LOANS RECEIVABLE AND THE ALLOWANCE FOR LOAN LOSSES (Land and Land Development by State) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 3,235,714	$ 3,296,338
Percent of total loans	100.00%	100.00%
Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,167,034
Percent of total loans	67.00%
Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	675,473
Percent of total loans	20.90%
Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	288,512
Percent of total loans	8.90%
Land and land development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	90,992
Percent of total loans	100.00%
Land and land development [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	50,659
Percent of total loans	55.70%
Land and land development [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	36,570
Percent of total loans	40.20%
Land and land development [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,763
Percent of total loans	4.10%
Land and land development - residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	77,010	97,491
Percent of total loans	2.40%	3.00%
Land and land development - residential [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	41,680
Land and land development - residential [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	33,478
Land and land development - residential [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,852
Land and land development - residential [Member] | Acquisition and development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	25,248
Land and land development - residential [Member] | Acquisition and development [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	10,182
Land and land development - residential [Member] | Acquisition and development [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	13,454
Land and land development - residential [Member] | Acquisition and development [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,612
Land and land development - residential [Member] | Improved land and lots [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	42,481
Land and land development - residential [Member] | Improved land and lots [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	23,418
Land and land development - residential [Member] | Improved land and lots [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	18,823
Land and land development - residential [Member] | Improved land and lots [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	240
Land and land development - residential [Member] | Unimproved land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	9,281
Land and land development - residential [Member] | Unimproved land [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	8,080
Land and land development - residential [Member] | Unimproved land [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,201
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	13,982	15,197
Percent of total loans	0.40%	0.50%
Land and land development - commercial and industrial [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	8,979
Land and land development - commercial and industrial [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,092
Land and land development - commercial and industrial [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,911
Land and land development - commercial and industrial [Member] | Acquisition and development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,755
Land and land development - commercial and industrial [Member] | Acquisition and development [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,273
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	482
Land and land development - commercial and industrial [Member] | Improved land and lots [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	4,892
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	4,204
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	136
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	552
Land and land development - commercial and industrial [Member] | Unimproved land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	7,335
Land and land development - commercial and industrial [Member] | Unimproved land [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,502
Land and land development - commercial and industrial [Member] | Unimproved land [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,956
Land and land development - commercial and industrial [Member] | Unimproved land [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 877