Number of directors to whom the Company agreed to issue warrants to purchase common shares.

No definition available.

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Namespace Prefix:	bhvn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(i)(4))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

Name:	us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- 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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(i)(2))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
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

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Balance Type:	na
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- Details

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Namespace Prefix:
Data Type:	na
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- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=srt_DirectorMember
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Related Party Transactions - Narrative (Details)	Jan. 26, 2017 director $ / shares shares	Mar. 31, 2019 $ / shares shares
Guarantor and Co-Guarantor Warrants
Related Party Transactions
Number of securities called by warrants (shares) \| shares		107,500
Exercise price of warrants (in dollars per share) \| $ / shares		$ 9,291.1000
Directors
Related Party Transactions
Number of directors to whom the Company agreed to issue warrants \| director	2
Directors \| Guarantor and Co-Guarantor Warrants
Related Party Transactions
Number of securities called by warrants (shares) \| shares	107,500
Exercise price of warrants (in dollars per share) \| $ / shares	$ 9.2911