S000002882 [Member] Investment Objectives and Goals - BlackRock Basic Value V.I. Fund	Dec. 31, 2025
Prospectus [Line Items]
Risk/Return [Heading]	Fund Overview Key Facts About BlackRock Basic Value V.I. Fund
Objective [Heading]	Investment Objective
Objective, Primary [Text Block]	The investment objective of BlackRock Basic Value V.I. Fund (the “Fund”) is to seek capital appreciation
Objective, Secondary [Text Block]	and, secondarily, income.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form N-1A
-Section 2
-Subsection a

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form N-1A
-Section 2
-Subsection a

Name:	oef_ObjectivePrimaryTextBlock
Namespace Prefix:	oef_
Data Type:	dtr-types:textBlockItemType
Balance Type:	na
Period Type:	duration

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form N-1A
-Section 2
-Subsection a

Name:	oef_ObjectiveSecondaryTextBlock
Namespace Prefix:	oef_
Data Type:	dtr-types:textBlockItemType
Balance Type:	na
Period Type:	duration

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form N-1A
-Section 1
-Subsection a

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Section 2
-Name Form N-1A
-Subsection a

Name:	dei_LegalEntityAxis=bvsf_S000002882Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: