LOANS RECEIVABLE AND THE ALLOWANCE FOR LOAN LOSSES (Loans by Geographic Type) (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%
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	104,695
Percent of total loans	3.20%
Commerical real estate - owner-occupied [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	489,581	469,806
Percent of total loans	15.10%	14.20%
Commerical real estate - owner-occupied [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	366,422
Commerical real estate - owner-occupied [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	57,903
Commerical real estate - owner-occupied [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	61,379
Commerical real estate - owner-occupied [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,877
Commerical real estate - investment properties [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	583,641	621,622
Percent of total loans	18.00%	18.90%
Commerical real estate - investment properties [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	450,142
Commerical real estate - investment properties [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	85,416
Commerical real estate - investment properties [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	42,774
Commerical real estate - investment properties [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	5,309
Multifamily real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	137,504	139,710
Percent of total loans	4.30%	4.20%
Multifamily real estate [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	117,654
Multifamily real estate [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	11,309
Multifamily real estate [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	8,249
Multifamily real estate [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	292
Commercial construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	30,229	42,391
Percent of total loans	0.90%	1.30%
Commercial construction [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	20,839
Commercial construction [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	6,107
Commercial construction [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	934
Commercial construction [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,349
Multifamily construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	22,581	19,436
Percent of total loans	0.70%	0.60%
Multifamily construction [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	12,383
Multifamily construction [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	10,198
Multifamily construction [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0
Multifamily construction [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0
One-to four-family construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	160,815	144,177
Percent of total loans	5.00%	4.40%
One-to four-family construction [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	88,090
One-to four-family construction [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	71,663
One-to four-family construction [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,062
One-to four-family construction [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0
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] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0
Land and land development - commercial [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 [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	8,979
Land and land development - commercial [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,092
Land and land development - commercial [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,911
Land and land development - commercial [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0
Commercial business [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	618,049	601,440
Percent of total loans	19.10%	18.20%
Commercial business [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	396,935
Commercial business [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	72,594
Commercial business [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	58,416
Commercial business [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	90,104
Agricultural business, including secured by farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	230,031	218,171
Percent of total loans	7.10%	6.60%
Agricultural business, including secured by farmland [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	108,671
Agricultural business, including secured by farmland [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	51,286
Agricultural business, including secured by farmland [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	70,074
Agricultural business, including secured by farmland [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0
One- to four-family real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	581,670	642,501
Percent of total loans	18.00%	19.50%
One- to four-family real estate [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	360,625
One- to four-family real estate [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	195,364
One- to four-family real estate [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	23,596
One- to four-family real estate [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,085
Consumer secured by one- to four-family [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	170,123	181,049
Percent of total loans	5.30%	5.50%
Consumer secured by one- to four-family [Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	114,405
Consumer secured by one- to four-family [Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	42,395
Consumer secured by one- to four-family [Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	12,644
Consumer secured by one- to four-family [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	679
Consumer - other Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	120,498	103,347
Percent of total loans	3.70%	3.10%
Consumer - other Member] | Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	80,209
Consumer - other Member] | Oregon [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	34,668
Consumer - other Member] | Idaho [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	5,621
Consumer - other Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 0