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Consolidated Statements of Comprehensive Loss (Parentheticals) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Research and development expense, patent cost | $ 42,259 |  |

X
- Definition Represents the amount of research and development expense related to patent acquired settled by shares issuance. + References No definition available. + Details
Name: | bysi_ResearchAndDevelopmentExpensesSettledBySharesIssuance
Namespace Prefix: | bysi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration