3.20.4 html 113 188 1 true 99 0 false 2 false false R1.htm 000001 - Document - Document and Entity Information Sheet http://www.MFS.com/20201228/role/DocumentAndEntityInformation Document and Entity Information 1 false true R2.htm 020000 - Document - Risk/Return Summary {Unlabeled} - MFS?? Core Equity Fund Sheet http://www.MFS.com/20201228/role/DocumentRiskReturnSummaryUnlabeledMFSCoreEquityFund Risk/Return Summary- MFS?? Core Equity Fund 2 false false R9.htm 020007 - Disclosure - Risk/Return Detail Data {Elements} - MFS?? Core Equity Fund Sheet http://www.MFS.com/20201228/role/DisclosureRiskReturnDetailDataElementsMFSCoreEquityFund Risk/Return Detail Data- MFS?? Core Equity Fund 3 false true R10.htm 020008 - Document - Risk/Return Summary {Unlabeled} - MFS?? Low Volatility Equity Fund Sheet http://www.MFS.com/20201228/role/DocumentRiskReturnSummaryUnlabeledMFSLowVolatilityEquityFund Risk/Return Summary- MFS?? Low Volatility Equity Fund 4 false false R17.htm 020015 - Disclosure - Risk/Return Detail Data {Elements} - MFS?? Low Volatility Equity Fund Sheet http://www.MFS.com/20201228/role/DisclosureRiskReturnDetailDataElementsMFSLowVolatilityEquityFund Risk/Return Detail Data- MFS?? Low Volatility Equity Fund 5 false true R18.htm 020016 - Document - Risk/Return Summary {Unlabeled} - MFS?? Low Volatility Global Equity Fund Sheet http://www.MFS.com/20201228/role/DocumentRiskReturnSummaryUnlabeledMFSLowVolatilityGlobalEquityFund Risk/Return Summary- MFS?? Low Volatility Global Equity Fund 6 false false R25.htm 020023 - Disclosure - Risk/Return Detail Data {Elements} - MFS?? Low Volatility Global Equity Fund Sheet http://www.MFS.com/20201228/role/DisclosureRiskReturnDetailDataElementsMFSLowVolatilityGlobalEquityFund Risk/Return Detail Data- MFS?? Low Volatility Global Equity Fund 7 false true R26.htm 020024 - Document - Risk/Return Summary {Unlabeled} - MFS?? New Discovery Fund Sheet http://www.MFS.com/20201228/role/DocumentRiskReturnSummaryUnlabeledMFSNewDiscoveryFund Risk/Return Summary- MFS?? New Discovery Fund 8 false false R33.htm 020031 - Disclosure - Risk/Return Detail Data {Elements} - MFS?? New Discovery Fund Sheet http://www.MFS.com/20201228/role/DisclosureRiskReturnDetailDataElementsMFSNewDiscoveryFund Risk/Return Detail Data- MFS?? New Discovery Fund 9 false true R34.htm 020032 - Document - Risk/Return Summary {Unlabeled} - MFS?? Research International Fund Sheet http://www.MFS.com/20201228/role/DocumentRiskReturnSummaryUnlabeledMFSResearchInternationalFund Risk/Return Summary- MFS?? Research International Fund 10 false false R41.htm 020039 - Disclosure - Risk/Return Detail Data {Elements} - MFS?? Research International Fund Sheet http://www.MFS.com/20201228/role/DisclosureRiskReturnDetailDataElementsMFSResearchInternationalFund Risk/Return Detail Data- MFS?? Research International Fund 11 false true R42.htm 020040 - Document - Risk/Return Summary {Unlabeled} - MFS?? Technology Fund Sheet http://www.MFS.com/20201228/role/DocumentRiskReturnSummaryUnlabeledMFSTechnologyFund Risk/Return Summary- MFS?? Technology Fund 12 false false R49.htm 020047 - Disclosure - Risk/Return Detail Data {Elements} - MFS?? Technology Fund Sheet http://www.MFS.com/20201228/role/DisclosureRiskReturnDetailDataElementsMFSTechnologyFund Risk/Return Detail Data- MFS?? Technology Fund 13 false true R50.htm 020048 - Document - Risk/Return Summary {Unlabeled} - MFS?? U.S. Government Cash Reserve Fund Sheet http://www.MFS.com/20201228/role/DocumentRiskReturnSummaryUnlabeledMFSUSGovernmentCashReserveFund Risk/Return Summary- MFS?? U.S. Government Cash Reserve Fund 14 false false R57.htm 020055 - Disclosure - Risk/Return Detail Data {Elements} - MFS?? U.S. Government Cash Reserve Fund Sheet http://www.MFS.com/20201228/role/DisclosureRiskReturnDetailDataElementsMFSUSGovernmentCashReserveFund Risk/Return Detail Data- MFS?? U.S. Government Cash Reserve Fund 15 false true R58.htm 020056 - Document - Risk/Return Summary {Unlabeled} - MFS?? Value Fund Sheet http://www.MFS.com/20201228/role/DocumentRiskReturnSummaryUnlabeledMFSValueFund Risk/Return Summary- MFS?? Value Fund 16 false false R65.htm 020063 - Disclosure - Risk/Return Detail Data {Elements} - MFS?? Value Fund Sheet http://www.MFS.com/20201228/role/DisclosureRiskReturnDetailDataElementsMFSValueFund Risk/Return Detail Data- MFS?? Value Fund 17 false false R66.htm 040000 - Disclosure - Risk/Return Detail Data {Elements} Sheet http://xbrl.sec.gov/rr/role/RiskReturnDetailData Risk/Return Detail Data 18 false false All Reports Book All Reports tm2037454d1_485bpos.htm ck0000798244-20201228.xsd ck0000798244-20201228_cal.xml ck0000798244-20201228_def.xml ck0000798244-20201228_lab.xml ck0000798244-20201228_pre.xml tm2037454d1_ex99-a28.htm tm2037454d1_ex99-d12.htm tm2037454d1_ex99-h11.htm tm2037454d1_ex99-h14.htm tm2037454d1_ex99-i2.htm tm2037454d1_ex99-j1.htm tm2037454d1_ex99-j2.htm tm2037454d1_ex99-n2.htm g374542bi01i001.gif g374542bi01i002.jpg g374542bk01i001.gif g374542bk01i002.jpg g374542bm01i001.gif g374542bm01i002.jpg g374542bo01i001.gif g374542bo01i002.jpg g374542bq01i001.gif g374542bq01i002.gif g374542bs01i001.gif g374542bs01i002.jpg g374542bu01i001.gif g374542bu03i001.jpg g374542bw01i001.gif g374542bw01i002.jpg g374543bg01i001.gif BarChart1.png BarChart2.png BarChart3.png BarChart4.png BarChart5.png BarChart6.png BarChart7.png BarChart8.png http://xbrl.sec.gov/dei/2019-01-31 http://xbrl.sec.gov/rr/2018-01-31 true true