3.21.1 html 6 170 1 false 5 0 false 2 false false R1.htm 0001 - Document - Document and Entity Information {Elements} Sheet http://www.elfun.com/role/DocumentAndEntityInformationElements Document and Entity Information 1 false true R2.htm 0002 - Document - Risk/Return Summary {Unlabeled} - ELFUN TRUSTS Sheet http://www.elfun.com/role/RiskReturnSummaryUnlabeledElfunTrusts Risk/Return Summary- ELFUN TRUSTS 2 false false R9.htm 0009 - Disclosure - Risk/Return Detail Data {Elements} - ELFUN TRUSTS Sheet http://www.elfun.com/role/RiskReturnDetailDataElementsElfunTrusts Risk/Return Detail Data- ELFUN TRUSTS 3 false false R10.htm 040000 - Disclosure - Risk/Return Detail Data {Elements} Sheet http://xbrl.sec.gov/rr/role/RiskReturnDetailData Risk/Return Detail Data 4 false false All Reports Book All Reports d107734d485bpos.htm d107734dex9928g2.htm d107734dex9928j.htm d107734dex9928p1.htm d107734dex9928q4.htm elfun-20201231.xsd elfun-20201231_cal.xml elfun-20201231_def.xml elfun-20201231_lab.xml elfun-20201231_pre.xml g107734g1elfundiversified.jpg g107734g1elfungovtmm.jpg g107734g1elfunincome.jpg g107734g1elfuninternationale.jpg g107734g1elfuntaxexempt.jpg g107734g1elfuntrusts.jpg g107734g1ssga_hor.jpg g117450g75m56.jpg g125283g75m56.jpg BarChart1.png http://xbrl.sec.gov/rr/2018-01-31 http://xbrl.sec.gov/dei/2020-01-31 true true