Amount of asset retirement obligations divested during the period.

No definition available.

Name:	brn_AssetRetirementObligationLiabilitiesDivested
Namespace Prefix:	brn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Collaborative Agreement, Purchase Price

+ References

No definition available.

+ Details

Name:	brn_CollaborativeAgreementPurchasePrice
Namespace Prefix:	brn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

Name:	brn_OilAndNaturalGasPropertiesLineItems
Namespace Prefix:	brn_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percent Difference in Capitalized Costs Divided by Proved Reserves if the Gain is Recorded as Opposed to being Credited against the full-cost pool

+ References

No definition available.

+ Details

Name:	brn_PercentDifferenceinCapitalizedCostsDividedbyProvedReservesiftheGainisRecordedasOpposedtobeingCreditedagainstthefullcostpool
Namespace Prefix:	brn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Sale Of Oil And Gas Property And Equipment, Number Of Separate Independent Third Parties

+ References

No definition available.

+ Details

Name:	brn_SaleOfOilAndGasPropertyAndEquipmentNumberOfSeparateIndependentThirdParties
Namespace Prefix:	brn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of asset retirement obligations incurred during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

+ Details

Name:	us-gaap_AssetRetirementObligationLiabilitiesIncurred
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of gain (loss) on sale or disposal of oil and gas property or timber property.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

+ Details

Name:	us-gaap_GainLossOnSaleOfProperty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Carrying amount due within one year of the balance sheet date (or one operating cycle, if longer) from tax authorities as of the balance sheet date representing refunds of overpayments or recoveries based on agreed-upon resolutions of disputes.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.5(c))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.10)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3(a)(4))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

The cash outflow to purchase long lived physical asset for use in the normal oil and gas operations and to purchase mineral interests in oil and gas properties not intended for resale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireOilAndGasPropertyAndEquipment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash inflow to dispose of long-lived, physical assets and mineral interests in oil and gas properties used for normal oil and gas operations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3179-108585

+ Details

Name:	us-gaap_ProceedsFromSaleOfOilAndGasPropertyAndEquipment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	srt_StatementGeographicalAxis=brn_TwiningMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=brn_RedEarthMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=brn_StolbergMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=brn_MiscellaneousOilAndNaturalGasPropertiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=brn_ProgressandValhallaJune2017Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=brn_SpiritRiver2017Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=brn_PurchaseandSaleAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=brn_BarnwellIndustriesIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

OIL AND NATURAL GAS PROPERTIES (Details)	1 Months Ended	12 Months Ended
OIL AND NATURAL GAS PROPERTIES (Details)	Feb. 28, 2018 USD ($) party	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Jul. 31, 2018 USD ($)
Oil and natural gas properties
ARO assumed		$ 3,085,000	$ 34,000
Proceeds from sale of oil and natural gas assets		848,000	619,000
Income taxes receivable		2,461,000	1,145,000
Gain (loss) on disposition of oil and natural gas properties		2,255,000	0
Liabilities associated with properties sold		1,855,000	406,000
Payments to acquire oil and natural gas properties		10,362,000	381,000
Twining
Oil and natural gas properties
ARO assumed		3,076,000
Red Earth
Oil and natural gas properties
Sale of oil and gas property and equipment, number of separate independent third parties \| party	2
Proceeds from sale of oil and natural gas assets	$ 1,367,000
Income taxes receivable	$ 752,000
Percent difference in capitalized costs divided by proved reserves if the gain is recorded as opposed to being credited against the full-cost pool	322.00%
Gain (loss) on disposition of oil and natural gas properties		2,140,000
Stolberg
Oil and natural gas properties
Proceeds from sale of oil and natural gas assets		118,000
Gain (loss) on disposition of oil and natural gas properties		115,000
Miscellaneous Oil And Natural Gas Properties
Oil and natural gas properties
Proceeds from sale of oil and natural gas assets		221,000	208,000
Income taxes receivable		106,000	$ 72,000
Gain (loss) on disposition of oil and natural gas properties		0
Progress and Valhalla June 2017
Oil and natural gas properties
Proceeds from sale of oil and natural gas assets		1,076,000
Income taxes receivable		593,000
Spirit River 2017
Oil and natural gas properties
Payments to acquire oil and natural gas properties		$ 381,000
Purchase and Sale Agreement \| Barnwell Industries Inc \| Twining
Oil and natural gas properties
Collaborative Agreement, purchase price				$ 10,362,000
Purchase and Sale Agreement \| Barnwell Industries Inc \| Red Earth
Oil and natural gas properties
Liabilities associated with properties sold	$ 1,666,000