Represents information pertaining to the increase in the fair value of the derivative liability.

No definition available.

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- Definition

Represents the amount of milestone payment to be paid by the company upon the achievement of specified commercial milestones and annual royalty payments based on net sales of products from patents.

+ References

No definition available.

+ Details

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- Definition

Represents the amount of milestone payment to be paid by the company upon the achievement of specified regulatory milestones and annual royalty payments based on net sales of products from patents.

+ References

No definition available.

+ Details

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- Definition

Represents the amount of milestone payment to be paid by the company upon the achievement of specified regulatory milestones and annual royalty payments based on net sales of products from patents other than the specified product.

+ References

No definition available.

+ Details

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- Definition

Represents the number of licensed products using the patent rights licensed from BMS.

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
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Period Type:	duration

- Definition

Represents information pertaining to other expenses recorded for the change in the fair value of the derivative liability.

+ References

No definition available.

+ Details

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Namespace Prefix:	bhvn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

Represents information pertaining to the right of BMS to purchase fully diluted shares as a percentage.

+ References

No definition available.

+ Details

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Namespace Prefix:	bhvn_
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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.

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Balance Type:	na
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- Definition

This element represents the aggregate cost of investments accounted for under the equity method of accounting.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

The cash inflow from issuance of preferred stocks identified as being convertible into another form of financial instrument, typically the entity's common stock.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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- Definition

The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

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- Definition

Price of a single share of a number of saleable stocks of a company.

+ References

No definition available.

+ Details

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Balance Type:	na
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- Definition

Number of new stock issued during the period.

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- Definition

Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.

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License Agreements - BMS Agreement (Details) $ / shares in Units, $ in Thousands	1 Months Ended			3 Months Ended
	May 31, 2017 shares	Jul. 31, 2016 USD ($) item $ / shares	Feb. 29, 2016 $ / shares shares	Mar. 31, 2017 USD ($)	Jul. 31, 2016 USD ($) $ / shares shares	Mar. 31, 2016 USD ($)
License agreements
Net proceeds				$ 40,000
Fair value of common share \| $ / shares		$ 7.70	$ 7.00		$ 7.70
Issuance of common shares \| shares			429,000		1,090,500
Research and development				10,740		$ 2,370
BMS Agreement \| Product related collaborative arrangements
License agreements
Common shares value issued		$ 12,500
Fair value of common share \| $ / shares		$ 9.2911			$ 9.2911
Other expense for change in the fair value of the derivative liability				1,875
Increase in the fair value of the liability		$ 15,938			$ 15,938
Issuance of common shares \| shares	1,345,374
Research and development				$ 0
BMS Agreement \| Product related collaborative arrangements \| Maximum
License agreements
Milestone payment to be paid		127,500
Milestone payment to be paid for any product other than rimegepant		74,500
Commercial milestone payment to be paid		$ 150,000
Right to purchase shares fully diluted (as a percent)		8			8
BMS Agreement \| Product related collaborative arrangements \| Minimum
License agreements
Number of licensed products \| item		1
Net proceeds		$ 30,000
Minimum investment in equity		$ 22,000			$ 22,000