Name:	open_BusinessCombinationConsiderationBaseForCalculation
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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Represents the number of shares converted from each share from a class of shares held by the company upon merger under the merger agreement.

No definition available.

Name:	open_CommonStockConversionBasisNumberOfSharesConverted
Namespace Prefix:	open_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

It represents Aggregate carrying value as of the balance sheet date of the liabilities for deferred underwriting fees.

No definition available.

Name:	open_DeferredUnderwritingFees
Namespace Prefix:	open_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents deferred underwriting fees (in dollars per share).

No definition available.

Name:	open_DeferredUnderwritingFeesInDollarsPerShare
Namespace Prefix:	open_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

Represents refunds from deferred underwriting discount.

No definition available.

Name:	open_RefundsFromDeferredUnderwritingDiscount
Namespace Prefix:	open_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The refund received from the underwriting discount paid related to public offering.

No definition available.

Name:	open_RefundsFromUnderwritingDiscount
Namespace Prefix:	open_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The percentage of underwriting discount expended related to public offering during the period.

No definition available.

Name:	open_UnderwritingDiscountPercentage
Namespace Prefix:	open_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Price of a single share of a number of saleable stocks paid or offered to be paid in a business combination.

No definition available.

Name:	us-gaap_BusinessAcquisitionSharePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

Number of securities into which each warrant or right may be converted. For example, but not limited to, each warrant may be converted into two shares.

No definition available.

Name:	us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Face amount or stated value per share of common stock.

Reference 1: 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(29))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

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Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassBMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_WarrantMember
Namespace Prefix:
Data Type:	na
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