REGULATORY CAPITAL REQUIREMENTS (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Total capital to risk-weighted assets:
Actual	$ 581,796	$ 615,092
Actual, Ratio	16.96%	18.07%
Minimum for Capital Adequacy Purposes	274,460	272,344
Minimum for Capital Adequacy Purposes, Ratio	8.00%	8.00%
Tier 1 capital to risk-weighted assets:
Actual	538,485	572,036
Actual, Ratio	15.70%	16.80%
Minimum for Capital Adequacy Purposes	137,230	136,172
Minimum for Capital Adequacy Purposes, Ratio	4.00%	4.00%
Tier 1 leverage capital to average assets:
Actual	538,485	572,036
Actual, Ratio	12.74%	13.44%
Minimum for Capital Adequacy Purposes	169,035	170,242
Minimum for Capital Adequacy Purposes, Ratio	4.00%	4.00%
Banner Bank [Member]
Total capital to risk-weighted assets:
Actual	533,128	511,594
Actual, Ratio	16.38%	15.81%
Minimum for Capital Adequacy Purposes	260,390	258,900
Minimum for Capital Adequacy Purposes, Ratio	8.00%	8.00%
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions	325,488	323,625
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions, Ratio	10.00%	10.00%
Tier 1 capital to risk-weighted assets:
Actual	492,025	470,668
Actual, Ratio	15.12%	14.54%
Minimum for Capital Adequacy Purposes	130,195	129,450
Minimum for Capital Adequacy Purposes, Ratio	4.00%	4.00%
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions	195,293	194,175
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions, Ratio	6.00%	6.00%
Tier 1 leverage capital to average assets:
Actual	492,025	470,668
Actual, Ratio	12.29%	11.71%
Minimum for Capital Adequacy Purposes	160,104	160,721
Minimum for Capital Adequacy Purposes, Ratio	4.00%	4.00%
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions	200,130	200,902
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions, Ratio	5.00%	5.00%
Islanders Bank
Total capital to risk-weighted assets:
Actual	32,913	30,627
Actual, Ratio	17.53%	16.06%
Minimum for Capital Adequacy Purposes	15,019	15,255
Minimum for Capital Adequacy Purposes, Ratio	8.00%	8.00%
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions	18,773	19,068
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions, Ratio	10.00%	10.00%
Tier 1 capital to risk-weighted assets:
Actual	30,558	28,237
Actual, Ratio	16.28%	14.81%
Minimum for Capital Adequacy Purposes	7,509	7,627
Minimum for Capital Adequacy Purposes, Ratio	4.00%	4.00%
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions	11,264	11,441
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions, Ratio	6.00%	6.00%
Tier 1 leverage capital to average assets:
Actual	30,558	28,237
Actual, Ratio	13.02%	12.08%
Minimum for Capital Adequacy Purposes	9,388	9,351
Minimum for Capital Adequacy Purposes, Ratio	4.00%	4.00%
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions	$ 11,735	$ 11,689
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions, Ratio	5.00%	5.00%