member] | Unimproved Land [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0
Land and land development - commercial and industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	14,242	15,197	19,173
Percent of total loans	0.40%	0.50%	0.60%
Land and land development - commercial and industrial [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	9,205
Land and land development - commercial and industrial [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,107
Land and land development - commercial and industrial [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,930
Land and land development - commercial and industrial [Member] | Acquisition and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,854
Land and land development - commercial and industrial [Member] | Acquisition and Development [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,370
Land and land development - commercial and industrial [Member] | Acquisition and Development [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0
Land and land development - commercial and industrial [Member] | Acquisition and Development [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	484
Land and land development - commercial and industrial [Member] | Improved Land and Lots [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	4,166
Land and land development - commercial and industrial [Member] | Improved Land and Lots [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,470
Land and land development - commercial and industrial [Member] | Improved Land and Lots [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	138
Land and land development - commercial and industrial [Member] | Improved Land and Lots [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	558
Land and land development - commercial and industrial [Member] | Unimproved Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	8,222
Land and land development - commercial and industrial [Member] | Unimproved Land [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	4,365
Land and land development - commercial and industrial [Member] | Unimproved Land [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,969
Land and land development - commercial and industrial [Member] | Unimproved Land [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 888