CASH AND SECURITIES (Available-for-sale Securities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 411,424	$ 474,960
Gross Unrealized Gains	1,812	1,630
Gross Unrealized Losses	(2,215)	(6,310)
Fair Value	411,021us-gaap_AvailableForSaleSecurities	470,280us-gaap_AvailableForSaleSecurities
Percent of Total	100.00%	100.00%
U.S. Government and agency obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	29,973	59,178
Gross Unrealized Gains	8	117
Gross Unrealized Losses	(211)	(635)
Fair Value	29,770	58,660
Percent of Total	7.20%	12.50%
Total municipal bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	49,959	53,071
Gross Unrealized Gains	190	270
Gross Unrealized Losses	(121)	(486)
Fair Value	50,028	52,855
Percent of Total	12.20%	11.20%
Taxable municipal bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	16,565	23,842
Gross Unrealized Gains	65	100
Gross Unrealized Losses	(52)	(278)
Fair Value	16,578	23,664
Percent of Total	4.00%	5.00%
Tax exempt municipal bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	33,394	29,229
Gross Unrealized Gains	125	170
Gross Unrealized Losses	(69)	(208)
Fair Value	33,450	29,191
Percent of Total	8.20%	6.20%
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,000	7,001
Gross Unrealized Gains	18	2
Gross Unrealized Losses	0	(39)
Fair Value	5,018	6,964
Percent of Total	1.20%	1.50%
Total Mortgage-backed or related securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	300,979	330,097
Gross Unrealized Gains	1,429	1,113
Gross Unrealized Losses	(1,598)	(4,600)
Fair Value	300,810	326,610
Percent of Total	73.20%	69.50%
1-4 residential agency guaranteed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	48,001	47,077
Gross Unrealized Gains	758	648
Gross Unrealized Losses	(240)	(838)
Fair Value	48,519	46,887
Percent of Total	11.80%	10.00%
1-4 residential other [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	675	988
Gross Unrealized Gains	38	63
Gross Unrealized Losses	0	0
Fair Value	713	1,051
Percent of Total	0.20%	0.20%
Multifamily agency guaranteed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	241,800	271,428
Gross Unrealized Gains	627	402
Gross Unrealized Losses	(1,346)	(3,392)
Fair Value	241,081	268,438
Percent of Total	58.70%	57.10%
Multifamily other [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,503	10,604
Gross Unrealized Gains	6	0
Gross Unrealized Losses	(12)	(370)
Fair Value	10,497	10,234
Percent of Total	2.50%	2.20%
Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	25,513	25,613
Gross Unrealized Gains	167	128
Gross Unrealized Losses	(285)	(550)
Fair Value	25,395	25,191
Percent of Total	6.20%	5.30%
SLMA [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	15,462	15,553
Gross Unrealized Gains	167	128
Gross Unrealized Losses	0	0
Fair Value	15,629	15,681
Percent of Total	3.80%	3.30%
Other Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,051	10,060
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(285)	(550)
Fair Value	$ 9,766	$ 9,510
Percent of Total	2.40%	2.00%

Available-for-sale Securities, Fair Value Percent of Total Fair Value

No definition available.

Name:	banr_AvailableForSaleSecuritiesFairValuePercentOfTotalFairValue
Namespace Prefix:	banr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (aa)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

+ Details

Name:	us-gaap_AvailableForSaleSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.2)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesAmortizedCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=banr_MortgageBackedSecuritiesOrRelatedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=banr_MultifamilyAgencyGuaranteedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=banr_MultifamilyOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=banr_OneToFourResidentialAgencyGuaranteedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=banr_OneToFourResidentialOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=banr_OtherAssetBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=banr_StudentLoanMarketingAssocationSlmaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_CorporateBondSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_MunicipalBondsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_NontaxableMunicipalBondsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_TaxableMunicipalBondsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_USTreasuryAndGovernmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: