Derivative Financial Instruments - Reconciliation of Beginning and Ending Balances of Assets and Liabilities Measured at Fair Value Using Significant Observable Inputs (Detail) (Midcap warrant [Member], Level 2 [Member], USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Midcap warrant [Member] \| Level 2 [Member]
Fair Value Measurement Inputs Disclosure [Line Items]
Warrant asset, Beginning balance		$ 50
Increase (decrease) in fair value of warrants	0
Increase (decrease) in fair value of warrants, Number of warrants
Decrease due to exercise of warrants, assets		(50)
Warrant asset, Ending balance
Warrant liability, Beginning balance	4,315	4,498
Decrease due to exercise of warrants	(17,482)	(11)
Increase (decrease) in fair value of warrants	13,167	(172)
Warrant liability, Ending balance		$ 4,315
Warrant asset, Beginning balance, Number of warrants		2,000,000
Decrease due to exercise of warrants, assets, Number of warrants		(2,000,000)
Warrant asset, Ending balance, Number of warrants
Warrant liability, Beginning balance, Number of warrants	1,999,437	2,009,437
Decrease due to exercise of warrants, liabilities, Number of warrants	(1,999,153)	(10,000)
Increase (decrease) in fair value of warrants, Number of warrants
Warrant liability, Ending balance, Number of warrants	284	1,999,437

Derivative Financial Instruments - Reconciliation of Beginning and Ending Balances of Assets and Liabilities Measured at Fair Value Using Significant Observable Inputs (Detail) (Midcap warrant [Member], Level 2 [Member], USD $)

12 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Midcap warrant [Member] | Level 2 [Member]

Fair Value Measurement Inputs Disclosure [Line Items]

Warrant asset, Beginning balance

$ 50us-gaap_DerivativeAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancialInstrumentAxis
= us-gaap_WarrantMember

Increase (decrease) in fair value of warrants

0us-gaap_IncreaseDecreaseInDerivativeAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancialInstrumentAxis
= us-gaap_WarrantMember

Increase (decrease) in fair value of warrants, Number of warrants

Decrease due to exercise of warrants, assets

(50)bdsi_DerivativeAssetsDecreaseDueToWarrantExercised
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancialInstrumentAxis
= us-gaap_WarrantMember

Warrant asset, Ending balance

Warrant liability, Beginning balance

4,315us-gaap_DerivativeLiabilities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancialInstrumentAxis
= us-gaap_WarrantMember

4,498us-gaap_DerivativeLiabilities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancialInstrumentAxis
= us-gaap_WarrantMember

Decrease due to exercise of warrants

(17,482)bdsi_DerivativeLiabilityDecreaseDueToWarrantExercised
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancialInstrumentAxis
= us-gaap_WarrantMember

(11)bdsi_DerivativeLiabilityDecreaseDueToWarrantExercised
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancialInstrumentAxis
= us-gaap_WarrantMember

Increase (decrease) in fair value of warrants

13,167us-gaap_IncreaseDecreaseInDerivativeLiabilities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancialInstrumentAxis
= us-gaap_WarrantMember

(172)us-gaap_IncreaseDecreaseInDerivativeLiabilities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancialInstrumentAxis
= us-gaap_WarrantMember

Warrant liability, Ending balance

$ 4,315us-gaap_DerivativeLiabilities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancialInstrumentAxis
= us-gaap_WarrantMember

Warrant asset, Beginning balance, Number of warrants

2,000,000bdsi_NumberOfDerivativeAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancialInstrumentAxis
= us-gaap_WarrantMember

Decrease due to exercise of warrants, assets, Number of warrants

(2,000,000)bdsi_NumberOfDerivativeAssetsDecreaseDueToWarrantExercised
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancialInstrumentAxis
= us-gaap_WarrantMember

Warrant asset, Ending balance, Number of warrants

Warrant liability, Beginning balance, Number of warrants

1,999,437bdsi_NumberOfDerivativeLiability
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancialInstrumentAxis
= us-gaap_WarrantMember

2,009,437bdsi_NumberOfDerivativeLiability
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancialInstrumentAxis
= us-gaap_WarrantMember

Decrease due to exercise of warrants, liabilities, Number of warrants

(1,999,153)bdsi_NumberOfDerivativeLiabilityDecreaseDueToWarrantExercised
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancialInstrumentAxis
= us-gaap_WarrantMember

(10,000)bdsi_NumberOfDerivativeLiabilityDecreaseDueToWarrantExercised
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancialInstrumentAxis
= us-gaap_WarrantMember

Increase (decrease) in fair value of warrants, Number of warrants

Warrant liability, Ending balance, Number of warrants

284bdsi_NumberOfDerivativeLiability
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancialInstrumentAxis
= us-gaap_WarrantMember

1,999,437bdsi_NumberOfDerivativeLiability
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancialInstrumentAxis
= us-gaap_WarrantMember

- Definition

Derivative Assets Decrease Due To Warrant Exercised

+ References

No definition available.

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Namespace Prefix:	bdsi_
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Balance Type:	credit
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- Definition

Derivative liability decrease due to warrant exercised.

+ References

No definition available.

+ Details

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- Details

Name:	bdsi_FairValueMeasurementInputsDisclosureLineItems
Namespace Prefix:	bdsi_
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Balance Type:	na
Period Type:	duration

- Definition

Increase decrease in number derivative assets.

+ References

No definition available.

+ Details

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

- Definition

Increase decrease in number derivative liability.

+ References

No definition available.

+ Details

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Namespace Prefix:	bdsi_
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- Definition

Number of derivative assets

+ References

No definition available.

+ Details

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Balance Type:	na
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- Definition

Number Of Derivative Assets Decrease Due To Warrant Exercised

+ References

No definition available.

+ Details

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Namespace Prefix:	bdsi_
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- Definition

Number of derivative liability

+ References

No definition available.

+ Details

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Namespace Prefix:	bdsi_
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Balance Type:	na
Period Type:	instant

- Definition

Number of derivative liability decrease due to warrant exercised.

+ References

No definition available.

+ Details

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Namespace Prefix:	bdsi_
Data Type:	xbrli:sharesItemType
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- Definition

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13433-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13495-108611

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=34720828&loc=SL20225862-175312

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 55

-Paragraph 10

-URI http://asc.fasb.org/extlink&oid=36459792&loc=SL20226008-175313

+ Details

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- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

+ Details

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

- Definition

The increase (decrease) during the period in the carrying value of derivative instruments reported as assets that are due to be disposed of within one year (or the normal operating cycle, if longer).

+ References

No definition available.

+ Details

Name:	us-gaap_IncreaseDecreaseInDerivativeAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The increase (decrease) during the period in the carrying value of derivative instruments reported as liabilities that are due to be disposed of within one year (or the normal operating cycle, if longer).

+ References

No definition available.

+ Details

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