Amount of increase (decrease) in accrual for contingency matter.

No definition available.

Name:	bstg_IncreaseDecreaseInAccrualForContingencyMatter
Namespace Prefix:	bstg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Number of bioreactors.

+ References

No definition available.

+ Details

Name:	bstg_NumberOfBioreactors
Namespace Prefix:	bstg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of Synthetic Trachea Scaffold product.

+ References

No definition available.

+ Details

Name:	bstg_NumberOfSyntheticTracheaScaffoldProduct
Namespace Prefix:	bstg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of litigation expense, including but not limited to legal, forensic, accounting, and investigative fees.

+ References

No definition available.

+ Details

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

- 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_LossContingenciesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of receivable related to a loss contingency accrual. For example, an insurance recovery receivable.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=124440162&loc=d3e12053-110248

+ Details

Name:	us-gaap_LossContingencyReceivable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of cash inflow from the collection of receivables related to a loss contingency.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=124440162&loc=d3e12053-110248

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 17
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3367-108585

+ Details

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

- Details

Name:	srt_LitigationCaseAxis=bstg_MedmarcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Commitments and Contingencies (Details) $ in Thousands		3 Months Ended	12 Months Ended
Commitments and Contingencies (Details) $ in Thousands	Mar. 03, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Jan. 25, 2022 USD ($)	Apr. 14, 2017 item
Loss Contingencies [Line Items]
Number of Synthetic Trachea Scaffold product \| item						1
Number of bioreactors \| item						2
Accrual for contingency matter			$ 3,250	$ 0
Medmarc
Loss Contingencies [Line Items]
Legal costs on claims against insurance carrier		$ 1,400
Reimbursement of legal costs					$ 1,000
Cash payment received on litigation	$ 100