Stock Issued During Period, Shares, Warrants Exercised

No definition available.

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

- Definition

Exercise price per share or per unit of warrants or rights outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

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

- 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_ClassOfWarrantOrRightLineItems
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Balance Type:	na
Period Type:	duration

- Definition

Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares.

+ References

+ Details

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

- Definition

Number of warrants or rights outstanding.

+ References

No definition available.

+ Details

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

- Definition

The cash inflow associated with the amount received from holders exercising their stock warrants.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3255-108585

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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Namespace Prefix:
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- Details

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Period Type:

WARRANTS - Warrants to Purchase Series D Preferred Stock (Details) - USD ($)			6 Months Ended
	Nov. 12, 2020	Nov. 07, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2019	Jun. 12, 2018
Class of Warrant or Right [Line Items]
Warrants to purchase shares (in shares)			19,933,333
Exercise price of warrants (in dollars per share)			$ 11.50
Proceeds from warrant exercise			$ 4,823,000	$ 0
Warrants to purchase shares (in shares)			19,400,000
Series D, Penny warrants
Class of Warrant or Right [Line Items]
Warrants to purchase shares (in shares)						485,262
Exercise price of warrants (in dollars per share)						$ 0.006
Shares exercised and issued (in shares)	485,262
Proceeds from warrant exercise	$ 3,000.0
Warrants to purchase shares (in shares)			0
Series E Warrants
Class of Warrant or Right [Line Items]
Warrants to purchase shares (in shares)				121,356	242,713
Exercise price of warrants (in dollars per share)				$ 5.92
Shares exercised and issued (in shares)		364,069
Proceeds from warrant exercise		$ 2,200,000
Warrants to purchase shares (in shares)			0