Annual percentage increase for rent.

No definition available.

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Namespace Prefix:	obas_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Deduction from the gross amount.

+ References

No definition available.

+ Details

Name:	obas_DeductionFromGrossAmount
Namespace Prefix:	obas_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of monthly consulting fee in consideration for services.

+ References

No definition available.

+ Details

Name:	obas_MonthlyConsultingFeeInConsiderationForServices
Namespace Prefix:	obas_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Monthly rent payment for property leased from related party.

+ References

No definition available.

+ Details

Name:	obas_MonthlyRentPaymentForPropertyLeasedFromRelatedParty
Namespace Prefix:	obas_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Ownership percentage stated as a percentage of the outstanding share capital owned.

+ References

No definition available.

+ Details

Name:	obas_OwnershipPercentageOutstandingShareCapital
Namespace Prefix:	obas_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount of reimbursement of health insurance expenses to CEO as a part of compensation terms.

+ References

No definition available.

+ Details

Name:	obas_ReimbursementOfAnnualHealthInsuranceExpenses
Namespace Prefix:	obas_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of reimbursement of reasonable work-related expenses to CEO as a part of compensation terms.

+ References

No definition available.

+ Details

Name:	obas_ReimbursementOfAnnualReasonableWorkRelatedExpenses
Namespace Prefix:	obas_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Duration of an agreement or transaction with a related party.

+ References

No definition available.

+ Details

Name:	obas_RelatedPartyTransactionDuration
Namespace Prefix:	obas_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Remaining loan amount.

+ References

No definition available.

+ Details

Name:	obas_RemainingLoanAmount
Namespace Prefix:	obas_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Reserve from transaction with controlling shareholder.

+ References

No definition available.

+ Details

Name:	obas_ReserveFromTransactionWithControllingShareholder
Namespace Prefix:	obas_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents interest incurred for borrowed money which was used to produce goods or render services.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2)
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

+ Details

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

- Definition

Describe the approximate term of the guarantee or each group of similar guarantees.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=115931803&loc=d3e12069-110248

+ Details

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

- Definition

Amount of expense for salary and wage arising from service rendered by officer. Excludes allocated cost, labor-related nonsalary expense, and direct and overhead labor cost included in cost of good and service sold.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(4))
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

+ Details

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

- Definition

The cash inflow from a long-term borrowing made from related parties where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth. Alternate caption: Proceeds from Advances from Affiliates.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3255-108585

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3291-108585

+ Details

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

- Definition

Number of shares of stock issued during the period as part of a transaction to acquire assets that do not qualify as a business combination.

+ References

No definition available.

+ Details

Name:	us-gaap_StockIssuedDuringPeriodSharesPurchaseOfAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=obas_FlamingoSouthBeachCondominiumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=srt_AffiliatedEntityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_MajorityShareholderMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_FinancialGuaranteeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_DirectorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=obas_ControllingShareholderMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_ChiefExecutiveOfficerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidatedEntitiesAxis=srt_SubsidiariesMember
Namespace Prefix:
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MAJOR SHAREHOLDERS AND RELATED PARTY TRANSACTIONS (Details) € in Thousands, $ in Thousands				1 Months Ended		12 Months Ended
	May 16, 2016 USD ($)	Dec. 19, 2013 USD ($)	Dec. 19, 2013 EUR (€)	Feb. 14, 2019 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013 shares
Related Party Transaction [Line Items]
Proceeds from related party guarantee							$ 5,118
Shares issued for real estate investment \| shares										1,300,580
Deduction from the gross amount						$ 142
Finance expense						133
Flamingo South Beach Condominium [Member]
Related Party Transaction [Line Items]
Time period									3 years
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Monthly rent payment for property leased from related party						$ 25
Annual percentage increase for rent						3.00%
Majority Shareholder [Member]
Related Party Transaction [Line Items]
Ownership percentage						73.00%
Majority Shareholder [Member] \| Financial Guarantee [Member]
Related Party Transaction [Line Items]
Term of loan guarantee								3 years
Director [Member]
Related Party Transaction [Line Items]
Reimbursement of reasonable work-related expenses \| €			€ 12
Director [Member] \| Maximum [Member]
Related Party Transaction [Line Items]
Monthly consulting fee \| €			€ 4
Controlling Shareholder [Member]
Related Party Transaction [Line Items]
Proceeds from related party guarantee					$ 5,118
Maturity date					Apr. 01, 2020
Reserve from transaction with controlling shareholder					$ 372
Repayment of loan					2,500
Remaining loan amount					$ 2,600
Chief Executive Officer [Member] \| Subsidiaries [Member]
Related Party Transaction [Line Items]
Salary to CEO	$ 200	$ 170		$ 220,000
Chief Executive Officer [Member] \| Maximum [Member] \| Subsidiaries [Member]
Related Party Transaction [Line Items]
Reimbursement of health insurance expenses	24	24
Reimbursement of reasonable work-related expenses	$ 50	$ 50