LOANS RECEIVABLE AND THE ALLOWANCE FOR LOAN LOSSES (Land and Land Development by State) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 3,522,912	$ 3,418,445	$ 3,240,321
Percent of total loans	100.00%	100.00%	100.00%
Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,289,283
Percent of total loans	65.00%
Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	720,639
Percent of total loans	20.50%
Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	288,762
Percent of total loans	8.20%
Land and land development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	84,597
Percent of total loans	100.00%
Land and land development [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	46,741
Percent of total loans	55.20%
Land and land development [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	34,482
Percent of total loans	40.80%
Land and land development [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,374
Percent of total loans	4.00%
Land and land development - residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	73,733	75,695	78,446
Percent of total loans	2.10%	2.20%	2.40%
Land and land development - residential [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	41,348
Land and land development - residential [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	31,143
Land and land development - residential [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,242
Land and land development - residential [Member] | Acquisition and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	30,440
Land and land development - residential [Member] | Acquisition and Development [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	17,523
Land and land development - residential [Member] | Acquisition and Development [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	11,899
Land and land development - residential [Member] | Acquisition and Development [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,018
Land and land development - residential [Member] | Improved Land and Lots [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	36,733
Land and land development - residential [Member] | Improved Land and Lots [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	17,866
Land and land development - residential [Member] | Improved Land and Lots [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	18,643
Land and land development - residential [Member] | Improved Land and Lots [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	224
Land and land development - residential [Member] | Unimproved Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	6,560
Land and land development - residential [Member] | Unimproved Land [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	5,959
Land and land development - residential [Member] | Unimproved Land [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	601
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	10,864	10,450	12,477
Percent of total loans	0.30%	0.30%	0.40%
Land and land development - commercial and industrial [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	5,393
Land and land development - commercial and industrial [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,339
Land and land development - commercial and industrial [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,132
Land and land development - commercial and industrial [Member] | Acquisition and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	351
Land and land development - commercial and industrial [Member] | Acquisition and Development [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0
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	351
Land and land development - commercial and industrial [Member] | Improved Land and Lots [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,877
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	2,739
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	513
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	625
Land and land development - commercial and industrial [Member] | Unimproved Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	6,636
Land and land development - commercial and industrial [Member] | Unimproved Land [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,654
Land and land development - commercial and industrial [Member] | Unimproved Land [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,826
Land and land development - commercial and industrial [Member] | Unimproved Land [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 1,156