Represents annual incentive earned.

No definition available.

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Namespace Prefix:	bcrx_
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Period Type:	instant

- Definition

Represents the value of equity to be issued.

+ References

No definition available.

+ Details

Name:	bcrx_CommonStockToBeIssuedValue
Namespace Prefix:	bcrx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the maximum aggregate offering price of common stock, preferred stock, depository shares, stock purchase contracts, warrants and units.

+ References

No definition available.

+ Details

Name:	bcrx_MaximumAggregateOfferingPrice
Namespace Prefix:	bcrx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents stock issued during period shares for over allotment option exercised by underwriter.

+ References

No definition available.

+ Details

Name:	bcrx_StockIssuedDuringPeriodSharesForOverAllotmentOptionExercisedByUnderwriter
Namespace Prefix:	bcrx_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Aggregate par or stated value of issued nonredeemable common stock (or common stock redeemable solely at the option of the issuer). This item includes treasury stock repurchased by the entity. Note: elements for number of nonredeemable common shares, par value and other disclosure concepts are in another section within stockholders' equity.

+ 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 210.5-02.29)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 30

-Article 5

+ Details

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

- Definition

The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4297-108586

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 25

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3536-108585

+ Details

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

- Definition

The cash inflow from the additional capital contribution to the entity.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 14

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585

+ Details

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

- Definition

The total cash inflow associated with the amount received from holders to acquire the entity's shares under incentive and share awards, including stock option exercises. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately.

+ References

+ Details

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

- Definition

The cash inflow from the issuance of common stock, preferred stock, treasury stock, stock options, and other types of equity.

+ References

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

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

- Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares of capital stock issued (purchased by employees) in connection with an employee stock ownership plan.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30

-Article 5

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 40

-Section 25

-Paragraph 10

-URI http://asc.fasb.org/extlink&oid=6418455&loc=d3e16649-113920

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- Definition

Number of new stock issued during the period.

+ References

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Note 5 - Stockholders' Equity (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	1 Months Ended	0 Months Ended	1 Months Ended	12 Months Ended
	Jun. 30, 2014	Mar. 15, 2012	Aug. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Nov. 06, 2013	Jul. 13, 2011
Stockholders' Equity Note [Abstract]
Maximum Aggregate Offering Price							$ 125,000bcrx_MaximumAggregateOfferingPrice
Stock Issued During Period, Shares, New Issues (in Shares)	11,500		4,600		2,883	4,516
Proceeds from Issuance of Common Stock	115,000		18,500	106,600	23,633	17,805
Proceeds from Issuance or Sale of Equity	106,600
Share Price (in Dollars per share)		$ 5.23us-gaap_SharePrice	$ 4.40us-gaap_SharePrice		$ 1.85us-gaap_SharePrice	$ 4.08us-gaap_SharePrice
Stock Issued During Period, Shares for Over Allotment Option Exercised by Underwriter (in Shares)			600
Common Stock To Be Issued, Value	70,000bcrx_CommonStockToBeIssuedValue
Common Stock, Value, Issued				720us-gaap_CommonStockValue	591us-gaap_CommonStockValue			70,000us-gaap_CommonStockValue
Proceeds from Issuance of Shares under Incentive and Share-based Compensation Plans, Including Stock Options					5,218
Stock Issued During Period, Shares, Employee Stock Ownership Plan (in Shares)		193
Annual Incentive Earned		1,542bcrx_AnnualIncentiveEarned
Income Taxes Paid		$ 535us-gaap_IncomeTaxesPaid