Debt instrument interest only payment term.

No definition available.

Name:	bdsi_DebtInstrumentInterestOnlyPaymentTerm
Namespace Prefix:	bdsi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt instrument interest only payment term threshold.

+ References

No definition available.

+ Details

Name:	bdsi_DebtInstrumentInterestOnlyPaymentTermThreshold
Namespace Prefix:	bdsi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt instrument interest rate stated interest only period percentage.

+ References

No definition available.

+ Details

Name:	bdsi_DebtInstrumentInterestRateStatedInterestOnlyPeriodPercentage
Namespace Prefix:	bdsi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt instrument prepayment fee after year five.

+ References

No definition available.

+ Details

Name:	bdsi_DebtInstrumentPrepaymentFeeAfterYearFive
Namespace Prefix:	bdsi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Deferred loan costs expensed.

+ References

No definition available.

+ Details

Name:	bdsi_DeferredLoanCostsExpensed
Namespace Prefix:	bdsi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Final payment fees percentage.

+ References

No definition available.

+ Details

Name:	bdsi_FinalPaymentFeesPercentage
Namespace Prefix:	bdsi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

License termination effective date.

+ References

No definition available.

+ Details

Name:	bdsi_LicenseTerminationEffectiveDate
Namespace Prefix:	bdsi_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility additional borrowing capacity upon contingent milestone achievement.

+ References

No definition available.

+ Details

Name:	bdsi_LineOfCreditFacilityAdditionalBorrowingCapacityUponContingentMilestoneAchievement
Namespace Prefix:	bdsi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line of credit facility second draw borrowing capacity upon contingent milestone achievement.

+ References

No definition available.

+ Details

Name:	bdsi_LineOfCreditFacilitySecondDrawBorrowingCapacityUponContingentMilestoneAchievement
Namespace Prefix:	bdsi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Prepayment period of outstanding principal and accrued unpaid interest.

+ References

No definition available.

+ Details

Name:	bdsi_PrepaymentPeriodOfOutstandingPrincipalAndAccruedUnpaidInterest
Namespace Prefix:	bdsi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
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_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3255-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

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

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=bdsi_CRGServicingLLCAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bdsi_TrancheOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bdsi_TrancheTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=bdsi_MidCapFinancialTrustMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_SecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_InterestExpenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Notes Payable - Additional Information (Detail) - USD ($)			3 Months Ended
	Dec. 26, 2017	Feb. 21, 2017	Mar. 31, 2018	Mar. 31, 2017
CRG [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
License termination effective date			Feb. 21, 2017
Borrowings outstanding		$ 45,000,000
Additional borrowing capacity upon milestone achievement		30,000,000
Second draw borrowing capacity upon milestone achievement		$ 5,000,000
Loan agreement term		6 years
Loan agreement interest only term		3 years
Loan agreement interest only term threshold		4 years
Agreement maturity date		Dec. 31, 2022
Interest on borrowings		12.50%
Interest on borrowings, interest only period percentage		3.50%
Effective interest on borrowings		9.00%
Final payment fee rate		9.00%
Prepayment period of outstanding principal and accrued unpaid interest		5 years
Prepayment fee after		$ 0
CRG [Member] \| Tranche One [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Additional borrowing capacity upon milestone achievement		15,000,000
CRG [Member] \| Tranche Two [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Second draw gross proceeds	$ 15,000,000
Additional borrowing capacity upon milestone achievement		15,000,000
MidCap Financial Trust [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Second draw gross proceeds		$ 29,400,000
MidCap Financial Trust [Member] \| Secured Debt [Member] \| Interest Expense [Member]
Debt Instrument [Line Items]
Deferred loan costs expensed				$ 700,000