REGULATORY CAPITAL REQUIREMENTS (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Total capital to risk-weighted assets:
Actual	$ 631,674	$ 581,796
Actual, Ratio	16.99%	16.96%
Minimum for Capital Adequacy Purposes	297,493	274,460
Minimum for Capital Adequacy Purposes, Ratio	8.00%	8.00%
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions, Ratio	10.00%
Tier 1 capital to risk-weighted assets:
Actual	584,838	538,485
Actual, Ratio	15.73%	15.70%
Minimum for Capital Adequacy Purposes	148,747	137,230
Minimum for Capital Adequacy Purposes, Ratio	4.00%	4.00%
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions, Ratio	6.00%
Tier 1 leverage capital to average assets:
Actual	584,838	538,485
Actual, Ratio	13.64%	12.74%
Minimum for Capital Adequacy Purposes	171,553	169,035
Minimum for Capital Adequacy Purposes, Ratio	4.00%	4.00%
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions, Ratio	5.00%
Banner Bank [Member]
Total capital to risk-weighted assets:
Actual	557,253	533,128
Actual, Ratio	15.75%	16.38%
Minimum for Capital Adequacy Purposes	282,984	260,390
Minimum for Capital Adequacy Purposes, Ratio	8.00%	8.00%
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions	353,730	325,488
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	512,689	492,025
Actual, Ratio	14.49%	15.12%
Minimum for Capital Adequacy Purposes	141,192	130,195
Minimum for Capital Adequacy Purposes, Ratio	4.00%	4.00%
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions	212,238	195,293
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	512,689	492,025
Actual, Ratio	12.65%	12.29%
Minimum for Capital Adequacy Purposes	162,174	160,104
Minimum for Capital Adequacy Purposes, Ratio	4.00%	4.00%
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions	202,707	200,130
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	34,795	32,913
Actual, Ratio	18.73%	17.53%
Minimum for Capital Adequacy Purposes	14,859	15,019
Minimum for Capital Adequacy Purposes, Ratio	8.00%	8.00%
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions	18,574	18,773
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	32,469	30,558
Actual, Ratio	17.48%	16.28%
Minimum for Capital Adequacy Purposes	7,430	7,509
Minimum for Capital Adequacy Purposes, Ratio	4.00%	4.00%
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions	11,144	11,264
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	32,469	30,558
Actual, Ratio	13.60%	13.02%
Minimum for Capital Adequacy Purposes	9,553	9,388
Minimum for Capital Adequacy Purposes, Ratio	4.00%	4.00%
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions	$ 11,941	$ 11,735
Minimum to be Categorized as Well-Capitalized Under Prompt Corrective Action Provisions, Ratio	5.00%	5.00%