ORGANIZATION AND DESCRIPTION OF BUSINESS (Details)	Apr. 07, 2014 Country	Jun. 30, 2014 Eurasian and African Countries [Member] Country
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of EU countries in which marketing rights of XIAPEX held	28	71

Represents number of EU countries in which marketing rights of XIAPEX held by Swedish Orphan Biovitrum AB ("Sobi").

No definition available.

Name:	bstc_NumberOfEuCountriesInWhichMarketingRightsOfXiapexHeld
Namespace Prefix:	bstc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant