3.21.4 html 13 189 1 true 10 0 false 2 false false R1.htm 000000 - Document - Document and Entity Information {Elements} Sheet http://www.blackrock.com/role/DocumentDocumentandEntityInformationElements000000 Document and Entity Information 1 false false R2.htm 000021 - Disclosure - Risk/Return Detail Data {Elements} - BLACKROCK ADVANTAGE SMALL CAP GROWTH FUND (Investor A, Institutional and Class R) Sheet http://www.blackrock.com/role/DisclosureRiskReturnDetailDataElementsBLACKROCKADVANTAGESMALLCAPGROWTHFUNDInvestorAInstitutionalandClassR Risk/Return Detail Data- BLACKROCK ADVANTAGE SMALL CAP GROWTH FUND (Investor A, Institutional and Class R) 2 false false R3.htm 000041 - Disclosure - Risk/Return Detail Data {Elements} - BLACKROCK ADVANTAGE SMALL CAP GROWTH FUND (Class K) Sheet http://www.blackrock.com/role/DisclosureRiskReturnDetailDataElementsBLACKROCKADVANTAGESMALLCAPGROWTHFUNDClassK000041 Risk/Return Detail Data- BLACKROCK ADVANTAGE SMALL CAP GROWTH FUND (Class K) 3 false false All Reports Book All Reports d284514d485bpos.htm bf1-20220126.xsd bf1-20220126_cal.xml bf1-20220126_def.xml bf1-20220126_lab.xml bf1-20220126_pre.xml d284514dex9910a.htm g284514bar.jpg g284514c000004049_dgf.jpg g284514g1bar.jpg g284514g1c000198224_dgf.jpg g284514g1img918ff7a01.gif g284514img25dc45b31.gif http://xbrl.sec.gov/dei/2021 http://xbrl.sec.gov/rr/2021 true true